CN102136828B - A barrel-wall EMI filter composed of spiral flat coils - Google Patents

Abstract

The invention provides a cylinder wall type electromagnetic interference (EMI) filter consisting of a spiral flat coil. The filter comprises an EER magnetic core, and common mode integrated LC modules, a leakage inductance layer and differential mode capacitors which are arranged by taking the EER core as an axis. The common mode integrated LC modules comprises a common mode integrated LC structure I and a common mode integrated LC structure II. The differential mode capacitors comprise a differential mode capacitor I and a differential mode capacitor II. The two common mode integrated LC structures are isolated by the leakage inductance layer. The differential mode capacitor I is arranged at one end of the common mode integrated LC module as the input end of the whole filter, and the differential mode capacitor II is arranged at the other end of the common mode integrated LC module as the output end of the whole filter. The cylinder wall type integrated LC structures are adopted as basic components of the integrated EMI filter provided by the invention, so that high frequency current is uniformly distributed on the spiral flat coil without influencing the performance of the filter; and due to the selection of the EER core, the utilization rate and effective section area of the core are both increased.

Description

A barrel-wall EMI filter composed of spiral flat coils

technical field

The invention relates to an EMI power supply filter, in particular to a cylinder-wall type EMI filter composed of a spiral flat coil.

Background technique

The switching operation of power devices in various power electronic devices causes extremely large voltage or current pulses, which cause severe electromagnetic interference (EMI). At present, there are two main methods for people to solve the problem of electromagnetic interference in power electronics in practical engineering: one is to find out the source of electromagnetic interference in power electronic circuits, and to reduce or eliminate electromagnetic interference by developing new components and designing new circuit topologies. The second is to use electromagnetic interference (EMI) filters to effectively block the transmission path of conducted electromagnetic interference (150 kHz ~ 30 MHz), which is also the most common and commonly used method to solve electromagnetic interference in engineering. Properly connecting this type of filter between the power supply and the load can not only prevent the noise generated by the power electronic device from entering the power grid, but also prevent various high-frequency noises in the power grid from entering the power electronic device through conduction coupling.

The implementation of EMI power filters is conventionally done with discrete components, which raises many problems. First, due to the parasitic parameters of discrete components, such as the equivalent parallel capacitance (Equivalent Parallel Capacitance-EPC) of inductors and the equivalent series inductance (Equivalent Series Inductance-ESL) of capacitors, some analysis results have also clearly shown that EMI power The high-frequency performance of the filter is mainly determined by the parasitic parameters; secondly, the parasitic parameters caused by the wiring of the filter will further weaken the high-frequency performance of the filter; thirdly, for different elements of a discrete EMI power filter Consideration of factors such as device type, size, and size, as well as issues such as interconnection and connection gaps between components, will lead to a reduction in space utilization. Therefore, the modeling, construction, design and optimization of EMI power filters have always been a challenge for electrical engineers.

The proposal of the planar magnetic integrated EMI filter is undoubtedly a great leap forward in filter manufacturing. A generalized transmission line theory proposed by YingLin Zhao of Virginia Tech can theoretically predict the high-frequency characteristics of the planar LC structure. Rengang Chen designed a planar EMI filter (Fig. 1) for switching power supply systems. The filter uses a planar EI core and consists of a differential mode capacitor (101), a common mode integrated LC structure (102) and a leakage inductance layer (103 ) composition, using a planar LC structure with one turn or less than one turn as a differential mode capacitor, using a four-terminal connection method to reduce the series parasitic inductance, and using two multi-turn planar LC structures to connect into a low-pass filter structure, Connected together in parallel as a common mode choke coil, this structure realizes the planar magnetic integration structure of the EMI power filter, reduces the volume, greatly improves the power density, and reduces the high-frequency parasitic parameters. The planar integrated EMI filter shown in Figure 1 uses a rectangular planar spiral coil. However, the filter also has defects. First, the current distribution at the direct corner is very uneven, which seriously affects the performance of the filter. Second, the utilization rate of the magnetic core is too low, and the effective cross-sectional area of the magnetic core is too small to effectively generate a large enough current. Third, the PCB board forming the planar integrated LC structure is made of high dielectric constant ceramic material, which is brittle and difficult to install.

Contents of the invention

technical problem:

The object of the present invention is to provide a cylindrical wall type EMI filter composed of a spiral flat coil to solve the defects in the prior art.

Invention content:

The present invention adopts following technical scheme in order to realize above-mentioned invention object:

A barrel wall type EMI filter composed of a spiral flat coil of the present invention includes an EER type magnetic core, and a common mode integrated LC module, a leakage inductance layer and a differential mode capacitor module set with the EER type magnetic core as the axis, The common-mode integrated LC module includes common-mode integrated LC structure I and common-mode integrated LC structure II, and the differential-mode capacitor includes differential-mode capacitor I and differential-mode capacitor II. The two common-mode integrated LC structures are separated by a leakage inductance layer. The mode capacitor I is set at one end of the common-mode integrated LC module as the input of the whole filter, and the differential-mode capacitor II is set at the other end of the common-mode integrated LC module as the output of the whole filter.

The common-mode integrated LC structure is composed of cylindrical wall ceramic materials, the inner and outer spiral coils are respectively composed of flat helical wires with the same line width, pitch and number of turns, and the ceramic cylinder wall is made of ceramic material NPO with a dielectric constant of 70-150. .

The differential mode capacitor is composed of a double-sided PCB board, the upper and lower plane spiral coils are single-turn, and the upper and lower layers are completely symmetrical, and the PCB board is made of ceramic material Y5V with a high dielectric constant of 10000-20000.

