High-voltage flyback power supply circuit

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By employing a single-winding transformer and a series-parallel structure of multiple switching transistors in the high-voltage flyback power supply, the manufacturing process is simplified, costs and failure rates are reduced, stable voltage control is achieved, and the problems of complex manufacturing processes and high costs of high-voltage flyback power supplies are solved.

CN223713865UActive Publication Date: 2025-12-23BLUESIGHT POWER SUPPLY LTD

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Patent Information

Application Number: CN202520025510.8
Authority / Receiving Office: CN · China
Patent Type: Utility models(China)
Current Assignee / Owner
Filing Date: 2025-01-06
Publication Date: 2025-12-23
Estimated Expiration: 2035-01-06

AI Technical Summary

Technical Problem

Existing high-voltage flyback power supplies suffer from complex manufacturing processes and high costs, especially when multiple sets of transformer primary windings are connected in series, leading to complex production processes and increased costs.

Method used

A single-winding transformer is used. Multiple switching transistors are connected in series on the primary side of the transformer, and voltage-dividing capacitors and resistors are connected in parallel. The drive signal is only input to the drive terminal of the last switching transistor at the low voltage end. The drive terminals of the remaining switching transistors are connected to DC drive voltage. A diode and resistor are connected in antiparallel between the drive terminal and the second terminal to achieve series control of multiple switching transistors.

Benefits of technology

It simplifies the transformer manufacturing process, improves reliability, reduces the cost and failure rate of the drive circuit, achieves stable voltage control, and solves the problems of complex processes and high costs caused by multiple series connection of transformer main windings.

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Patent Text Reader

Abstract

The utility model provides a high-voltage flyback power supply circuit, which belongs to the field of flyback switching power supplies and comprises a transformer T1, an input circuit arranged on a primary side of the transformer T1 and an output circuit arranged on a secondary side of the transformer T1. The input circuit comprises N switching tubes, N divider resistors, N divider capacitors, N driving resistors, N-1 diodes, N-1 voltage stabilizing diodes and N-1 protective resistors, the N switching tubes are sequentially connected in series between the synonym end of the primary side of the transformer T1 and the ground, the driving end of the first switching tube inputs a driving signal, and the driving end of the second switching tube inputs a driving signal; the driving ends of the other switching tubes are respectively connected with a direct-current driving voltage; the main winding of the transformer adopts a single winding, the process is simple, the reliability is improved, a plurality of switching tubes are connected in series at the low voltage end, a voltage dividing capacitor and a voltage dividing resistor are connected in parallel between the first end and the second end of each switching tube, and only a driving signal needs to be input at the driving end of the last switching tube at the low voltage end, so that a driving transformer and a driving circuit are greatly saved; the cost is reduced.

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Description

TECHNICAL FIELD

[0001] The utility model relates to flyback switching power supply technical field especially relates to a high voltage flyback power supply circuit. BACKGROUND

[0002] With power supply system voltage promotion to DC2000V above, the power MOS pipe of flyback switching power supply's withstand voltage requirement is higher, single pipe cannot satisfy the demand, and currently high voltage flyback power supply has two kinds of coping schemes: one is through the front stage step-down and makes the input voltage of power supply drop to the voltage grade that pipe adapts, and this scheme has the defect that the front stage step-down will produce the relatively big loss, and another scheme is that the main winding of transformer primary side adopts multiple groups in series, for example as shown in the figure, and this scheme has the defect that: transformer primary side tap is relatively many, leads to the complex production technology of transformer, and each group of switch tube needs independent drive, leads to cost increase. Figure 1 UTILITY MODEL CONTENTS

[0003] The utility model is used to solve the problem of the existing high voltage flyback power supply process complex, cost bigger.

[0004] The utility model discloses a high -pressure flyback power supply circuit, including transformer T1, the input circuit of primary side and the output circuit of secondary side of setting in transformer T1, input circuit includes N switch tube, N voltage divider resistance, N voltage divider capacitor, N drive resistance, N-1 diode, N-1 voltage stabilizing diode, N-1 protection resistance, N switch tube is connected in series between the opposite name end of primary side of transformer T1 and ground in proper order, wherein the first end of N switch tube connects the opposite name end of primary side of transformer T1, the second end of N switch tube connects the first end of N-1 switch tube, by analogy, the second end of second switch tube connects the first end of first switch tube, and the second end of first switch tube is grounded, and voltage divider resistance and voltage divider capacitor are connected in series and are connected between the first end and the second end of N switch tube one by one, N drive resistance is connected in series between high -voltage input anode and ground in proper order, and the connecting point between N drive resistance and N-1 drive resistance connects the drive end of N switch tube, and N-1 diode is connected between the drive end of N switch tube to the drive end of second switch tube and the second end of N switch tube to the second end of second switch tube one by one, wherein the cathode of N diode, anode connects the drive end, the second end of N switch tube, by analogy, the cathode of first diode, anode connects the drive end, the second end of second switch tube, N-1 voltage stabilizing diode is connected between the drive end of N switch tube to the drive end of second switch tube and the second end of N switch tube to the second end of second switch tube one by one, wherein the cathode of N voltage stabilizing diode, anode connects the drive end, the second end of N switch tube, by analogy, the cathode of first voltage stabilizing diode, anode connects the drive end, the second end of second switch tube, N-1 protection resistance is connected in parallel between the two ends of N-1 voltage stabilizing diode one by one, and the drive end of first switch tube inputs drive signal, and the drive end of remaining switch tube is connected direct current drive voltage respectively, and N is the positive integer greater than or equal to 2.

