WO2017211104A1

WO2017211104A1 - Emi filter and power emi filter access circuit

Info

Publication number: WO2017211104A1
Application number: PCT/CN2017/076742
Authority: WO
Inventors: 戴彪; 宋爱; 程海松
Original assignee: 珠海格力电器股份有限公司
Priority date: 2016-06-08
Filing date: 2017-03-15
Publication date: 2017-12-14
Also published as: CN107482896A

Abstract

An EMI filter and a power EMI filter access circuit. The EMI filter comprises a tunable common mode inductor (L1), a first and a second differential-mode working capacitor (CX) that are connected in parallel with an input end and an out end of the tunable common mode inductor respectively, a tunable differential-mode inductor (L2) whose input end is connected in series with the output end of the tunable common mode inductor, and a first and a second common mode working capacitor (CY) that are connected in series with the input end of the tunable differential-mode inductor. The EMI filter can provide a relatively high insertion loss within a conducted interference frequency range, so as to attenuate the EMI signal to the maximum degree, thus making the device meet an electromagnetic standard, and effectively improving the filtering effect.

Description

EMI filter and power EMI filter access circuit

Technical field

This application claims the priority of the domestic application filed on June 8, 2016, the Chinese Patent Office, the application number 201610398464.1, the invention name is "EMI filter and power EMI filter access circuit", the entire contents of which are incorporated by reference. In this application.

Background technique

With the widespread use of electronic products and converters related to power electronics, Electromagnetic Interference (EMI) has become increasingly serious and has become a public hazard. Conducted interference from air conditioners can be reduced to the requirements of the EMC standard by EMI power filters. The insertion loss of the EMI filter is directly related to the source impedance and the load impedance. Therefore, even if the insertion loss design value of the EMI filter can reach the standard, if the EMI filter is used improperly, it may be due to changes in the source impedance and the load impedance. The best filtering effect is not obtained.

In response to the above problems, no effective solution has been proposed yet.

Summary of the invention

An embodiment of the present invention provides an EMI filter for improving a filtering effect, where the EMI filter includes:

The adjustable common mode inductor; the first differential mode working capacitor is connected in parallel with the input end of the adjustable common mode inductor; the second differential mode working capacitor is connected in parallel with the output end of the adjustable common mode inductor; the adjustable differential mode An inductor, the input end is connected in series with an output end of the adjustable common mode inductor; a first common mode working capacitor and a second common mode working capacitor are connected in series with an input end of the adjustable differential mode inductor, the first common mode The working capacitor and the second common mode working capacitor form a parallel structure with each other; wherein the first differential mode working capacitor and the second differential mode working capacitor and the adjustable differential mode inductor form a second-order LC filter Device.

In one embodiment, the EMI filter further includes: a bleeder resistor connected in parallel between the output of the adjustable common mode inductor and the input of the adjustable differential mode inductor.

In one embodiment, the EMI filter further includes: a controller, and the EMI An input port of the filter is connected to an output port of the EMI filter for sampling a voltage current signal of the EMI filter input port and a voltage current signal of the output port, and according to the voltage current signal and the output of the input port The voltage and current signals of the port calculate a source impedance and a load impedance, and the inductance values of the adjustable common mode inductance and the adjustable differential mode inductance are determined according to the source impedance and the load impedance.

In one embodiment, the core of the adjustable common mode inductor is a tubular structure, and the core of the adjustable differential mode inductor is a tubular structure.

In one embodiment, the adjustable common mode inductor is wound with an AC control winding along the inside and outside of the tubular core, and a DC main winding is wound around the outside of the tubular core, wherein the AC and DC windings and the corresponding AC and DC flux are orthogonal to each other. .

In one embodiment, the adjustable differential mode inductor is wound with a DC control winding along the inside and outside of the tubular core, and an AC main winding is surrounded along the outside of the tubular core, wherein the AC-DC winding and the corresponding AC-DC flux are orthogonal to each other. .

