A wideband active EMI filter circuit and a control method thereof

Abstract

The application discloses a wideband active EMI filter circuit and a control method thereof, which comprises a high-frequency common-mode inductance module, an amplification filter module and a differential-mode filter module, the high-frequency common-mode inductance module further comprises two sampling signal output ports, and the sampling common-mode noise is connected to two input ports of the amplification filter module respectively after sampling; the output port of the amplification filter module is connected to the differential-mode filter module, and the differential-mode noise is filtered in the differential-mode filter module after the loop noise current is eliminated. Through the wideband active EMI filter circuit and the control method thereof, the compensation current signal is obtained through a novel sampling mode, the novel sampling mode is adopted, the purpose of wideband filtering is achieved, the stability of the filter is improved, meanwhile, the filter is small in size, wide in frequency band, high in stability, applicable to various space-limited scenes such as aerospace and industrial application, and the hardware design can make the matched product meet the electromagnetic compatibility requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic compatibility, and in particular to a wideband active EMI filter circuit and a control method thereof. BACKGROUND

[0002] In 1971, H. Sasaki and T. Machida of Japan proposed the concept of active filtering. That is, by injecting a compensation current equal in size and opposite in direction to the original noise current into the power supply side of the interference device, the noise current on the power supply side is zero, so that the product meets the electromagnetic compatibility requirements. Compared with passive filters, active filters have the advantage of small size, and can solve the problem of impedance mismatch of passive filters.

[0003] Foreign countries started early research on active filters, and achieved considerable research results. Domestic research followed, and now the sales of domestic active filters have far exceeded imported brands. However, the current research on active filters at home and abroad is concentrated in the APF field, and the research on electromagnetic interference active filters is less. The market demand for electromagnetic interference filters is increasing, and the requirement for the size of the filter is increasingly demanding, and the impedance adaptation problem has become a difficulty in filter design. SUMMARY

[0004] To solve the above problems, based on the research on electromagnetic compatibility technology, a wideband active EMI filter circuit and a control method thereof are proposed.

[0005] In a first aspect, a wideband active EMI filter circuit includes a high-frequency common-mode inductor module, an amplification filter module, and a differential-mode filter module. The high-frequency common-mode inductor module further includes two sampling signal output ports, which are respectively connected to two input ports of the amplification filter module after sampling common-mode noise. The output port of the amplification filter module is connected to the differential-mode filter module, and the differential-mode filter module is input after eliminating the loop noise current to filter the differential-mode noise.

[0006] Specifically, the high-frequency common-mode inductor module includes a high-frequency common-mode inductor one connected to a signal input port and a high-frequency common-mode inductor two connected in series with the high-frequency common-mode inductor one. The high-frequency common-mode inductor one and the high-frequency common-mode inductor two are respectively connected in parallel with a bias resistor. The high-frequency common-mode inductor one and the high-frequency common-mode inductor two output circuits are further provided with a resistor, and two output circuits are respectively connected to two input ports of the amplification filter circuit.

[0007] Specifically, the high-frequency common-mode inductor one and the high-frequency common-mode inductor two are high-frequency common-mode inductors with sensing coils, which sample the common-mode noise after filtering the high-frequency common-mode noise in the loop.

[0008] Specifically, the high-frequency common-mode inductor one and the high-frequency common-mode inductor two sampling coils and the common-mode coils are all anodes, and the induced coils sample the noise signals i+ and i- in the same current direction.

[0009] Specifically, the amplification and filtering module further comprises two amplifier sub-modules, each of which further comprises two signal amplifiers, a bias resistor connected in parallel between the output terminals of the signal amplifier one and the signal amplifier two, a high-frequency noise filtering sub-module and a medium and low noise filtering sub-module arranged between the two amplifiers, and the two amplifier sub-modules are respectively connected to the active filter circuit switch after processing the sampling signal noise and connected to the differential mode filtering module input end.

[0010] Specifically, the differential mode filtering module comprises a differential mode filtering sub-module composed of an inductor and two filtering capacitors, and the differential mode filtering sub-module is further connected to a signal output end.

