| 摘要 |
<p>PURPOSE:To prevent going-out of a discharging lamp by expanding an allowable range of D.C. current when the discharge lamp is started, and making an upper limit restriction strict during a fixed time after lighting. CONSTITUTION:Vo necessary for starting is ensured by raising an upper limit value of a duty cycle of a control pulse Ps of a control circuit 21 and relaxing an upper limit restriction of an output Vo of a DC pressure rise circuit 7 with an idle period control part 21 when battery 2 voltage is lower than a fixed value when a lamp is started in a lighting circuit 1. When lighting is made after that, this time, the upper limit of the duty cycle of the control pulse Ps is lowered and the upper limit restriction is made strict, power control below rated power with a supply voltage lowering detection circuit 18 is not performed until a given period elapses after lighting during a lamp unit condition is detected, and width of voltage drop of output in the D.C. pressure rise circuit 7 is restrained. Consequently going-out after once lighting is made can be prevented.</p> |
