A power switch is for interrupting an electrical circuit when current and/or current time span threshold values are exceeded. The power switch includes an energy converter, which on the primary side is connected to the electrical circuit, and on the secondary side provides an energy supply for at least one control unit of the power switch. The energy converter has a core having a remanence flux density (Br2) of less than 30% of the saturation flux density (Bs2) or a coercive field strength (Hc2) of less than 10 A/m.