Design and performance studies of a hybrid voltage regulator with improved energy efficiency

Transformer coupling in high step-down ratio voltage regulators (VR) improves their efficiency by extending the duty cycle, but results in poor dynamic performance because of their low inductor current slew rate and the leakage inductance of the transformer. Hybrid VR use an auxiliary buck converter in parallel with the main converter during load transients to improve the dynamic performance of the VR. The dynamic power loss in the auxiliary buck converter, however, severely affects the energy efficiency of the VR with increasing frequency of the load transients. This study presents the design and performance of a new control circuit proposed to minimise the dynamic power loss in the auxiliary buck converter of a hybrid voltage regulator consisting of an isolated full-bridge current doubler rectifier converter in parallel with an auxiliary buck converter. The results obtained from simulation and experimentation on a 9-19-V input, 1-V/30-A output, 500-kHz hybrid voltage regulator, designed according to the proposed method, show that the proposed control scheme significantly improves both the dynamic performance and the energy efficiency of the VR.