A common mode current cancellation circuit that overcomes compensation capacitor tolerance

Abstract

The application discloses a common-mode current cancellation circuit overcoming compensation capacitor tolerance, and belongs to the technical field of power electronics, and comprises the following steps: a tolerance feedback branch acquires a common-mode voltage signal of phase lines and neutral lines of an input power supply relative to a protective ground; high-pass filtering, voltage following isolation, low-pass filtering and inverse amplification processing are performed on the common-mode voltage signal to obtain an equivalent controlled voltage source signal proportional to the common-mode voltage signal; a parallel branch superimposes the equivalent controlled voltage source signal and a basic compensation voltage in series to obtain a corrected total compensation voltage, and current matching conversion processing is performed based on the total compensation voltage to obtain an output cancellation current. The application connects a controlled voltage source in series in the common-mode current cancellation branch, actively adjusts the compensation voltage to overcome the influence of the compensation capacitor tolerance, enhances the common-mode current cancellation capability, and thus improves the insertion loss of the common-mode current cancellation method.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a common-mode current cancellation circuit that overcomes the tolerance of compensation capacitors. Background Technology

[0002] With the rapid development of power electronics technology towards higher frequencies and higher power densities, electromagnetic compatibility (EMC) issues in switching converters are becoming increasingly prominent. Common-mode noise, as a major component of electromagnetic interference (EMI), not only affects the stable operation of the switching converter itself but can also interfere with the normal operation of nearby electronic equipment through conduction, and even jeopardize the safety and reliability of the entire power system. Therefore, suppressing common-mode noise has become one of the research hotspots in the field of power electronics.

[0003] Among numerous common-mode noise suppression techniques, passive cancellation methods based on the compensation principle have received widespread attention and application due to their advantages such as simple structure, no need for additional active components, and no introduction of new independent electromagnetic interference sources. The parallel cancellation method, also known as the common-mode current cancellation method, works on the following principle: after analyzing the common-mode noise using an equivalent model, at the high-frequency potential transition nodes that affect the noise, a compensation branch equivalent to the original common-mode noise source is constructed by using the characteristics of the same-name terminals of the coupled inductor or by adding a compensation winding to the transformer and connecting it in series with a compensation capacitor. This generates a reverse compensation current, thereby canceling the common-mode noise. Compared with traditional common-mode choke filtering methods, passive cancellation methods show better noise suppression performance in the low-frequency range and contribute to the miniaturization of filter design.

[0004] However, the suppression effect of the common-mode current cancellation method is highly dependent on the parameter matching accuracy of the compensation network. Whether the value of the compensation capacitor accurately approximates the actual value of the equivalent parasitic capacitance in the equivalent model of the original noise source topology directly affects the common-mode noise suppression effect. When the actual value of the compensation capacitor deviates from the design value, the amplitude and phase of the compensation current will deviate from the ideal state, manifesting as an attenuation of insertion loss. Deviations in the compensation capacitor value will lead to noise signals exceeding the ideal state across the entire frequency band, and even a small tolerance can cause significant insertion loss attenuation, greatly reducing the noise suppression effect of the common-mode current cancellation method.

[0005] Current research lacks a systematic solution to the insertion loss attenuation problem caused by the tolerance of the compensation capacitor. In engineering practice, the trial-and-error method is still used to repeatedly correct the compensation parameters, which greatly delays the product development cycle. Summary of the Invention

[0006] The purpose of this application is to overcome the deficiencies of the prior art and provide a common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor, so as to offset the insertion loss attenuation caused by the tolerance of the compensation capacitor.

[0007] In a first aspect, this application provides a common-mode current cancellation circuit to overcome the tolerance of the compensation capacitor, comprising: The tolerance feedback branch acquires the common-mode voltage signal between the first and second output terminals of the input power supply relative to the protective ground, and performs high-pass filtering, voltage follower isolation, low-pass filtering and inverting amplification on the common-mode voltage signal to obtain the controlled voltage source signal. The parallel branch determines the total compensation voltage source signal based on the controlled voltage source signal, and performs current matching conversion processing based on the total compensation voltage source signal to obtain the output cancellation current.

