A power switch tube control circuit for power supply

Abstract

This application belongs to the field of power management technology and discloses a power switch control circuit for a power supply, including: an input signal conditioning unit for receiving an external PWM control signal and outputting first and second drive signals; a first drive branch for providing a low-impedance turn-on path in response to the first drive signal during the turn-on phase of the power switch; a second drive branch for providing a controllable turn-off current path in response to the second drive signal during the turn-off phase of the power switch; an accelerated turn-off unit connected in parallel with the second drive branch for providing a stepwise instantaneous low-impedance turn-off path when the voltage at the control terminal of the power switch is detected to drop below a preset voltage; and an overshoot suppression unit connected between the control terminal of the power switch and ground for suppressing voltage spikes generated by the power switch during the turn-off process. This application can improve the switching speed of the power switch and reduce switching losses.

Description

Technical Field

[0001] This application belongs to the field of power management technology, specifically relating to a power switch control circuit for power supplies. Background Technology

[0002] In power electronic systems such as switching power supplies, DC-DC converters, and motor drives, the turn-on and turn-off control of power switching transistors (such as MOSFETs and IGBTs) directly affects the system's efficiency, EMI, dynamic response, and reliability. Traditional power switch control circuits for power supplies often employ resistor drives, totem-pole drives, or dedicated driver ICs. However, in high-frequency, high-voltage, or high-current applications, these circuits suffer from problems such as high switching losses, insufficient drive capability, slow switching speed, and susceptibility to ringing or false triggering. Furthermore, existing solutions struggle to achieve precise timing matching and overshoot suppression in scenarios involving multiple parallel circuits or synchronous rectification. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this application is to provide a power switch control circuit for power supply. This application aims to improve the switching speed of the power switch, reduce switching losses, and achieve adjustable drive strength.

[0004] To achieve the above objectives, this application provides the following technical solution: A power switch control circuit for a power supply includes: an input signal conditioning unit for receiving an external PWM control signal and outputting a first drive signal and a second drive signal; a first drive branch connected to the control terminal of the power switch for providing a low-impedance turn-on path in response to the first drive signal during the turn-on phase of the power switch; a second drive branch connected to the control terminal of the power switch for providing a controllable turn-off current path in response to the second drive signal during the turn-off phase of the power switch; an accelerated turn-off unit connected to the control terminal of the power switch for cooperating with the second drive branch during the turn-off process of the power switch to provide a stepwise instantaneous low-impedance turn-off path when the voltage at the control terminal of the power switch is detected to drop below a preset voltage; and an overshoot suppression unit connected between the control terminal of the power switch and ground for suppressing voltage spikes generated by the power switch during the turn-off process.

[0005] Optionally, the input signal conditioning unit includes: a first resistor, a second resistor, a third resistor, a first diode, a second diode, a first capacitor, and a second capacitor; wherein, the first end of the first resistor serves as the input terminal of the control circuit to receive an external PWM control signal, and the second end is connected to a first ground terminal after being connected in series with the second resistor and the first capacitor; the anode of the first diode receives the PWM control signal, the cathode is connected to the first end of the third resistor, and the second end of the third resistor serves as the first output terminal of the input signal conditioning unit to output a first drive signal; the first end of the second capacitor is connected to the second end of the third resistor, and the second end of the second capacitor is connected to a second ground terminal; the cathode of the second diode is connected to the junction of the second resistor and the first capacitor, and the anode is connected to the third ground terminal; the junction of the first resistor and the second resistor serves as the second output terminal of the input signal conditioning unit to output a second drive signal.

[0006] Optionally, the first driving branch includes: a fourth resistor, a fifth resistor, a first PNP transistor, a first NPN transistor, a third diode, and a fourth diode; wherein, the first end of the fourth resistor is connected to the first driving signal, and the second end is connected to both the base of the first PNP transistor and the base of the first NPN transistor; the emitter of the first PNP transistor is connected to the first power supply voltage, and the collector is connected to the control terminal of the power switch through the fifth resistor, and a fourth diode is connected in parallel between the base and emitter of the first PNP transistor; the emitter of the first NPN transistor is connected to the fourth ground terminal, and the collector is connected to the control terminal of the power switch; the third diode is connected in parallel between the collector and emitter of the first NPN transistor.

[0007] Optionally, the second driving branch includes: a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, a second NPN transistor, and a third NPN transistor; wherein, the first end of the sixth resistor is connected to the second driving signal, and the second end is connected to both the base of the second NPN transistor and the first end of the third capacitor; the second end of the third capacitor is connected to the fifth ground terminal through the seventh resistor; the collector of the second NPN transistor is connected to the control terminal of the power switch, and the emitter is connected to the sixth ground terminal through the eighth resistor; the base of the third NPN transistor is connected to the first end of the third capacitor, the collector is connected to the control terminal of the power switch, and the emitter is connected to the seventh ground terminal.

[0008] Optionally, the accelerated shutdown unit includes: a first threshold detection module for detecting whether the voltage at the control terminal of the power switch is lower than a first preset voltage and outputting a first trigger signal; a second threshold detection module for detecting whether the voltage at the control terminal of the power switch is lower than a second preset voltage and outputting a second trigger signal; a first acceleration switch for responding to the first trigger signal and providing a first impedance path; a second acceleration switch for responding to the second trigger signal and providing a second impedance path; and a hysteresis feedback loop connected between the output and input terminals of the first threshold detection module and between the output and input terminals of the second threshold detection module, for preventing the first trigger signal and the second trigger signal from erroneously flipping due to voltage fluctuations within their respective preset voltage hysteresis ranges.

