Abstract: A power supply device includes a series arrangement of an inductance (3), a switching device (4) clocked by a control circuit (12), and a current measuring impedance (5), which series arrangement is arranged between two terminals (1, 2) to which a supply voltage (Ue) can be applied. A voltage (Um) appearing across the current measuring impedance (5) is applied via an input resistor 17to an input (18) of the control circuit (12) to control the switching device (4), a capacitance (19) being in parallel with the input (18) of the control circuit (12).A diode (20) is arranged in parallel with the input resistor (17), dimensioned in such a manner relative to one another that the diode (20) becomes conductive only when the Voltage (Um) across the current measuring impedance (5) exceeds a given limit value. Also, the ohmic resistance of the diode (20) together with the capacitance (19) forms a smaller time constant than the input resistor (17) with the capacitance (19).