High Efficiency AC-adapter realized by Voltage-clamper with Mid-voltage AHB converter using Synchronous Rectification

The advent of GaN devices has intensified the competition to miniaturize AC- adapter size. Utilizing the high performance of GaN-FET to reduce size, power supply topologies are transitioning from the traditional flyback topology to the resonant topologies such AHB (Asymmetric Half-bridge Flyback) configurations. A previously proposed new concept of two converters combining a voltage-clamper circuit with Mid-voltage (MV) AHB converter with GaN-FET successfully reduced the converter size by half. However, it still faced the issue that efficiency is not improved and is still at the same level as conventional AC-adapters. This paper introduces the incorporation of a Synchronous Rectification (SR) circuit in a MV-AHB converter with optimization of the soft-switching condition which achieves higher efficiency. The MV-AHB converter has achieved 96.4% efficiency at input voltage of 160Vdc, and output voltage of 20Vdc /3.25A(65W) with 500kHz, (up from the previous 91%). Finally, a complete AC-DC converter board was built by combining the AC input section (including voltage clamper) with the MV-AHB converter, resulting in an overall efficiency of 93% .