[0009] Optionally, the second preset voltage is less than the first preset voltage.

[0010] Optionally, the first threshold detection module includes: a ninth resistor, a tenth resistor, an eleventh resistor, a fourth NPN transistor, and a fifth diode; wherein, the first end of the ninth resistor is connected to the control terminal of the power switch transistor, and the second end is connected to both the base of the fourth NPN transistor and the first end of the tenth resistor; the second end of the tenth resistor is connected to the anode of the fifth diode, and the cathode of the fifth diode is connected to the first reference ground; the emitter of the fourth NPN transistor is connected to the first reference ground through the eleventh resistor, and the collector serves as the output terminal of the first threshold detection module, outputting a first trigger signal.

[0011] Optionally, the first acceleration switch uses a fifth NPN transistor, whose base is connected to the collector of a fourth NPN transistor, whose emitter is connected to the control terminal of a power switch, and whose collector is connected to an eighth ground terminal through a first acceleration resistor.

[0012] Optionally, the second threshold detection module includes: a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a sixth NPN transistor, and a sixth diode; wherein, the first end of the twelfth resistor is connected to the control terminal of the power switch transistor, and the second end is connected to both the base of the sixth NPN transistor and the first end of the thirteenth resistor; the second end of the thirteenth resistor is connected to the anode of the sixth diode, and the cathode of the sixth diode is connected to the second reference ground; the emitter of the sixth NPN transistor is connected to the second reference ground through the fourteenth resistor, and the collector serves as the output terminal of the second threshold detection module to output a second trigger signal.

[0013] Optionally, the second acceleration switch uses a seventh NPN transistor, whose base is connected to the collector of the sixth NPN transistor, whose emitter is connected to the control terminal of the power switch, and whose collector is connected to the ninth ground terminal through a second acceleration resistor.

[0014] Compared with the prior art, the beneficial effects of this application are as follows: This application achieves reduced power switch conduction losses and suppressed voltage spikes and electromagnetic interference in the early stage of turn-off by setting an input signal conditioning unit to separate the turn-on and turn-off control timings, and by using a low-impedance first drive branch and a controllable turn-off second drive branch respectively. At the same time, by introducing an accelerated turn-off unit connected in parallel with the second drive branch, it provides instantaneous low-impedance turn-off paths in stages according to the degree of voltage drop at the control terminal of the power switch, and accelerates the extraction of residual charge at the end of the turn-off period to reduce turn-off losses. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the circuit structure of a power switch control circuit for a power supply provided in one embodiment of this application; Figure 2 This is a schematic diagram of the circuit structure of the input signal conditioning unit; Figure 3 This is a schematic diagram of the circuit structure of the first driving branch; Figure 4 This is a schematic diagram of the circuit structure of the second drive branch; Figure 5 This is a schematic diagram of the circuit structure of the first threshold detection module; Figure 6 This is a schematic diagram of the circuit structure of the second threshold detection module; Figure 7 This is a schematic diagram of the circuit structure of the overshoot suppression unit. Detailed Implementation

[0016] Specific embodiments of this application will now be described in detail with reference to the accompanying drawings. While specific embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0017] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0018] To facilitate understanding of the embodiments of this application, the following will provide further explanation and description with reference to the accompanying drawings and specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of this application.

[0019] Figure 1 This is a schematic diagram of the circuit structure of a power switch control circuit for a power supply according to one embodiment of this application, as shown below. Figure 1 As shown, the control circuit includes: an input signal conditioning unit for receiving an external PWM control signal and outputting a first drive signal and a second drive signal; a first drive branch connected to the control terminal of the power switch transistor for providing a low-impedance conduction path in response to the first drive signal during the power switch transistor's turn-on phase; a second drive branch connected to the control terminal of the power switch transistor for providing a controllable turn-off current path in response to the second drive signal during the power switch transistor's turn-off phase; an accelerated turn-off unit connected to the control terminal of the power switch transistor for working in conjunction with the second drive branch during the power switch transistor's turn-off process, for providing a step-by-step instantaneous low-impedance turn-off path when the voltage at the control terminal of the power switch transistor is detected to drop below a preset voltage, so that the second drive branch can achieve controllable slow turn-off in the initial stage of the power switch transistor's turn-off and the accelerated turn-off unit can achieve rapid charge extraction in the final stage of the turn-off process; and an overshoot suppression unit connected between the control terminal of the power switch transistor and ground for suppressing voltage spikes generated by the power switch transistor during the turn-off process.

[0020] In this control circuit, the input signal conditioning unit receives an external PWM control signal, and after conditioning, outputs a first drive signal to the first drive branch and a second drive signal to the second drive branch. During the power switch's turn-on phase, the first drive branch responds to the first drive signal by providing a low-impedance conduction path to achieve fast charging. During the turn-off phase, the second drive branch responds to the second drive signal by providing a controllable turn-off current path to extract gate charge at an appropriate speed, suppressing voltage spikes and electromagnetic interference in the initial turn-off phase. Simultaneously, an accelerated turn-off unit is connected in parallel to the second drive branch. When the voltage at the power switch control terminal is detected to drop below a preset voltage, it sequentially activates the instantaneous low-impedance turn-off path to accelerate the extraction of residual charge at the end. The overshoot suppression unit is always connected between the control terminal and ground to further absorb and clamp voltage spikes generated during the turn-off process. The technical advantages of this control circuit are as follows: by reducing conduction losses through the low impedance design of the conduction branch, suppressing initial turn-off spikes and electromagnetic interference through the controllable current of the turn-off branch, rapidly extracting residual charge at the end of turn-off through the graded acceleration mechanism of the accelerated turn-off unit to reduce turn-off losses, and supplementing the spike absorption of the overshoot suppression unit, the high-frequency switching efficiency, electromagnetic compatibility and dynamic reliability of the power switching transistor are comprehensively considered.

