| 摘要 |
PURPOSE:To eliminate the generation of unnecessary light radiation and make possible optimization of light quantity control to the subject of a short distance by flowing the current recharging a commutating capacitor to the specified route right after cutting-off of an element which controls a discharge lamp. CONSTITUTION:The discharging current of a main capacitor MC at right after the turning-off of a switching element SW1 flows so as to charge a commutating capacitor CC and a commutating charge accumulating capacitor Cd to the polarity opposite from the initial one by way of a switching element SW2 having an impedance sufficiently lower than that of a discharge lamp Xe, resulting in that no current flows to the lamp Xe at all. Hence, the light emission time of the lamp Xe coincides with the period since the element SW1 conducted and the lamp Xe started emission until the element SW2 conducts and the element SW1 is cut off, thus accurate light quantity control is made possible. |
