LIGHTING DEVICE OF DISCHARGE LAMP

摘要

PROBLEM TO BE SOLVED: To provide a lighting device of a discharge lamp which gives the same dimming curve up to lower limits at different lower limits of a dimming range. SOLUTION: The lighting device of a discharge lamp comprises a dimming control voltage generation circuit 3 and a dimming lower limit setting circuit 6. The generation circuit 3 is adapted to generate a DC voltage whose value decreases linearly with the increase in a pulse width of a dimming signal and also to output the voltage to an inverter circuit side as a dimming control voltage of the discharge lamp. The dimming setting circuit 6 which generates a lower limit control voltage to set a lower limit of dimming range of the discharge lamp based on partial pressures between resistances R4, R5 and diodes D2, D3 connected in series and is constituted so as to output the lower limit control voltage into the inverter side when the above control voltage decreases below the lower limit control voltage.