Electronic trip unit of a circuit breaker

摘要

An electronic trip unit (20) which includes a processing unit (22) and a comparator circuit (24). The processing unit (22) receives an input voltage (VCC), and a reset signal (RESET) to reset the electronic trip unit (20), and generates a trip signal (TS) when sensed current of the electronic trip unit (20) exceeds a predetermined threshold. The comparator circuit (24) includes a first comparator (38) which receives the trip signal (TS) from the processing unit (22) and compares the trip signal (TS) with a predetermined reference voltage (VREF) determined based on the reset signal (RESET), and a second comparator (46) which compares a voltage generated by a power supply (11) with the predetermined reference voltage (VREF). The comparator circuit (24) determines whether the trip signal (TS) is for a valid trip event based comparison results of the first comparator (38) and the second comparator (46).