Piezoelectric transformer for cold cathode fluorescent lamp inverter

A piezoelectric transformer of which the structure differs from the Rosen-type structure was investigated. According to the aim of reducing the heat generation of the piezoelectric transformer, the relationship between the heat generation and vibration velocity of the transformer was investigated. The temperature of the transformer rapidly rises when the vibration velocity of the transformer increases to above a critical value. Based on analysis of the electrical equivalent circuit of the piezoelectric transformer, the vibration velocity of the transformer is proportional to the output current and inversely proportional to the force factor of the output part. As a result, new piezoelectric transformers with a strip electrode at the output part which can minimize the heat generation of transformers have been developed. The inverters with these 3, 6 and 10 W piezoelectric transformers showed more than 85% efficiency at 60-80 kHz driving.