CN102982968A - Planar integrated EMI (electro magnetic interference) choking coil for planar EMI filter - Google Patents

Abstract

The invention relates to a planar integrated EMI choking coil for a planar EMI filter. The planar integrated EMI choking coil comprises a pair of EDT magnetic cores, an outer magnetic ring formed by a pair of I-shaped magnetic cores opposite to each other, and an inner magnetic ring arranged between the EDT magnetic cores and the I-shaped magnetic cores, wherein the inner magnetic ring comprises two PCBs (Printed Circuit Board) which are opposite to each other, and are provided with two ends being in symmetrical ring shapes; ring-shaped through holes are respectively arranged on ring-shaped parts on two ends of a base plate of each PCB; and a protruded piece is arranged on an inner wall of each EDT magnetic core, and sequentially penetrates through the ring-shaped through holes on the two PCBs opposite to the protruded pieces. According to the planar integrated EMI choking coil for the planar EMI filter, the integration of a difference mode inductor and a common mode inductor is realized through two magnetic cores with different magnetic conductivities, independent adjustment of the difference mode inductor and the common mode inductor is realized, the difference mode inductor is effectively increased without affecting characteristics of the common mode inductor, needed components are less, and the processing is simple. The impedance symmetry of an integrated structure is better, the conversion between difference mode noise and common mode noise is effectively prevented, and the filtering effect is good.

Description

A planar integrated EMI choke for planar EMI filter

technical field

The invention relates to a planar integrated EMI choke coil for a planar EMI filter.

Background technique

At present, the electromagnetic interference in the power electronic system is mainly conducted interference, and the EMI filter is an effective means to suppress this type of interference. Differential-mode and common-mode choke coils occupy the largest volume and weight of the entire EMI filter. The integration of choke coils is in line with the development trend of miniaturization and integration of power electronic systems. By consulting relevant literature, we found that the integration of discrete component choke coils is mainly divided into two types: one is the selection of a large magnetic ring with high magnetic permeability plus two small magnetic rings with low magnetic permeability proposed by Professor Yang Yugang of Liaoning University of Engineering Science and Technology The choke coil integration method, under differential mode excitation, the magnetic flux in the large magnetic ring core cancels each other, and the small magnetic ring provides a path for the magnetic flux to increase the differential mode inductance; under common mode excitation, due to the small magnetic ring permeability Low, the main magnetic flux strengthens each other in the large magnetic ring, resulting in a large common-mode inductance, but the integrated structure still requires three toroidal cores, which is not reduced compared to discrete ones, and the utilization of the magnetic core window is too low ; Second, CPES adopts a new winding method, which realizes the integration of choke coils with only two magnetic cores with different magnetic permeability. The difference and common mode inductance can be adjusted independently, but the winding method is complicated and the parasitic capacitance is also significantly increased. big. Rengang Chen of Virginia Tech University proposed a planar magnetic integration structure of choke coils for planar filters, and used the leakage inductance of common-mode inductors to realize differential-mode inductance. The insertion of leakage inductance layers can increase the differential-mode inductance, but at the same time The common mode inductance is weakened, and the differential mode inductance is not easy to adjust.

Contents of the invention

For above problem, the present invention proposes a kind of planar integrated EMI choke coil for planar EMI filter, EMI choke coil plane integration new structure, this planar magnetic integrated choke coil has realized the integration of differential and common mode inductors, Moreover, while effectively increasing the differential mode inductance, the characteristics of the common mode inductance are not affected, and the required components are less than discrete ones, and the processing is simple.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A kind of planar integrated EMI choke coil that is used for planar EMI filter, comprises the outer magnetic ring that is made up of a pair of EDT magnetic core, a pair of I-type magnetic cores opposite to each other, and is arranged on described EDT magnetic core and I-type The inner magnetic ring between the magnetic cores; wherein the inner magnetic ring includes first and second PCB boards arranged opposite to each other and both ends are symmetrical rings, and the first and second PCB boards are covered by a substrate, Composed of coils on the substrate, and the annular parts at both ends of the substrates of the first and second PCB boards are provided with annular through holes; a protruding piece is respectively provided on the inner wall of each EDT magnetic core, and the protruding piece passes through in turn. The annular through holes on the first and second PCB boards opposite to it; wherein, the coils covered on the substrate of the first PCB board are spirally wound along the circumferences of the two annular through holes at both ends of the first PCB board, A double annular spiral coil is formed; the coil has a first port A and a second port C; the coil covered on the substrate of the second PCB is formed by connecting along the outer circumference of two annular through holes at both ends of the second PCB The channels are wound to form a racetrack coil; the coil has a first port B and a second port D;

The EMI choke uses the first port A of the double annular spiral coil and the first port B of the racetrack coil as the input port of the EMI choke respectively, and the second port C, The second port D of the racetrack coil is used as the output port of the EMI choke coil;

When the EMI choke coil flows through the common mode current, the magnetic flux generated in the outer magnetic ring strengthens each other, and the magnetic flux generated by the inner magnetic ring cancels each other; when the EMI choke coil flows through the differential mode current, the magnetic flux generated in the outer magnetic ring The magnetic fluxes cancel each other out, and the magnetic fluxes generated by the inner magnetic rings reinforce each other.

