A filter circuit

Abstract

This disclosure relates to a filter circuit, including a capacitor discharge module, a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor; the capacitor discharge module includes a discharge resistor assembly and a discharge switch assembly, the discharge resistor assembly includes a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor; the two ends of the first capacitor are respectively connected to two power input terminals, the second end of the second capacitor is connected to the second end of the third capacitor, and the second end of the second capacitor is connected to a ground terminal; the two ends of the first discharge resistor are respectively connected to the first power input terminal of the two power input terminals and the first end of the discharge switch assembly, the two ends of the second discharge resistor are respectively connected to the second power input terminal of the two power input terminals and the second end of the discharge switch assembly, the two ends of the third discharge resistor are respectively connected to the third end of the discharge switch assembly and the ground terminal, and the two ends of the fourth discharge resistor are respectively connected to the fourth end of the discharge switch assembly and the ground terminal.

Description

Technical Field

[0001] This disclosure relates to the field of filtering technology, and in particular to a filtering circuit. Background Technology

[0002] Household appliances are controlled by an electronic control board, which receives power from an AC power input. At the front end of the AC input power supply, capacitors, inductors, and other components form an input / output EMC (Electromagnetic Compatibility) filter circuit to reduce external interference and improve the device's immunity. The capacitors in this filter circuit include differential-mode filter capacitors (X capacitors) and common-mode filter capacitors (Y capacitors).

[0003] National safety standards stipulate that after an appliance is powered off or its power cord is unplugged, the voltage at the L (live)-N (neutral), L-GND (live wire grounding), and N-GND (neutral wire grounding) terminals of the AC power input must discharge to less than 34V within one second to ensure safety and prevent electric shock. To meet these safety requirements, the following methods are commonly used: For X capacitors, a resistive load is added between L and N to discharge the X capacitor; for Y capacitors, a resistive load is added between L-GND and N-GND to discharge the Y capacitor. The voltage rating of these resistors must meet safety requirements, and dozens of resistors are often connected in series. Therefore, in these methods, using resistors to discharge X and Y capacitors means the resistive load is constantly online and consuming power in real time, which is detrimental to energy saving and hinders the achievement of low-power standby mode. Utility Model Content

[0004] In view of the aforementioned technical problems, this disclosure proposes a filtering circuit.

[0005] According to one aspect of the present disclosure, a filter circuit is provided, the filter circuit including a capacitor discharge module, a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor; the capacitor discharge module includes a discharge resistor assembly and a discharge switch assembly, the discharge resistor assembly including a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor; The two ends of the first capacitor are respectively connected to the two power input terminals, the two ends of the first capacitor are respectively connected to the two input terminals of the common mode inductor, the two output terminals of the common mode inductor are respectively connected to the first terminal of the second capacitor and the first terminal of the third capacitor, the second terminal of the second capacitor is connected to the second terminal of the third capacitor, and the second terminal of the second capacitor is connected to the ground terminal. The two ends of the first discharge resistor are respectively connected to the first power input terminal of the two power input terminals and the first terminal of the discharge switch assembly. The two ends of the second discharge resistor are respectively connected to the second power input terminal of the two power input terminals and the second terminal of the discharge switch assembly. The two ends of the third discharge resistor are respectively connected to the third terminal of the discharge switch assembly and the ground terminal. The two ends of the fourth discharge resistor are respectively connected to the fourth terminal of the discharge switch assembly and the ground terminal.

[0006] Optionally, the discharge switch assembly includes a first control switch, a second control switch, and a third control switch; one end of the first control switch is connected to a first end of the discharge switch assembly, and the other end of the first control switch is connected to a second end of the discharge switch assembly; one end of the second control switch is connected to the first end of the discharge switch assembly, and the other end of the second control switch is connected to a third end of the discharge switch assembly; one end of the third control switch is connected to the second end of the discharge switch assembly, and the other end of the third control switch is connected to a fourth end of the discharge switch assembly.

[0007] Optionally, the capacitor discharge module further includes a controller and a switch drive module. The controller is connected to the switch drive module, and the switch drive module includes a first drive circuit, a second drive circuit, and a third drive circuit. The output terminal of the first drive circuit is connected to the control signal input terminal of the first control switch, the output terminal of the second drive circuit is connected to the control signal input terminal of the second control switch, and the output terminal of the third drive circuit is connected to the control signal input terminal of the third control switch.

