Opto-coupled devices
Opto-coupled devices
Solid State Relays
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
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