A self-powered drive circuit applied to a switching power supply circuit
By introducing a self-powered drive circuit into the switching power supply circuit, and using the primary inductor current for self-powering, the problem of voltage instability in traditional self-powered methods when the load changes is solved, and a stable power supply effect without the need for additional energy replenishment is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI ORIENT CHIP TECH CO LTD
- Filing Date
- 2025-07-10
- Publication Date
- 2026-07-10
AI Technical Summary
In traditional self-powered circuits, the energy storage circuit voltage is insufficient when the load suddenly increases, resulting in unstable load output voltage and requiring additional energy consumption at the output terminal to replenish the power.
A self-powered drive circuit is adopted, including a current drive switching circuit, a voltage clamping circuit, a field-effect transistor and a triode. It uses the primary-side inductor current for self-powering, reducing the external circuitry of the transformer. The control chip detects load changes and adjusts the conduction time to achieve self-powering.
This improved the stability of the transformer output voltage, reduced the use of auxiliary windings, and enabled stable power supply without the need for additional energy replenishment.
Smart Images
Figure CN224481629U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of integrated circuit technology, and in particular to a self-powered drive circuit for use in switching power supply circuits. Background Technology
[0002] Traditional self-powered circuits consist of a control chip, a Darlington power transistor, a feedback circuit, an energy storage loop, the primary inductor of a transformer, the secondary inductor of a transformer, and an auxiliary winding. The energy storage circuit is powered by the auxiliary winding. Typically, since energy storage circuits are low-voltage circuits, the auxiliary winding is connected to the secondary inductor at the output terminal, requiring additional energy from the output terminal for replenishment. During a single cycle after startup, if the primary current suddenly increases due to a load surge, the maximum current limit of the primary inductor, coupled with the need for both the load output and the energy storage circuit to maintain voltage levels, can lead to insufficient voltage in the energy storage circuit and unstable output voltage for the load. Utility Model Content
[0003] The purpose of this application is to provide a self-powered drive circuit for use in switching power supply circuits, which reduces the external circuitry of the transformer and improves the stability of the transformer output voltage.
[0004] To achieve the above objectives, this application provides the following solution:
[0005] This application provides a self-powered drive circuit for use in a switching power supply circuit. The switching power supply circuit includes a primary inductance of a transformer, a secondary inductance of a transformer, a resistor, and a Darlington power transistor. One end of the primary inductance and one end of the resistor are both connected to the first end of the Darlington power transistor. The self-powered drive circuit for use in the switching power supply circuit includes: a current drive switching circuit, a voltage clamping circuit, a first field-effect transistor, a second field-effect transistor, and a first transistor.
[0006] The output terminal of the current drive switching circuit is connected to the second terminal of the Darlington power transistor, and the first and second input terminals of the current drive switching circuit are both connected to the control chip.
[0007] The first terminal of the voltage clamping circuit is connected to the second terminal of the Darlington power transistor, and the second terminal of the voltage clamping circuit is grounded through an energy storage circuit.
[0008] The gate of the first field-effect transistor is connected to the control chip, the drain of the first field-effect transistor is connected to the third terminal of the Darlington power transistor, and the source of the first field-effect transistor is grounded.
[0009] The gate of the second field-effect transistor is connected to the control chip, the drain of the second field-effect transistor is connected to the fourth terminal of the Darlington power transistor, and the source of the second field-effect transistor is grounded.
[0010] The base and collector of the first transistor are both connected to the fourth terminal of the Darlington power transistor, and the emitter of the first transistor is grounded through the energy storage circuit.
[0011] In one embodiment, the current-driven switching circuit includes: a comparator, a NOR gate, a third field-effect transistor, a fourth field-effect transistor, a fifth field-effect transistor, a current mirror circuit, a first current source, and a second current source.
[0012] The positive terminal of the comparator is connected to the voltage of the energy storage circuit, the negative terminal of the comparator is connected to the reference voltage, and the output terminal of the comparator is connected to the first input terminal of the NOR gate.
