| 摘要 |
A current supplied to a discharge lamp (100) is an A.C. current having a predetermined frequency from an inverter circuit (70), and its power control is carried out by changing the current setting (setting signal) of a chopper circuit (40) constituting a constant current circuit. In other words, when a value is set by an output luminance regulator (120), this set current value is inputted to a chopper control circuit (130). The chopper control circuit (130) checks the current detected by a current detector (110) and outputs a current control signal to a gate terminal (41) of the chopper circuit (40) so that the output current may coincide with the set current value. Accordingly, the power supplied from the inverter circuit (70) to the discharge lamp (100) is controlled by the chopper circuit (40). |
