A buck converter for converting a DC input voltage into a DC output voltage comprises a DC input circuit with a positive input terminal and a negative input terminal, for providing a DC input voltage, a converter circuit for converting a DC input voltage into a DC output voltage, and a DC output circuit with a positive output terminal, a negative output terminal and an output capacitor connected between the positive output terminal and the negative output terminal. The buck converter further comprises a switching device with a first switching terminal connected with the positive input terminal and a second switching terminal connected over a charging diode with the negative input terminal, a charging inductor as well as a frequency-dependent back-flow circuit connecting the positive output terminal with a power supply terminal of the switching device for supporting the power supply of the switching device.