High-Frequency Bidirectional Resonant Converter for High Conversion Ratio and Variable Load Operation

Abstract

Applying RF circuit design techniques to dc-dc resonant converters has enabled switching frequencies well beyond 10 MHz, leading to higher power densities and faster transient response. Synchronous rectification is advantageous for low-voltage high-power applications but is challenging to implement in a high-frequency (HF) dc-dc converter. This article proposes an HF/very HF (VHF) resonant converter structure in which the rectifier and the inverter switches can be driven with the same gate signal. The presented structure enables efficient bidirectional power delivery in the HF/VHF range for applications that require a large voltage conversion ratio. A 64-MHz, 12-W, 36-12-V prototype converter verifies the operation of the structure. This article further explores an interleaved architecture of the same circuit to improve efficiency and transient performance. Finally, a 13.56-MHz 210-30-V prototype converter with 90% peak efficiency at 200 W demonstrates the advantages of the interleaved architecture.

Photograph of 13.56-MHz push–pull Φ22 prototype converter. (a) Top of the converter, including all the resonant passives and gate-drive circuits. (b) Bottom of the converter, four GaN FETs.