Self-adaptive circuit for reducing capacitor howling

Abstract

The utility model provides a self-adaptive circuit for reducing capacitor squeal. The self-adaptive circuit comprises an MOS tube Q1, a first voltage conversion circuit, a second voltage conversion circuit, a triode Q5 and a switch control circuit. Compared with the prior art, when the input power supply has the condition that the alternating voltage is superposed, the conducting channel of the field-effect tube is closed, and the field-effect tube is equivalent to a diode, so that the capacitor voltage at the rear end of the field-effect tube cannot fluctuate along with the input power supply, and the condition that the capacitor generates howling is reduced. In addition, the high-power self-adaptive circuit for reducing the capacitor squeal does not need external control, and can perform self-adaptive adjustment according to the condition of an input power supply.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit design, and particularly relates to a high-power adaptive circuit for reducing capacitor whistling.

Background Art

[0002] In an automotive electrical system, an alternating voltage may be superimposed on the input power supply side. A ripple voltage with a certain frequency will appear in the entire operating system along with the automotive input power supply. As Figure 1 shown, it is a waveform diagram of the input power supply with a superimposed alternating voltage in an embodiment. When the chip capacitor in the circuit is subjected to an alternating voltage, it will exhibit a special physical phenomenon. It will be deformed by an external force in a certain direction. When the frequency of the alternating voltage reaches a certain value, mechanical vibration will be generated, thereby generating a sound, that is, the capacitor whistling phenomenon.

[0003] In the circuit, in order to prevent damage to the product due to reverse power connection, a diode or a field effect transistor is connected in series on the input circuit to play a role in preventing reverse connection. When the input power supply VIN supplies power normally, it will charge the capacitor at the back end through the diode. When the input power supply VIN has a superimposed alternating current, due to the unidirectional conductivity of the diode, the capacitor voltage at the back end of the diode is greater than that at the front end of the diode. The capacitor voltage will first supply power to the load VOUT and will not fluctuate with the input power supply VIN. When the capacitor voltage is lower than the voltage at the front end of the diode, it will charge the capacitor. In this way, the frequency of the voltage fluctuation on the capacitor will be reduced, and thus the whistling situation generated by the capacitor will also be reduced. However, diodes are usually used in low-power circuits. When the circuit current is large, the power consumption of the diode is relatively large, and thus the generated heat is relatively high. In a high-temperature situation, the diode will be overheated and burned out. Therefore, for high-power circuits, a field effect transistor is selected for power supply reverse protection. As Figure 2 shown, it is a circuit schematic diagram of the input circuit in an embodiment. Since the charge flows through the conducting channel after the field effect transistor Q1 is turned on, when the voltage of the input power supply VIN decreases, the conducting channel will not close, and the capacitor voltage at the back end of the field effect transistor Q1 will fluctuate with the input power supply VIN, so the whistling situation generated by the capacitor will be relatively serious.

[0004] Currently, there are the following solutions for capacitor whistling: ①. Support the capacitor by means of a bracket, and use the elastic action of the metal terminal to relieve stress, thereby reducing the degree of capacitor whistling. Specifically, as Figure 3 shown, it is a structural schematic diagram of an anti-whistling capacitor in the prior art. ②. Place the same specification chip capacitors symmetrically at the same positions on the front and back sides of the PCB board, and reduce the whistling degree by the vibration cancellation of the two capacitors. Specifically, as Figure 4 shown, it is a structural schematic diagram of another anti-whistling capacitor in the prior art.

[0005] Among them, the disadvantages of the prior art solution ① are: using a support capacitor, the cost is relatively high, and the package size is relatively large. The disadvantages of the prior art solution ② are: the degree of reducing capacitor crosstalk is limited, and it is related to welding process, chip symmetry degree, etc., and the situation where capacitor crosstalk cannot be effectively reduced will occur.

[0006] Therefore, it is necessary to propose a new technical solution to solve the above problems.