[0005] In the high -voltage flyback power supply circuit of the utility model, the transformer main winding adopts single winding, and the process is simple, the reliability increases, a plurality of switch tubes are connected in series at the low voltage end, the first end and the second end between each switch tube are connected in parallel voltage divider capacitor and voltage divider resistance, only need to input drive signal at the drive end of last switch tube at the low voltage end, greatly save drive transformer and drive circuit, reduce cost, the drive end and the second end of remaining switch tube are connected direct current drive voltage, and are connected in antiparallel diode and resistance between the drive end and the second end, realize that a plurality of switch tubes are connected in series and open simultaneously, realize voltage stability control when shutting down.

[0006] Preferably, one end of the Nth voltage dividing resistor is connected to the first end of the Nth switch tube, and the other end of the Nth voltage dividing resistor is connected to the second end of the Nth switch tube in series with the Nth voltage dividing capacitor. Similarly, one end of the first voltage dividing resistor is connected to the first end of the first switch tube, and the other end of the first voltage dividing resistor is connected to the second end of the first switch tube in series with the first voltage dividing capacitor.

[0007] Preferably, one end of the Nth drive resistor is connected to the positive high voltage input, and the other end of the Nth drive resistor is connected to one end of the N-1th drive resistor. Similarly, the other end of the second drive resistor is connected to one end of the first drive resistor, and the other end of the first drive resistor is connected to ground.

[0008] Preferably, N is 3, and the input circuit comprises switch tubes Q1-Q3, voltage dividing resistors R5-R7, voltage dividing capacitors C2-C4, drive resistors R2-R4, diodes D3 and D5, voltage stabilizing diodes Z2 and Z3, and protection resistors R8 and R9. The first end of the switch tube Q1 is connected to the non-polar end of the primary side of the transformer T1, the second end of the switch tube Q1 is connected to the first end of the switch tube Q2, the second end of the switch tube Q2 is connected to the first end of the switch tube Q3, the second end of the switch tube Q3 is connected to ground, one end of the voltage dividing resistor R7 is connected to the first end of the switch tube Q1, the other end of the voltage dividing resistor R7 is connected to the second end of the switch tube Q1 in series with the voltage dividing capacitor C2, one end of the voltage dividing resistor R6 is connected to the first end of the switch tube Q2, the other end of the voltage dividing resistor R6 is connected to the second end of the switch tube Q2 in series with the voltage dividing capacitor C3, one end of the voltage dividing resistor R5 is connected to the first end of the switch tube Q3, the other end of the voltage dividing resistor R5 is connected to the second end of the switch tube Q3 in series with the voltage dividing capacitor C4, one end of the drive resistor R2 is connected to the positive high voltage input, the other end of the drive resistor R2 is connected to one end of the drive resistor R3, the other end of the drive resistor R3 is connected to one end of the drive resistor R4, the other end of the drive resistor R4 is connected to ground, the connection point between the drive resistor R2 and the drive resistor R3 is connected to the drive end of the switch tube Q1, the connection point between the drive resistor R3 and the drive resistor R4 is connected to the drive end of the switch tube Q2, the cathode of the diode D3 is connected to the drive end of the switch tube Q1, the anode of the diode D3 is connected to the second end of the switch tube Q1, the cathode of the diode D5 is connected to the drive end of the switch tube Q2, the anode of the diode D5 is connected to the second end of the switch tube Q2, the cathode of the voltage stabilizing diode Z2 is connected to the drive end of the switch tube Q1, the anode of the voltage stabilizing diode Z2 is connected to the second end of the switch tube Q1, the cathode of the voltage stabilizing diode Z3 is connected to the drive end of the switch tube Q2, the anode of the voltage stabilizing diode Z3 is connected to the second end of the switch tube Q2, the protection resistor R8 is connected in parallel across the voltage stabilizing diode Z2, the protection resistor R9 is connected in parallel across the voltage stabilizing diode Z3, the drive signal is input to the drive end of the switch tube Q3, and the drive ends of the switch tubes Q1 and Q2 are respectively connected to the direct current drive voltage.

