CN201039001Y - A standby circuit for switch power - Google Patents

Abstract

The utility model provides a standby circuit of a switch power, which comprises an AC detection circuit. The AC detection circuit comprises a secondary rectifier circuit, a first filter voltage dividing circuit, a first triode, a third resistance, a fourth resistance, and a second triode; wherein, the second rectifier circuit comprises a first diode and a voltage dividing resistance which are connected with each other in series; the AC electricity processed by an EMI filter circuit sequentially passes through the first diode and the voltage dividing resistance of the second rectifier circuit, and are output to the first filter voltage dividing circuit and a basal pole of the first triode; the voltage dividing resistance comprises a first resistance; the first filter voltage dividing circuit comprises a first capacitance and a second capacitance which are connected with each other in parallel; the output terminal of the first filter voltage dividing circuit is grounded; an emitter of the first triode is grounded; a collector of the first triode is output to a third resistance, a fourth resistance, and the basal pole of the second triode which are connected with each other in parallel; the third resistance is connected with the main voltage of the standby control circuit; the fourth resistance is grounded; the emitter of the second triode is grounded; the collector of the second triode is connected with the standby control circuit.

Description

A standby circuit of switching power supply

technical field

The utility model relates to, in particular to a standby circuit of a switching power supply.

Background technique

With higher and higher requirements for energy saving, currently, the standby power consumption of home appliances, especially video home appliances, is required to be lower and lower. In order to meet this demand, the current LCD TV adopts a working mode of a main circuit and an auxiliary standby circuit, which is realized by reducing the power consumption of the auxiliary standby circuit itself.

As shown in Figure 1, the input alternating current is filtered by EMI and rectified by AC to the energy storage circuit. The energy storage circuit can be a large capacitor, and the charge stored in the energy storage circuit is output in two ways, one to the main circuit, and the main circuit passes through After the main circuit converter transforms the voltage, it supplies power to the main board and backlight of the LCD TV: one way supplies power to the standby control circuit, and the standby converter converts the voltage to supply power to the standby frame chip and indicator lights on the main board. As long as the standby control circuit has voltage, it will work all the time, and the standby control circuit will stop working only when the voltage is lowered to its lowest voltage point, without taking other measures.

When the TV is in the viewing state, the standby CPU sends a power-on signal. When the standby control circuit receives the power-on signal, the main circuit starts to work, so that the main circuit converter has a voltage output, and the backlight of the LCD TV is lit. , the motherboard starts to work, and the user can watch TV programs.

When the TV is in standby, the standby control chip sends a standby control signal, and when the standby control circuit receives the standby signal, the main circuit stops working, so that the main circuit converter has no voltage output, the backlight of the LCD TV is extinguished, and the main board Not working, we can only see the standby light is on. Due to the current higher and higher energy requirements, the energy consumption required for standby is getting smaller and smaller, that is, the power consumption for standby will be below 3 watts. And the power consumption of our LCD TVs will be between small and large sizes. Between 100 watts and several hundred watts, that is, the capacity requirement for large capacitors also increases with the increase of power. When in standby, the input 220V AC passes through the EMI inductor, rectifies and filters, and then reaches the large capacitor. Therefore, the large capacitor stores a lot of charge during standby. When the AC power is turned off during standby, the energy stored in the large capacitor will be consumed by a small power consumption during standby. It will take a while, that is, the capacitance of the energy storage circuit will drop. It will take some time after reaching the minimum operating voltage of the standby thick film block. Even if the AC power is turned off during this period, the thick film circuit module of the standby control circuit will continue to work under the action of the energy storage circuit. There is still output voltage after the device, so the standby indicator light is still on after the standby power is turned off.

That is, when the power supply is in the standby state, if the user executes the shutdown operation, because the high-voltage capacitor is large at this time, a lot of charge is stored. When the user turns off the power supply, the charge discharge is very slow, and the indicator light will be on for a long time. Bring certain trouble, promptly the user does not know whether to turn off the power supply, cause sometimes the user turns on and off repeatedly repeatedly, has brought inconvenience to the user.