Utility Model Content

[0007] One of the purposes of the present utility model is to provide a high-power adaptive circuit for reducing capacitor crosstalk, which can not only reduce costs, but also reduce the situation of capacitor crosstalk.

[0008] According to one aspect of the present utility model, the present utility model provides an adaptive circuit for reducing capacitor crosstalk, which includes an MOS transistor Q1, a first voltage conversion circuit, a second voltage conversion circuit, a triode Q5, and a switch control circuit. The input power supply terminal VIN is connected to node A; the first connection end of the MOS transistor Q1 is connected to node A, its second connection end is connected to node B, and its control end is connected to node D; the input end of the first voltage conversion circuit is connected to node A, the output end of the first voltage conversion circuit is connected to node C, the first voltage conversion circuit steps down the voltage at its input end by a first predetermined voltage and then outputs, the input end of the second voltage conversion circuit is connected to node B, the output end of the second voltage conversion circuit is connected to node G, the second voltage conversion circuit steps down the voltage at its input end by a second predetermined voltage and then outputs, the first connection end of the triode Q5 is connected to node G, its control end is connected to node C, and its second connection end is connected to node F; the input end of the switch control circuit is connected to node F, and the output end of the switch control circuit is connected to node D; when the triode Q5 is turned off, the switch control circuit controls the MOS transistor Q1 to conduct, and when the triode Q5 is turned on, the switch control circuit controls the MOS transistor Q1 to turn off.

[0009] Compared with the prior art, when there is an overlapping AC voltage in the input power supply in the present utility model, the conductive channel of the field effect transistor (Q1) is turned off, then the field effect transistor is equivalent to a diode, so that the capacitor voltage at the back end of the field effect transistor (Q1) will not fluctuate with the input power supply, thereby reducing the situation of capacitor crosstalk. In addition, the high-power adaptive circuit for reducing capacitor crosstalk provided by the present utility model does not require external control and can be adaptively adjusted according to the input power supply situation.

Description of the Drawings

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0011] Figure 1 It is a waveform diagram of the input power supply with superimposed AC voltage in one embodiment;

[0012] Figure 2 It is a circuit schematic diagram of the input circuit in one embodiment;

[0013] Figure 3 It is a structural schematic diagram of an anti-squeal capacitor in the prior art;

[0014] Figure 4 It is a structural schematic diagram of another anti-squeal capacitor in the prior art;

[0015] Figure 5 It is a circuit schematic diagram of a high-power adaptive circuit for reducing capacitor squeal in one embodiment of the present invention.

Specific Embodiments

[0016] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0017] The so-called "one embodiment" or "embodiment" herein refers to specific features, structures, or characteristics that can be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments. Unless otherwise specified, the words indicating electrical connection such as "coupled", "connected", "joined", and "connected" in this article all mean directly or indirectly connected. For example, when A is connected to B, it includes both A and B being directly electrically connected, and also A being connected to B through electrical components or circuits.

[0018] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "front", "back", "left", "right", "vertical", "perpendicular", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0019] Please refer toFigure 5 As shown, it is a circuit schematic diagram of a high-power adaptive circuit for reducing capacitor crosstalk in an embodiment of the present invention. Figure 5 The high-power adaptive circuit for reducing capacitor crosstalk shown includes an MOS transistor (metal oxide semiconductor, abbreviated as field effect transistor) Q1, a first voltage conversion circuit 520, a second voltage conversion circuit 530, a triode Q5, and a switch control circuit 540.

