Carrier circuit for suppressing capacitor squeal

Abstract

The utility model provides a carrier circuit for suppressing capacitor squeal, which comprises a switching tube Q1, a voltage sampling circuit, a control circuit and a driving circuit, and is characterized in that an input power supply end VIN is connected with a node A; a first connecting end of the switching tube Q1 is connected with the node A, a second connecting end of the switching tube Q1 is connected with an output power supply end VOUT, and a control end of the switching tube Q1 is connected with a node F; the input end of the voltage sampling circuit is connected with the node A, the output end is connected with the input end of the control circuit, and the output end of the control circuit is connected with the input end of the driving circuit; the power supply end of the driving circuit is connected with the node A, and the output end is connected with the node F; the output power supply end VOUT is used for being connected with a functional circuit, and the functional circuit comprises a capacitor. Compared with the prior art, the circuit provided by the utility model is applied to a product of which the input power supply can be subjected to the condition of alternating current superposition, can reduce the cost, and can better suppress the squeal of the capacitor.

Description

[Technical field]

[0001] The utility model relates to the technical field of circuit design, in particular to a carrier circuit for suppressing capacitor howling. [Background technology]

[0002] In the automotive electrical system, AC voltage will be superimposed on the input power side, and 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. 1 , it is a waveform diagram of an input power supply superimposed with an AC voltage in one embodiment. When the chip capacitor in the circuit is subjected to an 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, mechanical vibration will be generated, thereby making a sound, which is the capacitor howling phenomenon. Please refer to Figure 2 As shown, it is a circuit diagram of a functional circuit with capacitors in one embodiment. Due to the presence of filter capacitors C1, C3, C4, C5, and C6, when an AC voltage is superimposed on the input power supply VIN, a ripple voltage of a certain frequency will appear in the entire operating system along with the input power supply VIN, and the chip capacitors will generate mechanical vibrations, thereby making a sound.

[0003] During the use of the product, the occurrence of capacitor howling will affect the user experience during use, especially in the automotive field. Abnormal noise during driving will affect the driver's attention and may cause the risk of traffic accidents.

[0004] At present, there are the following solutions for capacitor howling: 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 howling. Figure 3 ②, symmetrically place chip capacitors of the same specification at the same position on both sides of the PCB board, and reduce the degree of howling by canceling the vibration of the two capacitors. Figure 4 As shown, it is a schematic diagram of the structure 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 howling is limited, and it is related to the welding process, the degree of patch symmetry, etc., and there may be a situation where the capacitor howling cannot be effectively reduced.

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

[0007] One of the purposes of the utility model is to provide a carrier circuit for suppressing capacitor howling, which is applied to products where AC power is superimposed on the input power supply, which can not only reduce costs but also better suppress capacitor howling.

[0008] According to one aspect of the utility model, the utility model provides a carrier circuit for suppressing capacitor howling, which includes a switch tube Q1, a voltage sampling circuit, a control circuit and a drive circuit, and the input power supply terminal VIN is connected to the node A; the first connection end of the switch tube Q1 is connected to the node A, the second connection end is connected to the output power supply terminal VOUT, and the control end is connected to the node F; the input end of the voltage sampling circuit is connected to the node A, the output end is connected to the input end of the control circuit, and the output end of the control circuit is connected to the input end of the drive circuit; the power supply end of the drive circuit is connected to the node A, and the output end is connected to the node F; the output power supply terminal VOUT is used to be connected to a functional circuit, and the functional circuit includes a capacitor.

[0009] Furthermore, the voltage sampling circuit is used to collect the voltage of the node A and output a sampled voltage based on the voltage of the node A; the control circuit outputs a control signal Control based on the sampled voltage; and the drive circuit controls the switch tube Q1 to turn on or off based on the control signal Control.

[0010] Further, when the control circuit detects that an AC voltage is superimposed on the input power terminal VIN based on the sampled voltage, the drive circuit controls the switch tube Q1 to periodically alternately turn on and off based on the control signal Control; when the control circuit detects that no AC voltage is superimposed on the input power terminal VIN based on the sampled voltage, the drive circuit controls the switch tube Q1 to be continuously turned on based on the control signal Control, wherein the frequency of the periodic alternating turn-on and turn-off of the switch tube Q1 is greater than the frequency of the AC voltage superimposed on the input power terminal VIN.

