A boost inductance-based auxiliary winding type common-mode conducted electromagnetic interference counter-acting circuit

Abstract

This invention proposes an auxiliary winding-type common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit based on a Boost inductor, applicable to Boost converters. This invention is based on the drain-source voltage vo of the internal power MOS in the Boost converter. DS This involves understanding its conducted electromagnetic interference noise source, and constructing an auxiliary winding coupled with a power inductor to connect with v. DS Compensation voltages v with the same waveform shape and proportional amplitude comp Through two compensation capacitors C comp1 With C comp2 Injecting compensation current reverses and cancels common-mode conducted electromagnetic interference (EMI) within the converter. Under ideal coupling conditions between the power inductor and auxiliary winding, this invention can completely cancel EMI within the converter; under non-ideal coupling conditions, it can provide amplitude attenuation exceeding 20dB, with a maximum of 40dB, within a frequency range of 150kHz-5MHz. This invention uses only three passive components, offering advantages such as simple structure, small size, low cost, and easy integration.

Description

Technical Field

[0001] This invention relates to the field of modeling and suppressing conducted electromagnetic interference in switching power supplies, and particularly to an auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on a Boost inductor. Background Technology

[0002] Electromagnetic interference (EMI) refers to the amplitude of electromagnetic noise generated by electronic equipment or systems during operation. Excessive EMI can affect other electrical equipment in the same space, even causing them to malfunction. To reduce the interference of various electronic devices on other equipment, various countries and regions have successively introduced mandatory electromagnetic compatibility standards for different electronic products. On the other hand, the ever-increasing switching frequencies and increasingly compact PCB layouts have made conducted electromagnetic interference in switching power supplies more and more serious. Suppressing conducted electromagnetic interference has become an urgent problem to be solved.

[0003] As academic research into the mechanisms of electromagnetic interference continues to deepen, various methods for suppressing conducted electromagnetic interference have been proposed. These methods can be broadly categorized into two types: 1) noise reduction after noise generation; and 2) noise reduction during the noise generation stage.

[0004] Noise reduction after noise generation, i.e., filtering, is currently the most common method in the power electronics industry. Mainstream filtering schemes are divided into passive EMI filtering and active EMI filtering (AEF). Passive EMI filtering mainly uses low-pass filters composed of passive components such as inductors and capacitors to suppress EMI noise. Passive EMI filters are large, sometimes occupying up to 30% of the converter area, which is detrimental to high power density designs. Active EMI filters utilize active devices such as operational amplifiers or transistors to construct feedforward / feedback circuits for EMI noise suppression. They are very small, but limited by bandwidth requirements, resulting in higher costs and hindering industrial adoption. Emerging digital active filters also face similar problems.

[0005] Noise reduction during the noise generation stage is mainly achieved through three approaches: 1) selecting or designing appropriate components, or improving PCB layout; 2) using better switching modulation schemes; and 3) soft-switching technology. However, current research is insufficient, a complete theoretical system has not yet been formed, and effective evaluation methods are lacking.

[0006] This invention proposes a circuit structure for an auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on a Boost inductor. The circuit structure is simple and has the advantages of small size and light weight compared to passive EMI filters. The circuit uses only a few passive components and has the advantages of low cost and easy integration compared to active EMI filters. Summary of the Invention

[0007] This invention provides a circuit structure for an auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on a Boost inductor. This circuit structure eliminates voltage sampling and feedback, resulting in a simple structure; it uses only three passive components, making it low-cost, easy to implement, and extremely compact.