[0020] The input power supply terminal VIN is connected to node A; the first connection terminal of the MOS transistor Q1 is connected to node A, its second connection terminal is connected to node B, and its control terminal is connected to node D; the input terminal of the first voltage conversion circuit is connected to node A, the output terminal of the first voltage conversion circuit is connected to node C, and the first voltage conversion circuit steps down the voltage at its input terminal by a first predetermined voltage and then outputs it. The input terminal of the second voltage conversion circuit is connected to node B, the output terminal of the second voltage conversion circuit is connected to node G, and the second voltage conversion circuit steps down the voltage at its input terminal by a second predetermined voltage and then outputs it. The first connection terminal of the triode Q5 is connected to node G, its control terminal is connected to node C, and its second connection terminal is connected to node F. The input terminal of the switch control circuit is connected to node F, and the output terminal of the switch control circuit is connected to node D. The first predetermined voltage is greater than the second predetermined voltage, so that the voltages at node G and node C are close. For example, the first predetermined voltage can be equal to the sum of the second predetermined voltage and the conduction voltage of the body diode of the MOS transistor Q1. For example, the first predetermined voltage is 1.4V, the second predetermined voltage is 0.7V, and the conduction voltage of the body diode of the MOS transistor Q1 is 0.7V.

[0021] When no superimposed AC voltage appears at the input power supply terminal VIN, the voltage difference between the output voltage of the first voltage conversion circuit and the output voltage of the second voltage conversion circuit causes the triode Q5 to turn off, that is, the voltage difference between node G and node C is less than the turn-on voltage value of the triode Q5, so that the triode Q5 is turned off. When the triode Q5 is turned off, the switch control circuit controls the MOS transistor Q1 to turn on, and the circuit can operate normally.

[0022] When an AC voltage is superimposed on the input power supply terminal VIN, the voltage difference between the output terminal of the first voltage conversion circuit and the output terminal of the second voltage conversion circuit causes the triode Q5 to conduct, that is, the voltage difference between the node G and the node C is greater than the turn-on voltage value of the triode Q5, so that the triode Q5 conducts. When the triode Q5 conducts, the switch control circuit controls the MOS transistor Q1 to turn off, so that the conduction channel of the MOS transistor Q1 is closed, and the voltage at the back end of the MOS transistor Q1 will not fluctuate with the input power supply, thereby reducing the ripple voltage superimposed on both ends of the capacitor and reducing the effect of the capacitor generating a howling sound.

[0023] As Figure 5 shown, the first voltage conversion circuit 520 includes a triode Q2, a triode Q4, and a resistor R1. The first connection end of the triode Q2 is used as the input end of the first voltage conversion circuit and is connected to the node A, and its control end is connected to its second connection end; the first connection end of the triode Q4 is connected to the second connection end of the triode Q2, its control end is used as the output end of the first voltage conversion circuit and is connected to the node C, its second connection end is grounded through the resistor R1, and its second connection end is connected to its control end.

[0024] As Figure 5 shown, the second voltage conversion circuit 530 includes a triode Q3 and a capacitor C6. The first connection end of the triode Q3 is used as the input end of the second voltage conversion circuit and is connected to the node B, its second connection end is connected to its control end, its second connection end is used as the input end of the second voltage conversion circuit and is connected to the node G, and one end of the capacitor C6 is connected to the control end of the triode Q3, and the other end is grounded.

[0025] As Figure 5 shown, the switch control circuit 540 includes a triode Q6, resistors R2, R3, R5, R6, R7 and R8, a triode Q7, and a resistor R4. The first connection end of the triode Q6 is connected to the input power supply terminal VIN through the resistor R2, its control end is connected to the node H, and its second connection end is grounded; one end of the resistor R3 is connected to the node H, and the other end is connected to the node F; one end of the resistor R6 is connected to the node H, and the other end is grounded; one end of the resistor R8 is connected to the node F, and the other end is grounded; one end of the resistor R4 is connected to the node A, and the other end is connected to the node D; the first connection end of the triode Q7 is connected to the node D, its control end is connected to the node E, and its second connection end is grounded; one end of the resistor R5 is connected to the node E, and the other end is connected to the first connection end of the triode Q6; one end of the resistor R7 is connected to the node E, and the other end is grounded.