[0008] Optionally, the tolerance feedback branch includes: The sampling module performs high-pass filtering, voltage-following isolation, and low-pass filtering on the common-mode voltage signals of the phase line and neutral line of the input power supply relative to the protective ground to obtain the sampled voltage signal. An amplification module performs inverting amplification on the sampled voltage signal and outputs an equivalent controlled voltage source signal that is proportional to the common-mode voltage signal.

[0009] Optionally, the sampling module includes: a first capacitor, a second capacitor, a first resistor, a first operational amplifier, a second resistor, and a third capacitor. The first terminal of the first capacitor is connected to the first terminal of the input power supply; the second terminal of the first capacitor is connected to the first terminal of the first resistor; and the second terminal of the first resistor is connected to protective ground. The first terminal of the second capacitor is connected to the second terminal of the input power supply; the second terminal of the second capacitor is connected to the second terminal of the first capacitor and the first terminal of the first resistor. The first input terminal of the first operational amplifier is connected to the second terminal of the second capacitor, the second terminal of the first capacitor, and the first terminal of the first resistor; the second input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier. The first terminal of the second resistor is connected to the output terminal of the first operational amplifier; the second terminal of the second resistor is connected to the first terminal of the third capacitor; and the second terminal of the third capacitor is connected to protective ground.

[0010] Optionally, the voltage across the third capacitor is the sampling voltage output by the sampling module. V sense2 The expression is: in, Z C_sense1 Let be the capacitive reactance of the first capacitor and the second capacitor. Z C_sense2 The capacitive reactance of the third capacitor. Rsense1 The first resistor, R sense2 For the second resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

[0011] Optionally, the first capacitor, the second capacitor, and the first resistor constitute a high-pass filter unit, and the second resistor and the third capacitor constitute a low-pass filter unit; the high-pass filter unit and the low-pass filter unit together constitute a band-pass filter.

[0012] Optionally, the amplification module includes: a third resistor, a second operational amplifier, and a fourth resistor. The first end of the third resistor is connected to the second end of the second resistor, and the second end of the third resistor is connected to the first input terminal of the second operational amplifier. The second input terminal of the second operational amplifier is connected to protective ground. The first end of the fourth resistor is connected to the second end of the third resistor and the first input terminal of the second operational amplifier, and the second end of the third resistor is connected to the output terminal of the second operational amplifier.

[0013] Optionally, the output voltage of the amplification module can be used as an equivalent controlled voltage source.

[0014] Optionally, the tolerance feedback branch, when connected in series with the parallel branch, is equivalent to a new compensation voltage source. The equivalent controlled voltage source of the tolerance feedback branch has the same reference direction as the original compensation voltage source of the parallel branch. By actively adjusting the compensation voltage source, the influence of the compensation capacitor tolerance is overcome, enhancing the common-mode current cancellation capability and thus improving the insertion loss of the common-mode current cancellation method.

[0015] Optionally, an equivalent controlled voltage source v G The expression is: in, This represents the actual closed-loop gain of the amplification module. Z C_sense1 Let be the capacitive reactance of the first capacitor and the second capacitor. Z C_sense2 The capacitive reactance of the third capacitor. R sense1 The first resistor, R sense2 For the second resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

[0016] Secondly, this application provides a power electronic conversion device, comprising: Input power, output electrical energy; The converter, with power semiconductor switching devices as its core, receives electrical energy output from the input power supply and performs power conversion. During the power conversion process, the high-frequency switching action of the power semiconductor switching devices generates common-mode noise signals through the parasitic capacitance to ground of the potential switching nodes. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor as described in any one of the first aspects receives the electrical energy output by the input power supply and the common-mode noise signal generated by the converter, performs phase inversion and amplitude matching processing to obtain a cancellation current, and injects the cancellation current into the converter to cancel the common-mode current generated therefrom.

[0017] This application provides a common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor. By connecting the tolerance feedback branch in series with the parallel branch, the equivalent controlled voltage source reduces the insertion loss attenuation caused by the tolerance of the compensation capacitor, greatly improves the cancellation effect of passive cancellation technology when the parameter accuracy is mismatched, and significantly reduces the dependence on high-precision compensation capacitors.

[0018] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying 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.

