CN218387275U - Auxiliary power supply circuit of switching power supply - Google Patents

Abstract

The utility model discloses an auxiliary power supply circuit of a switching power supply, wherein the collector of a first triode is connected with the cathode of a second diode, and the emitter is connected with the anode of a direct current output end; the collector of the first triode is connected with the base of the first triode through a first driving resistor; the anode of the first diode is connected with the first end of the auxiliary winding of the transformer, and the cathode of the first diode is connected with the anode of the second diode; the first end of the output capacitor is connected with the anode of the direct current output end, the second end of the output capacitor is grounded, and the second end of the auxiliary winding is grounded; the collector of the second triode is connected with the high-voltage direct-current power supply, and the emitter of the second triode is connected with the collector of the first triode; the collector of the second triode is connected with the base of the second triode through a second driving resistor; the collector of the third triode is connected with the base of the second triode, the emitter of the third triode is grounded, and the base is connected with the cathode of the first diode. The utility model discloses a switch tube can adopt the paster triode, reduces filter capacitance's quantity, practices thrift the cost, is favorable to the miniaturization of product.

Description

Auxiliary power supply circuit of switching power supply

[technical field]

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

[Background technique]

A switching power supply is a high-frequency power conversion device whose function is to convert a form of electrical energy (AC/DC) into the required DC power. The structure of the switching power supply is shown in Figure 1.

The auxiliary power supply of the switching power supply mainly involves the start-up power supply and continuous power supply of the control chip, and finally achieves the role of efficient and stable operation of the control chip.

The traditional auxiliary power supply circuit uses high-voltage start-up power supply and auxiliary winding power supply to supply power together. The application number is CN201210254466.5. The invention discloses an auxiliary power supply for switching power supply. It has two working modes, namely starting mode and normal working mode. When the power is turned on, it works in the startup mode, that is, the input high-voltage DC power supplies the control and drive parts to work after a certain current limit; when the control and drive parts work normally, the power transformer generates an alternating magnetic field, which passes through the auxiliary power supply. The coil is rectified and filtered, linearly stabilized and then supplied to the control and drive parts. At this time, it works in the normal working mode, and at the same time the high-voltage DC power supply electronic switch will be automatically disconnected, and no longer provide power to the control and drive parts.

The start-up module of the invention uses N-MOS, and the N-MOS is large in size, requires a large number of filter capacitors, and the product is large in size and high in cost.

[Content of the invention]

The technical problem to be solved by the utility model is to provide an auxiliary power supply circuit of a switching power supply with small volume and low cost.

In order to solve the above technical problems, the technical solution adopted by the utility model is, an auxiliary power supply circuit of a switching power supply, including a starting circuit, a working circuit and a DC output terminal, a switching power supply including a high-voltage DC power supply and a power transformer of the main circuit, and a working circuit Including the first triode, the first drive resistor, the first diode, the second diode, the first regulator tube, the output capacitor and the auxiliary winding of the power transformer; the starting circuit includes the second triode, the second drive resistor, the second regulator tube and the third triode; the collector of the first triode is connected to the cathode of the second diode, and the emitter is connected to the positive pole of the DC output terminal; the collector of the first triode passes through the second A drive resistor is connected to the base of the first triode and the cathode of the first voltage regulator, and the anode of the first voltage regulator is grounded; the anode of the first diode is connected to the first end of the auxiliary winding, and the first diode The cathode of the output capacitor is connected to the anode of the second diode; the first terminal of the output capacitor is connected to the positive pole of the DC output terminal, the second terminal is grounded, and the second terminal of the auxiliary winding is grounded; the collector of the second triode is connected to the high-voltage DC power supply, and the emission The pole is connected to the collector of the first transistor; the collector of the second transistor is connected to the base of the second transistor and the cathode of the second voltage regulator through the second drive resistor, and the anode of the second voltage regulator is grounded ; The collector of the third transistor is connected to the base of the second transistor, the emitter of the third transistor is grounded, and the base is connected to the cathode of the first diode.

In the aforementioned auxiliary power supply circuit, the start-up circuit includes a third diode, the anode of the third diode is connected to the high-voltage DC power supply, and the cathode is connected to the collector of the second triode.

In the auxiliary power supply circuit described above, the starting circuit includes a current-limiting resistor and a pull-down resistor, and the current-limiting resistor is connected to the base of the third transistor and the cathode of the first diode; the base of the third transistor is pulled-down resistor to ground.

In the auxiliary power supply circuit described above, the working circuit includes two energy storage capacitors, the first energy storage capacitor is connected between the cathode of the first diode and the ground, and the second energy storage capacitor is connected between the cathode of the second diode and the ground.

In the auxiliary power supply circuit mentioned above, the first triode, the second triode and the third triode are patch triodes.

The switch tube in the auxiliary power supply circuit of the utility model can adopt patch transistors, which requires less filter capacitors, can save costs, and is beneficial to product miniaturization.

[Description of drawings]

Below in conjunction with accompanying drawing and specific embodiment, the utility model is described in further detail.

Fig. 1 is the circuit block diagram of prior art switching power supply auxiliary power supply

Fig. 2 is a circuit diagram of the auxiliary power supply of the switching power supply according to the embodiment of the present invention.

[Detailed ways]

The structure and principle of the auxiliary power supply circuit of the switching power supply in the embodiment of the utility model are shown in Figure 2, including a start-up circuit, a working circuit and a DC output terminal. The switching power supply includes a high-voltage DC power supply and a power transformer for the main circuit,

The working circuit includes the first triode Q9, the first drive resistor R43, the first diode D26, the second diode D6, the first voltage regulator tube Z3, the output capacitor CE8, the energy storage capacitor C158, and the energy storage capacitor C40 And the auxiliary winding T3-B of the power transformer. The start-up circuit includes a third diode D5, a second transistor Q19, a second drive resistor R80, a first FG voltage regulator transistor Z8 and a third transistor Q20.

