| 摘要 |
PROBLEM TO BE SOLVED: To provide a power source circuit for reducing a wasteful power to be consumed therein. SOLUTION: A DC power source 7 compares a voltage obtained by dividing a voltage Vu of a smoothing capacitor C by resistors R8, R9 and R11 with a predetermined voltage by an operational amplifier IC to open or close a switching element 6, when a voltage obtained by rectifying a voltage of a commercial power source 9 by a rectifying means 5 is charged in the capacitor C via the element 6 and outputs the voltage Vu having a predetermined ripple based on a hysteresis operation of the amplifier IC. Then, a control circuit 8 switches a level of one end of the resistor R11 to Low or High corresponding to a load amount of a load 10 to change a width of the ripple to increase the width of the ripple when the load amount of the load 10 is small to reduce an opportunity of turning on the element 6, thereby decreasing the power 7 to be consumed therein. |