[0008] A common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit based on an auxiliary winding of a Boost inductor is applied to a Boost converter. This circuit utilizes the auxiliary winding coupled to the Boost power inductor to construct an EMI reverse cancellation circuit against the internal noise source v of the converter. DS Compensation voltage sources with the same waveform shape and proportional amplitude v comp After passing through two compensation capacitors C comp1 With C comp2 Injected into the busbar, it reverses and cancels common-mode conducted electromagnetic interference in the circuit; the circuit structure includes an auxiliary winding L coupled to the power inductor. aux and two compensation capacitors C comp1 With C comp2 Among them, the auxiliary winding L aux Coupled with the power inductor L of the Boost converter, one end is connected to the common ground of the Boost converter, and the other end is connected to two compensation capacitors C. comp1 With C comp2 The common connection terminal; the terminal connected to the converter's common ground and the terminal connected to the positive input bus of the Boost converter by the power inductor L are of the same name; the two compensation capacitors C comp1 With C comp2 One end is connected to the other, and the other end is connected to the positive and negative input buses of the Boost converter respectively. The auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on the Boost inductor can completely cancel the common-mode conducted electromagnetic interference in the circuit under the condition of ideal coupling between the auxiliary winding and the power inductor winding, and obtain a good attenuation effect in the full frequency range. The circuit can also work under the condition of non-ideal coupling between the auxiliary winding and the power inductor winding, and can obtain a good attenuation effect in the frequency range below 10MHz.

[0009] The two compensation capacitors C comp1 With C comp2 Their capacitance, model, package, and specifications are all identical to form a symmetrical circuit structure, that is:

[0010]

[0011] The two compensation capacitors C comp1 With C comp2 The compensation current flowing through it is extremely small, so a small-package surface-mount MLCC ceramic capacitor is selected to reduce the size. It is only necessary to ensure that its voltage rating is higher than half of the input bus voltage of the Boost converter.

[0012] The auxiliary winding L aux It is coupled to the power inductor L of the Boost converter to induce a compensation voltage v. comp This allows for the injection of compensation current into the busbar. Because the compensation current is extremely small, the auxiliary winding is very simple to construct. For wound power inductors, the auxiliary winding can be directly wound onto the core of the power inductor using copper wires with a small diameter; for planar power inductors, the auxiliary winding can be constructed by adding fine traces to the copper foil layer, increasing the volume almost indiscriminately.

[0013] The auxiliary winding L aux The turns ratio of the power inductor L in the Boost converter can be flexibly adjusted according to the actual situation of the converter. The reverse cancellation circuit is in the auxiliary winding L. aux The cancellation effect is best under ideal coupling with the power inductor L. If a better attenuation effect is desired across the entire frequency range, a turns ratio of 1:1 should be selected, and the thick wire of the power inductor should be twisted together with the thin wire of the auxiliary winding to obtain a higher coupling coefficient. If a simple circuit with a very small size and low component parameter sensitivity is required, only one turn of the auxiliary winding can be selected.

[0014] When the Boost power inductor and auxiliary winding are ideally coupled, the capacitance C of the two compensation capacitors is... comp1 With C comp2 The capacitance C of the parasitic capacitance to ground at the Boost converter jumper point par The number of turns n of the power inductor L of the Boost converter and the auxiliary winding L aux number of turns n aux The following relationship should be satisfied between them:

[0015]

[0016] At this time, the common-mode noise inverse cancellation circuit can completely cancel the common-mode conducted electromagnetic interference of the Boost converter, and achieve a good attenuation effect across the entire frequency band.

[0017] When the Boost power inductor and auxiliary winding are not ideally coupled, the capacitance C of the two compensation capacitors... comp1 With C comp2 The capacitance C of the parasitic capacitance to ground at the Boost converter jumper point parThe self-inductance L of the power inductor in the Boost converter and the mutual inductance M between the power inductor winding and the auxiliary winding should satisfy the following relationship:

[0018]

[0019] At this point, the common-mode noise reverse cancellation circuit can reverse cancel the common-mode conducted electromagnetic interference of the Boost converter in the low-frequency range of conducted electromagnetic interference, typically 150kHz-10MHz. However, due to the leakage inductance introduced by non-ideal coupling, the constructed compensation voltage has ringing, introducing an extremely high-frequency resonance peak to the converter. This resonance peak can be filtered out by an external filter or suppressed by adding a damping resistor to the injection branch. Since the resonance frequency is extremely high, the required external filter size is extremely small.

