Circuit device and method for driving piezoelectric transformer

Means for controlling a piezoelectric transformer comprising a transformer driver supplies a driving voltage to the transformer, the driving frequency of the voltage controlled oscillator frequency. Load current monitor, monitors the load current flowing through the load supported by the transformer as a fluorescent tube or the like. When the initial drive transformer, frequency sweep controller controls the frequency of the oscillator frequency decreases as the scan, this time, the predetermined frequency of the drive voltage to a predetermined lower frequency scan from a high frequency; after stable operation of the transformer, the controller continues to control the frequency sweep frequency oscillator, a frequency scan when the load current drops below a second predetermined value down to a first predetermined value.