Power supply for an apparatus with standby operation

The invention relates to a power supply for a device with Standby mode, also referred to as standby mode. devices of this type are, for example, televisions or VCRs, in which certain stages, for. example, an infrared receiver and a Microprocessor, are active during standby operation to Infrared signals of a remote control to receive and evaluate can. Since the microprocessor already a power of about 750 Milliwatts needed and switching power supplies in standby mode a have poor efficiency, possess switching power supplies this Art in the standby mode power consumption of about 5 to 10 Watt and more.

To reduce the power loss in standby mode is made EP 0610700 A1 discloses a known switching power supply, which has a third operation, a so-called organic farm which. In This operation is only the infrared receiver and at its Output filter connected with operating voltage supplies. For this, a battery is used, the during operation is recharged regularly.

In US 5,353,215 and US 5,036,261 are power supplies described, in addition to a switching power supply for a Normal operation of a device, a separate, linear power supply have a standby mode.

The invention addresses the problem of providing a power supply unit of initially specify the type mentioned, the one in standby mode has very low fuel consumption and also the Shortcomings of battery operation avoids.

This object is achieved by the in claim 1 mentioned invention solved. Advantageous developments of the Invention are recited in the dependent claims.

According to the invention, in addition to a main switching power supply a separate switching power supply only for the standby mode used. Since this in standby mode only a few components with power supply, it can be very compact. So it may in particular operated at reduced operating voltage be, which his own power loss is minimized.

Since the separate switching power supply for a low operating voltage is interpreted by only 36 V, very low power consumption and having only a few components are needed, the entire PSU cheaper than the switching power supply of EP 0610700 A1. Also a separate linear power supply for the standby mode would not be cost-effective. The separate switch mode power supply Moreover, even for the transmission of control signals from the Secondary side are used for primary side.

The input voltage of the separate switched mode power supply is at least one current-limiting component, z. B. a Condenser, reduced so that it has a high resistance to Reducing the power loss.

In standby mode, the separate switching power supply only operates an infrared receiver on the secondary side, this is a downstream circuit for detecting received Infrared pulses and the start of the oscillator Main switching power supply, possibly even a light emitting diode for Operation indicator. By this measure consumed the entire PSU in standby mode only 100mW. The main switching power supply is held with only 4 mW in standby. The light-emitting diode for status display requires only 3 mW, as it with the high Switching frequency, 100 kHz, the standby switching power supply is operated. At this switching frequency has the LED a very good energy utilization.

Applications for this power supply type, in particular for Televisions, VCRs, satellite receivers, stereos and basically all devices with standby mode and Remote control. This low fuel consumption, a TV even over prolonged periods in standby mode be started, it consumes, for example one year Idle mode just about one kilowatt hour.

During standby operation may advantageously be the Oscillator and the driver stage of the main switching power supply in Willingness to be kept. This achieves the Main switching power supply after a short start-up phase its Normal operation and can in particular for the evaluation of needed remote control signals in microprocessor short time with voltage. This is advantageous in Switching power supplies, which in a wide input voltage range work from z. B. 90 V to 265 V and at low Input voltages have a long start-up phase.

In normal operation the Hautpschaltnetzteil works as Flyback converter and the separate switching power supply as Forward converter, wherein the switching frequency of the stand-by switching power supply synchronized by the main switching power supply becomes. By synchronizing the control is the secondary output voltages of the main switching power supply optimally, since this small voltage fluctuations this Output voltages due to the switching frequency are inevitable, do not cause interference effects. The separate Therefore, the switching power supply has an oscillator during the Normal operation as a monostable multivibrator, and during the Standby operation operates as an astable multivibrator. The separate switching power supply is fixed and requires self no rule information in standby mode.

The invention is described below by way of example based on schematic drawings explained in more detail. Show it:<dl tsize="7" compact="compact"><dt>Fig. 1</dt><dd>a block diagram of the complete power supply;</dd><dt>Fig. 2A</dt><dd>a diagram of the separate switching power supply;</dd><dt>FIG. 2b</dt><dd>a circuit diagram of the main switching power supply.</dd></dl>

In FIG. 1, the AC voltage VAC of 230 V network is located on a first rectifier G1 on, the main switching power supply, the via a capacitor C50 with a smoothed DC voltage provided. This is due to a primary winding W4 of a first Transformer L50, and a series-connected Switching transistor T85. The first contains the transformer L50 Secondary windings W7, W8 and W9 to produce Operating voltages V_sys, Vx and Vs +/-, and on the primary side a feedback winding W6 and an auxiliary winding W5 for primary-side voltage generation. The switching transistor T85 is Nomalbetrieb driven in by a driving circuit DR, the is connected to the feedback winding W6. On the primary side are also still a circuit OVP overvoltage protection and an oscillator start-up operation of the STO for the Main SMPS arranged. The oscillator runs at STO a frequency of about 1 kHz and causes a soft power-up the power supply unit after power on. In Nomalbetrieb swings the main switching power supply with a frequency depending on the load of about 60-150 kHz.