[0011] Further, the output end of the control circuit includes a first output end and a second output end; the control signal Control includes a first control signal Control-1 and a second control signal Control-2; the first output end outputs the first control signal Control-1, and the second output end outputs the second control signal Control-2; the driving circuit includes a resistor R1, a resistor R3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube Q5 and a switch tube Q6, one end of the resistor R3 is connected to the node A, and the other end thereof is connected to the node F; the first connection end of the switch tube Q3 is connected to the node A, the second connection end thereof is connected to the node F, and the control end thereof is connected to the node E; the first connection end of the switch tube Q4 is connected to the node F, the second connection end thereof is connected to the node G, and the control end thereof is connected to the node E The first connection end of the switch tube Q2 is connected to the node A, the second connection end thereof is connected to the node E, and the control end thereof is connected to the node D; one end of the resistor R1 is connected to the node A, and the other end thereof is connected to the node D; the first connection end of the switch tube Q5 is connected to the node D via the resistor R5, the second connection end thereof is grounded, and the control end thereof is connected to the node C; one end of the resistor R8 is connected to the node C, and the other end thereof is grounded; one end of the resistor R6 is connected to the first output end of the control circuit, and the other end thereof is connected to the node C; one end of the resistor R7 is connected to the node E, and the other end thereof is connected to the node G; the first connection end of the switch tube Q6 is connected to the node G, the second connection end thereof is grounded, and the control end thereof is connected to the node H; one end of the resistor R10 is connected to the node H, and the other end thereof is grounded; one end of the resistor R9 is connected to the second output end of the control circuit, and the other end thereof is connected to the node H.

[0012] Furthermore, the voltage sampling circuit includes a resistor R2 and a resistor R4, one end of the resistor R2 is connected to the node A, and the other end thereof is connected to the node B; one end of the resistor R4 is connected to the node B, and the other end thereof is grounded; the node B is the output end of the voltage sampling circuit, and the voltage on the node B is the sampling voltage.

[0013] Furthermore, the voltage sampling circuit further includes a capacitor C2, one end of the capacitor C2 is connected to the node B, and the other end of the capacitor C2 is grounded.

[0014] Further, the switch tube Q1 is a PMOS transistor, and the first connection end, the second connection end and the control end of the switch tube Q1 are respectively the source, the drain and the gate of the PMOS transistor; the switch tube Q2 is a PNP-type triode, and the first connection end, the second connection end and the control end of the switch tube Q2 are respectively the emitter, the collector and the base of the PNP-type triode; the switch tube Q3 is an NPN-type triode, and the first connection end, the second connection end and the control end of the switch tube Q3 are respectively the collector, the emitter and the base of the NPN-type triode. The switch tube Q4 is a PNP type triode, and the first connection end, the second connection end and the control end of the switch tube Q4 are respectively the emitter, the collector and the base of the PNP type triode; the switch tube Q5 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q5 are respectively the collector, the emitter and the base of the NPN type triode; the switch tube Q6 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q6 are respectively the collector, the emitter and the base of the NPN type triode.

[0015] Furthermore, when the control circuit detects that an AC voltage is superimposed on the input power supply terminal VIN based on the sampled voltage, the first control signal Control-1 and the second control signal Control-2 output by the control circuit are both PWM signals, and the first control signal Control-1 and the second control signal Control-2 are both high level or low level at the same time; when the control circuit detects that no AC voltage is superimposed on the input power supply terminal VIN based on the sampled voltage, the first control signal Control-1 and the second control signal Control-2 output by the control circuit are both high level.

[0016] Further, when the first control signal Control-1 and the second control signal Control-2 are both at high levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned on; when the first control signal Control-1 and the second control signal Control-2 are both at low levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned off.

[0017] Furthermore, the resistance values ​​of the resistor R9 and the resistor R10 are selected to satisfy: when the second control signal Control-2 is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the switch tube Q6, so that the switch tube Q6 is in an on state; the resistance values ​​of the resistor R6 and the resistor R8 are selected to satisfy: when the first control signal Control-1 is at a high level, the voltage value of the node C is greater than the turn-on voltage value of the switch tube Q5, so that the switch tube Q5 is in an on state; the resistance values ​​of the resistor R1 and the resistor R5 are selected to satisfy: when the switch tube Q5 is in an on state, the voltage difference between the node A and the node D is greater than the voltage drop of the body diode between the emitter and the base of the switch tube Q2, so that the switch tube Q2 is in an on state.

[0018] Furthermore, the carrier circuit for suppressing capacitor howling also includes an anti-reverse diode D1, wherein the positive electrode of the anti-reverse diode D1 is connected to the input power supply terminal VIN, and the negative electrode thereof is connected to the node A.

[0019] Furthermore, the carrier circuit for suppressing capacitor howling also includes a Zener diode D2, the cathode of the Zener diode D2 is connected to the node A, and the anode of the Zener diode D2 is connected to the node F; the operating voltage value of the Zener diode D2 is greater than the turn-on voltage value of the switch tube Q1 and less than the maximum rated voltage value between the gate and the source of the switch tube Q1; the turn-on voltage value of the switch tube Q1 is less than the maximum rated voltage value between the gate and the source of the switch tube Q1.

