Direct current-direct current conversion circuit for reducing capacitor squeal

Abstract

The utility model provides a DC-DC conversion circuit for reducing capacitor squeal, comprising a voltage sampling circuit, the input end of which is connected with a node A, the output end of which outputs sampling voltage, and the node A is connected with an input power supply end; the input end of the master control circuit is connected with the output end of the voltage sampling circuit, the first output end of the master control circuit outputs a first control signal, and the second output end of the master control circuit outputs a second control signal; the input end of the direct current-direct current conversion module is connected with a node A, the output end of the direct current-direct current conversion module is connected with an output power supply end VOUT, and the enabling end of the direct current-direct current conversion module is connected with the first output end of the main control circuit; the first connecting end of the switch control circuit is connected with the node A, the second connecting end of the switch control circuit is connected with the node D, and the control end of the switch control circuit is connected with the second output end of the main control circuit; the first connecting end of the linear voltage stabilizing circuit is connected with the node D, and the second connecting end of the linear voltage stabilizing circuit is connected with the output power supply end. Compared with the prior art, the utility model can play a role in reducing the squeal of the capacitor.

Description

Technical field

[0001] The utility model relates to the technical field of circuit design, in particular to a DC-DC conversion circuit capable of reducing capacitor whistling. [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 in the prior art. According to the characteristics of the DC-DC converter circuit, the DC-DC chip U1 will generate ripple voltage at the input and output ends during operation, thereby increasing the AC voltage value superimposed on the input power supply side. At the same time, due to the presence of filter capacitors C1, C2, C3, C4, C5, and C6, the greater the AC voltage superimposed on both ends of the capacitor, the worse the capacitor howling will be.

[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 objectives of the present invention is to provide a DC-DC conversion circuit that reduces capacitor noise. When an AC voltage is superimposed, the DC-DC conversion module (or DCDC chip) is disabled to reduce the ripple voltage at the input power supply terminal VIN and the output power supply terminal VOUT. This reduces the ripple voltage superimposed across the input and output capacitors, thereby reducing capacitor noise.

[0008] According to one aspect of the present invention, the present invention provides a DC-DC conversion 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, its first output end outputs a first control signal, and its second output end outputs a second control signal, the main control circuit outputs the first control signal and the second control signal based on the sampling voltage a DC-DC conversion module, whose input end is connected to the node A, whose output end is connected to the output power supply end VOUT, and whose enable end is connected to the first output end of the main control circuit, wherein the DC-DC conversion module is used to convert the first DC power supply into a second DC power supply; a switch control circuit, whose first connection end is connected to the node A, whose second connection end is connected to the node D, and whose control end is connected to the second output end of the main control circuit; a linear voltage regulator circuit, whose first connection end is connected to the node D, and whose second connection end is connected to the output power supply end VOUT, wherein the linear voltage regulator circuit is used to provide a stable voltage to the output power supply end VOUT.

[0009] Compared with the prior art, the present invention is applied to products that use DCDC and whose input power supply may be superimposed with AC power. When there is a superimposed AC voltage, the DC-DC conversion module (or DCDC chip) is disabled to reduce the ripple voltage at the input power supply terminal VIN and the output power supply terminal VOUT, thereby reducing the ripple voltage value superimposed on the input capacitor and the output capacitor, thereby reducing 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 Schematic diagram of a DC-DC converter circuit for reducing capacitor noise 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. [Specific implementation method]

[0017] 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.

[0018] 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.

[0019] 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.

[0020] Please refer to Figure 5, which is a circuit diagram of a DC-DC conversion circuit for reducing capacitor howling in one embodiment of the present invention. Figure 5 The DC-DC conversion circuit for reducing capacitor noise shown includes a voltage sampling circuit 510 , a DC-DC conversion module U1 , a main control circuit U2 , a switch control circuit 520 and a linear voltage stabilization circuit 530 .

[0021] 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 R11 and R12. Resistor R11 has one end connected to node A and its other end connected to node B. Resistor R12 has one end connected to node B and its other end grounded. 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 C9, one end of which is connected to node B and its other end is grounded.