[0011] On the other hand, a wideband active EMI filter circuit control method is based on a wideband active EMI filter circuit, comprising:

[0012] The high-frequency common-mode inductor filters the high-frequency common-mode noise in the power loop, and the induced coil samples the common-mode noise, and the sampling signal enters the input end of the signal amplifier one of the amplification and filtering module;

[0013] After the signal amplifier one amplifies the signal, the high-frequency noise is filtered by the high-frequency noise filtering sub-module, and the medium and low noise is filtered by the medium and low noise filtering sub-module, and then the current is injected into the power loop by the active filter circuit switch;

[0014] The induced coil of the high-frequency common-mode inductor samples the signal, so that the current injected into the power loop is equal in size and opposite in direction to the noise current on the power loop, and the noise current on the power loop is eliminated.

[0015] Further, the signal amplifier one samples the injected signal and returns to the input end of the signal amplifier two to form a feedback loop, and the oscillation generated by the injected signal is suppressed.

[0016] Further, when the input is inverted, the active filter circuit switch turns off the active filter circuit.

[0017] The beneficial effects of the present application: the present application proposes a wideband active EMI filter circuit control method, proposes a new type of active filter circuit, the filter circuit is characterized in that a new type of sampling method is used to obtain a compensation current signal, the compensation current is injected into the backflow end of the power bus through a resistor capacitor, a new sampling method is adopted, a new current sensor is designed according to the new sampling method, and two current sensors are connected in parallel to realize the purpose of wideband filtering, and a follower is added at the output end of the operational amplifier, then negative feedback is performed, so as to improve the stability of the filter, and the filter is small in size, wide in frequency band, high in stability, suitable for various space-limited scenes such as aerospace and industrial applications, and the hardware design can make the matching products meet the electromagnetic compatibility requirements. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a wideband active filter topology circuit diagram of the present application;

[0019] Figure 2 is a principle diagram of the active filter of the present application;

[0020] Figure 3 is a schematic diagram of the active topology network model of the present application;

[0021] Figure 4 is a principle diagram of the current transformer (high-frequency common-mode inductor) of the present application. DETAILED DESCRIPTION

[0022] In order to have a clearer understanding of the technical features, objects and effects of the present application, the specific embodiments of the present application will be described with reference to the drawings.

[0023] The present application proposes a wideband active EMI filter circuit and a control method thereof, as shown in Figure 1As shown, the first aspect, the first aspect, a wideband active EMI filter circuit, including high frequency common mode inductance module, amplification filter module and differential mode filter module, the high frequency common mode inductance module further comprises two sampling signal output ports, sampling common mode noise is connected to the two input ports of amplification filter module respectively; The output port of the amplification filter module is connected to the differential mode filter module, and the differential mode noise is filtered after the loop noise current is input into the differential mode filter module. The high frequency common mode inductance module comprises high frequency common mode inductance one connected with signal input port and high frequency common mode inductance two connected with high frequency common mode inductance one in series, the high frequency common mode inductance one and the high frequency common mode inductance two are further respectively connected with one bias resistor, and the high frequency common mode inductance one and the high frequency common mode inductance two output circuit are further provided with resistors, and two output circuits are connected with two input ports of amplification filter circuit respectively. The high frequency common mode inductance one and the high frequency common mode inductance two are all high frequency common mode inductance with sensing coil, and the common mode noise is sampled after the high frequency common mode noise in the loop is filtered. The sampling coil and the common mode coil of the high frequency common mode inductance one and the high frequency common mode inductance two with sensing coil are all homonymous ends, and the current direction of the noise signals i+, i- sampled from the two common mode coils is same. The amplification filter module further comprises two amplifier submodules, each amplifier submodule further comprises two signal amplifiers, one bias resistor is connected between the output ends of signal amplifier one and signal amplifier two, high frequency noise filtering submodule and low noise filtering submodule are further arranged between the two amplifiers, and the two amplifier submodules are connected to active filter circuit switch and differential mode filter module input end after processing sampling signal noise. The differential mode filter module comprises differential mode filter submodule composed of inductance and two filter capacitors, and the differential mode filter submodule is further connected with signal output end.

