EMI suppression circuit
By coordinating the design of low-frequency common-mode suppression module, differential-mode discharge module, high-frequency common-mode suppression module and common-mode grounding module, and combining three-phase ferrite core common-mode inductor and X/Y capacitor, the problem of large size and high cost of existing EMI suppression technology in high-power scenarios is solved, achieving efficient EMI suppression and structural simplification.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2026-03-31
Smart Images
Figure CN224068545U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power electronics technology, and in particular to an EMI suppression circuit. Background Technology
[0002] With the widespread application of power electronic converters, the high-frequency electromagnetic interference (EMI) generated by their switching devices during rapid switching seriously affects system reliability and safety. Existing EMI suppression technologies are mainly divided into three categories: passive, active, and integrated filters.
[0003] Passive filters rely on inductors and capacitors to suppress interference, but they are bulky and have limited high-frequency suppression capabilities in high-power scenarios.
[0004] Active filters: They cancel out interference by compensating for the signal, but they are costly and have insufficient high-frequency suppression.
[0005] Integrated filters: reduce size by using a shared magnetic core, but the design is complex and heat dissipation is a significant problem.
[0006] In existing technologies, passive filters often require additional differential-mode inductors to suppress both common-mode and differential-mode noise, leading to increased size and cost. How to simplify the structure and reduce cost without compromising suppression performance is a pressing issue in this field. Utility Model Content
[0007] To address the technical problems existing in the background art, this utility model proposes an EMI suppression circuit.
[0008] This utility model proposes an EMI suppression circuit, comprising:
[0009] The low-frequency common-mode suppression module is used to suppress power frequency harmonics and low-frequency conducted noise. It consists of a three-phase ferrite core common-mode inductor L1.
[0010] The differential mode discharge module is used to discharge differential mode noise and consists of X capacitor C1, X capacitor C2 and X capacitor C3.
[0011] The high-frequency common-mode suppression module is used to suppress high-frequency switching noise and diode reverse recovery ringing, and is composed of a three-phase common-mode inductor L2;
[0012] The common-mode grounding module is used to guide common-mode noise to be discharged through the ground wire. It consists of Y capacitors C4, C5, and C6. One end of each Y capacitor is connected to the three-phase line, and the other end is connected to the ground.
[0013] Preferably, the input terminal of the differential mode bleeder module is electrically connected to the output terminal of the low-frequency common-mode suppression module, the output terminal of the differential mode bleeder module is electrically connected to the input terminal of the high-frequency common-mode suppression module, and the X capacitors C1, C2, and C3 are connected in parallel between the three phase lines.
[0014] Preferably, it further includes: an input protection module for overcurrent protection, comprising three sets of fuses connected in series independently at the three-phase input terminals, located before the low-frequency common-mode suppression module.
[0015] Preferably, both the three-phase ferrite core common-mode inductor L1 and the three-phase common-mode inductor L2 adopt a symmetrical winding structure, with the same number of turns and wound on the same ferrite toroidal core.
[0016] Preferably, the inductance value of the three-phase common-mode inductor L2 is not greater than one-thousandth of the inductance value of the three-phase ferrite core common-mode inductor L1.
[0017] Preferably, the Y capacitors C4, C5, and C6 of the common-mode grounding module are grounded in a star connection manner to form a multi-path discharge channel for common-mode noise.
[0018] Preferably, the capacitance of the X capacitors C1, C2, and C3 is 2.2μF and the withstand voltage is ≥630V; the capacitance of the Y capacitors C4, C5, and C6 is 0.1μF.
[0019] In this invention, the proposed EMI suppression circuit uses a three-phase ferrite core common-mode inductor L1 to suppress low-frequency noise, a three-phase common-mode inductor L2 to handle high-frequency interference, a differential-mode discharge module to discharge differential-mode noise, and a common-mode grounding module to guide common-mode noise to ground. Through the coordinated design of the two-stage common-mode inductor, differential-mode discharge module, and common-mode grounding module, the differential-mode inductor is omitted, thus reducing circuit size and saving costs while maintaining common-mode noise suppression capability. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the circuit structure of an EMI suppression circuit proposed in this utility model;
[0021] Figure 2 This is a schematic diagram of the circuit operation structure of an EMI suppression circuit proposed in this utility model. Detailed Implementation
[0022] Reference Figure 1 and Figure 2 The present invention proposes an EMI suppression circuit, comprising:
[0023] The low-frequency common-mode suppression module is used to suppress power frequency harmonics and low-frequency conducted noise. It consists of a three-phase ferrite core common-mode inductor L1.
[0024] The differential mode discharge module is used to discharge differential mode noise and consists of X capacitors C1, C2, and C3.
[0025] In this embodiment, the input terminal of the differential mode bleeder module is electrically connected to the output terminal of the low-frequency common-mode suppression module, and the output terminal of the differential mode bleeder module is electrically connected to the input terminal of the high-frequency common-mode suppression module. X capacitors C1, C2, and C3 are connected in parallel between the three phase lines.
[0026] The high-frequency common-mode suppression module is used to suppress high-frequency switching noise and diode reverse recovery ringing, and is composed of a three-phase common-mode inductor L2.
[0027] In this embodiment, both the phase ferrite core common mode inductor L1 and the three-phase common mode inductor L2 adopt a symmetrical winding structure, with the same number of turns and wound on the same ferrite toroidal core.
[0028] In this embodiment, the inductance of the three-phase common-mode inductor L2 is no greater than one-thousandth of the inductance of the three-phase ferrite core common-mode inductor L1.
