Resonance-type switching power supply device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention rectifies a switching means for switching a DC input, a converter transformer to which a switching output is supplied by the switching circuit, a resonance means using the coil of the converter transformer as a resonance element, and an output of the converter transformer. The present invention relates to a resonance type switching power supply device including a rectifying means for supplying a load and a switching control means for controlling a switching frequency of the switching circuit according to a rectified output by the rectifying means.

【0002】

[Problems to be solved by conventional techniques and inventions]

Conventionally, a switching power supply device in which a direct current obtained by rectifying and smoothing commercial alternating current is switched at a high frequency of, for example, about 100 kHz and converted into a desired voltage by a transformer with high efficiency has been widely used. There is.

【0003】

The output voltage control method in the switching power supply device includes a pulse width modulation (PWM) control method that controls the duty ratio of the switching pulse according to a change in the output voltage, and controls the frequency and phase of the switching pulse. A frequency control method such as resonance, a phase control method, or the like is adopted.

【0004】

FIG. 8 shows the basic circuit configuration of a conventionally known current resonance type switching power supply 200.

【0005】

The current resonance type switching power supply 200 shown in FIG. 8 has an AC rectifying unit 3 connected to a commercial power supply 1 via a noise filter 2, a smoothing capacitor 4 for smoothing the rectified output by the AC rectifying unit 3, and this smoothing capacitor. A current resonance circuit 6 having a switching circuit 5 or the like for switching the DC output obtained by being smoothed by 4 and connecting the primary coil 10A of the converter transformer 10 and the resonance capacitor 6C in series connects the switching circuit 5. It is connected to the AC rectifier unit 3 via the above. A rectifying / smoothing circuit 20 including diodes 21A and 21B, capacitors 22A and 22B, and a choke coil 23 is connected to the secondary coil 10B of the converter transformer 10. A switching control circuit 25 that controls the switching operation of the switching circuit is connected to the rectifying / smoothing circuit 20 via an error detection circuit 24, and output terminals 26A and 26B are connected to the rectifying / smoothing circuit 20.

【0006】

In the current resonance type switching power supply 200 having such a configuration, the voltage on the secondary side output from the rectifying / smoothing circuit 20 via the output terminals 26A and 26B is referred to by the voltage comparator 24A in the error detection circuit 24. The error voltage obtained by comparing with the voltage Vref is fed back to the switching control circuit 24 via the photocoupler 24B, and the frequency at which the switching elements 5A and 5B are alternately switched is changed to change the input and load. I try to take out a stable voltage against fluctuations.

【0007】

In this current resonance type switching power supply device 200, the loss is reduced by the resonance circuit formed by the leakage inductance le of the converter transformer 10 and the capacitance of the resonance capacitor 6C.

【0008】

In the conventional current resonance type switching power supply 200, the leakage inductance le of the converter transformer 10 and the capacitance of the resonance capacitor 6C are fixed values, and the switches of the switching elements 5A and 5B in the switching circuit 5 near this self-resonance frequency fr. The gloss is minimized, the maximum output power is obtained, and the loss ratio is the minimum due to the operating characteristics. The operation at this time is as shown in FIG. 9, and when the input voltage is the lowest and the load current satisfies the maximum condition, the switch gloss is minimized and the conversion efficiency is maximized.

【0009】

When the input voltage rises or the load becomes lighter, the switching frequency is raised to control the output voltage to be constant. The operation at this time is as shown in Fig. 10, and IQ₁Since the switching element 5A forcibly turns off the current that is about to flow due to the self-resonance indicated by, the switch gloss increases by turning off when the current value is large.

【0010】

[Problems to be Solved by the Invention]

However, in reality, the input voltage also varies from 100 to 240V in each region, and the load current also changes greatly depending on the operation of the built-in equipment. Further, normally, the higher the input voltage and the lighter the load, the higher the switching frequency, so that the power converted to the secondary side is saved and the output is stabilized. Therefore, the conventional current resonance type switching power supply device 200 does not operate in a region where the loss ratio is low in a region normally used.

【0011】

Therefore, an object of the present invention is to always obtain high conversion efficiency in view of the problems in the conventional current resonance type switching power supply device as described above.

【0012】

[Means for solving problems]

In the present invention, by changing the leakage inductance of the converter transformer in response to changes in the input voltage and load, the optimum resonance condition is always created and the switching loss is constantly reduced.

