FAULT-TOLERANT OUTPUT CIRCUITS

摘要

FAULT-TOLERANT OUTPUT CIRCUITS Circuit modules for providing digital or analog outputs from computational devices in such a manner that the components of the output circuit modules are tolerant of malfunctions in one or more of the components. In the digital output embodiment of the invention, output signals are independently derived using two voting circuits and are then applied to two switches connected in series to provide a fail-safe condition for most types of failure of the switches or the voting circuits. Two identical modules provide the ability to faithfully follow commanded on or off signals in all but a statistically small number of situations, and permit convenient replacement of a defective module without affecting output through the other module. In an analog output module, two independent voting circuits provide voted digital outputs to separate digital-to-analog converters, the outputs of which are compared to generate a validity signal that is used to control an output switch. The validity signal for the module can be combined logically with the switch status of another identical module, to determine which of the modules should be activated by closure of its output switch. An inactive module can be removed and replaced without affecting the integrity of the analog output signals.