Resonance-Based Wireless Energizing of Piezoelectric Components

A new technique of wirelessly transmitting electric energy to piezoelectric components is explored. The proposed method improves energy transfer efficiency by using the strongly coupled magnetic resonance as well as the mechanical resonance of the piezoelectric component. In the design, a printed spiral receiving coil connected across the piezoelectric component is used to capture energy wirelessly from the magnetic fields generated by a source resonator. Experimentally, the transmission of electric energy to the piezoelectric components is enhanced when the operating frequency of the generated magnetic field is close to the mechanical resonance frequency of the piezoelectric component. The power delivered to the piezoelectric component depends on the driving frequency, vibration modes of the piezoelectric plate, design, and separation distance of the source and receiving coils. At the resonant frequency 772 kHz of the piezoelectric component operating in the thickness vibration mode, a maximum power of 1.26 W and energy conversion efficiency of 48% have been achieved wirelessly by the piezoelectric component with an input ac source power of 2.6 W across the source coil and 4 cm separation distance of the source and receiver coils.