| 摘要 |
<p>PROBLEM TO BE SOLVED: To avoid increasing the size of a smoothing capacitor, to reduce the cost, and to obtain a lamp light intensity early enough in a lamp control device providing a lamp lighting voltage through the smoothing capacitor. SOLUTION: After an input voltage Vin is rectified by a diode bridge DB1, and is smoothed by a smoothing capacitor C1, a lamp lighting voltage is supplied for a lamp 1 through a step-down type chopper circuit. A constant voltage circuit 4 controls an output voltage Vo to be constant by detecting the output voltage Vo. In this process, an input voltage to the copper circuit is detected, and if the detected value is low, a PWM control circuit 8 controls a drive of FETQ1 which is a switching element for the chopper circuit to restrict the output voltage Vo to the lamp 1.</p> |
