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How to Design Isolated Comparators for ±48V, 110V and 240V DC and AC Detection (Rev. A)

 

Many industrial applications need to monitor DC and AC voltages in the range of 48V to 300V. Examples include power supply and battery monitors, and receivers of status signals from sensors, switches and relays. Isolation is needed to handle ground potential differences and to protect against high voltage. The traditional solution for AC detection is to use a bridge rectifier followed by a Zener diode and an optocoupler. For DC detection, the same circuit is used without the bridge rectifier.