US Patent 7973533 In-circuit testing for integrity of solid-state switches

A switching and fault detection circuit comprises two controllable switches capable of coupling a power source to a load. A controller can control the switches and test them for faults, and a voltage sensor can read the output voltage going to the load. Dual-redundant switches and fault detection circuitry can provide correct operation if one should fail. Control and feedback logic can determine if each of the solid-state switches is operating correctly during the power-on and power-off cycles and can also check for a fail-open condition during normal operations. If it is determined that a solid switch has failed open or closed, a fault can be generated.