A filter circuit and a bridge rectifier circuit

Abstract

The present invention provides a filtering circuit, comprising a first filtering capacitor, a voltage detection module, a second filtering capacitor, a third filtering capacitor, a control module, and a fourth filtering capacitor; the voltage detection module is used to detect the output signal of the circuit to be filtered, obtain a detection signal and send the detection signal to the control module; the control module is used to receive the detection signal, and when the detection signal is a low voltage signal, control the second filtering capacitor and the third filtering capacitor to form a parallel relationship, and when the detection signal is a high voltage signal, control the second filtering capacitor and the third filtering capacitor to form a series relationship, thereby effectively reducing the size of the capacitor used while ensuring high withstand voltage and large capacity, and solving the problem that the size of the filter capacitor is too large and the finished bridge rectifier circuit is too large when the AC input voltage range of the existing bridge rectifier circuit is large.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a filter circuit and a bridge rectifier circuit. Background Art

[0002] The prior art uses a filter capacitor to shape the rectified waveform output by the bridge rectifier circuit to obtain a smooth direct current. The withstand voltage of the filter capacitor is determined by the AC input voltage, and the capacity of the filter capacitor is determined by the output power. The higher the AC input voltage, the higher the withstand voltage of the required filter capacitor, and the lower the AC input voltage, the larger the capacity of the required filter capacitor. When the range of the AC input voltage is relatively large, the withstand voltage of the filter capacitor is very high and the capacity is very large, which will cause the size of the filter capacitor to be very large, and thus make the finished product of the bridge rectifier circuit very large. Summary of the invention

[0003] The present invention provides a filter circuit and a bridge rectifier circuit to solve the problems that the filter capacitor is too large and the finished product of the bridge rectifier circuit is too large when the AC input voltage range of the existing bridge rectifier circuit is large.

[0004] The present invention is implemented in this way: a filter circuit comprises:

[0005] A first filter capacitor, a voltage detection module, a second filter capacitor, a third filter capacitor, a control module, and a fourth filter capacitor;

[0006] A common point among the positive electrode of the first filter capacitor, the first end of the voltage detection module, the positive electrode of the second filter capacitor and the first end of the control module serves as the first end of the filter circuit;

[0007] The second end of the voltage detection module is connected to the second end of the control module;

[0008] The negative electrode of the second filter capacitor is connected to the third terminal of the control module;

[0009] The fourth end of the control module is connected to the positive electrode of the third filter capacitor, and the fifth end is connected to the first end of the fourth filter capacitor;

[0010] A common point among the negative electrode of the first filter capacitor, the third end of the voltage detection module, the negative electrode of the third filter capacitor, the second end of the fourth filter capacitor, and the sixth end of the control module serves as the second end of the filter circuit;

[0011] The first end of the filter circuit is used to connect to the output end of the circuit to be filtered, and the second end of the filter circuit is used to be grounded;

[0012] The voltage detection module is used to detect the output signal of the circuit to be filtered, obtain a detection signal and send the detection signal to the control module; the control module is used to receive the detection signal, and when the detection signal is a low voltage signal, control the second filter capacitor and the third filter capacitor to form a parallel relationship, and when the detection signal is a high voltage signal, control the second filter capacitor and the third filter capacitor to form a series relationship.

[0013] Optionally, the first filter capacitor is a high-voltage and low-capacity electrolytic capacitor, and the second filter capacitor and the third filter capacitor are low-voltage electrolytic capacitors.

[0014] Optionally, the control module includes:

[0015] A control unit, a first switch tube, a second switch tube, and a third switch tube;

[0016] The first end of the control unit serves as the second end of the control module, the second end is connected to the first end of the first switch tube, the third end is connected to the first end of the third switch tube, the fourth end is connected to the first end of the second switch tube, and the fifth end serves as the fifth end of the control module;

[0017] The common point between the second end of the first switch tube and the second end of the third switch tube serves as the third end of the control module; the common point between the third end of the first switch tube and the sixth end of the control unit serves as the sixth end of the control module;

[0018] The second end of the second switch tube serves as the first end of the control module; the common point between the third end of the second switch tube and the third end of the third switch tube serves as the fourth end of the control module;

[0019] The control unit is used to receive the detection signal, and when the detection signal is a low voltage signal, control the first switch tube and the second switch tube to be turned on so that the second filter capacitor and the third filter capacitor are in a parallel relationship, and when the detection signal is a high voltage signal, control the third switch tube to be turned on so that the second filter capacitor and the third filter capacitor are in a series relationship.