The EER-type magnetic core (201) is made of a ferrite material, and a flat-shaped cover plate is provided correspondingly to the EER-type magnetic core (201).

Beneficial effect:

Compared with the prior art, the present invention eliminates the influence of uneven current distribution at the corner of the rectangular spiral coil at high frequencies, and the vertical installation of the common-mode integrated LC unit effectively reduces the coupling of inductance and capacitance, and at the same time , The EER type magnetic core is used, which greatly improves the effective cross-sectional area of the magnetic core and the utilization rate of the magnetic core, thereby increasing the inductance value, reducing the total volume and quality of the filter, and improving the power density. The invention can be applied to the front-end converter of the distributed power system. Compared with the EMI power filter composed of discrete components, the volume is obviously reduced, and the insertion loss of the filter is improved, and the high-frequency performance of the filter is improved. The invention adopts the tube-wall integrated LC structure as the basic unit of the integrated EMI filter, so that the high-frequency current is evenly distributed on the planar spiral coil without affecting the performance of the filter, and the selection of the EER type magnetic core improves the utilization of the magnetic core The rate increases the effective cross-sectional area of the magnetic core and is easy to install.

Description of drawings

Figure 1 is an integrated EMI filter based on a rectangular planar integrated LC structure.

Figure 2A is an integrated EMI filter based on a barrel-wall integrated LC structure.

Fig. 2B is an equivalent lumped parameter circuit of the barrel-wall integrated EMI filter.

Figure 3A is a cylindrical wall integrated LC structure.

Fig. 3B is the equivalent lumped parameter circuit of the barrel-wall integrated LC structure.

Figure 4A is an integrated differential mode capacitor.

Fig. 4B is an equivalent lumped parameter circuit integrating differential mode capacitors.

Detailed ways

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

As the example shown in Figure 2A, the cylinder wall type integrated LC structure provided by the present invention comprises an EER type magnetic core 201 as an integrated EMI filter, two differential mode capacitors 202 and 206, two integrated LC structures 203 and 205, one leakage inductance layer 204 . A ₁ and B ₁ of the differential mode capacitor I (Figure 4A) are used as the input terminals of the filter and are drawn out by wires, C ₁ is connected to point A of the integrated LC structure I (Figure 3A), D1 is connected to point A of the integrated LC structure II, and the difference The A2 point of the mode capacitor II is connected to the C point of the integrated LC structure I, the B2 point of the differential mode capacitor II is connected to the C point of the integrated LC structure II, the D points of the integrated LC structures I and II are respectively grounded, and the B points are suspended. The leakage inductance layer is between the integrated LC structures I and II, and _C2 and _D2 of the differential mode capacitor II serve as the output port of the filter (Fig. 2B).

Figure 3B is the equivalent circuit diagram of Figure 3A, the number of turns of the coil is N ₁ , the width of the wire is w ₁ , and the thickness of the cylinder wall ceramic is d ₁ , Figure 4B is the equivalent circuit diagram of Figure 4A, the number of turns is 1, and the width of the wire is w ₂ , the thickness of the PCB is d ₂ , the effective magnetic circuit area of the magnetic core is A _e , the magnetic circuit length is l _e , and the magnetic permeability is μ _r .

The inner and outer layers of the integrated EMI filter are symmetrical about the leakage inductance layer, and the results of the inner and outer layers are the same. Its common mode inductance is:

Integrated LC structure interlayer capacitance as common mode capacitance:

In the formula, l ₁ is the total length of the integrated LC structure coil wire.

A single-turn integrated LC structure acts as a differential-mode capacitor:

 

 

In the formula, l ₂ is the total length of the single-turn integrated LC structure coil.

A specific example of the present invention has been described in detail above, but it should be understood that the embodiments of the present invention are not limited thereto, and this example is only used to help understand the present invention. Various changes made to the present invention should be included within the scope of the present invention. The patent protection scope of the present invention should be limited by the appended claims.

Claims (3)

1. A cylindrical wall type EMI filter composed of a spiral flat coil, characterized in that it includes an EER type magnetic core (201), and a common mode integrated LC module set with the EER type magnetic core (201) as the axis, The leakage inductance layer (204) and the differential-mode capacitor module, the common-mode integrated LC module includes a common-mode integrated LC structure I (203) and a common-mode integrated LC structure II (205), and the differential-mode capacitor includes a differential-mode capacitor I (202) and The differential mode capacitor II (206), is isolated by the leakage inductance layer (204) between the two common mode integrated LC structures, and the differential mode capacitor I (202) is set at one end of the common mode integrated LC module as the input end of the whole filter, The differential mode capacitor II (206) is set at the other end of the common mode integrated LC module as the output end of the entire filter; The common-mode integrated LC structure I (203) and the common-mode integrated LC structure II (205) are composed of cylindrical wall ceramic materials, and the inner and outer spiral coils (301 and 303) are respectively made of flat coils with the same line width, pitch and number of turns. It is composed of spiral wires, and the ceramic cylinder wall (302) adopts ceramic material NPO with a dielectric constant of 70-150. 2. the cylinder wall type EMI filter that a kind of helical flat coil forms according to claim 1 is characterized in that described differential mode electric capacity is made of double-sided PCB board, and the upper and lower plane helical coils (401 and 403) are Single turn, and the upper and lower layers are completely symmetrical, and the plate material of the PCB board (402) adopts ceramic material Y5V with a high dielectric constant of 10000-20000. 3. The cylindrical wall type EMI filter that a kind of helical flat coil constitutes according to claim 1 is characterized in that described EER type magnetic core (201) adopts ferrite material, also includes flat cover plate and EER Type magnetic core (201) corresponding setting.

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