Control circuit for reducing howling of capacitor

Abstract

The utility model provides a control circuit for reducing capacitor howling, comprising a voltage sampling circuit, the input end of which is connected with a node A, the output end of which outputs a sampling voltage, the node A is connected with an input power supply end, and the voltage sampling circuit is used for collecting the voltage of the node A and outputting the sampling voltage based on the voltage of the node A; the input end of the master control circuit is connected with the output end of the voltage sampling circuit, and the output end of the master control circuit outputs control signals; each capacitor howling suppression circuit comprises a capacitor, a switching device and a first resistor, one end of the capacitor is connected with the node A, and the other end of the capacitor is connected with the first connecting end of the switching device; the second connecting end of the switching device is grounded, the control end of the switching device is connected with the output end of the master control circuit, one end of the first resistor is connected with the first connecting end of the switching device, and the other end of the first resistor is connected with the second connecting end of the switching device. Compared with the prior art, the circuit provided by the utility model is lower in cost, higher in reliability, and better in effect of suppressing the squeal of the capacitor.

Description

Technical field

[0001] The utility model relates to the technical field of circuit design, in particular to a control circuit for reducing capacitor howling. [Background Technology]

[0002] In the automotive electrical system, AC voltage will be superimposed on the input power side. Ripple voltage of a certain frequency will appear in the entire operating system along with the input power of the car, such as Figure 1 As shown in FIG, it is a waveform diagram of an AC voltage superimposed on the input power supply in one embodiment. When the chip capacitor in the circuit is subjected to AC voltage, it will exhibit a special physical phenomenon. It will be deformed in a certain direction due to external force. When the frequency of the AC voltage reaches a certain value, it will generate mechanical vibration, thereby making a sound, which is the capacitor whine phenomenon. Please refer to Figure 2 As shown in FIG, it is a circuit diagram of a DC-to-DC converter circuit (DC-to-DC converter) in the prior art. According to the characteristics of the DC-DC converter circuit, the DC-DC chip will generate ripple voltage at the input and output ends during operation, which will increase the AC voltage value superimposed on the input power side, and increase the AC voltage across the capacitor connected to the input end, so that the capacitor howling situation will be worse.

[0003] During product use, capacitor howling will affect the user experience. Especially in the automotive field, abnormal noises during driving will affect the driver's attention and may cause traffic accidents. Therefore, it is necessary to suppress capacitor howling and reduce the decibel of capacitor howling.

[0004] Currently, there are the following solutions to capacitor whistling: ① Support the capacitor by means of a bracket, and use the elasticity of the metal terminal to relieve stress, thereby reducing the degree of capacitor whistling. Figure 3 ② Place chip capacitors of the same specifications symmetrically at the same position on both sides of the PCB board to reduce the degree of howling by offsetting the vibration of the two capacitors. Figure 4 As shown in FIG, it is a structural diagram of another anti-howling capacitor in the prior art.

[0005] Among them, the disadvantages of the existing technical solution ① are: the use of bracket capacitors is high in cost and has a large package size. The disadvantages of the existing technical solution ② are: the degree of reducing capacitor whistle is limited, and it is related to the welding process, the degree of patch symmetry, etc., and there may be cases where the capacitor whistle cannot be effectively reduced.

[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 invention is to provide a control circuit for reducing capacitor howling, which has low cost, high reliability, and better effect of suppressing capacitor howling.

[0008] According to one aspect of the present invention, the present invention provides a control circuit for reducing capacitor howling, which includes: a voltage sampling circuit, whose input end is connected to node A, and whose output end outputs a sampling voltage, the node A is connected to the input power supply end VIN, the voltage sampling circuit is used to collect the voltage of the node A, and output the sampling voltage based on the voltage of the node A; a main control circuit, whose input end is connected to the output end of the voltage sampling circuit, and whose output end outputs a control signal, the main control circuit outputs the control signal based on the sampling voltage; several capacitor howling suppression circuits, the capacitor howling suppression circuit includes a capacitor, a switching device and a first resistor, one end of the capacitor is connected to the node A, and the other end is connected to the first connection end of the switching device; the second connection end of the switching device is grounded, and its control end is connected to the output end of the main control circuit, one end of the first resistor is connected to the first connection end of the switching device, and the other end is connected to the second connection end of the switching device.