[0020] Optionally, the first switch tube, the second switch tube, and the third switch tube are NMOS tubes respectively;

[0021] The gate of the first switch tube is connected to the second end of the control unit, the gate of the second switch tube is connected to the fourth end of the control unit, and the gate of the third switch tube is connected to the third end of the control unit;

[0022] The common point between the drain of the first switch tube and the drain of the third switch tube serves as the third terminal of the control module; the common point between the source of the first switch tube and the sixth terminal of the control unit serves as the sixth terminal of the control module;

[0023] The drain of the second switch tube serves as the first end of the control module, and the common node between the source of the second switch tube and the source of the third switch tube serves as the fourth end of the control module.

[0024] Optionally, the voltage detection circuit is composed of a plurality of resistors connected in series;

[0025] The first end of the first resistor serves as the first end of the voltage detection module, the second end of the last resistor serves as the third end of the voltage detection module, and any series connection point between resistors serves as the second end of the voltage detection module.

[0026] Optionally, the voltage detection module includes a first resistor, a second resistor, and a third resistor;

[0027] The first resistor serves as the first end of the voltage detection module, the second section of the first resistor is connected to the first end of the second resistor, the common point between the second end of the second resistor and the first end of the third resistor serves as the second end of the voltage detection module; the second end of the third resistor serves as the third end of the voltage detection module.

[0028] A bridge rectifier circuit, comprising a rectifier bridge and a filter circuit as described in any one of the above items;

[0029] The first end of the rectifier bridge is connected to the live wire, the second end is connected to the neutral wire, the third end is connected to the first end of the filter circuit, and the fourth end and the second end of the filter circuit are connected to the ground.

[0030] Optionally, the maximum withstand voltage of the first filter capacitor is 400V, the capacity is 27μF, and the size is 10*17mm; the maximum withstand voltage of the second filter capacitor and the third filter capacitor is 200V, the capacity is 47μF, and the size is 10*17mm.

[0031] The filter circuit provided by the present invention comprises a first filter capacitor, a voltage detection module, a second filter capacitor, a third filter capacitor, a control module and a fourth filter capacitor; a common point among the positive electrode of the first filter capacitor, the first end of the voltage detection module, the positive electrode of the second filter capacitor and the first end of the control module serves as the first end of the filter circuit; the second end of the voltage detection module is connected to the second end of the control module; the negative electrode of the second filter capacitor is connected to the third end of the control module; the fourth end of the control module is connected to the positive electrode of the third filter capacitor, and the fifth end is connected to the first end of the fourth filter capacitor; the negative electrode of the first filter capacitor, the third end of the voltage detection module, the negative electrode of the third filter capacitor, the The common point between the second end of the fourth filter capacitor and the sixth end of the control module serves as the second end of the filter circuit; the first end of the filter circuit is used to connect the output end of the circuit to be filtered, and the second end of the filter circuit is used to be grounded; the voltage detection module is used to detect the output signal of the circuit to be filtered, obtain a detection signal and send the detection signal to the control module; the control module is used to receive the detection signal, and when the detection signal is a low voltage signal, control the second filter capacitor and the third filter capacitor to form a parallel relationship, and when the detection signal is a high voltage signal, control the second filter capacitor and the third filter capacitor to form a series relationship; thereby effectively reducing the size of the capacitor used while ensuring high withstand voltage and large capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 is a schematic diagram of a filter circuit provided by an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of a control module in a filter circuit provided by an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of a filter circuit provided by another embodiment of the present invention;

[0036] Figure 4 Schematic diagram of a bridge rectifier circuit provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] The filter circuit provided by the present invention includes a first filter capacitor, a voltage detection module, a second filter capacitor, a third filter capacitor, a control module, and a fourth filter capacitor. The output signal of the circuit to be filtered is detected by the voltage detection module, and the connection relationship between the second filter capacitor and the third filter capacitor is changed to a parallel relationship or a series relationship according to the level of the detection signal by the control module, thereby effectively reducing the size of the capacitor used while ensuring high withstand voltage and large capacity.

