Planar transformer, power converter with planar transformer and circuit board with planar transformer

Abstract

The invention discloses a planar transformer and a power converter with the same. The planar transformer comprises a primary coil layer, a secondary coil layer, a bottom shielding layer and a top shielding layer, at least one of the bottom shielding layer and the top shielding layer comprises a shielding coil and an auxiliary winding, the shielding coil comprises a first copper foil section and asecond copper foil section, the winding direction of the first copper foil section is the same as that of the secondary coil, and the winding direction of the second copper foil section is opposite tothat of the secondary coil; the sum of the number of turns of the first copper foil section and the number of turns of the second copper foil section is less than or equal to 1; the auxiliary windingis used for providing a fixed power supply for a functional circuit of the planar transformer; at least part of the coil of the auxiliary winding is located outside the shielding coil. On the one hand, auxiliary winding wiring is convenient to form; on the other hand, an auxiliary winding does not need to be independently arranged, so the number of layers of the PCB can be reduced, existing shielding layer resources are fully utilized, and then the planar transformer is compact in structure.

Description

technical field [0001] The invention relates to the technical field of transformers, in particular to a planar transformer, a power converter and a circuit board having the same. Background technique [0002] The common-mode current of the transformer has a great influence on EMI. It is necessary to reduce the common-mode current caused by the primary coil as much as possible. Usually, in a traditional transformer, the common-mode current is adjusted by adjusting the number of turns of the transformer shielding winding to reduce EMI. interference from common mode noise. [0003] The Chinese patent application with the application number 201711390939.3 discloses a planar transformer. The planar transformer is the primary type, in which the shielding winding has one turn and the auxiliary winding has three turns. The common mode current is adjusted by adjusting the number of turns inside the compound winding. ; However, this solution needs to lead out the winding from the pri...

AI Technical Summary

Problems solved by technology

[0003] The Chinese patent application with the application number 201711390939.3 discloses a planar transformer. The planar transformer is the primary type, in which the shielding winding has one turn and the auxiliary winding has three turns. The common mode current is adjusted by adjusting the number of turns inside the compound winding. ; However, this solution needs to lead out the winding from the primary or secondary coil to build a consistent winding layer, resulting in complex processes and high costs; and, the primary winding has a high operating voltage, and a relatively large potential difference will be generated between it and the magnetic core, which may cause Insulation breakdown between the magnetic core and the winding reduces the reliability of the product

[0004] In addition, in the prior art, in order to supply power to the functional circuit (such as a chip) of the planar transformer, an additional auxiliary winding layer needs to be configured, so the number of PCB layers will increase

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