DISCHARGE LAMP LIGHTING DEVICE AND LIGHTING SYSTEM USING IT

摘要

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device for preventing a load current from increasing in a region where a load voltage is low when a discharge lamp is abnormal without increasing a cost, and an illumination device using the same.SOLUTION: The discharge lamp lighting device includes a control circuit 5 which gives a drive signal to switching elements Q1 to Q5 corresponding to a result detected by a detection circuit 4 so as to control an output voltage of a step-down circuit 1 and a high-frequency voltage of a polarity inversion circuit 2 respectively. A minimum value Tonmin of an "on" duration Ton during which the switching element Q1 of the step-down circuit 1 is turned on and a maximum value Toffmax of an "off" duration Toff during which the switching element Q1 of the step-down circuit 1 is turned off are set for the drive signal. The control circuit 5 has a variable means 50 for changing the maximum value Toffmax of the "off" duration Toff of the drive signal corresponding to the result detected by the detection circuit 4, and the variable means 50 increases the maximum value Toffmax of the "off" duration Toff of the drive signal with a decrease in a load voltage La.