| 摘要 |
PURPOSE: To improve the lighting function of a discharge lamp immediately after lighting by supplying d.c. input to an inductance element at high intensity based on a start control signal immediately after lighting of the discharge lamp. CONSTITUTION: Though the lamp voltage VL becomes almost 0 immediately after lamp lighting, that the voltage of a connection point P3 lowers to near 0 is delayed by a capacitor C2. That is, the voltage of the connection point P3 is kept as high as the voltage VL before lighting. As a result, even after lighting, the condition before the lighting is retained immediately after lighting. Consequently, a Zener diode ZD1 is electrically conductive and a SW element Q2 is put in ON state and voltage of a connection point P2 becomes higher than that of a connection point P1 and rather than a stabilization control signal S1 from an IC 1, a start control signal S2 from an IC 2 is sent prior to a control circuit 5. In this way, the SR element Q1 is limited more by the current limiting level by the signal S2 which has a higher current limit level than current limiting level of the signal S1. |
