Composite filter circuit

Abstract

The utility model relates to a composite filter circuit. The composite filter circuit comprises two integrated differential and common mode filters, three cross-core magnetic beads and a three-phase common mode inductor which are sequentially arranged according to a signal flow direction, the first integrated differential common mode filter C is connected in parallel between the UIN end and the WIN end; the second integrated differential common mode filter C1 is connected in parallel between the WIN end and the VIN end; the UIN end is connected in series with a pin 1 of the three-phase common mode inductor through a first cross-core magnetic bead FB, the WIN end is connected in series with a pin 2 of the three-phase common mode inductor through a second cross-core magnetic bead FB1, and the VIN end is connected in series with a pin 3 of the three-phase common mode inductor through a third cross-core magnetic bead FB2; and a pin 4, a pin 5 and a pin 6 of the three-phase common mode inductor are respectively a UOUT end, a WOUT end and a VOUT end. The composite filter circuit adopts the integrated differential common mode filter, the cross-core magnetic beads and the three-phase common mode inductors which are arranged in sequence, and has the advantage of full-band coverage filtering.

Description

Technical Field

[0001] The utility model relates to a filtering circuit, in particular to a composite filtering circuit. Background Art

[0002] With the gradual improvement of technology, electronic products have entered thousands of households, and machines are becoming more and more intelligent. In order to complete human-like actions, motors have become the core of the actions of such products. While motors are widely used, the corresponding EMC problems have emerged. To deal with the noise of motors, people have chosen brushless motors, which are superior to brushed motors. However, the corresponding noise source has become the continuous on-off of the MOS transistors on the motor drive board. The EMI noise frequency band generated by the on-off changes of multiple MOS transistors ranges from Hz to GHz. The generated EMI noise is likely to interfere with the operation of other modules. The existing technologies have the following three pain points in filtering the on-off noise of MOS transistors in DC brushless motor drives:

[0003] 1. The bandwidth of traditional capacitor-inductor filtering is insufficient and cannot fully cover the noise generated by MOS transistors;

[0004] 2. Multiple capacitors with different capacitance values and inductors with different inductance values will resonate with each other, losing the corresponding filtering effect;

[0005] 3. Stacking too many filters is likely to form some noise loops, causing the noise of MOS transistors to radiate out. Summary of the Utility Model

[0006] In view of the above situation, it is necessary to provide a composite filtering circuit that solves at least one of the above problems.

[0007] A composite filtering circuit includes two integrated differential common-mode filters, three feed-through beads, and a three-phase common-mode inductor arranged in sequence according to the signal flow direction;

[0008] The first integrated differential common-mode filter C is connected in parallel between the U_IN terminal and the W_IN terminal;

[0009] The second integrated differential common-mode filter C1 is connected in parallel between the W_IN terminal and the V_IN terminal;

[0010] The U_IN terminal is connected in series with the 1st pin of the three-phase common-mode inductor through the first feed-through bead FB, the W_IN terminal is connected in series with the 2nd pin of the three-phase common-mode inductor through the second feed-through bead FB1, and the V_IN terminal is connected in series with the 3rd pin of the three-phase common-mode inductor through the third feed-through bead FB2;

[0011] The 4th, 5th, and 6th pins of the three-phase common-mode inductor are the U_OUT terminal, the W_OUT terminal, and the V_OUT terminal respectively.

[0012] As a further solution of the present utility model: the through-hole magnetic bead is a nickel-zinc ferrite through-hole magnetic bead.

[0013] As a further solution of the present utility model: the three-phase common-mode inductor is a manganese-zinc ferrite three-phase common-mode inductor.

[0014] The above composite filter circuit adopts an integrated differential common-mode filter, a through-hole magnetic bead and a three-phase common-mode inductor, and is arranged in sequence, having the advantage of full-frequency band coverage filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the circuit schematic diagram of the embodiment of the present utility model;

[0016] Figure 2 is the test data diagram before EMI noise reduction of the circuit of the embodiment of the present utility model;

[0017] Figure 3 is the test data diagram after EMI noise reduction of the circuit of the embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to make the objectives, technical solutions and advantages of the present utility model more clear and understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0019] In the description of the present utility model, unless otherwise specified, the meaning of "a plurality" is two or more; the terms "center", "longitudinal", "transverse", "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present utility model. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0021] As Figure 1 shown, a composite filter circuit includes two integrated differential common-mode filters, three bead cores, and a three-phase common-mode inductor arranged in sequence according to the signal flow direction;

[0022] The first integrated differential common-mode filter C is connected in parallel between the U_IN terminal and the W_IN terminal;

[0023] The second integrated differential common-mode filter C1 is connected in parallel between the W_IN terminal and the V_IN terminal;

[0024] The U_IN terminal is connected in series with the 1st pin of the three-phase common-mode inductor L through the first bead core FB, the W_IN terminal is connected in series with the 2nd pin of the three-phase common-mode inductor L through the second bead core FB1, and the V_IN terminal is connected in series with the 3rd pin of the three-phase common-mode inductor L through the third bead core FB2;

[0025] The 4th, 5th, and 6th pins of the three-phase common-mode inductor are the U_OUT terminal, the W_OUT terminal, and the V_OUT terminal respectively.

