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I am a hardware developer. I have a requirement for designing a firing card for SCR. I am not very used to using thyristors and it has been a long time since I used one.

I see on the internet there are typically R, RC, and UJT circuits for the firing of SCR.

Can you tell me what circuit is typically used in the industry for robust design for SCR firing?

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  • \$\begingroup\$ You may want to ask a more specific question. There are hundreds more ways to fire a card. \$\endgroup\$
    – jay
    Commented Nov 6, 2021 at 13:16
  • \$\begingroup\$ SCR are fired with "power pulses". Depending of kind of SCR, kind of load, etc ... i.sstatic.net/ydjqG.png Sorry, in french \$\endgroup\$
    – Antonio51
    Commented Nov 6, 2021 at 13:22
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    \$\begingroup\$ I don't think UJTs have been used in decades; as far as I know, they aren't even manufactured anymore. \$\endgroup\$
    – Hearth
    Commented Nov 6, 2021 at 13:52
  • \$\begingroup\$ Yes ... UJT (very few models after 2N2646), after some years, was quickly replaced by PUT ... \$\endgroup\$
    – Antonio51
    Commented Nov 6, 2021 at 14:03
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    \$\begingroup\$ All industrial SCR boards I had ever seen, do use pulse transformers for the gate triggering and a train of pulses, if that's what you are asking for. \$\endgroup\$
    – Marko Buršič
    Commented Nov 6, 2021 at 15:46

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Here an example of such "drivers" : SCR is fired every 20 ms (50 Hz EU)

enter image description here

NB :

1- A guard angle ( generally 15-30 °) must be provided (firing angle no more then 150 degrees) ... especially in case of inductive load.

2- The simulation does not show the "synchronization" circuitry.

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