Modeling of a 2MHz GaN-Based Constant-On-Time Virtual-Ripple-Controlled 20A Buck Converter for High-Performance Computing Applications

High-performance computing (HPC) systems require power converters with fast transient response and high power density for advanced processors. This paper details the modeling and design of a 2MHz GaN-based constant-on-time (COT) buck converter utilizing a dual-path virtual-ripple control (VRC) strategy. Designed for HPC applications, the converter delivers a 1.2V, 20A output from a 5V to 12V input. The VRC architecture emulates inductor current ripple for superior transient performance with low-ESR ceramic capacitors, while a complementary slow path ensures precise DC regulation. GaN FETs enable high-frequency operation, critical for compact converter size and improved figure-of-merit (FoM). LTspice simulations validate the design’s superior transient performance, managing a 19A load step at a 5A/µs slew rate with only 21.3mV of voltage undershoot and a 5.6µs recovery time. This represents a 4x reduction in voltage droop and a 10x faster recovery compared to conventional valley-mode control. This design methodology and analysis offers a compelling solution for advanced point-of-load power delivery in next-generation computing platforms.