A kind of low leakage inductance planar transformer

It´s necessary to decrease the leakage inductance of transformer because it often produces a large voltage peak as device is turned off, meanwhile the large voltage peak is a source of EMI and produces a large voltage stress and affects the power supply´s efficiency. This paper proposes a kind of low leakage inductance planar transformer with shunt magnetic circuit structure, the primary winding number of this structure can be decreased to 1 turn and the equivalent secondary winding can be decreased to less than 1 turn, therefore the leakage inductance can be decreased remarkably, and it can be used to various turns ratio of high frequency transformer expressly in the transformer of low voltage and large current power supply. This shunt magnetic structure is verified with Maxwell 3D.