Electric circuit

The present invention relates to an electric circuit that connects a constant current power source and a detachable functional element driven by electric power from the constant current power source, and prevents the functional element from being destroyed according to the attachment / detachment of the functional element.

In a conventional typical light emitting device, in order to light an LED, a resistor and an LED are connected in series to a constant voltage power supply, and the current flowing through the LED is adjusted by the resistor, as shown in FIG. 12 (A). In this way, a current limiting circuit was connected in series between the constant voltage power supply 1 and the LED 2, and the current flowing through the LED was adjusted by the current limiting circuit. However, when the resistors and current limiting circuits are connected in series in this way, the resistors and current limiting circuits inserted during the normal driving of the LED become a load, causing energy loss.

In recent years, the brightness of LEDs has become higher, and unlike conventional display LEDs, it has become necessary to drive them with a large current. When driven by such a large current, if the configuration is the same as that of a conventional typical light emitting device, the energy loss due to the load due to the inserted resistance and the current limiting circuit increases. In order to reduce such energy loss and promote miniaturization, a constant current power source has been increasingly used instead of the constant voltage power source.

A conventional general power supply is provided with a capacitor between the reference potential end and the output end in order to supply a stable voltage or current and to reduce fluctuations due to noise or the like (for example). , See Patent Document 1). During operation of the constant current power supply, electric charges corresponding to the capacity of the capacitor and the output voltage of the constant current power supply are accumulated in this capacitor. Even after the operation is stopped, the electric charge is accumulated until the electric charge is completely discharged by the natural discharge.

In a conventional typical light emitting device that lights LED2 by the electric power from a general constant current power source 1, the constant current power source 1 and LED2 are connected by wiring as shown in FIG. 12 (B). .. In such a case, when the LED2 is mounted while the electric charge is accumulated in the capacitor C1, the LED2 is damaged or deteriorated. This is because only the current of a predetermined current value is supplied from the current limiting circuit, but the electric charge stored in the capacitor C1 is instantly discharged when the LED2 is mounted, so that the current is instantaneously extremely large (instantaneous). This is because it flows as an electric current).

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2004-119078</text></patcit>

<p> In order to prevent the LED from being destroyed or deteriorated, it is sufficient to wait for a predetermined time after stopping the operation of the constant current power supply. However, in the case of LEDs driven by a large current, the amount of charge stored in the capacitor C1 has doubled, and waiting for the completion of spontaneous discharge is no longer a realistic solution. In addition, in the light emitting device for notifying the occurrence of an emergency such as an emergency light, the emergency light can never be turned off for safety as long as the device that monitors the light emitting device is in operation. .. Therefore, it is necessary to avoid stopping those devices for the replacement of all or part of the LEDs that make up the emergency light, and a device that can replace the LEDs while the constant current power supply is operating is eagerly desired. Was there. In addition, when arranging a large number of LEDs with multiple colors to form a figure, pattern, or image, the LEDs should be operated while the constant current power supply is operating so that the work can be performed while visually checking the emission color and the arrangement location. A replaceable device was eagerly awaited.</p><p> In the above, the case where the capacitor is connected between the output end and the reference potential end has been described, but the same applies to all constant current power supplies having a capacitance between the output end and the reference potential end. .. Further, although the case of the light emitting device has been described above, the same applies to the general electric equipment provided with the detachable functional element driven by the constant current power source.</p><p> Therefore, in the electric circuit according to the present invention, it is possible to prevent the functional element from being destroyed or deteriorated due to the attachment / detachment of the functional element immediately after the power is cut off from the constant current power source or during the power supply, and the impedance of the functional element during normal driving. Suppress the increase.</p>

<p> In order to solve the above problems, the electric circuit according to the present invention has a constant current power supply including a capacitance between an output end and a reference potential end, and a predetermined function based on the power from the constant current power supply. A first circuit end that electrically connects to a detachable functional element that expresses the above, and is electrically connected to one of the output end and the reference potential end via the functional element. A second circuit end electrically connected to the other of the output end and the reference potential end, a switching element arranged between the first circuit end and the second circuit end, and control of the switching element. An element destruction prevention circuit including a switching control circuit for controlling voltage is provided, and a state in which the functional element is not mounted is defined as a disconnected state, and a state in which the functional element is mounted is defined as a connected state.<u style="single">The switching control circuit includes a resistance element and a capacitance element.</u> The element destruction prevention circuit changes the control voltage of the switching element based on the change in voltage between the first circuit end and the second circuit end according to the state transition from the connected state to the non-connected state. The impedance between the first circuit end and the second circuit end is self-consistently increased to the impedance at the time of non-connection, and the first state corresponding to the state transition from the non-connection state to the connection state. Based on the change in voltage between the 1st circuit end and the 2nd circuit end<u style="single">, The capacitance element is charged by the current passing through the resistance element, and the voltage between the terminals of the capacitance element causes the capacitance element to be charged.</u>It is characterized in that the control voltage of the switching element is changed to reduce the impedance between the first circuit end and the second circuit end to a connection impedance lower than the non-connection impedance in a self-aligned manner. .. Further, in order to solve the above problems, the electric circuit according to the present invention is determined based on a constant current power supply including a capacitance between the output end and the reference potential end and the power from the constant current power supply. A first circuit end that electrically connects to a detachable functional element that expresses the above-mentioned function, and is electrically connected to one of the output end and the reference potential end via the functional element. A second circuit end electrically connected to the other of the output end and the reference potential end, a switching element arranged between the first circuit end and the second circuit end, and the switching element. An element destruction prevention circuit including a switching control circuit for controlling the control voltage of the above is provided, and the state in which the functional element is not mounted is regarded as the disconnected state, and the state in which the functional element is mounted is defined as the connected state.<u style="single">The switching control circuit includes a resistance element and a capacitance element.</u> The element destruction prevention circuit sets the control voltage of the switching element based on the change in the current flowing between the first circuit end and the second circuit end according to the state transition from the connected state to the non-connected state. By changing the impedance, the impedance between the first circuit end and the second circuit end is self-consistently increased to the unconnected impedance, and the state transition from the non-connected state to the connected state is performed. Based on the change in current flowing between the end of the first circuit and the end of the second circuit<u style="single">, The capacitance element is charged by the current passing through the resistance element, and the voltage between the terminals of the capacitance element causes the capacitance element to be charged.</u>It is characterized in that the control voltage of the switching element is changed to reduce the impedance between the first circuit end and the second circuit end to a connection impedance lower than the non-connection impedance in a self-aligned manner. ..</p>

<p> In the electric circuit according to the present invention, in the discharge of the accumulated charge of the capacitive element, the impedance between the first circuit end and the second circuit end completely becomes the impedance at the time of connection immediately after the state transition to the connected state. Since it is started before the change is completed (in the case of impedance at the time of non-connection), it is possible to suppress a sudden change in the discharge current based on the discharge. As a result, it is possible to prevent the functional element from being damaged or deteriorated due to the attachment / detachment of the functional element immediately after the power supply from the general constant current power supply is cut off or during the power supply. Further, when the functional element is mounted and the functional element is driven in the normal state, the impedance between the first circuit end and the second circuit end is changed to low impedance (impedance at the time of connection). Since the electric power is supplied through the prevention circuit, the energy loss due to the load of the element destruction prevention circuit can be reduced.</p>

The best form of the electric device according to the present invention will be described. After explaining the conceptual configuration of the present invention, the specific configuration will be described with reference to the drawings.

