A Spurious-Free Piezoelectric Resonator Based 3.2 kW DC–DC Converter for EV On-Board Chargers

Abstract

Piezoelectric power conversion has emerged as a promising technology for power-dense, efficient dc–dc conversion absent of magnetic components for energy storage. However, two practical challenges of piezoelectric devices have limited prototype demonstrations to relatively low power. First, spurious resonant modes plague low impedance resonator design, restricting operating load range, and lowering efficiency. Second, the mechanical nature of piezoelectric energy storage prevents traditional methods of removing heat. This work presents a spurious-free piezoelectric resonator design and a FOM for measuring a power resonator’s spurious modes. Additionally, this work develops thermal enhancements at both the piezoelectric device and converter level to improve heat extraction. These advances in acoustic and thermal performance overcome the challenges for moving piezoelectric power conversion to high power, demonstrated by a paralleled piezoelectric dc–dc converter capable of outputting 3.2 kW at 97.7% efficiency, and a piezoelectric resonator achieving a component power density of 5.7 kW/cm3.

Measured impedance and resistance of three electrode designs: square, circle, and ring. The ring design presented in this paper suppresses spurious modes, improving efficiency across converter load range.

Picture of the “heatsink” converter forcing air through four parallel converter fins.

Converter efficiency converting 450 V to 220 V.