An embodiment of the present invention further provides a power EMI filter access circuit, the circuit comprising: a power source; a source impedance connected in series with the power source; and the EMI filter, the input port is connected in parallel with the power source and the source impedance Structure; load impedance, forming a parallel structure with an output port of the EMI filter.

In the above embodiment, two parameters adjustable inductors are provided in the EMI filter, and a common-mode working capacitor and a differential mode working capacitor are combined to form a power EMI two-stage filter, because the parameters of the inductor are adjustable, The inductance parameter can be adjusted according to actual needs, so that the EMI filter can provide higher insertion loss in the conducted interference frequency range, so as to minimize the EMI signal, so that the electromagnetic of the device can meet the standard and effectively improve the filtering effect. .

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a circuit diagram of an EMI filter in accordance with an embodiment of the present invention;

2 is a circuit diagram of a power EMI filter access circuit according to an embodiment of the present invention;

3 is a schematic circuit diagram of an EMI filter according to an embodiment of the present invention;

4 is a schematic diagram of an electromagnetic structure of an adjustable common mode inductor according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an electromagnetic structure of an adjustable differential mode inductor according to an embodiment of the invention.

detailed description

In order to make the objects, technical solutions and advantages of the present invention more comprehensible, the present invention will be further described in detail with reference to the embodiments and drawings. The illustrative embodiments of the present invention and the description thereof are intended to explain the present invention, but are not intended to limit the invention.

Considering that the parameters of each device of the conventional air conditioner power EMI filter are fixed, due to changes in source impedance and load impedance, a good filtering effect is often not obtained. To this end, an EMI filter is provided in the embodiment of the present invention. As shown in FIG. 1, the method may include:

The adjustable common mode inductor L1; the differential mode working capacitor CX is connected in parallel with the input end of the adjustable common mode inductor L1; the common mode working capacitor CY and the adjustable differential mode inductor L2 form an LC second order filter; the adjustable differential mode inductor L2, The input end is connected in series with the output end of the adjustable common mode inductor L1; the differential mode working capacitor CX is connected in series in the loop to eliminate the differential mode signal common mode working capacitor CY directly grounded, eliminating the common mode signal,

In the above embodiment, two parameters adjustable inductors are provided in the EMI filter, and a common-mode working capacitor and a differential mode working capacitor are combined to form a power EMI two-stage filter, because the parameters of the inductor are adjustable, The inductance parameters can be adjusted according to actual needs, so that the EMI filter can provide high insertion loss in the conducted interference frequency range, so as to minimize the EMI signal, so that the electromagnetic of the device can meet the standard.

As shown in FIG. 1 , the EMI filter may further include: a bleeder resistor R connected in parallel between the output end of the adjustable common mode inductor and the input end of the adjustable differential mode inductor, and the resistance of R is relatively high. When not working, R quickly vents the amount of electricity stored in the CX to avoid shocking the operator.

In order to adjust the inductance value of the adjustable inductor, a controller may be disposed in the EMI filter, and the controller is connected to the input port of the EMI filter and the output port of the EMI filter for sampling the EMI filter input. Voltage and current signals of the port and voltage of the output port The signal is flowed, and the source impedance and the load impedance are calculated according to the voltage current signal of the input port and the voltage current signal of the output port, and the inductance values of the adjustable common mode inductor and the adjustable differential mode inductor are determined according to the source impedance and the load impedance.

Specifically, the iron core of the adjustable common mode inductor L1 may be a tubular structure, and the iron core of the adjustable differential mode inductor L2 may be a tubular structure, and the adjustable common mode inductor is wound around the inner and outer sides of the tubular iron core with an AC control winding. The tubular core is surrounded by a DC main winding, wherein the AC-DC winding and the corresponding AC-DC flux are orthogonal to each other. The adjustable differential mode inductor has a DC control winding wound around the inside and outside of the tubular core, and an AC main winding is arranged around the tubular core, wherein the AC-DC winding and the corresponding AC-DC flux are orthogonal to each other.

