EMI filter with impulse current suppression function

Abstract

The utility model belongs to the technical field of filters, and particularly relates to an EMI filter with an impulse current suppression function, which comprises a lightning protection circuit, a reverse connection prevention circuit, an impulse current suppression circuit, a filter circuit and a connection relation thereof. The EMI filter with the functions of lightning protection, reverse connection prevention and impact current suppression, provided by the utility model, brings efficient lightning protection, reverse connection prevention and impact current suppression to equipment.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to an EMI filter with an impact current suppression function. Background Art

[0002] At present, the functions of precision instruments and equipment are increasing, and the integration is getting higher and higher. Therefore, the electromagnetic compatibility requirements for instrument and equipment systems are becoming more and more stringent. As one of the effective devices to solve electromagnetic compatibility, electromagnetic interference filters (EMI filters) are usually designed at the forefront of the circuit. While filtering and protecting, the differential mode capacitors inside the filter circuit and the rear-end load capacitors will generate impact currents when the equipment is powered on. The propagation of impact currents on the power line will cause certain interference to other functional modules in the line, and traditional EMI filters cannot effectively eliminate this interference. Utility Model Content

[0003] The utility model aims to solve the problem of excessive impact current generated when the traditional EMI filter itself and the rear end capacitive load are powered on under a rated voltage of 270VDC, and to this end, provides an EMI filter with an impact current suppression function.

[0004] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0005] An EMI filter with an impact current suppression function, comprising a lightning protection circuit, an anti-reverse connection circuit, an impact current suppression circuit and a filter circuit;

[0006] The output end of the lightning protection circuit is electrically connected to the input end of the anti-reverse connection circuit, the output end of the anti-reverse connection circuit is electrically connected to the input end of the surge current suppression circuit, and the output end of the surge current suppression circuit is electrically connected to the input end of the filter circuit;

[0007] The lightning protection circuit comprises a TVS tube 1 and a TVS tube 2, wherein one end of the TVS tube 1 is grounded, and the other end of the TVS tube 1 is connected to the positive electrode of the filter input voltage, one end of the TVS tube 2 is grounded, and the other end of the TVS tube 2 is connected to the negative electrode of the filter input voltage;

[0008] The inrush current suppression circuit includes a capacitor C1, a MOS tube Q2 and a current limiting resistor R5;

[0009] The positive output terminal of the anti-reverse connection circuit is electrically connected to the G pole of the MOS tube Q2 through the resistors R3 and R4, and the negative output terminal of the anti-reverse connection circuit is electrically connected to the S pole of the MOS tube Q2;

[0010] One end of the capacitor C1 is connected to the line between the resistors R3 and R4 through the diode D3, and the other end of the capacitor C1 is electrically connected to the S pole of the MOS tube Q2. A current limiting resistor R5 is connected between the S pole and the D pole of the MOS tube Q2.

[0011] The following is a technical solution further defined by the present utility model, wherein the anti-reverse connection circuit comprises a MOS tube Q1, a G pole of the MOS tube Q1 is connected to the positive pole of the filter input voltage through a resistor R1, and a D pole of the MOS tube Q1 is connected to the negative pole of the filter input voltage;

[0012] A resistor R2 and a voltage-stabilizing diode D1 are electrically connected between the S pole and the G pole of the MOS tube Q1 , wherein the resistor R2 and the voltage-stabilizing diode D1 are connected in parallel.

[0013] The following is a technical solution further defined by the present invention: a capacitor C1 is electrically connected between the S pole and the G pole of the MOS tube Q1, wherein the capacitor C1, the resistor R2 and the voltage-stabilizing diode D1 are connected in parallel.

[0014] The following is a technical solution further defined by the utility model, wherein the inrush current suppression circuit further includes a Zener diode D2, one end of the Zener diode D2 is electrically connected to one end of the capacitor C1, and the other end of the Zener diode D2 is electrically connected to a diode D3 at the other end of the capacitor C1.

