SWITCHING POWER SUPPLY AND SEMICONDUCTOR DEVICE THEREFOR

摘要

PROBLEM TO BE SOLVED: To enhance the efficiency of power supply by a switching power supply without fail by reducing switching loss under light load to reduce power consumption through simple constitution. SOLUTION: A control circuit 15 includes an output load detection circuit 53 that converts feedback signals into feedback voltage signals VFBO indicating the state of a secondary-side load and outputs the signals; an error amplifier 22 that receives the feedback voltage signals VFBO at the inverting terminal thereof, generates error voltage signals VEAO resulting from the difference between the feedback voltage signals and reference voltages applied to the positive-phase terminal thereof, and outputs the signals; a switching signal control circuit 25 that controls switching signal output based on the comparison signals resulting from the comparison of the error voltage signals VEAO with element current detection signals VCL; and a light load detection circuit 40 that causes a switching signal control circuit 25 to stop the output of switching signals to a switching element 14, if the error voltage signal VEAO is lower than the lower limit voltage value.