An Adaptive Synchronous Driving Phase Control Method of GaN-based Full-bridge 6.78MHz WPTS

The GaN-based active rectifiers have potential to improve efficiency of the several MHz wireless power transfer system (WPTS). The full-bridge active rectifier can eliminate extra dc-dc converters for output regulation with less voltage stress than resonant rectifiers, such as Class E, Φ rectifiers. However, the lack of the synchronous phase control method is the core challenge for full-bridge active rectifier in 6.78MHz WPTSs. Meanwhile, the increasing switching losses and reverse conduction losses of the gallium nitride high electron mobility transistors (GaN HEMTs) are the main constraints on the efficiency of the system. This paper proposes an adaptive synchronous driving phase control (ASDPC) method of the GaN-based full-bridge rectifier in 6.78MHz WPTS. With the proposed method, the full-bridge rectifier can obtain the maximum output power in the critical ZVS operation over a wide load range. A 50W 6.78MHz WPTS is built to verify the effectiveness and stability of the proposed ASDPC method. The dcdc efficiency is improved in the wide load range of 8Ω∼50Ω (11.8W∼54.57W) and reaches 87.18% at Po = 44.9W. Compared to the system without ASDPC, the efficiency can be improved by 5.2% at light load and 3.1% at heavy load