| 摘要 |
PURPOSE:To enable chopper light adjustment even when there is no signal input terminal for dimming and to achieve large variation in brightness through small input voltage variation by changing the duty of a chopper circuit according to the variation in an input DC voltage. CONSTITUTION:A power source voltage Vin is fed to a power source line 2 of a chopper circuit part 1, and is fed to an operation amplifier 3. The pulse of the duty corresponding to the operation amplifier input voltage, is output from a duty output part 4, in the chopper circuit part 1. A chopper circuit output 5 is changed along with the duty and a peak value to the variation in the power source voltage. The tube current flowing in an electric discharge tube 7 is changed by applying the voltage waveform to a DC/AC conversion part 6, and the brightness of the electric discharge lamp is changed. Since the duty and the peak value are both changed, dimming can be achieved to a large degree by small variation in the power source voltage. |
