An oscillator generates a triangular wave signal whose inclination for charging a capacitor and inclination for discharging the same are the same and which is used to turn on/off FETs Qp1 and Qn1. A signal generation part generates first drive signal in a period shorter than a half period of the triangular wave signal to drive the Qp1, and generates a second drive signal having a pulse width substantially equal to that of the first drive signal and a phase difference of about 180 degrees with respect to the first drive signal, to drive the Qn1 and provide a current to the discharge tube in a direction opposite to the current driven by the first drive signal. Furthermore a pulse current generation circuit converts a synchronization pulse voltage signal into a pulse current that alternates between positive and negative current values.