[0021] Furthermore, it should be noted that in this application, the drain and source of the power switch are used to connect to the main power circuit. The specific connection method depends on the topology of the power system. For example, in a buck converter, the drain is connected to the positive input terminal, and the source is connected to ground or a sampling resistor; in a boost converter, the drain is connected to the inductor and the output diode, and the source is connected to ground; in a flyback converter, the drain is connected to the primary winding of the transformer, and the source is connected to ground or a sampling resistor. It should be noted that in this application, the connection of the drain and source of the power switch falls within the scope of the main power circuit. Those skilled in the art can configure it according to the actual application scenario, and this application does not limit this. The scope of protection of this application only involves the driving and control of the control terminal (gate) of the power switch.

[0022] In another exemplary embodiment, such as Figure 2 As shown, the input signal conditioning unit includes a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a second diode D2, a first capacitor C1, and a second capacitor C2. The first terminal of the first resistor R1 serves as the input terminal of the control circuit, receiving an external PWM control signal. The second terminal is connected in series with the second resistor R2 and the first capacitor C1, and then connected to the first ground terminal GND1. The anode of the first diode D1 receives the PWM control signal (provided by an external PWM controller chip or microcontroller MCU), and the cathode is connected to the first terminal of the third resistor R3. The second terminal of the third resistor R3 serves as the first output terminal of the input signal conditioning unit, outputting a first drive signal. The first terminal of the second capacitor C2 is connected to the second terminal of the third resistor R3, and the second terminal of the second capacitor C2 is connected to the second ground terminal GND2. The cathode of the second diode D2 is connected to the junction of the second resistor R2 and the first capacitor C1, and the anode is connected to the third ground terminal GND3. The junction of the first resistor R1 and the second resistor R2 serves as the second output terminal of the input signal conditioning unit, outputting a second drive signal.

[0023] In this embodiment, the PWM control signal provided by an external PWM controller chip or microcontroller (MCU) is filtered by an RC filter network composed of a first resistor R1, a second resistor R2, and a first capacitor C1 to remove high-frequency noise and generate a delay. A second drive signal is output at the connection between the first resistor R1 and the second resistor R2, which is used to control the timing of the turn-off branch. On the other hand, after the PWM control signal is forward-biased by the first diode D1, it is current-limited by the third resistor R3 and forms a smooth first drive signal with the cooperation of the second capacitor C2, which is used to control the conduction branch. The cathode of the second diode D2 is connected to the connection between the second resistor R2 and the first capacitor C1, and the anode is connected to the third ground terminal GND3, which plays a clamping and negative voltage absorption role, preventing negative voltages exceeding the safe range during signal conditioning and protecting the subsequent drive circuit. The structural features of this input signal conditioning unit are: it adopts dual-channel independent output to generate conduction drive signals (first drive signals) and turn-off drive signals (second drive signals) with different timing and drive strengths; at the same time, the combination of diodes and RC networks realizes signal shaping, delay matching, and noise suppression. This input signal conditioning unit has three main advantages: first, it can effectively separate the turn-on and turn-off control paths, facilitating independent optimization of subsequent drive branches; second, by adjusting the parameters of the first resistor R1, the second resistor R2, and the first capacitor C1, it can flexibly match the switching characteristics of different power switches, thereby achieving precise coordination of the turn-on and turn-off timing; and third, it can improve the response speed and anti-interference capability of the PWM signal edge, avoiding false triggering caused by signal glitches or jitter, thus helping to reduce the loss of the power switch.

[0024] In another exemplary embodiment, such as Figure 3 As shown, the first driving branch includes: a fourth resistor R4, a fifth resistor R5, a first PNP transistor Q1, a first NPN transistor Q2, a third diode D3, and a fourth diode D4; wherein, the first end of the fourth resistor R4 is connected to the first driving signal, and the second end is connected to both the base of the first PNP transistor Q1 and the base of the first NPN transistor Q2; the emitter of the first PNP transistor Q1 is connected to the first supply voltage VCC1, and the collector is connected to the control terminal of the power switch M through the fifth resistor R5, and the fourth diode D4 is connected in parallel between the base and emitter of the first PNP transistor Q1; the emitter of the first NPN transistor Q2 is connected to the fourth ground terminal GND4, and the collector is connected to the control terminal of the power switch M; the third diode D3 is connected in parallel between the collector and emitter of the first NPN transistor Q2.

