Enhancing Buck Converter Efficiency by Using GaN/Si Hybrid Switches to Suppress Dynamic On-State Resistance

In this work, it is demonstrated that the buck converter using a GaN/Si hybrid switch can achieve an even higher power conversion efficiency than the one using a pure-GaN switch with the same ratings. By replacing one of the dual paralleled GaN HEMTs with a Si superjunction mosfet having the same voltage rating yet a slightly higher resistance, the total conduction loss, however, is significantly decreased. This is accomplished through suppressing the dynamic ON-state resistance peculiar to GaN HEMTs. Optimizing the gate timing between the GaN and the Si devices within the hybrid switch enables exceptional low-loss performance. Both device-level and system-level demonstrations are performed. The experimental results prove that the p-GaN gate HEMT/Si MOSFET hybrid switch increases the efficiency by 2% and 3%, respectively, when compared to its pure-GaN and pure-Si counterparts, at an output power of 240 W and a switching frequency of 500 kHz.