[0008] Optionally, the first control switch includes a first field-effect transistor and a second field-effect transistor, and the output terminal of the first driving circuit includes a first output terminal and a second output terminal; the source of the first field-effect transistor is connected to the source of the second field-effect transistor, the drain of the first field-effect transistor is connected to the first terminal of the discharge switch assembly, the drain of the second field-effect transistor is connected to the second terminal of the discharge switch assembly, the gate of the first field-effect transistor is connected to the first output terminal, and the gate of the second field-effect transistor is connected to the second output terminal.

[0009] Optionally, the second control switch includes a third field-effect transistor and a fourth field-effect transistor, and the output terminal of the second driving circuit includes a third output terminal and a fourth output terminal; the source of the third field-effect transistor is connected to the source of the fourth field-effect transistor, the drain of the third field-effect transistor is connected to the first terminal of the discharge switch assembly, the drain of the fourth field-effect transistor is connected to the third terminal of the discharge switch assembly, the gate of the third field-effect transistor is connected to the third output terminal, and the gate of the fourth field-effect transistor is connected to the fourth output terminal.

[0010] Optionally, the third control switch includes a fifth field-effect transistor and a sixth field-effect transistor, and the output terminal of the third driving circuit includes a fifth output terminal and a sixth output terminal; the source of the fifth field-effect transistor is connected to the source of the sixth field-effect transistor, the drain of the fifth field-effect transistor is connected to the second terminal of the discharge switch assembly, the drain of the sixth field-effect transistor is connected to the fourth terminal of the discharge switch assembly, the gate of the fifth field-effect transistor is connected to the fifth output terminal, and the gate of the sixth field-effect transistor is connected to the sixth output terminal.

[0011] Optionally, the capacitor discharge module further includes a power failure detection module, the output of which is connected to the controller.

[0012] Optionally, the power failure detection module includes a current detection unit and a power failure detection unit. The two input terminals of the current detection unit are located between the first power input terminal and the first capacitor. The output terminal of the current detection unit is connected to the input terminal of the power failure detection unit, and the output terminal of the power failure detection unit is connected to the controller.

[0013] Optionally, the discharge switch assembly is packaged using an integrated chip structure.

[0014] The technical solutions provided by the embodiments of this disclosure have at least the following beneficial effects: By incorporating a capacitor discharge module in the filter circuit, which includes a discharge resistor assembly and a discharge switch assembly, and the filter circuit comprising a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor; the discharge resistor assembly comprising a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor; the two ends of the first discharge resistor are connected to the first power input terminal and the first end of the discharge switch assembly, respectively; the two ends of the second discharge resistor are connected to the second power input terminal and the second end of the discharge switch assembly, respectively; the two ends of the third discharge resistor are connected to the third end of the discharge switch assembly and the ground terminal, respectively; and the two ends of the fourth discharge resistor are connected to the fourth end of the discharge switch assembly and the ground terminal, respectively. This allows for controllable discharge of the discharge resistor assembly, preventing continuous online operation and energy consumption, thus achieving energy saving and facilitating low-power standby operation of the equipment. Furthermore, the discharge resistor assembly can discharge the first, second, and third capacitors separately, enabling rapid discharge of these capacitors and expanding the range of capacitor capacity selection.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure, and are not intended to unduly limit this disclosure.

[0017] Figure 1 This is a schematic diagram of a filter circuit according to an exemplary embodiment; Figure 2 This is a circuit diagram of a capacitor discharge module according to an exemplary embodiment; Figure 3 This is a circuit diagram of a packaged capacitor discharge module according to an exemplary embodiment. Detailed Implementation

[0018] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0019] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0020] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0021] Please see Figure 1 , Figure 1 This is a schematic diagram of a filter circuit according to an exemplary embodiment. Specifically, the filter circuit may include a capacitor discharge module, a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor. The capacitor discharge module may include a discharge resistor assembly and a discharge switch assembly. The discharge resistor assembly may include a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor.

[0022] Furthermore, the two ends of the first capacitor can be connected to the two power input terminals respectively, the two ends of the first capacitor can be connected to the two input terminals of the common mode inductor respectively, the two output terminals of the common mode inductor can be connected to the first terminal of the second capacitor and the first terminal of the third capacitor respectively, the second terminal of the second capacitor and the second terminal of the third capacitor are connected, and the second terminal of the second capacitor is connected to the ground terminal.

