| 摘要 |
PROBLEM TO BE SOLVED: To prevent the breakage of a high frequency voltage generation circuit, and the like by an abnormal voltage in an inverter type ballast. SOLUTION: An output voltage Ed of a power supply circuit 10 is converted into a low voltage Ea by a zener diode D1, and the voltage Ea is supplied to a drive circuit 52. A thyristor SCR is connected in parallel to the zener diode SCR. A snubber circuit SB composed of a resistor R7 and a capacitor C7 absorbing abnormal voltage generating in a switching element Q2 is connected in parallel to the switching element Q2 forming the output portion of a high frequency voltage generation circuit 50. A voltage generated in the resistor R2 is detected by a voltage detection circuit 40, and when the detected voltage is not in a predetermined range, the thyristor SCR is turned on so as to stop voltage supply to the drive circuit 52. Thereby, the operation of the high frequency voltage generation circuit 50 is stopped so as to prevent the occurrence of an abnormal voltage. |
