Switching power supply circuit and computer power supply

The invention provides a switching power supply circuit. The switching power supply circuit comprises a transformer, an input circuit, an output circuit, a control IC, a feedback loop and a management circuit. The feedback loop is connected between the control IC and the output circuit and transmits a feedback signal to the control IC through a photoelectric coupler, and the control IC controls the input circuit to work according to the feedback signal. The input end of the management circuit is connected with a control signal sent by a computer system, and the output end of the management circuit is connected with the photoelectric coupler; the management circuit adjusts current flowing through the input end of the photoelectric coupler when receiving the control signal, so that a signal received by the feedback end of the control IC reaches the limit value and a PWM signal output by the output end of the control IC is switched off. Compared with a traditional power circuit, a photoelectric coupler used for transmitting a control signal sent by the management circuit is omitted, so that the circuit is simple, and the problem that PCB arrangement is difficult when multiple photoelectric couplers are adopted is solved.