[0009] Preferably, the input circuit further comprises resistance R10, resistance R11, diode D4 and diode D6, the resistance R10 is connected between the driving end of the switch tube Q3 and the second end, one end of the resistance R11 is connected with the direct current driving voltage, the other end of the resistance R11 is connected with the anode of the diode D4, the cathode of the diode D4 is connected with the driving end of the switch tube Q1, the anode of the diode D6 is connected with the direct current driving voltage, and the cathode of the diode D6 is connected with the driving end of the switch tube Q2.

[0010] Preferably, the input circuit further comprises resistance R1 and diode D1, one end of the resistance R1 is connected with the same end of the primary side of the transformer T1, the other end of the resistance R1 is connected with the cathode of the diode D1, and the anode of the diode D1 is connected with the different end of the primary side of the transformer T1.

[0011] Preferably, the input circuit further comprises resistance R12, capacitor C5, diode D9 and voltage stabilizing diode Z1, one end of the resistance R12 is connected with the same end of the primary side of the transformer T1, the other end of the resistance R12 is connected with the positive plate of the capacitor C5, the cathode of the diode D9 and the cathode of the voltage stabilizing diode Z1 respectively and connected with the direct current driving voltage, the anode of the diode D9 is connected with the different end of the other primary side of the transformer T1, the negative plate of the capacitor C5, the anode of the voltage stabilizing diode Z1 and the same end of the other primary side of the transformer T1 are connected and grounded.

[0012] Preferably, the output circuit of the secondary side of the transformer T1 comprises capacitor C1 and diode D2, the anode of the diode D2 is connected with the different end of the secondary side of the transformer T1, the cathode of the diode D2 is connected with the positive plate of the capacitor C1, and the negative plate of the capacitor C1 is connected with the same end of the secondary side of the transformer T1.

[0013] Preferably, the capacitance of the voltage dividing capacitor is much larger than the parasitic capacitance between the drain and the source of the switch tube.

[0014] Preferably, the switch tube is a power MOS tube, the diode D3 and the diode D5 are fast recovery diodes, the resistance values of the N driving resistances are the same, and the capacitances of the N voltage dividing capacitors are the same.

[0015] The utility model discloses a power supply circuit, which has the advantages that:

[0016] (1) The high-voltage flyback power supply circuit of the utility model, the transformer main winding adopts single winding, the process is simple, the reliability is increased, a plurality of switching tubes are connected in series at the low voltage end, a voltage dividing capacitor and a voltage dividing resistor are connected in parallel between the first end and the second end of each switching tube, only a driving signal needs to be input at the driving end of the last switching tube at the low voltage end, the driving transformer and the driving circuit are greatly saved, the cost is reduced, the driving end and the second end of the remaining switching tubes are connected with a direct current driving voltage, and a diode and a resistor are connected in antiparallel between the driving end and the second end to realize the simultaneous opening of the plurality of switching tubes in series and the voltage stable control when the switching tubes are turned off.

[0017] (2) The high-voltage flyback power supply circuit of the utility model adopts single-path driving, compared with multi-path driving, the failure rate can be greatly reduced.

[0018] (3) The utility model connects a voltage dividing resistor and a voltage dividing capacitor in parallel between the first end and the second end of each switching tube, can absorb the voltage peak caused by the switching tube turning off, and the voltage dividing resistor and the voltage dividing capacitor in series can limit the discharge current of the voltage dividing capacitor when the switching tube is turned on, thereby protecting the circuit.

[0019] (4) The utility model connects a voltage stabilizing diode in parallel between the gate and the source of the switching tube, can make the gate voltage of the switching tube work in a safe voltage range, because there is a gate-source capacitor in the gate of the switching tube, the protection resistor provides a discharge loop for the gate-source capacitor, there is also a capacitor Cgd between the drain and the gate of the switching tube, before the switching tube is turned on, the high voltage of the drain may be reversed to the gate through the capacitor Cgd, causing damage to the switching tube, by setting the protection resistor, a discharge loop can be provided to release the voltage, thereby protecting the switching tube from being punctured.

[0020] (5) The utility model sets the capacitance of the voltage dividing capacitor to be much larger than the parasitic capacitance between the drain and the source of the switching tube, so that the parasitic capacitance between the drain and the source of the switching tube is relatively small, when the switching tube Q3 is turned off, the voltage between the drain and the source of the switching tube Q3 exceeds 1 / 3U in , the diode D5 is turned on, the diode D5 has a forward conduction time, because the voltage dividing capacitor is large, the voltage change rate between the drain and the source of the switching tube is small, the voltage peak is small, and after the switching tube is turned off, the parasitic capacitance of the switching tube has differences, the parallel connection of the large voltage dividing capacitor can better realize voltage equalization, and the problem that the transformer and the parasitic parameters of the power tube are inconsistent in the prior art can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a circuit diagram of the prior art high-voltage flyback power supply in which the transformer main winding adopts multiple series connections;