[0025] In this embodiment, the first driving branch adopts a complementary emitter follower structure composed of a first PNP transistor Q1 and a first NPN transistor Q2. Its working principle is as follows: when the input first driving signal is high, the first NPN transistor Q2 is turned on and the first PNP transistor Q1 is turned off. The control terminal (gate) of the power switch transistor M is quickly pulled low to the fourth ground terminal GND4 through the first NPN transistor Q2 to achieve turn-off. When the first driving signal is low, the first NPN transistor Q2 is turned off and the first PNP transistor Q1 is turned on. The first supply voltage VCC1 injects current into the control terminal of the power switch transistor M through the first PNP transistor Q1 and the fifth resistor R5, so that it is quickly charged and turned on.

[0026] The structural features of this drive branch are as follows: A fourth diode D4 is connected in parallel between the emitter and base of the first PNP transistor Q1, which prevents reverse breakdown of the base-emitter junction of the first PNP transistor Q1 to protect the first PNP transistor Q1; A third diode D3 is connected in parallel between the collector and emitter of the first NPN transistor Q2, which is responsible for providing a low-impedance freewheeling path when the power switch M is turned off, so as to suppress the negative voltage spike caused by parasitic inductance; At the same time, a fifth resistor R5 is connected in series between the collector of the first PNP transistor Q1 and the control terminal of the power switch M, which can adjust the drive strength and switching speed when the power switch M is turned on. The above circuit structure provides the following technical benefits: First, the complementary push-pull output provides a low-impedance conduction path, which helps to shorten the charging time of the control terminal of the power switch M and reduce conduction losses. Second, by connecting the fifth resistor R5 in series, users can flexibly adjust the conduction speed according to the actual switching frequency and electromagnetic interference limits, thereby achieving controllable adjustment of the drive strength of the power switch M. Third, the fourth diode D4 and the third diode D3 provide dual protection, which can effectively prevent their respective drive transistors from being damaged by reverse voltage or gate negative voltage, thereby improving the circuit's shock resistance and long-term operational reliability.

[0027] In another exemplary embodiment, such as Figure 4 As shown, the second drive branch includes: a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a third capacitor C3, a second NPN transistor Q3, and a third NPN transistor Q4; wherein, the first end of the sixth resistor R6 is connected to the second drive signal, and the second end is connected to both the base of the second NPN transistor Q3 and the first end of the third capacitor C3; the second end of the third capacitor C3 is connected to the fifth ground terminal GND5 through the seventh resistor R7; the collector of the second NPN transistor Q3 is connected to the control terminal of the power switch M, and the emitter is connected to the sixth ground terminal GND6 through the eighth resistor R8; the base of the third NPN transistor Q4 is connected to the first end of the third capacitor C3, the collector is connected to the control terminal of the power switch M, and the emitter is connected to the seventh ground terminal GND7.

[0028] In this embodiment, the second driving branch adopts a two-stage NPN transistor cascade and RC timing control structure. Its working principle is as follows: when the second driving signal is high, the signal is simultaneously applied to the base of the second NPN transistor Q3 and the first terminal of the third capacitor C3 after passing through the sixth resistor R6, so that the second NPN transistor Q3 is instantaneously turned on. The control terminal (gate) of the power switch M discharges to the sixth ground terminal GND6 through the second NPN transistor Q3 and the eighth resistor R8, realizing a controllable turn-off process. At the same time, the third capacitor C3 is charged through the sixth resistor R6. When its voltage rises to the conduction threshold of the third NPN transistor Q4, the third NPN transistor Q4 is turned on, further providing a second lower impedance path and accelerating the extraction of gate charge.

[0029] The structural features of the second drive branch are as follows: the RC delay network composed of the sixth resistor R6 and the third capacitor C3 can determine the conduction delay time of the third NPN transistor Q4; the seventh resistor R7 can provide a discharge path for the third capacitor C3, ensuring that the third capacitor C3 is reset before the next cycle; the eighth resistor R8 is connected in series with the emitter of the second NPN transistor Q3 to limit the peak discharge current when the second NPN transistor Q3 is turned on, avoiding excessively high voltage spikes caused by too fast turn-off; the collectors of the second NPN transistor Q3 and the third NPN transistor Q4 are directly connected to the control terminal of the power switch M, forming a parallel two-stage turn-off path. The second drive branch with the above structure has three advantages: First, it can delay the turn-on of the third NPN transistor Q4 through an RC delay network, thereby achieving a graded turn-off process. Initially, the second NPN transistor Q3 slowly turns off the transistor with a limited current to suppress voltage spikes and electromagnetic interference. Later, the third NPN transistor Q4 assists in accelerating the turn-off to reduce turn-off losses, thus balancing turn-off safety and speed. Second, the series connection of the eighth resistor R8 allows the turn-off strength of the power switch M to be adjusted, thereby adapting to the gate charge characteristics of different power switches. Third, the entire branch uses only NPN transistors, which has good process compatibility and low cost, while avoiding the saturation voltage drop problem that PNP transistors may introduce in the turn-off path, thus improving the reliability of turn-off.

[0030] In another exemplary embodiment, the accelerated shutdown unit includes: a first threshold detection module for detecting whether the voltage at the control terminal of the power switch M is lower than a first preset voltage and outputting a first trigger signal; a second threshold detection module for detecting whether the voltage at the control terminal of the power switch M is lower than a second preset voltage and outputting a second trigger signal, wherein the second preset voltage is less than the first preset voltage; a first acceleration switch for responding to the first trigger signal and providing a first impedance path; a second acceleration switch for responding to the second trigger signal and providing a second impedance path; and a hysteresis feedback loop connected between the output and input terminals of the first threshold detection module and between the output and input terminals of the second threshold detection module, for preventing the first trigger signal and the second trigger signal from erroneously flipping due to voltage fluctuations within their respective preset voltage hysteresis ranges.

