A high-power switching power supply conducting interference filter circuit

Abstract

The application discloses a kind of high-power switching power supply conducted interference filter circuit, including common mode inductance, still including air core coil, the common mode inductance is the ring inductor of annular magnetic core, one side of the common mode inductance is provided with the air core coil, the air core coil is spiral air core coil, and the central axis of the hole of the air core coil and the central axis of the annular magnetic core of the common mode inductance are coaxial or parallel, after the air core coil and the common mode inductance energization, the magnetic field generated by the air core coil and the leakage magnetic of the common mode inductance interact, increase the leakage magnetic of the common mode inductance, to increase the differential mode component of the common mode inductance, the air core coil with the leakage magnetic of the common mode inductance as virtual "magnetic core", increase the differential mode inductance of the air core coil.The application can effectively filter out the conducted interference of high-power switching power supply product.

Description

Technical Field

[0001] This invention relates to conducted interference filtering circuits for switching power supplies, and particularly to a conducted interference filtering circuit for a high-power switching power supply. Background Technology

[0002] Electromagnetic compatibility (EMC) refers to the ability of a device or system to operate within its electromagnetic environment without causing unacceptable electromagnetic interference to other devices in that environment. Therefore, EMC includes two aspects: first, the electromagnetic interference (EMI) generated by the device during normal operation must not exceed certain limits; second, the device must have a certain degree of immunity to electromagnetic disturbances present in its environment, i.e., electromagnetic susceptibility (EMS). EMI interference is further divided into conducted and radiated interference. The filter circuit proposed in this invention mainly addresses conducted interference.

[0003] In international certification standards, the conducted interference limits for switching power supplies mostly reference the conducted interference limits specified in CISPR 32 / EN 55032 CLASS B standard. See details... Figure 1 As shown in the diagram. Analysis indicates that conducted interference below 1MHz is primarily composed of differential-mode components. To filter out differential-mode interference below 1MHz, a differential-mode filter circuit is often constructed by connecting an X capacitor in parallel on the input live wire (L line) and neutral wire (N line) and a differential-mode inductor in series. However, in the design of high-power, high-power-density switching power supplies, due to limited size, it is impossible to use large X capacitors and differential-mode inductors. Furthermore, the differential-mode inductors in current switching power supplies typically use a coil with a ferrite core or magnetic rod as the winding core. When the current flowing through the coil is large, the core will saturate. In this state, the differential-mode inductor is similar to an air-core coil without a core, leading to a sharp decrease in differential-mode inductance and loss of its function in filtering differential-mode interference. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-power switching power supply conducted interference filtering circuit to solve the conduction problem in high-power, high-power-density switching power supply products, effectively filtering out conducted interference below 1MHz.

[0005] A high-power switching power supply conducted interference filtering circuit includes a common-mode inductor and an air-core coil. The common-mode inductor is a toroidal inductor with a toroidal magnetic core. The air-core coil is disposed on one side of the common-mode inductor and is a spiral air-core coil. The central axis of the central hole of the air-core coil is coaxial or parallel to the central axis of the toroidal magnetic core of the common-mode inductor. When the air-core coil and the common-mode inductor are energized, the magnetic field generated by the air-core coil interacts with the leakage magnetic field of the common-mode inductor, increasing the leakage magnetic field of the common-mode inductor and thus increasing the differential-mode component of the common-mode inductor. The air-core coil uses the leakage magnetic field of the common-mode inductor as a virtual "magnetic core" to increase the differential-mode inductance of the air-core coil.

[0006] When current flows through the air-core coil of this invention, a magnetic field is generated on the coil. Because the air-core coil is close to the common-mode inductor, the magnetic field generated by the air-core coil interacts with the leakage flux of the common-mode inductor, increasing the leakage flux of the common-mode inductor and further increasing the differential-mode component of the common-mode inductor. Furthermore, due to the presence of the leakage flux of the common-mode inductor, the energized air-core coil uses the leakage flux of the common-mode inductor as its "core," further increasing the differential-mode inductance of the air-core coil. This process is equivalent to the energized air-core coil and the common-mode inductor generating mutual inductance, the type of which is differential-mode.

[0007] The present invention also has the following preferred designs:

[0008] The hollow coil of the present invention can be a coil wound with a single conductor.

[0009] It can also be a coil wound around the pins of a device, or a coil wound around a portion of the wires of any of the following devices: X capacitor, fuse, or common-mode inductor.

[0010] The common-mode inductor of this invention is either a vertical common-mode inductor or a horizontal common-mode inductor. For a vertical common-mode inductor, the air-core coil can be located in front of or behind the common-mode inductor; for a horizontal common-mode inductor, the air-core coil can be located above or below the common-mode inductor.

