Emi filter, circuit, and electrical appliance

Abstract

The utility model discloses a kind of EMI filter, circuit and electrical equipment applied to three-phase pulse width modulation inverter, belong to power electronics field.EMI filter includes inverter;The output side of the inverter is provided with common mode inductor;The common mode inductor is connected in series with the input side of the inverter.Due to common mode inductor and the output side and input side of the inverter are connected, i. e. inverter input side common mode inductor and output side common mode inductor are integrated into a magnetic component, equivalent to the input and output of inverter are magnetically coupled, so on the basis of not increasing inductor, input and output side common mode current can be further suppressed as well.In the case where cost and filter volume are not increased, the filtering effect of filter is improved.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to an EMI filter, circuit, and electrical equipment applied to a three-phase pulse width modulation inverter. Background Technology

[0002] A three-phase pulse width modulation (PWM) inverter is a power electronic device that regulates output voltage and frequency by controlling the pulse width. It is widely used in motor speed control, new energy power generation, and other fields. Its core principle is to generate an equivalent sine wave output by changing the on and off times of switching devices. Three-phase PWM inverters are highly efficient and have low harmonics, making them particularly suitable for small to medium capacity variable frequency speed control systems. With the development of switching devices and microelectronics technology, their output waveform is becoming increasingly closer to an ideal sine wave. However, the sum of the phase voltages in a three-phase pulse width modulation (PWM) inverter is not equal to zero. Therefore, in actual use, a three-phase PWM inverter will generate common-mode (CM) voltage, leading to various electromagnetic interferences (EMI) in the motor drive system.

[0003] For example, reduced motor bearing life due to motor shaft voltage, conducted EMI due to CM current propagating through parasitic capacitance, and radiated EMI due to radiated emissions from power cables are known.

[0004] To prevent the aforementioned EMI in motor drive systems, CM current propagating through the input and output sides of the inverter must be suppressed. However, installing EMI filters on the input and output sides of the inverter increases the number of filter components and the filter size. Utility Model Content

[0005] To overcome the shortcomings of existing technologies, this invention provides an EMI filter, circuit, and electrical equipment for a three-phase pulse width modulation inverter, addressing the issue that existing EMI filters, in order to prevent the aforementioned EMI in motor drive systems, must suppress the CM current propagating through the input and output sides of the inverter. However, installing EMI filters on the input and output sides of the inverter increases the number of filter components and the filter size.

[0006] The technical solution adopted by this utility model to solve its technical problem is: In one aspect, an EMI filter is provided, comprising: an inverter; A common-mode inductor is provided on the output side of the inverter; The common-mode inductor is connected in series with the input side of the inverter.

[0007] As an optional implementation of this application, the inverter is a three-phase pulse width modulation inverter; The inverter includes two input branches and three output branches; Each output branch has a common-mode inductor.

[0008] As an optional implementation of this application, it also includes: a differential mode inductor; A differential mode inductor is provided on each output branch of the inverter; One end of the common-mode inductor is connected to the inverter, and the other end is connected to the differential-mode inductor.

[0009] As an optional implementation of this application, it also includes: a differential mode capacitor; Each output branch of the inverter is connected to a differential mode capacitor; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

[0010] As an optional implementation of this application, one end of the differential mode capacitor is connected to the output side of the inverter in sequence through the differential mode inductor and the common mode inductor.

[0011] As an optional implementation of this application, it also includes: a common-mode capacitor; Each input branch of the inverter is connected to a common-mode capacitor; One end of the common-mode capacitor is connected to the input side of the inverter, and the other end is connected to the output side of the inverter.

[0012] As an optional implementation of this application, the other end of the common-mode capacitor is connected to the output side of the inverter in sequence through the differential-mode capacitor, the differential-mode inductor and the common-mode inductor.

[0013] As an optional implementation of this application, it also includes: a filter capacitor; One end of the filter capacitor is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

[0014] In a second aspect, a driving circuit is provided, comprising the EMI filter described in any of the preceding claims.

[0015] Thirdly, an electrical device is provided, comprising: a drive circuit as provided in the above technical solution.

