I've a small question about TRIAC operation.

If I've a TRIAC with IGT=5mA, Ih=10mA and IL=20mA, driving an AC Load (230VAC 50Hz).

I know that if I send a 5mA pulse to the TRIAC gate, it will be ON until load current falls under 10mA.

I also know that if I send a 5mA pulse to the TRIAC gate, load current must be at least 20mA when I remove gate current to keep the TRIAC in ON state.

But what's going on when I continuously power gate with 5mA ? Does the TRIAC able to provide less than 20mA (or 10mA) to the load ? Or Ih/IL are absolute minimal current going through the TRIAC ?

Many thanks for your answer and sorry for my bad English.

  • \$\begingroup\$ Remember that a triac can operate in different quadrants (polarity of \$A_1\$ and \$A_2\$) and implies different drive currents. The following guide from ST offers a good overview of triac parameters and what they mean: st.com/content/ccc/resource/technical/document/application_note/… \$\endgroup\$ – Verbal Kint Jul 15 '17 at 8:41
  • \$\begingroup\$ Thanks for your answer. I've read that. In my case, I will work in QI and QIV (triac controlled by MCU). I also already read the documents, but I found the voltage limitation (VT) but not for current. \$\endgroup\$ – Damgot Jul 15 '17 at 9:29

When you maintain IGT at 5mA or higher continuously, the triac will stay on all the time, as the PN junction is still in ON mode. IH is only valid in the context of a triac working without IGT anymore.

On a side note, I recommend you use more than 5mA, because this is the current for 25 Celsius. Below this ambient temperature, you need to trigger with a higher current. I recommend you use 10mA for a 5mA triac.

I hope this helps.


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