[0022] The input end of the main control circuit U2 is connected to the output end of the voltage sampling circuit 510, and its first output end outputs the first control signal Control-1, and its second output end outputs the second control signal Control-2. The main control circuit U2 outputs the first control signal Control-1 and the second control signal Control-2 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.

[0023] The input terminal Vin_dcdc of the DC-DC conversion module U1 (i.e., the DCDC chip) is connected to the node A, the output terminal Vout_dcdc of the DC-DC conversion module U1 is connected to the output power terminal VOUT, and the enable terminal Enable of the DC-DC conversion module U1 is connected to the first output terminal (or the first control signal Control-1) of the main control circuit U2. The DC-DC conversion module U1 is used to convert the first DC power supply into the second DC power supply. This is a technical content well known to those skilled in the art and will not be described in detail here.

[0024] The switch control circuit 520 has a first connection terminal connected to node A, a second connection terminal connected to node D, and a control terminal (ie, node E) connected to the second output terminal (or the second control signal Control-2) of the main control circuit U2.

[0025] A first connection terminal of the linear voltage stabilizing circuit 530 is connected to the node D, and a second connection terminal thereof is connected to the output power terminal VOUT. The linear voltage stabilizing circuit 530 is configured to provide a stable voltage to the output power terminal VOUT.

[0026] Figure 5 The DC-DC converter circuit for reducing capacitor noise shown further includes a first filtering circuit 550 and a second filtering circuit 560 .

[0027] The first filter circuit 550 is connected between the node A and the input terminal Vin_dcdc of the DC-DC converter module U1. The first filter circuit 550 includes a capacitor. The first filter circuit 550 is a filter circuit for the input power terminal VIN. It is an inevitable part in circuit design to ensure that the EMC (Electromagnetic Compatibility) test results meet the standard requirements. Figure 5 In the specific embodiment shown, the first filter circuit 550 includes an inductor L1, a capacitor C1, a capacitor C2, a capacitor C3, and a capacitor C4, wherein one end of the inductor L1 is connected to the node A, and the other end thereof is connected to the input terminal Vin_dcdc of the DC-DC converter module U1; one end of the capacitor C1 is connected to one end of the inductor L1, and the other end thereof is grounded; one end of the capacitor C2 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; and one end of the capacitor C4 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 first filter circuit 550 may also be other filter circuits including capacitors.

[0028] The second filter circuit 560 is connected between the output terminal Vout_dcdc and the output power terminal VOUT of the DC-DC conversion module U1. The second filter circuit 560 includes a capacitor. The second filter circuit 560 is a filter circuit for the output power terminal VOUT. It can reduce the ripple of the output voltage of the DC-DC conversion module U1 (i.e., the DCDC chip) and is an inevitable part in circuit design. Figure 5 In the illustrated embodiment, the second filter circuit 560 includes an inductor L2, a capacitor C5, and a capacitor C6. One end of the inductor L2 is connected to the output terminal Vout_dcdc of the DC-DC converter module U1, and a second end thereof is connected to the output power terminal VOUT. One end of the capacitor C5 is connected to the other end of the inductor L2, and the other end thereof is grounded. One end of the capacitor C6 is connected to the other end of the inductor L2, and the other end thereof is grounded. In other embodiments, the second filter circuit 560 may also be another filter circuit including capacitors.