[0016] The application employs the above technical solution and has at least the following beneficial effects: This application provides an EMI filter, circuit, and electrical equipment applied to a three-phase pulse width modulation inverter. The EMI filter includes an inverter; a common-mode inductor is disposed on the output side of the inverter; the common-mode inductor is connected in series with the input side of the inverter. Since the common-mode inductor is connected to both the output and input sides of the inverter, that is, the input-side common-mode inductor and the output-side common-mode inductor are integrated into a single magnetic component, it is equivalent to magnetic coupling between the input and output of the inverter. This further suppresses common-mode current on both the input and output sides without increasing the number of inductors. The filtering effect of the filter is improved without increasing cost or filter size. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the circuit structure of an existing EMI filter provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the circuit structure of an input / output coupling EMI filter provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the circuit structure of an input / output coupling EMI filter for a motor provided by an embodiment of the present invention; Figure 4 This is a schematic diagram of a conducted emission test result provided by an embodiment of this utility model.

[0019] Explanation of reference numerals in the attached figures: LISN - Linear Impedance Stabilized Network; C CM1 -First common-mode capacitor; C CM2 -Second common-mode capacitor; C - Filter capacitor; U-inverter; L CM1 - First common-mode inductor; L DM1 - First differential mode inductor; L CM2 -Second common-mode inductor; L DM2 -Second differential mode inductor; L CM3-Third common-mode inductor; L DM3 -Third differential mode inductor; C DM1 - First differential mode capacitor; C DM2 -Second differential mode capacitor; C DM3 -Third differential mode capacitor; IM-Motor; Ground plane - Ground wire. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this utility model will be described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Definitions: Three-phase pulse width modulation (PWM) is a technology widely used in power electronics and motor control. It generates a series of pulses with equal amplitude to equivalently replace the desired output waveform (such as a sine wave) by controlling the on / off state of the switching devices in a three-phase inverter circuit. Its core principle is to change the output voltage and frequency by adjusting the pulse width (duty cycle), thereby achieving the purpose of voltage and frequency regulation.

[0022] Basic principles Three-phase PWM technology generates three pulse sequences with a 120° phase difference by controlling six switching devices in a three-phase inverter bridge. The width of these pulses is modulated according to a modulation signal (usually a sine wave), so that the average voltage of the output pulses is equivalent to the target waveform.34 For example, in motor control, the motor speed and torque can be precisely controlled by adjusting the duty cycle of the PWM.

[0023] Main features High efficiency: The power devices operate in a switching state, avoiding the losses of linear regulation and improving system efficiency.

[0024] Flexibility: The duty cycle can be easily adjusted via digital signals (such as microprocessors), facilitating integration into digital control systems.

[0025] Harmonic suppression: By optimizing modulation strategies (such as SPWM), low-order harmonics in the output waveform can be effectively reduced, thereby improving power quality.

[0026] The sum of the phase voltages in a three-phase pulse width modulation (PWM) inverter is typically not equal to zero. This is related to the balance of the three-phase voltages and the load characteristics. The specific reasons are as follows: In an ideal equilibrium state, the scalar sum of the three-phase phase voltages (such as a sine wave) is zero. However, in practical applications, switching functions, harmonic components, or load asymmetry can cause the vector sum of the phase voltages to be non-zero. For example, the neutral point voltage (neutral point drift) introduces an additional voltage component, causing the sum of the three-phase voltages to deviate from zero. Harmonic component influence PWM waveforms contain higher-order harmonics (such as the 5th and 7th harmonics). These harmonics may cause a non-zero vector sum in the three phases due to phase or amplitude differences. Load characteristics If the load is unbalanced (such as a single-phase load or an unbalanced load), the three-phase current imbalance will introduce additional voltage through the neutral line, further affecting the sum of the phase voltages. Neutral point drift In a three-phase inverter, the neutral point voltage (neutral point drift) is determined by the state of the three-phase switches, and its expression is: If the switching states are unbalanced, the neutral point voltage will deviate from zero, resulting in the phase voltage vector sum being non-zero.

[0027] Performance in practical applications In motor control or power electronic systems, a non-zero sum of three-phase voltages may manifest as neutral point voltage offset or harmonic distortion, which requires optimization through control algorithms to reduce the impact.

[0028] Electromagnetic interference (EMI) is electronic noise that interferes with cable signals and reduces signal integrity. EMI is usually generated by sources of electromagnetic radiation such as motors and machines.

[0029] Electromagnetic interference (EMI) filters are electronic devices that reduce internal and external electromagnetic interference by suppressing conducted interference and improving electromagnetic compatibility. Their working principle primarily relies on differential-mode interference suppression and common-mode interference suppression. The former utilizes X-capacitors and differential-mode inductors to filter out high-frequency noise, while the latter attenuates noise paths through common-mode inductors and Y-capacitors. These devices are widely used in power supplies, communications, and medical equipment, and their main types include power filters and signal filters. During the design phase, factors such as operating frequency, impedance matching, and safety standards must be considered, and proper installation is crucial to ensure effective filtering.