[0009] Compared with the prior art, the present invention has lower cost, higher reliability, and better effect of suppressing capacitor howling.

Brief Description of the Drawings

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work. Among them:

[0011] Figure 1 A waveform diagram showing a superimposed AC voltage on an input power supply in one embodiment;

[0012] Figure 2 A circuit diagram of a DC-DC conversion circuit in the prior art;

[0013] Figure 3 This is a schematic diagram of the structure of an anti-howling capacitor in the prior art;

[0014] Figure 4 Schematic diagram of the structure of another anti-howling capacitor in the prior art;

[0015] Figure 5 1 is a circuit diagram of a control circuit for reducing capacitor howling in one embodiment of the present invention;

[0016] Figure 6 This is a logic flow chart for determining whether an AC voltage is superimposed on the input power terminal VIN based on a sampled voltage in one embodiment of the present invention;

[0017] Figure 7 In one embodiment, Figure 2 The capacitor howling test waveform of a DC-DC conversion circuit in the prior art is shown;

[0018] Figure 8 In one embodiment, Figure 5 The capacitive noise test waveform of the control circuit for reducing capacitive noise is shown. [Specific implementation method]

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the terms "coupled," "connected," "connected," and "connected" used herein to indicate electrical connection refer to direct or indirect connection. For example, "A and B are connected" includes both direct electrical connection between A and B and connection between A and B through electrical components or circuits.

[0021] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "front", "back", "left", "right", "vertical", "perpendicular", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0022] Please refer to Figure 5 , which is a circuit diagram of a control circuit for reducing capacitor howling in one embodiment of the present invention. Figure 5 The control circuit for reducing capacitive howling shown includes a voltage sampling circuit 510 , a main control circuit U2 , and several capacitive howling suppression circuits (eg, capacitive howling suppression circuits 520 , 530 , 540 ).

[0023] The input power supply terminal VIN is connected to the node A; the input terminal of the voltage sampling circuit 510 is connected to the node A, and its output terminal outputs the sampling voltage. The voltage sampling circuit 510 is used to collect the voltage of the node A and output the sampling voltage based on the voltage of the node A. Figure 5 In the illustrated embodiment, voltage sampling circuit 510 includes resistors R5 and R8. Resistor R5 has one end connected to node A and the other end connected to node B. Resistor R8 has one end connected to node B and the other end connected to ground. Node B is the output of voltage sampling circuit 510, and the voltage at node B is the sampled voltage. Furthermore, voltage sampling circuit 510 includes capacitor C8, one end of which is connected to node B and the other end is grounded.

[0024] The input end of the main control circuit U2 is connected to the output end of the voltage sampling circuit 510, and its output end C outputs a control signal Control, wherein the main control circuit U2 outputs the control signal Control based on the sampled voltage output by the voltage sampling circuit 510. Figure 5 In the specific embodiment shown, the main control circuit U2 is an MCU (Microcontroller Unit), and its input end is an ADC (analog-to-digital converter) pin.