[0029] When the main control circuit U2 detects based on the sampled voltage output by the voltage sampling circuit 510 that the voltage of the input power terminal VIN is greater than a preset start-up voltage (i.e., a preset voltage, which can be set as required) and no AC voltage is superimposed on the input power terminal VIN, the first control signal Control-1 output by the main control circuit U2 enables the DC-DC conversion module U1 to operate, and the second control signal Control-2 output by the main control circuit U2 controls the switch control circuit 520 to cut off the connection between the node A and the node D, so that the linear voltage regulator circuit 530 does not operate. At this time, only the DC-DC conversion module U1 is used. The block (i.e., DCDC) U1 supplies power to the output power terminal VOUT; when the main control circuit U2 detects that an AC voltage is superimposed on the input power terminal VIN based on the sampled voltage output by the voltage sampling circuit 510, the first control signal Control-1 output by the main control circuit U2 causes the DC-DC conversion module (i.e., DCDC) U1 to stop working, and the second control signal Control-2 output by the main control circuit U2 controls the switch control circuit 520 to connect nodes A and D, so as to cause the linear voltage regulator circuit 530 to operate. At this time, only the linear voltage regulator circuit 530 supplies power to the output power terminal VOUT. In other words, the DC-DC conversion circuit for reducing capacitor howling provided by the present invention causes the DC-DC conversion module to stop working when there is a superimposed AC voltage, thereby reducing the ripple voltage of the input power terminal VIN and the output power terminal VOUT, so that the ripple voltage value superimposed on the input capacitors C1, C2, C3, C4 and the output capacitors C5, C6 is reduced, thereby achieving the effect of reducing capacitor howling.

[0030] exist Figure 5 In the specific embodiment shown, the switch control circuit 520 includes a switch tube Q1, a resistor R4, a switch tube Q4, a resistor R5, and a resistor R7. Among them, the first connection terminal of the switch tube Q1 is connected to the node A, the second connection terminal thereof is connected to the node D, and the control terminal thereof is connected to the first connection terminal of the switch tube Q4 via the resistor R4; the second connection terminal of the switch tube Q4 is grounded, and the control terminal thereof is connected to the node G; one end of the resistor R7 is connected to the node G, and the other end thereof is grounded; one end of the resistor R5 is connected to the node G, and the other end thereof is connected to the node E (or the second output terminal of the main control circuit U2 (or the second control signal Control-2)).

[0031] exist Figure 5In the illustrated embodiment, the linear voltage regulator circuit 530 includes a switch Q2, a resistor R3, and a Zener diode D2. The switch Q2 has a first connection terminal connected to node D, another terminal connected to the output power supply terminal VOUT, and a control terminal connected to the cathode of the Zener diode D2. The anode of the Zener diode D2 is grounded. The resistor R3 has one terminal connected to the first connection terminal of the switch Q2, and another terminal connected to the control terminal of the switch Q2. Furthermore, the linear voltage regulator circuit 530 includes a capacitor C7, one terminal of which is connected to the second connection terminal of the switch Q2, and the other terminal of which is grounded.

[0032] Figure 5 The illustrated DC-DC converter circuit for reducing capacitor noise further includes a regulating circuit 540, which is connected between node A and the switch control circuit 520. The regulating circuit 540 includes a resistor R1, a voltage-stabilizing diode D1, a resistor R2, a resistor R6, a resistor R8, and a switch Q3. Resistor R1 has one end connected to node A and its other end connected to node C; the cathode of voltage-stabilizing diode D1 is connected to node C, and its anode is grounded; the first connection end of switch Q3 is connected to node C via resistor R2, its second connection end is grounded, and its control end is connected to node H; resistor R6 has one end connected to node H and its other end is grounded; resistor R8 has one end connected to node H and its other end connected to the first output end (or first control signal Control-1) of main control circuit U2; and node C is connected to the first connection end of switch Q1.

[0033] Figure 5 The DC-DC converter circuit for reducing capacitor noise shown in the figure also includes a resistor R9 and a resistor R10, wherein one end of the resistor R9 is connected to the node F, and the other end thereof is connected to the first output terminal (or the first control signal Control-1) of the main control circuit U2; one end of the resistor R10 is connected to the node F, and the other end thereof is grounded; the node F is connected to the enable terminal Enable of the DC-DC converter module (i.e., DCDC) U1. In addition, Figure 5 The DC-DC conversion circuit for reducing capacitor noise shown further includes a capacitor C8 , one end of the capacitor C8 is connected to the node F, and the other end thereof is grounded.