[0011] The coil of the common-mode inductor of the present invention can be a pair of wires wound in parallel on the toroidal magnetic core, or it can be wound separately and symmetrically on the toroidal magnetic core.

[0012] The beneficial effects of this invention are as follows:

[0013] 1. It can effectively filter out conducted interference in high-power switching power supply products, especially differential-mode interference below 1MHz;

[0014] 2. The circuit structure is simple, low-cost, small in size, and easy to design. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 The conducted interference limit for CLASS B in the CISPR32 / EN55032 standard;

[0017] Figure 2 This is a schematic diagram of a first embodiment of a high-power switching power supply conducted interference filtering circuit according to the present invention;

[0018] Figure 3 This is a front view of a vertical common-mode inductor, the coil of which is a two-wire parallel winding;

[0019] Figure 4 for Figure 3 Side view of a vertical common-mode inductor;

[0020] Figure 5 for Figure 3 A bottom view of a vertical common-mode inductor;

[0021] Figure 6 A front view of a vertical common-mode inductor with separate coil windings;

[0022] Figure 7 This is a schematic diagram of a second embodiment of a high-power switching power supply conducted interference filtering circuit according to the present invention;

[0023] Figure 8 This is a schematic diagram of a third embodiment of a high-power switching power supply conducted interference filtering circuit according to the present invention;

[0024] Figure 9 This is a top view of a horizontal common-mode inductor;

[0025] Figure 10 for Figure 9 A front view of a horizontal common-mode inductor;

[0026] Figure 11 for Figure 9 A bottom view of a horizontal common-mode inductor;

[0027] Figure 12 This is a schematic diagram of a fourth embodiment of a high-power switching power supply conducted interference filtering circuit according to the present invention;

[0028] Figure 13 The conducted interference test waveform of a 1500W switching power supply product without the filter circuit of this invention is shown.

[0029] Figure 14 Conducted interference test waveforms of a 1500W switching power supply product with the filter circuit of this invention added. Detailed Implementation

[0030] To make the present invention clearer, it 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 merely illustrative and not intended to limit the scope of the invention.

[0031] First Embodiment

[0032] like Figure 2 As shown, a high-power switching power supply conducted interference filtering circuit includes a common-mode inductor 1 and an air-core coil 2. The common-mode inductor 1 is a toroidal inductor with a toroidal magnetic core. The air-core coil 2 is disposed on one side of the common-mode inductor 1. The air-core coil 2 is a spiral air-core coil, and the central axis of the central hole of the air-core coil 2 is coaxial or parallel to the central axis of the toroidal magnetic core of the common-mode inductor 1. After the air-core coil 2 and the common-mode inductor 1 are energized, the magnetic field generated by the air-core coil 2 interacts with the leakage magnetic field of the common-mode inductor 1, increasing the leakage magnetic field of the common-mode inductor 1, thereby increasing the differential-mode component of the common-mode inductor 1. The air-core coil 2 uses the leakage magnetic field of the common-mode inductor 1 as a virtual "magnetic core" to increase the differential-mode inductance of the air-core coil 2.

[0033] In this embodiment, as Figures 3 to 5 As shown, common-mode inductor 1 is a vertical common-mode inductor, with its coil wound in parallel on a toroidal magnetic core. Alternatively, common-mode inductor 1 can also be as follows: Figure 6 The coil shown is a hollow coil wound symmetrically on a toroidal magnetic core. Hollow coil 2 is a coil wound with a separate wire. In the filter circuit, hollow coil 2 is located in front of common-mode inductor 1, for example... Figure 2 A hollow coil 2 is positioned to the left of the common-mode inductor 1. The common-mode inductor 1 and the hollow coil 2 are connected in series on the product's input line. One pin of the common-mode inductor 1 serves as the input terminal 3 of the filter circuit, and the other pin serves as the output terminal 4 of the filter circuit. After the product is powered on, a large input current flows through the hollow coil 2, generating a magnetic field. This magnetic field interacts with the leakage flux of the common-mode inductor 1, increasing the leakage flux and further increasing the differential-mode component of the common-mode inductor 1. Due to the leakage flux of the common-mode inductor 1, the energized hollow coil 2 uses the leakage flux of the common-mode inductor 1 as its "core," further increasing the differential-mode inductance of the hollow coil 2. This process is equivalent to the energized hollow coil 2 and the common-mode inductor 1 generating mutual inductance, which is of the differential-mode type.