[0023] Furthermore, the two ends of the first discharge resistor can be connected to the first power input terminal of the two power input terminals and the first terminal of the discharge switch assembly, respectively; the two ends of the second discharge resistor can be connected to the second power input terminal of the two power input terminals and the second terminal of the discharge switch assembly, respectively; the two ends of the third discharge resistor can be connected to the third terminal of the discharge switch assembly and the ground terminal, respectively; and the two ends of the fourth discharge resistor can be connected to the fourth terminal of the discharge switch assembly and the ground terminal, respectively.

[0024] Specifically, the first capacitor can refer to the X capacitor. The second and third capacitors can be Y capacitors.

[0025] In the above embodiments, by setting a capacitor discharge module in the filter circuit, the capacitor discharge module includes a discharge resistor assembly and a discharge switch assembly. The filter circuit includes a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor. The discharge resistor assembly includes a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor. The two ends of the first discharge resistor are respectively connected to the first power input terminal of the two power input terminals and the first end of the discharge switch assembly. The two ends of the second discharge resistor are respectively connected to the second power input terminal of the two power input terminals and the second end of the discharge switch assembly. The two ends of the third discharge resistor are respectively connected to the third end of the discharge switch assembly and the ground terminal. The two ends of the fourth discharge resistor are respectively connected to the fourth end of the discharge switch assembly and the ground terminal. This allows for controllable discharge of the discharge resistor assembly, avoiding continuous online operation that leads to energy consumption. This achieves energy saving and facilitates low-power standby operation of the equipment. In addition, the first, second, and third capacitors can be discharged separately by the discharge resistor assembly, enabling rapid discharge of the capacitors and thus expanding the range of capacitor capacity selection. Understandably, during the filtering process when the filter circuit is connected to the power supply, the switches in the aforementioned discharge switch assembly can be controlled to be disconnected, so that the discharge resistor assembly is not connected to the filter circuit, the discharge circuits of X capacitor and Y capacitor are open, no current flows, the discharge load loss is almost zero, achieving low standby power consumption of the whole machine, meeting the standby requirement of less than 0.5W, and reducing energy consumption; when the power supply is unplugged and offline, the discharge circuit is turned on, and the electrical energy on X capacitor and Y capacitor is quickly consumed and released through the Π-type X and Y capacitor discharge modules. The voltage between LN, L-GND, and N-GNG of the power plug is required to drop the voltage to below 34V within 1 second, meeting the safety standard requirements.

[0026] In a specific embodiment, based on the time parameter requirement of discharging within 1 second and having a voltage less than 34V, the discharge resistor and capacitor can be selected with reference to the relationship RC≤1 / 2.21. The power loss of the resistor can be calculated with reference to the formula P=U² / R. For example, capacitor X has C=3.3uF, R≤137K, and a total value of 100K is selected, using resistors RD1=50K and RD2=50K. According to the formula P=U² / R, the power loss is calculated as P=220² / 100K=0.484W; capacitor Y has C=4700pF. Since the value of capacitor Y is much smaller than that of capacitor X, its energy storage is much smaller than that of capacitor X, and using the same discharge load size as capacitor X fully meets the requirements. With this design, the standby power consumption of the circuit can be reduced by at least 0.484W.

[0027] In one specific embodiment, the X capacitor in the circuit can meet the capacitance requirement of 6uF, and the Y capacitor can meet the capacitance requirement of 0.022uF.

[0028] In one specific embodiment, the discharge switch assembly may include a first control switch, a second control switch, and a third control switch. Specifically, one end of the first control switch is connected to a first end of the discharge switch assembly, and the other end of the first control switch is connected to a second end of the discharge switch assembly. One end of the second control switch is connected to the first end of the discharge switch assembly, and the other end of the second control switch is connected to a third end of the discharge switch assembly. One end of the third control switch is connected to the second end of the discharge switch assembly, and the other end of the third control switch is connected to a fourth end of the discharge switch assembly.

[0029] In the above embodiments, the discharge process of the first capacitor, the second capacitor, and the third capacitor can be controlled by the first control switch, the second control switch, and the third control switch, respectively.

[0030] In one specific embodiment, the capacitor discharge module may further include a controller and a switch drive module. Specifically, the controller is connected to the switch drive module; the switch drive module may include a first drive circuit, a second drive circuit, and a third drive circuit. The output terminal of the first drive circuit is connected to the control signal input terminal of the first control switch, the output terminal of the second drive circuit is connected to the control signal input terminal of the second control switch, and the output terminal of the third drive circuit is connected to the control signal input terminal of the third control switch.

[0031] In one specific embodiment, the controller can generate a control signal and send it to the switch activation module. The drive circuit in the switch drive module can control the corresponding control switch to close or open based on the received control signal.