The electric circuit according to the present invention comprises a constant current power supply including a capacitance between an output end and a reference potential end, and a detachable functional element that exhibits a predetermined function based on the power from the constant current power supply. An electric circuit that is electrically connected and includes a first circuit end connected to the output end of a constant current power supply and a second circuit end connected to a reference potential end of a constant current power supply via a functional element. Equipped with a destruction prevention circuit. The state in which the first circuit end and the output end of the constant current power supply are not electrically connected due to the disconnection and disconnection of the functional element is referred to as a "non-connected state", and the first circuit end and the output are described by mounting the functional element. The state in which the ends are electrically connected is referred to as a "connection state".

The "reference potential" is a common potential that serves as a voltage reference between the constant current power supply and the element destruction prevention circuit, and is usually a ground potential. Further, "connected to the reference potential end of the constant current power supply" is not limited to the case where the constant current power supply is specifically connected by wiring, and the constant current power supply and the element destruction prevention circuit may be individually grounded. Means.

The element destruction prevention circuit self-consistently increases the impedance between the first circuit end and the second circuit end to the impedance at the time of non-connection according to the state transition from the connected state to the non-connected state. Further, the element destruction prevention circuit self-aligns the impedance between the first circuit end and the second circuit end to be lower than the non-connection impedance at the time of connection according to the state transition from the non-connection state to the connection state. Reduce to. Here, "self-aligned" is determined according to a circuit state, for example, a voltage value at a predetermined location or a current value at a predetermined location, without any human operation other than mounting a functional element. Means. It should be noted that the discharge of the electric charge accumulated in the capacitance is immediately after the state transition to the connected state and before the impedance between the first circuit end and the second circuit end finishes changing to the impedance at the time of connection (substantially). (Impedance when not connected).

Examples of the element destruction prevention circuit include a circuit in which the internal resistance of the electric device when the functional element is mounted is self-aligned and larger than that in the normal driving state of the functional element, a circuit in which the discharge itself is moderated, and a circuit. A combination circuit thereof can be mentioned.

In the absence of the element destruction prevention circuit, at least a part of the accumulated charge is discharged instantly even when the constant current power supply is inactive, so the time change of the discharge current is a spire (peak) with an extremely narrow time width. ), And its maximum value (peak value) is a value that far exceeds the drive current value in the steady drive state. However, the amount of discharge (moving charge amount) in that case is generally a constant amount according to the amount of accumulated charge and the drive voltage of the functional element regardless of the presence or absence of the element destruction prevention circuit, and therefore the internal resistance of the electric device. The peak value of the discharge current can be reduced by increasing or gently discharging. As a result, it is possible to suppress the destruction or breakage of the functional element due to the flow of an excessive current. Further, when the constant current power supply is in the operating state, the discharge current is superimposed on the supply current from the power supply circuit excluding the element destruction prevention circuit and becomes a larger value. Therefore, the reduction rate of the discharge current in the element destruction prevention circuit is increased. It needs to be large.

The element destruction prevention circuit is located between the current inflow end connected to the functional element, the current outflow end connected to the reference potential end of the constant current power supply, and the current inflow end and the current outflow end. The present invention includes a switching element including a control end for changing a resistance, and a voltage-dependent switching control circuit for controlling the voltage at the control end based on a change in the voltage at the current inflow end of the switching element. The switching control circuit connects the resistance between the current inflow end and the current outflow end based on the change in the voltage of the current inflow end of the switching element in response to the state transition to the non-connection state. Is changed from the predetermined resistance value at the time of connection to a predetermined resistance value at the time of non-connection which is larger than the resistance value at the time of connection, and is based on the change of the voltage at the current inflow end of the switching element according to the state transition to the connection state. Therefore, it is preferable that the resistance between the current inflow end and the current outflow end is changed from the disconnection resistance value to the connection resistance value.

The "switching element" means an element capable of selectively expressing at least two different resistance values, and may be a binary selection element, a multi-value selection element, or a continuous element. It may be an element that takes a value that changes to. Examples of the switching element include an element such as a transistor whose resistance value can be controlled by an electric action, an element such as a photocoupler whose resistance value can be controlled by an optical action, and an element whose resistance value can be controlled by a magnetic action. The "current inflow end" is a terminal through which a current flows (a terminal through which electrons flow out), and in the case of a transistor, it means a drain end or a collector end. The "current outflow end" is a terminal through which a current flows out (a terminal through which electrons flow in), and in the case of a transistor, it means a source end or an emitter end. Further, the "control end" is a terminal to which a current signal or a voltage signal for changing the resistance value between the current inflow end and the current outflow end is input, and in the case of a transistor, the gate end or the base. Means the edge.

With this configuration, in order to change the impedance between the 1st circuit end and the 2nd circuit end by controlling the resistance value by the switching element, it is easy and surely between the 1st circuit end and the 2nd circuit end. Impedance can be changed. Further, since the resistance value is controlled based on the change in the voltage at the current inflow end of the switching element, the impedance between the first circuit end and the second circuit end can be controlled in a self-aligned manner easily and surely.

The element destruction prevention circuit is located between the current inflow end connected to the functional element, the current outflow end connected to the reference potential end of the constant current power supply, and the current inflow end and the current outflow end. A switching element having a control end for controlling a resistance value, and a current-dependent switching control circuit for controlling the voltage at the control end based on a change in the current flowing into the current inflow end of the switching element. The resistance between the current inflow end and the current outflow end is increased by the switching control circuit based on the change of the current flowing into the first circuit end in response to the state transition to the disconnected state. The change from the predetermined connection resistance value in the connected state to the predetermined non-connection resistance value larger than the connection resistance value, and the change of the current flowing into the first circuit end according to the state transition to the connection state. Based on this, it is preferable that the resistance between the current inflow end and the current outflow end is changed from the unconnected resistance value to the connected resistance value.

With this configuration, in order to change the impedance between the 1st circuit end and the 2nd circuit end by controlling the resistance value by the switching element, it is easy and surely between the 1st circuit end and the 2nd circuit end. Impedance can be changed. Further, since the resistance value is controlled based on the change of the current flowing into the first circuit end, the impedance between the first circuit end and the second circuit end can be controlled in a self-aligned manner easily and surely.

The element destruction prevention circuit changes the impedance between the first circuit end and the second circuit end to an impedance lower than the impedance at the time of connection according to the state transition to the connection state. It is preferable that the configuration further includes the configuration. Specifically, for example, the resistance between the current inflow end and the current outflow end of the switching element is changed to a resistance value lower than the connection resistance value according to the state transition to the connection state. Examples thereof include a configuration further including a resistance circuit.

With this configuration, it is possible to further suppress an increase in load caused by the element destruction prevention circuit during normal driving of the functional element. Further, it is possible to substantially prevent the increase in the load.

The element destruction prevention circuit further includes a high impedance promotion circuit that speeds up the change in impedance between the first circuit end and the second circuit end due to the state transition to the non-connected state. Is preferable. Specifically, for example, a configuration further including a high resistance promotion circuit for accelerating the change in resistance between the current inflow end and the current outflow end of the switching element due to the state transition to the non-connected state. Can be mentioned.

