Multi-level pulse compensation type active EMI (Electro-Magnetic Interference) filter applied to multi-noise source switching power supply

Abstract

The invention discloses a multi-level pulse compensation type active EMI (Electro-Magnetic Interference) filter suitable for a multi-noise source switching power supply and a control method of the multi-level pulse compensation type active EMI filter. The invention provides a multi-level pulse compensation scheme based on switch behavior modeling, aiming at the problem of common-mode noise of adjacent rising edges and falling edges generated by a high-frequency switch in a multi-noise-source switching power supply. The time sequence delay and the edge slope of the compensation signal are calculated by analyzing the dv / dt characteristics in the switching-on and switching-off processes of the switching device, and accurate matching and offset with a noise source in phase and amplitude are achieved. Compensation control logic is realized by sharing a main control chip with a power circuit, and an additional controller and a high-precision sampling system are not needed; the self-adaptive tracking of the compensation amplitude is realized through the voltage following circuit; a multi-level compensation signal is output through the totem-pole circuit and injected into a common-mode path, and effective suppression of electromagnetic interference is achieved. The converter has the advantages of small size, low cost, simplicity and convenience in installation, high stability and the like, and is suitable for various multi-noise-source power electronic systems including a dual-active bridge converter, a phase-shifted full-bridge converter and an interleaving Buck converter.

Description

Technical Field

[0001] The present invention relates to the technical field of EMI suppression of switching power supplies, in particular to a multi-level pulse compensation type active electromagnetic interference filter applied to multiple noise sources. Background Art

[0002] With the development of high-frequency, high-efficiency power electronics technology, switching power supply topologies with multiple noise sources, particularly isolated full-bridge converters and interleaved parallel converters, have been widely adopted in high-performance scenarios such as electric vehicles, server power supplies, and photovoltaic energy storage systems. These converters offer advantages such as soft switching, high power density, and excellent bidirectional energy transfer capabilities. However, during operation, the high-speed turn-on and turn-off of switching devices generates a large common-mode voltage change rate, which in turn generates strong common-mode electromagnetic interference.

[0003] In existing technologies, common-mode noise is primarily suppressed through traditional passive filters (such as LC filters consisting of common-mode chokes and Y-capacitors). However, these solutions are typically bulky and heavy, and struggle to maintain good filtering performance at high frequencies. To address this size issue, active electromagnetic interference filters (AEMI) have been increasingly researched and applied. These filters detect noise and inject an inverted signal to offset the noise source. However, existing AEMI filter structures are often based on analog feedback closed-loop control, relying on high-bandwidth, high-precision sampling and calculations. This leads to complex control, poor stability, and high cost.

[0004] Therefore, there is an urgent need for a novel active EMI filter method suitable for switching power supplies with multiple noise sources. This method, while maintaining excellent suppression performance, reduces system complexity, size, and cost, and exhibits good adaptability and stability, is suitable for these applications. An active EMI filter based on pulse compensation may offer a solution to these challenges. This approach eliminates the noise detection circuit and analyzes the noise characteristics using mathematical modeling. A digital controller then provides a pulse compensation signal synchronized with the power switch. Two MOSFETs are used as independent branches to output the compensation signal, which is then injected into the power circuit. This method, due to its low cost and simple control, holds high research value. Summary of the Invention

[0005] The present invention aims to provide a multi-level pulse compensation active electromagnetic interference filtering method and device suitable for phase-shift control converters, thereby resolving the problems of existing active filters, such as complex structure, poor stability, high cost, and poor compensation effect when processing continuous rising / falling noise edges. To achieve the above objectives, the present invention proposes a multi-level pulse compensation active electromagnetic interference filter, comprising:

[0006] Voltage adaptive circuit, used to automatically adjust the compensation pulse amplitude according to the input voltage change;

[0007] A compensation output circuit, used for outputting a multi-level pulse compensation signal and providing signal isolation;

[0008] The timing control method uses mathematical and circuit models in a controller to calculate the difference between the noise source and the driving timing, ensuring that the compensation signal meets the noise cancellation requirements in terms of phase. To ensure that the cancellation signal and the noise signal have the same amplitude and phase, the error between the signals must be accurately calculated. The compensation signal in this invention uses a pulse compensation circuit. The timing relationship between the compensation signal and the drain-source signal of the switching device is determined by the timing control method and compensated by the controller.