Moreover, when the user turns off the power supply, the standby control circuit drops from 220V voltage all the way to the minimum operating voltage of the standby control circuit, and the corresponding current will increase greatly at the minimum operating voltage, which will easily lead to unstable performance and affect the power supply. stability.

Therefore, there are defects in the prior art and need to be improved.

Utility model content

The purpose of this utility model is to provide a standby circuit of a switching power supply. By increasing the detection of the presence or absence of AC voltage to turn off the standby circuit, the power indicator light can be quickly turned off after the user turns off the power, so that the user can immediately know that the power has been successfully turned off .

The technical scheme of the utility model is as follows:

A standby circuit of a switching power supply, which includes an EMI filter circuit, a first rectifier circuit, an energy storage circuit, a main circuit, a standby control circuit and a standby control chip, and alternating current flows through the EMI filter circuit, the first rectifier circuit, and the energy storage circuit in sequence sent to the main circuit and output, and sent to the standby control circuit and output through the energy storage circuit; wherein, it also includes an AC detection circuit; the AC detection circuit includes a second rectifier circuit, a first filter voltage divider circuit, a first three-pole Tube Q604A, the second voltage dividing resistor, the third voltage dividing resistor and the second triode Q615; the second rectification circuit includes the first diode D11 and the first voltage dividing resistor connected in series; the EMI filter circuit processed After the alternating current flows through the first diode D11 and the voltage dividing resistor of the second rectifying circuit in sequence, it is respectively output to the first filter voltage dividing circuit and the base of the first triode Q604A; the first voltage dividing resistor Including a first resistor R41; the first filter voltage divider circuit includes a parallel first capacitor C672c and a second resistor R51; its output terminal is grounded; the emitter of the first triode Q604A is grounded, and the first triode The collector of Q604A is respectively output to the second voltage dividing resistor, the third voltage dividing resistor and the base of the second triode Q615; the second voltage dividing resistor includes the third resistor R648, which is connected to the main voltage of the standby control circuit The third voltage dividing resistor includes a fourth resistor R47, which is grounded; the emitter of the second triode Q615 is grounded, and the collector of the second triode Q615 is connected to the standby control circuit.

The standby circuit, wherein, the AC detection circuit further includes a second filter voltage divider circuit, which is arranged between the second rectifier circuit and the first filter voltage divider circuit, and the output ends of the second rectifier circuit are respectively connected to the first The sixth resistor R50 of the two filter voltage divider circuits and the second capacitor C673 and the fifth resistor R48 connected in parallel; the output terminals of the second capacitor C673 and the fifth resistor R48 are grounded; the output terminals of the sixth resistor R50 are connected with the first filter voltage divider The input terminals of the circuit are connected.

The standby circuit further includes a third capacitor C672A connected in parallel with the third voltage dividing resistor.

In the standby circuit, wherein, the second rectification circuit further includes a second diode, which is connected in parallel with the first diode D11 and connected in series with the first voltage dividing resistor.

In the standby circuit, the first voltage dividing resistor further includes other resistors connected in series or in parallel with the first resistor R41, or a group of resistors connected in series or in parallel with the first resistor R41.

In the standby circuit, the second voltage dividing resistor further includes other resistors connected in series or in parallel with the third resistor R648, or a group of resistors connected in series or in parallel with the third resistor R648.

In the standby circuit, the third voltage dividing resistor further includes other resistors connected in series or in parallel with the fourth resistor R47, or a group of resistors connected in series or in parallel with the fourth resistor R47.

In the standby circuit, the first triode and/or the second triode are MOSFETs.

With the above scheme, when the power supply is turned off during standby, the utility model shuts down the standby circuit by increasing the detection of the presence or absence of AC voltage, thereby stopping the standby thick film circuit, which greatly accelerates the standby working time when shutting down , so as to achieve the standby power off and the standby indicator light can go out quickly, allowing the user to immediately know that the power has been turned off; and the circuit used is simple in structure, low in cost, and the standby power consumption can reach below 1 watt; and due to the existence of the detection circuit, It makes the power supply work more stable, more reliable, and more adaptable to the needs of the market.