[0025] exist Figure 5In the illustrated embodiment, the plurality of capacitive howling suppression circuits include a first capacitive howling suppression circuit 520, a second capacitive howling suppression circuit 530, and a third capacitive howling suppression circuit 540. The first capacitive howling suppression circuit 520 includes a capacitor C3, a capacitor C4, a switch device Q2, and a first resistor R3, wherein one end of the capacitor C3 is connected to the node A, and the other end thereof is connected to the first connection end of the switch device Q2; one end of the capacitor C4 is connected to the node A, and the other end thereof is connected to the first connection end of the switch device Q2; the second connection end of the switch device Q2 is grounded, and the control end thereof is connected to the output end C of the main control circuit U2; and one end of the first resistor R3 is connected to the first connection end of the switch device Q2, and the other end thereof is connected to the second connection end of the switch device Q2. The second capacitive howling suppression circuit 530 includes a capacitor C5, a capacitor C6, a capacitor C7, a switching device Q3 and a first resistor R4, wherein one end of the capacitor C5 is connected to the node A, and the other end thereof is connected to the first connection end of the switching device Q3; one end of the capacitor C6 is connected to the node A, and the other end thereof is connected to the first connection end of the switching device Q3; one end of the capacitor C7 is connected to the node A, and the other end thereof is connected to the first connection end of the switching device Q3; the second connection end of the switching device Q3 is grounded, and its control end is connected to the output end C of the main control circuit U2; one end of the first resistor R4 is connected to the first connection end of the switching device Q3, and the other end thereof is connected to the second connection end of the switching device Q3. The third capacitive howling suppression circuit 540 includes a capacitor C1, a switching device Q1 and a first resistor R1, wherein one end of the capacitor C1 is connected to the node A, and the other end thereof is connected to the first connection end of the switching device Q1; the second connection end of the switching device Q1 is grounded, and its control end is connected to the output end C of the main control circuit U2; one end of the first resistor R1 is connected to the first connection end of the switching device Q1, and the other end thereof is connected to the second connection end of the switching device Q1.

[0026] exist Figure 5 In the specific embodiment shown, the switching device Q2 is an NMOS transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device Q2 are the drain, source, and gate of the NMOS transistor, respectively. The first capacitive howling suppression circuit 520 also includes a second resistor R6, one end of the second resistor R6 is connected to the control terminal of the switching device Q2, and the other end thereof is grounded; the switching device Q3 is an NMOS transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device Q3 are the drain, source, and gate of the NMOS transistor, respectively. The second capacitive howling suppression circuit 530 also includes a second resistor R7, one end of the second resistor R7 is connected to the control terminal of the switching device Q2, and the other end thereof is grounded; the switching device Q1 is an NMOS transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device Q1 are the drain, source, and gate of the NMOS transistor, respectively. The third capacitive howling suppression circuit 540 also includes a second resistor R2, one end of the second resistor R2 is connected to the control terminal of the switching device Q1, and the other end thereof is grounded.

[0027] From the above description of the first capacitor howling suppression circuit 520, the second capacitor howling suppression circuit 530 and the third capacitor howling suppression circuit 540, it can be seen that each capacitor howling suppression circuit in the present invention includes a capacitor, a switching device and a first resistor, one end of the capacitor is connected to the node A, and the other end is connected to the first connection end of the switching device; the second connection end of the switching device is grounded, and its control end is connected to the output end C of the main control circuit U2, one end of the first resistor is connected to the first connection end of the switching device, and the other end is connected to the second connection end of the switching device. In a specific embodiment of the present invention, the switching device is an NMOS tube, and the first connection end, the second connection end and the control end of the switching device are the drain, source and gate of the NMOS tube respectively; the capacitor howling suppression circuit also includes a second resistor, one end of the second resistor is connected to the control end of the switching device, and the other end is grounded. The capacitor includes one capacitor or multiple capacitors in parallel. For example, in the first capacitor howling suppression circuit 520, it includes two parallel capacitors C3 and C4; in the second capacitor howling suppression circuit 530, it includes three parallel capacitors C5, C6 and C7; in the third capacitor howling suppression circuit 540, it includes one capacitor C1.

