Two Stage GaN Transistor-Based Isolated Class E DC-DC Converter

On-Off control is usually adopted to regulate the output voltage of the isolated Class E DC-DC converter when the switching frequency increases up to multi-megahertz. In this control scheme, the parameters are usually designed at the lowest input voltage to ensure enough output power capacity. Unfortunately, it is revealed that with the increase of the input voltage, the conversion efficiency would decrease greatly and the voltage stress would increase under On-Off control. To solve this problem, a two stage isolated Class E DC-DC converter structure is proposed in this paper. In the two stage structure, a voltage step-down circuit is introduced to help regulate the input voltage of the isolated Class E DC-DC converter. Accordingly, the conversion efficiency could increase and the voltage stress would decrease. An experimental comparison between two stage structure with Buck circuit as step-down circuit and single stage structure is conducted. The experiment results show that the two stage structure could help improve the conversion efficiency by 5.10% and at the same time, reduce the voltage stress by 54V.