Opto-coupled devices

                                    Opto-coupled devices
 

Devices that are used in the control of high voltage/high power equipment need to have good electrical insulation between their high voltage output and low voltage input. Relying on a layer of silicon a few atoms thick to provide the required insulation, is not really an option in such conditions. When faults occur (and they are more likely to do so in high power circuits) the results can be catastrophic, not only to the circuit components but also to the users of such equipment. Physical isolation (meaning that there is no electrical connection at all between the input and output) is what is needed. Fortunately there are easy and cheap solutions to this problem. High power circuits are often controlled by "Opto−electronic devices" such as Opto−Triacs, Opto−Thyristors and Solid state relays.

The materials used in the manufacture of Triacs and SCRs, like any semiconductor device, are light sensitive. Their conduction is changed by the presence of light, that´s why they are normally packaged in little chunks of black plastic. However, if a Light Emitting Diode is included within the package that shines its light on a light sensitive semiconductor housed in the same I.C. package, it is possible to control a high power device in response to a very small input current through the LED, without having an electrical connection between the two.

 

                     Solid State Relays