[0028] exist Figure 5 In the illustrated embodiment, the control circuit for reducing capacitor noise further includes a DC-DC conversion module (i.e., a DCDC chip) U1, whose input terminal Vin_dcdc is connected to node A, and whose output terminal Vout_dcdc is connected to the output power terminal VOUT. The DC-DC conversion module U1 is configured to convert a first DC power supply into a second DC power supply. This is a technical detail well known to those skilled in the art and will not be further described herein.

[0029] exist Figure 5In the illustrated embodiment, the control circuit for reducing capacitor howling further includes an inductor L1, one end of which is connected to node A, and the other end of which is connected to the input terminal Vin_dcdc of the DC-DC conversion module U1. Capacitors C3 and C4 in the first capacitor howling suppression circuit 520 have one end connected to node A, and capacitors C5, C6, and C7 in the second capacitor howling suppression circuit 530 have one end connected to the input terminal Vin_dcdc of the DC-DC conversion module U1 (or capacitors C5, C6, and C7 in the second capacitor howling suppression circuit 530 have one end connected to node A via the inductor L1). The first capacitor howling suppression circuit 520, the second capacitor howling suppression circuit 530, and the inductor L1 form an input filter circuit for the DC-DC conversion module U1. This input filter circuit ensures that EMC (Electromagnetic Compatibility) test results meet standard requirements and is an inevitable part of circuit design. It should be noted that, in other embodiments, the input filter circuit of the DC-DC conversion module U1 may also be other filter circuits including a capacitor howling suppression circuit.

[0030] exist Figure 5 In the illustrated embodiment, the control circuit for reducing capacitive howling further includes a module circuit 550 connected to node A. One end of capacitor C1 in the third capacitive howling suppression circuit 540 is connected to the input end of the module circuit 550. The third capacitive howling suppression circuit 540 forms an input filter circuit of the module circuit 570. It should be noted that in other embodiments, the input filter circuit of the module circuit 570 may also be other filter circuits including a capacitive howling suppression circuit.

[0031] exist Figure 5 In the embodiment shown, the control circuit for reducing capacitor noise further includes an output filter circuit 560, which is connected between the output terminal Vout_dcdc of the DC-DC converter module U1 and the output power terminal VOUT. The output filter circuit 560 can reduce the ripple of the output voltage of the DC-DC converter module U1 and is an inevitable part in circuit design. Figure 5 In the illustrated embodiment, the output filter circuit 560 includes an inductor L2 and a capacitor C2. One end of the inductor L2 is connected to the output terminal Vout_dcdc of the DC-DC converter module U1, and the other end is connected to the output power terminal VOUT. One end of the capacitor C2 is connected to the other end of the inductor L2, and the other end is grounded. In other embodiments, the output filter circuit 560 may also be another filter circuit including a capacitor.

[0032] exist Figure 5In the illustrated embodiment, the control circuit for reducing capacitor noise further includes a reverse polarity protection diode D1 , wherein the positive electrode of the reverse polarity protection diode D1 is connected to the input power terminal VIN, and the negative electrode thereof is connected to the node A. The reverse polarity protection diode D1 provides reverse polarity protection when the input power terminal VIN is reversely connected.

[0033] The following is a detailed introduction Figure 5 The working principle of the control circuit for reducing capacitor howling is shown.

[0034] When the main control circuit U2 detects, based on the sampled voltage, that the voltage at the input power terminal VIN is greater than a preset turn-on voltage (i.e., a preset voltage, which can be set as required) and that no AC voltage is superimposed on the input power terminal VIN, the main control circuit U2 controls the control signal Control outputted by its output terminal C to a high level, turning on MOS transistors Q1, Q2, and Q3. Since the on-resistance of MOS transistors Q1, Q2, and Q3 is very small, the parallel resistors are bypassed. Therefore, the first resistors R1, R3, and R4 are bypassed, and capacitor C1 is connected to ground terminal GND through MOS transistor Q1. Capacitors C3 and C4 are connected to ground terminal GND through MOS transistor Q2. Capacitors C5, C6, and C7 are connected to ground terminal GND through MOS transistor Q3. Since the on-resistance of the MOS transistors is very close to the ESR (equivalent series resistance) of the capacitors, the conduction of MOS transistors Q1, Q2, and Q3 does not affect circuit operation.

