High frequency (MHz) soft switched flyback dc-dc converter using GaN switches and six-layered PCB transformer

The increased switching losses with increasing switching frequency are the biggest concerns in designing high power density converters. This paper presents the investigation of an energy efficient DC-DC flyback converter in combination with six layered printed circuit board transformer. The recorded efficiency of the low profile transformer for the frequency range of 1-5MHz is 98% at power density of 770W/in
³
. The proposed converter is characterized for frequencies up to 4MHz by using possible soft switching techniques such as Boundary Mode and Quasi Resonant Mode. The emerging Gallium Nitride (GaN FET) devices are used as power switch. The control is incorporated with Digital Signal Processor (dsPIC) for both the Boundary and Quasi Resonant Modes of operations. The proposed flyback DC-DC converter is tested on a prototype Printed Circuit Board (PCB). The performance of the proposed converter is investigated for the telecom input voltage range of 36-72Vdc. The maximum obtained energy efficiency of the converter is about 94%. According to the authors' knowledge, this is the maximum efficiency ever achieved in flyback converters switching in MHz frequency range. The results are very encouraging for the development of high frequency, high power density and low cost isolated power converters.