[0024] A wideband active EMI filter circuit control method based on a wideband active EMI filter circuit, comprising:

[0025] The high frequency common mode inductance filters the high frequency common mode noise in the power loop, the sensing coil samples the common mode noise, and the sampling signal enters the input end of signal amplifier one of the amplification filter module;

[0026] After the signal amplifier one amplifies the signal, the high frequency noise is filtered through the high frequency noise filtering submodule, the low noise is filtered through the low noise filtering submodule, and the current injected into the power loop is injected into the power loop through the active filter circuit switch;

[0027] The sensing coil sampling signal of the high frequency common mode inductance is conditioned, so that the current injected into the power loop is equal in size and opposite in direction to the noise current on the power loop, and the noise current on the power loop is eliminated. Further comprising: signal amplifier one samples the injected signal and returns to the input end of signal amplifier two to form a feedback loop, and suppresses the oscillation generated by the injected signal. Further comprising: when the input is inverted, the active filter circuit switch turns off the active filter circuit.

[0028] In this invention, the active filter circuit is as follows: Figure 2 As shown, in this filter, inductor L3 is a high-frequency common-mode inductor with a sensing coil. This common-mode inductor can filter out high-frequency common-mode noise in the power circuit. Its sensing coil can sample common-mode noise. The sampled signal enters the input terminal of U2, and after being amplified by U2, the high-frequency noise is filtered out by the RC filter circuit composed of R10 and C7. The medium and low noise is injected into the power circuit through R11, C6, and switch S1. The sampling signal of the sensing coil is conditioned so that the current injected into the power circuit is equal in magnitude and opposite in direction to the noise current in the power circuit, thereby extinguishing the noise current in the power circuit. Figure 1 In the process, after the negative line common-mode noise is filtered out, the positive line common-mode noise is converted into differential-mode noise, which is then filtered out by the differential-mode filter circuit composed of L1, C2, and C3. The sampled injection signal from U1 is returned to the input of U2, forming a feedback loop that can suppress the oscillations generated by the injected signal. S1 is the switch of the active filter circuit; when the input is inverted, the active filter circuit can be turned off.

[0029] This active filter circuit is a feedforward circuit that samples the signal at the power supply end. The circuit topology requires that the injected current be equal to the noise current on the bus. For example... Figure 3 As shown, this requires In - Ic = Iq = 0. In reality, Iq cannot reach zero; its closed-loop current transfer function is Iq = In / (1+F). Therefore, to achieve a filtering effect close to the ideal value, the gain of the differential-mode amplifier should be as large as possible. However, excessive gain can easily cause system oscillations and reduce stability; at high frequencies, the gain should not be too high either. To improve system stability, a follower U1 is added to this design. Appropriately selecting the parameter value of R12 according to the filtering frequency band is also crucial for designing filters for different noise frequency bands.

[0030] In this embodiment, L3 is a current transformer, which can not only filter out high-frequency common-mode noise, but also sample noise signals for active filtering. Figure 4 As shown, in this design, the sampling coil and the common-mode coil are opposite terminals. The noise signals i+ and i- sampled by the induction coil from the two common-mode coils have the same current direction. Compared to single-wire sampling from the positive and negative lines, this design doubles the sampling signal strength. This design can reduce the number of turns in the primary and secondary coils, reduce parasitic parameters during high-frequency sampling, and the minimum number of turns on the primary side can be as low as 1 turn.

[0031] In this embodiment, the filter achieves wideband filtering by connecting two active filter circuits in parallel. Figure 4 The lower cutoff frequency of the medium current transformer is:

[0032]

[0033] In the formula, A e Is the effective section area of the magnetic core; l is the effective magnetic flux length; mu r Is the relative magnetic permeability.

[0034] The upper limit cutoff frequency is:

[0035]

[0036] In the formula, c` is the parasitic capacitance, L` is the leakage inductance, and L`` is the parasitic inductance.

