| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply which reduces power consumption during standby and prevents noise in a standby power supply.SOLUTION: A switching power supply comprises a main power supply 10a and a standby power supply 10b. In a standby state; a standby power supply control circuit 24 turns to be in an on-state to make a transformer T3 supply power supply voltage to a set control circuit 28, and the set control circuit 28 performs off-control of a switch 30 to make a main power supply control circuit 18 be in an off-state. In a power supply on-state; the set control circuit 28 performs on-control of the switch 30 to make the main power supply control circuit 18 be in an on-state to make a transformer T1 output power supply voltage, and a standby power supply control feedback circuit 26 and a threshold adjustment circuit 40 make the standby power supply control circuit 24 be in an off-state depending on the output from the transformer T1. |
