Input circuit for industrial control with low heat dissipation

摘要

An I/O circuit for use with an industrial controller provides an input circuit with low power dissipation through the use of a series connected substantially nonresistance impedance. An AC waveform input activates a light emitting diode (LED) bridge to provide an optical signal which illuminates a photosensitive solid-state switch thereby providing optical isolation between the industrial controller and the controlled process or machine. By using a series connected substantially nonresistance impedance, reduced current demand by the input circuit may be realized, which allows reduced power dissipation. As a result, the same circuit allows receiving input signals over a greater range, such as 120 volts AC and 240 volts AC, and allows significantly smaller components with closer spacing for a more compact design.

主权项

1. An I/O module circuit for use in an industrial control system comprising:
a housing; a terminal supported by the housing for receipt of an AC waveform; and a circuit contained in the housing providing: a series connected substantially nonresistance impedance comprising an inductor, the series connected substantially nonresistance impedance for receiving the AC waveform and limiting the current of the AC waveform; an optical isolator comprising a light emitting diode (LED) bridge coupled in series with the series connected substantially nonresistance impedance and operative to transmit light only when the magnitude of the voltage of the AC waveform is greater than a threshold, and having a photosensitive solid-state switch for receiving light from the LED bridge to provide an optically isolated signal.