| 摘要 |
PURPOSE:To light a discharge lamp in an optimum state by controlling a time constant, which is to control the timing of the second switching means to control a switching means depending on the output of the secondary winding in a current transformer, depending on the output of the third winding. CONSTITUTION:The third and the fourth switching means are provided for turning the first and the second switching means OFF depending on the output of the secondary winding N22 in a transformer. Also, a time constant circuit to control the switching timing of the third and the fourth switching means and a control means to control the time constant of time constant circuits T1, T2 depending on the output of the third winding in the transformer are provided. In this way, if resonance current output from a drive transformer DT is increased, the oscillation frequency of an inverter circuit IN becomes high, so that the preheating secondary voltage of a discharge lamp L is prevented from abnormally rising to allow the lighting of the discharge lamp L in a short time after a power supply is made. |
