Patent ID: 6028388
Filing Date: 2000-02-22
Classification: H01L,H03B,H03L

Abstract:
A piezoelectric transformer driver comprising a drive circuit for driving a piezoelectric transformer, a frequency sweep oscillator for determining the drive frequency of the drive circuit, a load current comparator for determining the frequency sweep direction of the frequency sweep oscillator by comparing an output current carried by a load of the piezoelectric transformer with a reference level, and an output voltage comparator including a first and a second detector for detecting an upper and a lower limit level, respectively, of the output voltage of the piezoelectric transformer, the frequency sweep oscillator being operable, in a steady-state operation, to sweep the drive frequency to a higher or a lower frequency range side in dependence on whether the output current is higher or lower than the reference level and, when the output voltage becomes higher than the upper limit level, to sweep the drive frequency to the higher frequency range side by giving preference to the sweep direction determined according to the output current until the output voltage becomes lower than the lower limit level.