For the standby mode is a separate switching power supply provided, the two capacitors C1, C2 with the AC voltage VAC is connected. These act as lossless Reactances and thereby reduce the input voltage for a rectifier G2 and for the subsequent Switching power supply. Therefore, directly to the output of Rectifier G2 two zener diodes D5 and D6 connected in series are provided for generating operating voltages of 36 V and 6 V. The separate switching power supply further includes a second Transformer L1 with primary windings W1 and W3 and with a secondary-side winding W2. Connected in series to the coil W1 lying switching transistor T21 is from an oscillator OSC driven, the determined at a frequency of in standby mode 100 kHz swings. It operates both as a forward converter as also as a flyback converter, and generates via the connection 8 of the secondary-side winding W2 a Vorsorgungsspannung of 5 V for an infrared receiver IE and the other terminal 5 a supply voltage for a variable gain amplifier IS10. Of the Control amplifier IS10 is used to transfer Control information and a control information from the Secondary side to the primary side of the second transformer L1. This information is a control stage SEC and Compound 4 to the driver DR of the main switching power supply continued.

At the exit of the infrared receiver IE is a passive Filter circuit STS connected to the remote control pulses is matched to a corresponding infrared remote control. at Detection of remote control pulses it passes a signal over the control amplifier IS10 and the control stage SEC the Main switching power supply switches.

The oscillator OSC of the separate switching power supply is on electrical connections 5 and 6 with the main switching power supply connected, through which it is synchronized in normal operation. This is discussed further below with reference to Figures 2a and 2b explained.

In Fig. 2a, the separate switching power supply with its individual components shown. It is through electrical Compounds 1 to 8 with the main switching power supply, shown in FIG. 2b, respectively. Identical components are in the Fig. 1 and Figures 2a and 2b are the same, respectively.

The switching transistor T21 in Fig. 2a by a IP1 operational amplifier driven, of an oscillator is connected and a very low energy consumption having.

Via the connection 8 of the second transformer L1 is a smoothed DC voltage of 5 volts for operation of the generates infrared receiver IE. Its output signals are to a via a connection to a non-illustrated IR Microprocessor forwarded and also serve to Turning on the main switching power supply when the power supply in Idle mode is.

In standby mode, the transistor T31 is conducting. In recognition of infrared signals, the infrared receiver is IU at its OUT output signals from, by switching the transistor T40 and thus also off the transistor T31. This is about the transformer L1 a signal to the main switching power supply passed that turns this. Check-off signals can also other connections On / Off, the For example, a VCR or a Scart socket are connected, are fed. About a terminal 7 is in Normal operation of the main switching power supply of a voltage to the Cathode of the error amplifier IS10 created that the Normal operation maintains.

In the following, the operation of the main switching power supply described with reference to Fig. 2b. It is self-oscillating operated, wherein there is a positive feedback via the winding W6 of the first transformer L50 receives. The amplitude of the Collector current of the switching transistor T85 is a Resistor R85 monitored to the output voltages V_sys, Vx and keep +/- Vs constant. The switching frequency of the Main switching power supply varies due to the output side Load, the applied voltage VAC or due to magnetic properties of the first transformer L50. Of the Switching transistor T85 is operated in a mode in which this is disabled when its collector voltage in a Minimum is. This switching losses are significantly reduced. This mode is already in the previous Application DE 44 31 783 A1 in detail described and is therefore not explained here in detail. This operation is also a complete Energy transfer in the flyback converter mode achieved so that by the current control automatically achieves overload protection becomes.

The base current of the switching transistor T85 is via a throttle L80 limited in such a manner that it is proportional to the Collector current. The operation of this throttle is L80 already described in the earlier application DE 196 02 556 A1 and is therefore not discussed here. This control is a very efficient and fast switching action causes the reliably up to switching frequencies of 150 kHz works.

When the switching transistor T85 is switched through, then a Terminal 6 of the winding W6, transistor T77 and throttle L80 of generates base current for the switching transistor T85. Through a Capacitor C78, ​​the switching on of the switching transistor T85 supported. The locks of the switching transistor T85 is over a capacitor C75 and transistors T74, T72 and T77 causes. When the transistor T77 is steep flank locked a negative base current via the inductor L80 generated, the the switching transistor T85 is blocked.

The oscillator STO of Fig. 1 is shown in Fig. 2b by means of a wired operational amplifier IP2 realized. in the Startup mode after turning it switches the transistor T77 with a switching frequency of about 1 KHz by until the Main switching power supply in the higher frequency, self-oscillating Normal engine passes.