[0037] As can be seen from formula (1), the lower limit cutoff frequency f L Of the current transformer is determined by the effective section area A e Of the magnetic core, the effective magnetic circuit length l and the magnetic core material; as can be seen from formula (2), the upper limit frequency of the current transformer is determined by the parasitic parameters. Figure 1 As can be seen from formula (1) and formula (2), the cutoff frequency of the current transformer with fixed parameters is also fixed. To widen the lower limit cutoff frequency, the winding needs to be increased, and the parasitic parameters generated by the winding reduce the upper limit cutoff frequency.

[0038] The present application provides a wideband active EMI filter circuit control method, which can be used in the power supply of a blade in a communication computer, a power supply of a telecommunication base station, a distributed power supply, a network switch and a router, and a power supply system of a wireless communication base station.

[0039] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A broadband active EMI filter circuit, characterized in that, The system includes a high-frequency common-mode inductor module, an amplification and filtering module, and a differential-mode filtering module. The high-frequency common-mode inductor module also includes two sampling signal output ports, which are connected to the two input ports of the amplification and filtering module after sampling common-mode noise. The output port of the amplification and filtering module is connected to the differential-mode filtering module, and after eliminating loop noise current, it is input to the differential-mode filtering module for differential-mode noise filtering. The high-frequency common-mode inductor module includes a high-frequency common-mode inductor I connected to the signal input port and a high-frequency common-mode inductor II connected in series with the high-frequency common-mode inductor I. The high-frequency common-mode inductor I and the high-frequency common-mode inductor II are also connected in parallel with a bias resistor. The output circuits of the high-frequency common-mode inductor I and the high-frequency common-mode inductor II are also equipped with resistors. The two output circuits are respectively connected to the two input ports of the amplification and filtering circuit. Both the high-frequency common-mode inductor one and the high-frequency common-mode inductor two are high-frequency common-mode inductors with sensing coils. After filtering out the high-frequency common-mode noise in the circuit, the common-mode noise is sampled. The sampling coils of the high-frequency common-mode inductor one and the high-frequency common-mode inductor two with sensing coils are opposite to the common-mode coils. The noise signals i+ and i- sampled by the induction coils from the two common-mode coils have the same current direction.

2. The broadband active EMI filter circuit according to claim 1, characterized in that, The amplification and filtering module also includes two amplifier sub-modules. Each amplifier sub-module includes two signal amplifiers. A bias resistor is connected in parallel between the output terminals of signal amplifier one and signal amplifier two. A high-frequency noise filtering sub-module and a medium-low noise filtering sub-module are also provided between the two amplifiers. After processing the noise of the sampled signal, the two amplifier sub-modules are respectively connected to the active filter circuit switch and connected to the input terminal of the differential mode filter module.

3. The broadband active EMI filter circuit according to claim 1, characterized in that, The differential mode filtering module includes a differential mode filtering sub-module consisting of an inductor and two filtering capacitors, and the differential mode filtering sub-module is also connected to the signal output terminal.

4. A method for controlling a broadband active EMI filter circuit, implemented based on a broadband active EMI filter circuit according to any one of claims 1 to 3, characterized in that, include: The high-frequency common-mode inductor filters out high-frequency common-mode noise in the power circuit. Its induction coil samples the common-mode noise, and the sampled signal enters the input terminal of the signal amplifier of the amplification and filtering module. After the signal amplifier amplifies the signal, high-frequency noise is filtered out by the high-frequency noise filtering submodule, and medium- and low-frequency noise is filtered out by the medium- and low-frequency noise filtering submodule and then injected into the power circuit by the active filter circuit switch. The sampling signal of the high-frequency common-mode inductor is conditioned so that the current injected into the power circuit is equal in magnitude and opposite in direction to the noise current in the power circuit, thereby eliminating the noise current in the power circuit.

5. The broadband active EMI filter circuit control method according to claim 4, characterized in that, Also includes: The input signal is sampled by signal amplifier one and returned to the input terminal of signal amplifier two to form a feedback loop, which suppresses the oscillation generated by the injected signal.

6. The broadband active EMI filter circuit control method according to claim 4, characterized in that, Also includes: When the input is inverted, the active filter circuit switches off.

Images