[0039] Figure 1 Schematic diagram of a filter circuit 1 provided in an embodiment of the present invention. Figure 1 As shown, the filtering circuit 1 comprises:

[0040] A first filter capacitor EC1, a voltage detection module 10, a second filter capacitor EC2, a third filter capacitor EC3, a control module 20, and a fourth filter capacitor C1;

[0041] The common point between the positive electrode of the first filter capacitor EC1, the first end of the voltage detection module 10, the positive electrode of the second filter capacitor EC2 and the first end p1 of the control module 20 serves as the first end of the filter circuit 1;

[0042] The second end of the voltage detection module 10 is connected to the second end p2 of the control module 20;

[0043] The negative electrode of the second filter capacitor EC2 is connected to the third terminal p3 of the control module 20;

[0044] The fourth terminal p4 of the control module 20 is connected to the positive electrode of the third filter capacitor EC3, and the fifth terminal p5 is connected to the first terminal of the fourth filter capacitor C1;

[0045] The common point among the negative electrode of the first filter capacitor EC1, the third terminal of the voltage detection module 10, the negative electrode of the third filter capacitor EC3, the second terminal of the fourth filter capacitor C1, and the sixth terminal p6 of the control module 20 serves as the second terminal of the filter circuit 1;

[0046] The first end of the filter circuit 1 is used to connect to the output end of the circuit to be filtered, and the second end of the filter circuit 1 is used to ground GND;

[0047] The voltage detection module 10 is used to detect the output signal of the circuit to be filtered, obtain a detection signal and send the detection signal to the control module 20; the control module 20 is used to receive the detection signal, and when the detection signal is a low voltage signal, control the second filter capacitor EC2 and the third filter capacitor EC3 to form a parallel relationship, and when the detection signal is a high voltage signal, control the second filter capacitor EC2 and the third filter capacitor EC3 to form a series relationship.

[0048] In an embodiment of the present invention, the first filter capacitor EC1 is a high-voltage low-capacity electrolytic capacitor, and the second filter capacitor EC2 and the third filter capacitor EC3 are low-voltage electrolytic capacitors. The embodiment of the present invention splits the filter capacitor used in the prior art into two low-voltage electrolytic capacitors and one high-voltage low-capacity electrolytic capacitor. The voltage signal output by the circuit to be filtered is first filtered by the first filter capacitor EC1, and then detected by the voltage detection module 10 to obtain a detection signal of the output signal of the circuit to be filtered, and the detection signal is sent to the control module 20; the control module 20 changes the connection relationship between the second filter capacitor EC2 and the third filter capacitor EC3 to a parallel relationship or a series relationship according to the level of the detection signal. The fourth filter capacitor C1 is used as the power supply filter of the control module 20.

[0049] Among them, when the detection signal is a low voltage signal, the control module 20 controls the second filter capacitor EC2 and the third filter capacitor EC3 to form a parallel relationship. At this time, the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3 form a parallel relationship. The total capacity of the filter circuit 1 is the sum of the capacities of the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3, that is, C 总 =EC1+EC2+EC3, the withstand voltage of the filter circuit 1 is the withstand voltage of the second filter capacitor EC2 or the third filter capacitor EC3, thereby effectively solving the requirement for large capacity of the filter capacitor.