Description of drawings

FIG. 1 is a schematic diagram of a standby circuit in the prior art;

The schematic diagram of the standby circuit of Fig. 2 the utility model;

Fig. 3 is a schematic diagram of an embodiment of the AC detection circuit of the present invention;

Fig. 4 is a schematic diagram of another embodiment of the AC detection circuit of the present invention.

Detailed ways

Preferred embodiments of the present utility model are described in detail below.

The utility model provides a standby circuit of a switching power supply, as shown in Figure 2, which includes an EMI filter circuit, a first rectifier circuit, an energy storage circuit, a main circuit, a standby control circuit and a standby control chip, and the alternating current flows through the The EMI filter circuit, the first rectifier circuit, and the energy storage circuit are delivered to the main circuit and output, and are delivered to the standby control circuit through the energy storage circuit and output; wherein, the L terminal is the output phase line (fire wire), and the N terminal is the output neutral line ( zero line). The standby circuit also includes an AC detection circuit, and the AC power processed by the EMI filter circuit is output to the standby control circuit through the AC detection circuit. In practical applications, a PFC (Power Factor Correction, power factor correction) circuit can be added between the first rectifier circuit, the energy storage circuit, and the main circuit, or a feedback circuit and other existing circuits that have been used in the standby circuit can be added. These prior arts will not be described in detail here.

As shown in Figure 3, the AC detection circuit includes a second rectifier circuit, a first filter voltage divider circuit, a first transistor Q604A, a second voltage divider resistor, a third voltage divider resistor and a second transistor Q615 ; The second rectifier circuit includes a series connection of the first diode D11 and the first voltage divider resistor; the alternating current processed by the EMI filter circuit flows through the first diode D11 and the voltage divider resistor of the second rectifier circuit in sequence After that, they are respectively output to the first filter voltage divider circuit and the base of the first triode Q604A.

The first voltage dividing resistor includes a first resistor R41; it may also include other resistors connected in series or in parallel with the first resistor R41, or a group of resistors connected in series or in parallel with the first resistor R41. For example, the series resistor group obtained by connecting the first resistor R41 in series with another resistor is used as the first voltage dividing resistor; or the series resistor group is connected in parallel with one or more other resistors to obtain a resistor group as the first voltage dividing resistor . In actual use, using multiple resistors as the first voltage dividing resistor is beneficial to the wiring of the PCB. The following second and third voltage dividing resistors are similar.

The first filter voltage divider circuit includes a first capacitor C672c and a second resistor R51 connected in parallel; its output end is grounded for filter voltage divider.

The emitter of the first transistor Q604A is grounded, and the collector of the first transistor Q604A outputs to the second voltage dividing resistor, the third voltage dividing resistor and the base of the second transistor Q615 respectively. The first triode can also be an N-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor, Metal-Oxide-Semiconductor Field Effect Transistor), and the second triode can also be an N-channel MOSFET tube. When the working voltage of the MOSFET tube, that is, the voltage difference between the gate and the source is greater than 5V, the tube will be turned on. The emitter of the second transistor Q615 is grounded, and the collector of the second transistor Q615 is connected to the standby control circuit. The second triode can also be a MOSFET, as described above in detail.

As shown in Fig. 3, the on-resistance of the low-voltage MOSFET tube of the first triode Q604A or the pin 1 and pin 3 of the second triode Q615 is very small, and the current it bears is relatively large. When the AC power supply is turned off, the first triode Q604A has no base voltage and base current, and this tube is cut off. A VCC generated by the standby transformer itself to supply power to the standby control circuit can be sensed by the auxiliary winding of the transformer. After rectification, current limiting, filtering and voltage stabilization, a stable voltage is provided to the thick film circuit. This voltage is affected by the input voltage of the energy storage circuit. When the voltage of the energy storage circuit drops to 80V, the thick film circuit stops working. After the stable Vcc voltage is divided by R648 and R47, the ground voltage at pin 1 of Q615 is greater than 5V so that Q615 is turned on, thereby connecting the collector of the second triode Q615 with the thick film circuit of the standby circuit The voltage of the connection point drops to a voltage lower than 1V, so that the thick film circuit module cannot reach the start-up voltage and shut down the chip to work, and finally achieve the purpose of shutting down the output voltage.

