Industrial process field device with low power optical isolator

摘要

An industrial process control field device includes a process variable transducer configured to sense or control a process variable. Field device circuitry is configured to couple to the process variable transducer and communicate information related to the process variable to another location. The field device circuitry includes an optical isolator having transmit circuitry on a first side of a galvanic isolation configured to transmit an optical signal which is pulsed on and off across the isolation. Receive circuitry is located on a second side of galvanic isolation and configured to receive the optical signal with an optical sensor. The optical sensor enters an “on” state when it receives a pulse and is otherwise in an “off” state. The receive circuitry provides a secondary side output based upon the received optical signal. The receive circuitry enters in a low power state when the optical sensor is in the “off” state.

主权项

1. An industrial process control field device, comprising:
a process variable transducer configured to sense or control a process variable; field device circuitry configured to couple to the process variable transducer and communicate on an industrial process control loop, the field device circuitry including an optical isolator comprising:
transmit circuitry on a first side of a galvanic isolation configured to transmit an optical signal across the isolation, the optical signal which is pulsed on and off; andreceive circuitry on a second side of the galvanic isolation configured to receive the optical signal and responsively provide a secondary side output based upon the optical signal, the receive circuitry including an optical sensor which enters an “on” state when it receives a pulse in the optical signal and is otherwise in an “off” state, and an amplifier coupled to the optical sensor which only amplifies the secondary side output when the optical sensor enters the “on” state to thereby reduce power consumption, wherein the receive circuitry includes a comparator which provides an output based upon an output from the optical sensor and the output from the optical sensor is AC coupled to the comparator to thereby reduce power consumption.