The EMI filter is further provided in the embodiment of the present invention, and further provides a power EMI filter access circuit, the circuit includes: a power source; a source impedance, connected in series with the power source; an EMI filter, an input port, and the power source and the The source impedance forms a parallel structure; the load impedance forms a parallel structure with the output port of the EMI filter.

That is, a parameter-adjustable single-phase power EMI filter control method is proposed. The source impedance and the load impedance are calculated by detecting the input and output voltage and current signals, and then the EMI filter two-port impedance is matched to provide within the conducted interference frequency range. Higher insertion loss maximizes EMI signal attenuation.

The EMI filter and the power EMI filter access circuit are described below in conjunction with a specific embodiment. However, it is to be noted that the specific embodiment is only for better explanation of the present invention and does not constitute an undue limitation of the present invention. .

Considering that the purpose of accessing the EMI filter in the circuit is to insert an impedance transfer network between the interference source and the sensitive device, it can make the useful signal pass smoothly, limit the passage of useless EMI signals, and thus the energy of the EMI signal transmitted along the line. Attenuated to a minimum. Insertion loss is an important indicator to measure the performance of an EMI filter. It is the ratio of the power delivered by the source to the load when the filter is not connected to the line and after the line is connected.

For a circuit with a source impedance ZS and a load impedance ZL, if an external two-port network with a port characteristic impedance ZC1 and ZC2 equal to the source internal resistance ZS and the load impedance ZL, respectively, is connected between the source and the negative cut as shown in FIG. , at this time, the two-port network only acts as a matching impedance, and the source can The power supplied will be fully absorbed by the load.

As shown in Figure 3, the circuit of the filter is a passive network, which has reciprocity, connecting the load to the filtered power supply terminal (Lin terminal and Nin terminal), or to the load terminal (Lout terminal and Nout terminal). In principle, it is possible, especially when the internal resistance of the power supply (source impedance) is equal to the load resistance (load impedance), and the insertion loss measured by this interchangeability is also equal. Figure 3 shows the topology topology of the EMI filter with adjustable parameters. The power EMI filter is composed of a common mode filter circuit and a differential mode filter circuit. L1 is a common mode choke and L2 is a differential mode. Choke, CX is the differential mode working capacitor, CY is the common mode working capacitor, R is the bleeder resistance (higher resistance), when not working, R quickly vents the amount of electricity stored in CX to avoid electric shock operation. personnel.

Figure 4 shows the electromagnetic structure of the adjustable common mode inductor. Figure 5 shows the electromagnetic structure of the adjustable differential mode inductor. The iron core adopts a tubular structure. The adjustable differential mode inductor is wound around the inside and outside of the tubular core. The DC control winding is surrounded by an AC main winding outside the tubular iron core, and the adjustable common mode inductor is wound around the tubular iron core with an AC control winding, and a DC main winding is arranged around the tubular iron core, and the AC and DC windings and their corresponding The AC and DC magnetic fluxes are orthogonal to each other. Therefore, the AC-DC flux does not affect each other, and the DC current does not affect the linear characteristics of the reactor. In addition, the DC magnetic circuit is a closed core structure, and the DC power required to generate a strong DC control magnetic field is small, and the stronger the transverse DC magnetic field, the lower the longitudinal magnetic permeability. From the energy point of view, the presence of the transverse DC magnetic field increases the anisotropy energy of the core, thereby suppressing the magnetic permeability of the core. In the case of a tunable inductor, the core has the highest magnetic permeability and the largest inductance in the absence of a superimposed DC magnetic field. As the DC magnetic field increases, the magnetic permeability of the core in the direction of the alternating magnetic field decreases, and thus the inductance of the inductor decreases.