[0026] In Figure 5In the specific embodiment shown, the MOS transistor (or field effect transistor) Q1 is a PMOS transistor. The first connection end, the second connection end, and the control end of the MOS transistor Q1 are the drain D, the source S, and the gate G of the PMOS transistor respectively; the triode Q2 is a PNP type triode. The first connection end, the second connection end, and the control end of the triode Q2 are the emitter, the collector, and the base of the PNP type triode respectively; the triode Q3 is a PNP type triode. The first connection end, the second connection end, and the control end of the triode Q3 are the emitter, the collector, and the base of the PNP type triode respectively; the triode Q4 is a PNP type triode. The first connection end, the second connection end, and the control end of the triode Q4 are the emitter, the collector, and the base of the PNP type triode respectively; the triode Q5 is a PNP type triode. The first connection end, the second connection end, and the control end of the triode Q5 are the emitter, the collector, and the base of the PNP type triode respectively; the triode Q6 is an NPN type triode. The first connection end, the second connection end, and the control end of the triode Q6 are the collector, the emitter, and the base of the NPN type triode respectively; the triode Q7 is an NPN type triode. The first connection end, the second connection end, and the control end of the triode Q7 are the collector, the emitter, and the base of the NPN type triode respectively.

[0027] Figure 5 The high-power adaptive circuit for reducing capacitor crosstalk shown also includes a zener diode D21. The negative electrode of the zener diode D1 is connected to node B, and its positive electrode is connected to node D. Among them, the zener diode D1 plays a role in protecting the MOS transistor (or field effect transistor) Q1, preventing the voltage between the gate and the source of the MOS transistor Q1 from exceeding the rated voltage value (or exceeding the withstand voltage value between the gate and the source of the MOS transistor). Specifically, when the power supply generates a pulse, the voltage between node B and node D will not be too high, exceeding the withstand voltage value between the source and the gate of the MOS transistor (or field effect transistor) Q1 and burning out the MOS transistor (or field effect transistor) Q1. It can also be said that the operating voltage value of the zener diode D1 is greater than the turn-on voltage value of the MOS transistor Q1 and less than the maximum rated voltage value between the gate and the source of the MOS transistor Q1, where the turn-on voltage value of the MOS transistor Q1 is less than the maximum rated voltage value between the gate and the source of the MOS transistor Q1.

[0028] Figure 5 The high-power adaptive circuit for reducing capacitor crosstalk shown also includes a capacitor C1 and a filter circuit 510. One end of the capacitor C1 is connected to node A, and the other end is grounded. The capacitor C1 is a port filter and an ESD (Electro-Static discharge, that is, electrostatic discharge) protection capacitor. The filter circuit 510 is connected between node B and the output power supply terminal VOUT; the filter circuit 510 includes a capacitor. In Figure 5In the specific embodiment shown, the filter circuit 510 includes an inductor L1, a capacitor C2, and one or more output capacitors. For example, the output capacitors include a capacitor C3, a capacitor C4, and a capacitor C5. One end of the inductor L1 is connected to node B, and the other end is connected to the output power supply terminal VOUT; one end of the capacitor C2 is connected to node B, and the other end is grounded. One end of each output capacitor is connected to the output power supply terminal VOUT, and the other end is grounded. Specifically, one end of the capacitor C3 is connected to the output power supply terminal VOUT, and the other end is grounded; one end of the capacitor C4 is connected to the output power supply terminal VOUT, and the other end is grounded; one end of the capacitor C5 is connected to the output power supply terminal VOUT, and the other end is grounded. This part of the circuit is the noise filter circuit of the input power supply terminal VIN, which enables the EMC test (i.e., electromagnetic compatibility test) results to meet the standard requirements and is an inevitable part in circuit design.