[0022] Figure 2The circuit diagram of the high-voltage flyback power supply circuit is provided for the embodiments of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the technical scheme of the present application is described clearly and completely below in connection with specific embodiments and with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0024] The embodiment provides a high-voltage flyback power supply circuit, which comprises a transformer T1, an input circuit arranged at a primary side of the transformer T1 and an output circuit arranged at a secondary side of the transformer T1, the input circuit comprises N switch tubes, N voltage division resistors, N voltage division capacitors, N driving resistors, N-1 diodes, N-1 voltage stabilizing diodes and N-1 protection resistors, the N switch tubes are connected in series between opposite-phase terminals of the primary side of the transformer T1 and the ground in sequence, wherein a first end of the Nth switch tube is connected to the opposite-phase terminal of the primary side of the transformer T1, a second end of the Nth switch tube is connected to a first end of the N-1th switch tube, a second end of the N-1th switch tube is connected to a first end of the N-2th switch tube, a second end of the N-2th switch tube is connected to a first end of the N-3th switch tube, and so on, a second end of the second switch tube is connected to a first end of the first switch tube, and a second end of the first switch tube is connected to the ground, the voltage division resistors and the voltage division capacitors are connected between the first ends and the second ends of the N switch tubes in series and one-to-one correspondence, wherein one end of the Nth voltage division resistor is connected to the first end of the Nth switch tube, the other end of the Nth voltage division resistor is connected to the second end of the Nth switch tube after being connected to the Nth voltage division capacitor in series, one end of the N-1th voltage division resistor is connected to the first end of the N-1th switch tube, the other end of the N-1th voltage division resistor is connected to the second end of the N-1th switch tube after being connected to the N-1th voltage division capacitor in series, and so on, one end of the first voltage division resistor is connected to the first end of the first switch tube, and the other end of the first voltage division resistor is connected to the second end of the first switch tube after being connected to the first voltage division capacitor in series, the N driving resistors are connected in series between a high-voltage input positive electrode and the ground in sequence, wherein one end of the Nth driving resistor is connected to the high-voltage input positive electrode, the other end of the Nth driving resistor is connected to one end of the N-1th driving resistor, and so on, the other end of the second driving resistor is connected to one end of the first driving resistor, and the other end of the first driving resistor is connected to the ground, a connection point between the Nth driving resistor and the N-1th driving resistor is connected to a driving end of the Nth switch tube, a connection point between the N-1th driving resistor and the N-1th driving resistor is connected to a driving end of the N-1th switch tube, and so on, a connection point between the second driving resistor and the first driving resistor is connected to a driving end of the first switch tube, the N-1 diodes are connected between the driving ends of the Nth switch tube to the second switch tube and the second ends of the Nth switch tube to the second switch tube in one-to-one correspondence, wherein a cathode of the Nth diode is connected to the driving end of the Nth switch tube, an anode of the Nth diode is connected to the second end of the Nth switch tube, a cathode of the N-1th diode is connected to the driving end of the N-1th switch tube, and an anode of the N-1th diode is connected to the second end of the N-1th switch tube, and so on, a cathode of the first diode is connected to the driving end of the second switch tube, and an anode of the first diode is connected to the second end of the second switch tube.N-1 voltage stabilizing diodes are connected between the driving end of the Nth switch tube to the driving end of the second switch tube and the second end of the Nth switch tube to the second end of the second switch tube in one-to-one correspondence respectively, wherein the cathode of the Nth voltage stabilizing diode is connected to the driving end of the Nth switch tube, the anode of the Nth voltage stabilizing diode is connected to the second end of the Nth switch tube, the cathode of the N-1 voltage stabilizing diode is connected to the driving end of the N-1 switch tube, the anode of the N-1 voltage stabilizing diode is connected to the second end of the N-1 switch tube, and so on, the cathode of the first voltage stabilizing diode is connected to the driving end of the second switch tube, the anode of the first voltage stabilizing diode is connected to the second end of the second switch tube, N-1 protection resistors are connected in parallel across the N-1 voltage stabilizing diodes in one-to-one correspondence respectively, wherein the N-1 protection resistor is connected in parallel across the anode and the cathode of the N-1 voltage stabilizing diode, the N-2 protection resistor is connected in parallel across the anode and the cathode of the N-2 voltage stabilizing diode, and so on, the first protection resistor is connected in parallel across the anode and the cathode of the first voltage stabilizing diode, only the driving end of the first switch tube inputs the driving signal, and the driving end of the remaining switch tubes is connected to the direct current driving voltage respectively.