With this configuration, the impedance between the 1st circuit end and the 2nd circuit end (resistance between the current inflow end and the current outflow end) is increased at high speed (high) when shifting to the non-connected state. In order to be able to (resistive), specifically, the transition to the completely off state of the switching element can be performed at high speed, so even if the transition to the connected state and the transition to the disconnected state are repeated in a short period of time. Destruction and deterioration of functional elements can be suppressed. As a result, it is possible to suppress destruction and deterioration caused by chattering and unexpected repetition of attachment / detachment when attaching / detaching the functional element.

The element destruction prevention circuit is located between the current inflow end connected to the functional element, the current outflow end connected to the reference potential end of the constant current power supply, and the current inflow end and the current outflow end. It further includes a switching element having a control end for changing the resistance and an additional circuit end connected to the output end of the constant current power supply in the process of mounting the functional element, and responds to the state transition to the non-connected state. Based on the change in the voltage at the end of the additional circuit, the resistance between the current inflow end and the current outflow end is changed from the predetermined connection resistance value in the connection state to a predetermined connection resistance value larger than the connection resistance value. The resistance value is changed to a resistance value, and the resistance between the current inflow end and the current outflow end is changed from the unconnected resistance value based on the change in the voltage at the additional circuit end according to the state transition to the connection state. It is preferable that the configuration is such that the resistance value at the time of connection is changed.

With this configuration, it is possible to further suppress an increase in load caused by the element destruction prevention circuit during normal driving of the functional element. Further, it is possible to substantially prevent the increase in the load.

Here, a specific form of the element destruction prevention circuit according to the present invention will be described with reference to the drawings. In the following, various forms thereof will be described by taking the case where the functional element is an LED as an example.

[Embodiment 1] The element destruction prevention circuit of the first embodiment will be described. FIG. 1 is a circuit diagram showing an example of an element destruction prevention circuit according to the first embodiment. FIG. 1 shows the constant current power supply 1 and LED 2 together with the element destruction prevention circuit 10. In FIG. 1, the switch SW1 is not a switch element provided separately from the LED2, but is a virtual switch for representing the transition between the connected state and the non-connected state of the LED2. For example, a socket (not shown) that includes a first input / output terminal and a second input / output terminal that are electrically connected to the output end (upper wiring end) of the constant current power supply 1 and that fixes the LED 2 detachably. It is composed of LED2. By attaching LED2 to the socket, the first input / output terminal and the second input / output terminal are electrically connected, and by removing LED2 from the socket, the terminals are electrically connected. There are cases where it is cut off. Therefore, when the switch SW1 is in the ON state, it means that the LED2 is electrically connected to the element destruction prevention circuit 10, and when it is in the OFF state, the LED2 is electrically connected to the element destruction prevention circuit 10. It means a disconnected state that is not connected. The same applies to the switch SW1 in the following various embodiments.

Prior to the description of the element destruction prevention circuit 10, the constant current power supply 1 and the LED 2 will be described. As shown in FIG. 1, the constant current power supply 1 is connected in series with the DC power supply V as a power source circuit and the DC power supply V, and the current supplied from the DC power supply V is reduced to a predetermined maximum current value or less. It includes a current limiting circuit to limit, a DC power supply V connected in series, and an electrolytic capacitor C1 (a type of [capacitance]) connected in parallel to the current limiting circuit. The low potential side of the DC power supply V is grounded. When the constant current power supply 1 is on (power supply state), the electrolytic capacitor C1 has its capacity and the voltage value of the output voltage V0 (potential difference with respect to the ground potential) of the constant current power supply 1 (for example, 30 [V (). Charges ([accumulated charge]) corresponding to (volt)]) are accumulated. Further, even in the off state of the constant current power supply 1 (power supply stop state), although the accumulated charge is attenuated by the natural discharge, the charge is accumulated for a long time from the transition to the off state. LED2 emits light when a voltage equal to or higher than a predetermined drive threshold voltage value VF (for example, 20 [V]) is applied, and the emission brightness increases as the supplied current value increases. If a current exceeding the rated maximum current value (for example, 5 [A (ampere)]) is supplied, the LED2 itself may be destroyed and no light may be emitted, or a part of it may be damaged and normal light emission may not be possible. To do. The electromotive voltage of the DC power supply V is equal to or higher than the drive threshold voltage value VF, and the current value of the output current I0 from the current limiting circuit (for example, 1 [A]) is smaller than the rated maximum current value of LED2. The electric field capacitor C1 mitigates the influence of sudden fluctuations in the DC power supply V, the output voltage V0 of the current limiting circuit, the output current I0, etc. in the steady drive state of the LED2, and outputs from the constant current power supply 1. It suppresses that the voltage becomes less than or equal to the drive threshold voltage value VF of LED2 and that the output current I0 exceeds the rated maximum current value of LED2 and becomes large. In addition, it suppresses the destruction or damage of the DC power supply V and current limiting circuit due to the flyback current that accompanies the transition from the connected state to the disconnected state due to the disconnection and disconnection of LED2. Although FIG. 1 shows a case where the electric field capacitor C1 is provided between the output end and the reference potential end of the constant current power supply 1, a capacitive element such as the electric field capacitor C1 is actually connected. This may be the case when the DC power supply V or the current limiting circuit has an inherent capacitance. Further, although FIG. 1 shows a case where a DC power supply V is provided as an electromotive force circuit, it may be an electromotive force circuit that converts AC power supplied from the outside into DC power. It may be an electromotive force circuit that converts DC power supplied from the outside into a predetermined voltage or the like.

As shown in FIG. 1, the element destruction prevention circuit 10 is a type of the cathode end of LED 2 on the opposite side of the constant current power supply 1 and the ground potential end (lower wiring end; [reference potential end]) of the constant current power supply 1. ) Is composed only of the transient current suppression circuit 11. The transient current suppression circuit 11 is based on the voltage of the drain end (a type of [current inflow end] and [first circuit end]) of the LED2 and the field transistor Q1, and a sudden change in the transient current after the transition to the connected state. Suppress. Here, the "transient current after the transition to the connected state" means the current flowing through the LED 2 in the transitional period until the steady state is reached after the transition to the connected state due to the mounting of the LED 2. The transient current is caused by the current supplied from the DC power supply V via the current limiting circuit (hereinafter referred to as "basic current") and the discharge of the electrolytic capacitor C1 when the constant current power supply 1 is in the ON state. It is the total current with the current (discharge current), and is the same as the current caused by the discharge of the electrolytic capacitor C1 when the constant current power supply 1 is in the off state (power supply stop state). In the following, if it is possible to prevent the destruction or deterioration of LED2 due to the installation of LED2 in the on state of the constant current power supply 1, the destruction or deterioration of LED2 due to the installation of LED2 in the off state of the constant current power supply 1 is a DC power supply. Since it is not affected by the current supplied from V, it can be reliably prevented. Therefore, only the case where the LED 2 is mounted while the constant current power supply 1 is on will be described in detail.