[0015] The following is a technical solution further defined by the present utility model, wherein the filter circuit includes filter inductors LC1, LC2 and filter capacitors Cx1, Cy1, Cy2, wherein one end of the filter capacitor Cx1 is connected to the positive electrode of the filter input voltage, and the other end of the filter capacitor Cx1 is electrically connected to the D pole of the MOS tube Q2;

[0016] One end of the filter capacitor Cx1 is connected to the positive electrode of the filter output terminal through the filter inductor LC1, and the other end of the filter capacitor Cx1 is connected to the negative electrode of the filter output terminal through the filter inductor LC2;

[0017] Filter capacitors Cy1 and Cy2 are connected between the positive electrode and the negative electrode of the filter output end, wherein the filter capacitors Cy1 and Cy2 are connected in series, and the line between the filter capacitors Cy1 and Cy2 is grounded.

[0018] Compared with the prior art, the utility model has the following technical effects:

[0019] The utility model designs a lightning protection circuit in the EMI filter, and the lightning protection circuit and the EMI filter circuit are packaged in the same housing, so that the EMI filter has a lightning protection function, effectively discharges instantaneous surge current, and protects sensitive devices.

[0020] The utility model designs an anti-reverse connection circuit based on a MOS tube in an EMI filter. The anti-reverse connection circuit and the EMI filter circuit are packaged in the same housing, so that the EMI filter has an anti-reverse connection function to prevent the circuit from being damaged by reverse voltage when the positive and negative lines are connected in reverse.

[0021] The utility model designs an impact current suppression circuit based on a MOS tube in an EMI filter. The impact current suppression circuit and the EMI filter circuit are packaged in the same housing, so that the EMI filter has an impact current suppression function and suppresses the impact current when the power supply is started to a safe range.

[0022] The EMI filter provided by the utility model has the functions of lightning protection, reverse connection protection and impact current suppression, which brings efficient lightning protection, reverse connection protection and impact current suppression to the equipment.

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a circuit connection diagram of the utility model;

[0026] Figure 2 It is a main structural schematic diagram of the utility model;

[0027] Figure 3 It is a partial structural schematic diagram of the utility model.

[0028] Figure numerals: 1. Lightning protection circuit; 2. Anti-reverse connection circuit; 3. Inrush current suppression circuit; 4. Filter circuit; 5. Metal shell; 6. Input lead wire; 7. Lightning protection module; 8. MOS tube driving circuit board; 9. N-type MOS tube for anti-reverse connection; 10. N-type MOS tube for inrush current suppression; 11. EMI filter module; 12. Output lead wire. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the utility model. However, the utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.

[0030] like Figure 1-3 As shown, an EMI filter with a surge current suppression function is provided.

[0031] like Figure 2 and 3 As shown, the EMI filter includes a metal shell 5, in which a 270VDC lightning protection module 7, a MOS tube driving circuit board 8, and an N-type MOS tube 9 (i.e. Figure 1 MOS tube Q1), N-type MOS tube 10 for surge current suppression (i.e. Figure 1 MOS tube Q2), 270VDC EMI filter module 11. The 270VDC lightning protection module 7 is provided with an input terminal lead wire 6 leading to the outside of the metal shell 5. The rear end of the 270VDC lightning protection module 7 is connected to the MOS tube driving circuit board 8. The MOS tube driving circuit board 8 is provided with an N-type MOS tube 9 for reverse connection protection and an N-type MOS tube 10 for impulse current suppression. The rear end of the MOS tube driving circuit board 8 is connected to the 270VDC EMI filter module 11. The 270VDC EMI filter module 11 is provided with an output terminal lead wire 12 leading to the outside of the metal shell 5.

[0032] The 270VDC lightning protection module 7 is provided with a 270VDC lightning protection circuit 1 .

[0033] The MOS tube driving circuit board 8 is provided with a 270VDC reverse connection protection circuit 2 and a 270VDC surge current suppression circuit 3 .

[0034] The 270VDC reverse connection protection circuit 2 is provided with an N-type MOS tube 9 (i.e. Figure 1 MOS tube Q1).

[0035] The 270VDC surge current suppression circuit 3 is provided with a surge current suppression N-type MOS tube 10 (i.e. Figure 1 MOS tube Q2).

[0036] 270VDC EMI filter circuit 4 in the 270VDC EMI filter module 11.

[0037] Considering the heat dissipation problem of the MOS tube, in this embodiment, the tube shell of the MOS tube is attached to the bottom of the metal shell 5 of the filter packaging shell.