[0031] In this embodiment, the accelerated turn-off unit monitors the voltage drop at the control terminal of the power switch M in real time through a first threshold detection module and a second threshold detection module. When the voltage drops below a first preset voltage, a first trigger signal is activated, a first acceleration switch is turned on, and a first impedance path is provided to initiate first-stage acceleration. When the voltage drops further below a lower second preset voltage, a second trigger signal is activated, a second acceleration switch is turned on, and a second impedance path is provided to initiate second-stage acceleration. Simultaneously, a hysteresis feedback loop introduces positive feedback between the output and input terminals of the two threshold detection modules to prevent the two trigger signals from erroneously flipping due to voltage fluctuations within their respective preset voltage hysteresis ranges. This unit can achieve a smooth transition from "slow controllable turn-off" to "graded acceleration" and then to "strong extraction and fast turn-off at the end of the turn-off process." It can suppress voltage spikes and electromagnetic interference in the early stage of turn-off, shorten the charge extraction time at the control terminal of the power switch in the final stage of turn-off, reduce turn-off losses, and ensure the stability and reliability of the trigger action through the hysteresis characteristic, thereby helping to avoid false triggering caused by noise or voltage swirl.

[0032] In another exemplary embodiment, such as Figure 5 As shown, the first threshold detection module includes a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fourth NPN transistor Q5, and a fifth diode D5. The first end of the ninth resistor R9 is connected to the control terminal (gate) of the power switch M, and the second end is connected to both the base of the fourth NPN transistor Q5 and the first end of the tenth resistor R10. The second end of the tenth resistor R10 is connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 is connected to the first reference ground GND_ref1. The emitter of the fourth NPN transistor Q5 is connected to the first reference ground GND_ref1 through the eleventh resistor R11, and the collector serves as the output terminal of the first threshold detection module, outputting a first trigger signal.

[0033] In this embodiment, the first acceleration switch uses the fifth NPN transistor Q6, whose base is connected to the collector of the fourth NPN transistor Q5, the emitter of the fifth NPN transistor Q6 is connected to the control terminal of the power switch transistor M, and the collector is connected to the eighth ground terminal GND8 through the first acceleration resistor R_acc1.

[0034] The first threshold detection module is used to detect whether the control terminal voltage of the power switch transistor M is lower than the first threshold voltage Vth1. The first threshold voltage Vth1 is jointly set by the forward voltage drop of the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11 and the fifth diode D5.

[0035] When the control terminal voltage of the power switch M is higher than the first threshold voltage Vth1, the fourth NPN transistor Q5 is turned on, its collector outputs a low level, and the first acceleration switch remains off; when the control terminal voltage of the power switch M is lower than the first threshold voltage Vth1, the fourth NPN transistor Q5 is turned off, its collector outputs a high level, the base of the first acceleration switch receives a bias current and turns on, thereby providing a low-impedance turn-off path through the first acceleration resistor R_acc1, thus accelerating the extraction of charge from the control terminal of the power switch M.

[0036] The circuit structure of this first threshold detection module is characterized by the following: First, the ninth resistor R9, the tenth resistor R10, and the fifth diode D5 form a resistor voltage divider and diode reference network, thereby enabling a stable setting of the first preset voltage Vth1. Second, the emitter of the fourth NPN transistor Q5 is connected in series with the eleventh resistor R11, which can be used to stabilize the operating point and adjust the detection sensitivity. Finally, the collector of the first acceleration switch, connected in series with the first acceleration resistor R_acc1, can limit the peak current during accelerated conduction. Based on the above structure, this module can achieve the following technical effects: through the combination of resistor voltage divider and diode reference, the first threshold voltage Vth1 can be accurately and stably maintained over a wide temperature range without being affected by power supply fluctuations; by adjusting the resistance values ​​of the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11, the first threshold voltage Vth1 and the detection hysteresis can be flexibly set, thereby adapting to the turn-off characteristics of different power switches.

[0037] In another exemplary embodiment, such as Figure 6As shown, the second threshold detection module includes the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14, the sixth NPN transistor Q7, and the sixth diode D6. Among them, the first end of the twelfth resistor R12 is connected to the control end (gate) of the power switch tube M, and the second end is simultaneously connected to the base of the sixth NPN transistor Q7 and the first end of the thirteenth resistor R13. The second end of the thirteenth resistor R13 is connected to the anode of the sixth diode D6, and the cathode of the sixth diode D6 is connected to the second reference ground GND_ref2. The emitter of the sixth NPN transistor Q7 is connected to the second reference ground GND_ref2 through the fourteenth resistor R14, and the collector serves as the output end of the second threshold detection module to output the second trigger signal.

[0038] In this embodiment, the second acceleration switch uses the seventh NPN transistor Q8. Its base is connected to the collector of the sixth NPN transistor Q7. The emitter of the seventh NPN transistor Q8 is connected to the control end of the power switch tube M, and the collector is connected to the ninth ground terminal GND9 through the second acceleration resistor R_acc2.

