Aspects of the present disclosure are directed to providing power from two or more power sources. As may be implemented in accordance with one or more embodiments, a switching circuit includes a switching transistor connected between a backup power supply and both a primary power supply and an internal power rail. When power is provided via the primary power supply, the switching circuit operates in a blocking state in which back current is prevented from flowing to the backup power supply while the primary power supply couples power to the internal power rail. When the primary power supply is disconnected or interrupted, a voltage coupled to a gate/control terminal of the switching circuit drops and the switching circuit automatically switches to another state in which the internal power rail is powered by the backup power supply.