[0034] exist Figure 5In the specific embodiment shown, the switch transistor Q1 is a PNP transistor, and the first connection terminal, second connection terminal, and control terminal of the switch transistor Q1 are respectively the emitter, collector, and base of the PNP transistor; the switch transistor Q2 is an NPN transistor, and the first connection terminal, second connection terminal, and control terminal of the switch transistor Q2 are respectively the collector, emitter, and base of the NPN transistor; the switch transistor Q3 is an NPN transistor, and the first connection terminal, second connection terminal, and control terminal of the switch transistor Q3 are respectively the collector, emitter, and base of the NPN transistor; the switch transistor Q4 is an NPN transistor, and the first connection terminal, second connection terminal, and control terminal of the switch transistor Q4 are respectively the collector, emitter, and base of the NPN transistor.

[0035] Figure 5 The DC-DC conversion circuit for reducing capacitor noise shown in the figure also includes an anti-reverse diode D3 and an anti-reverse diode D4. Among them, the positive pole of the anti-reverse diode D3 is connected to the input power supply terminal VIN, and its negative pole is connected to node A; the positive pole of the anti-reverse diode D4 is connected to node A, and its negative pole is connected to the input terminal Vin_dcdc of the DC-DC conversion module (i.e., DCDC) U1 through the first filter circuit 550. The anti-reverse diode D3 plays a reverse connection protection role when the input power supply terminal VIN is reversely connected. The function of the anti-reverse diode D4 is that when the voltage of the input power supply terminal VIN is reduced, the charge on the capacitor at the back end of the anti-reverse diode D4 (for example, capacitors C1, C2, C3, C4) will not be reversely injected back into the input power supply terminal VIN.

[0036] The resistance values of the resistors R6 and R8 are selected to satisfy the following conditions: when the first control signal Control-1 is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the switch tube Q3, so that the switch tube Q3 is in the on state; the resistance values of the resistors R5 and R7 are selected to satisfy the following conditions: when the second control signal Control-2 is at a high level, the voltage value of the node G is greater than the turn-on voltage value of the switch tube Q4, so that the switch tube Q4 is in the on state; the resistance values of the resistors R9 and R10 are selected to satisfy the following conditions: when the first control signal Control-1 is at a high level, the voltage value of the node F is greater than the turn-on voltage threshold of the DC-DC conversion module U1, so that the DC-DC conversion module U1 is in operation.

[0037] The following is a detailed introduction Figure 5 The working principle of the DC-DC conversion circuit for reducing capacitor noise is shown.

[0038] When the main control circuit U2 detects based on the sampled voltage that the voltage of 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 first control signal Control-1 outputted by its first output terminal to be high, and controls the second control signal Control-2 outputted by its second output terminal to be low. Since the resistance values of resistors R9 and R10 are selected to satisfy the following conditions: when the first control signal Control-1 is high, the voltage value at node F is greater than the turn-on voltage threshold of the DC-DC converter module U1. Therefore, when the first control signal Control-1 is high, the DC-DC converter module U1 operates. Since the resistance values of resistors R6 and R8 are selected to ensure that, when the first control signal Control-1 is high, the voltage at node H is greater than the turn-on voltage of transistor Q3, transistor Q3 is turned on when the first control signal Control-1 is high. Resistor R2 acts as a shunt, reducing the current flowing through Zener diode D1, thereby reducing power consumption and heat generation. Zener diode D1 functions as a voltage regulator. A suitable voltage regulator value must be selected based on actual design to ensure that Zener diode D1 functions as a voltage regulator when the voltage at node C is greater than a certain voltage. The voltage regulator value must also consider the power consumption of Zener diode D1 itself and the power consumption of downstream transistors Q1 and Q2 when they are turned on. When the second control signal Control-2 is low, i.e., node G is low, the voltage at node G is less than the turn-on voltage of transistor Q4, and transistor Q4 is turned off (or switched off), thereby turning transistor Q1 off (or switched off). In the three-linear voltage regulator circuit 530, the voltage regulator D2 needs to be selected according to the voltage value of the output power supply terminal VOUT. When the transistor Q1 is closed (or turned off), the linear voltage regulator circuit 530 will not work.

