Piezoelectric Filter Module Used in Harmonics Elimination for High-Efficiency Piezoelectric Transformer Driving

Switching driving, such as pulse width modulation, has been used in many power circuits because of its high efficiency. However, given the capacitance of a piezoelectric transformer (PT) for high harmonics in a square waveform, using switching technology directly in a driver circuit is difficult without an inductance linked with the PT. This paper proposes a design of a piezoelectric filter module for eliminating harmonic frequencies in the driving of a PT. Compared with a traditional inductor filter, the performance, cost, and space advantages make the module a wiser choice. The particular design of several PFs fabricated on one piece of piezoelectric plate has future integration potential with the transformer. The third harmonic filtering experiment shows that the module exhibits excellent performance on the elimination of harmonics and improvement of the whole converter's efficiency, making the large inductor for wide-range damping of harmonics unnecessary. Efficiency analyses for a simplified push-pull power amplifier model prove the existence of an optimum output waveform for a tradeoff consideration on the circuit efficiency and driving complexity of a PT. This study offers detailed guidance for the future development of novel converter circuits.