A transformer for naturally canceling common-mode noise of a power converter with symmetrical noise sources

Abstract

The present invention discloses a transformer with symmetrical noise sources that naturally cancels common-mode noise in power converters. The transformer comprises a magnetic core and windings. The core is symmetrical in shape, with equal magnetic flux around the left and right half-turns of each winding. The windings are wound around the two inner magnetic poles of the core, with each layer comprising a single or multiple turns. The total number of winding layers is an even number, 2n, and the winding layout is mirror-symmetric about the core. This transformer eliminates the need for additional components and can reduce the common-mode noise of a converter by more than 20dBμV without affecting the transformer's electrical performance.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering, and in particular to a transformer with symmetrical noise sources and natural cancellation of common-mode noise of a power converter. Background Art

[0002] Push-pull and full-bridge LLC resonant converters, due to their high efficiency and power density, are widely used in various fields, including aerospace, electric vehicles, and server power supplies. Driven by the trend toward higher frequencies and smaller sizes, wide-bandgap semiconductor switching devices and planar integrated matrix transformers are increasingly being used in these converters. However, the rapid switching speeds and large parasitic capacitance between the primary and secondary windings lead to severe common-mode noise. Common-mode filters are a common method for noise suppression, but the high raw common-mode noise of the converter results in large filters, severely limiting the power density of the converter. Suppressing the converter's raw common-mode noise by targeting its transmission path can significantly reduce the filter's size. As a key component in the common-mode noise transmission path, the transformer can be used to reduce raw common-mode noise, reduce the size of the common-mode filter, and increase the converter's power density.

[0003] Common noise reduction measures for transformers include shielding, balancing or offsetting windings, adding compensation capacitors, and equipotential arrangements for the primary and secondary windings. However, these methods all have drawbacks. Shielding, shielding, or offsetting windings increase the transformer's size and lead to eddy current losses. Compensation capacitors have high requirements for capacitance tolerance and inherent characteristics, making it difficult to find the right value. Equipotential winding arrangements are not suitable for applications with large turns ratios. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a transformer with symmetrical noise sources that naturally cancels out the common-mode noise of a power converter. No additional components need to be added to the transformer. Without affecting the electrical performance of the transformer, the use of the transformer in the present invention can reduce the common-mode noise of the converter by more than 20dBμV.

[0005] To solve the above technical problems, the present invention provides a transformer with symmetrical noise sources and natural cancellation of common-mode noise of a power converter, comprising: a magnetic core and a winding, wherein the magnetic core is symmetrical in shape and the magnetic flux around the left and right half turns of each winding is equal, the winding is wound on the center column of the magnetic core, each layer is wound with a single turn or multiple turns, the total number of winding layers is an even number 2n, and the winding layout is mirror-symmetric about the magnetic core.

[0006] Preferably, the winding is a flat copper wire winding or a PCB trace.

[0007] Preferably, the shape of the magnetic core is symmetrical in the left and right directions, and the magnetic flux in the magnetic core is symmetrically distributed about the left and right half turns of each winding.

[0008] Preferably, the magnetic core includes an upper magnetic plate and a lower magnetic plate connecting four magnetic columns, and the upper magnetic plate and the lower magnetic plate have the same length, width and height.

[0009] Preferably, the four magnetic columns include two inner magnetic columns for winding and two outer magnetic columns for shunting magnetic flux. The cross-sectional area of ​​the outer magnetic columns is the same as that of the upper and lower magnetic plates and is half of the cross-sectional area of ​​the inner magnetic columns.

[0010] Preferably, there are air gaps of the same length between the upper magnetic plate and the four magnetic pillars, a longitudinal air gap is opened in the middle of the upper magnetic plate, and the length of the air gap is twice the length of the air gap between the upper magnetic plate and the four magnetic pillars, and the window area between the outer magnetic pillars and the inner magnetic pillars is half the window area between the two inner magnetic pillars.

[0011] Preferably, the primary windings wound on the same inner magnetic column are connected in series, the primary windings wound on two inner magnetic columns are connected in parallel, the windings on the two inner magnetic columns are wound in opposite directions and are mirror-symmetrical about the middle of the magnetic core.

[0012] The beneficial effects of the present invention are as follows: the present invention does not require any additional components, and will not lead to an increase in transformer volume, cost, or performance degradation; it can achieve precise symmetrical transformer design, which helps to naturally cancel out the common-mode noise of push-pull and full-bridge resonant converters, reduces the design pressure of common-mode filters, and improves the power density of the converter; the winding structure is simple, and the lower n layers can be obtained by flipping the upper n layers, saving manufacturing costs; there are multiple distributed air gaps in the magnetic core, which can effectively reduce the AC loss of the transformer winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the magnetic core and winding layout of the symmetrical integrated matrix transformer of the present invention.

