| 摘要 |
PURPOSE:To attain a low light flux dimming start of superimposing DC by providing a switching element, which controls DC power supplied to a discharge lamp, and generating a starting pulse of containing a DC component. CONSTITUTION:A secondary winding output of a high frequency transformer T2 is rectified by a diode D1 and smoothed by a capacitor C6 to obtain DC voltage. This capacitor C6 is connected to one end of a discharge lamp 1 through an inductance L1 and to the other end through a diode D2 and a MOS transistor Q3. A control signal of a comparator IC8 is supplied to a gate of the MOS transistor Q3 through a terminal (d) to superimpose DC power in the discharge lamp 1. A control signal, in which output voltage of a timer circuit IC2 is waveform-shaped by NOT circuits IC5, IC6, is supplied to the gate of the MOS transistor Q3 through a terminal (e) to provide a conduction condition at the time of starting the discharge lamp 1. In this way, a low light flux dimming start of superimposing DC can be performed. |
