scr causes transients

pager48

Joined Nov 25, 2018
161
this simulation has 400v at gate of SCR. Its large enough to damage something.

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Bordodynov

Joined May 20, 2015
2,907
See

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Alec_t

Joined Sep 17, 2013
12,206
The gate-to-cathode voltage is less than the gate-to-ground voltage, but still excessive in the sim. A gate-to-cathode capacitor (of even a few pF) should help to reduce that.

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Alec_t

Joined Sep 17, 2013
12,206
I was editing my post while you were posting. Even 0.01pF added gate-to-cathode is enough to pull the gate-cathode spike down to ~4V, so perhaps the spike is an artifact of the thyristor model.

Alec_t

Joined Sep 17, 2013
12,206
Ignore my above posts. My sim was mis-behaving. The gate-to-cathode voltage is the important one and peaks at ~ 3.6V. The diode Bordodynov added needs to have a reverse voltage rating greater than the peak capacitor voltage.
Edit: Interchanging the load resistor and thyristor would avoid the high gate voltage and is the usual arrangement in a CDI (cap discharge ignition) circuit.

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