Abstract: A DC power supply for an electronic switching element connected in series with a load in an AC main has a rectifying element and a capacitor parallel to the electronic switching element. Charging of the capacitor is provided by opening the switching element and diverting current from the AC main through the rectifying element and capacitor. The voltage difference across the capacitor powers control circuitry for the electronic switching element. Hysteresis built into the control circuitry results in the electronic switching element opening at a lower voltage difference across the capacitor than the voltage difference required to close the electronic switching element.