【0013】

That is, the present invention rectifies the switching means for switching the DC input, the converter transformer to which the switching output by the switching circuit is supplied, the resonance means using the coil of the converter transformer as a resonance element, and the output of the converter transformer. A resonance type switching power supply device including a rectifying means for supplying the load and a switching control means for controlling the switching frequency of the switching circuit according to the rectified output by the rectifying means, wherein the converter transformer has a leakage inductance. The converter transformer is provided with a variable converter transformer, and is based on a detecting means for detecting an input voltage input to the switching means and an output current supplied to a load from the rectifying means, and a detection output by the detecting means. It is characterized by providing a control means for variably controlling the leakage inductance.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

【0015】

The resonant switching power supply device according to the present invention is configured as shown in FIG. 1, for example.

【0016】

The current resonance type switching power supply device 100 shown in FIG. 1 is an application of the present invention to the current resonance type switching power supply device 200 shown in FIG. 8, and instead of the converter transformer 10 having a fixed leakage inductance, the leakage A converter transformer 50 having a variable inductance is provided, and a control circuit 60 for controlling the leakage inductance of the converter transformer 50 is provided.

【0017】

In the current resonance type switching power supply device 100, the same components as those of the current resonance type switching power supply device 200 shown in FIG. 8 are designated by the same reference numerals in FIG. 1 for details. The explanation is omitted.

【0018】

In the converter transformer 50 in which the leakage inductance can be changed, for example, as shown in (A) and (B) of FIG. 2, the cores having four magnetic legs each made of a ferrite material are attached to each other. It has a magnetic core 51 that is butted against each other, and is wound around two common primary coils 50A and 50B so as to straddle the magnetic legs, and is controlled so as to be orthogonal to the above primary coil 50A and secondary coil 50B. The coil 50C is wound around two coils so as to straddle the magnetic legs.

【0019】

Further, the converter transformer 50 includes, for example, as shown in FIG. 3, a magnetic core 52 in which E-type cores each having three magnetic legs formed of a ferrite material are butted against each other. The control coil may be wound around the central magnetic leg, and the primary coil 50A and the secondary coil 50B may be wound around the magnetic legs on both sides.

【0020】

As shown in FIG. 4, the converter transformer 50 having such a structure saturates a part of the cores used in the primary coil 50A and the secondary coil 50B by the control current Ic flowing through the control coil 50C. , The leakage inductance Ll can be changed along with the inductance value L formed in the coil.

【0021】

In the current resonance type switching power supply device 100, one end of the secondary coil 50B of the converter transformer 50 is connected to the output terminal 26B via a current detection resistor 70.

【0022】

Further, the control circuit 60 is for detecting the fluctuation of the rectified output voltage output from the first voltage comparator 61 for detecting the fluctuation of the input voltage input to the switching circuit 5 and the rectifying / smoothing circuit 20. To the second voltage comparator 62, the third voltage comparator 63 that detects the voltage drop due to the current detection resistor 70 proportional to the load current flowing through the current detection resistor 70, and the control coil 50C of the converter transformer 50. It is composed of connected transistors 64 and the like.

【0023】

The first voltage comparator 61 compares the input voltage input to the switching circuit 5 with the first reference voltage Vref1, and uses the fluctuation of the input voltage as the first error voltage to set the first photocoupler. It is supplied to the resistance addition circuit 66 via.

【0024】

The resistance addition circuit 66 adds the first error voltage to the rectified output voltage output from the rectifying / smoothing circuit 20. Then, the second voltage comparator 62 compares the rectified output voltage to which the first error voltage is added with the second reference voltage Vref2, and changes the input voltage and the rectified output voltage as the comparison output. Outputs the corresponding voltage fluctuation information. By giving the comparison output of the second voltage comparator 62 to the base of the transistor 64 via the diode 67, the control current corresponding to the fluctuation of the input voltage and the rectified output voltage is passed through the control coil 50C. Controls the transistor 64.

【0025】

Further, the third voltage comparator 63 detects the voltage drop due to the current detection resistor 70, which is proportional to the load current flowing through the current detection resistor 70. By giving the comparison output of the third voltage comparator 63 to the base of the transistor 64, the transistor 64 is controlled so that a control current proportional to the load current flows through the control coil 50C.

【0026】

The control circuit 60 detects the input voltage input to the switching circuit 5 and the voltage drop by the current detection resistor 70 proportional to the load current flowing through the current detection resistor 70, and detects the voltage drop of the converter transformer 50. The leakage inductance Ll is controlled as follows.

【0027】

That is, when the input voltage is low and the load current is large, the maximum output power can be obtained and the minimum loss ratio can be obtained by preventing the control current Ic flowing through the control coil 50C from flowing.

