| 摘要 |
PROBLEM TO BE SOLVED: To start the switching operation of a switching element positively even if power is shut off and then is turned on immediately. SOLUTION: When power is turned on and a discharge lamp 4 is on, capacitors C1 and C3 are connected to the base circuits of transistors Tr1 and Tr2 in parallel and the base circuits are in a low-impedance state since the terminal voltage of a capacitor C7 is fully high, a transistor Tr3 is on and FET Trs 5 and 6 are on. At this time, when the power supply is turned off, the terminal voltage of the capacitor C7 drops, a zener diode ZD1 is turned off, the transistor Tr3 is turned off, at the same time the FETs Tr5 and 6 are turned off, the capacitors C1 and C3 are separated from the above base circuits, and the base circuits become high impedance simultaneously and immediately, As a result, even if power is turned on immediately, the transistors Tr1 and Tr2 perform smooth switching operation and continue operation. |