The transient current suppression circuit 11 is a gate control circuit that suppresses the transient current and controls the voltage at the gate end (a type of [control end]) of the field effect transistor Q1 (a type of switching element). (A type of "voltage-dependent switching control circuit"). The drain end (a type of [current inflow end]) of the field effect transistor Q1 is connected to LED2, and the source end (a type of [current outflow end]) is connected to the ground potential end. The gate control circuit consists of a resistor R1 that connects the gate end of the field effect transistor Q1 and one end of LED2, a capacitor C2 that connects the gate end and the ground potential end, and a resistor R2 that connects the gate end and the ground potential end. And is included. The resistor R1 and the capacitor C2 mainly constitute a circuit unit that suppresses the transient current and controls the transition of the field effect transistor Q1 to the on state, and the resistor R2 mainly constitutes the off state of the field effect transistor Q1. It constitutes a circuit part which controls the transition of.

Here, the operation of the element destruction suppression circuit 10 (transient current suppression circuit 11) will be described. FIG. 2 is a timing chart that qualitatively shows an example of the operation of the element destruction suppression circuit 10. FIG. 2 (A) shows the time transition of the current flowing through the LED 2, and FIG. 2 (B) shows the time transition between the terminals of the capacitor C2. The time transition of the voltage is shown, and Fig. 2 (C) shows the time transition of the resistance between the source and drain of the field effect transistor Q1. Note that FIG. 2 shows only the operation when the state shifts from the non-connected state to the connected state according to the mounting of the LED 2. Further, in FIG. 2A, for reference, the time transition of the current flowing through the LED when the transient current suppression circuit 11 is not provided is shown by a alternate long and short dash line. These are the same in the timing chart referred to in other embodiments described later.

First, by disconnecting and disconnecting LED2, the constant current power supply 1 is in the on state as shown in FIG. 1, and by disconnecting and disconnecting LED2, it shifts to the disconnected state (SW1 is off) for a predetermined time. After the lapse of time, the voltage of the electrolytic capacitor C1 is the same as the voltage value of the output voltage V0 of the constant current power supply 1, and the voltage value of the voltage across the capacitor C2 VC2 is Vn [V] (Vn). = 0), the field effect transistor Q1 is in the off state, and the resistance value of the source-drain resistance RQ1 is Rn [Ω (ohm)]. On the other hand, the voltage of the electrolytic capacitor C1 is in the steady phase of the connection state, which is after a predetermined time has elapsed since the constant current power supply 1 is on and the connection state (SW1 is on) is changed by mounting the LED2. Is V0 [V], which is the same as the output voltage value of the constant current power supply 1, the voltage value of the voltage VC2 across the capacitor C2 is Vs [V], and the field effect transistor Q1 is on and its source and drain. The resistance value of the inter-resistance RQ1 is Rs [Ω].

When the installation of LED2 is started and the transition from the disconnected state to the connected state (time t0) occurs, the circuit becomes closed immediately after the connection transition, which corresponds to the case where the space between the source end and the drain end of the field effect transistor Q1 is open. , The supply of the transient current including the basic current caused by the DC power supply V and the discharge current caused by the electrolytic capacitor C1 is started.

Even if the supply of the transient current is started, the rapid increase of the transient current flowing through the LED 2 is suppressed by the resistor R1 and the capacitor C2 connected in series in the closed circuit immediately after the connection transition. Therefore, immediately after the transition to the connected state, the current value of the transient current ILED is a minute value In [A] as shown in FIG. 2 (A). When there is no transient current suppression circuit 11 and the cathode end of LED2 is connected to the ground potential end of the constant current power supply 1, as shown by the one-point chain line in FIG. 2 (A), the LED2 is constantly driven. An instantaneous current of a spire waveform having a maximum value Im [A] (for example, Im = 28) with a current value far exceeding the current value Is [A] (for example, Is = 1) of the output current I0 at the time flows.

As time elapses from the transition to the connected state, as shown in Fig. 2 (B), the capacitor C2 is charged by the transient current, and the voltage VC2 of the capacitor C2 changes from Vn [V] to Vs. It gradually increases to [V] (time ts). After that, the voltage VC2 of the capacitor C2 maintains Vs [V].

In addition, as the gate voltage of the field effect transistor Q1 (same as the voltage VC2 of the capacitor C2) increases in response to this charging, the resistance value between the source and drain increases as shown in FIG. 2 (C). It gradually decreases from Rn [Ω] to Rs [Ω] (time ts). After that, the resistance value between the source and drain maintains Rs [Ω]. The resistance value of the source-drain resistor RQ1 does not substantially start to decrease until the gate voltage of the field effect transistor Q1 exceeds a predetermined threshold voltage.

As shown in Fig. 2 (A), the current value of the transient current ILED is such that in the initial stage of the transition period, a current path is formed through the resistor R2 after the supply of the transient current ILED is started, and the current is formed. Since the diversion component of the transient current ILED flowing through the path increases with the increase of the voltage VC2 of the capacitor C2, it slightly increases from In [A]. In this initial stage, since the field effect transistor Q1 is maintained in the off state, the resistance value of the source-drain resistor RQ1 is higher than the combined resistance value of the resistors R1 and R2 connected in series. Due to its large size, it hardly functions as a current path for transient current ILEDs. However, after that, when the resistance value of the source-drain resistance RQ1 due to the increase of the voltage VC2 of the capacitor C2 becomes smaller than the combined resistance value of the resistance R1 and the resistance R2, the field effect transistor Q1 is used as the current path of the transient current ILED. The current path through the resistor R1 and the current path through the resistor R2 become dominant over the current path through the resistor R1 and R2, and as shown in Fig. 2 (A), in response to the sharp decrease in the resistance value of the source-drain resistor RQ1. It increases sharply to Is [A] (time ts). After that, a steady current whose current value is Is [A] is supplied to LED2.

In the steady phase of the connected state in which the steady current is supplied to LED2, the resistance value Rs [Ω] is substantially smaller than the combined resistance of the resistance R1 and the resistance R2 instead of the transient current suppression circuit 11. A closed circuit corresponding to the case where is provided between the LED 2 and the ground potential end of the constant current power supply 1 is formed.

On the other hand, when the disconnection / disconnection of LED2 is started and the connection state is changed to the non-connection state, the capacitor C2 starts discharging through the resistor R2. This discharge reduces the voltage VC2 of the capacitor C2 from Vs [V] to Vn (= 0) [V] and then maintains Vn [V]. In addition, the resistance value of the source-drain resistor RQ1 increases from Rs [Ω] to Rn [Ω] as the voltage value of the gate voltage of the field effect transistor Q1 decreases as the potential VC2 across the capacitor C2 decreases. After that, Rn [Ω] is maintained.