[0013] The second input terminal of the NOR gate and the gate of the fourth field-effect transistor serve as the first input terminal of the current-driven switching circuit, and the output terminal of the NOR gate is connected to the gate of the third field-effect transistor.
[0014] The drain of the third field-effect transistor is connected to the input terminal of the current mirror circuit, and the source of the third field-effect transistor is grounded through the first current source.
[0015] The drain of the fourth field-effect transistor is connected to the input terminal of the current mirror circuit, and the source of the fourth field-effect transistor is grounded through the second current source.
[0016] The output terminal of the current mirror circuit serves as the output terminal of the current drive switching circuit. Both the output terminal of the current mirror circuit and the drain of the fifth field-effect transistor are connected to the second terminal of the Darlington power transistor.
[0017] The gate of the fifth field-effect transistor serves as the second input terminal of the current-driven switching circuit.
[0018] In one embodiment, the current mirror circuit includes: a sixth field-effect transistor and a seventh field-effect transistor;
[0019] The gate of the sixth field-effect transistor is connected to the drain of the sixth field-effect transistor, the gate of the seventh field-effect transistor, the drain of the third field-effect transistor, and the drain of the fourth field-effect transistor, respectively. The source of the sixth field-effect transistor is connected to the source of the seventh field-effect transistor, and the drain of the seventh field-effect transistor is connected to the second terminal of the Darlington power transistor.
[0020] In one embodiment, the voltage clamping circuit includes: a second transistor, a third transistor, a fourth transistor, and a fifth transistor;
[0021] The base and collector of the second transistor are short-circuited to serve as the first terminal of the voltage clamping circuit and are connected to the second terminal of the Darlington power transistor; the base and collector of the third transistor are short-circuited and are connected to the emitter of the second transistor; the base and collector of the fourth transistor are short-circuited and are connected to the emitter of the third transistor; the base and collector of the fifth transistor are short-circuited and are connected to the emitter of the fourth transistor, the emitter of the fifth transistor serves as the second terminal of the voltage clamping circuit, and the emitter of the fifth transistor is grounded through the energy storage circuit.
[0022] In one embodiment, the Darlington power transistor includes: a sixth transistor and a seventh transistor;
[0023] The collector of the sixth transistor is connected to the collector of the seventh transistor to form the first terminal of the Darlington power transistor. The base of the sixth transistor forms the second terminal of the Darlington power transistor. The emitter of the sixth transistor is connected to the gate of the seventh transistor to form the third terminal of the Darlington power transistor. The emitter of the seventh transistor forms the fourth terminal of the Darlington power transistor.
[0024] In one embodiment, the energy storage circuit is a capacitor;
[0025] One end of the capacitor is connected to the emitter of the fifth transistor and the emitter of the first transistor, and the other end of the capacitor is grounded.
[0026] In one embodiment, the operation of the self-powered drive circuit applied to the switching power supply circuit includes:
[0027] When the first signal of the control chip output acquired by the first input terminal of the current drive switching circuit is high, the third field-effect transistor is turned off and the fourth field-effect transistor is turned on. The current of the second current source enters the second terminal of the Darlington power transistor through the current mirror circuit. The transformer is in normal working current drive mode.
[0028] When the first signal from the control chip acquired at the first input terminal of the current-driven switching circuit is low and the voltage of the energy storage circuit is lower than the reference voltage, the comparator outputs a low level, the NOR gate outputs a high level, the third field-effect transistor is turned on, the fourth field-effect transistor is turned off, the current from the first current source enters the second terminal of the Darlington power transistor through the current mirror circuit, and the transformer operates in a self-powered current-driven state.
[0029] In one embodiment, the operation process of the transformer in the self-powered current driven state includes:
[0030] When the second signal output by the control chip acquired by the second field-effect transistor is high, and the third signal output by the control chip acquired by the first field-effect transistor and the fourth signal output by the control chip acquired by the fifth field-effect transistor are both low, the control chip and the resistor jointly drive the circuit to ground through the Darlington power transistor and the second field-effect transistor, and the transformer enters the inductor magnetization state.