[0030] Common-mode capacitors are electronic components that suppress common-mode interference by bypassing high-frequency noise. They are widely used to improve the electromagnetic compatibility (EMC) performance of circuits. Their core function is to guide common-mode noise signals away from sensitive circuits through a low-impedance path. They are commonly found in power supply port filtering, operational amplifier circuit stability, and IGBT module design. Common-mode capacitors employ a three-terminal design combined with a ground terminal to effectively reduce equivalent series inductance (ESL) and electrode edge radiation, playing a crucial role in EMC filtering and transimpedance amplifiers.

[0031] Common-mode inductor: A common-mode inductor, also known as a common-mode choke or common-mode filter, is made by placing two inductors with opposite winding directions together to suppress common-mode signals.

[0032] Differential-mode capacitors (X capacitors) are electronic components used to suppress differential-mode interference. They protect circuits from interference by providing a low-impedance path for high-frequency noise, short-circuiting it back to the source. Differential-mode inductor: A differential-mode inductor is an inductor with high inductive reactance to differential-mode high-frequency interference, also known as a differential-mode choke coil.

[0033] Existing EMI filter structure as follows Figure 1 As shown, the transformer is a three-phase pulse width modulation transformer, which includes two input branches and three output branches, with a filter capacitor connected between the two input branches. The input branches are connected to DC power, and in some embodiments, each input branch is connected to a linear impedance stabilizing network. The output branches are connected to a three-phase load, such as a motor.

[0034] The two input branches are connected to the transformer's output branches via a first common-mode capacitor and a second common-mode capacitor, respectively. Specifically, they are connected to the transformer's three output branches via a first differential-mode capacitor, a second differential-mode capacitor, and a third differential-mode capacitor, respectively. Each of the three output branches is equipped with a set of differential-mode inductors and common-mode inductors connected in series, namely, a first differential-mode inductor, a first common-mode inductor, a second differential-mode inductor, a second common-mode inductor, a third differential-mode inductor, and a third common-mode inductor.

[0035] Figure 1 The EMI filter shown has a differential-mode inductor and a differential-mode capacitor connected to the output side of inverter U, forming a sinusoidal filter. The neutral point of the differential-mode capacitor is connected to the input side of inverter U through a common-mode capacitor, and the other end is connected to the output side of inverter U, forming a common-mode filter. However, this method cannot effectively suppress the common-mode current on the input side of inverter U. Adding a common-mode inductor directly to the input side of inverter U would not only significantly increase the cost of the EMI filter but also increase its overall size.

[0036] Example 1: Therefore, in order to solve the above problems, refer to Figure 2 This utility model embodiment provides an EMI filter, including: an inverter U; A common-mode inductor is provided on the output side of the inverter U; The common-mode inductor is connected in series with the input side of the inverter U.

[0037] In a preferred implementation of this application, the inverter U is a three-phase pulse width modulation inverter U; The inverter U includes two input branches and three output branches; each input branch can be connected to a DC power supply through a linear impedance stabilization network. The output branches are phases UVW, connected to a three-phase load.

[0038] Each output branch has a common-mode inductor, such as Figure 2 As shown, these are the first common-mode inductor L. CM1 Second common mode inductor L CM2 and the third common mode inductor L CM3 This common-mode inductor is used to suppress common-mode signals on each output branch. Since the common-mode inductor is connected in series with the input side of inverter U, the common-mode inductor on the output side can also suppress common-mode signals on the input branch. Compared with traditional filters, only two more sets of wiring are required, eliminating the need for additional common-mode inductors. It suppresses common-mode signals on the input side of inverter U without increasing costs. Furthermore, the common-mode inductor connects to both the output and input sides of inverter U, effectively creating magnetic coupling between inverter U and the inductors on both the output and input sides. Compared to directly adding a common-mode inductor to the input side of inverter U, magnetic coupling attenuates conducted emissions over a wide frequency range, further improving the performance of inverter U.

[0039] Furthermore, it also includes: differential mode inductors; A differential-mode inductor is provided on each output branch of the inverter U; for example... Figure 2 As shown, these are the first differential mode inductor L. DM1 Second differential mode inductor L DM2 and the third differential mode inductor L DM3 This is used to eliminate the differential mode signal of the inverter U.