[0020] Compared with the prior art, the utility model is applied to products where AC power may be superimposed on the input power supply, which can not only reduce the cost but also better suppress capacitor howling.

Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0022] Figure 1 In one embodiment, the input power supply appears as a waveform diagram of a superimposed AC voltage;

[0023] Figure 2 is a circuit diagram of a functional circuit with a capacitor in one embodiment;

[0024] Figure 3 It is a structural schematic diagram of an anti-howling capacitor in the prior art;

[0025] Figure 4 It is a schematic diagram of the structure of another anti-howling capacitor in the prior art;

[0026] Figure 5 A circuit diagram of a carrier circuit for suppressing capacitor howling in one embodiment of the utility model;

[0027] Figure 6 The present invention is a logic flow chart for determining whether an AC voltage is superimposed on an input power terminal VIN based on a sampled voltage in one embodiment. [Specific implementation method]

[0028] 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 in conjunction with the accompanying drawings and specific implementation methods.

[0029] The "one embodiment" or "embodiment" referred to herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the utility model. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "coupled", "connected", "connected" and "connected" in this document that indicate electrical connection all mean direct or indirect connection. For example, A is connected to B, which includes both direct electrical connection between A and B and connection between A and B through electrical components or circuits.

[0030] 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 should not be understood as a limitation on the present invention.

[0031] Please refer to Figure 5 As shown, it is a circuit diagram of a carrier circuit for suppressing capacitor howling in one embodiment of the utility model. Figure 5 The carrier circuit for suppressing capacitor howling shown includes a switch tube Q1 , a voltage sampling circuit 510 , a control circuit 520 and a drive circuit 530 .

[0032] The input power supply terminal VIN is connected to the node A; the first connection terminal of the switch tube Q1 is connected to the node A, the second connection terminal thereof is connected to the output power supply terminal VOUT, and the control terminal thereof is connected to the node F. The input terminal of the voltage sampling circuit 510 is connected to the node A, the output terminal thereof is connected to the input terminal of the control circuit 520, the output terminal of the control circuit 520 is connected to the input terminal of the driving circuit 530; the power supply terminal of the driving circuit 530 is connected to the node A, and the output terminal thereof is connected to the node F. Specifically, the voltage sampling circuit 510 is used to collect the voltage of the node A, and output a sampled voltage based on the voltage of the node A; the control circuit 520 outputs a control signal Control based on the sampled voltage; and the driving circuit 530 controls the switch tube Q1 to be turned on or off based on the control signal Control.

[0033] When the control circuit 520 detects that an AC voltage is superimposed on the input power terminal VIN based on the sampling voltage output by the sampling circuit 510, the drive circuit 530 controls the switch tube Q1 to periodically alternately turn on and off based on the control signal Control output by the control circuit 520; when the control circuit 520 detects that no AC voltage is superimposed on the input power terminal VIN based on the sampling voltage output by the sampling circuit 510, the drive circuit 530 controls the switch tube Q1 to be continuously turned on based on the control signal Control output by the control circuit 520, wherein the frequency of the periodic alternating on and off of the switch tube Q1 is greater than the frequency of the AC voltage superimposed on the input power terminal VIN.

[0034] The output power supply terminal VOUT is used to connect to the functional circuit 540, and the functional circuit 540 includes a capacitor. Figure 5 In the specific embodiment shown, the functional circuit 540 includes an inductor L1, a capacitor C1, a capacitor C3, a capacitor C4, a capacitor C5 and a capacitor C6. One end of the capacitor C6 is connected to the output power supply terminal VOUT, and the other end thereof is grounded; one end of the inductor L1 is connected to the output power supply terminal VOUT; one end of the capacitor C1 is connected to the other end of the inductor L1, and the other end thereof is grounded; one end of the capacitor C3 is connected to the other end of the inductor L1, and the other end thereof is grounded; one end of the capacitor C4 is connected to the other end of the inductor L1, and the other end thereof is grounded; one end of the capacitor C5 is connected to the other end of the inductor L1, and the other end thereof is grounded. It should be noted that in other embodiments, the functional circuit 540 may also be other circuits including capacitors.