[0020] This invention constructs a structure that corresponds to the noise source v DS Compensation voltages v with the same waveform shape and proportional amplitude comp This invention also incorporates impedance matching to counteract common-mode conducted electromagnetic interference (EMI) within the converter. Applicable to Boost converters, it completely cancels common-mode conducted EEMI under ideal coupling between the power inductor and auxiliary winding; under non-ideal coupling, it provides over 20dB of amplitude attenuation within a frequency range of 150kHz-5MHz. This invention features a simple structure, low cost, small size, and easy integration, making it widely applicable to Boost topology converters, such as DC-DC Boost converters and Boost-type PFCs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on Boost inductor described in this invention, and a connection diagram when it is applied to a Boost circuit.

[0022] Figure 2 This is the common-mode equivalent circuit diagram of the common-mode conducted electromagnetic interference reverse cancellation circuit described in this invention when applied to a Boost circuit.

[0023] Figure 3 Under ideal coupling conditions between the power inductor and the auxiliary winding, when the common-mode conducted electromagnetic interference reverse cancellation circuit described in this invention is applied to a Boost circuit, the converter PWM signal and the internal noise source v of the converter... DS The constructed compensation voltage source v comp and the injected compensation current i comp The waveform diagram.

[0024] Figure 4Under ideal coupling conditions between the power inductor and the auxiliary winding, the common-mode conducted electromagnetic interference (CMEMI) spectrum comparison of the common-mode conducted electromagnetic interference before and after the common-mode conducted electromagnetic interference (CMEMI) reverse cancellation circuit described in this invention is applied to the Boost circuit.

[0025] Figure 5 Under the condition of non-ideal coupling between the power inductor and the auxiliary winding (coupling coefficient between the power inductor and the auxiliary winding is 0.8), when the common-mode conducted electromagnetic interference reverse cancellation circuit described in this invention is applied to the Boost circuit, the converter PWM signal and the internal noise source v of the converter... DS The constructed compensation voltage source v comp and the injected compensation current i comp The waveform diagram.

[0026] Figure 6 Under the condition of non-ideal coupling between the power inductor and the auxiliary winding (the coupling coefficient between the power inductor and the auxiliary winding is 0.8), the common-mode conducted electromagnetic interference reverse cancellation circuit described in this invention is applied to the Boost circuit before and after a comparison of the common-mode conducted electromagnetic interference spectrum. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0028] This invention is based on the drain-source voltage v of the power MOSFET Q in the Boost converter. DS This involves recognizing the noise source of common-mode conducted electromagnetic interference within the converter, and constructing an auxiliary winding to interact with v. DS Compensation voltage sources with the same waveform shape and proportional amplitude v comp And through appropriate connection and impedance matching, it can be reverse-cancelled. DS This causes common-mode conducted electromagnetic interference.

[0029] For a Boost converter, when the power MOSFET is turned on, its drain-source voltage v DS When the voltage is zero, the voltage drop across the power inductor L is equal to the input bus voltage V. in When the power MOSFET is turned off, its drain-source voltage v DS Output voltage V o At this time, the voltage at one end of the power inductor L is equal to the input bus voltage V. in The voltage at one end is the output voltage V. o The voltage drop across the two ends is V in -V oTherefore, the voltage drop across the power inductor L is v. L The waveform shape and the drain-source voltage of the power MOS DS They are exactly the same, but the amplitudes are proportional. Using an auxiliary winding coupled to the power inductor, an amplitude similar to v can be induced. DS Compensation voltage sources with the same waveform shape and proportional amplitude v comp Through proper connection, its polarity can be made similar to v. DS Conversely; by compensating capacitor C comp1 and C comp2 Parasitic capacitance to ground at the jump point of the Boost converter C par Impedance matching allows the injected compensation current to be matched with v. DS The resulting common-mode conducted electromagnetic interference current is canceled out in the opposite direction.

[0030] Figure 1 A schematic diagram of the proposed auxiliary winding type common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit based on a Boost inductor and its connection diagram when applied to a Boost circuit are shown. The circuit structure includes an auxiliary winding L coupled to the Boost power inductor. aux And two compensation capacitors C comp1 With C comp2 The LISN circuit is a general-purpose linear impedance-stabilized network, where R... LISN =50Ω, L LISN =50μH, C1=0.1μF, C2=1μF. The detailed connection relationship of the circuit is described below:

[0031] The compensation capacitor C comp1 With C comp2 One end is connected to the other, and the other end is connected to the positive and negative input buses of the Boost converter respectively, forming the injection branch of the reverse cancellation circuit;

