Nonlinear processing of the output voltage of a piezoelectric transformer

Reducing the size of power supplies raises the problem of new components that could be better candidates for integration. In this field, electromagnetic transformers may be replaced with significant benefit by piezoelectric transformers (PT). In a PT, the input electrical energy is transferred to the output by an acoustical means, using the direct and converse effects of piezoelectric materials. Its main advantages over an electromagnetic transformer are no magnetic noise generation, small size, high power density, and high efficiency. This paper deals with an innovative technique that produces a significant improvement of the power capability of piezoelectric transformers. This technique is based on a particular output voltage processing of the PT. Its effect is a vibration level reduction of the PT structure while keeping the output power practically constant. Vibration level is a critical parameter that determines the maximum power capability of a given PT. Thus, the new processing reduces significantly the losses of the PT. Both theoretical predictions and experimental results show that the increase of the power capability may reach 200%.