[0031] When the second signal from the control chip acquired by the second field-effect transistor is low, and the third signal from the control chip acquired by the first field-effect transistor and the fourth signal from the control chip acquired by the fifth field-effect transistor are both high, current flows through the fifth field-effect transistor, making the base voltage of the sixth transistor equal to zero, the sixth transistor turns off, the fourth field-effect transistor turns on, discharging the charge at the base of the seventh transistor to prevent overcharging, the transformer enters the inductor demagnetization state, and no current flows through the Darlington power transistor.
[0032] According to the specific embodiments provided in this application, the following technical effects are disclosed:
[0033] This application discloses a self-powered drive circuit for use in switching power supply circuits. The self-powered drive circuit includes: a current-driven switching circuit, a voltage clamping circuit, a first field-effect transistor (FET), a second FET, and a first transistor. The output terminal of the current-driven switching circuit is connected to the second terminal of the Darlington power transistor, and both the first and second input terminals are connected to a control chip. The first terminal of the voltage clamping circuit is connected to the second terminal of the Darlington power transistor, and the second terminal is grounded through an energy storage circuit. The gate of the first FET is connected to the control chip, the drain is connected to the third terminal of the Darlington power transistor, and the source is grounded. The gate of the second FET is connected to the control chip, the drain is connected to the fourth terminal of the Darlington power transistor, and the source is grounded. The base and collector of the first transistor are both connected to the fourth terminal of the Darlington power transistor, and the emitter is grounded through an energy storage circuit. This application, by setting a self-powered drive circuit in the control chip and switching power supply circuit, eliminates the need for auxiliary windings, reduces the need for auxiliary energy storage circuits in the transformer as peripheral circuits, and utilizes the fact that the current of the primary inductor does not affect the voltage at the transformer's output terminal, thereby improving the stability of the transformer's output voltage. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0035] Figure 1 A schematic diagram of a self-powered drive circuit structure applied to a switching power supply circuit is provided in an embodiment of this application;
[0036] Figure 2 This is a schematic diagram of the connection structure of a self-powered drive circuit, a switching power supply circuit, and an energy storage circuit used in switching power supply circuits.
[0037] Figure reference numerals: NOR gate, first field-effect transistor - M1, second field-effect transistor - M2, third field-effect transistor - M3, fourth field-effect transistor - M4, fifth field-effect transistor - M5, sixth field-effect transistor - M6, seventh field-effect transistor - M7, first transistor - Q1, second transistor - Q2, third transistor - Q3, fourth transistor - Q4, fifth transistor - Q5, sixth transistor - Q6, seventh transistor - Q7, resistor - R, capacitor - C, first current source - I1, second current source - I2. Detailed Implementation
[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0039] The purpose of this application is to provide a self-powered drive circuit for use in switching power supply circuits, which aims to reduce the external circuitry of the transformer and improve the stability of the transformer output voltage.
[0040] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0041] In one exemplary embodiment, such as Figure 1 and Figure 2As shown, a self-powered drive circuit for use in a switching power supply circuit is provided, including: the switching power supply circuit includes the primary inductance of a transformer, the secondary inductance of a transformer, a resistor R, and a Darlington power transistor; one end of the primary inductance and one end of the resistor R are both connected to the first end of the Darlington power transistor. The self-powered drive circuit for use in the switching power supply circuit includes: a current drive switching circuit, a voltage clamping circuit, a first field-effect transistor M1, a second field-effect transistor M2, and a first transistor Q1.
[0042] The output of the current-driven switching circuit is connected to the second terminal of the Darlington power transistor, and both the first and second input terminals of the current-driven switching circuit are connected to the control chip.
