| 摘要 |
PURPOSE:To hold a lamp at a constant voltage by furnishing a feedback circuit, making phase control of an inverter circuit, and putting the phase angle into correspondence to variation of the supplied voltage. CONSTITUTION:An inverter circuit is formed at the output end of a whole-wave rectifier 2, and a soft starting circuit A is provided at the base of a transistor 9 in this inverter circuit with a driver circuit C interposed. The voltage of a Iamp 14 is sensed by the secondary winding n3 of a high frequency stepdown transformer 12 and a circuit A operated by the output voltage of the rectifier 2. The circuit C controls the charging constant of a capacitor 6 in accordance with signals from the circuit A and a feedback circuit B. The phase angle at which a trigger element 7 overbreaks, is controlled with the time constant, and a transistor 9 in the inverter circuit is controlled. When the lamp is lit, the phase angle is controlled in compliance with the supplied voltage 1, and thus soft starting is accomplished. This prevents rushing or variation in the input voltage, and also excessive input and lack of the photo-output are suppressed. |