[0029] When there is no superimposed AC voltage at the input power supply terminal VIN, the voltage at node A is the input voltage value. The voltage at node A can pass through the body diode of the triode Q2, from the emitter to the base of the triode Q2, so that the voltage ratio between the base and the collector of the triode Q2 is 0.7V lower than the emitter voltage (at Figure 5In the specific embodiments shown, the voltage drops across the internal body diodes of the triode and the field effect transistor are all considered to be 0.7V. The actual voltage drop needs to be determined according to the selection of the triode and the field effect transistor). Similarly, the voltage between the base and the collector of the triode Q4 is 0.7V lower than the emitter voltage. Therefore, the voltage at node C is 1.4V lower than the voltage at node A. The resistor R1 is a current-limiting resistor that limits the current flowing through the triodes Q2 and Q4. The voltage at node A reaches node B through the body diode of the MOS transistor (or field effect transistor) Q1. Therefore, the voltage at node B is 0.7V lower than the voltage at node A. Similarly, the voltage between the base and the collector of the triode Q3 is 0.7V lower than the emitter voltage. Therefore, the voltage at node G is 1.4V lower than the voltage at node A, so that the voltage at node G is equal to the voltage at node C, that is, the emitter voltage of the triode Q5 is equal to the base voltage, and the triode Q5 is not turned on. (In practical applications, according to the selection of the triode and the field effect transistor, there will be a deviation between the voltage at node C and the voltage at node G, but there will not be a situation where the voltage at node G is about 0.7V higher than the voltage at node V. That is to say, when there is no superimposed AC voltage at the input power supply terminal VIN, the voltage difference between node G and node C is less than the turn-on voltage value of the triode Q5, so that the triode Q5 is turned off). Therefore, node F is at a low level, and the voltage at node F is less than the turn-on voltage value of the triode Q6, and the triode Q6 is not turned on. Since the selection of the resistors R2, R5, and R7 needs to meet the condition that when the triode Q6 is not turned on, the voltage at node E is greater than the turn-on voltage value of the triode Q7, the triode Q7 is turned on, so node D is at a low level. The resistor R4 is a current-limiting resistor that limits the current flowing through the triode Q7. Since node B is at a high level, the voltage between node B and node D is greater than the turn-on voltage value of the field effect transistor Q1. Therefore, the field effect transistor Q1 is turned on. The input power supply terminal VIN is transmitted to the output power supply terminal VOUT through the field effect transistor Q1 and the inductor L1, and the circuit can work normally.

[0030] When there is an AC voltage superimposed on the input power supply terminal VIN, the voltage at node A fluctuates with the power supply voltage, resulting in a decrease in the voltage at node A. Since the capacitance at the back end of node B is large, the voltage at node B can be maintained, causing the voltage at node B to decrease more slowly than that at node A. After the voltage at node A decreases by 1V, since the voltage at node B decreases more slowly than that at node A, the voltage at node C is about 2.1V lower than that at node A and the voltage at node G is about 1.4V lower than that at node A. As a result, the voltage at node G is about 0.7V higher than the voltage at node C, so the triode Q5 conducts. That is to say, when there is an AC voltage superimposed on the input power supply terminal VIN, the voltage difference between node G and node C is greater than the turn-on voltage value of the triode Q5, causing the triode Q5 to conduct. Since the selection of resistors R3 and R6 needs to meet the condition that when the triode Q5 conducts, the voltage at node H is greater than the turn-on voltage value of the triode Q6, the triode Q6 conducts, so node E is at a low level, and the voltage at node E is less than the turn-on voltage value of the triode Q7, so the triode Q7 turns off. When the triode Q7 does not conduct (i.e., turns off), node D is at a high level. At this time, the voltage between node B and node D is less than the turn-on voltage value of the field effect transistor Q1, so the field effect transistor Q1 turns off, and thus the conductive channel of the field effect transistor Q1 closes (or turns off). The voltage of the capacitor at the back end of the field effect transistor Q1 does not fluctuate with the input power supply, thereby reducing the ripple voltage superimposed on both ends of the capacitor and reducing the effect of the capacitor generating a howling sound.