[0032] When the circuit is applied to a Boost converter, the auxiliary winding L coupled to the power inductor L... aux One end is connected to the common ground of the converter, and the other end is connected to two compensation capacitors C. comp1 With C comp2 The common connection terminal; the end connected to the converter common ground and the end of the power inductor L connected to the converter input positive bus are of the same name;

[0033] Figure 2 The common-mode equivalent circuit diagram of the proposed common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit applied to a Boost circuit is shown. To reverse cancel common-mode conducted EEMI, the following must first be satisfied:

[0034]

[0035] The compensating voltage v can be constructed using Thevenin's equivalent theorem. comp With the internal noise source v of the Boost converter DS Equivalent to a noise source v eq Parasitic capacitance C of the Boost converter jump point to ground par The two compensation capacitors can be equivalent to a single capacitor C. eq The corresponding expression is:

[0036]

[0037] Under ideal coupling conditions between the power inductor and the auxiliary winding, in order to achieve reverse cancellation between the compensation signal and the internal noise signal of the Boost converter, the capacitance C of the compensation capacitor is... comp Number of turns n in the auxiliary winding aux The number of turns n of the converter power inductor and the capacitance C of the Boost converter jumper to ground. par The following conditions must be met:

[0038]

[0039] Under non-ideal coupling conditions between the power inductor and the auxiliary winding, in order to achieve reverse cancellation between the compensation signal and the internal noise signal of the Boost converter, the capacitance C of the compensation capacitor is... comp The self-inductance L of the auxiliary winding aux The self-inductance L of the converter power inductor, the mutual inductance M between the auxiliary winding and the power inductor winding, and the capacitance C of the parasitic capacitance C of the Boost converter jumper to ground. par The following conditions must be met:

[0040]

[0041] Figure 3 This illustrates the common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit, proposed under ideal coupling conditions between the power inductor and auxiliary winding, when applied to a Boost converter, as simulated in Simulink. The results show the PWM signal and internal noise source v. DS The constructed compensation voltage source v comp and the injected compensation current i comp The waveform diagram is shown. The simulated Boost converter operates in CCM mode with an input voltage of 15V, an output voltage of 30V, and an output power of 120W. The turns ratio between the Boost power inductor winding and the auxiliary winding is 10:1. The constructed compensation voltage source v... comp With the noise source v inside the converter DSThe waveforms are identical in shape and proportional in amplitude (with a certain DC bias, but the DC bias has no effect on EMI). The compensation current is a periodic pulse, but the peak value is only 40mA, which is very small compared to the power current and has little impact on the power loop.

[0042] Figure 4 The diagram shows a comparison of the common-mode conducted electromagnetic interference (CMEMI) spectrum before and after applying the proposed reverse common-mode noise cancellation circuit to a Boost converter under ideal coupling conditions of the power inductor and auxiliary winding, as simulated in Simulink. The lighter-colored line represents the CEMI spectrum of the Boost converter without the reverse common-mode noise cancellation circuit; the darker-colored line represents the CEMI spectrum of the Boost converter with the reverse common-mode noise cancellation circuit. After incorporating the reverse cancellation circuit, the CEMI spectrum of the Boost converter exhibits an attenuation of over 40 dB across the entire frequency range, demonstrating the effectiveness of the proposed circuit.

[0043] Figure 5 This illustrates the simulation results in Simulink, showing the proposed common-mode conducted electromagnetic interference (EMI) reverse cancellation circuit under non-ideal coupling conditions between the power inductor and auxiliary winding, applied to a Boost converter. The simulation results also demonstrate the interaction between the PWM signal and the internal noise source v. DS The constructed compensation voltage source v comp and the injected compensation current i comp The waveform diagram is shown. At this time, the self-inductance of the Boost converter power inductor is 100μH, the self-inductance of the auxiliary winding is 1μH, and the coupling coefficient between the two windings is 0.8. At this time, due to the influence of non-ideal coupling, the compensation voltage source v based on the auxiliary winding... comp Ringing occurred on both the rising and falling edges, affecting the injected compensation current i. comp middle.

