| 摘要 |
PURPOSE:To prevent flickering of a fluorescent lamp and dim light over a wide range by connecting a dummy resistance in parallel to a condensor when a phase-controlled voltage rectified by a rectifier is smaller than a predetermined reference voltage. CONSTITUTION:An AC voltage from an AC power source 31 is phase controlled by a dimmer 1. The phase controlled voltage is supplied as a DC voltage to an inverter 3 through a choking coil 25 and is converted to 24V so that an illuminating lamp 5 is lighted. A rectified voltage from a rectifier 9 is supplied to a Zener diode 15 via a resistance 11. When the rectified voltage is greater than the Zener voltage of the diode 15 a base current is passed through a Tr 17 via the diode 15 so that the Tr 17 is on while a Tr 21 is off. A dummy resistance 23 connected to the collector of the Tr 21 is not varied at both ends of the rectifier i.e., the parallel impedance of a condensor 7 is not varied when the Tr 21 is turned off. If the rectified voltage is smaller than the Zener voltage, voltages at both ends of the condensor 7 become smaller when the Tr 21 is on. |
