| 摘要 |
PROBLEM TO BE SOLVED: To improve circuit efficiency with a simple circuit constitution, and make it unnecessary to use an element of high withstand voltage by preventing a voltage of a capacitor for smoothing in the case of a light load from becoming higher than a voltage in the case of a rating load. SOLUTION: In one term, a control unit 10 makes a switching element Q2 turn on and off repeatedly while keeping switching elements Q1, Q3 in the state of OFF. In the OFF term, a switching element Q4 is made to turn on for a prescribed term in the case of a light load. In the other term, the switching element Q1 is made to turn on while the switching elements Q2, Q4 are made to turn off, and the switching element Q3 is made to turn on/off repeatedly. In the case of a light load, the switching element Q4 is made to turn on for a prescribed term while the switching element Q2 is made to turn off, forms a loop where a circuit of an LD, an IGN, a C2 and an L1 is connected with both ends of a parasitic diode of a switching element Q1, discharges energy stored in the inductance element L1 to a load LD, and decreases the current peak value of the inductance element L1. |