[0040] One end of the common-mode inductor is connected to the inverter U, and the other end is connected to the differential-mode inductor.

[0041] Preferably, one end of the differential mode capacitor is connected to the output side of the inverter U in sequence through the differential mode inductor and the common mode inductor.

[0042] Also includes: differential mode capacitors; Each output branch of the inverter is connected to a differential-mode capacitor, namely the first differential-mode capacitor C. DM1 Second differential mode capacitor C DM2 and the third differential mode capacitor C DM3 ; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

[0043] Furthermore, it also includes: common-mode capacitors; Each input branch of the inverter U is connected to a common-mode capacitor; namely, the first common-mode capacitor C. CM1 Second common-mode capacitor C CM2 ; One end of the common-mode capacitor is connected to the input side of the inverter U, and the other end is connected to the output side of the inverter U.

[0044] Specifically, the other end of the common-mode capacitor is connected to the output side of the inverter U in sequence through the differential-mode capacitor, the differential-mode inductor, and the common-mode inductor.

[0045] As a preferred implementation of this application embodiment, it further includes: a filter capacitor C; One end of the filter capacitor C is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

[0046] The EMI filter provided in this embodiment includes an inverter U; a common-mode inductor is disposed on the output side of the inverter U; the common-mode inductor is connected in series with the input side of the inverter U. Since the common-mode inductor is connected to both the output and input sides of the inverter U, that is, the input-side common-mode inductor and the output-side common-mode inductor of the inverter U are integrated into a single magnetic component, it is equivalent to magnetic coupling between the input and output of the inverter U. This further suppresses common-mode current on both the input and output sides without increasing the number of inductors. The filtering effect of the filter is improved without increasing cost or filter size.

[0047] Furthermore, magnetically coupling the input common-mode inductor and the output common-mode inductor together offers the following advantages: 1. Enhanced common-mode noise suppression effect Magnetic coupling design can more effectively suppress common-mode noise. When the cores of two common-mode inductors are coupled, their magnetic fields superimpose, presenting a higher impedance to common-mode interference signals, thus blocking noise propagation more efficiently. This design is particularly suitable for high-frequency noise environments, significantly reducing electromagnetic interference (EMI). 2. Improve signal transmission quality Through magnetic coupling, common-mode inductors can more accurately distinguish between common-mode and differential-mode signals. Common-mode signals are suppressed, while differential-mode signals (such as normal data transmission) pass through with almost no attenuation, thereby improving signal integrity and transmission reliability. This is especially important in high-speed communications or precision electronic equipment.

[0048] 3. Optimize electromagnetic compatibility (EMC) Magnetic coupling design helps meet stringent EMC standards. It simultaneously suppresses common-mode noise on both the power input and output sides, preventing high-frequency noise generated by internal switching devices from feeding back into the power grid or interfering with other equipment. This is crucial for scenarios with high EMC requirements.

[0049] 4. Simplify circuit design Coupled designs can reduce the number of discrete components, shrink layout space, and mitigate the effects of parasitic parameters. For example, core sharing or winding coupling can reduce parasitic capacitance and improve high-frequency performance.

[0050] 5. Improve system security Through more thorough noise suppression, magnetically coupled common-mode inductors can reduce the risk of equipment failure caused by electromagnetic interference, such as bit errors and signal distortion, thereby improving the overall system stability and security. Example 2: like Figure 3 As shown below, an EMI filter for motor IM is provided, including: inverter U; A common-mode inductor is provided on the output side of the inverter U; The common-mode inductor is connected in series with the input side of the inverter U.

[0051] In a preferred implementation of this application, the inverter U is a three-phase pulse width modulation inverter U; The inverter U includes two input branches and three output branches; each input branch can be connected to a DC power supply via a linear impedance stabilization network (LISN). The output branches are phases UVW, connected to the motor IM. The LISN, inverter U, and motor IM are all connected to the ground plane.

[0052] Each output branch has a common-mode inductor, such as Figure 3 As shown, these are the first common-mode inductor L. CM1 Second common mode inductor L CM2 and the third common mode inductor L CM3This common-mode inductor is used to suppress common-mode signals on each output branch. Since the common-mode inductor is connected in series with the input side of inverter U, the common-mode inductor on the output side can also suppress common-mode signals on the input branch. Compared with traditional filters, only two more sets of wiring are required, eliminating the need for additional common-mode inductors. It suppresses common-mode signals on the input side of inverter U without increasing costs. Furthermore, the common-mode inductor connects to both the output and input sides of inverter U, effectively creating magnetic coupling between inverter U and the inductors on both the output and input sides. Compared to directly adding a common-mode inductor to the input side of inverter U, magnetic coupling attenuates conducted emissions over a wide frequency range, further improving the performance of inverter U.