[0029] The common-mode grounding module is used to guide common-mode noise to be discharged through the ground wire. It consists of Y capacitors C4, C5, and C6. One end of each Y capacitor is connected to the three-phase line, and the other end is connected to the ground.
[0030] In this embodiment, the Y capacitors C4, C5, and C6 of the common-mode grounding module are grounded in a star connection manner, forming a multi-path discharge channel for common-mode noise.
[0031] In this embodiment, it also includes: an input protection module for overcurrent protection, comprising three sets of fuses connected in series independently at the three-phase input terminals, located before the low-frequency common-mode suppression module.
[0032] In this embodiment, the capacitance of X capacitors C1, C2, and C3 is 2.2μF, and the withstand voltage is ≥630V; the capacitance of Y capacitors C4, C5, and C6 is 0.1μF.
[0033] Specifically, such as Figure 1 and Figure 2As shown, a passive EMI filter circuit is added to the system input. Because the system's EMI is in the high-frequency range (>1MHz), high-frequency noise is more easily coupled to the ground line through parasitic capacitance. Therefore, common-mode noise dominates the EMI. The design of the entire EMI filter circuit is mainly to suppress common-mode noise. Here, a three-phase common-mode inductor is connected in series after the fuse in the main circuit at the system input. This inductor is close to the mains input and its main purpose is to filter the power frequency harmonics after rectification and the conducted noise of the switching frequency. This noise frequency is significantly lower than the noise frequency near the switching transistor, so the inductance value is relatively large. A three-phase ferrite core common-mode inductor L1 with an inductance value of 5mH can be selected. The common-mode inductor is a common-mode interference suppression device with a ferrite core. It consists of three sets of coils of the same size and number of turns symmetrically wound on the same ferrite toroidal core, forming a six-port device. It has a large inductance for common-mode signals and has a suppression effect, while it has a very small leakage inductance for differential-mode signals and has almost no effect. The specific working principle is as follows: when a common-mode interference signal flows through the inductor, the magnetic flux in the magnetic ring superimposes, resulting in a considerable inductance. This presents a high impedance state for the common-mode signal, thus suppressing it. However, when differential-mode current flows through the two coils, the magnetic flux in the magnetic ring cancels out, resulting in almost no inductance. Therefore, the differential-mode current can pass through without attenuation. An X capacitor is then connected between each pair of phase lines. Since the power supply is 10KW, a larger capacitance value is chosen; a 2.2uF X capacitor is used here. Its function is to provide low impedance when a differential-mode signal flows through the input, forming an efficient differential-mode noise discharge path and preventing the signal from flowing into subsequent stages and causing interference. Because the proportion of differential-mode signals in the entire system is relatively small, and to reduce circuit size and cost, the differential-mode inductor is omitted in the overall circuit design; only the X capacitor is used to meet the overall system requirements. Then, another common-mode inductor L2 is connected. This common-mode inductor is used to filter the high-frequency noise generated by the fast switching of the switching transistor and the ringing caused by the reverse recovery of the diode. Therefore, its inductance value is much smaller than that of the first common-mode inductor. A common-mode inductor with an inductance value of 2.67uH can be selected. A Y capacitor is connected to the phase line of the inductor output terminal to the ground to form a discharge path between the common-mode noise and the ground, blocking the propagation of the common-mode noise to the power grid or load, so as to achieve better suppression of common-mode noise.
[0034] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. An EMI suppression circuit, characterized by, The application relates to a three-phase input filter, which comprises the following modules: a low-frequency common-mode suppression module for suppressing power frequency harmonics and low-frequency conducted noise, which is composed of a three-phase ferrite core common-mode inductor L1; a differential-mode discharge module for discharging differential-mode noise, which is composed of X capacitors C1, C2 and C3; a high-frequency common-mode suppression module for suppressing high-frequency switching noise and diode reverse recovery ringing, which is composed of a three-phase common-mode inductor L2; a common-mode grounding module for guiding common-mode noise to discharge through a ground wire, which is composed of Y capacitors C4, C5 and C6, one end of each Y capacitor being connected to three-phase lines and the other end being grounded in common.
2. The EMI suppression circuit of claim 1, wherein, The input end of the differential-mode discharge module is electrically connected to the output end of the low-frequency common-mode suppression module, and the output end of the differential-mode discharge module is electrically connected to the input end of the high-frequency common-mode suppression module, and the X capacitors C1, C2 and C3 are connected in parallel between the three-phase lines.
3. The EMI suppression circuit of claim 1, wherein, The application further comprises: an input protection module for overcurrent protection, which comprises three groups of fuses connected in series independently at three-phase input ends and is located in the front stage of the low-frequency common-mode suppression module.
4. The EMI suppression circuit of claim 1, wherein, The three-phase ferrite core common-mode inductor L1 and the three-phase common-mode inductor L2 adopt a symmetrical winding structure, have the same number of turns and are wound on the same ferrite ring-shaped magnetic core.
5. The EMI suppression circuit of claim 1, wherein, The inductance of the three-phase common-mode inductor L2 is not greater than one thousandth of the inductance of the three-phase ferrite core common-mode inductor L1.
6. The EMI suppression circuit of claim 1, wherein, The Y capacitors C4, C5 and C6 of the common-mode grounding module are grounded through a star connection mode to form a multi-path discharge channel of common-mode noise.
7. The EMI suppression circuit of claim 1, wherein, The capacitance of the X capacitors C1, C2 and C3 is 2.2 mu F, and the withstand voltage is greater than or equal to 630 V; the capacitance of the Y capacitors C4, C5 and C6 is 0.1 mu F.