POWER SUPPLY, DISCHARGE LAMP LIGHTING UNIT AND LIGHTING FIXTURE

摘要

PURPOSE: To prevent the input current from an AC power supply from being distorted through simple circuitry without causing any trouble in the output circuit. CONSTITUTION: An output control circuit 23 delivers oscillation signals a1, b1 to first and second switching means 21, 22 which are thereby turned ON/OFF alternately and the ON duty ratio thereof is controlled based on the output voltage from a rectifier circuit 12. At the time of deep dimming, the output control circuit 23 decreases the ON/OFF frequency of the first and second switching means 21, 22 and increases the ON duty ratio of the second switching means 22. Consequently, the input current from an AC power supply can be prevented from being distorted through simple circuitry without causing any trouble in the output circuit.