[0032] In one specific embodiment, for the discharge of the first capacitor, when the need for discharge is detected (i.e., when the power input is detected to be disconnected), the first control switch can be closed by the first drive circuit, and the first capacitor can be discharged through the first discharge resistor and the second discharge resistor.

[0033] In one specific embodiment, for the discharge of the second capacitor, when the need for discharge is detected (i.e., when the power input is detected to be disconnected), the second control switch can be closed by the second drive circuit. At this time, the second capacitor can form a discharge circuit through the ground terminal and discharge through the first discharge resistor and the third discharge resistor.

[0034] In one specific embodiment, for the discharge of the third capacitor, when the need for discharge is detected (i.e. when the power input is detected to be disconnected), the third control switch can be closed by the third drive circuit. At this time, the third capacitor can form a discharge circuit through the ground terminal and discharge through the second discharge resistor and the fourth discharge resistor.

[0035] In one specific embodiment Figure 2 This is a circuit diagram illustrating a capacitor discharge module according to an exemplary embodiment. Specifically, as shown below... Figure 2 As shown, the first control switch may include a first field-effect transistor Q1 and a second field-effect transistor Q2; the output terminal of the first driving circuit may include a first output terminal and a second output terminal. Specifically, the source of the first field-effect transistor is connected to the source of the second field-effect transistor, the drain of the first field-effect transistor is connected to the first terminal of the discharge switch assembly, the drain of the second field-effect transistor is connected to the second terminal of the discharge switch assembly, the gate of the first field-effect transistor is connected to the first output terminal, and the gate of the second field-effect transistor is connected to the second output terminal.

[0036] In one specific embodiment, both the first field-effect transistor and the second field-effect transistor can be N-type field-effect transistors.

[0037] In one specific embodiment, the first field-effect transistor may include a first diode; the second field-effect transistor may include a second diode. Specifically, the anodes of the first diode and the second diode are connected together. The cathode of the first diode is connected to the drain of the first field-effect transistor. The cathode of the second diode is connected to the drain of the second field-effect transistor.

[0038] In a specific embodiment, such as Figure 2 As shown, the second control switch may include a third field-effect transistor Q3 and a fourth field-effect transistor Q4, and the output terminals of the second drive circuit may include a third output terminal and a fourth output terminal. The source of the third field-effect transistor is connected to the source of the fourth field-effect transistor, the drain of the third field-effect transistor is connected to the first terminal of the discharge switch assembly, the drain of the fourth field-effect transistor is connected to the third terminal of the discharge switch assembly, the gate of the third field-effect transistor is connected to the third output terminal, and the gate of the fourth field-effect transistor is connected to the fourth output terminal.

[0039] In one specific embodiment, the third field-effect transistor may include a third diode; the fourth field-effect transistor may include a fourth diode. Specifically, the anodes of the third diode and the fourth diode are connected together. The cathode of the third diode is connected to the drain of the third field-effect transistor. The cathode of the fourth diode is connected to the drain of the fourth field-effect transistor.

[0040] In a specific embodiment, such as Figure 2As shown, the third control switch may include a fifth field-effect transistor Q5 and a sixth field-effect transistor Q6, and the output terminals of the third drive circuit may include a fifth output terminal and a sixth output terminal. The source of the fifth field-effect transistor is connected to the source of the sixth field-effect transistor, the drain of the fifth field-effect transistor is connected to the second terminal of the discharge switch assembly, the drain of the sixth field-effect transistor is connected to the fourth terminal of the discharge switch assembly, the gate of the fifth field-effect transistor is connected to the fifth output terminal, and the gate of the sixth field-effect transistor is connected to the sixth output terminal.

[0041] In one specific embodiment, the fifth field-effect transistor may include a fifth diode; the fourth field-effect transistor may include a sixth diode. Specifically, the anodes of the fifth and sixth diodes are connected together. The cathodes of the fifth diode and the drain of the fifth field-effect transistor are connected together. The cathodes of the sixth diode and the drain of the sixth field-effect transistor are connected together.

[0042] In one specific embodiment, for each field-effect transistor in the control switch of the discharge switch assembly, the corresponding field-effect transistor can be turned on according to the voltage polarity of the corresponding capacitor, and together with the body diode in another field-effect transistor, they form a discharge circuit to achieve the discharge of the capacitor.

