| 摘要 |
PURPOSE:To permit an accurate starting operation of a lamp as load voltage, especially referring to no-load secondary voltage, is not lowered even in a light adjusting state by adjusting feedback signals corresponding to load current, depending on light adjusting signals. CONSTITUTION:Signals corresponding to load current flowing through an electric discharge lamp 17 are detected by an amperometric transducer, and applied to one of the input of a calculating machine 19 via a variable impedance element 23. To the other input of the calculating machine 19, signals corresponding to load voltage in an inverter circuit is inputted from a secondary coil N4 of an inverter transducer 11. The calculating machine 19 adds these signals to input the same into a drive control circuit 21 as control signals, on the basis of which the switching frequencies of switching elements 3, 5 are provided with variation and others to adjust output in the inverter circuit. Thus, the output in the inverter circuit is controlled so that the summation of the load current and the load voltage can be constant, and a lighting device having a constant-power output characteristic can be obtained. |