[0050] When the detection signal is a high voltage signal, the control module 20 controls the second filter capacitor EC2 and the third filter capacitor EC3 to form a series relationship. At this time, the second filter capacitor EC2 and the third filter capacitor EC3 form a series relationship. The total capacity of the filter circuit 1 is the sum of the series capacity of the second filter capacitor EC2 and the third filter capacitor EC3 and the capacity of the first filter capacitor EC1, that is, C 总=EC1+(EC2*EC3) / (EC2+EC3), the withstand voltage of the filter circuit 1 is the sum of the withstand voltages of the second filter capacitor EC2 and the third filter capacitor EC3. In the embodiment of the present invention, the second filter capacitor EC2 and the third filter capacitor EC3 are both low-voltage electrolytic capacitors, and the size of a single low-voltage electrolytic capacitor is relatively small, usually only 1 / 4 of that of a high-voltage and high-capacity electrolytic capacitor, thereby effectively solving the problem of the filter capacitor being too large under high-voltage and high-capacity conditions.

[0051] Optionally, as an implementation example of the present invention, Figure 2 As shown, the control module 20 includes:

[0052] A control unit 21, a first switch tube 22, a second switch tube 23, and a third switch tube 24;

[0053] The first end d1 of the control unit 21 serves as the second end p2 of the control module 20, the second end d2 is connected to the first end of the first switch tube 22, the third end d3 is connected to the first end of the third switch tube 24, the fourth end d4 is connected to the first end of the second switch tube 23, and the fifth end d5 serves as the fifth end p5 of the control module 20;

[0054] The common point between the second end of the first switch tube 22 and the second end of the third switch tube 24 serves as the third end p3 of the control module 20; the common point between the third end of the first switch tube 22 and the sixth end d6 of the control unit 21 serves as the sixth end p6 of the control module 20;

[0055] The second end of the second switch tube 23 serves as the first end p1 of the control module 20; the common point between the third end of the second switch tube 23 and the third end of the third switch tube 24 serves as the fourth end p4 of the control module 20;

[0056] The control unit is used to receive the detection signal, and when the detection signal is a low voltage signal, controls the first switch tube 22 and the second switch tube 23 to be turned on, so that the second filter capacitor EC2 and the third filter capacitor EC3 are in a parallel relationship, and when the detection signal is a high voltage signal, controls the third switch tube 24 to be turned on, so that the second filter capacitor EC2 and the third filter capacitor EC3 are in a series relationship.

[0057] In the embodiment of the present invention, the first ends of the first switch tube 22, the second switch tube 23, and the third switch tube 24 are respectively used as control ends of the first switch tube 22, the second switch tube 23, and the third switch tube 24, and are connected to the control unit 21. The control unit 21 receives the detection signal through the first end d1 and performs high and low voltage judgment on the detection signal.

[0058] When the detection signal is a low voltage signal, the control unit 21 generates a conduction signal for the first switch tube 22 and the second switch tube 23, so that the first switch tube 22 and the second switch tube 23 are turned on; when the first switch tube 22 and the second switch tube 23 are turned on, the second filter capacitor EC2 and the third filter capacitor EC3 form a parallel relationship. At this time, the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3 are connected in parallel with each other, and the total capacity of the filter circuit 1 is the sum of the capacities of the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3, that is, C 总 =EC1+EC2+EC3, the withstand voltage of the filter circuit 1 is the withstand voltage of the second filter capacitor EC2 or the third filter capacitor EC3, thereby effectively solving the requirement for large capacity of the filter capacitor.

[0059] When the detection signal is a high voltage signal, the control unit 21 generates a turn-on signal for the third switch tube 24 to turn on the third switch tube 24; when the third switch tube 24 is turned on, the second filter capacitor EC2 and the third filter capacitor EC3 form a series relationship. At this time, the second filter capacitor EC2 and the third filter capacitor EC3 are connected in series and then in parallel with the first filter capacitor EC1. The total capacity of the filter circuit 1 is the sum of the series capacity of the second filter capacitor EC2 and the third filter capacitor EC3 and the capacity of the first filter capacitor EC1, that is, C 总 =EC1+(EC2*EC3) / (EC2+EC3), the withstand voltage of the filter circuit 1 is the sum of the withstand voltages of the second filter capacitor EC2 and the third filter capacitor EC3. In the embodiment of the present invention, the second filter capacitor EC2 and the third filter capacitor EC3 are both low-voltage electrolytic capacitors, and the size of a single low-voltage electrolytic capacitor is relatively small, usually only 1 / 4 of that of a high-voltage and high-capacity electrolytic capacitor, thereby effectively solving the problem of the filter capacitor being too large under high-voltage and high-capacity conditions.

