Power rail control systems that include power multiplexing circuits that include cross-current conduction protection are disclosed. Power multiplexing circuit includes supply selection circuits each coupled between a respective supply power rail and an output power rail coupled to a powered circuit. To maintain power to the powered circuit during switching coupling of the output power rail, but while also avoiding current cross-conduction path between supply power rails, diode drop control circuits are provided in supply selection circuits. In diode drop operation mode, the diode drop control circuit associated with a higher voltage supply power rail is configured to regulate voltage supplied by such supply power rail to the output power rail to power the powered circuit. A current cross-conduction path is not created, because diode drop control circuits associated with lower voltage supply power rails are reverse biased to prevent current from flowing through their associated supply selection circuits.