| 摘要 |
PURPOSE:To improve the reliability of the oscillation stopping control of an inverter when an abnormal condition is detected, in a lighting device of a discharge lamp to light the discharge lamp at a high-frequency by an inverter circuit. CONSTITUTION:An impedance element such as a resistance R12 is connected in series to the smoothing capacitor C8 of an abnormality detecting circuit, and the system has been set that the voltage value of the charging voltage of the smoothing capacitor C8 to which the voltage dropping component of the impedance element is superposed exceeds the yield voltage of a thyristor Q7 in an abnormal condition of the load circuit. By utilizing a high-frequency type of oscillation output of an inverter circuit, a peak voltage higher than the charging voltage of the smoothing capacitor C8 instantly is applied to the thyristor Q7, and the thyristor Q7 for holding the oscillation stopping condition in the abnormal detecting time can be turned on securely. |
