ORing diodes are used for power redundancy. In order to reduce the power loss due to the diode forward drop voltage, active ORing power MOSFETs are proposed to replace the diodes. With the active ORing controller and power MOSFETs, the power loss can be easily decreased by 90%. To make an N-channel MOSFET work like a diode when it is in reverse and have a very small forward voltage drop when it is in forward, an ORing controller is provided. Its offset, hysteresis, and propagation delay times are optimized for speed, stability, and noise immunity. Its ORing function is tested in an ORing demo board. Its FET check feature makes a live checkup of the ORing power MOSFETs to improve the reliability of the redundant power system.