[0038] like Figure 1 As shown, the output end of the 270VDC lightning protection circuit 1 is electrically connected to the input end of the 270VDC anti-reverse connection circuit 2, the output end of the 270VDC anti-reverse connection circuit 2 is electrically connected to the input end of the 270VDC impulse current suppression circuit 3, and the output end of the 270VDC impulse current suppression circuit 3 is electrically connected to the input end of the 270VDC EMI filter circuit 4.

[0039] The lightning protection circuit 1 includes TVS tube 1 and TVS tube 2, wherein one end of TVS tube 1 is grounded, and the other end of TVS tube 1 is connected to the positive pole of the filter input voltage, one end of TVS tube 2 is grounded, and the other end of TVS tube 2 is connected to the negative pole of the filter input voltage.

[0040] The anti-reverse connection circuit 2 includes a MOS tube Q1, the G pole of the MOS tube Q1 is connected to the positive pole of the filter input voltage through a resistor R1, and the D pole of the MOS tube Q1 is connected to the negative pole of the filter input voltage; a resistor R2 and a voltage zener diode D1 are electrically connected between the S pole and the G pole of the MOS tube Q1, wherein the resistor R2 and the voltage zener diode D1 are connected in parallel. Further, a capacitor C1 is electrically connected between the S pole and the G pole of the MOS tube Q1, wherein the capacitor C1, the resistor R2 and the voltage zener diode D1 are connected in parallel.

[0041] The surge current suppression circuit 3 includes a capacitor C1, a MOS tube Q2, a current limiting resistor R5 and a voltage stabilizing diode D2. The positive output end of the anti-reverse connection circuit 2 is electrically connected to the G pole of the MOS tube Q2 through resistors R3 and R4, and the negative output end of the anti-reverse connection circuit 2 is electrically connected to the S pole of the MOS tube Q2; one end of the capacitor C1 is connected to the line between the resistors R3 and R4 through a diode D3, and the other end of the capacitor C1 is electrically connected to the S pole of the MOS tube Q2, and a current limiting resistor R5 is connected between the S pole and the D pole of the MOS tube Q2. One end of the voltage stabilizing diode D2 is electrically connected to one end of the capacitor C1, and the other end of the voltage stabilizing diode D2 is electrically connected to the diode D3 at the other end of the capacitor C1.

[0042] The filter circuit 4 includes filter inductors LC1, LC2 and filter capacitors Cx1, Cy1, and Cy2, wherein one end of the filter capacitor Cx1 is connected to the positive electrode of the filter input voltage, and the other end of the filter capacitor Cx1 is electrically connected to the D pole of the MOS tube Q2; one end of the filter capacitor Cx1 is connected to the positive electrode of the filter output end through the filter inductor LC1, and the other end of the filter capacitor Cx1 is connected to the negative electrode of the filter output end through the filter inductor LC2; filter capacitors Cy1 and Cy2 are connected between the positive and negative electrodes of the filter output end, wherein the filter capacitors Cy1 and Cy2 are connected in series, and the line between the filter capacitors Cy1 and Cy2 is grounded.

[0043] In summary, if Figure 1 As shown, a 270VDC lightning protection circuit 1 based on a TVS tube is designed at the front end of the circuit. When the circuit is working normally, the TVS tube is in a high impedance state, which is equivalent to an open circuit and has no effect on the normal operation of the circuit. When an overvoltage pulse in the circuit breaks down the TVS tube, it is in a low impedance state, which is equivalent to a short circuit, discharging the instantaneous surge current flowing to the protected circuit and clamping the voltage to a safe level. When the abnormal voltage disappears, the TVS tube returns to a high impedance state and the back-end circuit works normally.

[0044] A 270VDC reverse connection protection circuit 2 based on an N-type MOS tube is designed at the rear end of the 270VDC lightning protection circuit 1. When the positive and negative lines are not reversed, the voltage between the MOS tube GS is greater than the threshold voltage after voltage division, the MOS tube Q1 is turned on, and the circuit works normally; when the positive and negative lines are reversed, the voltage between the G pole and the S pole of the MOS tube Q1 is less than the threshold voltage, the MOS tube Q1 is not turned on, and the rear end circuit is protected from damage by reverse voltage.

