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 300kHz 400V to 48~V regulated LLC converter is presented. The design is based on PCB magnetics which has easier manufacturability and lowers cost compared to the Litz wire magnetics. Prototype for 400V/48V 3kW 300kHz is demonstrated with power density > 1kW/in3.