[0035] That is to say, when the main control circuit U2 detects that the voltage of the input power terminal VIN is greater than the preset start-up voltage (that is, the preset voltage, which can be set according to requirements) based on the sampling voltage output by the voltage sampling circuit 510 and the input power terminal VIN is not superimposed with an AC voltage, the control signal Control output by the main control circuit U2 turns on the switching devices Q2, Q3, and Q4 in the capacitive howling suppression circuits 520, 530, and 540, and the circuit can operate normally.

[0036] When the input power supply terminal VIN has a superimposed AC voltage phenomenon, the voltage of the input power supply terminal VIN will be in a fluctuating state. The main control circuit U2 can detect the input voltage of its input terminal ADC (which is equal to the sampling voltage) through software, and control the control signal control output from its output terminal C to a low level through judgment logic. The specific judgment logic is as follows: Figure 6 shown.

[0037] Figure 6 This is a logic flow chart for determining whether an AC voltage is superimposed on the input power terminal VIN based on a sampled voltage in one embodiment of the present invention. Figure 6The judgment logic shown for judging whether an AC voltage is superimposed on the input power terminal VIN based on the sampled voltage includes the following steps.

[0038] Step 610: Calculate the maximum value VIN_filter_max and the minimum value VIN_filter_min in VIN_filter[n]; and calculate the average value VIN_filter_average of all VIN_filter[n] within 1 second. It should be noted in step 610 that the arrays VIN_filter[0] to VIN_filter[n] store the VS voltage filter data collected by the main control circuit U2 (i.e., MCU) within 1 second. The data at the next moment is stored in VIN_filter[n], and the data of VIN_filter[0] is overwritten by VIN_filter[1].

[0039] Step 620 : Determine whether VIN_filter_max − VIN_filter_min < 1v. If not, return to step 610 ; if yes, proceed to step 630 .

[0040] Step 630: Calculate the maximum value (VIN_original_max) and minimum value (VIN_original_min) of VIN_original[m] within 3 seconds. Note that in step 630, similarly to VIN_filter[n], VIN_original[0] should be collected after the last data of VIN_filter[n]. VIN_original[m] stores 3 consecutive seconds of voltage data.

[0041] Step 640: Determine whether all of the following conditions are met simultaneously:

[0042] ①VIN_original_max-VIN_filter_average>1v;

[0043] ②VIN_filter_average-VIN_filter_min>1v;

[0044] ③VIN_original_max-VIN_filter_min>2V.

[0045] If not (No), return to step 610; if yes (Yes), execute step 650.

[0046] Step 650: MCU GPIO Control outputs a low level, that is, the control signal Contro outputted by the output terminal C of the main control circuit U2 is a low level, and then the process returns to step 610. The above parameters can be adjusted according to actual use requirements.

[0047] exist Figure 6 In the illustrated embodiment, VIN_filter_max is the maximum value in the VIN_filter[n] array, VIN_filter_min is the minimum value in the VIN_filter[n] array, VIN_filter_average is the average value in the VIN_filter[n] array, VIN_original_max is the maximum value in the VIN_original[n] array, and VIN_original_min is the minimum value in the VIN_original[n] array.

[0048] Figure 6 This is just a specific example of determining whether an AC voltage is superimposed on the input power terminal VIN based on the sampled voltage. Obviously, those skilled in the art can also determine whether an AC voltage is superimposed on the input power terminal VIN in other ways.

