| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power unit capable of implementing an operation at an optimal switching frequency corresponding to an input voltage.SOLUTION: The switching power unit is configured to output an output voltage to a load by performing a switching operation of a switching element Q1. The switching power unit includes: a brown-in/brown-out circuit 14 which functions as an input voltage detection circuit for detecting an input voltage of a commercial AC power source AC; an error amplifier which compares the output voltage with a reference voltage and sends an error voltage to a primary side as a feedback signal V; and an internal oscillation circuit (OSC 12) which selects any one of a plurality of frequency reduction settings in accordance with the input voltage detected by the brown-in/brown-out circuit 14 and uses the selected frequency reduction setting to execute a frequency reduction function for reducing a switching frequency of the switching element Q1 at a light load time in accordance with the feedback signal Vreporting a state of the load from a secondary side. |
