Abstract: A multi-range power supply unit with an automatic switchover between ranges for different power supply voltages is disclosed for use with devices such as circuit breakers or contact systems. The power supply unit preferably has only two input connections for an input voltage range of approximately 20V-230V. Between the two input connections there is a rectifier circuit with a voltage stabilizing element, such as a Z-diode or equivalent device, connected in parallel. Connected in series to the rectifier circuit is a current divider. The current divider includes a capacitance and a thermistor. The thermistor preferably has a positive temperature coefficient (PTC). The power supply unit can be used for a power supply with DC voltage and for a power supply with AC voltage.