This presentation deals with reliability of motor drive systems. It focuses on the switching power converter which is the weakest drive part. It investigates a new architecture which provides intrinsic redundancy. The method used in this fault switch detection and diagnosis is based on a sliding mode observer. The original aspect of this new approach is that the observer influences the control algorithm in order to rule out or accept the possibility of the device failure. This leads to the right decision which induces the rebuilding of the converter topology. This fault tolerant control strategy assures a limp-back operation.