In the element destruction prevention circuit 10 (transient current suppression circuit 11) of this embodiment, a resistor connected in series as the main current path of the transient current at the initial stage of the transition period after the transition to the connection state by mounting the LED2. A current path is formed via R1 and capacitor C2, and the resistance value of the source-drain resistance RQ1 of the electric field effect transistor Q1 that becomes the main current path of the subsequent transient current gradually decreases. As a result, a sudden change in transient current can be suppressed, and it is possible to prevent an instantaneous current that exceeds the rated maximum current value of LED2 and the current value Is [A] in the stationary period in the connected state. As a result, it is possible to prevent the LED 2 from being damaged or deteriorated even if the LED 2 is attached or detached when the constant current power supply 1 is in the power supply state. In addition, in the steady-state period after the transition to the connection state by mounting the LED2, a current path is formed between the source and drain of the field-effect transistor Q1 in the on-state as the main current path of the steady-state current, which is usually present. It is possible to suppress an increase in load due to the element destruction prevention circuit 10 itself in driving LED2. As a result, it is possible to suppress an increase in power consumption and heat generation. The formation of the main path of the transient current and the formation of the main current path of the steady current are based on the circuit state of the element destruction prevention circuit 10 itself, specifically, depending on the voltage between the elements of the field effect transistors Q1 and LED2. Since it is automatically performed based on the control of the field effect transistor Q1, it is not necessary to perform artificial work other than the attachment / detachment work when replacing the LED2. Further, by using the capacitor C2 for suppressing a sudden change in the transient current to control the gate voltage of the field effect transistor Q1, the circuit configuration of the element destruction prevention circuit 10 can be simplified.

In the above, the case where the transient current suppression circuit 11 is composed of the field effect transistor Q1, the resistor R1, the resistor R2 and the capacitor C1 has been described, but the electric current in which the main current path of the steady current in the steady phase of the connected state is on. Even if the current path is via the effect transistor Q1 and the main current path of the transient current is a path other than the field effect transistor Q1 and at least the current path via the resistance element at least in the initial stage of the transitional period of the connected state. Good. Further, in the above, the capacitor C2 constitutes a part of a circuit for preventing a sudden change in the transient current and a part of a circuit for controlling the gate voltage of the field effect transistor Q1. Although the circuit configuration has been simplified by using it as an element, each circuit may include a capacitor individually.

[Embodiment 2] The element destruction prevention circuit according to the second embodiment has a configuration capable of reducing the load due to the element destruction prevention circuit itself in the stationary period of the connected state as compared with the element destruction prevention circuit 10 according to the first embodiment. FIG. 3 is a circuit diagram showing an example of the element destruction prevention circuit according to the second embodiment. The element destruction prevention circuit 20 of this embodiment has the same configuration as the element destruction prevention circuit 10 (see FIG. 1) in the first embodiment, except that the element destruction prevention circuit 20 includes the resistance-free circuit 22. In the following, the same components as those in the first embodiment will be designated by the same reference numerals, and detailed description thereof will be omitted.

The element destruction prevention circuit 20 is a non-resistance circuit that further increases the voltage value of the gate voltage of the field effect transistor Q1 in the steady connection state to lower the resistance value of the source-drain resistance to make it substantially non-resistive. 22 (a type of [low impedance promotion circuit]: a type of "voltage-dependent switching control circuit") is further included. In this embodiment, the transition control of the field effect transistor Q1 to the on state is performed by the use of both the circuit unit including the resistor R1 and the capacitor C2 and the non-resistance circuit 22.

The non-resistance circuit 22 includes a circuit unit including a Zener diode ZD1, a resistor R3, and a resistor R4 arranged in series so as to connect the output end and the ground potential end of the constant current power supply 1, and the output end and the ground potential end. Resistor R5, resistor R6 and transistor Q2, resistor R5 and resistor arranged in series to connect with<u style="single">R</u>Zener diode ZD2, resistor that connects the element with 6 and the ground potential end<u style="single">R</u>It is composed of a circuit unit including a diode D1 that connects the elements of 6 and the transistor Q2 and the gate end of the field effect transistor Q1. The emitter end of the transistor Q2 is connected to the resistor R2, and the base end is connected between the elements of the resistor R3 and the resistor R4. The circuit unit including the Zener diode ZD1, the resistor R3 and the resistor R4 mainly controls the state transition between the on state and the off state of the transistor Q2 according to the change of the output voltage V0. The other circuit unit mainly constitutes a circuit unit that controls the state transition of the field effect transistor Q1 from the on state according to the transition of the transistor Q2 to the off state.

In the non-connected steady state shown in FIG. 3, the voltage across the electrolytic capacitor C1 is the same as the voltage value of the output voltage V0 of the constant current power supply 1, and the voltage value of the terminal voltage VC2 of the capacitor C2 is Vn [ V] (Vn = 0), the field effect transistor Q1 is in the off state, and the resistance value of the source-drain resistance RQ1 is Rn [Ω (ohm)]. In addition, the Zener diode ZD1 maintains the breakthrough voltage, and the transistor Q2 is the voltage obtained by subtracting the breakthrough voltage of the Zener diode ZD1 from the output voltage V0, which is divided by the resistors R3 and R4 into resistors R3 and R4. The ON state is maintained by the voltage value between the elements.

On the other hand, both ends of the electrolytic capacitor C1 are in the steady phase of the connection state, which is after a predetermined time has elapsed since the constant current power supply 1 is on and the connection state (SW1 is on) is changed by mounting the LED2. The voltage is V0 [V], which is the same as the output voltage value of the constant current power supply 1, the voltage value of the voltage VC2 across the capacitor C2 is Vs [V], and the field effect transistor Q1 is in the ON state and its source. The effective resistance value of the inter-drain resistance is Rs'[Ω (ohm)]. Further, the current through the Zener diode ZD1, the current through the transistor Q2, and the current through the diode D1 are substantially cut off. In addition, various circuit elements are selected so as to realize the operation in the stationary period of such a non-connected state or a connected state.

Here, FIG. 4 is a timing chart that qualitatively shows an example of the operation of the element destruction prevention circuit 20, FIG. 4 (A) shows the time transition of the current flowing through the LED, and FIG. 4 (B) shows the capacitor C2. The time transition of the voltage between terminals is shown, and Fig. 4 (C) shows the time transition of the resistance between the source and drain of the field effect transistor.

When the LED2 is started to be mounted and the state is changed from the disconnected state to the connected state (time t0), the transient current ILED is started to be supplied, but the transient current flowing through the LED2 is based on the same operating principle as in the first embodiment. The rapid increase in ILED will be suppressed. As time elapses from the transition to the connected state, as shown in Fig. 4 (B), the transient current ILED charges the capacitor C2, and the voltage VC2 across the capacitor C2 becomes Vn [V]. Gradually increases from to Vs [V] (time ts). Further, as shown in FIG. 4 (C), the resistance between the source and drain is increased by increasing the voltage value of the gate voltage of the field effect transistor Q1 (same as the voltage across the capacitor C2 VC2) in response to this charging. The resistance value of RQ1 decreases from Rn [Ω] to Rs [Ω] (time ts). The transient phenomenon up to this point is qualitatively the same as in the case of the first embodiment.

