Abstract Piezoelectric resonators are becoming attractive alternatives to conventional magnetics in DC-DC converters due to their favorable scaling and manufacturing properties. However, the efficiency and current handling capabilities of baseline piezoelectric resonator-based DC-DC converters degrade at higher voltage conversion ratios due to charge utilization limitations imposed by topological operation. Here we present an Always-Multi-Path Embedded Flying Capacitor Piezoelectric Resonator-based DC-DC converter that uses flying capacitors to add both hybrid multi-path output power delivery features and to reduce the internal charge redistribution losses within the piezoelectric resonator. Specifically, the proposed integrated circuit modifies the optimal voltage conversion of the piezo network from 2:1 to 3:1 while adding a switched-capacitor output network that enables multi-path operation at all times, resulting in a net optimal voltage conversion ratio of 9:1 for the converter, with 4x improved output current. Fabricated in a 180 nm high-voltage CMOS process, the developed chip achieves a peak efficiency of 96.2% at a 48-to-4.8 V conversion ratio.
Ko et al. (Tue,) studied this question.