Patent ID: 6903517

Claim:
A cold cathode tube driving device comprising: a piezoelectric transformer which outputs an output voltage varying depending upon a frequency of an input voltage to a cold cathode tube which is a load; a data converting device which detects electric current flowing through said cold cathode tube and converts the detected current amount into digital data; a smoothing process device which smoothes output data from said data converting device at a predetermined timing; an error voltage calculating device which compares smoothing data obtained from said smoothing process device with reference data and outputs error data corresponding to its difference; a frequency setting device which sets a frequency of said driving pulse on the basis of said error data; a frequency dividing device which divides a clock of a predetermined frequency and generates a driving pulse of an average frequency corresponding to the frequency data outputted from said frequency setting device in a distribution cycle which is N cycle period of said driving pulse; a controller which controls a control cycle so as to perform the same driving for predetermined number of times A (A≧2) at said average frequency; a burst pulse generating device which generates a pulse having a duty width in accordance with a dimming level externally applied thereto and having a frequency outputted from said controller; an output enabling device which turns on or off the output of the driving pulse from said frequency dividing device in accordance with the output value from said burst pulse generating device; and a power amplifying device which performs inversion with a switching by the driving pulse from said output enabling device and then outputs to said piezoelectric transformer.