An OR controllers, also known as a diode-OR controller is a device that creates near ideal diodes using signal or back-to-back N-channel or P-channel MOSFETs. They are used in applications that require a low loss OR connection of multiple power supplies while minimizing the losses associated with the connection. This improves the efficiency of the system, lowers the power dissipated as heat and reduce the voltage drop across the 'OR'ing circuit.

 

Such applications include paralleled power supplies, uninterruptible power supplies (UPS), N+1 power supply redundancy and high availability systems. They are useful in any application where power supplies are switched or swapped. This includes hot insertion and hot swapping. They are good in applications where a primary power supply switches with a backup battery power supply. They are available in many configurations starting at 2 inputs to 1 output, and working up to many inputs to many outputs.

 

OR controllers work by sensing the input supply with respect to the load and will turn on the MOSFETs when the input supply is higher than the charging potential plus the small regulated voltage drop (typically around 15mOhms). They also incorporate under the over voltage detection and disable the MOSFETs under these conditions. Under voltage, conditions are usually managed using a hysteresis loop. The hysteresis level is typically configurable. The over voltage detection is generally filtered so as to not cause false triggering. They can also incorporate logic inputs to signal power fail conditions force switch over.