The collector of the first triode Q9 is connected to the cathode of the second diode D6, and the emitter is connected to the anode VDD of the DC output terminal. The collector of the first triode Q9 is connected to the base of the first triode Q9 and the cathode of the first voltage regulator transistor Z3 through the first driving resistor R43, and the anode of the first voltage regulator transistor Z3 is grounded. The anode of the first diode D26 is connected to the first end of the auxiliary winding T3-B, and the cathode of the first diode D26 is connected to the anode of the second diode D6. The first end of the output capacitor CE8 is connected to the positive pole VDD of the DC output end, the second end is grounded, and the second end of the auxiliary winding T3-B is grounded. The first energy storage capacitor C158 is connected between the cathode of the first diode D26 and the ground, and the second energy storage capacitor C40 is connected between the cathode of the second diode D6 and the ground.

The anode of the third diode D5 is connected to the high voltage DC power supply +28VOUT, and the cathode is connected to the collector of the second triode Q19. The emitter of the second transistor Q19 is connected to the collector of the first transistor Q9. The collector of the second transistor Q19 is connected to the base of the second transistor Q19 and the cathode of the second voltage regulator transistor Z8 through the second driving resistor R80, and the anode of the second voltage regulator transistor Z8 is grounded. The collector of the third transistor Q20 is connected to the base of the second transistor Q19, the emitter of the third transistor Q20 is grounded, and the base of the third transistor Q20 is connected to the first diode through the current limiting resistor R119 The cathode of the tube D26, and grounded through the pull-down resistor.

The first transistor Q9, the second transistor Q19 and the third transistor Q20 are SMD transistors.

The working process of the auxiliary power supply circuit of the switching power supply in the embodiment of the utility model is as follows:

The high level of the high-voltage DC power supply +28VOUT is rectified by the third diode D5, and the second triode Q19 is given a 18V high level regulated by the 18V regulator Z8 through the drive resistor R80, and the second triode Q19 is turned on. Then through the driving resistor R43, a 12V high level regulated by the 12V voltage regulator tube Z3 is given to the base of the first transistor Q9 to turn on the transistor Q9, and the positive pole VDD of the DC output terminal provides a 12V start-up voltage to the switching power supply control chip. After the control chip is started, the auxiliary winding T3-B of the main circuit power transformer starts to work, and the alternating current output by the auxiliary winding T3-B is rectified by the first diode D26 to obtain a high voltage of 16V. The high voltage of 16V gives a high level to the base of the third transistor Q20 through the current-limiting resistor R119, and turns on the third transistor Q20 to turn the base level of the second transistor Q19 into a low level. The second transistor Q19 is turned off. The 16V high level provided by the auxiliary winding is rectified by the second diode D6, and the base of the first triode Q9 is given a 12V high level regulated by a 12V regulator tube through the driving resistor R43 to keep the triode Q9 continuously open , so that the auxiliary winding T3-B alone supplies power to the VDD of the control chip, and the electrolytic capacitors C158, C40 and CE8 function as energy storage, which can improve the stability of the VDD power supply level.

The switching tube of the switching power supply in the above embodiments of the present invention adopts a patch triode, which requires a small number of filter capacitors, which can save costs and is beneficial to the miniaturization of the product.

Claims (5)

1. An auxiliary power supply circuit of a switching power supply, comprising a start-up circuit, a working circuit and a DC output terminal, the switching power supply comprising a high voltage DC power supply and a power transformer of the main circuit, characterized in that the working circuit comprises a first triode, a first Drive resistor, first diode, second diode, first voltage regulator tube, output capacitor and auxiliary winding of power transformer; start-up circuit includes second triode, second drive resistor, second voltage regulator tube and The third triode; the collector of the first triode is connected to the cathode of the second diode, and the emitter is connected to the positive pole of the DC output terminal; the collector of the first triode is connected to the first triode through the first drive resistor The base of the first Zener tube and the cathode of the first Zener tube, the anode of the first Zener tube is grounded; the anode of the first diode is connected to the first end of the auxiliary winding, and the cathode of the first diode is connected to the second diode Anode; the first terminal of the output capacitor is connected to the positive pole of the DC output terminal, the second terminal is grounded, and the second terminal of the auxiliary winding is grounded; the collector of the second triode is connected to the high-voltage DC power supply, and the emitter is connected to the collector of the first triode electrode; the collector of the second transistor is connected to the base of the second transistor and the cathode of the second voltage regulator through the second drive resistor, and the anode of the second voltage regulator is grounded; the collector of the third transistor The base of the second triode is connected, the emitter of the third triode is grounded, and the base is connected to the cathode of the first diode. 2. The auxiliary power supply circuit according to claim 1, wherein the start-up circuit comprises a third diode, the anode of the third diode is connected to the high-voltage DC power supply, and the cathode is connected to the collector of the second triode. 3. The auxiliary power supply circuit according to claim 1, wherein the starting circuit comprises a current limiting resistor and a pull-down resistor, and the current limiting resistor is connected to the base of the third triode and the cathode of the first diode; The base of the triode is grounded through a pull-down resistor. 4. The auxiliary power supply circuit according to claim 1, wherein the working circuit comprises two energy storage capacitors, the first energy storage capacitor is connected between the cathode of the first diode and the ground, and the second energy storage capacitor Connected between the cathode of the second diode and ground. 5. The auxiliary power supply circuit according to claim 2, wherein the first triode, the second triode and the third triode are chip triodes.

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