[0049] When the main control circuit U2 detects an AC voltage superimposed on the input power supply terminal VIN based on the sampled voltage, the main control circuit U2 controls the control signal Control outputted by its output terminal C to a low level. The MOS transistor Q1 is then turned off (or disconnected), and the capacitor C1 is connected to the ground terminal GND through the first resistor R1. Resistor R2 is a pull-down resistor, and resistor R2 and the junction capacitance of the MOS transistor Q1 form a discharge loop. The MOS transistor Q2 is turned off (or disconnected), and capacitors C3 and C4 are connected to the ground terminal GND through the first resistor R3. Resistor R6 is a pull-down resistor, and resistor R6 and the junction capacitance of the MOS transistor Q2 form a discharge loop. The MOS transistor Q3 is turned off (or disconnected), and capacitors C5, C6, and C7 are connected to the ground terminal GND through the first resistor R4. Resistor R7 is a pull-down resistor, and resistor R7 and the junction capacitance of the MOS transistor Q3 form a discharge loop. The resistance values of the first resistors R1, R3, and R4 are in the ohm range and need to be adjusted according to the actual circuit. When capacitor C1 passes through first resistor R1 to ground GND, since first resistor R1 is ohmic, when AC is superimposed on input power terminal VIN, the inrush current flowing through capacitor C1 will be reduced, thereby reducing the degree of howling of capacitor C1. Similarly, since first resistor R3 is ohmic, when AC is superimposed on input power terminal VIN, the inrush current flowing through capacitors C3 and C4 will be reduced, thereby reducing the degree of howling of capacitors C3 and C4. Since first resistor R4 is ohmic, when AC is superimposed on input power terminal VIN, the inrush current flowing through capacitors C5, C6, and C7 will be reduced, thereby reducing the degree of howling of capacitors C5, C6, and C7.

[0050] That is to say, when the main control circuit U2 detects that the voltage of the input power terminal VIN is greater than the preset turn-on voltage (that is, the preset voltage, which can be set according to demand) based on the sampling voltage output by the voltage sampling circuit 510 and the AC voltage is superimposed on the input power terminal VIN, the control signal Control output by the main control circuit U2 turns off the switching devices Q1, Q2, and Q3 in the capacitor howling suppression circuits 520, 530, and 540, and reduces the impact current flowing through the capacitors C1, C3, C4, C5, C6, and C7 through the first resistors R1, R3, and R4, thereby reducing the degree of capacitor howling.

[0051] It should be noted that since capacitor C8 is a filter capacitor for the ADC pin and has a capacitance in the nF range, capacitor noise is minimal. Therefore, there is no need to replace capacitor C8 with a capacitor noise suppression circuit to reduce capacitor noise. When the capacitance of capacitor C8 is greater than or equal to 1uF, capacitor noise will be more severe. Therefore, capacitor C8 needs to be equipped with a corresponding MOS transistor, a first resistor, and a second resistor to form a capacitor noise suppression circuit to reduce capacitor noise.

[0052] Please refer to Figure 7As shown, in one embodiment, Figure 2 The waveform diagram of the capacitor howling test of a DC-DC conversion circuit in the prior art is shown; please refer to Figure 8 As shown, in one embodiment, Figure 5 The capacitor noise test waveform diagram of the control circuit for reducing capacitor noise is shown in the figure. Figure 7 and Figure 8 The test data shows that Figure 5 The capacitive howling of the control circuit for reducing capacitive howling is shown is significantly reduced.

[0053] In summary, the control circuit for reducing capacitor howling provided by the present invention has the following beneficial effects:

[0054] 1. The cost of the control circuit for reducing capacitor howling provided by the utility model is low.

[0055] 2. Compared with the solution of symmetrically placing chip circuits of the same specifications at the same position on the front and back sides of the PCB board, the control circuit for reducing capacitor howling provided by the utility model is more reliable and can better suppress capacitor howling.

[0056] It should be noted that any changes 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. Accordingly, the scope of the claims of the present invention is not limited to the aforementioned specific embodiments.