[0060] Optionally, as a preferred example of the present invention, Figure 2 As shown, the first switch tube 22, the second switch tube 23, and the third switch tube 24 are NMOS tubes respectively;

[0061] The gate G of the first switch tube 22 is connected to the second end d2 of the control unit 21, the gate G of the second switch tube 23 is connected to the fourth end d4 of the control unit 21, and the gate G of the third switch tube 24 is connected to the third end d3 of the control unit 21;

[0062] The common point between the drain D of the first switch tube 22 and the drain D of the third switch tube 24 serves as the third terminal p3 of the control module 20; the common point between the source S of the first switch tube 22 and the sixth terminal d6 of the control unit 21 serves as the sixth terminal p6 of the control module 20;

[0063] The drain D of the second switch tube 23 serves as the first terminal p1 of the control module 20 , and the common node between the source S of the second switch tube 23 and the source S of the third switch tube 24 serves as the fourth terminal p4 of the control module 20 .

[0064] Here, the control unit 21 receives the detection signal through the first terminal d1, and performs high or low voltage judgment on the detection signal. When the detection signal is a low voltage signal, the control circuit 21 provides a high level to the first switch tube 22 and the second switch tube 23, so that the first switch tube 22 and the second switch tube 23 are turned on; when the first switch tube 22 and the second switch tube 23 are turned on, the second filter capacitor EC2 and the third filter capacitor EC3 form a parallel relationship.

[0065] When the detection signal is a high voltage signal, the control circuit 21 provides a high level to the third switch tube 24 to turn on the third switch tube 24; when the third switch tube 24 is turned on, the second filter capacitor EC2 and the third filter capacitor EC3 form a series relationship.

[0066] Optionally, as a preferred example of the present invention, the voltage detection circuit 10 is composed of a plurality of resistors connected in series;

[0067] The first end of the first resistor serves as the first end of the voltage detection module 10 , the second end of the last resistor serves as the third end of the voltage detection module 10 , and any series connection point between resistors serves as the second end of the voltage detection module 10 .

[0068] For ease of understanding, the following description will be made by taking the voltage detection module 10 as an example consisting of three resistors connected in series. Figure 3 As shown, the voltage detection module includes a first resistor R1, a second resistor R2, and a third resistor R3; wherein the first resistor R1 serves as the first end of the voltage detection module 10 to receive the output signal of the circuit to be filtered; the second end of the first resistor R2 is connected to the first end of the second resistor R2, and the common point between the second end of the second resistor R2 and the first end of the third resistor R3 serves as the second end of the voltage detection module 10 to output a detection signal to the control module 20; the second end of the third resistor R3 serves as the third end of the voltage detection module 10, and is connected to the ground together with the second end of the circuit to be filtered.

[0069] Here, after the output signal of the circuit to be filtered is divided by the first resistor R1, the second resistor R2, and the third resistor R3, a voltage drop is formed on the third resistor R3. The embodiment of the present invention uses the divided voltage signal on the third resistor R3 as a detection signal and provides it to the subsequent control module 20 for use.

[0070] The embodiment of the present invention also provides a bridge rectifier circuit, such as Figure 4 As shown, the bridge rectifier circuit includes a rectifier bridge 2 and the filter circuit 1 as described above;

[0071] The first end of the rectifier bridge 2 is connected to the live wire L, the second end is connected to the neutral wire N, the third end is connected to the first end of the filter circuit 1, and the fourth end and the second end of the filter circuit 1 are connected to the ground GND.

