Dual PWM relay driver with diagnostics for functional safety system

摘要

A component includes first and second switches in series and connected between a power source and a coil of contacts of a safety relay. A first controller controls the first switch with a close signal that closes the first switch or a first PWM signal that opens and closes the first switch on each PWM cycle. A second controller controls the second switch with a close signal that closes the second switch or a second PWM signal that opens and closes the second switch on each PWM cycle. A PWM sensing circuit connected to the coil sends a sensed PWM signal to an input of the first and second controllers. The first controller sends the first PWM signal while the second controller sends a close signal and vice-versa. The controllers verify that the received PWM signal matches the sent PWM signal.