[0035] exist Figure 5In the specific embodiment shown, the output end of the control circuit 520 includes a first output end and a second output end, and the control signal Control includes a first control signal Control-1 and a second control signal Control-2, wherein the first output end outputs the first control signal Control-1, and the second output end outputs the second control signal Control-2. The driving circuit 530 includes a resistor R1, a resistor R3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube Q5 and a switch tube Q6, wherein one end of the resistor R3 is connected to the node A, and the other end thereof is connected to the node F; the first connection end of the switch tube Q3 is connected to the node A, the second connection end thereof is connected to the node F, and the control end thereof is connected to the node E; the first connection end of the switch tube Q4 is connected to the node F, the second connection end thereof is connected to the node G, and the control end thereof is connected to the node E; the first connection end of the switch tube Q2 is connected to the node A, the second connection end thereof is connected to the node E, and the control end thereof is connected to the node D; one end of the resistor R1 is connected to the node A, the second connection end thereof is connected to the node E, and the control end thereof is connected to the node D; The first connection end of the switch tube Q5 is connected to the node D via the resistor R5, the second connection end thereof is grounded, and the control end thereof is connected to the node C; one end of the resistor R8 is connected to the node C, and the other end thereof is grounded; one end of the resistor R6 is connected to the first output end of the control circuit 520, and the other end thereof is connected to the node C; one end of the resistor R7 is connected to the node E, and the other end thereof is connected to the node G; the first connection end of the switch tube Q6 is connected to the node G, the second connection end thereof is grounded, and the control end thereof is connected to the node H; one end of the resistor R10 is connected to the node H, and the other end thereof is grounded; one end of the resistor R9 is connected to the second output end of the control circuit 520, and the other end thereof is connected to the node H.

[0036] exist Figure 5 In the specific embodiment shown, the control circuit 520 is an MCU (Microcontroller Unit) in U1, and its input end is an ADC (analog-to-digital converter) pin.

[0037] exist Figure 5In the specific embodiment shown, the switch tube Q1 is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q1 are respectively the source (S pole), the drain (D pole) and the gate (G pole) of the PMOS transistor. Therefore, the switch tube Q1 can also be called a MOS tube (or field effect tube). The switch tube Q2 is a PNP type triode, and the first connection end, the second connection end and the control end of the switch tube Q2 are respectively the emitter, the collector and the base of the PNP type triode; the switch tube Q3 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q3 are respectively the collector, the emitter and the base of the NPN type triode; the switch tube Q4 is a PNP type triode, and the first connection end, the second connection end and the control end of the switch tube Q4 are respectively the emitter, the collector and the base of the PNP type triode; the switch tube Q5 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q5 are respectively the collector, the emitter and the base of the NPN type triode; the switch tube Q6 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q6 are respectively the collector, the emitter and the base of the NPN type triode.

[0038] exist Figure 5 In the specific embodiment shown, the voltage sampling circuit 510 includes a resistor R2 and a resistor R4, one end of the resistor R2 is connected to the node A, and the other end thereof is connected to the node B; one end of the resistor R4 is connected to the node B, and the other end thereof is grounded; the node B is the output end of the voltage sampling circuit 510, and the voltage on the node B is the sampling voltage. In addition, the voltage sampling circuit 510 also includes a capacitor C2, one end of the capacitor C2 is connected to the node B, and the other end thereof is grounded.

[0039] Figure 5 The carrier circuit for suppressing capacitor howling shown also includes an anti-reverse diode D1, the positive electrode of which is connected to the input power terminal VIN, and the negative electrode of which is connected to the node A. When the input power terminal VIN and the output power terminal VOUT are reversely connected, the anti-reverse diode D1 plays a reverse connection protection role.

[0040] Figure 5The carrier circuit for suppressing capacitor howling shown also includes a voltage stabilizing diode D2, the cathode of the voltage stabilizing diode D2 is connected to the node A, and the anode thereof is connected to the node F. Among them, the voltage stabilizing diode D2 plays a role in protecting the MOS tube (or field effect tube) Q1, preventing the voltage between the gate and the source of the MOS tube Q1 from exceeding the rated voltage value (or exceeding the gate and source withstand voltage value of the MOS tube). Specifically, the MOS tube (or field effect tube) Q1 will not be burned out because the voltage between the node A and the node F is too high when the power supply generates a pulse, exceeding the withstand voltage value between the source and the gate of the MOS tube (or field effect tube) Q1. It can also be said that the operating voltage value of the voltage stabilizing diode D2 is greater than the turn-on voltage value of the switch tube Q1 and less than the maximum rated voltage value between the gate and the source of the switch tube Q1, wherein the turn-on voltage value of the switch tube Q1 is less than the maximum rated voltage value between the gate and the source of the switch tube Q1.