[0025] In order to facilitate the description of the high-voltage flyback power supply circuit of the utility model, taking N equal to 3, that is, three switch tubes in series as an example for description:

[0026] As Figure 2As shown, the high-voltage flyback power supply circuit includes a transformer T1, an input circuit arranged at the primary side of the transformer T1, and an output circuit arranged at the secondary side of the transformer T1. The input circuit includes switching tubes Q1, Q2, Q3, voltage dividing resistors R5, R6, R7, voltage dividing capacitors C2, C3, C4, driving resistors R2, R3, R4, diodes D3, D5, voltage stabilizing diodes Z2, Z3, protection resistors R8, R9, a first end of the switching tube Q1 is connected to the heteronym end of the primary side of the transformer T1, a second end of the switching tube Q1 is connected to a first end of the switching tube Q2, a second end of the switching tube Q2 is connected to a first end of the switching tube Q3, a second end of the switching tube Q3 is grounded, one end of the voltage dividing resistor R7 is connected to the first end of the switching tube Q1, the other end of the voltage dividing resistor R7 is connected to the second end of the switching tube Q1 in series with the voltage dividing capacitor C2, one end of the voltage dividing resistor R6 is connected to the first end of the switching tube Q2, the other end of the voltage dividing resistor R6 is connected to the second end of the switching tube Q2 in series with the voltage dividing capacitor C3, one end of the voltage dividing resistor R5 is connected to the first end of the switching tube Q3, the other end of the voltage dividing resistor R5 is connected to the second end of the switching tube Q3 in series with the voltage dividing capacitor C4, one end of the driving resistor R2 is connected to the positive pole of the high-voltage input, the other end of the driving resistor R2 is connected to one end of the driving resistor R3, the other end of the driving resistor R3 is connected to one end of the driving resistor R4, the other end of the driving resistor R4 is grounded, the connection point between the driving resistor R2 and the driving resistor R3 is connected to the driving end of the switching tube Q1, the connection point between the driving resistor R3 and the driving resistor R4 is connected to the driving end of the switching tube Q2, the cathode of the diode D3 is connected to the driving end of the switching tube Q1, the anode of the diode D3 is connected to the second end of the switching tube Q1, the cathode of the diode D5 is connected to the driving end of the switching tube Q2, the anode of the diode D5 is connected to the second end of the switching tube Q2, the cathode of the voltage stabilizing diode Z2 is connected to the driving end of the switching tube Q1, the anode of the voltage stabilizing diode Z2 is connected to the second end of the switching tube Q1, the cathode of the voltage stabilizing diode Z3 is connected to the driving end of the switching tube Q2, the anode of the voltage stabilizing diode Z3 is connected to the second end of the switching tube Q2, the protection resistor R8 is connected in parallel across the voltage stabilizing diode Z2, the protection resistor R9 is connected in parallel across the voltage stabilizing diode Z3, the driving end of the switching tube Q3 is inputted with a driving signal, and the driving ends of the switching tubes Q1, Q2 are respectively connected to a direct-current driving voltage.

[0027] The utility model discloses parallel connection voltage dividing resistance and voltage dividing capacitor between the first end and the second end of each switch tube, can absorb the voltage peak caused by switch tube turn-off, voltage dividing resistance and voltage dividing capacitor series connection can limit the discharge current of voltage dividing capacitor when switch tube conduction, protection circuit. Through parallel connection zener diode between the gate and the source of switch tube, can make the gate voltage of switch tube work in the safe voltage range, because the gate of switch tube exists gate-source capacitance, protection resistance provides discharge loop for gate-source capacitance, the drain and the gate of switch tube also exist capacitor Cgd, before switch tube does not conduct, the high voltage of drain can be through capacitor Cgd and pour back to the gate, lead to switch tube damage, through setting protection resistance, can provide a discharge loop and play the release effect, protect switch tube not to be punctured.

[0028] The input circuit further includes resistance R1, resistance R10, resistance R11, diode D1, diode D4, diode D6, one end of resistance R1 is connected with the same end of the primary side of transformer T1, the other end of resistance R1 is connected with the cathode of diode D1, the anode of diode D1 is connected with the different end of the primary side of transformer T1, resistance R10 is connected between the driving end and the second end of switch tube Q3, one end of resistance R11 is connected with direct current driving voltage, the other end of resistance R11 is connected with the anode of diode D4, the cathode of diode D4 is connected with the driving end of switch tube Q1, the anode of diode D6 is connected with direct current driving voltage, the cathode of diode D6 is connected with the driving end of switch tube Q2.

