Full-bridge rectifier input reactance compensation in Megahertz wireless power transfer systems

It is attractive to achieve wireless power transfer with large spatial freedom by using a Megahertz system. For most systems, especially those working at kHz, the rectifiers are equivalently modelled as pure resistive loads when designing the compensated capacitors for coupling coils. However, the input reactance occurs when a rectifier works at high frequency, such as Megahertz. It can disturb the original circuit resonance designed without considering this reactance. This paper analyzes the input reactance for the full-bridge rectifier and evaluates its effects on the originally resonant coupling coils. A novel compensation method is proposed to eliminate the input reactance effects. Finally, a 6.78 MHz system is implemented in experiment. It shows that the compensation method can improve the system efficiency from 65% to 84% for the best case.