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Why triac driver circuits use NON ISOLATED POWER supplies???
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Dhanushka:
Dear all,
I am confusing whether why triac driver circuits use non isolated power supplies instead of SMPS, transformers in washing machines, remote controlled fans etc.
Is it cheap or other reason?
It is not safe as I think.
Thanks.
brabus:
In order to trigger the TRIAC you need to be synchronous with the line phase (zero crossing), so it's convenient to tie the system to the non-isolated side of things. As long as the load does not require isolation (which is the case by any mains driven load), and as long as the user interface is isolated (e.g.: a plastic potentiometer shaft), you're good to go! :-)
Ian.M:
TRIACs are inherently non-isolated as their gate drive must be applied with respect to MT1 which is part of the load circuit. Adding isolation adds cost, and *IF* there is no requirement for any user-accessible low voltage interface, rather than isolate the control circuit, its cheaper and easier to simply use an enclosure and controls that prevent physical access to any live part without the use of tools and meet the requirements for reinforced insulation.
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