[0043] For example, taking a first control switch that includes a first field-effect transistor and a second field-effect transistor as an example, the principle of the discharge process of the first capacitor XC1 is as follows: 1) Assuming the voltage polarity of the first capacitor is positive, the first terminal of the first capacitor (i.e., the terminal connected to the first power input terminal) is positive, and the second terminal of the first capacitor (i.e., the terminal connected to the second power input terminal) is negative, the first field-effect transistor can be turned on by the first driving circuit, and the second field-effect transistor can be turned off. At this time, the discharge circuit for the first capacitor can be "first capacitor XC1—first discharge resistor RD1—first field-effect transistor Q1—second diode D2—second discharge resistor RD2—first capacitor XC1".

[0044] 2) Assuming the voltage polarity of the first capacitor is as follows, the first terminal of the first capacitor (i.e., the terminal connected to the first power input terminal) is the negative terminal, and the second terminal of the first capacitor (i.e., the terminal connected to the second power input terminal) is the positive terminal, the first field-effect transistor can be turned off by the first driving circuit, and the second field-effect transistor can be turned on by the second driving circuit. At this time, the discharge circuit for the first capacitor can be "first capacitor XC1—second discharge resistor RD2—second field-effect transistor Q2—first diode D1—first discharge resistor RD1—first capacitor XC1".

[0045] For example, taking a second control switch that includes a third field-effect transistor and a fourth field-effect transistor as an example, the principle of the discharge process of the second capacitor XC2 is as follows: 1) Assuming the voltage polarity of the second capacitor is positive, the first terminal of the second capacitor (i.e., the terminal connected to the output terminal of the common-mode inductor) is positive, and the second terminal of the first capacitor (i.e., the terminal connected to the third capacitor) is negative, the third field-effect transistor can be closed by the second driving circuit, and the fourth field-effect transistor can be opened. At this time, the discharge circuit for the second capacitor can be "second capacitor XC2—common-mode inductor L—first discharge resistor RD1—third field-effect transistor Q3—fourth diode D4—third discharge resistor RD3—ground terminal GND—second capacitor XC2".

[0046] 2) Assuming the voltage polarity of the second capacitor is as follows, the first terminal of the second capacitor (i.e., the terminal connected to the output terminal of the common-mode inductor) is negative, and the second terminal of the first capacitor (i.e., the terminal connected to the third capacitor) is positive, the third field-effect transistor can be turned off by the second driving circuit, and the fourth field-effect transistor can be turned on. At this time, the discharge circuit for the second capacitor can be "second capacitor XC2—ground terminal GND—third discharge resistor RD3—fourth field-effect transistor Q4—third diode D3—first discharge resistor RD1—common-mode inductor L—second capacitor XC2".

[0047] The discharge circuit for the third capacitor can be referenced from the discharge circuit for the second capacitor described above, and will not be repeated here.

[0048] In one specific embodiment, the capacitor discharge module may further include a power-off detection module, the output of which is connected to the controller. The power-off detection module can be used to detect whether the power supply to the input of the filter circuit is disconnected.

[0049] In one specific embodiment, the power failure detection module may include a current detection unit and a power failure detection unit. Specifically, the two input terminals of the current detection unit are located between the first power input terminal and the first capacitor, the output terminal of the current detection unit is connected to the input terminal of the power failure detection unit, and the output terminal of the power failure detection unit is connected to the controller. The current detection unit can be used to detect whether the current at the input terminal of the filter circuit is zero. When the current output by the current detection unit is zero, the power failure detection unit can generate a power failure signal and send the power failure signal to the controller. Accordingly, upon receiving the power failure signal, the controller can control the switch in the discharge switch assembly to close, so that the first capacitor, the second capacitor, and the third capacitor in the filter circuit can discharge through the discharge resistor assembly.

[0050] In one specific embodiment Figure 3This is a circuit diagram illustrating a packaged capacitor discharge module according to an exemplary embodiment. Specifically, as shown... Figure 3 As shown, the discharge switch assembly can be packaged using an integrated chip structure. Specifically, using integrated chip packaging can solve the technical problem of miniaturization. Fewer external components are required; the actual circuit uses four external discharge resistors (i.e., the first discharge resistor, the second discharge resistor, the third discharge resistor, and the fourth discharge resistor). The circuit is simple, safe, and reliable, and it facilitates the structural layout of the filter circuit and the printed circuit board layout.