[0072] In the embodiment of the present invention, the filter circuit 1 is used to filter the output signal of the rectifier bridge 2. Specifically, the output signal of the rectifier bridge 2 is detected by the voltage detection module 10 to obtain a detection signal, and then the connection relationship between the second filter capacitor EC2 and the third filter capacitor EC3 is changed to a parallel relationship or a series relationship according to the level of the detection signal by the control module 20.

[0073] Among them, when the AC input signal is low, the output signal of the rectifier bridge 2 is a low voltage signal, and the control module 20 controls the second filter capacitor EC2 and the third filter capacitor EC3 to form a parallel relationship. At this time, the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3 form a parallel relationship, and the total capacity of the filter circuit 1 is the sum of the capacities of the first filter capacitor EC1, the second filter capacitor EC2 and the third filter capacitor EC3, that is, C 总 =EC1+EC2+EC3, the withstand voltage of the filter circuit 1 is the withstand voltage of the second filter capacitor EC2 or the third filter capacitor EC3, thereby effectively solving the requirement for large capacity of the filter capacitor; when the AC input signal is high, the output signal of the rectifier bridge 2 is a high voltage signal, and the control module 20 controls the second filter capacitor EC2 and the third filter capacitor EC3 to form a series relationship. At this time, the second filter capacitor EC2 and the third filter capacitor EC3 form a series relationship, and the total capacity of the filter circuit 1 is the sum of the series capacity of the second filter capacitor EC2 and the third filter capacitor EC3 and the capacity of the first filter capacitor EC1, that is, C 总=EC1+(EC2*EC3) / (EC2+EC3), the withstand voltage of the filter circuit 1 is the sum of the withstand voltages of the second filter capacitor EC2 and the third filter capacitor EC3. In the embodiment of the present invention, the second filter capacitor EC2 and the third filter capacitor EC3 are both low-voltage electrolytic capacitors, and the size of a single low-voltage electrolytic capacitor is relatively small, usually only 1 / 4 of that of a high-voltage and high-capacity electrolytic capacitor, thereby effectively solving the problem of the filter capacitor being too large under high-voltage and high-capacity conditions.

[0074] Optionally, as a preferred example of the present invention, taking a 65W flyback switching power supply as an example, the input voltage range of the rectifier bridge 2 is 100--240Vac, the filter capacitor selected in the prior art is 400V120uF, the size of the filter capacitor is 18*32mm, and the volume of the filter capacitor = 8138mm3. Through the filter circuit provided by the embodiment of the present invention, the first filter capacitor EC1 can select a high-voltage low-capacity electrolytic capacitor with a maximum withstand voltage of 400V, a capacity of 27μF, and a size of 10*17mm, and the second filter capacitor EC2 and the third filter capacitor EC3 can select low-voltage electrolytic capacitors with a maximum withstand voltage of 200V, a capacity of 47μF, and a size of 10*17mm. At this time, the volume of the first filter capacitor EC1, the second filter capacitor EC2, and the third filter capacitor EC3 is 1334*3=4002mm3, which is about 50% smaller than that of the high-voltage large-capacity electrolytic capacitor, thereby effectively reducing the size of the filter capacitor used in the rectifier bridge 2, and solving the problem that the size of the filter capacitor is too large and the finished bridge rectifier circuit is too large when the AC input voltage range of the existing bridge rectifier circuit is large.

