Resonant current estimation and phase-locked loop control system for inductorless step-up single piezo element-based (SUPRC) DC-DC converter

An FPGA-based control system for the step-up piezo resonator-based DC-DC converter is presented. An all-digital phase-locked loop (ADPLL) is used to self-start the converter and locks on to the resonant current, which is extracted using a current estimator. The PLL and several analogue comparator outputs are used to generate the gate signals for both MOSFETS. A new method is presented for determining the optimal high side switch duty cycle, which ensures zero-voltage switching on both MOSFETS. A practical converter is constructed, and experimental results presented, showing the effectiveness of the converter across a range of operating conditions.