[0039] The second threshold detection module is used to detect whether the voltage at the control end of the power switch tube M is lower than the second preset voltage Vth2, and Vth2 < Vth1 (setting Vth2 to be less than Vth1 aims to form a two-stage acceleration mechanism with light first and then heavy during the turn-off process. When the voltage at the control end of the power switch tube M drops to the higher Vth1, the first-stage moderate acceleration is first started to suppress the voltage spike. When the voltage further drops to the lower Vth2, the second-stage stronger acceleration is started to quickly extract the residual charge, so as to balance electromagnetic compatibility and turn-off efficiency). The second preset voltage Vth2 is jointly set by the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14, and the forward voltage drop of the sixth diode D6. To ensure Vth2 < Vth1, it can be achieved through the following methods: Method 1: Select the resistance value of the ninth resistor R9 to be greater than that of the twelfth resistor R12, so that the voltage division ratio of the first threshold detection module is higher than that of the second threshold detection module, so that Vth1 is higher than Vth2 under the same conditions. Method 2: Use diodes with different forward voltage drops. For example, the fifth diode D5 uses a silicon tube (forward voltage drop is about 0.7V), and the sixth diode D6 uses a Schottky diode (forward voltage drop is about 0.3V - 0.4V). Utilize the characteristic that the voltage drop of the fifth diode D5 is higher than that of the sixth diode D6 to make Vth1 higher than Vth2.

[0040] The structural features of this second threshold detection module are as follows: By employing a voltage divider and reference network composed of the twelfth resistor R12, the thirteenth resistor R13, and the sixth diode D6, a stable setting of the second preset voltage Vth2 can be achieved. Furthermore, by adjusting the resistor ratio or selecting different diode types (e.g., D5 is a silicon diode, D6 is a Schottky diode), Vth2 can be ensured to be precisely lower than Vth1, thus forming a clear two-stage voltage detection window. The collector of the second acceleration switch Q8, connected in series with the second acceleration resistor R_acc2, can limit the peak current during the second-stage acceleration conduction, thereby avoiding new voltage spikes at the end of the turn-off period. Based on the above structure, this module can achieve the following technical effects: through the combination of resistor voltage division and diode reference, Vth2 is accurately stable over a wide temperature range, and the difference between it and Vth1 is controllable, ensuring that the two-stage acceleration is triggered in the preset voltage sequence; by adjusting the resistance values ​​of the twelfth resistor R12, the thirteenth resistor R13, and the fourteenth resistor R14, Vth2 and the detection hysteresis can be flexibly set, thus adapting to the turn-off characteristic requirements of different power switches. The second threshold detection module is integrated with the first threshold detection module to jointly realize a graded acceleration strategy for the turn-off process from slow to fast and then to even faster. This allows for the suppression of voltage spikes and electromagnetic interference at a slower speed in the early stage of the turn-off of the power switch M, and the rapid extraction of residual charge at the end of the turn-off with two progressively stronger steps. This approach can simultaneously ensure electromagnetic compatibility, switching efficiency, and system reliability.

[0041] In another exemplary embodiment, please refer to Figure 5 and Figure 6 The hysteresis feedback loop includes a seventh diode D7, an eighth diode D8, a fifteenth resistor R15, and a sixteenth resistor R16. The anode of the seventh diode D7 is connected to the collector of the fourth NPN transistor Q5, and its cathode is connected to the base of the fourth NPN transistor Q5. The anode of the eighth diode D8 is connected to the collector of the sixth NPN transistor Q7, and its cathode is connected to the base of the sixth NPN transistor Q7. The first terminal of the fifteenth resistor R15 is connected to the base of the fourth NPN transistor Q5, and its second terminal is connected to the tenth ground terminal GND10. The first terminal of the sixteenth resistor R16 is connected to the base of the sixth NPN transistor Q7, and its second terminal is connected to the eleventh ground terminal GND11.

[0042] In this embodiment, when the fourth NPN transistor Q5 is turned on, its collector is at a low level. The seventh diode D7 is reverse-biased and cut off because its anode potential is lower than its cathode potential, thus not affecting the base bias of the fourth NPN transistor Q5. When the fourth NPN transistor Q5 is turned off, its collector outputs a high impedance state. If the voltage at the control terminal of the power switch M rises to slightly higher than the first preset voltage Vth1, the seventh diode D7 is forward-biased, feeding back the high potential of the collector of the fourth NPN transistor Q5 to its base, raising the base potential and thus maintaining the cut-off state of the fourth NPN transistor Q5, preventing it from turning on again near the threshold point due to small voltage fluctuations. Similarly, the eighth diode D8 provides the same positive feedback hysteresis function for the sixth NPN transistor Q7. The fifteenth resistor R15 and the sixteenth resistor R16 provide base pull-down discharge paths for the fourth NPN transistor Q5 and the sixth NPN transistor Q7, respectively, ensuring that the base potential is stable in the non-triggered state. The technical effect of this circuit is that by introducing positive feedback between the output and input terminals of the two threshold detection modules, hysteresis intervals are formed near the first preset voltage Vth1 and the second preset voltage Vth2, respectively. This ensures that once the trigger signal flips, the voltage at the control terminal of the power switch M needs to be significantly lower than the original threshold (i.e., across the entire hysteresis interval) before it can flip back. This effectively prevents the trigger signal from flipping erroneously due to parasitic oscillations, power supply ripples, or gate voltage swings, ensuring the stable and reliable operation of the two-stage acceleration switch and improving the anti-interference capability and operational robustness of the entire acceleration turn-off unit.