As the resistance value of the source-drain resistor RQ1 decreases, the external combined resistance of the constant current power supply 1 decreases, so that the voltage value of the output voltage V0 decreases. At this time, the voltage between the source and drain of the field-effect transistor Q1 decreases until it becomes the same as the voltage between the source and gate where the field-effect transistor Q1 can hold the ON state. As the voltage value of the output voltage V0 decreases, the voltage value becomes smaller than the breakthrough voltage value of the Zener diode ZD1, and the current from the output end to the Zener diode ZD1 is cut off (time ts). Due to this interruption, the voltage between the elements of the resistor R3 and the resistor R4 becomes substantially the ground potential, and the transistor Q2 shifts to the off state. Due to this transition, as shown in FIG. 4 (B), the capacitor C2 is further charged by the current supplied through the resistor R5, the resistor R6 and the diode D1, and the voltage VC2 across the capacitor C2 becomes Vs'[. It further increases to V] (time ts'). After that, the voltage VC2 of the capacitor C2 is maintained at Vs'[V]. Further, by this charging, the resistance value of the source-drain resistance RQ1 of the field effect transistor Q1 decreases to Rs'[Ω] (Rs0) (time ts'). After that, the resistance RQ1 between the source and drain is maintained at Rs'[Ω]. The change in the current value of the transient current ILED is qualitatively the same as in the case of the first embodiment.

The element destruction prevention circuit 20 according to the present embodiment can further reduce the resistance value of the source-drain resistance RQ1 of the field effect transistor Q1 as compared with the case of the element destruction prevention circuit 10 of the first embodiment. Therefore, the increase in load caused by the element destruction prevention circuit 20 in the normal driving of the LED 2 can be suppressed more satisfactorily. In addition, since the resistance value of the source-drain resistance RQ1 of the field-effect transistor Q1 can be made substantially 0 [Ω], compared with the conventional configuration without the element destruction prevention circuit 20 (see FIG. 12 (B)). Therefore, the increase in load caused by the element destruction prevention circuit 20 can be suppressed extremely well.

In the above, the case where the gate voltage of the field effect transistor Q1 in the steady state in the connected state is controlled to a higher voltage value than the case where the non-resistance circuit 22 is not provided by the non-resistance circuit 22 shown in FIG. 3 will be described. However, any configuration may be used as long as the gate voltage value can be controlled to a high voltage value.

[Embodiment 3] In the element destruction prevention circuit 40 according to the third embodiment, when the LED (functional element) is attached or detached, a plurality of transitions from a connected state to a disconnected state and vice versa are performed at minute time intervals. Even if it occurs repeatedly, it is possible to prevent the functional element from being destroyed or deteriorated when it is attached or detached. FIG. 5 is a circuit diagram showing an example of the element destruction prevention circuit according to the third embodiment. The element destruction prevention circuit 40 of this embodiment shown in FIG. 5 includes a high resistance promotion circuit 43 (a kind of [high impedance promotion circuit]: a kind of a voltage-dependent switching control circuit). Except for this, the configuration is the same as that of the element destruction prevention circuit 20 (see FIG. 3) in the second embodiment. In the following, the same components as those in the second embodiment will be designated by the same reference numerals, and detailed description thereof will be omitted.

The high resistance promotion circuit 43 is mainly a circuit for forcibly discharging the capacitor C2 in the transient current suppression circuit 11. In this embodiment, the transition control of the field effect transistor Q1 to the off state is performed by using both the circuit unit including the resistor R2 and the high resistance promotion circuit 43. Specifically, the high resistance promotion circuit 43 is faster than discharging the capacitor C2 by the resistor R2 in the transient current suppression circuit 11 based on the voltage at the circuit end of the transient current suppression circuit 11 connected to the LED 2. It is a circuit that causes the discharge.

A circuit unit consisting of resistors R10 and R8 arranged in series so as to connect the circuit end of the transient current suppression circuit 11 connected to LED 2 and the ground potential end of the constant current power supply 1, and the non-resistance circuit 22. A circuit unit consisting of transistors Q3 and R7, which are arranged in series so as to connect the elements of resistor R5 and resistor R6 and the ground potential end, and are controlled according to the voltage between the elements of resistor R8 and resistor R10. And the circuit part consisting of the capacitor C3 and the resistor R9 arranged in series so as to connect the elements of the resistor R7 and the transistor Q3 and the ground potential end, and the cathode end (resistor) of the diode D1 of the non-resistance circuit 22. It is composed of a circuit unit consisting of a transistor Q4, which connects the ground potential end (between the elements of R1 and the resistor R2) and the ground potential end, and is controlled according to the voltage between the elements of the capacitor C3 and the resistor R9. The collector end of the transistor Q3 is connected to the resistor R7, the emitter end is connected to the ground potential end of the constant current power supply 1, and the base end is connected between the elements of the resistor R10 and the resistor R8. The collector end of the transistor Q4 is connected between the element of the diode D1 and the capacitor C2 in the transient current suppression circuit 11.

In the stationary period of the disconnected state shown in FIG. 5, the transistor Q3 is in the off state, and the transistor Q4 is also in the off state because the transistor Q3 is in the off state. Other circuit states are the same as in the second embodiment. On the other hand, in the steady phase of the connected state, the transistor Q3 is in the on state, and the transistor Q4 is also in the off state. Further, the voltage value of the output voltage V0 of the constant current power supply 1 in the non-connected state is larger than that in the connected state.

When the state is changed from the connected state to the disconnected state, the current through the resistor R1 and the resistor R10 is cut off. By interrupting the current through the resistor R1, the capacitor C2 starts discharging through the resistor R2. The discharge proceeds slowly through the resistor R2. On the other hand, by cutting off the current through the resistor R10, the base voltage of the transistor Q3 becomes substantially the ground potential, and the transistor Q3 shifts to the off state. When the transistor Q3 shifts to the off state, the transistor Q4 shifts to the on state, and the discharge of the capacitor C2 is started through the transistor Q4 (between the collector end and the emitter end). Since the collector-emitter resistor RQ1 of the transistor Q4 is much smaller than the resistor R2, the capacitor C2 can be discharged at high speed. However, due to the presence of the capacitor C3, the ON state of the transistor Q4 is temporary, and once it shifts to the ON state, it automatically shifts to the OFF state again. More specifically, since the DC component is cut off by the capacitor C3, the change in the output voltage V0 depending on the presence or absence of LED2 flows from the capacitor C3 to the base end of the transistor Q4 through the resistors R5 and R7, and the transistor Q4 is turned on. Let me. When the change in the output voltage V0 disappears, the currents from the resistors R5, R7 and the capacitor C3 disappear, so the transistor Q4 shifts to the off state. As a result, the transistor Q4 is turned on only during the change of the output voltage V0 at the moment when the state is changed from the connected state to the disconnected state, and when the output voltage V0 is stable even in the disconnected state or in the connected state, It remains off.

On the contrary, when the state is changed from the non-connected state to the connected state, the output voltage V0 is lowered and the transient current supply is started through the resistors R1 and R10. When the shunt current of the transient current flowing through the resistor R10 increases, the base voltage of the transistor Q3 rises, and when the current value of the shunt current of the transient current exceeds a predetermined current value, the transistor Q3 shifts to the on state. The capacitor C3 is substantially completely discharged in response to the transition of the transistor Q3 to the on state, and the base voltage of the transistor Q4 becomes substantially the ground potential with this discharge. This ensures that the transistor Q4 shifts to the off state. As a result, the operation after the transition to the connected state is executed as in the second embodiment.