The thick-film circuit can be an ICE3A1565 thick-film power module, which has a soft-start pin CS pin, that is, the first pin of the thick-film block. Some thick-film blocks from other companies do not have this function pin, but the standby The circuit is still applicable to other thick film power modules to achieve this function, but the circuit can only be used after some proper adjustments. That is, the second pin of Q615, that is, the collector of the triode, or the drain of the MOSFET can be connected to the second pin of the thick film block, that is, the FB pin. The specific implementation circuit belongs to the prior art and will not be described here. repeat. For example, the utility model circuit can be used to control the FB (feedback input terminal) function pin of the NCP1010-14 series thick film power supply block of ON SEMICONDUCTOR, or the STR of Shanken (SANKENELECTRIC CO, LTE) company. -6159 FB pin, or the FB function pin of ST's L6590A series thick film power block. However, different chips need to control different pin positions and names, which should not be interpreted as limiting the application of the present invention. Each company's power module has a unified pin position, that is, each power module has a feedback terminal. Although their names may be different, their functions will be the same. It is the feedback input pin. Generally, the feedback input pin of the thick film power module is connected to the fourth pin of the optocoupler.

The second voltage dividing resistor includes a third resistor R648, which is connected to the main voltage of the standby control circuit; the second voltage dividing resistor may also include other resistors connected in series or in parallel with the third resistor R648, or connected with the third resistor R648 Groups of resistors connected in series or parallel. The second voltage-dividing resistor is connected to a VCC voltage generated by the standby circuit, thereby forming a voltage-dividing circuit with the third voltage-dividing resistor, providing a gate drive voltage for the second triode Q615, and providing a gate driving voltage for the first triode Q615. Tube Q604A provides collector bias current, that is, when the AC power is turned off, the first transistor Q604A has no base voltage and current, and the first transistor Q604A is cut off. When there is AC voltage, the first transistor Q604A has Base voltage and collector current, so that the first triode Q604A is turned on.

The third voltage dividing resistor includes a fourth resistor R47, which is grounded; the third voltage dividing resistor may also include other resistors connected in series or in parallel with the fourth resistor R47, or a group of resistors connected in series or in parallel with the fourth resistor R47.

As shown in Figure 4, the AC detection circuit of the standby circuit also includes a second filter voltage divider circuit, which is arranged between the second rectifier circuit and the first filter voltage divider circuit, and the output ends of the second rectifier circuit are respectively connected to The sixth resistor R50 of the second filter voltage divider circuit and the second capacitor C673 and the fifth resistor R48 in parallel; the output terminals of the second capacitor C673 and the fifth resistor R48 are grounded; the output terminal of the sixth resistor R50 is connected to the first The input ends of the filter voltage divider circuit are connected together. Moreover, the sixth resistor R50 forms a RC filter together with the first capacitor C672c and the second capacitor C673, which can filter out some peak noise and improve the stability of the circuit, because if there is a In the case of noise interference, the interference signal can be effectively filtered out through the first capacitor C672c, the second capacitor C673 and the sixth resistor R50, which can improve the performance of the standby circuit.

It may also include a third capacitor C672A, which is connected in parallel with the third voltage dividing resistor, and the third capacitor C672A may function as a filter and increase the stability of the standby circuit.

The second rectification circuit further includes a second diode connected in parallel with the first diode D11 and connected in series with the first voltage dividing resistor.

Specifically, when there is AC input, some interference signals are filtered out through the EMI filter in the AC path, and then rectified by D11 to remove the negative half-cycle AC power, divided by R41 and R48, and stored by C673 , filtering, the divided voltage is then divided and current-limited by R50 and R51 to provide a base voltage for Q604A, because there is alternating current, the standby circuit works under normal conditions, the collector bias current of Q604A can be obtained through R648, So that Q604A is turned on. The conduction of Q604A causes pin 1 of Q615, that is, the gate, to be at low level, and Q615 is cut off, which does not have any impact on the thick film circuit in the standby circuit, and the standby thick film circuit normally controls the duty cycle of the switching power supply.

