Abstract: A supply circuit and a switched mode power supply (SMPS) are provided. The supply circuit includes a first capacitor, a second capacitor, and a charging-discharging control circuit; the first capacitor includes a first terminal connected to a switching node, and a second terminal for providing a first supply voltage; the second capacitor includes a first terminal connected to a reference ground or a first potential terminal under control of the charging-discharging control circuit, and a second terminal for providing a second supply voltage; and according to a charging-discharging enable signal, the charging-discharging control circuit charges the second capacitor in a first time period and discharges the second capacitor in a second time period.