[0020] Figure 1 This is a schematic diagram of the structure of a power electronic conversion device provided in one embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor provided in the power electronic conversion device of this application.

[0022] Figure 3 This is a schematic diagram of the topology of the common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor provided in the power electronic conversion device of this application.

[0023] Figure 4 This is a simplified schematic diagram of the original cancellation circuit.

[0024] Figure 5 for Figure 2 A simplified schematic diagram of the common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor.

[0025] Figure 6This is a comparison of the simulated common-mode noise spectra with and without a tolerance feedback branch during passive noise reduction in a specific example.

[0026] Figure 7 This is a graph showing the insertion loss curves of the theoretical calculation and simulation spectrum transformation of a passive cancellation noise reduction circuit with tolerance feedback versus one without tolerance feedback, in a specific example. Detailed Implementation

[0027] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0028] In one specific embodiment, please refer to Figure 1 This application provides a power electronic conversion device, including: a common-mode current cancellation circuit 1 for overcoming the tolerance of the compensation capacitor; an input power supply 2 for outputting electrical energy; and a converter 3, which uses a power semiconductor switching device as its core, receives the electrical energy output from the input power supply 2 and performs power conversion. During the power conversion process, the high-frequency switching action of the power semiconductor switching device generates a common-mode noise signal through the parasitic capacitance to ground at the potential jump node. The common-mode current cancellation circuit 1 for overcoming the tolerance of the compensation capacitor receives the electrical energy output from the input power supply 2 and the common-mode noise signal generated by the converter 3, performs phase inversion and amplitude matching processing to obtain a cancellation current, and injects the cancellation current into the converter 3 to cancel the common-mode current it generates.

[0029] As an example, a power electronic conversion device of this application further includes: a detection device 4, used to detect the common-mode interference signal generated by the converter 3 in real time, and / or detect the residual common-mode interference signal after being canceled by the common-mode current cancellation circuit 1 that overcomes the tolerance of the compensation capacitor.

[0030] As an example, the detection device can be a linear stable impedance network (LISN).

[0031] In one specific embodiment, the converter 3 can be any type of power conversion topology, including but not limited to a single-stage DC-DC converter, an isolated DC-DC converter, a single-stage AC-DC converter, and a multi-stage cascaded power conversion structure. The converter 3 includes at least one transformer 31.

[0032] For example, the transformer 31 includes a primary winding. N 1. The primary winding N1. Electrically connected to the primary power circuit of converter 3, it is the core winding of converter 3 for realizing power conversion and transmission. The transformer 31 includes a secondary winding. N 2 The secondary winding N 2 The common-mode current cancellation circuit 1, which overcomes the tolerance of the compensation capacitor, injects the cancellation current into the converter 3.

[0033] As an example, the primary winding N 1 and the winding of parallel branch 12 N Two common magnetic cores are wound to form a one-to-one common mode magnetic coupling winding pair.

[0034] As an example, the secondary winding N 2 is an anti-parallel cancelling winding, which is a compensation winding.

[0035] In one specific embodiment, please refer to Figure 2 This application provides a common-mode current cancellation circuit 1 for overcoming the tolerance of compensation capacitors, comprising: a tolerance feedback branch 11, which acquires the common-mode voltage signal of the phase line L and neutral line N of the input power supply 2 relative to the protective ground PE, and performs high-pass filtering, voltage follower isolation, low-pass filtering and inverting amplification on the common-mode voltage signal to obtain an equivalent controlled voltage source signal; and a parallel branch 12, which determines a total compensation voltage source signal based on the equivalent controlled voltage source signal, and performs current matching conversion processing on the total compensation voltage source signal to obtain an output cancellation current.

[0036] As an example, the series connection of the tolerance feedback branch 11 and the parallel branch 12 is equivalent to a new compensation voltage source, thereby offsetting the attenuation of the cancellation effect of the original noise source caused by the tolerance of the compensation capacitor.

[0037] As an example, the equivalent controlled voltage source signal is proportional to the common-mode voltage signal.

[0038] As an example, the tolerance feedback branch 11 includes a sampling module 111, which performs high-pass filtering, voltage-following isolation, and low-pass filtering on the common-mode voltage signal of the phase line L and neutral line N of the input power supply 2 relative to the protective ground PE to obtain a sampled voltage signal; and an amplification module 112, which performs inverting amplification on the sampled voltage signal and outputs an equivalent controlled voltage source signal proportional to the common-mode voltage signal.