[0031] In summary, it can be seen that Figure 5 In the high-power adaptive circuit for reducing capacitor howling shown, when there is no AC voltage superimposed on the input power supply terminal VIN, the triode Q5 and the triode Q6 are turned off, and the triode Q7 and the MOS transistor Q1 are turned on; when there is an AC voltage superimposed on the input power supply terminal VIN, the triode Q5 and the triode Q6 are turned on, and the triode Q7 and the MOS transistor Q1 are turned off.

[0032] Compared with the prior art, the high-power adaptive circuit for reducing capacitor howling provided by the present invention has the following beneficial effects:

[0033] 1. The high-power adaptive circuit for reducing capacitor howling provided by the present invention does not require external control and can adaptively adjust the circuit state according to the input power supply situation.

[0034] 2. The high-power adaptive circuit for reducing capacitor howling provided by the present invention is built using discrete components and has a low cost.

[0035] It should be noted that any modifications made by those skilled in the art to the specific embodiments of the present invention do not depart from the scope of the claims of the present invention. Correspondingly, the scope of the claims of the present invention is not limited solely to the foregoing specific embodiments.

Claims

1. An adaptive circuit for reducing capacitor howling, characterized in that: It includes a MOS tube Q1, a first voltage conversion circuit, a second voltage conversion circuit, a transistor Q5, and a switch control circuit. The input power supply terminal VIN is connected to the node A; the first connection terminal of the MOS tube Q1 is connected to the node A, the second connection terminal thereof is connected to the node B, and the control terminal thereof is connected to the node D; The input end of the first voltage conversion circuit is connected to the node A, the output end of the first voltage conversion circuit is connected to the node C, the first voltage conversion circuit steps down the voltage at its input end to a first predetermined voltage and then outputs it, the input end of the second voltage conversion circuit is connected to the node B, the output end of the second voltage conversion circuit is connected to the node G, the second voltage conversion circuit steps down the voltage at its input end to a second predetermined voltage and then outputs it, The first connection end of the transistor Q5 is connected to the node G, the control end thereof is connected to the node C, and the second connection end thereof is connected to the node F; The input end of the switch control circuit is connected to the node F, and the output end of the switch control circuit is connected to the node D; When the transistor Q5 is turned off, the switch control circuit controls the MOS transistor Q1 to be turned on, and when the transistor Q5 is turned on, the switch control circuit controls the MOS transistor Q1 to be turned off.

2. The adaptive circuit for reducing capacitor howling according to claim 1, characterized in that: When the input power supply terminal VIN does not have a superimposed AC voltage, the voltage difference between the voltage at the output terminal of the first voltage conversion circuit and the voltage at the output terminal of the second voltage conversion circuit causes the transistor Q5 to be disconnected; When a superimposed AC voltage appears at the input power supply terminal VIN, the voltage difference between the voltage at the output terminal of the first voltage conversion circuit and the voltage at the output terminal of the second voltage conversion circuit causes the transistor Q5 to be turned on.

3. The adaptive circuit for reducing capacitor howling according to claim 2, characterized in that: The first voltage conversion circuit includes a transistor Q2, a transistor Q4, and a resistor R1, wherein the first connection end of the transistor Q2 is connected to the node A as an input end of the first voltage conversion circuit, and the control end thereof is connected to its second connection end; the first connection end of the transistor Q4 is connected to the second connection end of the transistor Q2, and the control end thereof is connected to the node C as an output end of the first voltage conversion circuit, and the second connection end thereof is grounded via the resistor R1, and the second connection end thereof is connected to its control end; The second voltage conversion circuit includes a transistor Q3 and a capacitor C6, wherein a first connection end of the transistor Q3 is connected to the node B as an input end of the second voltage conversion circuit, a second connection end is connected to its control end, and a second connection end is connected to the node G as an input end of the second voltage conversion circuit, one end of the capacitor C6 is connected to the control end of the transistor Q3, and the other end is grounded. The switch control circuit includes a transistor Q6, a resistor R2, a resistor R3, a resistor R5, a resistor R6, a resistor R7 and a resistor R8, a transistor Q7 and a resistor R4, wherein a first connection end of the transistor Q6 is connected to an input power supply end VIN via the resistor R2, a control end thereof is connected to a node H, and a second connection end thereof is grounded; one end of the resistor R3 is connected to the node H, and the other end thereof is connected to a node F; one end of the resistor R6 is connected to the node H, and the other end thereof is grounded; one end of the resistor R8 is connected to the node F, and the other end thereof is grounded; one end of the resistor R4 is connected to the node A, and the other end thereof is connected to the node D; a first connection end of the transistor Q7 is connected to the node D, a control end thereof is connected to the node E, and the second connection end thereof is grounded; one end of the resistor R5 is connected to the node E, and the other end thereof is connected to the first connection end of the transistor Q6; one end of the resistor R7 is connected to the node E, and the other end thereof is grounded.