[0053] Furthermore, it also includes: differential mode inductors; A differential-mode inductor is provided on each output branch of the inverter U; for example... Figure 3 As shown, these are the first differential mode inductor L. DM1 Second differential mode inductor L DM2 and the third differential mode inductor L DM3 This is used to eliminate the differential mode signal of the inverter U.

[0054] One end of the common-mode inductor is connected to the inverter U, and the other end is connected to the differential-mode inductor.

[0055] Preferably, one end of the differential mode capacitor is connected to the output side of the inverter U in sequence through the differential mode inductor and the common mode inductor.

[0056] Also includes: differential mode capacitors; Each output branch of the inverter is connected to a differential-mode capacitor, namely the first differential-mode capacitor C. DM1 Second differential mode capacitor C DM2 and the third differential mode capacitor C DM3 ; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

[0057] Furthermore, it also includes: common-mode capacitors; Each input branch of the inverter U is connected to a common-mode capacitor; namely, the first common-mode capacitor C. CM1 Second common-mode capacitor C CM2 ; One end of the common-mode capacitor is connected to the input side of the inverter U, and the other end is connected to the output side of the inverter U.

[0058] Specifically, the other end of the common-mode capacitor is connected to the output side of the inverter U in sequence through the differential-mode capacitor, the differential-mode inductor, and the common-mode inductor.

[0059] As a preferred implementation of this application embodiment, it further includes: a filter capacitor C; One end of the filter capacitor C is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

[0060] To further illustrate the effects of the embodiments of this application, tests are provided.

[0061] The test was conducted under three conditions: 1. Inverter U is not connected to a filter; 2. Connecting to a traditional PEF (and) Figure 3 Compared to the circuit shown, the only difference is that a common-mode inductor is added to the output side of the inverter U. (Refer to...) Figure 1 ); 3. Connect the input / output coupling PEF (reference) Figure 3 (Circuit shown).

[0062] Background noise was measured when all experimental equipment was turned off. The test results are as follows: Figure 3 As shown, the input / output coupled PEF increases the attenuation of conducted emissions without increasing the number of filter components or the filter size compared to the traditional PEF.

[0063] This result is because the input / output coupling PEF can suppress common-mode currents on both the input and output sides. In particular, the coupling PEF attenuates conducted emissions at frequencies above approximately 18 MHz, even when conventional PEFs show almost no attenuation. However, as... Figure 3 As shown, when the PEF is connected, conducted emissions increase slightly at approximately 30 MHz. This result may be due to the resonance between the leakage inductance and distributed capacitance of the CMI, but this has not been investigated in detail in the embodiments of this application. It will not be elaborated further here.

[0064] This embodiment investigates the attenuation characteristics of conducted emissions in an input / output coupled PEF in a motor IM drive system. Measurement results show that, compared to a conventional PEF, the input / output coupled PEF increases the attenuation of conducted emissions over a wide frequency range.

[0065] The EMI filter provided in this embodiment includes an inverter U; a common-mode inductor is disposed on the output side of the inverter U; the common-mode inductor is connected in series with the input side of the inverter U. Since the common-mode inductor is connected to both the output and input sides of the inverter U, that is, the input-side common-mode inductor and the output-side common-mode inductor of the inverter U are integrated into a single magnetic component, it is equivalent to magnetic coupling between the input and output of the inverter U. This further suppresses common-mode current on both the input and output sides without increasing the number of inductors. The filtering effect of the filter is improved without increasing cost or filter size.

[0066] Furthermore, magnetically coupling the input common-mode inductor and the output common-mode inductor together offers the following advantages: 1. Enhanced common-mode noise suppression effect Magnetic coupling design can more effectively suppress common-mode noise. When the cores of two common-mode inductors are coupled, their magnetic fields superimpose, presenting a higher impedance to common-mode interference signals, thus blocking noise propagation more efficiently. This design is particularly suitable for high-frequency noise environments, significantly reducing electromagnetic interference (EMI). 2. Improve signal transmission quality Through magnetic coupling, common-mode inductors can more accurately distinguish between common-mode and differential-mode signals. Common-mode signals are suppressed, while differential-mode signals (such as normal data transmission) pass through with almost no attenuation, thereby improving signal integrity and transmission reliability. This is especially important in high-speed communications or precision electronic equipment.

