Design and Control of Tunable Piezoelectric Transformer Based DC/DC Converter

Piezoelectric transformer is an alternative for magnetic transformers in power converters. Specifically, tunable piezoelectric transformer (TPT) is a recently developed device that has input, output, and control ports. When connected with different impedance at the control port, TPT has different voltage gain characteristics. In this paper, it is proposed to use this property for output voltage regulation while keeping constant switching frequency. To illustrate this concept, this paper introduces the working principle and characteristics of the TPT. A closed-loop control scheme is proposed, where the regulation is done by a duty cycle controlled switched capacitor at the TPT control port. Design of the converter implementing the proposed control scheme is presented. A converter with a 100 W TPT is constructed and tested, which shows the state-of-the-art performance and limitations of TPT based converters.