[0041] exist Figure 5 In the specific embodiment shown, when the control circuit 520 detects that the input power supply terminal VIN is superimposed with an AC voltage based on the sampled voltage, the first control signal Control-1 outputted from the first output terminal of the control circuit 520 and the second control signal Control-2 outputted from the second output terminal are both PWM (Pulse-Width Modulation) signals, wherein the first control signal Control-1 and the second control signal Control-2 are both high level or low level at the same time. When the control circuit 520 detects that the input power supply terminal VIN is not superimposed with an AC voltage based on the sampled voltage, the first control signal Control-1 outputted from the first output terminal of the control circuit 520 and the second control signal Control-2 outputted from the second output terminal are both high level.

[0042] When the first control signal Control-1 and the second control signal Control-2 are both at high levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned on; when the first control signal Control-1 and the second control signal Control-2 are both at low levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned off. Correspondingly, the resistance values ​​of the resistors R9 and R10 are selected to satisfy: when the second control signal Control-2 is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the switch tube Q6, so that the switch tube Q6 is in the on state; the resistance values ​​of the resistors R6 and R8 are selected to satisfy: when the first control signal Control-1 is at a high level, the voltage value of the node C is greater than the turn-on voltage value of the switch tube Q5, so that the switch tube Q5 is in the on state; the resistance values ​​of the resistors R1 and R5 are selected to satisfy: when the switch tube Q5 is in the on state, the voltage difference between the node A and the node D is greater than the voltage drop of the body diode between the emitter and the base of the transistor Q2, so that the transistor Q2 is in the on state.

[0043] The following is a detailed introduction Figure 5 The working principle of the carrier circuit for suppressing capacitor howling is shown.

[0044] When the control circuit 520 detects that the input power supply terminal VIN is not superimposed with an AC voltage based on the sampled voltage, specifically, when the control circuit 520 detects that the input power supply terminal VIN is greater than a certain turn-on voltage value (the turn-on voltage can be set according to demand) based on the sampled voltage, the control circuit 520 controls the first control signal Control-1 output from the first output terminal and the second control signal Control-2 output from the second output terminal to be both high level. Since the selection of the resistance values ​​of the resistors R9 and R10 satisfies: when the second control signal Control-2 is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the transistor Q6, therefore, when the second control signal Control-2 is at a high level, the transistor Q6 is turned on, and the node G is at a low level. Since the selection of the resistance values ​​of the resistors R6 and R8 satisfies: when the first control signal Control-1 is at a high level, the voltage value of the node C is greater than the turn-on voltage value of the transistor Q5, therefore, when the first control signal Control-1 is at a high level, the transistor Q5 is turned on, and the voltage of the node D is related to the resistors R1 and R5. Since the resistance values ​​of resistor R1 and resistor R5 are selected to satisfy: when switch tube Q5 is in the on state, the voltage difference between node A and node D is greater than the voltage drop of the body diode between the emitter and base of transistor Q2, so transistor Q2 is turned on and node E is high level. Since the voltage of node E is greater than the turn-on voltage value of transistor Q3, transistor Q3 is in the on state, and the voltage of node E is clamped by the body diode of transistor Q3, and the voltage difference between node A and node E is approximately equal to the voltage drop of the body diode of transistor Q3. At this time, since transistor Q3 is turned on, node F is high level, that is, the emitter of transistor Q4 is high level, and the base voltage of transistor Q4 is the voltage of node E, so the emitter voltage of transistor Q4 is greater than the base voltage, so transistor Q4 is turned on. Since transistor Q6 is turned on, node G is low level, so when transistor Q4 is turned on, node F is also low level. At this time, the voltage between node A and node F is greater than the turn-on voltage value of field effect tube Q1, so field effect tube Q1 is turned on. That is to say, when the control circuit 520 detects that the input power supply terminal VIN is not superimposed with an AC voltage based on the sampled voltage, the first control signal Control-1 output by the first output terminal of the control circuit 520 and the second control signal Control-2 output by the second output terminal are both high level, so that the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned on, so that the power of the input power supply terminal VIN is transmitted to the output terminal VOUT through the diode D1 and the field effect tube Q1. Since there is no superimposed AC power at this time, the capacitors C1, C3, C4, C5 and C6 in the functional circuit 540 will not produce a whistling phenomenon, and the functional circuit 540 can work normally.

[0045] When the input power supply terminal VIN is superimposed with an AC voltage, the voltage of the input power supply terminal VIN will be in a fluctuating state. The control circuit 520 can detect the input voltage of its input terminal ADC (which is equal to the sampling voltage) through software, and determine whether to output a PWM signal through judgment logic. The specific judgment logic is as follows: Figure 6 shown.

