| 摘要 |
PROBLEM TO BE SOLVED: To suppress power consumption and improve efficiency in a circuit by making the value of the voltage of an energy accumulating means for supplying energy to step voltage generating means at a trough part of an ac power voltage agree with the peak value of an output voltage on a side higher than discharge characteristic of a discharge lamp. SOLUTION: A lamp current is large, and the voltage of discharge lamp characteristics is low, when a discharge lamp fully lights up. When attempting to light stably, ratios of high and low periods becomes close, a voltage VdcF of a smooth capacitor C0 is set as low as a voltage equivalent to three capacitors, and a capacitor for power conversion requires only three switching elements for switching control to effectively utilize the elements. When modulated light lights up, a lamp voltage is low and a characteristic voltage is high. A rate of a high applied voltage period is smaller than that of a low applied voltage period. Thus, a voltage VdcD of the smooth condenser C0 is set so that a control range for preventing a discharge lamp failure is set higher than a maximum voltage, and switching elements are effectively used to reduce power consumption and provide stable lighting. |
