| 摘要 |
PROBLEM TO BE SOLVED: To prevent break of the switching element of an output circuit when controlling the output power of the circuit, when power supply is turned on or according to an output control signal from the outside. SOLUTION: An output circuit 5 supplies high frequency generated from a high frequency generating circuit 1 to an electrodeless discharge lamp 20, after amplifying the frequency by means of a switching element Q5. During a fixed period of time after DC power supply E is turned on, the output of a timer circuit 9 becomes higher in level, and the switching element Q3 of a short-circuiting circuit 6 is turned on. Consequently, both ends of the primary winding n1 of a drive transformer CT1 and the gate and source of the switching elements Q5 are respectively short-circuited to each other. Therefore, no pulse-like high voltage is generated across both ends of the induction coil 8 of the discharge lamp 20, and the stress applied to the switching element Q5 is reduced at the start of the output circuit 5. |
