Output module for industrial control with sink and source capability and low heat dissipation

摘要

An I/O circuit for use with an industrial controller provides a photovoltaic optical isolator communicating between a controller and a field-side of the I/O circuit, the photovoltaic optical isolator eliminating the need for high wattage power dropping circuits for powering the field-side of the I/O circuit from high-voltage field signals. The field effect transistor type transistors permit use of the low-power photovoltaic optical isolator while allowing flexible connections to various field circuit types.

主权项

1. An I/O module circuit for use in an industrial control system comprising:
a housing; terminals supported by the housing for receipt of electrical power to be controlled by the I/O module circuit; and a circuit contained in the housing providing: at least one field effect transistor having a source and drain in series between the terminals to control current flow through the terminals according to a first electrical signal received by a gate of the field effect transistor; an input supported by the housing receiving a second electrical signal indicating a desired control of electrical power at the terminals of the I/O module; a power isolator receiving, at a first controller-side, the second signal and providing at a second field-side output power and the first signal communicating information of the second signal; an active pulldown transistor connected between the gate of the at least one field effect transistor and the field side of the power isolator; and a diode separating the field side of the power isolator from a connection of the active pulldown transistor to the gate of the at least one field effect transistor, wherein a control input of the active pulldown transistor is connected to the field side of the power isolator on one side of the diode and the connection of the active pulldown transistor to the gate of the at least one field effect transistor is on the opposite side of the diode, and wherein the output power is derived from input electrical power received at the first controller-side of the power isolator but isolated and floating with respect to that input power; and therein the first signal is isolated and floating with respect to the second signal.