[0051] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the utility models disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0052] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A filter circuit, characterized in that, The filter circuit includes a capacitor discharge module, a common-mode inductor, a first capacitor, a second capacitor, and a third capacitor; the capacitor discharge module includes a discharge resistor assembly and a discharge switch assembly, and the discharge resistor assembly includes a first discharge resistor, a second discharge resistor, a third discharge resistor, and a fourth discharge resistor; The two ends of the first capacitor are respectively connected to the two power input terminals, the two ends of the first capacitor are respectively connected to the two input terminals of the common mode inductor, the two output terminals of the common mode inductor are respectively connected to the first terminal of the second capacitor and the first terminal of the third capacitor, the second terminal of the second capacitor is connected to the second terminal of the third capacitor, and the second terminal of the second capacitor is connected to the ground terminal. The two ends of the first discharge resistor are respectively connected to the first power input terminal of the two power input terminals and the first terminal of the discharge switch assembly. The two ends of the second discharge resistor are respectively connected to the second power input terminal of the two power input terminals and the second terminal of the discharge switch assembly. The two ends of the third discharge resistor are respectively connected to the third terminal of the discharge switch assembly and the ground terminal. The two ends of the fourth discharge resistor are respectively connected to the fourth terminal of the discharge switch assembly and the ground terminal.

2. The filter circuit according to claim 1, characterized in that, The discharge switch assembly includes a first control switch, a second control switch, and a third control switch; one end of the first control switch is connected to a first end of the discharge switch assembly, and the other end of the first control switch is connected to a second end of the discharge switch assembly; one end of the second control switch is connected to the first end of the discharge switch assembly, and the other end of the second control switch is connected to a third end of the discharge switch assembly; one end of the third control switch is connected to the second end of the discharge switch assembly, and the other end of the third control switch is connected to a fourth end of the discharge switch assembly.

3. The filter circuit according to claim 2, characterized in that, The capacitor discharge module further includes a controller and a switch drive module. The controller is connected to the switch drive module. The switch drive module includes a first drive circuit, a second drive circuit, and a third drive circuit. The output terminal of the first drive circuit is connected to the control signal input terminal of the first control switch. The output terminal of the second drive circuit is connected to the control signal input terminal of the second control switch. The output terminal of the third drive circuit is connected to the control signal input terminal of the third control switch.

4. The filter circuit according to claim 3, characterized in that, The first control switch includes a first field-effect transistor and a second field-effect transistor. The output terminal of the first driving circuit includes a first output terminal and a second output terminal. The source of the first field-effect transistor is connected to the source of the second field-effect transistor. The drain of the first field-effect transistor is connected to the first terminal of the discharge switch assembly. The drain of the second field-effect transistor is connected to the second terminal of the discharge switch assembly. The gate of the first field-effect transistor is connected to the first output terminal. The gate of the second field-effect transistor is connected to the second output terminal.

5. The filter circuit according to claim 3, characterized in that, The second control switch includes a third field-effect transistor and a fourth field-effect transistor. The output terminals of the second driving circuit include a third output terminal and a fourth output terminal. The source of the third field-effect transistor is connected to the source of the fourth field-effect transistor. The drain of the third field-effect transistor is connected to the first terminal of the discharge switch assembly. The drain of the fourth field-effect transistor is connected to the third terminal of the discharge switch assembly. The gate of the third field-effect transistor is connected to the third output terminal. The gate of the fourth field-effect transistor is connected to the fourth output terminal.

6. The filtering circuit according to claim 3, characterized in that, The third control switch includes a fifth field-effect transistor and a sixth field-effect transistor. The output terminals of the third driving circuit include a fifth output terminal and a sixth output terminal. The source of the fifth field-effect transistor is connected to the source of the sixth field-effect transistor. The drain of the fifth field-effect transistor is connected to the second terminal of the discharge switch assembly. The drain of the sixth field-effect transistor is connected to the fourth terminal of the discharge switch assembly. The gate of the fifth field-effect transistor is connected to the fifth output terminal. The gate of the sixth field-effect transistor is connected to the sixth output terminal.

7. The filter circuit according to claim 3, characterized in that, The capacitor discharge module also includes a power failure detection module, the output of which is connected to the controller.

8. The filter circuit according to claim 7, characterized in that, The power failure detection module includes a current detection unit and a power failure detection unit. The two input terminals of the current detection unit are located between the first power input terminal and the first capacitor. The output terminal of the current detection unit is connected to the input terminal of the power failure detection unit, and the output terminal of the power failure detection unit is connected to the controller.

9. The filter circuit according to any one of claims 1-8, characterized in that, The discharge switch assembly is packaged using an integrated chip structure.

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