[0046] Figure 6 The present invention is a logic flow chart for determining whether an AC voltage is superimposed on an input power terminal VIN based on a sampled voltage in one embodiment. Figure 6 The judgment logic shown for judging whether the input power terminal VIN is superimposed with an AC voltage based on the sampled voltage includes the following steps.

[0047] Step 610, calculate the maximum value VIN_filter_max and the minimum value VIN_filter_min in VIN_filter[n]; calculate the average value VIN_filter_average of all VIN_filter[n] within 1s. It should be noted in step 610 that the array VIN_filter[0]~VIN_filter[n] stores the voltage filter data collected by the control circuit 520 within 1s, and 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].

[0048] Step 620 , determine whether VIN_filter_max-VIN_filter_min<500mv is satisfied. If not (No), return to step 610 ; if yes (Yes), execute step 630 .

[0049] Step 630: Calculate the maximum value VIN_original_max and the minimum value VIN_original_min in VIN_original[m] within 5 seconds. It should be noted in step 630 that, similarly to VIN_filter[n], VIN_original[0] should start collecting after the last data of VIN_filter[n]; VIN_original[m] stores 5 seconds of continuous voltage data.

[0050] Step 640: Determine whether all of the following conditions are met simultaneously:

[0051] ①VIN_original_max-VIN_filter_average>500mv;

[0052] ②VIN_filter_average-VIN_filter_min>500mv;

[0053] ③VIN_original_max-VIN_filter_min>2V.

[0054] If not (No), return to step 610; if (Yes), execute step 640.

[0055] Step 640, MCU GPIO Control1 and Control2 output PWM signals, that is, (the first output terminal and the second output terminal of the control circuit 520 output PWM signals, 35khz / 10duty, for 100s, and then return to step 610. Specifically, the MCU controls the first output terminal and the second output terminal to output PWM signals, with a frequency of 35kHz and a duty cycle of 20%, for 100s. The parameters determined above can be adjusted according to actual usage requirements. Of course, the PWM signal can also be other frequencies, such as 30khz, 25khz, as long as it is higher than 20khz.

[0056] 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.

[0057] Figure 6 Only one specific example of judging whether the input power terminal VIN is superimposed with an AC voltage based on the sampled voltage is given. Obviously, those skilled in the art can also judge whether the input power terminal VIN is superimposed with an AC voltage in other ways.

[0058] When the control circuit 520 detects that an AC voltage is superimposed on the input power supply terminal VIN based on the sampled voltage, the first control signal Control-1 output from the first output terminal and the second control signal Control-2 output from the second output terminal of the control circuit 520 are both PWM signals, and the PWM signals are square wave signals (i.e., high and low levels) with a certain duty cycle.

[0059] When the PWM signal output by the control circuit 520 is at a high level (i.e., both the first control signal Control-1 and the second control signal Control-2 are at a high level), transistors Q5 and Q6 are turned on. Since transistor Q5 is turned on, at this time, the voltage difference between node A and node D is greater than the body diode voltage drop of transistor Q2, so transistor Q2 is turned on and node E is at a high level. Since the voltage at node E is greater than the turn-on voltage value of transistor Q3, transistor Q3 is in the on state, and the voltage at node E will be clamped by the body diode of transistor Q3, and the voltage at node E is approximately equal to the voltage drop of the body diode. At this time, since transistor Q3 is turned on, node F is at a high level, that is, the emitter of transistor Q4 is at a high level, and the base voltage of transistor Q4 is the voltage of node E, so the emitter voltage of transistor Q4 is greater than the base voltage, so transistor Q4 is turned on. Since transistor Q6 is turned on, node G is at a low level, so when transistor Q4 is turned on, node F is also at a low level. At this time, the voltage between node A and node F is greater than the turn-on voltage value of field effect tube Q1, so the field effect tube Q1 is turned on. In other words, when the PWM signal output by the control circuit 520 is at a high level, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned on.

[0060] When the PWM signal output by the control circuit 520 is at a low level (i.e., both the first control signal Control-1 and the second control signal Control-2 are at a low level), both transistors Q5 and Q6 are turned off. Since transistor Q5 is turned off, at this time, the voltage difference between node A and node D is less than the body diode voltage drop of transistor Q2, so transistor Q2 is turned off, node E is at a low level, and the voltage at node E is less than the turn-on voltage value of transistor Q3, so transistor Q3 is turned off. At this time, the voltage between node A and node F is less than the turn-on voltage value of field effect transistor Q1, so field effect transistor Q1 is turned off. In other words, when the PWM signal output by the control circuit 520 is at a low level, switch tubes Q1, switch tubes Q2, switch tubes Q3, switch tubes Q4, switch tubes Q5, and switch tubes Q6 are all turned off.