[0039] In yet another specific embodiment, please refer to Figure 3 The sampling module 111 includes a capacitor. C sens11 ,capacitance C sens12,resistance R sense1 First op-amp U1, resistor R sense2 ,capacitance C sense2 ,capacitance C sens11 The first terminal is connected to the first output terminal of the input power supply 2, and the capacitor... C sens11 The second end is connected to a resistor R sense1 The first terminal, resistor R sense1 The second terminal is connected to the protective ground PE; capacitor C sens12 The first terminal is connected to the second output terminal of the input power supply 2, and the capacitor... C sens12 The second end is connected to a capacitor C sens11 The second terminal and resistor R sense1 The first terminal; the first input terminal of the first operational amplifier U1 is connected to a capacitor. C sens12 The second terminal and capacitor C sens11 The second terminal and resistor R sense1 The first terminal, the second input terminal of the first operational amplifier U1, is connected to the output terminal of the first operational amplifier U1; resistor R sense2 The first terminal is connected to the output terminal of the first operational amplifier U1, and the resistor... R sense2 The second end is connected to a capacitor C sense2 The first terminal, capacitor C sense2 The second terminal is connected to protective ground PE, and the fourth terminal of the first operational amplifier U1 is connected to the power supply. V CC .

[0040] As an example, capacitor C sens11 ,capacitance C sens12 ,resistance R sense1 This constitutes a high-pass filter unit.

[0041] As an example, capacitor C sens11 ,capacitance C sens12 The capacitance values ​​are all C sens1 .

[0042] As an example, resistor R sense1 The second end is the output port of the sampling module 111, and the resistor is... R sense1 The voltage across the two terminals is the output sampling voltage of sampling module 111. V sens1 .

[0043] As an example, the first input terminal of the first operational amplifier U1 is the non-inverting input terminal, and the second input terminal of the first operational amplifier U1 is the inverting input terminal.

[0044] As an example, the first op-amp U1 can be a voltage follower.

[0045] As an example, resistor R sense2 ,capacitance C sense2 This constitutes a low-pass filter unit.

[0046] As an example, capacitor C sens11 ,capacitance C sens12 The first sampling capacitor, the capacitor C sense2 This is the second sampling capacitor. (Resistor) R sense1 The first sampling resistor, the resistor R sense2 This is the second sampling resistor.

[0047] As an example, capacitor C sense2 The voltage at both ends is the sampling voltage output by sampling module 111. V sense2 The expression is: in, Z C_sense1 For capacitor C sens11 and capacitor C sens12 Capacitive resistance, Z C_sense2 For capacitor C sense2 Capacitive resistance, R sense1 The first sampling resistor, R sense2 For the second sampling resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

[0048] As an example, to ensure the sampling voltage V sens1 It accurately reflects the high-frequency characteristics of common-mode noise and approximates the common-mode voltage as closely as possible. v CM To avoid introducing unnecessary filtering effects due to excessively large sampling capacitors, the capacitor should be... C sens11 ,capacitance C sens12 The capacitance value C sens1 The maximum is 20 nF.

[0049] For example, the high-pass filter unit and the low-pass filter unit together form a band-pass filter to avoid sampling low-frequency or high-frequency noise. Adding a first operational amplifier U1 between the high-pass filter unit and the low-pass filter unit can eliminate the impedance coupling effect between them.

[0050] As an example, the passband of a bandpass filter should cover the frequency band of conducted electromagnetic interference, i.e., 150kHz-30MHz.

[0051] Furthermore, the amplification module 112 includes: a resistor R A1 Second operational amplifier U2, resistor R Af ,resistance R A1 The first end is connected to a resistor R sense2 The second terminal, resistor R A1 The second terminal is connected to the first input terminal of the second operational amplifier U2; the second input terminal of the second operational amplifier U2 is connected to the protective ground PE; resistor R Af The first end is connected to a resistor R A1 The second terminal and the first input terminal of the second operational amplifier U2, resistor R Af The second terminal is connected to the output terminal of the second operational amplifier U2, and the fourth terminal of the second operational amplifier U2 is connected to the power supply. V CC The output voltage of amplifier module 112 is V Ao .

