| 摘要 |
PURPOSE:To reduce the wasteful power consumption and stabilize the intensity without depending on the characteristics of a lamp to be lighted. CONSTITUTION:The tube current Io flowing in a lamp 3 is detected by a current detecting dimming circuit 44 as voltage Vb, the voltage Vb is corrected by the voltage Vin of a DC power source 1, and the voltage Vb is negatively fed back to a chopper drive control circuit 45 to drive and control a chopper circuit 46. The voltage Vin is interrupted by the chopper circuit 46 and applied to bases of driving transistors 471, 472 of an inverter circuit 47 as a bias. The applied voltage to the drive circuit of the inverter circuit having little power consumption is controlled, and the power loss can be sharply reduced. The brightness change of the lamp 3 due to the fluctuation of the inputted DC voltage and the fluctuation of the applied voltage of the lamp 3 can be prevented, and the lamp 3 can be invariably lighted at the prescribed brightness. |