Here, a case will be described in which the connection state is once changed when the LED2 is attached, the connection state is changed to the non-connection state, and then the connection state is changed again within a short period of time thereafter. When the high resistance promotion circuit 43 is not provided, the field-effect transistor Q1 shifts to the on state due to the transition to the connected state, and then shifts to the non-connected state, but the discharge of the capacitor C2 turns off the field-effect transistor Q1. If sufficient time is not secured to shift to the connection state, the LED2 will be connected with the field effect transistor Q1 turned on when the connection state is changed again, and when the connection state is changed, the LED2 will be connected. It is also possible that the steep increase in transient current cannot be sufficiently suppressed. However, in this embodiment, the capacitor C2 can be discharged at high speed when the state shifts to the non-connected state, that is, the transition to the completely off state of the field effect transistor Q1 can be performed at high speed, as described above. Even under the circumstances, the destruction and deterioration of LED2 can be suppressed.

The element destruction prevention circuit 40 according to the present embodiment can suppress the destruction and deterioration of the LED 2 due to repeated chattering and attachment / detachment during attachment / detachment of the LED, as compared with the case of the element destruction prevention circuit 20 of the second embodiment.

In the above, the case where the discharge of the capacitor C2 is performed by using the transient current suppression circuit 11 and the high resistance promotion circuit 43 in combination has been described, but the configuration is such that the discharge of the capacitor C2 is controlled only by the high resistance promotion circuit 43. You can also do it. In this case, the resistor R2 in the transient current suppression circuit 11 may not be present. Further, unlike the element destruction prevention circuit 50 shown in FIG. 6, in order to control the field effect transistor Q1 with high accuracy without providing the resistor R2, the diode D2 is located between the end of the first circuit and the resistor R1. Or a correction resistor R11 may be provided between the end of the first circuit and the drain end of the field effect transistor Q1.

In the above, the case where the high resistance promotion circuit 43 speeds up the discharge of the capacitor C2 at the time of transition from the connected state to the non-connected state has been described, but the high resistance promotion circuit according to the present invention is a switching element. Any configuration may be used as long as it can speed up the transition of the (field effect transistor Q1) from the on state to the off state.

[Embodiment 4] The element destruction prevention circuit according to the fourth embodiment has a configuration in which the switching element (field effect transistor Q1) is controlled based on the voltage as in the cases of the above-described first to third embodiments. FIG. 7 is a circuit diagram showing an example of the element destruction prevention circuit according to the fourth embodiment.

In the element destruction prevention circuit 60 shown in FIG. 7, when the connection state is entered, a transient current first flows through the resistor R12. The current flowing through the resistor R12 is a minute value, which suppresses a sudden change in the transient current. In addition, the transistor Q4 shifts to the ON state according to the change in the voltage at the cathode end of LED2. When the transistor Q4 shifts to the on state, the voltage between the resistor R14 and the collector end of the transistor Q4 drops, the base voltage of the transistor Q5 becomes substantially the ground potential, and the transistor Q5 shifts to the off state. As a result, the voltage between the elements of the resistor R15 and the resistor R16 in the circuit composed of the resistor R15, the resistor R16 and the capacitor C4 gradually increases. In response to this, the gate voltage of the field-effect transistor Q1 increases, and when it exceeds a predetermined value, the field-effect transistor Q1 shifts to the on state. After that, it becomes a steady period of the connected state.

On the contrary, when the state shifts to the non-connected state, the current flowing through the resistor R13 and the resistor R12 is cut off, and the base voltage of the transistor Q4 becomes substantially the ground potential. As a result, the transistor Q4 shifts to the off state. Further, the transistor Q5 shifts to the on state according to the off shift of the transistor Q4, and then the stationary period of the disconnected state is entered.

Even with the above configuration, substantially the same effect as that of the above-described first to third embodiments can be obtained.

[Embodiment 5] The element destruction prevention circuit according to the fifth embodiment has a configuration in which the switching element is controlled based on the current, unlike the cases of the above-described first to fourth embodiments. FIG. 8 is a circuit diagram showing an example of the element destruction prevention circuit according to the fifth embodiment. As shown in FIG. 8, the element destruction prevention circuit 70 of this embodiment is composed of a field effect transistor Q1 ([switching element]) and an element other than the field effect transistor Q1 and the gate voltage of the field effect transistor Q1. It is composed of a gate control circuit (a type of [current-dependent gate control circuit]) that controls the above. In the element destruction prevention circuit 70, the transient current suppression circuit 71 mainly suppresses the transient current and turns on the field effect transistor Q1 in the same manner as the transient current suppression circuit 11 (see FIG. 1) described above. It is a circuit that performs basic control of the transition to the off state and the transition to the off state. Further, the high resistance promotion circuit 73 (a type of [high impedance promotion circuit]) shifts the state of the field effect transistor Q1 to the off state in the same manner as the high resistance promotion circuit 43 (see FIG. 5) described above. It is a circuit that speeds up.

In the unconnected steady state shown in FIG. 8, the transistor Q7 is in the off state, and the voltage divided by the resistors R21 and R19 of the output voltage V0 is applied to the base end of the transistor Q6. Q6 is in the on state, and the transistor Q1 is in the off state because the transistor Q6 is in the on state.

When the transition from the disconnected state to the connected state (t0) occurs, as shown in FIG. 9D, a transient current starts to flow in R18 and R20 because the transistor Q1 is in the off state. Since the transient current flows out through the resistor R18 and the resistor R20, the sharp increase in the transient current can be reduced. As the transient current increases, the voltage drop in the resistor R18 increases, and the base voltage of the transistor Q7 increases accordingly. When the base voltage increases and exceeds a predetermined voltage value, the transistor Q7 shifts to the on state. As the transistor Q7 shifts to the on state, the voltage value of the base voltage of the transistor Q6 (same as the voltage VR19 of the resistor R19) of the transistor Q6 is substantially grounded from V1 [V] as shown in FIG. 9 (A). The potential (V0 [V]) is reached, and the transistor Q6 shifts to the off state. The transition of the transistor Q6 to the off state initiates charging of the capacitor C2 through the resistor R1 and increases the voltage VC2 across the capacitor C2, as shown in FIG. 9C. When the transistor Q6 is in the ON state, the current flowing through the resistor R1 substantially flows only through the transistor Q6. As shown in Fig. 9 (D), when the gate voltage of the field-effect transistor Q1 (same as the voltage across the capacitor C2 VC2) increases and the gate voltage exceeds a predetermined voltage, the field-effect transistor Q1 turns on. After shifting to the state and shifting to the ON state of the field-effect transistor Q1, the resistance value of the source-drain resistance RQ1 of the field-effect transistor Q1 decreases to Rs'[Ω] as the gate voltage increases.

In the element destruction prevention circuit 70 of this embodiment, a current path via the resistor R18 and the resistor 20 is formed as the main current path of the transient current at the initial stage of the transition period after the transition to the connected state by mounting the LED2. By gradually reducing the resistance value of the source-drain resistance RQ1 of the electric field effect transistor Q1 that becomes the main current path of the transient current after that, a steep change in the transient current can be suppressed. It is possible to prevent the flow of an instantaneous current that exceeds the rated maximum current value of LED2, which is substantially the current value Is [A] in the steady phase in the connected state. As a result, it is possible to prevent the LED 2 from being damaged or deteriorated even if the LED 2 is attached or detached when the constant current power supply 1 is in the power supply state. In addition, in the steady-state period after the transition to the connection state by mounting the LED2, a current path is formed between the source and drain of the field-effect transistor Q1 in the on-state as the main current path of the steady-state current, which is usually present. It is possible to suppress an increase in load due to the element destruction prevention circuit 70 when driving LED2. As a result, it is possible to suppress an increase in power consumption and heat generation. The formation of the main path of the transient current and the formation of the main current path of the steady current are based on the circuit state of the element destruction prevention circuit 70, specifically, for the control of the field effect transistor Q1 according to the output current from the LED2. Since it is automatically performed based on the above, there is no need to perform artificial work other than the attachment / detachment work when replacing the LED2.

