Piezoelectric-transformer inverter with maximum-efficiency tracking and dimming control

This paper provides a solution for the problem of efficiency decrease caused by load variation and environmental temperature change. A novel control scheme of tracking the PT's operation frequency for the maximum efficiency is proposed. As a result, a high efficiency of over 80% has been achieved even under the output current decrease down to 10% of the maximum, and under the resonant-frequency variation by environmental temperature change of -10 to +70 centigrade.