[0009] The waveform compensation circuit adjusts the edge slope of the compensation waveform through a passive circuit network to increase the active cancellation effect of EMI;

[0010] The impedance fitting circuit matches the common mode impedance of the switching power supply through components such as C, L, and R to achieve active EMI cancellation.

[0011] By analyzing the dv / dt characteristics of switching transients in power devices in a switching power supply with multiple noise sources, this paper proposes a multi-level pulse compensation mechanism that effectively addresses the noise coupling caused by continuous rising / falling edges. The compensation signal uses a feedforward structure, generated by the main control chip by calculating delay and slope. This eliminates the need for high-bandwidth current / voltage sampling and complex real-time feedback control, thereby reducing system complexity and cost.

[0012] The beneficial effects of the present invention are as follows: the present invention has strong adaptability and is applicable to various multi-noise source power electronic systems including dual active bridge converters, phase-shifted full-bridge converters, and staggered parallel Buck converters, and has good versatility; the control is simple and stable: no additional controller and high-bandwidth sensor are required, avoiding the closed-loop instability problem existing in traditional active EMI filters; no large-sized passive components and high-precision analog-to-digital conversion modules are required, the overall size is small, the structure is simple, and it is easy to integrate.

[0013] In summary, the multi-level pulse compensation active electromagnetic interference filter solution proposed in the present invention combines suppression performance, control simplicity and system feasibility. It is particularly suitable for power electronic equipment with high requirements on size, cost and electromagnetic compatibility performance, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the multi-level pulse compensation active EMI filter of the present invention and its compensation connection method.

[0015] Figure 2 These are the compensation waveform and noise source waveform of the multi-level pulse compensation active EMI filter of the present invention.

[0016] Figure 3 This is a physical diagram of the multi-level pulse compensation active EMI filter circuit of the present invention.

[0017] Figure 4 This is a comparison diagram of common mode noise of a dual active bridge converter without using a filter and using the multi-level pulse compensation active electromagnetic interference filter proposed in the present invention. DETAILED DESCRIPTION

[0018] The present invention discloses a multi-level pulse compensation active EMI filter suitable for power electronic systems with multiple noise sources. The core idea is to generate corresponding multi-level compensation signals based on the dv / dt characteristics of switching devices in the converter during the turn-on and turn-off processes, and inject them into the common-mode interference path, thereby achieving active suppression of high-frequency electromagnetic interference.

[0019] like Figure 1 As shown, the multi-level pulse compensation active electromagnetic interference filter of the present invention includes the following parts:

[0020] Voltage adaptive circuit: Automatically tracks the input voltage through resistor voltage division, inverse proportional control circuit and buffer amplifier to generate a compensation signal consistent with the amplitude of the noise source. Figure 1 As shown in the figure, in order to make the compensation signal amplitude consistent with the input voltage change, the following circuit is used to achieve automatic adjustment: the input end is connected in series with resistors to form a voltage divider; the divided voltage passes through a buffer amplifier to form a follower output; the inverse proportional amplifier output adjustment signal controls the output amplitude of the driver to meet the goal of automatically tracking the input voltage with the compensation signal amplitude.

[0021] Compensation output circuit: Noise voltage is mainly generated by high dv / dt, that is, the rising and falling edges of the switch drain-source voltage. The multi-noise source switching power supply has multiple continuous rising and falling edges, requiring multiple pulse compensation. Therefore, the present invention designs a multi-level pulse compensation filter design method, which realizes the reverse cancellation of multiple noise sources through multiple levels to output a multi-level pulse compensation signal and provide signal isolation.

