JAJU858 December 2022
For safety reasons, detecting the output voltage of the relay and contactor is critical. The contacts can experience arcing and become fused together, providing power to the plug even when not powered by the system. Checking that the operation completed correctly is important and is to be done every time the relay is opened.
This reference design showcases ultra-low standby isolated AC/DC auxiliary power stage followed by ultra-low IQ as well as cost-optimized converters and linear regulators, comparator-based control pilot interface to meet SAE J1772 standard, efficient relay and contactor driver design, and digital isolator based line voltage sensing to detect fusing of relay and contactor contacts due to arcing.