The insertion loss of the EMI filter is directly related to the source impedance and the load impedance. Therefore, even if the insertion loss design value of the EMI filter is up to standard, if it is used improperly, it may not be optimal due to changes in source impedance and load impedance. The filtering effect makes it possible to gain the EMI signal even because resonance occurs. In this example, the sampling filter input port and the output port voltage and current signals are input into the MCU to calculate the corresponding source impedance and load impedance. The MCU controls the DC power output through the PWM signal, thereby changing the inductance value of the adjustable inductor. Achieve dynamic matching of impedance.

Another simple algorithm in voltammetry is used to design the RLC digital bridge, ie Knowing the voltage across the device under test and the current flowing through the test component, the impedance of the component under test can be determined, and since the standard resistance is known, the voltage across the standard resistor can be measured. The relationship between the voltage across the measured impedance and the voltage across the standard impedance is:

Z _x =U _x /I _x =U _x /U _s R _s

Applying the above EMI filter to the air conditioner power supply, when the power of the air conditioner compressor changes, thereby ensuring the maximum mismatch of the impedance, the filter network actually operates with both large insertion loss and maximum reflection. Loss, thereby achieving effective suppression of EMI signals.

From the above description, it can be seen that the embodiment of the present invention achieves the following technical effects: two parameters adjustable inductors are set in the EMI filter, and a common mode working capacitor and a differential mode working capacitor are combined to form a power supply EMI. Stage filter, because the parameters of the inductor are adjustable, the inductance parameters can be adjusted according to actual needs, so that the EMI filter can provide high insertion loss in the conducted interference frequency range to maximize EMI attenuation. The signal makes the electromagnetic of the device meet the standard.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various changes and modifications may be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

An EMI filter characterized by comprising:

Adjustable common mode inductor;

a first differential mode working capacitor connected in parallel with an input end of the adjustable common mode inductor;

a second differential mode working capacitor connected in parallel with an output of the adjustable common mode inductor;

An adjustable differential mode inductor, the input end being connected in series with the output end of the adjustable common mode inductor;

a first common mode working capacitor and a second common mode working capacitor are connected in series with an input end of the adjustable differential mode inductor, and the first common mode working capacitor and the second common mode working capacitor form a parallel structure with each other ;

The first differential mode working capacitor and the second differential mode working capacitor and the adjustable differential mode inductor form a second-order LC filter.
The EMI filter of claim 1 further comprising: a bleeder resistor coupled in parallel between the output of said tunable common mode inductor and the input of said tunable differential mode inductor.
The EMI filter of claim 1 further comprising:

a controller, connected to an input port of the EMI filter and an output port of the EMI filter, for sampling a voltage current signal of the EMI filter input port and a voltage current signal of the output port, and according to the input The voltage current signal of the port and the voltage current signal of the output port calculate a source impedance and a load impedance, and the inductance values of the adjustable common mode inductor and the adjustable differential mode inductor are determined according to the source impedance and the load impedance.
The EMI filter according to any one of claims 1 to 3, wherein the core of the adjustable common mode inductor is a tubular structure, and the core of the adjustable differential mode inductor is a tubular structure.
The EMI filter according to claim 4, wherein the adjustable common mode inductor is wound with an AC control winding inside and outside the tubular core, and a DC main winding is surrounded around the tubular core, wherein the AC and DC windings are The corresponding AC and DC magnetic fluxes are orthogonal to each other.
The EMI filter according to claim 4, wherein the adjustable differential mode inductor has a DC control winding wound around the inside and outside of the tubular core, and an AC main winding is arranged around the outside of the tubular core. Wherein, the AC-DC winding and the corresponding AC-DC flux are orthogonal to each other.
A power EMI filter access circuit, comprising:

power supply;

Source impedance, in series with the power source;

The EMI filter according to any one of claims 1 to 6, wherein the input port forms a parallel structure with the power source and the source impedance;

The load impedance forms a parallel structure with the output port of the EMI filter.
The power EMI filter access circuit according to claim 7, wherein the power source is an air conditioner power source.