| 摘要 |
PROBLEM TO BE SOLVED: To shorten the period of time during which large stress is applied to a switching element having an inverter circuit when power supply from an AC power source is stopped. SOLUTION: A power source circuit 4 for supplying an operation power to a control circuit 3 is constituted with a resistance R1 , a zener diode ZD, a capacitor C4 , a diode D3 , and a current amount switching circuit 5. The current amount switching circuit 5 is constituted with a parallel circuit of a resistance R2 and a series circuit of a resistance R3 and a switch SW2 . During low load operation, the switch SW2 is turned on, current I2 necessary and sufficient to pre-heat and start is supplied, and during lighting, the switch SW2 is turned off, and the supply amount of the current I2 is reduced to a degree necessary and sufficient to keep lighting. The period of time from stopping of power supply from the commercial AC power source Vs to stopping of the operation of the control circuit 3 by a reset circuit is shortened to shorten the period of time during which large stress is applied to switching elements Q1 , Q2 . |