[0067] 3. Optimize electromagnetic compatibility (EMC) Magnetic coupling design helps meet stringent EMC standards. It simultaneously suppresses common-mode noise on both the power input and output sides, preventing high-frequency noise generated by internal switching devices from feeding back into the power grid or interfering with other equipment. This is crucial for scenarios with high EMC requirements.

[0068] 4. Simplify circuit design Coupled designs can reduce the number of discrete components, shrink layout space, and mitigate the effects of parasitic parameters. For example, core sharing or winding coupling can reduce parasitic capacitance and improve high-frequency performance.

[0069] 5. Improve system security Through more thorough noise suppression, magnetically coupled common-mode inductors can reduce the risk of equipment failure caused by electromagnetic interference, such as bit errors and signal distortion, thereby improving the stability and safety of the overall system.

[0070] Example 3: Based on the same inventive concept, this application provides a drive circuit, including an EMI filter, wherein the EMI filter includes an inverter U; A common-mode inductor is provided on the output side of the inverter U; The common-mode inductor is connected in series with the input side of the inverter U.

[0071] In a preferred implementation of this application, the inverter U is a three-phase pulse width modulation inverter U; The inverter U includes two input branches and three output branches; each input branch can be connected to a DC power supply through a linear impedance stabilization network. The output branches are phases UVW, connected to a three-phase load.

[0072] Each output branch has a common-mode inductor, such as Figure 2 As shown, these are the first common-mode inductor L. CM1 Second common mode inductor L CM2 and the third common mode inductor L CM3 This common-mode inductor is used to suppress common-mode signals on each output branch. Since the common-mode inductor is connected in series with the input side of inverter U, the common-mode inductor on the output side can also suppress common-mode signals on the input branch. Compared with traditional filters, only two more sets of wiring are required, eliminating the need for additional common-mode inductors. It suppresses common-mode signals on the input side of inverter U without increasing costs. Furthermore, the common-mode inductor connects to both the output and input sides of inverter U, effectively creating magnetic coupling between inverter U and the inductors on both the output and input sides. Compared to directly adding a common-mode inductor to the input side of inverter U, magnetic coupling attenuates conducted emissions over a wide frequency range, further improving the performance of inverter U.

[0073] Furthermore, it also includes: differential mode inductors; A differential-mode inductor is provided on each output branch of the inverter U; for example... Figure 2 As shown, these are the first differential mode inductor L. DM1 Second differential mode inductor L DM2 and the third differential mode inductor L DM3 This is used to eliminate the differential mode signal of the inverter U.

[0074] One end of the common-mode inductor is connected to the inverter U, and the other end is connected to the differential-mode inductor.

[0075] Preferably, one end of the differential mode capacitor is connected to the output side of the inverter U in sequence through the differential mode inductor and the common mode inductor.

[0076] Also includes: differential mode capacitors; Each output branch of the inverter is connected to a differential-mode capacitor, namely the first differential-mode capacitor C. DM1 Second differential mode capacitor C DM2 and the third differential mode capacitor C DM3 ; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

[0077] Furthermore, it also includes: common-mode capacitors; Each input branch of the inverter U is connected to a common-mode capacitor; namely, the first common-mode capacitor C. CM1 Second common-mode capacitor C CM2 ; One end of the common-mode capacitor is connected to the input side of the inverter U, and the other end is connected to the output side of the inverter U.

[0078] Specifically, the other end of the common-mode capacitor is connected to the output side of the inverter U in sequence through the differential-mode capacitor, the differential-mode inductor, and the common-mode inductor.

[0079] As a preferred implementation of this application embodiment, it further includes: a filter capacitor C; One end of the filter capacitor C is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

[0080] The driving circuit provided in this application embodiment includes an EMI filter, which includes an inverter U. A common-mode inductor is disposed on the output side of the inverter U. The common-mode inductor is connected in series with the input side of the inverter U. Since the common-mode inductor is connected to both the output and input sides of the inverter U, that is, the input-side common-mode inductor and the output-side common-mode inductor of the inverter U are integrated into a single magnetic component, it is equivalent to magnetic coupling between the input and output of the inverter U. In this way, without increasing the number of inductors, the common-mode current on both the input and output sides can be further suppressed. The filtering effect of the filter is improved without increasing cost or filter size.

