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Triac for blocking high frequency voltage

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mrinalmani

mrinalmani

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Hi
The figure attached depicts a scenario in which two solid state switches are used and only one is ON at a time.
The problem is that the transformers are high frequency transformers running at 100KHz. Back to back MOSFETs could be used to implement the switches, but I am thinking to use triacs.

I am looking at high dV/dt three quadrant triacs.
dV/dt of the transformer voltage is around 5kV/us. Maximum allowed dV/dt of the triac with gate open is 1kV/us.
How much improvement in dV/dt rating of the triac can be expected with its gate shorted to the anode terminal (by using MOSFET gate driver)? Will it be reliable to use a triac in such applications?

Thank you
 

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A Triac which works at 100Khz does not exist.
Triacs are powerline frequency (50/60 Hz) only. Perhaps 400Hz.

There are a few inverter-grade SCR which can switch up to 10 Khz. But those are SCRs, not Triacs.
 

5 kV/µs at 100 kHz sounds like a square wave. What's the actual voltage?

As schmitt trigger mentioned, switching speed of triacs is several orders of magnitude slower than 100 kHz. Limit switch spped doesn't necessarily exclude slow switching of high frequency signals. But a triac or SCR won't latch any more at 100 kHz.
 

Thanks for the reply.
The transformer output is nearly 400V square wave. Latching of current is not a problem since we can always provide continuous gate current just like in case of BJTs. Spurious triggering due to dv/dt is the real problem. I have had bad experience with triacs in the past. I was wondering if dv/dt rating could be improved by using regular MOSFET driver to drive triacs.
 

Latching of current is not a problem since we can always provide continuous gate current just like in case of BJTs.
Click to expand...
It might be a problem if you expect higher anode currents than a few mA. I must confess that I'm only guessing about the actual behavior. You would need to test it empirically. MOSFET switches are the straightforward way.
 

Thanks for the replies.
I have decided upon MOSFETs for the time being.
 

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