| 摘要 |
<p>A circuit for protecting an electronic device from excessive voltages applied to an input or output terminal (14) includes a solid state relay (120) coupling the electronic device to the terminal (14). The solid state relay (120) may include an optotransistor (130) coupled between the electronic device and the terminal (14) and a light emitting diode (124) optically coupled to the opto-transistor (130). The solid state relay (120) is coupled in series with a current limiting device (18,24), such as one or more enhancement mode field effect transistors. A voltage detector (30) coupled to the terminal detects a voltage larger than a specific value and causes current to flow thorough the light emitting diode (124), thereby interrupting the coupling between the terminal (14) and the electronic device. The voltage detector (30) may be coupled between two spaced-apart connections to the coupling path between the terminal to the electronic device so that the voltage detector avoids diverting current from the coupling path.</p> |
