The invention provides a switching power conversion circuit, in order to convert voltage and supply the voltage to the load; the switching power conversion circuit comprises: a power circuit, which comprises a switch circuit and a first magnetic component; through the connection or the disconnection of the switch circuit, the power circuit converts the input voltage to the output voltage; a feedback circuit, whose input end is connected with the output end of the power circuit, and which is used for generating feedback signal according to output voltage; and a control circuit, which is electrically connected with input end of the switching power conversion circuit, the switch circuit and the output end of the feedback circuit, and is used for controlling the connection or the disconnection of the switch circuit, wherein, the control circuit fixes the time length of the disconnection of the switch circuit, while, the time length of the connection of the switch circuit is adjusted according to the feedback signal, and the time length of the connection of the switch circuit is limited in the maximum time length according to the value of the input voltage. When the switching power conversion circuit is in action, the internal components can normally run without burnthrough. And the load current at the load can be accurately controlled.