PIEZOELECTRIC TRANSFORMER FOR COLD-CATHODE FLUORESCENT LAMP INVERTER

A piezoelectric transformer of which the structure differs from the Ro sen-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 wh en the vibration velocity of the transformer increases to above a crit ical value. Based on analysis of the electrical equivalent circuit of the piezoelectric transformer, the vibration velocity of the transform er is proportional to the output current and inversely proportional to the force factor of the output part. As a result, new piezoelectric t ransformers with a strip electrode at the output part which can minimi ze the heat generation of transformers have been developed. The invert ers with these 3, 6 and 10 W piezoelectric transformers showed more th an 85% efficiency at 60-80 kHz driving.