The main switching power supply during standby operation shut down because a consumption of less than one watt at a slightly larger-sized switching power supply to barely is accomplished. The on and off commands for this are to winding W2 of the second transformer L1 from the tapped transistor stage T30 and via the connection 4 to the Driver stage DR, Fig. 1, and capacitor C75, Fig. 2b, continued. Specifically in this case, the transistor T74 is in . Fig 2b controlled: this is an out signal (level: high) is switched through, thereby also transistor T72 is turned on, then the drive transistor T77 is blocked.

In standby mode, only the operational amplifier wired IP2 and the level transistor T74 via the connection 3 and 4 in Operation. The components of these stages are dimensioned such that the total power consumption of the main switching power supply in Standby mode is only 4 milliwatts. - The particular reference to the Fig. 2b illustrated embodiment is only a preferred Embodiment to keep the power consumption minimal. Other embodiments of this are within the scope of the claims are conceivable.

In normal operation, the operating voltage V_sys stabilized, for example, used for deflection in a television can be. This voltage is on the compound 8 and tapped off via a voltage divider to the control input the error amplifier IS10, in this embodiment, variable zener diode TL431 created. The higher the voltage V_sysis, the higher the current from the cathode to the anode and correspondingly higher is the "flyback" current for the transformer L1. At terminal 5 of transformer L1 is in the "flyback" a voltage at the more by the error amplifier or IS10 is less heavily loaded according to the operating voltage V_sys, This burden is on the primary side of the coil W3 can be tapped, the higher is the secondary-side load, thus lower the "flyback" voltage on the winding W2. This Control signal is transmitted via the transistor stage T30 and compound 4 as described above to the main switching power supply passed. Via the switching transistor T85 and the Transformer L1 is then closed the loop. By This direct control is a very high control gain reached.

In order to obtain a very stable control gain, the Switching frequency of the separate switching power supply during Normal operation synchronized by the main switching power supply. Through ports 5 and 6, both the switching frequency and the pulse-width ratio is controlled in the separate switching power supply. About compound 6, the transistor T11 is turned on, whereby the output of the operational amplifier IP1 on high Voltage is (5.6 V). When the switching transistor T85 of Main switching power supply blocks, produced at terminal 5 of the Winding W6, a positive voltage pulse, which via connection 5 to the negative input of the operational amplifier IP1 will be continued and its output switches to zero.

For switching power supplies a protective circuit with respect is on Surges necessary. This is realized by a Transistsorstufe TP90, Fig. 2b (OVP in FIG. 1), the monitored voltage of the primary-side winding W5 and in the case an over-voltage to the driver stage of the switching transistor T85 acts. If the normal voltage of the winding W5 to 10% is high, then the switching transistor T85 for a short Time off completely. After running the Main switching power supply again and returns to Normal mode, when the overvoltage only briefly had occurred. If the surge contrast further, the switching transistor TP85 is switched off again if the above Limit voltage is reached, and this shutdown cycle will be while maintained as the overvoltage condition exists. These Circuit has the following advantages over known circuits, limiting the output voltage at a high level: Through the cyclic turning on and off will increase the burden of Components kept low, also is the effective Consumption power is reduced greatly in the event of overvoltage. Will For example, the output voltages at a higher Voltage value of 10% only limited, so must this complied voltage value certain safety conditions will. This leads to unnecessary se costs.

The operation of the protection circuit in more detail below explained: If a fault occurs, the output voltages V_sys, Vx and Vs rise, so would also the voltage at a capacitor C95 to rise to the primary side. From a certain value defined by the Zener diode D90 and the Voltage divider in parallel with C95, the transistor T90 switches by and send a quick surge in the base of the pnp transistor T77. This locks, thereby preventing the Switching on again of the switching transistor T85. As soon as the first Transformer L50 has swung, can Skin switching power supply only of the start oscillator (IP2) again turn on. Therefore, this start-oscillator at the noninverting Input over a larger time constant so driven such that it for a certain time (defined by Capacitor C90) does not oscillate and thus tarnishing the Main switching power supply prevented.

Through this long interruption drop all output voltages the first transformer L50 correspondingly far from, so that the Transistor T90 locks again and after a certain time the capacitor C91 is discharged. By using only a Transistor stage T90 is the cost of materials for the highly effective protection circuit kept very low. Since it on the Primary side is disposed, and directly through transistor T72 on the driver transistor T77 acts, it speaks to the very quickly.

The reference to the Figures 2a and 2b is explained in detail power supply especially suitable for applications in a television set is operated with 230V. For other applications, for example, in a VCR, or for other input voltages, are appropriate modifications within the scope defined by the claims of the Scope conceivable.