[0052] As an example, resistor R A1 This is the input resistance.

[0053] As an example, resistor R Af This is the feedback resistor.

[0054] For example, the first input terminal of the second op-amp U2 is the inverting input terminal, and the second input terminal of the second op-amp U2 is the non-inverting input terminal. The second op-amp U2 can be an inverting amplifier.

[0055] As an example, the output signal of the amplification module 112 serves as an equivalent controlled voltage source on the parallel branch 12. The equivalent controlled voltage source is connected in series with the original compensation voltage source of the parallel branch 12 to form a new compensation voltage source, thereby offsetting the attenuation of the cancellation effect of the original noise source caused by the tolerance of the compensation capacitor.

[0056] As an example, the output voltage of amplifier module 112 is V Ao Opposite to the direction of the equivalent controlled voltage source of the tolerance feedback branch 11, the output of the second operational amplifier U2 is connected in series with the parallel branch 12, so that the reference direction of the equivalent controlled voltage source of the tolerance feedback branch 11 is consistent with that of the original compensation voltage source of the parallel branch 12.

[0057] As an example, the larger the amplification factor of the amplification module 112, the more obvious the feedback compensation effect, and the better the suppression effect of the tolerance feedback branch 11 on the insertion loss attenuation. However, due to the limitation of the gain-bandwidth product of the second operational amplifier U2, the amplification factor cannot be too large, and a trade-off must be made between the effective bandwidth and the gain.

[0058] In this embodiment, the closed-loop gain of the second operational amplifier U2 is set to 5, and the effective bandwidth covers 30MHz.

[0059] As an example, parallel branch 12 includes a capacitor. C comp ,capacitance C comp The first terminal is connected to the output terminal of the second operational amplifier U2, and the capacitor... C comp The second end is connected to the secondary winding. N 2.

[0060] As an example, capacitor C comp For compensation capacitors.

[0061] As an example, parallel branch 12 is used to generate a voltage source signal corresponding to the primary winding based on the controlled voltage source signal output by tolerance feedback branch 11. N 1. A compensating magnetic field in the opposite direction of the common-mode current is used to cancel common-mode noise.

[0062] In one embodiment, see Figure 3 The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor in this application further includes a capacitor. C s1When the power switching transistor inside converter 3 performs high-speed switching, a very high voltage change rate dv / dt or current change rate di / dt is generated at the switching node. This voltage change rate dv / dt or current change rate di / dt provides common-mode noise current to the linear stable impedance network side through the parasitic capacitance from the switching transistor through the heat sink to the protective ground. The common-mode noise current is the target current that the entire common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor needs to suppress.

[0063] It is important to note that the voltage change rate dv / dt or current transformation rate di / dt here is different from the common-mode voltage concept defined in standard conducted emission testing. Common-mode voltage specifically refers to the voltage drop generated after the common-mode noise current flows through the equivalent impedance inside the linear stable impedance network, which is the interference value actually measured by the test equipment. The voltage change rate dv / dt or current transformation rate di / dt at the switching node is the fundamental excitation source that causes the noise current.

[0064] As an example, capacitor C s1 This is the equivalent parasitic capacitance of the common-mode noise equivalent circuit of converter 3.

[0065] As an example, capacitor C s1 It can be the series / parallel connection of several actual parasitic capacitances in converter 3, rather than the nominal value of a single physical component.

[0066] For example, the protective ground (PE) can be the radiator ground or the chassis ground.

[0067] This application is in capacitor C comp The equivalent controlled voltage source output by the front-end series tolerance feedback branch, when the capacitor... C comp When the capacitance value deviates, the capacitor is automatically adjusted. C comp The total voltage across the terminals ensures that the cancellation current always matches the common-mode current, thereby overcoming the tolerance effect.

[0068] The following analysis uses converter 3 as an example of a two-stage power converter to illustrate the working principle of a common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor in this application.