[0029] The input circuit further includes resistance R12, capacitor C5, diode D9, zener diode Z1, one end of resistance R12 is connected with the same end of the primary side of transformer T1, the other end of resistance R12 is connected with the positive plate of capacitor C5, the cathode of diode D9 and the cathode of zener diode Z1 respectively and connected with direct current driving voltage, the anode of diode D9 is connected with the different end of the other primary side of transformer T1, the negative plate of capacitor C5, the anode of zener diode Z1 and the same end of the other primary side of transformer T1 are connected and grounded, in the instant of electrification, high voltage HV charges capacitor C5 through resistance R12, zener diode Z1 provides required starting voltage VDD1 for driving and control chip, when transformer T1 works, after switch tube turn-off, the fifth pin and the sixth pin of transformer T generate voltage and charge capacitor C5 to maintain voltage VDD1, play the role of auxiliary power supply.

[0030] The output circuit of the secondary side of transformer T1 includes capacitor C1 and diode D2, the anode of diode D2 is connected with the different end of the secondary side of transformer T1, the cathode of diode D2 is connected with the positive plate of capacitor C1, the negative plate of capacitor C1 is connected with the same end of the secondary side of transformer T1.

[0031] The switch tubes Q1, Q2 and Q3 are power MOS tubes, the first end of the switch tube is a drain, the second end is a source, the driving end is a gate, the model is IMBF170R1K0M1, the models of the voltage dividing capacitors C2, C3 and C4 are the same, the capacitance of the voltage dividing capacitors C2, C3 and C4 is far greater than the parasitic capacitance between the drain and the source of the switch tube Q1, Q2 and Q3, so that the parasitic capacitance between the drain and the source of the switch tube is small, the voltage between the drain and the source of the switch tube Q3 exceeds 1 / 3Uin at the moment when the switch tube Q3 is turned off, the diode D5 is turned on, the diode D5 has a forward conduction time, due to the large voltage dividing capacitor, the voltage change rate between the drain and the source of the switch tube is small, and the voltage peak is small, and after the switch tube is turned off, the parasitic capacitance of the switch tube has a difference, and the parallel large voltage dividing capacitor can better realize voltage sharing, and can solve the problem that the transformer and the parasitic parameters of the power tube are inconsistent in the prior art, so that the voltage sharing is not easy to realize. The resistance values of the driving resistors R2, R3 and R4 are the same, the diode D3 and the diode D5 are fast recovery diodes, and the models are the same, and the voltage stabilizing diodes Z2 and Z3 are both 1W15V voltage stabilizing tubes.

[0032] The working principle of the high-voltage flyback power supply circuit of the utility model will be described by taking the case that N is equal to 3, that is, three switch tubes are connected in series, the voltage of the high-voltage input is U in , and the cathode voltages of the diodes D3 and D5 are 2 / 3U in and 1 / 3U in , respectively. When the PWM control signal is at a high level, the voltage low-end switch tube Q3 is turned on, and when the control signal is at a low level, the voltage low-end switch tube Q3 is turned off.

[0033] When the PWM control signal is at a high level, the switch tube Q3 is turned on, the voltage dividing capacitor C4 is discharged through the voltage dividing resistor R5, the voltage between the drain and the source of the switch tube Q3 is lower than 1 / 3U in , the voltage stabilizing diode Z3 and the protection resistor R9 have current flowing through the switch tube Q3, the voltage stabilizing diode Z3 clamps the voltage between the gate and the source of the switch tube Q2 to the gate voltage of the completely turned-on switch tube Q2, the switch tube Q2 starts to be turned on, the voltage dividing capacitor C3 is discharged through the voltage dividing resistor R6, and when the voltage from the drain of the switch tube Q2 to the input ground is less than 2 / 3U inAt this time, current flows through Zener diode Z2 and protection resistor R8. Zener diode Z2 clamps the voltage between the drain and source of switching transistor Q1 at the gate voltage required for full conduction of switching transistor Q1, and switching transistor Q1 begins to conduct. During the turn-on process of switching transistors Q1, Q2, and Q3, the voltage between the drain and source is effectively controlled. After switching transistors Q1, Q2, and Q3 are fully turned on, the PWM signal provides the gate voltage required for switching transistor Q3, and the DC drive voltage VDD1 provides the gate voltage required for switching transistors Q1 and Q2. The high-voltage input voltage U... in The circuit is formed by the primary side of transformer T1 and switching transistors Q1, Q2, and Q3, with energy stored on the primary side of transformer T1. When the PWM control signal is low, switching transistor Q3 is turned off, and the high voltage input charges the voltage dividing capacitor C4 through the voltage dividing resistor R5. When the voltage between the drain and source of switching transistor Q3 rises above 1 / 3U... in With diode D5 forward-biased, the voltage between the drain and source of switching transistor Q3 is clamped at 1 / 3U. in At this time, diode D6 is cut off, the voltage between the gate and source of switching transistor Q2 is 0V, switching transistor Q2 is turned off, and the high voltage input charges the voltage dividing capacitor C3 through the voltage dividing resistor R6. The voltage between the drain and source of switching transistor Q2 is clamped at 2 / 3U. in With diode D3 forward-biased and diode D4 cut off, the voltage between the gate and source of switching transistor Q1 is zero, so Q1 is turned off, and the voltage divider capacitor C2 charges. With switching transistors Q1, Q2, and Q3 all turned off, the voltage between the drain and source of switching transistors Q1 and Q2 is clamped at 1 / 3U. in The voltage between the drain and source of the switching transistor Q3 is 1 / 3U. in The sum of the voltage between the drain and source of the switching transistor Q1 and the reflected voltage of the transformer secondary winding is slightly greater than 1 / 3U. in The secondary winding of transformer T1 releases energy to supply power to the load. The secondary reflected voltage of the transformer refers to the voltage reflected from the transformer's primary winding when the primary-side switch is turned off, the secondary winding releases energy, the secondary diode turns on, and the voltage across the transformer is reflected back to the primary winding.