[0044] Figure 6 The diagram shows a comparison of the common-mode conducted electromagnetic interference (CMEMI) spectrum of a Boost converter before and after applying the proposed reverse coupling circuit for non-ideal coupling between the power inductor and auxiliary winding, obtained from Simulink simulations. The lighter-colored line represents the CEMI spectrum of the Boost converter without the reverse coupling circuit; the darker-colored line represents the CEMI spectrum after the reverse coupling circuit is applied. After applying the reverse coupling circuit, the CEMI spectrum of the Boost converter shows significant attenuation in the low-frequency range, verifying the effectiveness of the circuit. In the high-frequency range, leakage inductance caused by non-ideal coupling results in a high resonant frequency peak, but due to the extremely high resonant frequency, it can be filtered out by a very small external passive filter.

Claims

1. An auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on a Boost inductor, applied to a Boost converter, characterized in that: An auxiliary winding coupled to the boost power inductor is used to construct a noise source within the converter. Compensation voltage sources with the same waveform shape and proportional amplitude After passing through two compensation capacitors and Injected into the busbar, it reverses and cancels common-mode conducted electromagnetic interference in the circuit; the circuit structure includes an auxiliary winding coupled to the power inductor. and two compensation capacitors and Among them, auxiliary winding With the power inductor of the Boost converter Phase-coupled, one end is connected to the common ground of the Boost converter, and the other end is connected to two compensation capacitors. and The common connection terminal; the terminal connected to the converter's common ground and the power inductor The ends connected to the positive input bus of the Boost converter are terminals with the same name; two compensation capacitors and One end is connected to the other end, and the other end is connected to the positive and negative input buses of the Boost converter respectively. The auxiliary winding type common-mode conducted electromagnetic interference reverse cancellation circuit based on Boost inductor can completely cancel the common-mode conducted electromagnetic interference in the circuit under the condition of ideal coupling between the auxiliary winding and the power inductor winding, and obtain attenuation effect in the full frequency range. The circuit can also work under the condition of non-ideal coupling between the auxiliary winding and the power inductor winding.

2. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: The two compensation capacitors and Their capacitance, model, package, and specifications are all identical to form a symmetrical circuit structure, that is: 。 3. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: Two compensation capacitors and Surface-mount MLCC ceramic capacitors are selected to reduce size; it is sufficient to ensure that their voltage rating is higher than half of the input bus voltage of the Boost converter.

4. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: The auxiliary winding With Boost converter power inductor Mutual coupling is used to induce compensation voltage. This allows for the injection of compensation current into the busbar.

5. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: The auxiliary winding With Boost converter power inductor The turns ratio can be flexibly adjusted according to the actual situation of the converter. The reverse cancellation circuit is in the auxiliary winding. With power inductor The cancellation effect is best under ideal coupling conditions. If a better attenuation effect is desired across the entire frequency range, a turns ratio of 1:1 should be selected, and the thick wire of the power inductor should be twisted together with the thin wire of the auxiliary winding to obtain a higher coupling coefficient. If a simple circuit with a very small size and low component parameter sensitivity is required, then only one turn of the auxiliary winding can be selected.

6. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: When the Boost power inductor and auxiliary winding are ideally coupled, the capacitance values ​​of the two compensation capacitors are... and The capacitance of the Boost converter jumper to ground parasitic capacitance. Boost converter power inductor number of turns and auxiliary winding number of turns The following relationship should be satisfied between them: At this point, the reverse cancellation circuit can completely cancel the common-mode conducted electromagnetic interference of the Boost converter.

7. The circuit structure of the common-mode conducted electromagnetic interference reverse cancellation circuit according to claim 1, characterized in that: When the Boost power inductor and auxiliary winding are not ideally coupled, the capacitance values ​​of the two compensation capacitors are... and The capacitance of the Boost converter jumper to ground parasitic capacitance. Self-inductance of the power inductor in a Boost converter And the mutual inductance between the power inductor winding and the auxiliary winding The following relationship should be satisfied between them: At this time, the reverse cancellation circuit can reverse cancel the common-mode conducted electromagnetic interference of the Boost converter in the low-frequency range of conducted electromagnetic interference, 150kHz-10MHz.

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