Abstract: A circuit includes a power supply end, a switching tube and a first loop connected to the power supply end in order, a second loop, and a load. The power supply end provides an input voltage for the circuit through a positive busbar and a negative busbar. The first loop includes a first capacitor, a first inductor, and a first freewheeling diode. When the switching tube is on, the first inductor is charged by the input voltage through the first capacitor; and when the switching tube is off, the first inductor discharges through the first capacitor and the first freewheeling diode. The second loop includes a second inductor coupled with the first inductor, a second capacitor and a second freewheeling diode forming a loop with the second inductor. The second capacitor and the first capacitor are connected in series.