[0043] In another exemplary embodiment, such as Figure 7 As shown, the overshoot suppression unit includes a first clamping diode D9, a second clamping diode D10, a transient voltage suppressor (TVS), a current-limiting resistor R17, and an accelerating discharge diode D11. The anode of the first clamping diode D9 is connected to the control terminal of the power switch M, and its cathode is connected to the anode of the second clamping diode D10 to form node N. The cathode of the second clamping diode D10 is connected to the second supply voltage VCC2. The first terminal of the transient voltage suppressor TVS is connected to node N, and its second terminal is connected to the twelfth ground terminal GND12. The first terminal of the current-limiting resistor R17 is connected to node N, and its second terminal is connected to the thirteenth ground terminal GND13. The first terminal of the accelerating discharge diode D11 is connected to the control terminal of the power switch M, and its second terminal is connected to the fourteenth ground terminal GND14.

[0044] In this embodiment, during the turn-off process of the power switch M, a voltage spike is generated at its control terminal due to parasitic inductance and rapid current changes. If the control terminal voltage rises to a level higher than the sum of the second supply voltage VCC2 and the forward voltage drop of the second clamping diode D10, the first clamping diode D9 and the second clamping diode D10 are sequentially turned on, clamping the control terminal voltage to VCC2 + VF - D10 (i.e., the sum of the second supply voltage VCC2 and the forward voltage drop of the second clamping diode D10). The overshoot suppression unit (VF) prevents damage to the power switch M from excessive positive voltage. Simultaneously, if the positive spike energy is large and the voltage exceeds the breakdown voltage of the transient voltage suppressor (TVS), the TVS momentarily conducts, discharging excess spike energy to the twelfth ground terminal GND12 through the current-limiting resistor R17 to further suppress the overshoot amplitude. When the control terminal voltage drops below ground potential (negative voltage spike) and exceeds the forward voltage drop of the accelerating discharge diode D11, D11 conducts, providing a low-impedance discharge path and rapidly raising the negative voltage to the range of -0.3V to -0.4V, preventing the power switch from mis-conducting or damaging the gate oxide layer due to negative voltage overshoot. The current-limiting resistor R17 limits the surge current peak when the TVS operates, protecting the TVS and preventing additional load on the normal switching process. This overshoot suppression unit achieves comprehensive suppression of both positive and negative voltage spikes, ensuring that the gate voltage of the power switch is always within a safe range.

[0045] The circuit structure of this overshoot suppression unit is characterized by the following: the first clamping diode D9 and the second clamping diode D10 are connected in series between the control terminal of the power switch M and the second supply voltage VCC2, forming a bidirectional clamping frame. The first clamping diode D9 is responsible for conducting the forward overvoltage of the control terminal of the power switch M to node N, while the second clamping diode D10 is responsible for limiting the upper voltage of node N to the sum of VCC2 and its forward voltage drop. At the same time, the transient voltage suppressor TVS and the current limiting resistor R17 are connected in parallel across node N and ground. The transient voltage suppressor TVS is used to absorb high-energy spikes exceeding the preset threshold, and the current limiting resistor R17 is used to limit the surge current when the transient voltage suppressor TVS operates. In addition, the accelerating discharge diode D11 is independently connected between the control terminal and ground to suppress negative voltage spikes. This overshoot suppression unit adopts a hybrid architecture of "series clamping diode + TVS parallel current-limiting resistor + independent negative voltage discharge diode", which can achieve the following technical effects: First, the series clamping of the first clamping diode D9 and the second clamping diode D10 strictly limits the forward overvoltage of the power switch M control terminal to within VCC2+VF_D10, with a response speed in the nanosecond range, which is much faster than the traditional RC filter network; Second, the introduction of TVS provides a high-energy peak absorption channel, which, together with the current-limiting resistor R17, can not only avoid the damage of a single clamping diode due to excessive instantaneous energy, but also prevent the TVS conduction current overshoot from causing secondary interference to the gate drive circuit; Third, the accelerating discharge diode D11 is implemented with a Schottky diode, and its extremely low forward voltage drop (about 0.3V~0.4V) can be instantaneously turned on when a negative voltage peak occurs, pulling the negative voltage of the control terminal up to a safe range, thereby effectively preventing the power switch M from being mis-turned on or the gate oxide layer from being damaged due to negative voltage overshoot. In summary, this overshoot suppression unit can achieve fast and low-delay suppression of bidirectional voltage spikes, which helps to improve the electromagnetic compatibility and long-term reliability of the power switch M during the turn-off process.

[0046] The above embodiments are only for illustrating the technical concept and features of this application, and are intended to enable those skilled in the art to understand the content of this application and implement it accordingly. They should not be construed as limiting the scope of protection of this application. All equivalent changes or modifications made in accordance with the spirit and essence of this application should be included within the scope of protection of this application.

Claims

1. A power switch control circuit for a power supply, characterized in that, The control circuit includes: The input signal conditioning unit is used to receive external PWM control signals and output a first drive signal and a second drive signal; The first drive branch is connected to the control terminal of the power switch tube and is used to respond to the first drive signal during the power switch tube's turn-on phase to provide a low-impedance turn-on path. The second drive branch is connected to the control terminal of the power switch tube and is used to provide a controllable turn-off current path in response to the second drive signal during the turn-off phase of the power switch tube. The accelerated turn-off unit is connected to the control terminal of the power switch tube and works in conjunction with the second drive branch during the turn-off process of the power switch tube. It is used to provide instantaneous low-impedance turn-off path in stages when the voltage at the control terminal of the power switch tube is detected to drop below the preset voltage. The overshoot suppression unit is connected between the control terminal of the power switch and ground to suppress voltage spikes generated during the turn-off process of the power switch.