[0039] That is, when the main control circuit U2 detects, based on the sampled voltage output by the voltage sampling circuit 510, that the voltage of 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 no AC voltage is superimposed on the input power terminal VIN, the first control signal Control-1 output by the main control circuit U2 enables the DC-DC conversion module U1 to operate; the first control signal Control-1 output by the main control circuit U2 controls the switch tube Q3 to turn on; the second control signal Control-2 output by the main control circuit U2 controls the switch tube Q4 to turn off, thereby turning off the switch tube Q1 (i.e., the second control signal Control-2 output by the main control circuit U2 controls the switch control circuit 520 to cut off the connection between node A and node D), so that the linear voltage regulator circuit 530 does not operate. At this time, the DC-DC conversion module U1 is in an operating state, the output power terminal VOUT is powered only by the DC-DC conversion module U1, and the circuit can operate normally.

[0040] 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 first control signal control-1 output from its first output terminal to be low level and the second control signal control-2 output from its second output terminal to be high level through judgment logic. The specific judgment logic is as follows: Figure 6 shown.

[0041] 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 6 The 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.

[0042] 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].

[0043] Step 620 : Determine whether VIN_filter_max − VIN_filter_min < 1v. If not, return to step 610 ; if yes, proceed to step 630 .

[0044] 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.

[0045] Step 640: Determine whether all of the following conditions are met simultaneously:

[0046] ①VIN_original_max-VIN_filter_average>1v;

[0047] ②VIN_filter_average-VIN_filter_min>1v;

[0048] ③VIN_original_max-VIN_filter_min>2V.

[0049] If not (No), return to step 610; if yes (Yes), execute step 650.

[0050] In step 650, the MCU GPIO Control-1 outputs a low level and Control-2 outputs a high level. That is, the first control signal Control-1 outputted from the first output terminal of the main control circuit U2 is a low level, and the second control signal Control-2 outputted from the second output terminal is a high level. Then, the process returns to step 610. The above parameters can be adjusted according to actual usage requirements.

[0051] 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.

[0052] 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.

[0053] When the main control circuit U2 detects the AC voltage superimposed on the input power supply terminal VIN based on the sampled voltage, the main control circuit U2 controls the first control signal Control-1 output from its first output terminal to be low level, and controls the second control signal Control-2 output from its second output terminal to be high level. When the first control signal Control-1 is low level, that is, node F and node H are low level. Since node F is low level, the voltage of node F is less than the turn-on voltage threshold of the DC-DC conversion module U1, so that the DC-DC conversion module U1 is turned off and is in an inoperative state. Since node H is low level, the voltage of node H is less than the turn-on voltage value of the transistor Q3, so that the transistor Q3 is in a closed (or turned-off) state. Since the resistance values of the resistor R5 and the resistor R7 are selected to meet the following requirements: when the second control signal Control-2 is high level, the voltage value of the node G is greater than the turn-on voltage value of the switch tube Q4, therefore,

[0054] When the second control signal Control-2 is high, transistor Q4 is turned on, the base of transistor Q1 is low, and the emitter of Q1 is high. Therefore, transistor Q1 is turned on, and node D is high. In the linear voltage regulator circuit 530, the selection of the voltage regulator D2 is related to the voltage value of the output power terminal VOUT. When node D is high, the output of the linear voltage regulator circuit 530 is the voltage value required by the output power terminal VOUT. At this time, the output power terminal VOUT is powered by the input power terminal VIN through the diode D3, the resistor R1, the transistor Q1, and the transistor Q2. The DC-DC converter module (i.e., the DCDC chip) U1 is turned off, and the ripple voltage between the input power terminal VIN and the output power terminal VOUT is reduced, thereby reducing the ripple voltage value superimposed on the input capacitors (e.g., capacitors C1, C2, C3, C4) and the output capacitors (e.g., capacitors C5, C6), thereby reducing capacitor noise.

[0055] That is to say, when the main control circuit U2 detects that the AC voltage is superimposed on the input power supply terminal VIN based on the sampled voltage output by the voltage sampling circuit 510, the first control signal Control-1 output by the main control circuit U2 causes the DC-DC conversion module (i.e., DCDC) U1 to stop working; the first control signal Control-1 output by the main control circuit U2 controls the switch tube Q3 to turn off; the second control signal Control-2 output by the main control circuit U2 controls the switch tube Q4 to turn on, thereby turning on the switch tube Q1 (i.e., the second control signal Control-2 output by the main control circuit U2 controls the switch control circuit 520 to connect node A and node D), so that the linear voltage regulator circuit 530 works. At this time, the DC-DC conversion module (i.e., DCDC) U1 is in a non-working state, and the output power supply terminal VOUT is only powered by the linear voltage regulator circuit 530.