Claims

1. A control circuit for reducing capacitor howling, characterized in that: It includes: a voltage sampling circuit, wherein an input terminal of the circuit is connected to a node A and an output terminal of the circuit outputs a sampled voltage, wherein the node A is connected to an input power supply terminal VIN, and the voltage sampling circuit is configured to collect the voltage of the node A and output the sampled voltage based on the voltage of the node A; a main control circuit, whose input end is connected to the output end of the voltage sampling circuit, and whose output end outputs a control signal, wherein the main control circuit outputs the control signal based on the sampled voltage; Several capacitive howling suppression circuits include a capacitor, a switching device and a first resistor, one end of the capacitor is connected to the node A, and the other end is connected to the first connection end of the switching device; the second connection end of the switching device is grounded, and the control end is connected to the output end of the main control circuit; one end of the first resistor is connected to the first connection end of the switching device, and the other end is connected to the second connection end of the switching device.

2. The control circuit for reducing capacitor howling according to claim 1, characterized in that: When the main control circuit detects based on the sampled voltage that the voltage of the input power terminal VIN is greater than a preset voltage and no AC voltage is superimposed on the input power terminal VIN, the control signal output by the main control circuit turns on the switch device in the capacitive howling suppression circuit; When the main control circuit detects based on the sampled voltage that the voltage of the input power terminal VIN is greater than a preset voltage and an AC voltage is superimposed on the input power terminal VIN, the control signal output by the main control circuit turns off the switch device in the capacitive howling suppression circuit.

3. The control circuit for reducing capacitor howling according to claim 2, characterized in that: The switch device is an NMOS tube, and the first connection terminal, the second connection terminal and the control terminal of the switch device are respectively the drain, the source and the gate of the NMOS tube.

4. The control circuit for reducing capacitor howling according to claim 3, characterized in that: The capacitive howling suppression circuit further includes a second resistor, one end of which is connected to the control end of the switch device, and the other end of which is grounded.

5. The control circuit for reducing capacitor howling according to claim 1, wherein: The capacitor in the capacitive howling suppression circuit includes one capacitor or multiple capacitors connected in parallel.

6. The control circuit for reducing capacitor howling according to claim 1, characterized in that: The resistance of the first resistor is in ohm level.

7. The control circuit for reducing capacitor howling according to any one of claims 1 to 6, characterized in that: It also includes a DC-DC conversion module, The input end of the DC-DC conversion module is connected to the node A, and the output end thereof is connected to the output power supply end VOUT; The DC-DC conversion module is used to convert the first DC power supply into a second DC power supply.

8. The control circuit for reducing capacitor howling according to claim 7, characterized in that: It also includes an inductor L1, one end of the inductor L1 is connected to the node A, and the other end is connected to the input end of the DC-DC conversion module; The multiple capacitor howling suppression circuits include a first capacitor howling suppression circuit and a second capacitor howling suppression circuit. One end of the capacitor in the first capacitor howling suppression circuit is connected to the node A, and one end of the capacitor in the second capacitor howling suppression circuit is connected to the input end of the DC-DC conversion module. The first capacitor howling suppression circuit, the second capacitor howling suppression circuit and the inductor L1 form an input filter circuit of the DC-DC conversion module.

9. The control circuit for reducing capacitor howling according to claim 8, characterized in that: It also includes a module circuit connected to the node A, The plurality of capacitive howling suppression circuits further include a third capacitive howling suppression circuit, one end of the capacitor in the third capacitive howling suppression circuit is connected to the input end of the module circuit, and the third capacitive howling suppression circuit forms an input filter circuit of the module circuit.

10. The control circuit for reducing capacitor howling according to claim 7, characterized in that: It also includes output filtering circuit, The output filter circuit includes an inductor L2 and a capacitor C2, one end of the inductor L2 is connected to the output end of the DC-DC conversion module, and the other end thereof is connected to the output power supply end VOUT; one end of the capacitor is connected to the other end of the inductor L2, and the other end thereof is grounded.

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