[0034] Under conditions of 115Vac input and 12V / 125A full load output, a comparative test was conducted using the CISPR32 / EN55032 CLASS B conducted emission test standard. The tested product was a 1500W switching power supply. Without the filter circuit of this invention, the conducted emission test curve is as follows: Figure 13 As shown, the conducted interference curve after adding the filter circuit of the circuit scheme of this invention is as follows: Figure 14 As shown. Figure 13 , Figure 14 The horizontal axis represents frequency (in MHz), and the vertical axis represents interference amplitude (in dBμV). Comparing the quasi-peak curves in the frequency range below 1 MHz reveals that... Figure 13 The interference levels in the quasi-peak curves at frequencies of 180kHz, 380kHz, 570kHz, 760kHz, and 950kHz exceeded the Limit2 limit, but... Figure 14 The quasi-peak curves in the data are all below the Limit2 limit. Comparing the average curves in the frequency range below 1MHz, especially the curves near 180kHz and 380kHz, it can be seen that... Figure 14 The curve margin is significantly better than Figure 13 Therefore, it can be seen that the filter circuit of the present invention can effectively filter out conducted interference below 1MHz.

[0035] Second Embodiment

[0036] like Figure 7 As shown, the difference between this embodiment and the first embodiment lies in that, in this embodiment, the filter circuit has an air-core coil 2 positioned to the right of the common-mode inductor 1, i.e., the air-core coil 2 is positioned behind the vertical common-mode inductor 1. The air-core coil 2 is formed by winding a portion of the conductors of the X capacitor and fuse. Alternatively, the air-core coil 2 can be formed by winding the pins of other components on the product. The common-mode inductor 1 and the air-core coil 2 are connected in series on the product's input line. One pin of the common-mode inductor 1 serves as the input terminal 3 of the filter circuit, and the other pin serves as the output terminal 4 of the filter circuit. After the product is powered on, the working principle of the common-mode inductor 1 and the air-core coil 2 is the same as in the first embodiment, which can increase the differential-mode inductance.

[0037] Third Embodiment

[0038] like Figure 8 As shown, the difference between this embodiment and the first embodiment is that the filter circuit in this embodiment uses a horizontal common-mode inductor, whose coils are separately and symmetrically wound on a toroidal magnetic core, as shown in the figure below. Figures 9 to 11 As shown. The air-core coil 2 is located above the common-mode inductor 1. The air-core coil 2 is formed by winding a portion of the conductor of the X capacitor and fuse. Alternatively, the air-core coil 2 can also be formed by winding the pins of other components on the product. The common-mode inductor 1 and the air-core coil 2 are connected in series on the product's input line. One pin of the common-mode inductor 1 serves as the input terminal 3 of the filter circuit, and the other pin serves as the output terminal 4 of the filter circuit. After the product is powered on, the working principle of the common-mode inductor 1 and the air-core coil 2 is the same as in the first embodiment, which can increase the differential-mode inductance.

[0039] Fourth embodiment

[0040] like Figure 12As shown, the difference between this embodiment and the third embodiment is that in the filter circuit of this embodiment, the hollow coil 2 is located below the horizontal common-mode inductor 1, and its hollow coil 2 is wound with a portion of the wires of the common-mode inductor 1. The common-mode inductor 1 and the hollow coil 2 are connected in series on the product input line. One pin of the common-mode inductor 1 serves as the input terminal 3 of the filter circuit, and the other pin serves as the output terminal 4 of the filter circuit. After the product is powered on, the working principle of the common-mode inductor 1 and the hollow coil 2 is the same as in the third embodiment, which can increase the differential-mode inductance.

[0041] In this invention, the relative distance and relative position between the common-mode inductor 1 and the air coil 2 can be adjusted according to requirements.

[0042] The above embodiments are merely preferred embodiments of the present invention, but should not be construed as limiting the invention. Any modifications and improvements made based on the concept of the present invention should fall within the protection scope of the present invention, and the specific protection scope is subject to the claims.

Claims

1. A high power switching power supply conducted interference filter circuit comprising a common mode inductor, characterized by: The common mode inductor is a toroidal inductor, and the air core coil is a spiral air core coil.

2. The conducted interference filter circuit for high power switching power supplies of claim 1, wherein: The air core coil is a coil wound by separate wires.

3. The conducted interference filter circuit for high power switching power supplies of claim 1, wherein: The air core coil is a coil wound by device pins.

4. The conducted interference filter circuit for high power switching power supplies of claim 1, wherein: The air core coil is a coil wound by part of wires of any device among the X capacitor, the fuse and the common mode inductor.

5. The conducted interference filter circuit for high power switching power supplies of any one of claims 1 to 4, wherein: The common mode inductor is a vertical common mode inductor or a horizontal common mode inductor.

6. The conducted interference filter circuit for high power switching power supplies of claim 5, wherein: The coil of the common mode inductor is double-wound on the toroidal core, or the coil of the common mode inductor is symmetrically wound on the toroidal core.

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