【0028】

Then, when the input voltage rises and / or the load current decreases, the switching control circuit 25 operates so as to raise the switching frequency fsw and lower the output voltage, as shown in FIG. However, by passing the control current Ic through the control coil 50C according to the degree of increase in the input voltage and / or decrease in the load current, the leakage inductance Ll of the converter transformer 50 is reduced and is close to the switching frequency fsw. However, the leakage inductance Ll of the converter transformer 50 is controlled by the control circuit 60 so that the resonance frequency fr of the current resonance circuit 6 comes.

【0029】

In this current resonance type switching power supply device 100, the current IQ flowing by self-resonance is controlled by controlling the control current Ic flowing through the control coil 50C according to the degree of increase in input voltage and / or decrease in load current.₁The switch gloss caused by forcibly turning off the switch element 5A can be suppressed to a small value, and high conversion efficiency can always be maintained.

【0030】

The same effect can be obtained by using the oscillation frequency of the switching control circuit 25 as the information to be input to the control circuit 60.

【0031】

In the embodiment described above, as the converter transformer 50 in which the leakage inductance Ll can be changed, a transformer using a core with four magnetic legs or an E-type core with three magnetic legs is used, but a transformer using a control coil is used. It is also possible to use a transformer with a structure that can change the inductance of the transformer, or a transformer that changes the leakage inductance by changing the resistance in the magnetic circuit of the transformer (such as changing the gap amount) by a control signal. is there.

【0032】

In addition, the converter transformer T whose basic structure is shown in (A) of Fig. 6₁ Is a transformer T as shown in (B), (C), (D) in Fig. 6.₂, T₃, T₄And coil L₂, L₃, L₄, L₅It may be a structure that combines₂, T₃, T₄Coil L combined with₂, L₃, L₄, L₅By adopting a structure in which the inductance (corresponding to the leakage inductance) of the above can be changed by a control signal, it can be used as a converter transformer 50 in which the leakage inductance can be changed. In addition, each coil L₂, L₃, L₄, L₅Is a transformer T₂, T₃It may be provided on the secondary coil side instead of the primary coil side of.

【0033】

Further, as shown in FIG. 7, the converter transformer T is used.₁The current resonance circuit 6 is composed of the coil 10D and the resonance capacitor 6C provided independently of the primary coil and the secondary coil, and the inductance of the coil 10D of the current resonance circuit 6 is controlled by the control circuit 60. Even if the resonance frequency fr is made to match the switching frequency fsw, high conversion efficiency can be maintained.

【0034】

[Effect of the invention]

As described above, according to the present invention, by changing the leakage inductance of the converter transformer in response to changes in the input voltage and the load, the optimum resonance condition is always created and the switching loss is constantly reduced. Can be done.

【0035】

Therefore, according to the present invention, it is possible to provide a resonance type switching power supply device that can always obtain high conversion efficiency.

[Simple explanation of drawings]

[Figure 1]

It is a circuit diagram which shows the structure of the current resonance type switching power supply device which concerns on this invention.

[Figure 2]

It is a figure which shows typically the structure of the converter transformer which can change the leakage inductance used in the said current resonance type switching power supply apparatus.

[Fig. 3]

It is a figure which shows typically the other structure of the converter transformer which can change the leakage inductance used in the said current resonance type switching power supply apparatus.

[Fig. 4]

It is a figure which shows the relationship between the control current flowing through the control coil in the converter transformer, and leakage inductance.

[Fig. 5]

It is a waveform figure which shows the operation of the said current resonance type switching power supply apparatus.

[Fig. 6]

It is a figure which shows typically the structure of the converter transformer which can change the leakage inductance used in the said current resonance type switching power supply apparatus.

[Fig. 7]

It is a circuit diagram which shows the modification of the current resonance type switching power supply device which concerns on this invention.

[Fig. 8]

It is a circuit diagram which shows the basic circuit structure of the current resonance type switching power supply device known conventionally.

[Fig. 9]

It is a waveform figure which shows the ideal operation state of the conventional current resonance type switching power supply apparatus.

[Fig. 10]

It is a waveform figure which shows the actual operating state of the conventional current resonance type switching power supply apparatus.

[Explanation of symbols]

1 Commercial power supply, 2 Noise filter, 3 AC rectifier, 5 Switching circuit, 5A, 5B switching element, 6 Current resonance circuit, 6C resonance capacitor, 20 rectification / smoothing circuit, 21A, 21B diode, 22A, 22B capacitor, 23 choke Coil, 24 error detection circuit, 24A voltage comparator, 24B photocoupler, 25 switching control circuit, 26A, 26B output terminal, 50 converter transformer, 50A primary coil, 50B secondary coil, 50C control coil, 60 control circuit, 61 , 62,63 Voltage comparator, 64 transistors, 65 photocoupler, 66 resistance adder circuit, 70 current detection resistor, 100 current resonance type switching power supply