[0045] A 270VDC inrush current suppression circuit 3 based on an N-type MOS tube is designed at the rear end of the 270VDC reverse connection protection circuit 2. When the power supply is powered on, the capacitor C1 starts to charge, and the voltage between the G pole and the S pole of the MOS tube Q2 is 0V, which is less than the threshold voltage. The MOS tube Q2 is not turned on, and all the current flows through the current limiting resistor R5, suppressing the inrush current to a safe range. When C1 is charged to a voltage greater than the GS threshold voltage of the MOS tube Q2, the MOS tube Q2 is turned on, short-circuiting the current limiting resistor R5, and the circuit starts to work normally.

[0046] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the utility model by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the utility model, or modify it into an equivalent embodiment of equivalent changes. Therefore, all equivalent changes made according to the shape, structure and principle of the utility model without departing from the content of the technical solution of the utility model should be included in the protection scope of the utility model.

Claims

1. An EMI filter with a surge current suppression function, characterized in that: Including lightning protection circuit, anti-reverse connection circuit, surge current suppression circuit and filter circuit; The output end of the lightning protection circuit is electrically connected to the input end of the anti-reverse connection circuit, the output end of the anti-reverse connection circuit is electrically connected to the input end of the surge current suppression circuit, and the output end of the surge current suppression circuit is electrically connected to the input end of the filter circuit; The lightning protection circuit comprises a TVS tube 1 and a TVS tube 2, wherein one end of the TVS tube 1 is grounded, and the other end of the TVS tube 1 is connected to the positive electrode of the filter input voltage, one end of the TVS tube 2 is grounded, and the other end of the TVS tube 2 is connected to the negative electrode of the filter input voltage; The inrush current suppression circuit includes a capacitor C1, a MOS tube Q2 and a current limiting resistor R5; The positive output terminal of the anti-reverse connection circuit is electrically connected to the G pole of the MOS tube Q2 through the resistors R3 and R4, and the negative output terminal of the anti-reverse connection circuit is electrically connected to the S pole of the MOS tube Q2; One end of the capacitor C1 is connected to the line between the resistors R3 and R4 through the diode D3, and the other end of the capacitor C1 is electrically connected to the S pole of the MOS tube Q2. A current limiting resistor R5 is connected between the S pole and the D pole of the MOS tube Q2.

2. The EMI filter with surge current suppression function as claimed in claim 1, characterized in that: The anti-reverse connection circuit includes a MOS tube Q1, the G pole of the MOS tube Q1 is connected to the positive pole of the filter input voltage through a resistor R1, and the D pole of the MOS tube Q1 is connected to the negative pole of the filter input voltage; A resistor R2 and a voltage-stabilizing diode D1 are electrically connected between the S pole and the G pole of the MOS tube Q1 , wherein the resistor R2 and the voltage-stabilizing diode D1 are connected in parallel.

3. The EMI filter with surge current suppression function as claimed in claim 2, characterized in that: The capacitor C1 is electrically connected between the S pole and the G pole of the MOS tube Q1 , wherein the capacitor C1 , the resistor R2 and the voltage stabilizing diode D1 are connected in parallel.

4. The EMI filter with surge current suppression function as claimed in claim 1, characterized in that: The inrush current suppression circuit further includes a voltage regulator diode D2 , one end of the voltage regulator diode D2 is electrically connected to one end of the capacitor C1 , and the other end of the voltage regulator diode D2 is electrically connected to a diode D3 at the other end of the capacitor C1 .

5. The EMI filter with surge current suppression function as claimed in claim 1, characterized in that: The filter circuit includes filter inductors LC1, LC2 and filter capacitors Cx1, Cy1, Cy2, wherein one end of the filter capacitor Cx1 is connected to the positive electrode of the filter input voltage, and the other end of the filter capacitor Cx1 is electrically connected to the D pole of the MOS tube Q2; One end of the filter capacitor Cx1 is connected to the positive electrode of the filter output terminal through the filter inductor LC1, and the other end of the filter capacitor Cx1 is connected to the negative electrode of the filter output terminal through the filter inductor LC2; Filter capacitors Cy1 and Cy2 are connected between the positive electrode and the negative electrode of the filter output end, wherein the filter capacitors Cy1 and Cy2 are connected in series, and the line between the filter capacitors Cy1 and Cy2 is grounded.

Images