[0056] In summary, the present invention detects the input voltage value of the input power terminal VIN and uses a software algorithm to determine whether a superimposed AC voltage exists. When a superimposed AC voltage exists, the DC-DC converter module U1 (or DCDC chip) is disabled, thereby reducing the ripple voltage at the input power terminal VIN and the output power terminal VOUT. This reduces the ripple voltage superimposed on the input capacitor and the output capacitor, thereby reducing capacitor noise.

[0057] Compared with the prior art, the DC-DC conversion circuit for reducing capacitor howling provided by the present invention has the following beneficial effects:

[0058] 1. The DC-DC conversion circuit for reducing capacitor howling provided by the present invention is implemented in conjunction with software judgment, and has a lower cost compared to the solution of bracket capacitors.

[0059] 2. The DC-DC conversion circuit for reducing capacitor howling provided by the present invention is more reliable and can better suppress capacitor howling compared to 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.

[0060] 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 DC-DC conversion circuit for reducing capacitor noise, 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, whose first output end outputs a first control signal, and whose second output end outputs a second control signal, wherein the main control circuit outputs the first control signal and the second control signal based on the sampled voltage; a DC-DC conversion module, whose input terminal is connected to the node A, whose output terminal is connected to the output power terminal VOUT, and whose enable terminal is connected to the first output terminal of the main control circuit, wherein the DC-DC conversion module is used to convert the first DC power supply into a second DC power supply; a switch control circuit, having a first connection terminal connected to the node A, a second connection terminal connected to the node D, and a control terminal connected to the second output terminal of the main control circuit; A linear voltage stabilizing circuit has a first connection end connected to the node D and a second connection end connected to the output power supply end VOUT, and the linear voltage stabilizing circuit is used to provide a stable voltage to the output power supply end VOUT.

2. The DC-DC converter circuit for reducing capacitor noise according to claim 1, wherein: 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 main control circuit outputs a first control signal to enable the DC-DC conversion module to operate, and the main control circuit outputs a second control signal to control the switch control circuit to cut off the connection between the node A and the node D, so that the linear voltage regulator circuit does not operate; When the main control circuit detects, based on the sampled voltage, that an AC voltage is superimposed on the input power supply terminal VIN, the first control signal output by the main control circuit disables the DC-DC conversion module, and the second control signal output by the main control circuit controls the switch control circuit to connect the node A and the node D, so that the linear voltage regulator circuit operates.

3. The DC-DC converter circuit for reducing capacitor noise according to claim 2, wherein: The switch control circuit includes a switch tube Q1, a resistor R4, a switch tube Q4, a resistor R5, and a resistor R7. The first connection end of the switch tube Q1 is connected to the node A, the second connection end thereof is connected to the node D, and the control end thereof is connected to the first connection end of the switch tube Q4 via the resistor R4; the second connection end of the switch tube Q4 is grounded, and the control end thereof is connected to the node G; one end of the resistor R7 is connected to the node G, and the other end thereof is grounded; one end of the resistor R5 is connected to the node G, and the other end thereof is connected to the second output end of the main control circuit.

4. The DC-DC conversion circuit for reducing capacitor noise according to claim 3, wherein: The linear voltage stabilization circuit includes a switch tube Q2, a resistor R3 and a voltage stabilization diode D2. The first connection end of the switch tube Q2 is connected to the node D, the other end thereof is connected to the output power supply end VOUT, and the control end thereof is connected to the cathode of the voltage-stabilizing diode D2; the anode of the voltage-stabilizing diode D2 is grounded, one end of the resistor R3 is connected to the first connection end of the switch tube Q2, and the other end thereof is connected to the control end of the switch tube Q2.

