A power supply circuit and a switched-mode power supply with a power supply input circuit are proposed. Known power supply circuits comprise a rectifier supplied with an AC voltage and a first smoothing capacitor. To provide a circuit which is suitable for operation over a wide voltage range, it is proposed that at least a second capacitor be provided which is connected by a switching element to the load terminals so that, when the voltage at the load terminals drops below a voltage threshold, the second capacitor is connected to the load terminals. Further embodiments comprise an apparatus for charging the second capacitor, which is preferably equipped with an apparatus for limiting the voltage at the second capacitor to a charging threshold. By suitable selection of the charging threshold, a capacitor may be used as the second capacitor which, despite a high capacitance value, exhibits a small structural size and low component costs due to the relatively low dielectric strength.