[0043] The first terminal of the voltage clamping circuit is connected to the second terminal of the Darlington power transistor, and the second terminal of the voltage clamping circuit is grounded through the energy storage circuit.
[0044] The gate of the first field-effect transistor M1 is connected to the control chip, the drain of the first field-effect transistor M1 is connected to the third terminal of the Darlington power transistor, and the source of the first field-effect transistor M1 is grounded.
[0045] The gate of the second field-effect transistor M2 is connected to the control chip, the drain of the second field-effect transistor M2 is connected to the fourth terminal of the Darlington power transistor, and the source of the second field-effect transistor M2 is grounded.
[0046] The base and collector of the first transistor Q1 are both connected to the fourth terminal of the Darlington power transistor, and the emitter of the first transistor Q1 is grounded through the energy storage circuit.
[0047] Specifically, in the switching power supply circuit of this application, the transformer is a dual-winding inductor, with the left side being the primary inductor and the right side being the secondary inductor, which is responsible for supplying power to the actual load.
[0048] As an optional implementation, the current-driven switching circuit includes: a comparator, a NOR gate, a third field-effect transistor M3, a fourth field-effect transistor M4, a fifth field-effect transistor M5, a current mirror circuit, a first current source I1, and a second current source I2.
[0049] The positive terminal of the comparator is connected to the voltage VCC of the energy storage circuit, the negative terminal of the comparator is connected to the reference voltage Vref, and the output terminal of the comparator is connected to the first input terminal of the NOR gate.
[0050] The second input terminal of the NOR gate and the gate of the fourth field-effect transistor M4 serve as the first input terminal of the current-driven switching circuit, and the output terminal of the NOR gate is connected to the gate of the third field-effect transistor M3.
[0051] The drain of the third field-effect transistor M3 is connected to the input terminal of the current mirror circuit, and the source of the third field-effect transistor M3 is grounded through the first current source I1.
[0052] The drain of the fourth field-effect transistor M4 is connected to the input terminal of the current mirror circuit, and the source of the fourth field-effect transistor M4 is grounded through the second current source I2.
[0053] The output of the current mirror circuit serves as the output of the current-driven switching circuit. Both the output of the current mirror circuit and the drain of the fifth field-effect transistor M5 are connected to the second terminal of the Darlington power transistor.
[0054] The gate of the fifth field-effect transistor M5 serves as the second input terminal of the current-driven switching circuit.
[0055] As an alternative implementation, the current mirror circuit includes a sixth field-effect transistor M6 and a seventh field-effect transistor M7.
[0056] The gate of the sixth field-effect transistor M6 is connected to the drain of the sixth field-effect transistor M6, the gate of the seventh field-effect transistor M7, the drain of the third field-effect transistor M3, and the drain of the fourth field-effect transistor M4, respectively. The source of the sixth field-effect transistor M6 is connected to the source of the seventh field-effect transistor M7, and the drain of the seventh field-effect transistor M7 is connected to the second terminal of the Darlington power transistor.
[0057] As an optional implementation, the voltage clamping circuit includes: a second transistor Q2, a third transistor Q3, a fourth transistor Q4, and a fifth transistor Q5.
[0058] The base and collector of the second transistor Q2 are shorted together to serve as the first terminal of the voltage clamping circuit and are connected to the second terminal of the Darlington power transistor. The base and collector of the third transistor Q3 are shorted together and are connected to the emitter of the second transistor Q2. The base and collector of the fourth transistor Q4 are shorted together and are connected to the emitter of the third transistor Q3. The base and collector of the fifth transistor Q5 are shorted together and are connected to the emitter of the fourth transistor Q4. The emitter of the fifth transistor Q5 serves as the second terminal of the voltage clamping circuit and is grounded through the energy storage circuit.
