PIEZOELECTRIC TRANS-INVERTER CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a piezoelectric trans-inverter circuit capable of preventing the break of a piezoelectric transformer in case of a disconnection between a piezoelectric transformer and a cold cathode or in case of a broken cold cathode. SOLUTION: When voltage divided from the output voltage of a piezoelectric transformer 1 is equal to or above the upper limit reference voltage of a voltage detection circuit 7 for the piezoelectric transformer 1, a voltage-frequency conversion circuit 5 is controlled to operate the piezoelectric transformer 1 to give output voltage equal to or lower than a set voltage. In addition, a drive circuit 6 is stopped when the output voltage of the piezoelectric transformer 1 is equal to or less than the lower limit reference voltage of the voltage detection circuit 7 for the piezoelectric transformer 1 and the output voltage of an error amplifier circuit 8 is larger than the reference voltage of an error amplification circuit voltage detection circuit 8.