[0022] The timing control method uses mathematical and circuit models in the controller to calculate the difference between the noise source and the driving timing, so that the compensation signal meets the noise cancellation requirement in terms of phase. To ensure that the cancellation signal and the noise signal have the same amplitude and phase, the error between the signals must be accurately calculated. In this invention, the compensation signal uses a pulse compensation circuit, which requires analyzing the relationship between the compensation signal and the drain-source signal of the switching tube.

[0023] When the switch device turns off, the delay on the drain-source side of the switch device is mainly due to the Miller platform and V thThe turn-off process can be simplified into two parts: first, the gate signal is set to zero, and the C gs The voltage starts to decrease, at this time, the V gs The voltage is still greater than the Miller platform voltage of the switch tube at this time, so the switch tube continues to work in the ohmic region. ds will not increase until V gs Reduce to V M , so the compensation signal should lag behind the driving signal.

[0024] When the switch device is turned on, since most multi-noise source switching power supplies use a soft-switching topology, the drop in drain-source voltage when the switch is turned on is not determined by the switch drive signal. Instead, the voltage drops to 0 during the dead zone. Therefore, the filter compensation signal needs to be ahead of the drive signal. When the upper tube is turned off, the parasitic capacitance of the lower tube begins to discharge. That is, the early turn-on time of the compensation signal is the dead zone time minus the turn-on delay of the upper tube.

[0025] For the waveform compensation circuit, in the rising process, the switching device works in the saturation region at this stage, and V ds Continue to rise until it reaches V in During the opening process, V ds Voltage drop, C oss The discharge circuit and the shutdown process V ds Voltage rise, C oss The charging circuit is the same, and the voltage drop slope can be considered to be the inverse of the rising slope. The change of the drain-source signal is approximately linear, so the linear fitting method can be directly used for configuration. By calculating the passive circuit network, the edge slope of the compensation waveform is adjusted to increase the active EMI cancellation effect.

[0026] The impedance fitting circuit is composed of the devices in the common-mode path obtained by analysis, and is composed of L, R, C and equivalent devices existing in other paths. The value of the device is a multiple of the impedance of the corresponding device in the common-mode path.

[0027] The compensation signal control logic is implemented by a controller, which can be shared with the switching power supply's controller or added separately. The main control chip determines the phase polarity of the compensation signal based on the current operating mode. The control logic automatically inserts a delay or advance time for the compensation signal. Using the filter's application in an isolated bidirectional full-bridge converter as an example, the control logic for filtering multiple noise sources on the primary side is shown in Table 1, and the control logic for filtering multiple noise sources on the secondary side is shown in Table 2. The first and second compensation output circuits in the compensation output circuit are sequentially turned on to output a multi-level waveform. This control logic eliminates the need for a complex closed-loop error amplifier, thus avoiding the stability issues associated with traditional active EMI filters.

[0028] Table 1

[0029]

[0030] Table 2

[0031]

[0032] The present invention was verified on a 48V-48V 1kW DAB converter with a switching frequency of 136kHz. The EMI spectrum measured in the experiment is as follows: Figure 4 The dashed line represents common-mode noise without a filter, while the solid line represents common-mode noise with the filter described in this patent. The results demonstrate that the compensation signal accurately tracks the dv / dt characteristics of the noise source. Under the MIL-STD-461E-CE102 standard, the filter achieves better than 20dBμV of suppression at low frequencies and a 3-6dBμV reduction at high frequencies.

[0033] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the appended claims.

[0034] The above embodiments are intended only to illustrate the technical solutions of the present application and are not intended to limit them. The present application is not limited to the precise structures described above and illustrated in the accompanying drawings, and it cannot be assumed that the specific implementation of the present application is limited to these descriptions. For those skilled in the art of the present application, any changes and modifications made without departing from the concept of the present application should be deemed to fall within the scope of protection of the present application.

