CN103390484A - EMI (Electro-Magnetic Interference) filter - Google Patents

Abstract

The invention provides an EMI (Electro-Magnetic Interference) filter, which comprises a bus and a circular magnet ring, wherein the bus is formed by eleven layers of materials, the bus is sleeved by the circular magnet ring, the copper layer and the nickel layer in the bus are conducting layers, all the metal conducting layers and the magnet ring form a common mode inductor, leakage inductance of the filter is a differential mode inductor, the first, second and third layers of the bus form a common mode capacitor of the filter, the ninth, tenth and eleventh layers of the bus form another common mode capacitor, the fifth, sixth and seventh layers of the bus form a differential mode capacitor of the filter. The thickness of each layer is uniform, and the sixth layer is centrosymmetric. According to the EMI filter, power requirements can be met only by properly selecting geometric dimensions of each part, the EMI filter can be used for solving the problem of electromagnetic compatibility of high-power electric and electronic converters, can automatically realize separation of interference current from load current, and has reflection and dissipation effects on interference signals, and the interference effect can be weakened obviously; with the adoption of the circular magnet ring, the common mode inductor of a system is effectively increased, and a better heat dissipation performance is realized.

Description

A kind of electromagnetic interface filter

Technical field

The invention belongs to electronic technology field, especially relate to a kind of electromagnetic interface filter.

Background technology

Electromagnetic interface filter is the economic passive device reliably of effectively blocking the Conducted Electromagnetic Interference transmission.Have under desirable impedance symmetry prerequisite at the hypothesis filter circuit, the common decoupling zero of traditional E MI filter is poor, common-mode filter two parts, then for both, studies separately and designs.Actual filter circuit impedance symmetry is difficult to be guaranteed, even the lead-in wire layout of printed circuit board (PCB) full symmetric on how much, the impedance of passive component itself is asymmetric is also the factor that can not be ignored.Circuit impedance is asymmetric easily causes mutual conversion between poor, common-mode noise, and this makes traditional Decoupling design method lose efficacy, and namely the actual filter effect of filter does not reach design object.What propose the earliest is the discrete element type electromagnetic interface filter, it is simple in structure, be easy to make, but its parasitic parameter is large, the parasitic parameter technology for eliminating is complicated, even the impedance deviation of same model element is also very large, in recent years, integrated EMI filter is suggested, and plane, flexible PCB structural type of small-power occasion etc. have successively occurred can be used for, the bus type integrated EMI filter that this seminar proposes can be used for large-power occasions, and has electromagnetic property and radiating effect preferably.

Summary of the invention

Technical problem to be solved by this invention is to overcome the deficiencies in the prior art, has proposed a kind of electromagnetic interface filter.Described filter adopts bus layering integrated technology, and the circular magnet ring in addition in the bus outside, significantly improved common mode inductance, and then reduced system bulk; Than the rectangle magnet ring, circular magnet ring magnetic circuit cross-sectional area is invariable, is more conducive to magnetic line of force circulation, and this structure leaves space, and heat dissipating state is more excellent; This structure adopts the integrated technology that filter and bus are united two into one, and has reduced stray parameter, has improved the stability of system; A kind of method of new solution powerful device electromagnetic compatibility problem is provided.

For solving the problems of the technologies described above, the technical solution adopted in the present invention is:

A kind of electromagnetic interface filter, described filter comprise bus and circular magnet ring; Described bus consists of the eleventh floor material, and the cross section of bus is rectangle; Described circular magnet ring is enclosed within on bus; In described eleventh floor material, material from ground floor to the eleventh floor material is respectively nickel, pottery, nickel, copper, nickel, pottery, nickel, copper, nickel, pottery, nickel, and the cross section of all eleventh floor materials is all rectangle, and each layer thickness is even, centered by layer 6, up and down is symmetrical; Wherein the copper layer is the load current conductive layer.

Described pottery employing dielectric constant is 2000 to 10000 ceramic material CaCu ₃Ti ₄O ₁₂.

Described circular magnet ring number is one or more, and each magnet ring is measure-alike, if a plurality of magnet ring, the arrangement pitch between magnet ring is even.

The invention has the beneficial effects as follows: the present invention proposes a kind of electromagnetic interface filter, described filter comprises bus and circular magnet ring; Described bus consists of the eleventh floor material, and circular magnet ring is enclosed within on bus; In bus, copper layer and nickel dam are conductive layer; All metal conducting layers and magnet ring form common mode inductance, and the leakage inductance of described filter is differential mode inductance; First to the 3rd layer and the 9th forms respectively two common mode capacitance of filter to eleventh floor; The 5th differential mode capacitor to layer 7 formation filter.Each layer thickness is even, and is symmetrical centered by layer 6.The present invention only needs suitably to select the physical dimension of each parts, just can meet the requirement of power, it can be used for the electromagnetic compatibility problem of high-power power electronic converter, can automatically realize separating of disturbance current and load current, interference signal is had concurrently reflection and dissipation effect, slacken interference effect obvious; Circular magnet ring has effectively increased the common mode inductance of system, has heat dispersion preferably.

Description of drawings

Fig. 1 is the cross section with the bus type integrated EMI filter of circular magnet ring.

Fig. 2 is the longitudinal cross-section with the bus type integrated EMI filter bus of circular magnet ring.

Embodiment

Below in conjunction with accompanying drawing, a kind of electromagnetic interface filter that the present invention is proposed is elaborated:

Example as shown in Figure 1, median generatrix type integrated EMI filter of the present invention is comprised of eleventh floor rectangle material and one or several circular magnet rings.

