Patent ID: 6198198
Filing Date: 2001-03-06
Classification: C02F,H02M,H05B

Abstract:
A piezoelectric transformer control circuit for switching an input DC voltage by a driving circuit to generate an AC voltage, and driving a piezoelectric transformer by the AC voltage to obtain a high AC voltage, comprising:a driving voltage detecting circuit for detecting a magnitude of a driving voltage to said piezoelectric transformer;a driving voltage error output circuit for comparing an output from said driving voltage detecting circuit with a first predetermined value and for outputting a voltage error result as an amplified comparison difference;a load current detecting circuit for detecting a magnitude of a current flowing in a load connected to said piezoelectric transformer;a load current error output circuit for comparing an output from said load current detecting circuit with a second predetermined value and for outputting a current error result as an amplified comparison difference; andan oscillating circuit for outputting an oscillation signal for switching the input voltage,wherein the oscillation signal is a rectangular wave, and said oscillating circuit including:a frequency adjusting circuit for adjusting a frequency of the oscillation signal in accordance with the current error result, anda duty ratio adjusting circuit for adjusting a duty ratio of the oscillation signal, which is output from said frequency adjusting circuit, in accordance with the voltage error result.