I was trying to learn something about dimmers for light bulbs. After some reading, I found that most trailing edge dimmers contain some variant of this:
I do understand the general principle: No matter in which half wave we are, when the gate is pulled high, one of the MOSFETs lets current through to the other one which in turn lets the current flow because of its body diode.
But there are a couple of things I actually do not understand:
The signal could come from a µC, so there's no galvanic seperation between low DC and high AC voltage. Or is the insulation of the gate sufficient?
Even more confusing to me is the grounding between the MOSFETs. When the gates get pulled high, why does this not fry everything connected to that.
Why does nobody use an AC-optocoupler instead of this?