Looking at the datasheet for the ZS1031-11(H) trigger coil, the test setup activates the trigger coil with a thyristor:

Trigger Coil Test Circuit from Excelitas

In the datasheets for other trigger coils, and in other circuit diagrams online, pretty much all of the circuit diagrams I can find also use a thyristor.

Why is a thyristor used here, as opposed to a MOSFET or an IGBT? What are the important considerations for this part?

Thank you!

  • \$\begingroup\$ Simplicity, robustness, price,... \$\endgroup\$ Jun 26, 2020 at 17:35

1 Answer 1


Your premise is wrong, IGBTs are very common in speedlights and some studio flashes. That allows the flash to be terminated early, leaving charge on the capacitor. Some IGBTs, such as Toshiba's GT8G131 are specifically designed for strobe applications.

It's not as important in a studio flash where you can charge the capacitor leisurely to a known voltage before discharging it with a thyristor.

Both devices are capable of handling a high pulse current, and withstanding hundreds of volts with a relatively small die size (compared to, say, a MOSFET). The IGBT has the advantage it can be turned off while still conducting substantial current.


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