[0081] Furthermore, magnetically coupling the input common-mode inductor and the output common-mode inductor together offers the following advantages: 1. Enhanced common-mode noise suppression effect Magnetic coupling design can more effectively suppress common-mode noise. When the cores of two common-mode inductors are coupled, their magnetic fields superimpose, presenting a higher impedance to common-mode interference signals, thus blocking noise propagation more efficiently. This design is particularly suitable for high-frequency noise environments, significantly reducing electromagnetic interference (EMI). 2. Improve signal transmission quality Through magnetic coupling, common-mode inductors can more accurately distinguish between common-mode and differential-mode signals. Common-mode signals are suppressed, while differential-mode signals (such as normal data transmission) pass through with almost no attenuation, thereby improving signal integrity and transmission reliability. This is especially important in high-speed communications or precision electronic equipment.

[0082] 3. Optimize electromagnetic compatibility (EMC) Magnetic coupling design helps meet stringent EMC standards. It simultaneously suppresses common-mode noise on both the power input and output sides, preventing high-frequency noise generated by internal switching devices from feeding back into the power grid or interfering with other equipment. This is crucial for scenarios with high EMC requirements.

[0083] 4. Simplify circuit design Coupled designs can reduce the number of discrete components, shrink layout space, and mitigate the effects of parasitic parameters. For example, core sharing or winding coupling can reduce parasitic capacitance and improve high-frequency performance.

[0084] 5. Improve system security Through more thorough noise suppression, magnetically coupled common-mode inductors can reduce the risk of equipment failure caused by electromagnetic interference, such as bit errors and signal distortion, thereby improving the stability and safety of the overall system.

[0085] Example 4: Based on the same inventive concept, embodiments of this application also provide an electrical device, including a drive circuit, wherein the drive circuit includes an EMI filter. The EMI filter includes: an inverter U; A common-mode inductor is provided on the output side of the inverter U; The common-mode inductor is connected in series with the input side of the inverter U.

[0086] In a preferred implementation of this application, the inverter U is a three-phase pulse width modulation inverter U; The inverter U includes two input branches and three output branches; each input branch can be connected to a DC power supply through a linear impedance stabilization network. The output branches are phases UVW, connected to a three-phase load.

[0087] Each output branch has a common-mode inductor, such as Figure 2 As shown, these are the first common-mode inductor L. CM1 Second common mode inductor L CM2 and the third common mode inductor L CM3This common-mode inductor is used to suppress common-mode signals on each output branch. Since the common-mode inductor is connected in series with the input side of inverter U, the common-mode inductor on the output side can also suppress common-mode signals on the input branch. Compared with traditional filters, only two more sets of wiring are required, eliminating the need for additional common-mode inductors. It suppresses common-mode signals on the input side of inverter U without increasing costs. Furthermore, the common-mode inductor connects to both the output and input sides of inverter U, effectively creating magnetic coupling between inverter U and the inductors on both the output and input sides. Compared to directly adding a common-mode inductor to the input side of inverter U, magnetic coupling attenuates conducted emissions over a wide frequency range, further improving the performance of inverter U.

[0088] Furthermore, it also includes: differential mode inductors; A differential-mode inductor is provided on each output branch of the inverter U; for example... Figure 2 As shown, these are the first differential mode inductor L. DM1 Second differential mode inductor L DM2 and the third differential mode inductor L DM3 This is used to eliminate the differential mode signal of the inverter U.

[0089] One end of the common-mode inductor is connected to the inverter U, and the other end is connected to the differential-mode inductor.

[0090] Preferably, one end of the differential mode capacitor is connected to the output side of the inverter U in sequence through the differential mode inductor and the common mode inductor.

[0091] Also includes: differential mode capacitors; Each output branch of the inverter is connected to a differential-mode capacitor, namely the first differential-mode capacitor C. DM1 Second differential mode capacitor C DM2 and the third differential mode capacitor C DM3 ; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

[0092] Furthermore, it also includes: common-mode capacitors; Each input branch of the inverter U is connected to a common-mode capacitor; namely, the first common-mode capacitor C. CM1 Second common-mode capacitor C CM2 ; One end of the common-mode capacitor is connected to the input side of the inverter U, and the other end is connected to the output side of the inverter U.

[0093] Specifically, the other end of the common-mode capacitor is connected to the output side of the inverter U in sequence through the differential-mode capacitor, the differential-mode inductor, and the common-mode inductor.

