A power supply employs an error detecting circuit to output an error signal when detecting an overvoltage or overcurrent occurred in one of output powers and employs a latch trigger circuit to cause the power supply to enter a latch mode when receiving the error signal. The power supply will keep the latch mode when entering the latch mode until the AC power VAC is removed. In addition, the power supply employs the error detecting circuit to provide the accurate safety threshold value by the constant current source with temperature compensation function and stable constant current output.