When standby, the main circuit does not work, and the display screen is black. At this time, the working conditions of standby are basically the same as when watching normally. Q604A is still on, and Q615 is still off. At this time, if the AC power is cut off again, because the AC power is cut off, there will be no voltage and current flowing through D11, and the base of Q604A will have no base voltage and current, so that Q604A will be cut off immediately. Once Q604A is cut off, the collector of Q604A will be high immediately. Level, so that Q615 is turned on; make the standby thick film block immediately stop working. For example, when the PIN1 pin of the thick film circuit module of the standby circuit is connected to the collector of the second transistor Q615 of the AC detection circuit, the voltage of the PIN1 pin of the thick film circuit module is pulled to close to zero volts. Therefore, it can be realized that the standby output voltage can be turned off immediately after the standby power is turned off, so that the standby indicator light can be turned off immediately.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present utility model.

Claims (8)

1. A standby circuit of a switching power supply, which comprises an EMI filter circuit, the first rectifier circuit, an energy storage circuit, a main circuit, a standby control circuit and a standby control chip, and alternating current flows through the EMI filter circuit, the first rectifier circuit, the storage circuit successively The energy circuit is sent to the main circuit and output, and the energy storage circuit is sent to the standby control circuit and output; it is characterized in that it also includes an AC detection circuit; The AC detection circuit includes a second rectifier circuit, a first filter voltage divider circuit, a first transistor (Q604A), a second voltage divider resistor, a third voltage divider resistor and a second transistor (Q615); the The second rectifier circuit includes a first diode (D11) and a first voltage divider resistor connected in series; the alternating current processed by the EMI filter circuit flows through the first diode (D11) and the voltage divider of the second rectifier circuit in sequence After the resistance, it is respectively output to the first filter voltage divider circuit and the base of the first triode (Q604A); the first voltage divider resistor includes a first resistor (R41); the first filter voltage divider circuit includes a parallel The first capacitor (C672c) and the second resistor (R51); its output terminal is grounded; The emitter of the first transistor (Q604A) is grounded, and the collector of the first transistor (Q604A) is respectively output to the second voltage dividing resistor, the third voltage dividing resistor and the second transistor (Q615). base; The second voltage dividing resistor includes a third resistor (R648), connected to the main voltage of the standby control circuit; The third voltage dividing resistor includes a fourth resistor (R47), grounded; The emitter of the second transistor (Q615) is grounded, and the collector of the second transistor (Q615) is connected to the standby control circuit. 2. The standby circuit according to claim 1, wherein the AC detection circuit further comprises a second filter voltage divider circuit, arranged between the second rectifier circuit and the first filter voltage divider circuit, the second rectifier circuit The output terminals of the second filter voltage divider circuit are respectively connected to the sixth resistor (R50) and the second capacitor (C673) and the fifth resistor (R48) connected in parallel; the second capacitor (C673) and the fifth resistor (R48) The output terminal of the sixth resistor (R50) is connected to the input terminal of the first filter voltage divider circuit. 3. The standby circuit according to claim 1, further comprising a third capacitor (C672A) connected in parallel with the third voltage dividing resistor. 4. The standby circuit according to claim 1, characterized in that, the second rectifier circuit further comprises a second diode connected in parallel with the first diode (D11) and connected in series to the first divided voltage resistance. 5. The standby circuit according to claim 1, characterized in that, the first voltage dividing resistor further includes other resistors connected in series or in parallel with the first resistor (R41), or connected in series or in parallel with the first resistor (R41) resistor group. 6. The standby circuit according to claim 1, characterized in that, the second voltage dividing resistor further includes other resistors connected in series or in parallel with the third resistor (R648), or connected in series or in parallel with the third resistor (R648) resistor group. 7. The standby circuit according to claim 1, characterized in that, the third voltage dividing resistor further comprises other resistors connected in series or in parallel with the fourth resistor (R47), or connected in series or in parallel with the fourth resistor (R47) resistor group. 8. The standby circuit according to any one of claims 1 to 7, wherein the first triode and/or the second triode are MOSFETs.

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