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.