Claims

1. A multi-level pulse compensation active electromagnetic interference filter suitable for multi-noise source converters, The invention is characterized by: a voltage adaptive circuit (1), which is composed of a voltage dividing resistor (101), a sampling resistor (103), a first operational amplifier (102), and a second operational amplifier (104), and is used to automatically adjust the compensation pulse amplitude according to the input voltage change; a pulse compensation circuit (2), which is composed of a controller (201), a first compensation output circuit (202), a second compensation output circuit (203), a waveform compensation circuit (205), and an impedance fitting circuit (204), and is used to generate a compensation signal that matches the dv / dt characteristic of the noise source according to the drive signal of the converter main circuit; and a timing control method, which calculates the difference between the noise source and the drive timing in the controller through a mathematical model and a circuit model, so that the compensation signal meets the noise cancellation requirement in terms of phase. The first compensation output circuit and the second compensation output circuit are both composed of a totem pole output drive circuit (2021) and an electrical isolation module (2022), and are used to output a multi-level pulse compensation signal and provide signal isolation; a waveform compensation circuit, which adjusts the edge slope of the compensation waveform through a passive circuit network to increase the active cancellation effect of EMI; and an impedance fitting circuit, which matches the common mode impedance of the switching power supply through devices such as C, L, and R to achieve active cancellation of EMI.

2. The filter according to claim 1, wherein The injection network is connected between a power ground PG and a protection ground PE of the power supply system.

3. The filter according to claim 1 or 2, characterized in that The compensation signal is a multi-level pulse signal. The circuit consists of two compensation output circuits, wherein the power supply end of the second compensation output circuit is connected to the output end of the first compensation output circuit. Multi-level is achieved by controlling the conduction of the totem pole circuit. The output end of the second compensation output circuit is connected to the protective ground, and the compensation signal is injected into the protective ground.

4. The filter according to any one of claims 1 to 3, characterized in that The timing control method calculates the compensation delay time during the power device's on and off process using the instantaneous current value of the switching power supply and the parasitic parameters of the switching device. The calculation is performed by the controller and the first formula is obtained.

5. The timing control method according to claim 4, characterized in that: The first formula is: Among them, V H is the high level of the driving voltage, R g is the driving resistance, L g To drive the parasitic inductance, C iss is the input capacitance of the switching device, V Ciss is the voltage of the input capacitor of the switching device, S1 and S2 are parameters calculated according to the driving circuit.

6. The filter according to any one of claims 1 to 5, characterized in that: The waveform compensation circuit adjusts the waveform of the compensation signal through a passive device network, wherein L and R adjust the amplitude of the ringing, C and L adjust the frequency of the ringing, and R and C adjust the slope of the rising and falling edges. Its structure includes but is not limited to a waveform compensation circuit (205), a waveform compensation circuit 2 (2051) and a waveform compensation circuit 3 (2052).

7. The filter according to any one of claims 1 to 6, characterized in that: The impedance fitting circuit is composed of devices in the common mode path obtained by analysis, and is composed of L, R, C and equivalent devices existing in other paths. The value of the device is a multiple of the impedance of the corresponding device in the common mode path. Its structure includes but is not limited to the impedance fitting circuit (204), impedance fitting circuit 2 (2041) and impedance fitting circuit 3 (2042).

8. The filter according to any one of claims 1 to 7, characterized in that: A method for automatically adjusting the compensation pulse amplitude according to the input voltage change is provided by obtaining a multiple of the input voltage through a sampling resistor and forming a positive phase proportional circuit and a negative phase proportional circuit through a resistor and a buffer amplifier.

9. The filter according to any one of claims 1 to 8, characterized in that: When the filter is applied to an isolated bidirectional full-bridge converter, the control logic shown in Table 1 is applicable to primary-side multi-noise source filtering, and the control logic shown in Table 2 is applicable to secondary-side multi-noise source filtering. The table 1 is: The table 2 is:

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