The present invention provides a switched-mode power supply circuit, comprising a boost inductor, a boost capacitor, an energy storage capacitor, a transformer or a DC-DC inductor, a first switch device, an output rectifier element, a filter capacitor, a feedback control circuit, a first rectifier circuit, and a second rectifier circuit. When the first switch device is turned on, the boost inductor, the boost capacitor, and the first switch device form a first boost loop, the boost inductor stores energy, and the energy storage capacitor, the first switch device, and the transformer or the DC-DC inductor form a first DC-DC loop. When the first switch device is cut off, the boost inductor, the boost capacitor, the energy storage capacitor, and the transformer or the DC-DC inductor form a second boost loop, and the transformer or the DC-DC inductor, the output rectifier element, and the filter capacitor form a second DC-DC loop. An output of the filter capacitor is connected to a load. The feedback control circuit drives the first switch device to turn on or turn off according to a chopped wave having a specific frequency and a duty cycle, so as to control a voltage, a current, or a power output to the load.