A System Analysis of Solid State Switches with Software Controlled Circuit Protection Versus Electro-Mechanical Relays with Fuses or Circuit Breakers 2002-01-3134

Controlling electrical loads on vehicles have been a requirement since the earliest days of the automobile. Electrical load switching is normally accomplished using electro-mechanical relays, coupled with fuses or circuit breakers to protect the wiring of these circuits during electrical fault conditions. In the past decade, smart, solid-state field effect transistor switching components have been developed, in a commercially viable form, to perform this switching function with no moving parts. Circuit protection is employed in these devices through built-in hardware circuits and/or by simulated fuse functions performed in the software of a host controller. This paper uses a systems approach to establish the requirements of electrical switching in a vehicle, followed by examining the benefits and consequences of each switching technology. The comparative life cycle costs such as initial price, estimated switching life, durability to the environment, failure modes and diagnostic impacts shall be analyzed.