Patent ID: 7474064

Claim:
A lamp driving circuit configured for driving at least one discharge lamp, said lamp driving circuit comprising: a step-up transformer including a primary winding, and a secondary winding coupled electrically to the at least one discharge lamp and adapted to cooperate with the at least one discharge lamp to form a tank circuit that generates a tank current; a detector configured for detecting current magnitude of current flowing through the at least one discharge lamp, and outputting a first detecting signal that corresponds to the current magnitude detected thereby; and a controller coupled electrically to said primary winding of said step-up transformer, and to said detector for receiving the first detecting signal therefrom, said controller generating a drive signal for driving said step-up transformer; wherein said controller includes a capacitor, and further receives a current-setting signal, said controller configuring a waveform of the drive signal by controlling charging of said capacitor based on a first calculation value that corresponds to a frequency of the drive signal, a start-setting value, and a difference between the first detecting signal and the current-setting signal.