[0059] Specifically, transistors Q2, Q3, Q4, and Q5 are all configured with their bases and collectors shorted and cascaded. Their function is voltage clamping. During the circuit startup phase, the primary inductor provides the mains high voltage. At this time, the current path is that the current in the primary inductor flows through the megaohm-level resistor R to provide charge to the base of transistor Q6. When the base voltage of transistor Q6 is sufficient, since the control chip is not working at this time, the first field-effect transistor M1 and the second field-effect transistor M2 cannot conduct. The current at the base of transistor Q6 is amplified and flows from the first transistor Q1 to capacitor C, gradually accumulating charge until the voltage on C is sufficient to start the control circuit, and the entire circuit begins to work normally. Alternatively, when the base voltage of transistor Q6, the lower end of resistor R, and the drain voltage of the seventh field-effect transistor M7 are about to exceed 4 times Vbe (the voltage between the base and emitter), they conduct and limit the voltage at this position to 4 times Vbe.
[0060] As an alternative implementation, the Darlington power transistors include: a sixth transistor Q6 and a seventh transistor Q7.
[0061] The collector of transistor Q6 is connected to the collector of transistor Q7, which is the seventh transistor, and serves as the first terminal of the Darlington power transistor. The base of transistor Q6 serves as the second terminal of the Darlington power transistor. The emitter of transistor Q6 is connected to the gate of transistor Q7, which is the seventh transistor, and serves as the third terminal of the Darlington power transistor. The emitter of transistor Q7 serves as the fourth terminal of the Darlington power transistor.
[0062] Specifically, transistors Q6 and Q7 form a Darlington power transistor. Both transistors Q6 and Q7 are NPN transistors. The emitter of transistor Q6 is connected to the base of transistor Q7. In actual operation, the base and emitter of transistor Q2 connected to the upper end of V_S2 and the lower end of R are connected to the base of transistor Q6. Charge is injected into transistor Q6, amplified by transistor Q6, and then drives the more powerful transistor Q7.
[0063] As an optional implementation, the energy storage circuit is a capacitor C.
[0064] One end of capacitor C is connected to the emitter of the fifth transistor Q5 and the emitter of the first transistor Q1, and the other end of capacitor C is grounded.
[0065] As an optional implementation, the operation of a self-powered drive circuit applied to a switching power supply circuit includes:
[0066] When the first signal TON from the control chip, acquired at the first input terminal of the current drive switching circuit, is high, the third field-effect transistor M3 is turned off, the fourth field-effect transistor M4 is turned on, and the current from the second current source I2 enters the second terminal of the Darlington power transistor through the current mirror circuit. The transformer operates in normal current drive mode.
[0067] When the first signal TON from the control chip acquired by the first input terminal of the current-driven switching circuit is low, and the voltage VCC of the energy storage circuit is lower than the reference voltage Vref, the comparator outputs a low level, the NOR gate outputs a high level, the third field-effect transistor M3 is turned on, the fourth field-effect transistor M4 is turned off, the current from the first current source I1 enters the second terminal of the Darlington power transistor through the current mirror circuit, and the transformer operates in a self-powered current-driven state.
[0068] As an optional implementation, the transformer's operating mode in a self-powered current-driven state includes the following processes:
[0069] When the second signal V_S1 output by the control chip acquired by the second field-effect transistor M2 is at a high level, and the third signal V_S2 output by the control chip acquired by the first field-effect transistor M1 and the fourth signal DRV output by the control chip acquired by the fifth field-effect transistor M5 are both at a low level, the control chip and the resistor R jointly drive the circuit to ground through the Darlington power transistor and the second field-effect transistor M2, and the transformer enters the inductance magnetization state.
[0070] When the second signal V_S1, acquired by the control chip from the second field-effect transistor M2, is low, and the third signal V_S2, acquired by the control chip from the first field-effect transistor M1, and the fourth signal DRV, acquired by the control chip from the fifth field-effect transistor M5, are both high, current flows through the fifth field-effect transistor M5, causing the base voltage of the sixth transistor Q6 to be zero. The sixth transistor Q6 is turned off, and the fourth field-effect transistor M4 is turned on, discharging the base charge of the seventh transistor Q7 to prevent overcharging. The transformer enters the inductor demagnetization state, and no current flows through the Darlington power transistor.
