A power supply for a voltage or current-releasing switching device having at least one coil for one of a voltage and current release includes a device which activates a switch means in a pulse-width modulated manner, the device configured for setting the current flowing in the coil, wherein inductance of the coil functions as an impedor of a clocked power supply which, via a rectifier diode and a storage capacitor, provides a first supply voltage that is predefinable via a comparison value. A voltage regulation device provides at least one second supply voltage. A measurement-resistor-free regulation device is provided for setting the current through the coil.