PIEZOELECTRIC TRANSFORMATION TYPE COLD CATHODE FLUORESCENT LAMP DRIVING DEVICE

摘要

PROBLEM TO BE SOLVED: To restrict the pulsation by constantly maintaining the current value flowing in a cold cathode fluorescent lamp. SOLUTION: A variable oscillating circuit 1 generates the driving alternating current signal at a frequency near the resonance frequency of a piezoelectric transformer 5, and waveform of this output signal is formed into the nearly sine wave by a waveform forming circuit 2. Current or voltage of this output is amplified to a level enough for driving the piezoelectric transformer 5. Output of the drive circuit 3 is input to the piezoelectric transformer 5 through a resistor 4, and the output signal is applied to a cold cathode fluorescent lamp 6 for lighting. Even in the case where the impedance of the cold cathode fluorescent lamp 6 is lowered by the insertion of the resistor 4, since the piezoelectric transformer 5 can not supply a large current, the current value flowing in the cold cathode fluorescent lamp 6 can be maintained constant, and the pulsation of the current of the cold cathode fluorescent lamp 6 is restricted.