| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of reducing voltage stress applied to a circuit component during low load operation such as starting operation of a discharge lamp. SOLUTION: An AC power source Vs is full-wave rectified with a rectifying circuit DB, the output of the rectifying circuit is converted into high frequency output with an inverter circuit INV, and the high frequency output is supplied to a discharge lamp La. A control circuit CN is constituted with a frequency control circuit 21 for controlling the oscillating frequency of switching elements Q1 , Q2 , a driving circuit 22 for driving the switching elements Q1 , Q2 , and a constant current source 23. The frequency control circuit 21 detects both ends voltage VC5 of a capacitor C5 by current IR1 flowing in a resistance R1 , and controls so that oscillating frequency fSW becomes high with increase in input current Iin inputted in an input terminal. The resistance value of the resistance R1 is set so that the value of the current IR1 flowing when the AC power source Vs is rated voltage is I1 . |
