| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which makes a lamp hardly fade out when shifting toward dimmer state, in a small size at a low cost. SOLUTION: An alternating current power source is rectified by a rectifier circuit 5, and the output voltage of the rectifier circuit 5 is converted by a chopper circuit 1. Power is supplied to a lamp La through a chopper circuit 2, by making the output of the chopper circuit 1, the power source of the chopper circuit 2. The output voltage of the chopper circuit 1 is made variable by a control circuit 3, and the power supplied from the chopper circuit 2 to the lamp La is made variable by the control circuit 3. First, the control circuit 3 reduces the output voltage of the chopper circuit 1 when the lamp La is controlled so as to reduce the light output down to the requested value, but when the chopper circuit 1 becomes unable to maintain the prescribed power factor, the control circuit reduces the power supply from the chopper circuit 2 to the lamp La. |