[0034] In the high-voltage flyback power supply circuit of this invention, the main winding of the transformer adopts a single winding, which simplifies the process and increases reliability. Multiple switching transistors are connected in series at the low voltage end, and a voltage-dividing capacitor and a voltage-dividing resistor are connected in parallel between the first and second terminals of each switching transistor. Only the drive signal needs to be input at the drive terminal of the last switching transistor at the low voltage end, which greatly saves the drive transformer and drive circuit, reduces costs, and the single-path drive has a lower failure rate than the multi-path drive. The drive terminals and second terminals of the remaining switching transistors are connected to the DC drive voltage, and a diode and a resistor are connected in anti-parallel between the drive terminals and the second terminals to enable multiple switching transistors to be connected in series and turned on simultaneously. Voltage stabilization control is achieved when the transistors are turned off.

[0035] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features therein can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high voltage flyback power supply circuit, characterized by: The input circuit arranged at the primary side of the transformer T1 and the output circuit arranged at the secondary side of the transformer T1, the input circuit comprising N switch tubes, N voltage dividing resistors, N voltage dividing capacitors, N driving resistors, N-1 diodes, N-1 voltage stabilizing diodes, N-1 protection resistors, the N switch tubes being connected in series between the opposite name end of the primary side of the transformer T1 and the ground, wherein the first end of the Nth switch tube is connected to the opposite name end of the primary side of the transformer T1, the second end of the Nth switch tube is connected to the first end of the N-1th switch tube, and so on, the second end of the second switch tube is connected to the first end of the first switch tube, and the second end of the first switch tube is connected to the ground, the voltage dividing resistors and the voltage dividing capacitors are connected in series between the first end and the second end of the N switch tubes in one-to-one correspondence, the N driving resistors are connected in series between the high-voltage input positive pole and the ground, the connection point between the Nth driving resistor and the N-1th driving resistor is connected to the driving end of the Nth switch tube, the N-1 diodes are connected in one-to-one correspondence between the driving end of the Nth switch tube to the driving end of the second switch tube and the second end of the Nth switch tube to the second end of the second switch tube, wherein the cathode and the anode of the Nth diode are connected to the driving end and the second end of the Nth switch tube, and so on, the cathode and the anode of the first diode are connected to the driving end and the second end of the second switch tube, the N-1 voltage stabilizing diodes are connected in one-to-one correspondence between the driving end of the Nth switch tube to the driving end of the second switch tube and the second end of the Nth switch tube to the second end of the second switch tube, wherein the cathode and the anode of the Nth voltage stabilizing diode are connected to the driving end and the second end of the Nth switch tube, and so on, the cathode and the anode of the first voltage stabilizing diode are connected to the driving end and the second end of the second switch tube, the N-1 protection resistors are connected in parallel across the N-1 voltage stabilizing diodes in one-to-one correspondence, the driving end of the first switch tube is inputted with a driving signal, the driving ends of the remaining switch tubes are connected to a direct current driving voltage respectively, and N is a positive integer greater than or equal to 2.

2. The high-voltage flyback power supply circuit of claim 1, wherein: One end of the Nth voltage dividing resistor is connected to the first end of the Nth switch tube, the other end of the Nth voltage dividing resistor is connected to the second end of the Nth switch tube in series with the Nth voltage dividing capacitor, and so on, one end of the first voltage dividing resistor is connected to the first end of the first switch tube, and the other end of the first voltage dividing resistor is connected to the second end of the first switch tube in series with the first voltage dividing capacitor.

3. The high-voltage flyback power supply circuit of claim 1, wherein: One end of the Nth driving resistor is connected to the high-voltage input positive pole, the other end of the Nth driving resistor is connected to one end of the N-1th driving resistor, and so on, the other end of the second driving resistor is connected to one end of the first driving resistor, and the other end of the first driving resistor is connected to the ground.