[0094] As a preferred implementation of this application embodiment, it further includes: a filter capacitor C; One end of the filter capacitor C is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

[0095] The electrical device provided in this application includes a drive circuit, which includes an EMI filter. The EMI filter includes an inverter U. A common-mode inductor is disposed on the output side of the inverter U. The common-mode inductor is connected in series with the input side of the inverter U. Since the common-mode inductor is connected to both the output and input sides of the inverter U, that is, the input-side common-mode inductor and the output-side common-mode inductor of the inverter U are integrated into a single magnetic component, it is equivalent to magnetic coupling between the input and output of the inverter U. This further suppresses the common-mode current on both the input and output sides without increasing the number of inductors. The filtering effect of the filter is improved without increasing cost or filter size.

[0096] Furthermore, magnetically coupling the input common-mode inductor and the output common-mode inductor together offers the following advantages: 1. Enhanced common-mode noise suppression effect Magnetic coupling design can more effectively suppress common-mode noise. When the cores of two common-mode inductors are coupled, their magnetic fields superimpose, presenting a higher impedance to common-mode interference signals, thus blocking noise propagation more efficiently. This design is particularly suitable for high-frequency noise environments, significantly reducing electromagnetic interference (EMI). 2. Improve signal transmission quality Through magnetic coupling, common-mode inductors can more accurately distinguish between common-mode and differential-mode signals. Common-mode signals are suppressed, while differential-mode signals (such as normal data transmission) pass through with almost no attenuation, thereby improving signal integrity and transmission reliability. This is especially important in high-speed communications or precision electronic equipment.

[0097] 3. Optimize electromagnetic compatibility (EMC) Magnetic coupling design helps meet stringent EMC standards. It simultaneously suppresses common-mode noise on both the power input and output sides, preventing high-frequency noise generated by internal switching devices from feeding back into the power grid or interfering with other equipment. This is crucial for scenarios with high EMC requirements.

[0098] 4. Simplify circuit design Coupled designs can reduce the number of discrete components, shrink layout space, and mitigate the effects of parasitic parameters. For example, core sharing or winding coupling can reduce parasitic capacitance and improve high-frequency performance.

[0099] 5. Improve system security Through more thorough noise suppression, magnetically coupled common-mode inductors can reduce the risk of equipment failure caused by electromagnetic interference, such as bit errors and signal distortion, thereby improving the stability and safety of the overall system.

[0100] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0101] It should be noted that in the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means at least two.

[0102] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0103] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0104] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0105] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0106] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0107] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0108] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An EMI filter, characterized in that, include: Inverter; A common-mode inductor is provided on the output side of the inverter; The common-mode inductor is connected in series with the input side of the inverter.

2. The EMI filter according to claim 1, characterized in that: The inverter is a three-phase pulse width modulation inverter; The inverter includes two input branches and three output branches; Each output branch has a common-mode inductor.

3. The EMI filter according to claim 2, characterized in that, Also includes: Differential mode inductor; A differential mode inductor is provided on each output branch of the inverter; One end of the common-mode inductor is connected to the inverter, and the other end is connected to the differential-mode inductor.

4. The EMI filter according to claim 3, characterized in that, Also includes: Differential mode capacitor; Each output branch of the inverter is connected to a differential mode capacitor; One end of the differential capacitor is connected to the output side of the inverter, and the other end is connected to the input side of the inverter.

5. The EMI filter according to claim 4, characterized in that: One end of the differential-mode capacitor is connected to the output side of the inverter in sequence through the differential-mode inductor and the common-mode inductor.

6. The EMI filter according to claim 4, characterized in that, Also includes: Common-mode capacitor; Each input branch of the inverter is connected to a common-mode capacitor; One end of the common-mode capacitor is connected to the input side of the inverter, and the other end is connected to the output side of the inverter.

7. The EMI filter according to claim 6, characterized in that: The other end of the common-mode capacitor is connected to the output side of the inverter in sequence through the differential-mode capacitor, the differential-mode inductor, and the common-mode inductor.

8. The EMI filter according to claim 2, characterized in that, It also includes: filter capacitors; One end of the filter capacitor is connected to one input branch of the filter, and the other end is connected to the other input branch of the filter.

9. A circuit, characterized in that: Includes the EMI filter as described in any one of claims 1-8.

10. An electrical appliance, characterized in that, include: The circuit as described in claim 9.

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