[0014] Figure 2 The figure shows a comparison of the common-mode noise of a full-bridge LLC resonant converter using a traditional integrated matrix transformer and the symmetrical integrated matrix transformer proposed in the present invention. DETAILED DESCRIPTION

[0015] A transformer with symmetrical noise sources and natural common-mode noise cancellation for a power converter comprises a magnetic core and windings. The magnetic core is symmetrical in shape, and the magnetic fluxes surrounding the left and right half turns of each winding are equal. The windings are wound around two inner magnetic columns of the magnetic core, with each layer being a single turn or multiple turns. The total number of winding layers is an even number 2n, and the winding layout is mirror-symmetrical about the magnetic core.

[0016] like Figure 1As shown, the symmetrical integrated matrix transformer core proposed by the present invention is symmetrical in shape on the left and right sides, and the magnetic flux in the core is symmetrically distributed about the left and right half-turns of each winding. The magnetic core includes four magnetic pillars, inner and outer, and two magnetic plates, upper and lower. The four magnetic pillars are all connected to the lower magnetic plate, wherein the thickness of the upper and lower magnetic plates and the width of the two outer magnetic pillars are w, and the width of the two inner magnetic pillars is 2w. The upper and lower magnetic plates have the same length, width and height. There is an air gap l of the same length between the four magnetic pillars and the upper magnetic plate. A longitudinal air gap is opened in the middle of the upper magnetic plate, and the air gap length is 2l. The longitudinal cross-sectional area of ​​the upper and lower magnetic plates is the same as the cross-sectional area of ​​the outer magnetic pillars 1 and 2, and both are half the cross-sectional area of ​​the inner magnetic pillar. The core window 1 and window 3 between the outer magnetic pillars and the inner magnetic pillars have the same area, which is half the area of ​​the core window 2 between the two inner magnetic pillars. The windings are wound around the two inner poles of the core, with a total of four layers per pole. Each layer can be wound with a single or multiple turns. The first and second layers on each inner pole can be rotated 180 degrees along the black dashed line to form the third and fourth layers. Primary windings wound on the same inner pole are connected in series, while primary windings wound on two inner poles are connected in parallel. The windings on the two inner poles are wound in opposite directions and are mirror-symmetric about the red dashed line.

[0017] like Figure 2 As shown, compared with the traditional integrated matrix transformer, the common mode noise of the full-bridge LLC resonant converter using the symmetrical integrated matrix transformer proposed in the present invention is reduced by more than 20dBμV in the low frequency band and by 3-6dBμV in the high frequency band.

Claims

1. A transformer for naturally canceling common-mode noise of a power converter with symmetrical noise sources, characterized in that: The invention comprises a magnetic core and a winding, wherein the magnetic core is symmetrical in shape and the magnetic flux around the left and right half turns of each winding is equal, the winding is wound on the two inner magnetic poles of the magnetic core, each layer is wound with a single turn or multiple turns, the total number of layers of the winding is an even number of layers 2n, the winding layout is mirror-symmetrical about the magnetic core, the magnetic core shape is symmetrical in left and right, and the magnetic flux in the magnetic core is symmetrically distributed about the left and right half turns of each winding, the primary windings wound on the same inner magnetic pole are connected in series, the primary windings wound on the two inner magnetic poles are connected in parallel, the windings on the two inner magnetic poles are wound in opposite directions, and are mirror-symmetrical about the center of the magnetic core; The magnetic core includes an upper magnetic plate and a lower magnetic plate connecting four magnetic pillars. The upper magnetic plate and the lower magnetic plate have the same length, width and height. The four magnetic pillars include two inner magnetic pillars for winding and two outer magnetic pillars for diverting magnetic flux. The cross-sectional area of ​​the outer magnetic pillars is the same as that of the upper and lower magnetic plates, and is half of the cross-sectional area of ​​the inner magnetic pillars. There is an air gap of the same length between the upper magnetic plate and the four magnetic pillars. A longitudinal air gap is opened in the middle of the upper magnetic plate, and the length of the air gap is twice the length of the air gap between the upper magnetic plate and the four magnetic pillars. The window area between the outer magnetic pillars and the inner magnetic pillars is half of the window area between the two inner magnetic pillars.

2. The transformer for naturally canceling common-mode noise of a power converter with symmetrical noise sources as claimed in claim 1, wherein: The winding is a flat copper wire winding.

3. The transformer for naturally canceling common-mode noise of a power converter with symmetrical noise sources as claimed in claim 1, wherein: The windings are PCB traces.

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