2. The control circuit according to claim 1, characterized in that, The input signal conditioning unit includes: A first resistor, a second resistor, a third resistor, a first diode, a second diode, a first capacitor, and a second capacitor; wherein, The first end of the first resistor serves as the input terminal of the control circuit to receive external PWM control signals, and the second end is connected to the first ground terminal after being connected in series with the second resistor and the first capacitor. The anode of the first diode is connected to the PWM control signal, the cathode is connected to the first end of the third resistor, and the second end of the third resistor serves as the first output end of the input signal conditioning unit to output the first drive signal. The first terminal of the second capacitor is connected to the second terminal of the third resistor, and the second terminal of the second capacitor is connected to the second ground terminal. The cathode of the second diode is connected to the junction of the second resistor and the first capacitor, and the anode is connected to the third ground terminal; The connection between the first resistor and the second resistor serves as the second output terminal of the input signal conditioning unit, from which the second drive signal is output.

3. The control circuit according to claim 2, characterized in that, The first driving branch includes: The fourth resistor, the fifth resistor, the first PNP transistor, the first NPN transistor, the third diode, and the fourth diode; among them, The first end of the fourth resistor is connected to the first drive signal, and the second end is connected to both the base of the first PNP transistor and the base of the first NPN transistor. The emitter of the first PNP transistor is connected to the first power supply voltage, the collector is connected to the control terminal of the power switch transistor through the fifth resistor, and a fourth diode is connected in parallel between the base and emitter of the first PNP transistor. The emitter of the first NPN transistor is connected to the fourth ground terminal, and the collector is connected to the control terminal of the power switch transistor. The third diode is connected in parallel between the collector and emitter of the first NPN transistor.

4. The control circuit according to claim 2, characterized in that, The second drive branch includes: The sixth resistor, the seventh resistor, the eighth resistor, the third capacitor, the second NPN transistor, and the third NPN transistor; among them, The first end of the sixth resistor is connected to the second drive signal, and the second end is connected to both the base of the second NPN transistor and the first end of the third capacitor. The second terminal of the third capacitor is connected to the fifth ground terminal through the seventh resistor; The collector of the second NPN transistor is connected to the control terminal of the power switch, and the emitter is connected to the sixth ground terminal through the eighth resistor. The base of the third NPN transistor is connected to the first terminal of the third capacitor, the collector is connected to the control terminal of the power switch, and the emitter is connected to the seventh ground terminal.

5. The control circuit according to claim 1, characterized in that, The accelerated shutdown unit includes: The first threshold detection module is used to detect whether the voltage at the control terminal of the power switch is lower than the first preset voltage and output a first trigger signal. The second threshold detection module is used to detect whether the voltage at the control terminal of the power switch is lower than the second preset voltage and output a second trigger signal. A first acceleration switch, responding to a first trigger signal and providing a first impedance path; A second acceleration switch, responding to a second trigger signal and providing a second impedance path; The hysteresis feedback loop is connected between the output and input terminals of the first threshold detection module and between the output and input terminals of the second threshold detection module. It is used to prevent the first trigger signal and the second trigger signal from being falsely flipped due to voltage fluctuations within their respective preset voltage hysteresis ranges.

6. The control circuit according to claim 5, characterized in that, The second preset voltage is less than the first preset voltage.

7. The control circuit according to claim 5, characterized in that, The first threshold detection module includes: The ninth resistor, the tenth resistor, the eleventh resistor, the fourth NPN transistor, and the fifth diode; among them, The first end of the ninth resistor is connected to the control terminal of the power switch transistor, and the second end is connected to both the base of the fourth NPN transistor and the first end of the tenth resistor. The second end of the tenth resistor is connected to the anode of the fifth diode, and the cathode of the fifth diode is connected to the first reference ground; The emitter of the fourth NPN transistor is connected to the first reference ground through the eleventh resistor, and the collector serves as the output terminal of the first threshold detection module to output the first trigger signal.

8. The control circuit according to claim 7, characterized in that, The first acceleration switch uses a fifth NPN transistor, whose base is connected to the collector of a fourth NPN transistor, whose emitter is connected to the control terminal of a power switch, and whose collector is connected to an eighth ground terminal through a first acceleration resistor.

9. The control circuit according to claim 5, characterized in that, The second threshold detection module includes: The twelfth resistor, the thirteenth resistor, the fourteenth resistor, the sixth NPN transistor, and the sixth diode; among them, The first end of the twelfth resistor is connected to the control terminal of the power switch transistor, and the second end is connected to both the base of the sixth NPN transistor and the first end of the thirteenth resistor. The second end of the thirteenth resistor is connected to the anode of the sixth diode, and the cathode of the sixth diode is connected to the second reference ground; The emitter of the sixth NPN transistor is connected to the second reference ground through the fourteenth resistor, and the collector serves as the output terminal of the second threshold detection module to output the second trigger signal.

10. The control circuit according to claim 9, characterized in that, The second acceleration switch uses a seventh NPN transistor, whose base is connected to the collector of the sixth NPN transistor, the emitter of the seventh NPN transistor is connected to the control terminal of the power switch, and the collector is connected to the ninth ground terminal through the second acceleration resistor.

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