4. The adaptive circuit for reducing capacitor howling according to claim 3, characterized in that: The MOS transistor Q1 is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the MOS transistor Q1 are respectively the drain, the source and the gate of the PMOS transistor; The transistor Q2 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q2 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q3 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q3 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q4 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q4 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q5 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q5 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q6 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q6 are respectively the collector, the emitter and the base of the NPN transistor; The transistor Q7 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q7 are respectively the collector, the emitter and the base of the NPN transistor.

5. The adaptive circuit for reducing capacitor howling according to claim 3, characterized in that: When the input power supply terminal VIN does not have a superimposed AC voltage, the voltage difference between the node G and the node C is less than the turn-on voltage value of the transistor Q5, so that the transistor Q5 is turned off, and then the transistor Q6 is turned off, the transistor Q7 is turned on, and finally the MOS transistor Q1 is turned on; When a superimposed AC voltage appears at the input power supply terminal VIN, the voltage difference between the node G and the node C is greater than the turn-on voltage value of the transistor Q5, so that the transistor Q5 is turned on, and then the transistor Q6 is turned on, the transistor Q7 is turned off, and finally the MOS transistor Q1 is turned off.

6. The adaptive circuit for reducing capacitor howling according to claim 5, characterized in that: The resistance values ​​of the resistor R2, the resistor R5 and the resistor R7 are selected to satisfy: when the transistor Q6 is turned off, the voltage of the node E is greater than the turn-on voltage value of the transistor Q7; The resistance values ​​of the resistor R3 and the resistor R6 are selected to satisfy the following requirement: when the transistor Q5 is turned on, the voltage at the node H is greater than the turn-on voltage value of the transistor Q6.

7. The adaptive circuit for reducing capacitor howling according to claim 3, characterized in that: It also includes a Zener diode D1, The cathode of the voltage stabilizing diode D1 is connected to the node B, and the anode of the voltage stabilizing diode D1 is connected to the node D; The operating voltage value of the voltage stabilizing diode D1 is greater than the turn-on voltage value of the MOS transistor Q1 and less than the maximum rated voltage value between the gate and the source of the MOS transistor Q1; The turn-on voltage value of the MOS transistor Q1 is less than the maximum rated voltage value between the gate and the source of the MOS transistor Q1.

8. The adaptive circuit for reducing capacitor howling according to claim 1, characterized in that: It also includes a filter circuit, The filter circuit is connected between the node B and the output power supply terminal VOUT; The filter circuit includes a capacitor.

9. The adaptive circuit for reducing capacitor howling according to claim 8, characterized in that: The filter circuit includes an inductor L1, a capacitor C2, and one or more output capacitors. One end of the inductor L1 is connected to the node B, and the other end thereof is connected to the output power supply terminal VOUT; One end of the capacitor C2 is connected to the node B, and the other end thereof is grounded; One end of each output capacitor is connected to the output power supply terminal VOUT, and the other end thereof is grounded.

10. The adaptive circuit for reducing capacitor howling according to claim 8, characterized in that: It also includes capacitor C1, One end of the capacitor C1 is connected to the node A, and the other end thereof is grounded.

Images