As shown in Figure 2, in this bus type integrated EMI filter, ground floor 1, the 3rd layer 3, layer 55, layer 77, the 9th layer 9, eleventh floor 11 are nickel dam; The second layer 2, layer 66, be pottery for the tenth layer 10; Be the copper layer for the 4th layer 4, the 8th layers 8; Circular magnet ring is enclosed within the outside of all eleventh floor layer structure buses.Wherein, ground floor 1, the second layer 2 and the 3rd layer of 3 formation the first common mode capacitance, the 9th layer 9, the tenth layers 10 and eleventh floor 11 formation the second common mode capacitance; Layer 55, layer 66 and layer 77 form differential mode capacitor.All metal conducting layers of described bus type integrated EMI filter and magnet ring form common mode inductance, and the leakage inductance of bus type integrated EMI filter is differential mode inductance.The 4th layer 4 and the 8th layers 8 of described bus type integrated EMI filter as the load current conductive layer.Ground floor 1 and eleventh floor 11 use cables are connected on the ground wire of system.

Circular magnet ring can adopt one or more magnet rings according to the actual parameter needs, and each magnet ring is measure-alike, if a plurality of magnet ring, it is uniform that arrangement pitch requires.It is the ceramic material CaCu of 2000-10000 that pottery adopts dielectric constant ₃Ti ₄O ₁₂(CCTO).

About the common mode capacitance part of this structure, the interference signal in electromagnetic compatibility problem is high-frequency signal, and due to kelvin effect, interference signal trends towards in the nickel dam in the outside flowing, and can automatically realize separating of common mode disturbances electric current and load current.About the differential mode capacitor part of this structure, due to proximity effect, high-frequency interferencing signal trends towards in the nickel dam of inboard flowing, and automatically realizes separating of differential-mode current and load current.

Less than copper, magnetic permeability is much larger than copper due to the resistivity of nickel, and interference signal more easily is converted to heat and consumes in nickel dam, and in addition, the part common mode interference signal is transferred to stratum by two common mode capacitance; Part differential mode interference signal is reflected back source through differential mode capacitor.

Common mode inductance consists of all metal conducting layers and the magnet ring of described bus type integrated EMI filter, and it is the inductance that transmission line self has.Load current passes magnet ring from positive and negative both direction, and both direction load current size is identical, and because of the effect of mutual inductance between wire, total equivalent inductance is weakened, and its value is close to zero; Disturbance current is to pass magnet ring from same direction, and both direction disturbance current size is identical, and because of the effect of mutual inductance between wire, total equivalent inductance is reinforced, and its value is larger, and this meets the condition of filtering interfering.So this common mode inductance has good inhibitory action to disturbance current, less on the impact of load current.Differential mode inductance is the leakage inductance of described bus type integrated EMI filter, and is relevant with the spatial arrangement of the symmetry of whole bus type integrated EMI filter and each several part.This filter accomplishes that easily each layer thickness is even, and is symmetrical centered by layer 6, easily realizes the symmetry of common mode inductance, differential mode capacitor and common mode capacitance.By the circular magnet ring of selected shape rule, uniformly-spaced evenly distributed, namely realize the symmetry of differential mode inductance.The present invention realizes reflection and dissipation dual-use function to interference signal by kelvin effect, proximity effect.In addition, according to the size of actual power, the physical dimension of this each layer of structure of choose reasonable, this filter is suitable for various power occasions.

Described bus type integrated EMI filter can be regarded as the coil that a number of turn is 1 circle, and conductor width is t ₁, conductor length is l ₁, the thickness of the second layer 2 and the tenth layer 10 is d ₁, the thickness of layer 66 is d ₂, the magnetic circuit area of magnet ring is A _e, the length of magnetic path is l _e, magnetic permeability is μ _r, permeability of vacuum is μ ₀, the relative dielectric constant of pottery is ε _r, permittivity of vacuum is ε ₀, differential mode inductance is L _dc, common mode capacitance is C _cm, differential mode capacitor is C _dm.

The common mode inductance of this structure can calculate with following formula:

$L_{\mathrm{dc}}=\frac{{\mathrm{\μ}}_0{\mathrm{\μ}}_r{A}_e}{l_e}$

This structure is symmetrical Shang Xia 6 about layer 6, and two common mode capacitance in up and down are identical, and its size is:

$C_{\mathrm{cm}}=\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_r{t}_1{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA00003460275700012.png"\; state="\{\{state\}\}">d</figure-callout>}}_1}$

The differential mode capacitor size of this structure is:

$C_{\mathrm{dm}}=\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_r{t}_1{l}_1}{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003460275700012.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}$

The above describes example of the present invention in detail, but should be appreciated that embodiments of the present invention are not limited in this, and this example only is used for helping to understand the present invention.Various variation instance made for the present invention, all should be within the scope of the present invention.Scope of patent protection of the present invention should have appending claims to limit.

Claims (3)

1. an electromagnetic interface filter, is characterized in that, described filter comprises bus and circular magnet ring; Described bus consists of the eleventh floor material, and the cross section of bus is rectangle; Described circular magnet ring is enclosed within on bus; In described eleventh floor material, material from ground floor to the eleventh floor material is respectively nickel, pottery, nickel, copper, nickel, pottery, nickel, copper, nickel, pottery, nickel, the cross section of all eleventh floor materials is all rectangle, and each layer thickness is even, and is symmetrical centered by layer 6; Wherein the copper layer is the load current conductive layer.

2. a kind of electromagnetic interface filter as claimed in claim 1, is characterized in that, described pottery employing dielectric constant is 2000 to 10000 ceramic material CaCu ₃Ti ₄O ₁₂.

3. a kind of electromagnetic interface filter as claimed in claim 1, is characterized in that, described circular magnet ring number is one or more, if a plurality of magnet ring, the arrangement pitch between magnet ring is even.

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