A 100A 48-60V to 1V Hybrid LLC Resonant Converter with 51mV Droop for a 70A/20ns Load Transient

High performance multi-core CPUs and GPUs in data centers demand high current (>100A) and exhibit rapid load transients (>1000A/µs), posing significant challenges for existing 48V-to-1V converters, which often struggle to balance efficiency and transient response [1]–[4]. For example, hybrid converters [1] [2], which utilize switched capacitors to reduce voltage stress on power transistors, demonstrate improved peak efficiency, but also degrade transient response due to the limited slew rate of the inductor current. Moreover, these topologies require numerous switches and passive components, which compromise power density and result in poor efficiency at heavy load. On the other hand, LLC resonant converters leverage transformer to achieve the large voltage conversion ratios with zero-voltage switching operation, effectively reducing switch count and enhancing power density and efficiency. However, LLC converters have limited voltage regulation capability when adjusting the switching frequency away from resonance, and also suffer from poor transient response, as will be discussed later. A sigma converter introduced in [3] [4] attempts to improve regulation by paralleling a buck converter with the LLC converter, but its transient response remains limited. In this paper, we propose a hybrid LLC resonant converter featuring a transient enhancement phase to address the transient response challenges of existing LLC converters, while simultaneously achieving efficient 48-60V to 0.8~1V conversion with improved regulation.