4. The high-voltage flyback power supply circuit of claim 1, wherein: N is 3, the input circuit includes switch tube Q1-Q3, voltage dividing resistor R5-R7, voltage dividing capacitor C2-C4, drive resistor R2-R4, diode D3, diode D5, voltage stabilizing diode Z2-Z3, protection resistor R8-R9, the first end of switch tube Q1 is connected with the opposite end of the primary side of transformer T1, the second end of switch tube Q1 is connected with the first end of switch tube Q2, the second end of switch tube Q2 is connected with the first end of switch tube Q3, the second end of switch tube Q3 is grounded, one end of voltage dividing resistor R7 is connected with the first end of switch tube Q1, voltage dividing resistor R7 is connected with voltage dividing capacitor C2 in series and then connected with the second end of switch tube Q1, one end of voltage dividing resistor R6 is connected with the first end of switch tube Q2, voltage dividing resistor R6 is connected with voltage dividing capacitor C3 in series and then connected with the second end of switch tube Q2, one end of voltage dividing resistor R5 is connected with the first end of switch tube Q3, voltage dividing resistor R5 is connected with voltage dividing capacitor C4 in series and then connected with the second end of switch tube Q3, one end of drive resistor R2 is connected with the positive pole of high voltage input, the other end of drive resistor R2 is connected with one end of drive resistor R3, the other end of drive resistor R3 is connected with one end of drive resistor R4, the other end of drive resistor R4 is grounded, the connecting point between drive resistor R2 and drive resistor R3 is connected with the drive end of switch tube Q1, the connecting point between drive resistor R3 and drive resistor R4 is connected with the drive end of switch tube Q2, the cathode of diode D3 is connected with the drive end of switch tube Q1, the anode of diode D3 is connected with the second end of switch tube Q1, the cathode of diode D5 is connected with the drive end of switch tube Q2, the anode of diode D5 is connected with the second end of switch tube Q2, the cathode of voltage stabilizing diode Z2 is connected with the drive end of switch tube Q1, the anode of voltage stabilizing diode Z2 is connected with the second end of switch tube Q1, the cathode of voltage stabilizing diode Z3 is connected with the drive end of switch tube Q2, the anode of voltage stabilizing diode Z3 is connected with the second end of switch tube Q2, protection resistor R8 is connected in parallel with voltage stabilizing diode Z2, protection resistor R9 is connected in parallel with voltage stabilizing diode Z3, the drive end of switch tube Q3 is inputted with drive signal, the drive ends of switch tube Q1 and Q2 are connected with direct current drive voltage respectively.

5. The high-voltage flyback power supply circuit of claim 1, wherein: The input circuit further comprises resistor R10, resistor R11, diode D4, diode D6, resistor R10 is connected between the drive end and the second end of switch tube Q3, one end of resistor R11 is connected with direct current drive voltage, the other end of resistor R11 is connected with the anode of diode D4, the cathode of diode D4 is connected with the drive end of switch tube Q1, the anode of diode D6 is connected with direct current drive voltage, the cathode of diode D6 is connected with the drive end of switch tube Q2.

6. The high-voltage flyback power supply circuit of claim 1, wherein: The input circuit further comprises resistor R1, diode D1, one end of resistor R1 is connected with the same end of the primary side of transformer T1, the other end of resistor R1 is connected with the cathode of diode D1, the anode of diode D1 is connected with the opposite end of the primary side of transformer T1.

7. The high-voltage flyback power supply circuit of claim 1, wherein: The input circuit further comprises a resistor R12, a capacitor C5, a diode D9 and a stabilizing diode Z1. One end of the resistor R12 is connected to the same end of the primary side of the transformer T1, the other end of the resistor R12 is connected to the positive plate of the capacitor C5, the cathode of the diode D9 and the cathode of the stabilizing diode Z1 respectively and connected to a direct current driving voltage, the anode of the diode D9 is connected to the different end of the other primary side of the transformer T1, the negative plate of the capacitor C5, the anode of the stabilizing diode Z1 and the same end of the other primary side of the transformer T1 are connected to the ground.

8. The high-voltage flyback power supply circuit of claim 1, wherein: The output circuit of the secondary side of the transformer T1 comprises a capacitor C1 and a diode D2. The anode of the diode D2 is connected to the different end of the secondary side of the transformer T1, the cathode of the diode D2 is connected to the positive plate of the capacitor C1, and the negative plate of the capacitor C1 is connected to the same end of the secondary side of the transformer T1.

9. The high-voltage flyback power supply circuit according to claim 1 or 4, characterized in that: The capacitance of the voltage dividing capacitor is much larger than the parasitic capacitance between the drain and the source of the switch tube.

10. The high-voltage flyback power supply circuit according to claim 1 or 4, characterized in that: The switch tube is a power MOS tube, the diode D3 and the diode D5 are fast recovery diodes, the resistance of the N driving resistors is the same, and the capacitance of the N voltage dividing capacitors is the same.