[0069] Specifically, based on the fundamental principles of electromagnetic compatibility, the power switching devices, transformer parasitic capacitance, and heat sink-to-ground capacitance in the converter are equivalent to common-mode noise sources, combined with the common-mode equivalent impedance of the linear stable impedance network. Z LISNThe equivalent common-mode noise model of the two-stage power converter using common-mode current cancellation technology is obtained and simplified to obtain the first simplified common-mode interference model. In the first simplified common-mode interference model, the high-frequency switching operation of converter 3 is in the primary winding. N 1 generates the primary voltage of the high-frequency transformer. v A The primary voltage of the transformer v A via capacitor C s1 A common-mode current is generated, flowing through the protective earth (PE) circuit of detection device 4, and a common-mode voltage is generated across the detection resistor. v CM .

[0070] As an example, the common-mode equivalent impedance of a linear impedance stabilization network can be set to a standard impedance, typically 25Ω.

[0071] Furthermore, based on the passive cancellation technique, a compensation branch, namely parallel branch 12, is added to the simplified common-mode interference model to obtain the simplified common-mode noise model of the original cancellation circuit, as follows: Figure 4 As shown, where C comp To compensate for the capacitor, C s1 This is the equivalent parasitic capacitance of the common-mode noise equivalent circuit of converter 3. v comp To compensate for the voltage source's compensation voltage, v CM Common-mode voltage, v ENS As an equivalent common-mode noise excitation source, Z LISN This represents the common-mode equivalent impedance of the linear impedance-stabilized network. In the simplified model of the second common-mode noise, the compensation branch is the compensation capacitor. C comp Composition, compensation capacitor C comp With secondary winding N 2 series windings, secondary winding N 2 and the primary winding of transformer 31 N 1. Common core coupling enables the secondary winding N 2. The voltage generated by the upper inductance is related to the primary voltage of transformer 31. v A Proportional compensation voltage v comp The expression is: By setting compensation capacitors C comp The transformer turns ratio satisfies the charge conservation formula: Theoretically, the canceling current generated by the compensation branch can be made to have the same amplitude but opposite phase as the original common-mode current, thereby guiding the common-mode noise current to the compensation branch, reducing the current flowing through the LISN sensing resistor, and achieving conducted interference suppression. This is the primary voltage of the transformer. This is the lumped capacitance equivalent to the distributed capacitance on the primary and secondary sides. This refers to the capacitance of the converter switching node to protective ground.

[0072] However, in practical engineering applications, the actual capacitance value of compensation capacitors is inevitably subject to manufacturing tolerances due to factors such as material purity, manufacturing process, and film thickness uniformity. Common accuracy grades include ±20%, ±10%, and ±5%, and even high-precision capacitors have a deviation of around ±1%. Studies have shown that a tolerance of ±10% in compensation capacitors can lead to a decrease in common-mode rejection ratio of more than 10dB. Even a small tolerance can disrupt the charge conservation condition, resulting in a sharp decline in the cancellation effect.

[0073] To address the aforementioned issues, this application overcomes the common-mode current cancellation circuit for compensating capacitor tolerance by connecting a tolerance feedback branch 11 in series with the parallel branch. The tolerance feedback branch 11 acquires the common-mode voltage signals from the phase line L and neutral line N relative to the protective ground PE provided by the detection device 4. These signals are then sequentially processed through high-pass filtering, voltage follower isolation, low-pass filtering, and inverting amplification to generate an equivalent controlled voltage source signal proportional to the common-mode voltage signal. This equivalent controlled voltage source signal, along with the compensation voltage generated by the parallel branch 12 itself, is then... v comp The capacitors are connected in series with the same reference direction to form the corrected total compensation voltage. This total compensation voltage is then applied to the compensation capacitor. C comp At both ends, there are compensation capacitors. C comp The cancelling current generated can re-satisfy the new charge conservation relationship, thereby dynamically offsetting the cancellation deviation caused by the capacitor tolerance. The common-mode interference conduction model of the common-mode current cancellation circuit that overcomes the capacitor tolerance in this application is as follows: Figure 5 As shown, where C comp To compensate for the capacitor, C s1 This is the equivalent parasitic capacitance of the common-mode noise equivalent circuit of converter 3. v comp To compensate for voltage, v CM Common-mode voltage, v ENS As an equivalent common-mode noise excitation source, v G This is the equivalent controlled voltage source for the tolerance feedback branch. Z LISNThis is the common-mode equivalent impedance of a linear impedance-stabilized network.