As a preferred technical solution of the present invention: a spacer is placed between the EDT magnetic cores and the I-shaped magnetic cores arranged oppositely in pairs.

As a preferred technical solution of the present invention: the spacer is a paper sheet or a plastic sheet.

As a preferred technical solution of the present invention: the number of turns of the two toroidal helical coils of the double toroidal helical coil and the number of turns of the racetrack coil are the same.

As a preferred technical solution of the present invention: the coils covered on the first and second PCB boards are copper foil coils.

As a preferred technical solution of the present invention: the substrates of the first and second PCB boards are made of epoxy resin material.

As a preferred technical solution of the present invention: the magnetic permeability of the outer magnetic ring of the EMI choke coil is greater than the magnetic permeability of the inner magnetic ring.

As mentioned above, the present invention proposes a planar integrated EMI choke for a planar EMI filter, the planar integrated EMI choke uses two magnetic cores with different permeability to realize the integration of differential mode inductance and common mode inductance Moreover, the independent adjustment of differential and common-mode inductance is realized, and the differential-mode inductance is effectively increased without affecting the characteristics of common-mode inductance. The required components are less than discrete ones, and the processing is simple. The impedance symmetry of the integrated structure is also superior to that of the discrete one, which effectively prevents the conversion of poor and common mode noise, and has a good filtering effect.

Description of drawings

Fig. 1 is a schematic structural view of the planar integration of the EMI choke designed in the present invention.

Fig. 2 is the structural representation of the first PCB board that the present invention designs.

Fig. 3 is the structural representation of the second PCB board that the present invention designs.

FIG. 4A is a schematic diagram of magnetic flux coupling under common mode current designed in the present invention.

FIG. 4B is a schematic diagram of magnetic flux coupling under differential mode current designed in the present invention.

Fig. 5 is the equivalent circuit schematic diagram of the integrated choke coil designed by the present invention.

Detailed ways

The technical scheme of the present invention is described in detail below in conjunction with accompanying drawing:

As shown in Fig. 1, Fig. 2 and Fig. 3, the present invention comprises an outer magnetic ring composed of a pair of EDT magnetic cores and a pair of I-type magnetic cores facing each other, and is arranged between the EDT magnetic core and the I-type magnetic core. The inner magnetic ring between the cores; wherein the inner magnetic ring includes first and second PCB boards that are arranged opposite to each other and have symmetrical rings at both ends, and the first and second PCB boards are covered by the substrate and the Composed of coils on the substrate, and the annular parts at both ends of the substrates of the first and second PCB boards are provided with annular through holes; a protruding piece is respectively provided on the inner wall of each EDT magnetic core, and the protruding piece runs through it in turn. The annular through holes on the opposite first and second PCB boards;

Wherein, the coil covered on the substrate of the first PCB board 203 is respectively arranged along the circumference of the two annular through holes at the two ends of the first PCB board 203 to form a double annular spiral coil 207; the coil has a first port A With the second port C; the coil covered on the substrate of the second PCB board 204 is connected to the formed channel along the outer circumference of the two annular through holes at both ends of the second PCB board 204 to form a racetrack coil 209; The coil has a first port B and a second port D; the EMI choke uses the first port A of the double annular spiral coil and the first port B of the racetrack coil as the input ports of the EMI choke respectively, so as to The second port C of the double annular spiral coil and the second port D of the racetrack coil are used as the output port of the EMI choke coil; when the EMI choke coil flows through the common mode current, the magnetic flux generated in the outer magnetic ring interacts with each other Strengthening, the magnetic flux generated by the inner magnetic ring cancels each other; when the EMI choke coil flows through the differential mode current, the magnetic flux generated in the outer magnetic ring cancels each other, and the magnetic flux generated by the inner magnetic ring strengthens each other.

As shown in Fig. 2 and Fig. 3, the first PCB board 203 is made of double helix coil 207 and epoxy resin 208 connected together, and this PCB board uses epoxy resin as the substrate, and the upper layer of epoxy resin is covered with double helix The bottom layer of the coil and epoxy resin is not changed. The second PCB board 204 is composed of a racetrack-shaped copper foil coil 209 and epoxy resin 210. The PCB board uses epoxy resin as a substrate, and the upper layer of the epoxy resin is covered with a racetrack-shaped copper foil coil, and the bottom layer of the epoxy resin is not made. Change. A spacer is placed between two opposite EDT magnetic cores and the I-type magnetic core to reduce the magnetic permeability, such as a spacer is placed between the first EDT magnetic core 201 and the first I-type magnetic core 205, In order to reduce the magnetic permeability of the first EDT magnetic core 201 , spacers are placed between the second ETD magnetic core 202 and the second I-shaped magnetic core 206 to reduce the magnetic permeability of the second ETD magnetic core 202 . Wherein, the separator can be a material having a magnetic permeability similar to that of air, such as a paper or plastic sheet or other sheets with low magnetic permeability.

