TRIAC Switching Trailing Edge

It's not feasible with TRIAC or SCR, they can only turn off at current zero crossing.

Hi,

nis2311 said:

But TRIAC turns off naturally at zero cross.

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more exactly CURRENT zero cross.

nis2311 said:

In this mode how to turn off the TRIAC before the zero cross.

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I simply won´t do it. Because it´s against the typical triac behaviour. The triac itself can´t be turned OFF, one needs external cirtuitry to reduce current to close to zero for the triac to turn off.
It surely can be done ... but the effort is rather high.

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nis2311 said:

Need to turn ON the TRIAC at starting

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At starting of what?
Starting of voltage? Then the gate pulse need to be long enough to ensure the current did rise to the holding threshold.
And in case you have not purely resistive load ... it becomes even more difficult.

nis2311 said:

and need to stop at 50% of duty cycle of the sine wave

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Sine wave has no duty cycle ... we talk about phase angle of voltage (or current) instead.
So did you mean @ 90° of voltage?

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All in all we could help you a lot more if we knew true application requirements and specifications.
Without use case and numbers ... all we can do is guess.

Klaus

Trailing edge dimmers are available on the market, usually implemented with anti-serial connected MOSFET.

Only specially designed "GTO" SCRs can be forced off while conducting. This needs a real strong gate shunt, active.

Butterfly that (in concept - structural reality differs) and you need two flying shunt switches that are OK with high reverse voltage, where's the supply / drive for that, yadda yadda.

Saw this on a forum :

you can turn off the TRIAC by short circuit TRIAC main terminals, connect a BJT in parallel to the TRIAC MT1 and MT2, just pulse the base of the BJT for a very short time to short the TRIAC then the TRIAC is off, remember if the current is very high use a power BJT.

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But does dV/dT negate this ?

SCR (commutation) :



Regards, Dana.

The link about SCR commutation has a method (among several) employing a capacitor in series with the load. The capacitor charges partway through each half-sine, halting conduction. Perhaps a similar method can be used with a triac. It requires careful selection of cap value and neighboring components.

FvM said:

Trailing edge dimmers are available on the market, usually implemented with anti-serial connected MOSFET.

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Hello FvM,

Can I get any reference circuit using two anti-serial connected MOSFET by controlling through any MCU or any specific topology is there? Please help me out of this problem?


Kind Regards,
Nishanth M

See e.g. https://www.st.com/resource/en/appl...tf17n62k3-power-mosfet-stmicroelectronics.pdf

A solid-state relay with a MOSFET bidirectional output should work for you.
What current rating do you want?