Patent ID: 6153962
Filing Date: 2000-11-28
Classification: H05B

Abstract:
A piezoelectric transformer inverter, comprising:a piezoelectric transformer for converting an alternating voltage applied between its primary electrodes to an alternating drive current which is supplied to a load connected to a secondary electrode of the piezoelectric transformer;a driving frequency control circuit for controlling the frequency of the drive current so that the frequency of the drive current remains substantially constant;a chopper unit for supplying an alternating pulsed supply voltage having a frequency which is at least twice as high as the frequency of the load current applied to the load by chopping an input voltage applied thereto and for controlling the average value of the pulsed supply voltage by changing the duty cycle of the pulsed supply voltage; anda dimming unit for intermittently disabling the driving frequency control circuit by intermittently disabling the operation of the chopper circuit, said chopper unit being intermittently disabled at a frequency which is smaller than the frequency of the drive current;wherein signals having a duty ratio for allowing the chopper circuit to perform the chopping operation are sustained inside the chopper circuit during the period in which the dimming circuit is intermittently disabling the chopping circuit.