Mid-point voltage control of a series half bridge converter with GaN switches in 800V applications

A series half bridge (SHB) topology with a new control methodology is introduced for high-performance cost-effective automotive DC-DC converters. The topology enables the use of 650V gallium nitride (GaN) high-electron-mobility transistor (HEMT) and zero voltage switching (ZVS) operation for an 800V battery system. In addition, a new mid-point voltage control algorithm is employed to balance the voltage stress and thermal behavior of the power switches while maintaining ZVS with high frequency pulse width modulation (PWM). Proof of concept is demonstrated in a 3.5 kW 800V to 13.5V DCDC prototype, with an efficiency greater than 95.5%.