For the convenience of magnetic circuit analysis, the present invention equivalently converts two ETD magnetic cores into two magnetic rings with different magnetic permeability, the outer magnetic ring has high magnetic permeability and the inner magnetic ring has low magnetic permeability. As shown in Figure 4A, when the common mode current flows through the integrated choke coil, the magnetic fluxes Φ _{H_CM1} and Φ _{H_CM2} are generated in the outer magnetic ring, which reinforce each other; the magnetic fluxes Φ _{L_CM1} and Φ _{L_CM2} generated by the inner magnetic ring cancel each other out, temporarily Leakage flux is not considered. When the number of turns of the coil is the same, then:

As shown in Figure 4B, when the differential mode current flows through the integrated choke, the outer magnetic ring generates magnetic fluxes Φ _{H_DM1} and Φ _{H_DM2} that cancel each other out; the inner magnetic ring generates magnetic fluxes Φ _{L_DM1} and Φ _{L_DM2} that reinforce each other. When the number of turns of the coil is the same, then:

From the above analysis, it can be seen that the difference and common mode inductance of the integrated structure choke coil can be approximately given by the following formula:

Wherein, N is the number of turns of the coil, A is the effective cross-sectional area of the magnetic core, l is the average magnetic path length, μ ₀ is the magnetic permeability of the air, μ _rH is the magnetic permeability of the second ETD magnetic core 202, μ _rL is the Eth A magnetic permeability of the ETD magnetic core 201 , the magnetic permeability is reduced by placing a spacer between the ETD magnetic core and the I-type magnetic core. By adjusting μ _rL , the differential mode inductance L _DM can be adjusted independently, while the common mode inductance L _CM is not affected by it. The equivalent circuit of the integrated choke is shown in Figure 5.

This invention is funded by the Open Fund of Graduate Innovation Base (Laboratory) of Nanjing University of Aeronautics and Astronautics. The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and can also be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. Variations.

Claims (7)

1. A planar integrated EMI choke for a planar EMI filter, characterized by: the magnetic core comprises a pair of external magnetic rings formed by pairwise opposite pairs of EDT magnetic cores and a pair of I-type magnetic cores, and an internal magnetic ring arranged between the EDT magnetic cores and the I-type magnetic cores; the inner magnetic ring comprises a first PCB and a second PCB which are arranged oppositely and of which two ends are symmetrical and annular, wherein the first PCB and the second PCB are both composed of a substrate and a coil covered on the substrate, and annular through holes are formed in annular parts at two ends of the substrate of the first PCB and the second PCB; the inner wall of each EDT magnetic core is respectively provided with a protruding piece, and the protruding pieces sequentially penetrate through the annular through holes on the first PCB and the second PCB opposite to the protruding pieces; wherein,

the coils covered on the substrate of the first PCB (203) are spirally wound along the circumferences of the two annular through holes at the two ends of the first PCB respectively to form a double-annular spiral coil (207); the coil has a first port (A) and a second port (C);

the coil covered on the substrate of the second PCB (204) is wound along a channel formed by connecting the peripheries of the two annular through holes at the two ends of the second PCB to form a runway-type coil (209); the coil has a first port (B) and a second port (D);

the EMI choke coil takes a first port (A) of the double-ring spiral coil and a first port (B) of the runway-type coil as input ports of the EMI choke coil, and takes a second port (C) of the double-ring spiral coil and a second port (D) of the runway-type coil as output ports of the EMI choke coil;

when the EMI choking coil flows through the common-mode current, magnetic fluxes generated in the outer magnetic rings are mutually strengthened, and magnetic fluxes generated by the inner magnetic rings are mutually counteracted; when the EMI choking coil flows through the differential mode current, magnetic fluxes generated in the outer magnetic ring are mutually offset, and magnetic fluxes generated by the inner magnetic ring are mutually strengthened.

2. A planar integrated EMI choke for a planar EMI filter according to claim 1, characterized in that: and a spacer is padded between the two opposite EDT magnetic cores and the I-type magnetic core.

3. A planar integrated EMI choke for a planar EMI filter according to claim 2, characterized in that: the spacer is a paper sheet or a plastic sheet.

4. A planar integrated EMI choke for a planar EMI filter according to claim 1, characterized in that: the number of turns of the two annular spiral coils of the double annular spiral coil (207) is the same as the number of turns of the track type coil (209).

5. A planar integrated EMI choke for a planar EMI filter according to claim 1, characterized in that: and the coils covered on the first PCB and the second PCB are both copper foil coils.

6. A planar integrated EMI choke for a planar EMI filter according to claim 1, characterized in that: the base plates of the first PCB and the second PCB are made of epoxy resin materials.

7. A planar integrated EMI choke for a planar EMI filter according to claim 1, characterized in that: and the magnetic permeability of the outer magnetic ring of the EMI choking coil is greater than that of the inner magnetic ring.

Images