A
cold cathode tube driving device using a
piezoelectric transformer in which an output
voltage varies depending on a frequency of an input
voltage, as a booster
transformer for driving a
cold cathode tube, includes: a frequency dividing means which generates a driving pulse of an average frequency corresponding to
frequency data outputted from a frequency setting means at a distribution cycle which is a driving pulse N cyclic period; a controller which controls a control cycle so as to perform the same driving for predetermined number of times A (A≧2) at the average frequency; and a burst pulse generating means which generates a pulse having a duty width in accordance with a dimming level externally applied thereto and having a frequency outputted from the controller.A control cycle is A times (natural number) the distribution cycle and the driving is performed A times at the same average frequency, whereby a digital driving
system using the frequency distribution of the driving pulse is achieved. Consequently, a space for the
driving circuit can be saved and cost can be reduced. Further, a frequency
distribution system is adopted, thereby obtaining
frequency resolution required for satisfactory dimming performance and lighting performance. Moreover, a burst dimming
system is adopted, thereby suppressing brightness
flicker seen in a tube current
control system. Additionally, there is no
electric power loss seen in a
system in which a power source is turned on or off and further a shield circuit is unnecessary because of a system in which the driving pulse is turned on or off. In particular, the control cycle is A times the distribution cycle and the burst dimming is performed in which the driving is executed A times at the same average frequency, whereby the brightness
flicker can be prevented by controlling the tube current to be constant with high dimming resolution assured.