T09.4 - An All-GaN 90.6% Peak Efficiency Switch-Rationalized 48V-to-Point-of-Load Hybrid Power Converter with Digitally Auto-Locked Vᴄꜰ Control Achieving 1,158A/Inch3 Current Density

This paper presents a novel all-GaN hybrid quadruple step-down (QSD) switching power converter featuring a power-switch-minimized QSD power architecture and a digitally auto-locked VCF control technique for direct 48V-to-PoL power delivery. Specifically, the QSD power stage comprised merely 6 GaN power switches, 2 flying capacitors and 2 power inductors, facilitating simplified control strategy and high current-density and ensuring robust power conversion with high efficiency. Overall, the proposed 6-switch QSD (6S-QSD) hybrid power converter demonstrates a 90.6% peak efficiency over a wide output range up to 10A. Thanks to the device-efficient topology, this work reports a compact 48V power solution of 0.0214 inch3 volume, which leads to a remarkable current density of 1,158 A/inch3. To prevent the destructive power device breakdown, a fully digital auto-locked VCF control technique is also introduced. The measured results show that the unbalanced VCF error is substantially suppressed by 95.5%, from 4.5V to 0.2V at 36V input voltage, effectively eliminating the devices’ over-stress issue, thermal breakdown and system malfunction.