[0061] In a specific embodiment, since the frequency of the PWM signal is 35kHz, the control signal Control output by the control circuit 520 switches between high and low levels, so that the field effect transistor Q1 also switches with the frequency of the PWM signal. Since the ripple voltage frequency of the input power supply terminal VIN is 30Hz to 15kHz, within this frequency range, the whistle generated by the capacitor due to vibration is within the frequency range audible to the human ear, and the use of Figure 5The carrier circuit shown can change the ripple frequency superimposed on both ends of the capacitor to 35kHz, which is beyond the frequency range that the human ear can hear, thereby effectively reducing the problem of poor user experience caused by capacitor whistling. It can also be said that the frequency of the PWM signal (or the frequency of the periodic alternating on and off of the switch tube Q1) exceeds the frequency range that the human ear can hear.

[0062] In summary, the utility model detects the input voltage value of the input power supply terminal VIN and determines whether there is a superimposed AC voltage through a software algorithm. If there is a superimposed AC voltage, the low-frequency signal is modulated onto a high-frequency carrier through the constructed carrier circuit, thereby reducing the degree of capacitor howling. If there is no superimposed AC voltage, the constructed carrier circuit does not work and will not affect the normal working state.

[0063] Compared with the prior art, the carrier circuit for suppressing capacitor howling provided by the utility model has the following advantages:

[0064] Beneficial effects:

[0065] 1. The carrier circuit for suppressing capacitor howling provided by the utility model uses simple discrete components and software judgment to realize functions, and has lower cost than the solution of bracket capacitors.

[0066] 2. Compared with a solution in which chip circuits of the same specification are symmetrically placed at the same positions on the front and back sides of a PCB board, the carrier circuit for suppressing capacitor howling provided by the utility model has higher reliability and can suppress capacitor howling better.

[0067] It should be noted that any changes made by those skilled in the art to the specific implementation of the present invention do not deviate 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 implementation.

Claims

1. A carrier circuit for suppressing capacitor howling, characterized in that: It includes a switch tube Q1, a voltage sampling circuit, a control circuit and a drive circuit. The input power supply terminal VIN is connected to the node A; the first connection terminal of the switch tube Q1 is connected to the node A, the second connection terminal thereof is connected to the output power supply terminal VOUT, and the control terminal thereof is connected to the node F; The input end of the voltage sampling circuit is connected to the node A, the output end thereof is connected to the input end of the control circuit, and the output end of the control circuit is connected to the input end of the drive circuit; The power supply terminal of the driving circuit is connected to the node A, and the output terminal thereof is connected to the node F; The output power supply terminal VOUT is used to be connected to a functional circuit, and the functional circuit includes a capacitor.

2. The carrier circuit for suppressing capacitor howling according to claim 1, characterized in that: The voltage sampling circuit is used to collect the voltage of the node A and output a sampled voltage based on the voltage of the node A; The control circuit outputs a control signal Control based on the sampled voltage; The driving circuit controls the switch tube Q1 to be turned on or off based on the control signal Control.

3. The carrier circuit for suppressing capacitor howling according to claim 2, characterized in that: When the control circuit detects that the input power terminal VIN is superimposed with an AC voltage based on the sampled voltage, the drive circuit controls the switch tube Q1 to be periodically alternately turned on and off based on the control signal Control; When the control circuit detects that the input power terminal VIN is not superimposed with an AC voltage based on the sampled voltage, the drive circuit controls the switch tube Q1 to be continuously turned on based on the control signal Control. The frequency of the periodic alternating on and off of the switch tube Q1 is greater than the frequency of the AC voltage superimposed on the input power supply terminal VIN.

4. The carrier circuit for suppressing capacitor howling according to claim 3, characterized in that: The output end of the control circuit includes a first output end and a second output end; the control signal Control includes a first control signal Control-1 and a second control signal Control-2; the first output end outputs the first control signal Control-1, and the second output end outputs the second control signal Control-2; The driving circuit includes a resistor R1, a resistor R3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube Q5 and a switch tube Q6. One end of the resistor R3 is connected to the node A, and the other end thereof is connected to the node F; the first connection end of the switch tube Q3 is connected to the node A, the second connection end thereof is connected to the node F, and the control end thereof is connected to the node E; the first connection end of the switch tube Q4 is connected to the node F, the second connection end thereof is connected to the node G, and the control end thereof is connected to the node E; the first connection end of the switch tube Q2 is connected to the node A, the second connection end thereof is connected to the node E, and the control end thereof is connected to the node D; one end of the resistor R1 is connected to the node A, and the other end thereof is connected to the node D; the first connection end of the switch tube Q5 is connected to the node F through the resistor R5. The node D is connected, its second connection end is grounded, and its control end is connected to the node C; one end of the resistor R8 is connected to the node C, and the other end thereof is grounded; one end of the resistor R6 is connected to the first output end of the control circuit, and the other end thereof is connected to the node C; one end of the resistor R7 is connected to the node E, and the other end thereof is connected to the node G; the first connection end of the switch tube Q6 is connected to the node G, the second connection end thereof is grounded, and the control end thereof is connected to the node H; one end of the resistor R10 is connected to the node H, and the other end thereof is grounded; one end of the resistor R9 is connected to the second output end of the control circuit, and the other end thereof is connected to the node H.