5. The DC-DC conversion circuit for reducing capacitor noise according to claim 4, wherein: It also includes a regulating circuit, The regulating circuit includes a resistor R1, a voltage stabilizing diode D1, a resistor R2, a resistor R6, a resistor R8 and a switch tube Q3. One end of the resistor R1 is connected to the node A, and the other end thereof is connected to the node C; the cathode of the voltage stabilizing diode D1 is connected to the node C, and the anode thereof is grounded; the first connection end of the switch tube Q3 is connected to the node C via the resistor R2, the second connection end thereof is grounded, and the control end thereof is connected to the node H; 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 H, and the other end thereof is connected to the first output end of the main control circuit; the node C is connected to the first connection end of the switch tube Q1.

6. The DC-DC conversion circuit for reducing capacitor noise according to claim 5, wherein: 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 first control signal output by the main control circuit controls the switch tube Q3 to be turned on, and the second control signal output by the main control circuit controls the switch tube Q4 to be turned off, thereby turning off the switch tube Q1; When the main control circuit detects that an AC voltage is superimposed on the power supply terminal VIN based on the sampled voltage, the first control signal output by the main control circuit controls the switch tube Q3 to be turned off, and the second control signal output by the main control circuit controls the switch tube Q4 to be turned on, thereby turning on the switch tube Q1.

7. The DC-DC conversion circuit for reducing capacitor noise according to claim 6, wherein: The switch tube Q1 is a PNP type triode, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q1 are respectively the emitter, the collector and the base of the PNP type triode; The switch tube Q2 is an NPN transistor, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q2 are respectively the collector, the emitter and the base of the NPN transistor; The switch tube Q3 is an NPN transistor, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q3 are respectively the collector, the emitter and the base of the NPN transistor; The switch tube Q4 is an NPN transistor, and the first connection terminal, the second connection terminal and the control terminal of the switch tube Q4 are respectively the collector, the emitter and the base of the NPN transistor.

8. The DC-DC conversion circuit for reducing capacitor noise according to claim 7, wherein: It also includes resistors R9 and R10, One end of the resistor R9 is connected to the node F, and the other end thereof is connected to the first output end of the main control circuit; One end of the resistor R10 is connected to the node F, and the other end thereof is grounded; The node F is connected to the enable terminal of the DC-DC conversion module.

9. The DC-DC conversion circuit for reducing capacitor noise according to claim 8, wherein: The resistance values of the resistor R6 and the resistor R8 are selected so that when the first control signal is at a high level, the voltage value of the node H is greater than the turn-on voltage value of the switch tube Q3, so that the switch tube Q3 is in a conducting state; The resistance values of the resistor R5 and the resistor R7 are selected so that when the second control signal is at a high level, the voltage value of the node G is greater than the turn-on voltage value of the switch tube Q4, so that the switch tube Q4 is in a conducting state; The resistance values of the resistor R9 and the resistor R10 are selected to satisfy the following requirement: when the first control signal is at a high level, the voltage value of the node F is greater than the start-up voltage threshold of the DC-DC conversion module, so that the DC-DC conversion module operates.

10. The DC-DC conversion circuit for reducing capacitor noise according to claim 1, wherein: The voltage sampling circuit includes a resistor R11 and a resistor R12. One end of the resistor R11 is connected to the node A, and the other end thereof is connected to the node B; one end of the resistor R12 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.

11. The DC-DC conversion circuit for reducing capacitor howling according to any one of claims 1 to 10, characterized in that: It also includes a first filtering circuit and a second filtering circuit, The first filtering circuit is connected between the node A and the input end of the DC-DC conversion module, and the first filtering circuit includes a capacitor; The second filtering circuit is connected to the output terminal of the DC-DC conversion module and the output power terminal VOUT, and the second filtering circuit includes a capacitor.

12. The DC-DC conversion circuit for reducing capacitor noise according to claim 11, wherein: It also includes anti-reverse diode D3 and anti-reverse diode D4, The positive electrode of the anti-reverse diode D3 is connected to the input power supply terminal VIN, and the negative electrode thereof is connected to the node A; The positive electrode of the anti-reverse diode D4 is connected to the node A, and the negative electrode thereof is connected to the input end of the DC-DC conversion module via the first filtering circuit.

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