JPS6445088A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To lessen change of high-tension pulse voltage with respect to the voltage variation in a rectangular wave power supply by allowing a trigger circuit of a bidirectional SCR to operate in compliance with the end-to-end voltage of SCR, and by controlling the high-tension pulse for lighting-up. CONSTITUTION:In a trigger circuit of a bidirectional SCR 4, a series circuitry of a capacitor C10 and a resistance R12 is connected between a cathode and an anode of SCR 4, and a voltage response switching element 11 is connected between the junction of the C10 and R12 and the gate of SCR 4. At the time of operating, the C10 is charged by the end-to-end voltage of the SCR 4 through the R12, and when this charging voltage attains the breakover voltage of the switching element 11, it is turned on, and electric charges on the C10 are released via the gate of SCR 4 and the element 11 to turn off the SCR 4. Thus the voltage of the C7 is controlled in accordance with the output voltage of rectangular wave power supply 1, and variation of the high-tension pulse voltage for a discharge lamp 6 becomes small.