5. The carrier circuit for suppressing capacitor howling according to claim 2, characterized in that: The voltage sampling circuit includes a resistor R2 and a resistor R4. One end of the resistor R2 is connected to the node A, and the other end thereof is connected to the node B; one end of the resistor R4 is connected to the node B, and the other end thereof is grounded; the node B is the output end of the voltage sampling circuit, and the voltage on the node B is the sampling voltage.

6. The carrier circuit for suppressing capacitor howling according to claim 5, characterized in that: The voltage sampling circuit further includes a capacitor C2, one end of which is connected to the node B, and the other end of which is grounded.

7. The carrier circuit for suppressing capacitor howling according to claim 4, characterized in that: The switch tube Q1 is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q1 are the source, the drain and the gate of the PMOS transistor respectively; The switch tube Q2 is a PNP type triode, and the first connection end, the second connection end and the control end of the switch tube Q2 are respectively the emitter, the collector and the base of the PNP type triode; The switch tube Q3 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q3 are respectively the collector, the emitter and the base of the NPN type triode; The switch tube Q4 is a PNP type triode, and the first connection end, the second connection end and the control end of the switch tube Q4 are respectively the emitter, the collector and the base of the PNP type triode; The switch tube Q5 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q5 are respectively the collector, the emitter and the base of the NPN type triode; The switch tube Q6 is an NPN type triode, and the first connection end, the second connection end and the control end of the switch tube Q6 are respectively the collector, the emitter and the base of the NPN type triode.

8. The carrier circuit for suppressing capacitor howling according to claim 7, characterized in that: When the control circuit detects that the input power terminal VIN is superimposed with an AC voltage based on the sampled voltage, the first control signal Control-1 and the second control signal Control-2 output by the control circuit are both PWM signals, and the first control signal Control-1 and the second control signal Control-2 are both high level or low level at the same time, and the frequency of the PWM signal is higher than 20KHz, When the control circuit detects that no AC voltage is superimposed on the input power terminal VIN based on the sampled voltage, the first control signal Control-1 and the second control signal Control-2 output by the control circuit are both at high level.

9. The carrier circuit for suppressing capacitor howling according to claim 8, characterized in that: When the first control signal Control-1 and the second control signal Control-2 are both at high levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned on; When the first control signal Control-1 and the second control signal Control-2 are both at low levels, the switch tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all turned off.

10. The carrier circuit for suppressing capacitor howling according to claim 8, characterized in that: The resistance values ​​of the resistor R9 and the resistor R10 are selected to satisfy: when the second control signal Control-2 is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the switch tube Q6, so that the switch tube Q6 is in a conducting state; The resistance values ​​of the resistor R6 and the resistor R8 are selected to satisfy: when the first control signal Control-1 is at a high level, the voltage value of the node C is greater than the turn-on voltage value of the switch tube Q5, so that the switch tube Q5 is in a conducting state; The resistance values ​​of the resistor R1 and the resistor R5 are selected to satisfy the following requirement: when the switch tube Q5 is in the on state, the voltage difference between the node A and the node D is greater than the voltage drop of the body diode between the emitter and the base of the switch tube Q2, so that the switch tube Q2 is in the on state.

11. The carrier circuit for suppressing capacitor howling according to claim 1, characterized in that: It also includes an anti-reverse diode D1, wherein the anode of the anti-reverse diode D1 is connected to the input power supply terminal VIN, and the cathode of the anti-reverse diode D1 is connected to the node A.

12. The carrier circuit for suppressing capacitor howling according to any one of claims 1 to 11, characterized in that: It also includes a Zener diode D2, The cathode of the voltage stabilizing diode D2 is connected to the node A, and the anode of the voltage stabilizing diode D2 is connected to the node F; The operating voltage value of the voltage stabilizing diode D2 is greater than the turn-on voltage value of the switch tube Q1 and less than the maximum rated voltage value between the gate and the source of the switch tube Q1; The turn-on voltage value of the switch tube Q1 is less than the maximum rated voltage value between the gate and the source of the switch tube Q1.

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