[0071] This application's feedback loop requires only a single path to the control chip. No additional winding is needed to charge the energy storage circuit to ensure the normal operation of the control chip. The self-powered drive circuit internally utilizes the pre-off time of a single conduction cycle to detect VCC and replenish energy using the primary-side current. Compared to primary-side feedback circuits that require additional windings, this application significantly reduces the auxiliary energy storage circuit while achieving the same functionality, replacing it with the internal self-powered drive circuit. This reduction in external circuitry improves the voltage stability at the output terminal.
[0072] This application achieves self-powered operation of the entire circuit by reducing the auxiliary winding and using a self-powered drive circuit. After the control chip detects that the emitter current of Q7 has reached a preset maximum current value, the self-powered drive circuit detects the voltage VCC of capacitor C. When VCC is insufficient for a preset Vref, the conduction period is extended, thus achieving self-powered operation of the entire circuit. The feedback loop adjusts the conduction time of the control chip by detecting changes in the output load; this part of the circuit does not affect the normal operation of the self-powered drive circuit.
[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0074] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the circuit and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A self-powered drive circuit for use in a switching power supply circuit, the switching power supply circuit comprising a primary inductance of a transformer, a secondary inductance of a transformer, a resistor, and a Darlington power transistor; one end of the primary inductance and one end of the resistor are both connected to the first end of the Darlington power transistor, characterized in that, The self-powered drive circuit applied to the switching power supply circuit includes: a current drive switching circuit, a voltage clamping circuit, a first field-effect transistor, a second field-effect transistor, and a first transistor. The output terminal of the current drive switching circuit is connected to the second terminal of the Darlington power transistor, and the first and second input terminals of the current drive switching circuit are both connected to the control chip. The first terminal of the voltage clamping circuit is connected to the second terminal of the Darlington power transistor, and the second terminal of the voltage clamping circuit is grounded through an energy storage circuit. The gate of the first field-effect transistor is connected to the control chip, the drain of the first field-effect transistor is connected to the third terminal of the Darlington power transistor, and the source of the first field-effect transistor is grounded. The gate of the second field-effect transistor is connected to the control chip, the drain of the second field-effect transistor is connected to the fourth terminal of the Darlington power transistor, and the source of the second field-effect transistor is grounded. The base and collector of the first transistor are both connected to the fourth terminal of the Darlington power transistor, and the emitter of the first transistor is grounded through the energy storage circuit.
2. The self-powered drive circuit applied to a switching power supply circuit according to claim 1, characterized in that, The current-driven switching circuit includes: a comparator, a NOR gate, a third field-effect transistor, a fourth field-effect transistor, a fifth field-effect transistor, a current mirror circuit, a first current source, and a second current source. The positive terminal of the comparator is connected to the voltage of the energy storage circuit, the negative terminal of the comparator is connected to the reference voltage, and the output terminal of the comparator is connected to the first input terminal of the NOR gate. The second input terminal of the NOR gate and the gate of the fourth field-effect transistor serve as the first input terminal of the current-driven switching circuit, and the output terminal of the NOR gate is connected to the gate of the third field-effect transistor. The drain of the third field-effect transistor is connected to the input terminal of the current mirror circuit, and the source of the third field-effect transistor is grounded through the first current source. The drain of the fourth field-effect transistor is connected to the input terminal of the current mirror circuit, and the source of the fourth field-effect transistor is grounded through the second current source. The output terminal of the current mirror circuit serves as the output terminal of the current drive switching circuit. Both the output terminal of the current mirror circuit and the drain of the fifth field-effect transistor are connected to the second terminal of the Darlington power transistor. The gate of the fifth field-effect transistor serves as the second input terminal of the current-driven switching circuit.
