Utilization of EMI Shielding in PCB Matrix Transformer for Inductor Integration in High Power Density Resonant Converter

Magnetic integration of printed circuit board transformer is imperative to achieve high-efficiency DC-DC converter for the off-line power supply. This paper proposes a method to integrate controllable leakage inductance within a PCB-based matrix transformer. The EMI shielding layers of a 6-layer PCB transformer are utilized to create leakage flux within the transformer. The created leakage inductance is controlled and utilized as a series resonant inductance to form a regulated LLC converter. The proposed method increases the utilization of the PCB winding from 66% to 100%, which increases the throughput of the PCB transformer. A case study of a 300 kHz 400 V to 48 V regulated LLC converter is presented. The design is based on PCB magnetics which has easier manufacturability and lower cost than the Litz wire magnetics. Prototype for 400 V/48 V 3 kW 300 kHz is demonstrated with power density > 1 kW/in(3) and peak efficiecnt of 98.7%.