The invention discloses a standby zero reactive
power consumption control circuit in a
switching power supply, which comprises a main
control switch arranged between a PFC circuit in the
switching power supply and an
AC power supply network, and is characterized in that the main
control switch is switched off under the control of the
control circuit when the PFC circuit does not work; the controlcircuit is characterized by further comprising an auxiliary
control switch and a current-limiting
resistor, the auxiliary control switch and the current-limiting
resistor are connected in series and then connected to the two ends of the main control switch in parallel, and the
control circuit controls the auxiliary control switch to be closed for set
delay time and then controls the main control switch to be closed when the
switching power supply is connected to a load. According to the invention, when the switching power supply is connected to an alternating-current
power grid, the two ends of the main control switch are connected in parallel with the circuit formed by the series connection of the auxiliary control switch and the current-limiting
resistor, and then the auxiliary control switch is controlled to be closed, so that the current in capacitors, inductors and other devices in the PFC is saturated with small current due to the limitation of the current-limiting resistor; andthen the main control switch is closed to reduce the instantaneous current.