3. The self-powered drive circuit applied to a switching power supply circuit according to claim 2, characterized in that, The current mirror circuit includes: a sixth field-effect transistor and a seventh field-effect transistor; The gate of the sixth field-effect transistor is connected to the drain of the sixth field-effect transistor, the gate of the seventh field-effect transistor, the drain of the third field-effect transistor, and the drain of the fourth field-effect transistor, respectively. The source of the sixth field-effect transistor is connected to the source of the seventh field-effect transistor, and the drain of the seventh field-effect transistor is connected to the second terminal of the Darlington power transistor.
4. The self-powered drive circuit applied to a switching power supply circuit according to claim 3, characterized in that, The voltage clamping circuit includes: a second transistor, a third transistor, a fourth transistor, and a fifth transistor; The base and collector of the second transistor are short-circuited to serve as the first terminal of the voltage clamping circuit and are connected to the second terminal of the Darlington power transistor; the base and collector of the third transistor are short-circuited and are connected to the emitter of the second transistor; the base and collector of the fourth transistor are short-circuited and are connected to the emitter of the third transistor; the base and collector of the fifth transistor are short-circuited and are connected to the emitter of the fourth transistor, the emitter of the fifth transistor serves as the second terminal of the voltage clamping circuit, and the emitter of the fifth transistor is grounded through the energy storage circuit.
5. The self-powered drive circuit applied to a switching power supply circuit according to claim 4, characterized in that, The Darlington power transistor includes: a sixth transistor and a seventh transistor; The collector of the sixth transistor is connected to the collector of the seventh transistor to form the first terminal of the Darlington power transistor. The base of the sixth transistor forms the second terminal of the Darlington power transistor. The emitter of the sixth transistor is connected to the gate of the seventh transistor to form the third terminal of the Darlington power transistor. The emitter of the seventh transistor forms the fourth terminal of the Darlington power transistor.
6. The self-powered drive circuit applied to a switching power supply circuit according to claim 5, characterized in that, The energy storage circuit is a capacitor; One end of the capacitor is connected to the emitter of the fifth transistor and the emitter of the first transistor, and the other end of the capacitor is grounded.
7. The self-powered drive circuit applied to a switching power supply circuit according to claim 6, characterized in that, The operation of the self-powered drive circuit applied to the switching power supply circuit includes: When the first signal of the control chip output acquired by the first input terminal of the current drive switching circuit is high, the third field-effect transistor is turned off and the fourth field-effect transistor is turned on. The current of the second current source enters the second terminal of the Darlington power transistor through the current mirror circuit. The transformer is in normal working current drive mode. When the first signal from the control chip acquired at the first input terminal of the current-driven switching circuit is low and the voltage of the energy storage circuit is lower than the reference voltage, the comparator outputs a low level, the NOR gate outputs a high level, the third field-effect transistor is turned on, the fourth field-effect transistor is turned off, the current from the first current source enters the second terminal of the Darlington power transistor through the current mirror circuit, and the transformer operates in a self-powered current-driven state.
8. The self-powered drive circuit applied to a switching power supply circuit according to claim 7, characterized in that, The operating process of a transformer in self-powered current-driven mode includes: When the second signal output by the control chip acquired by the second field-effect transistor is high, and the third signal output by the control chip acquired by the first field-effect transistor and the fourth signal output by the control chip acquired by the fifth field-effect transistor are both low, the control chip and the resistor jointly drive the circuit to ground through the Darlington power transistor and the second field-effect transistor, and the transformer enters the inductor magnetization state. When the second signal from the control chip acquired by the second field-effect transistor is low, and the third signal from the control chip acquired by the first field-effect transistor and the fourth signal from the control chip acquired by the fifth field-effect transistor are both high, current flows through the fifth field-effect transistor, making the base voltage of the sixth transistor equal to zero, the sixth transistor turns off, the fourth field-effect transistor turns on, discharging the charge at the base of the seventh transistor to prevent overcharging, the transformer enters the inductor demagnetization state, and no current flows through the Darlington power transistor.