A 99%-efficiency GaN converter for 6.78 MHz magnetic resonant wireless power transfer system

Abstract

The authors developed a high-efficiency gallium-nitride (GaN) Class-E converter for a 6.78 MHz magnetic resonant wireless power transfer system. A negative-bias gate driver circuit made it possible to use a depletion mode GaN high-electron-mobility transistor (HEMT), and simplified the converter circuit. As the depletion mode GaN HEMT with very small gate–source capacitance provided almost ideal zero-voltage switching, the authors attained a drain efficiency of 98.8% and a total efficiency of 97.7%, including power consumption of a gate driver circuit, at a power output of 33 W. In addition, the authors demonstrated a 6.78 MHz magnetic resonant wireless power transfer system that consisted of the GaN Class-E converter, a pair of magnetic resonant coils 150 mm in diameter with an air-gap distance of 40 mm, and a full-bridge rectifier using Si Schottky barrier diodes. The system achieved a dc–dc efficiency of 82.8% at a power output of 25 W. The efficiencies of coil coupling and the rectifier were estimated to be ∼ 94 and 90%, respectively.

Keywords

• inductive power transmission
• gallium compounds
• III-V semiconductors
• power convertors
• driver circuits
• high electron mobility transistors
• Schottky diodes
• rectifiers
• gallium-nitride Class-E converter
• GaN Class-E converter
• magnetic resonant wireless power transfer system
• negative-bias gate driver circuit
• depletion mode GaN high-electron-mobility transistor
• depletion mode GaN HEMT
• gate–source capacitance
• drain efficiency
• magnetic resonant coils
• full-bridge rectifier
• Si Schottky barrier diodes
• frequency 6.78 MHz
• efficiency 98.8 percent
• efficiency 97.7 percent
• power 33 W
• size 150 mm
• size 40 mm
• efficiency 82.8 percent
• power 25 W
• GaN
• Si