In the above, the case where the transient current suppression circuit is composed of the field effect transistor Q1, the resistor R1, the resistor R2 and the capacitor C2 has been described, but the electric current effect in which the main current path of the steady current in the steady phase of the connected state is on. The current path may be a path via the field effect transistor Q1, and the main current path of the transient current may be a path other than the field effect transistor Q1 and at least a current path via a resistance element at least in the initial stage of the transitional period of the connected state. .. Further, in the above, the capacitor C2 constitutes a part of a circuit for preventing a sudden change in the transient current and a part of a circuit for controlling the gate voltage of the field effect transistor Q1. Although the circuit configuration has been simplified by using it as an element, each circuit may include a capacitor individually.

[Embodiment 6] The element destruction prevention circuit according to the sixth embodiment has a configuration in which a change in a mechanical connection state is used to suppress a transient current. FIG. 10 is a circuit diagram showing an example of the element destruction prevention circuit according to the sixth embodiment. The element destruction prevention circuit 80 of this embodiment is composed of only the transient current suppression circuit 81. As shown in FIG. 10, the transient current suppression circuit 81 is composed of a field effect transistor Q1 ([switching element]) and an element other than the field effect transistor Q1 and controls the gate voltage of the field effect transistor Q1. It is composed of a control circuit (a type of [voltage-dependent gate control circuit]). In the element destruction prevention circuit 80, the transient current suppression circuit 81 mainly suppresses the transient current and turns on the field effect transistor Q1 in the same manner as the transient current suppression circuit 11 (see FIG. 1) described above. It is a circuit that controls the transition to the off state and the transition to the off state. The resistor R1 that constitutes the current supply path to the capacitor C2 that substantially controls the gate voltage of the field effect transistor Q1 of the transient current suppression circuit 11 (see FIG. 1) is a separate contact P4. ..

When the mounting of LED2 is started, the contact P2 and the contact P4 first come into contact (t0). After that, contact P1 and contact P3 come into contact (t0'), and the mounting of LED2 is completed. When the contact P2 and the contact P4 come into contact with each other, a transient current flows through the resistor R1 and the capacitor C2, and charging of the capacitor C2 is started as shown in FIG. 11 (B). Since the transient current flows out through the resistor R1 and the capacitor C2, the sharp increase in the transient current can be reduced. After that, the state shifts from the non-connected state to the connected state by the contact between the contact P1 and the contact P3. In this state transition, since the closed circuit through which the transient current flows has already been formed, there is almost no influence of the instantaneous current. Subsequent operations are qualitatively the same as the transient phenomenon in the first embodiment as shown in FIGS. 11 (A) to 11 (C). Since one end of the resistor R1 of the element destruction prevention circuit 80 (the side opposite to the side connected to the gate end of the field effect transistor Q1) is connected to the anode end of the LED2, one end of the resistor R1 is the cathode of the LED. Compared to the element destruction prevention circuit 10 (see FIG. 1) connected to the end, the gate voltage of the field effect transistor Q1 can be made higher, and the source-drain resistance RQ1 can be made lower.

In the above, the case where the contact P1 and the contact P3 come into contact with each other after the contact P2 and the contact P4 come into contact with each other has been described. However, the contact P1 and the contact P3 are brought into contact with each other first, and then the contact P2 and the contact P4 are brought into contact with each other. It may be configured to be in contact with. Even in this case, the same control can be performed qualitatively as in the above case, and substantially the same effect can be obtained. Further, the contact between the contact P2 and the contact P4 may be performed substantially at the same time as the contact between the contact P1 and the contact P3. Even in this case, the same control can be performed qualitatively as in the above case, and substantially the same effect can be obtained.

In the above-described first to sixth embodiments, the case where the functional element is an LED has been described, but other light emitting elements may be used. Further, the functional element is not limited to the light emitting element, and may be an electric element that exhibits various functions other than light emission.

Further, in the above-described first to sixth embodiments, the case where the element destruction prevention circuit is arranged on the secondary side (LED cathode side) of the functional element has been described, but the primary side of the functional element (LED anode) has been described. It may be configured to be arranged on the side).

In the above, the element destruction prevention circuit has been described, but in the present invention, various electric devices incorporating the element destruction prevention circuit may be used. Specifically, for example, an adapter that includes an element destruction prevention circuit and is connected between a general constant current power source and a general electric device to make the functional element included in the electric device detachable, or element destruction. A power supply device that integrates a prevention circuit and a constant current power supply, an electric device that integrates an element destruction prevention circuit and a functional element, and an electric device that integrates an element destruction prevention circuit and a constant current power supply and a functional element. Can be mentioned. The effect of the present invention is enhanced when the functional element is a large current type functional element driven by a large current. Therefore, as the electric device, it is preferable to use LED lighting, LED light, LED signboard, and LED indicator light equipped with a large current type LED.

The present invention relates to an adapter for connecting a constant current power source and an electric device having a functional element, a constant current power supply device, an electric device having a functional element such as a light emitting element, for example, a lighting device (illumination) that illuminates a wide area or a narrow range. , Light), and can be used for light emitting devices such as display devices (signatures, indicator lights, image display devices) that display characters, figures, patterns, images, and videos.

<figref num="1">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 1.</figref><figref num="2">A timing chart qualitatively showing an example of the operation of the element destruction prevention circuit according to the first embodiment.</figref><figref num="3">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 2.</figref><figref num="4">A timing chart qualitatively showing an example of the operation of the element destruction prevention circuit according to the second embodiment.</figref><figref num="5">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 3.</figref><figref num="6">The circuit diagram which shows the modification of the element destruction prevention circuit which concerns on Embodiment 3.</figref><figref num="7">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 4.</figref><figref num="8">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 5.</figref><figref num="9">A timing chart qualitatively showing an example of the operation of the element destruction prevention circuit according to the fifth embodiment.</figref><figref num="10">The circuit diagram which shows an example of the element destruction prevention circuit which concerns on Embodiment 6.</figref><figref num="11">A timing chart qualitatively showing an example of the operation of the element destruction prevention circuit according to the sixth embodiment.</figref><figref num="12">(A) represents the electrical configuration of a conventional typical LED device using a constant voltage power supply, and (B) represents the electrical configuration of a conventional typical LED device using a constant current power supply. Figure.</figref>

Code description

1: Constant current power supply 2: LED (functional element) 10,20,40,50,60,70,80: Element destruction prevention circuit 11,31,71,81: Transient current suppression circuit 22: Non-resistance circuit (low) Impedance promotion circuit) 43,73: High resistance promotion circuit (high impedance promotion circuit) Q1: Field effect transistor (switching element)