[0026] In this embodiment, the integrated differential common-mode filter, the bead core, and the three-phase common-mode inductor need to be arranged in strict order, and the three respectively target high-frequency, medium-frequency, and low-frequency noises. Specifically, the integrated differential common-mode filter filters high-frequency in the Ghz level, the bead core filters medium-frequency in the Mhz level, and the three-phase common-mode inductor filters low-frequency in the Khz level. Here, the order we use is to first set the integrated differential common-mode filter, then the bead core, and finally the three-phase common-mode inductor. The purpose is that the components for eliminating high-frequency need to be closer to the problem source end, thereby improving the noise reduction and filtering effect in the entire frequency band. The three components are combined in a specific order to finally achieve a filtering frequency band from Khz to Ghz.

[0027] Furthermore, the bead core is a nickel-zinc ferrite bead core. Essentially, a bead core is a wire wrapped with a layer of nickel-zinc ferrite magnetic material, and the noise is suppressed through the frequency impedance characteristics of the magnetic material. The magnetic permeability of nickel-zinc ferrite is generally between 100 and 1000, so it is applicable to the medium and high frequency bands. Compared with ordinary magnetic beads, it will not affect the useful signal. Therefore, the nickel-zinc ferrite bead core mainly suppresses noises from 50 MHz to 600 MHz.

[0028] Furthermore, the three-phase common-mode inductor is a Mn-Zn ferrite three-phase common-mode inductor. The three-phase common-mode inductor mainly targets the noise in the working frequency band of the MOS tube itself. As a three-channel filtering device, it is a special frequency inductor, applicable to a three-phase balanced system, having good dielectric properties at low and medium frequencies, and effectively reducing the electromagnetic interference noise in KHz.

[0029] As Figure 2 , Figure 3 The comparison in [references] can clearly show the filtering effect of the composite filter circuit provided by this application in the full frequency band. Figure 2 The figure shows the actual electromagnetic radiation test data of a brushless motor. In the figure, M1, M2, M3, and M4 are the frequency points with relatively serious electromagnetic radiation exceeding the standard. Since the noise of the MOST tube switch in the brushless motor drive circuit is a problem in the full frequency band, and the defect of the filtering measure cannot filter out the noise, there is electromagnetic radiation exceeding the standard in the frequency band of 120Mhz - 325Mhz. The punctuation marks of M1 and M2 are 120Mhz and 150Mhz, belonging to the medium-frequency band exceeding the standard; the punctuation marks of M3 and M4 are 192Mhz and 325Mhz, belonging to the high-frequency band exceeding the standard. Figure 3 The figure shows the actual electromagnetic radiation test data of the brushless motor for the filter circuit in this application. In the figure, M1, M2, and M3 are the punctuation marks corresponding to the Figure 2 frequency bands exceeding the standard. It can be seen that the M1 point is 109Mhz, the M2 point is 199Mhz, and the M3 point is 330Mhz. It is obvious that the electromagnetic radiation energy in the frequency band of 100Mhz - 330Mhz has significantly decreased and can already pass the corresponding electromagnetic radiation standard.

[0030] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the technical solution scope of the present invention, can make some changes or modifications to the above-disclosed technical content to be equivalent change equivalent embodiments. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A composite filter circuit, characterized in that: It includes two integrated differential common mode filters, three through-core magnetic beads and a three-phase common mode inductor L which are arranged in sequence according to the signal flow direction; The first integrated differential common mode filter C is connected in parallel between the U_IN terminal and the W_IN terminal; The second integrated differential common mode filter C1 is connected in parallel between the W_IN terminal and the V_IN terminal; The U_IN terminal is connected in series with the 1st pin of the three-phase common-mode inductor L through the first through-core magnetic bead FB, the W_IN terminal is connected in series with the 2nd pin of the three-phase common-mode inductor L through the second through-core magnetic bead FB1, and the V_IN terminal is connected in series with the 3rd pin of the three-phase common-mode inductor L through the third through-core magnetic bead FB2; Pins 4, 5 and 6 of the three-phase common-mode inductor L are respectively U_OUT, W_OUT and V_OUT.

2. The composite filter circuit according to claim 1, characterized in that: The through-core magnetic bead is a nickel-zinc ferrite through-core magnetic bead.

3. The composite filter circuit according to claim 1, characterized in that: The three-phase common-mode inductor L is a manganese-zinc ferrite three-phase common-mode inductor.

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