[0074] As an example, the equivalent controlled voltage source of the tolerance feedback branch v G The expression is: in, This represents the actual closed-loop gain of the amplification module. Z C_sense1 For capacitor C sens11 and capacitor C sens12 Capacitive resistance, Z C_sense2 For capacitor C sense2 Capacitive resistance, R sense1 The first sampling resistor, R sense2 For the second sampling resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

[0075] For example, assuming the winding ratio is 1:1, the new charge conservation formula is as follows: in, To compensate for the capacitance tolerance, To compensate for voltage, It is a controlled voltage source. To compensate for the capacitor, This is the primary voltage of the transformer. This is the lumped capacitance equivalent to the distributed capacitance on the primary and secondary sides. This refers to the capacitance of the converter switching node to protective ground.

[0076] For example, to verify the effectiveness of the technical solution of this application, the common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor was built in the power electronics simulation software PSIM. The converter 3 is a two-stage AC-DC power converter, and the tolerance of the compensation capacitor is set to 20%. The insertion loss of the feedback branch with tolerance and the feedback branch without tolerance are compared in the 150k-30MHz frequency band. Figure 6This chart compares the simulated common-mode noise spectra of the converter with and without a tolerance feedback branch when using passive noise cancellation. The black dashed line represents the noise spectrum envelope of the passive noise cancellation model without a tolerance feedback branch, while the gray solid line represents the noise spectrum envelope of the passive noise cancellation model with a tolerance feedback branch. This example more clearly illustrates the relevant insertion loss data and demonstrates two comparison methods between theoretical calculations and simulated spectra. Figure 7 The graph shows the insertion loss curves of the theoretically calculated and simulated spectrum transformations when the converter employs passive noise cancellation with a tolerance feedback branch compared to one without. It can be seen that the tolerance feedback branch significantly improves the insertion loss of the passive noise cancellation technique by more than 20dB across the entire frequency band, even with a 20% tolerance. The insertion loss is also higher than that of the original noise. The simulation results are in high agreement with the theoretical calculations, verifying the correctness of the tolerance feedback compensation principle proposed in this application.

[0077] It is understood that the aforementioned specific software PSIM is merely an exemplary means of implementing this technical solution and is not intended to limit the present invention. Those skilled in the art can choose other suitable power electronics simulation tools to achieve the same technical purpose based on the teachings of this disclosure.

[0078] In the aforementioned common-mode current cancellation circuit that overcomes the tolerance of the compensation capacitor, the common-mode voltage signal is obtained through the tolerance feedback branch 11. After high-pass filtering, voltage following, low-pass filtering, and inverting amplification, an equivalent controlled voltage source is generated. This source is then connected in series with the basic compensation voltage source of the parallel branch 12 in the same reference direction, forming a dynamically corrected total compensation voltage. This voltage can compensate in real time for the deviation between the basic compensation voltage and the original common-mode voltage caused by the capacitor tolerance. It ensures that the cancellation current maintains amplitude matching and opposite direction to the original common-mode current across the entire frequency band, significantly reducing the dependence on high-precision compensation capacitors. It provides sufficient effective bandwidth to cover electromagnetic interference and exhibits good attenuation of noise signals across the entire frequency band, significantly improving the robustness of the component parameters in passive cancellation technology. This invention is simple in principle and, when combined with passive cancellation technology, is applicable to most scenarios requiring common-mode noise reduction, making it widely applicable.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of this application.

Claims

1. A common-mode current cancellation circuit for overcoming the tolerance of compensation capacitors, characterized in that, include: The tolerance feedback branch acquires the common-mode voltage signals of the first and second output terminals of the input power supply relative to the protective ground, performs inverting amplification processing on the common-mode voltage signals, and obtains the controlled voltage source signal. The parallel branch determines the total compensation voltage source signal based on the controlled voltage source signal, and performs current matching conversion processing on the total compensation voltage source signal to obtain the output cancellation current; The parallel branch includes a compensation capacitor. The first end of the compensation capacitor is connected to the output end of the tolerance feedback branch, and the second end of the compensation capacitor is connected to the secondary winding of the transformer. The secondary winding of the transformer is coupled to the primary winding of the transformer via a common magnetic core to generate a base compensation voltage. The controlled voltage source signal output from the tolerance feedback branch is connected in series with the base compensation voltage in the same reference direction to form a total compensation voltage source signal. The total compensation voltage source signal is applied across the compensation capacitor.

2. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 1, characterized in that, The tolerance feedback branch includes: The sampling module performs high-pass filtering, voltage-following isolation, and low-pass filtering on the common-mode voltage signals of the phase line and neutral line of the input power supply relative to the protective ground to obtain the sampled voltage signal. An amplification module performs inverting amplification on the sampled voltage signal and outputs an equivalent controlled voltage source signal that is proportional to the common-mode voltage signal.

3. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 2, characterized in that, The sampling module includes: a first capacitor, a second capacitor, a first resistor, a first operational amplifier, a second resistor, and a third capacitor. The first terminal of the first capacitor is connected to the first terminal of the input power supply; the second terminal of the first capacitor is connected to the first terminal of the first resistor; and the second terminal of the first resistor is connected to protective ground. The first terminal of the second capacitor is connected to the second terminal of the input power supply; the second terminal of the second capacitor is connected to the second terminal of the first capacitor and the first terminal of the first resistor. The first input terminal of the first operational amplifier is connected to the second terminal of the second capacitor, the second terminal of the first capacitor, and the first terminal of the first resistor; the second input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier. The first terminal of the second resistor is connected to the output terminal of the first operational amplifier; the second terminal of the second resistor is connected to the first terminal of the third capacitor; and the second terminal of the third capacitor is connected to protective ground.

4. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 3, characterized in that, The voltage across the third capacitor is the sampling voltage output by the sampling module. V sense2 The expression is: in, Z C_sense1 Let be the capacitive reactance of the first capacitor and the second capacitor. Z C_sense2 The capacitive reactance of the third capacitor. R sense1 The first resistor, R sense2 For the second resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

5. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 4, characterized in that, The first capacitor, the second capacitor, and the first resistor constitute a high-pass filter unit, and the second resistor and the third capacitor constitute a low-pass filter unit; the high-pass filter unit and the low-pass filter unit together constitute a band-pass filter.

6. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 2, characterized in that, The amplification module includes: a third resistor, a second operational amplifier, and a fourth resistor. The first end of the third resistor is connected to the second end of the second resistor, and the second end of the third resistor is connected to the first input terminal of the second operational amplifier. The second input terminal of the second operational amplifier is connected to protective ground. The first end of the fourth resistor is connected to the second end of the third resistor and the first input terminal of the second operational amplifier, and the second end of the third resistor is connected to the output terminal of the second operational amplifier.

7. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 6, characterized in that, The output voltage of the amplifier module serves as an equivalent controlled voltage source.

8. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 7, characterized in that, When the tolerance feedback branch is connected in series with the parallel branch, it is equivalent to a new compensation voltage source. The equivalent controlled voltage source of the tolerance feedback branch has the same reference direction as the original compensation voltage source of the parallel branch.

9. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to claim 8, characterized in that, Equivalent controlled voltage source v G The expression is: in, This represents the actual closed-loop gain of the amplification module. Z C_sense1 Let be the capacitive reactance of the first capacitor and the second capacitor. Z C_sense2 The capacitive reactance of the third capacitor. R sense1 The first resistor, R sense2 For the second resistor, R A1 This is the input resistance of the amplification module. v CM This is the common-mode voltage.

10. A power electronic conversion device, characterized in that, include: Input power, output electrical energy; The converter, with power semiconductor switching devices as its core, receives electrical energy output from the input power supply and performs power conversion. During the power conversion process, the high-frequency switching action of the power semiconductor switching devices generates common-mode noise signals through the parasitic capacitance to ground of the potential switching nodes. The common-mode current cancellation circuit for overcoming the tolerance of the compensation capacitor according to any one of claims 1 to 9 receives the electrical energy output by the input power supply and the common-mode noise signal generated by the converter, performs phase inversion and amplitude matching processing to obtain a cancellation current, and injects the cancellation current into the converter to cancel the common-mode current generated therefrom.

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