[0075] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A filter circuit, characterized in that: include: A first filter capacitor, a voltage detection module, a second filter capacitor, a third filter capacitor, a control module, and a fourth filter capacitor; A common point among the positive electrode of the first filter capacitor, the first end of the voltage detection module, the positive electrode of the second filter capacitor and the first end of the control module serves as the first end of the filter circuit; The second end of the voltage detection module is connected to the second end of the control module; The negative electrode of the second filter capacitor is connected to the third terminal of the control module; The fourth end of the control module is connected to the positive electrode of the third filter capacitor, and the fifth end is connected to the first end of the fourth filter capacitor; A common point among the negative electrode of the first filter capacitor, the third end of the voltage detection module, the negative electrode of the third filter capacitor, the second end of the fourth filter capacitor, and the sixth end of the control module serves as the second end of the filter circuit; The first end of the filter circuit is used to connect to the output end of the circuit to be filtered, and the second end of the filter circuit is used to be grounded; The voltage detection module is used to detect the output signal of the circuit to be filtered, obtain a detection signal and send the detection signal to the control module; the control module is used to receive the detection signal, and when the detection signal is a low voltage signal, control the second filter capacitor and the third filter capacitor to form a parallel relationship, and when the detection signal is a high voltage signal, control the second filter capacitor and the third filter capacitor to form a series relationship; The control module includes a control unit, a first switch tube, a second switch tube, and a third switch tube; The first end of the control unit serves as the second end of the control module, the second end is connected to the first end of the first switch tube, the third end is connected to the first end of the third switch tube, the fourth end is connected to the first end of the second switch tube, and the fifth end serves as the fifth end of the control module; The common point between the second end of the first switch tube and the second end of the third switch tube serves as the third end of the control module; the common point between the third end of the first switch tube and the sixth end of the control unit serves as the sixth end of the control module; The second end of the second switch tube serves as the first end of the control module; the common point between the third end of the second switch tube and the third end of the third switch tube serves as the fourth end of the control module; The control unit is used to receive the detection signal, and when the detection signal is a low voltage signal, control the first switch tube and the second switch tube to be turned on so that the second filter capacitor and the third filter capacitor are in a parallel relationship, and when the detection signal is a high voltage signal, control the third switch tube to be turned on so that the second filter capacitor and the third filter capacitor are in a series relationship.

2. The filter circuit according to claim 1, characterized in that: The first filter capacitor is a high-voltage and low-capacity electrolytic capacitor, and the second filter capacitor and the third filter capacitor are low-voltage electrolytic capacitors.

3. The filter circuit according to claim 1, characterized in that: The first switch tube, the second switch tube, and the third switch tube are NMOS tubes respectively; The gate of the first switch tube is connected to the second end of the control unit, the gate of the second switch tube is connected to the fourth end of the control unit, and the gate of the third switch tube is connected to the third end of the control unit; The common point between the drain of the first switch tube and the drain of the third switch tube serves as the third terminal of the control module; the common point between the source of the first switch tube and the sixth terminal of the control unit serves as the sixth terminal of the control module; The drain of the second switch tube serves as the first end of the control module, and the common node between the source of the second switch tube and the source of the third switch tube serves as the fourth end of the control module.

4. The filter circuit according to any one of claims 1 to 3, characterized in that: The voltage detection circuit is composed of a plurality of resistors connected in series; The first end of the first resistor serves as the first end of the voltage detection module, the second end of the last resistor serves as the third end of the voltage detection module, and any series connection point between resistors serves as the second end of the voltage detection module.

5. The filter circuit according to claim 4, characterized in that: The voltage detection module includes a first resistor, a second resistor, and a third resistor; The first resistor serves as the first end of the voltage detection module, the second section of the first resistor is connected to the first end of the second resistor, the common point between the second end of the second resistor and the first end of the third resistor serves as the second end of the voltage detection module; the second end of the third resistor serves as the third end of the voltage detection module.

6. A bridge rectifier circuit, characterized in that: The bridge rectifier circuit comprises a rectifier bridge and a filter circuit as claimed in any one of claims 1 to 5; The first end of the rectifier bridge is connected to the live wire, the second end is connected to the neutral wire, the third end is connected to the first end of the filter circuit, and the fourth end and the second end of the filter circuit are connected to the ground.

7. The bridge rectifier circuit according to claim 6, characterized in that: The maximum withstand voltage of the first filter capacitor is 400V and the capacity is 27 The size is 10*17mm. The maximum withstand voltage of the second and third filter capacitors is 200V and the capacity is 47 , size is 10*17mm.

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