Triac Ripple Voltage T1250H-6I (with schematic)

JSper.1 · ‎2026-04-17

Hello

I am currently developing an AC switch for a heating boiler in a coffee machine.

The boiler has a power rating of approx. 1200W.

To control the boiler, I have opted for a triac circuit (T1250H-6I) with an optotriac (14230634300) and ZCC. I used Application Note AN5114 to size the resistors. The description is generally excellent. However, I have a question regarding the voltage ripple on the triac. The note recommends a value of 4V. I cannot achieve this value with the standard resistor values available. My calculations give a voltage ripple of approx. 25V. Is that too much? Or what can I do to get down to the recommended value of 4V, triac with lower Igt?

Best regards
John

JSper.1 · ‎2026-04-20

Hi Peter
Yes, you’re right. Thanks so much for your excellent help. I’ll start with this setup, build the hardware and do some tests. I can always change the components afterwards. The circuit topology is the same, anyway.
Do you have any final tips for me on triac circuits? :)

Peter BENSCH · ‎2026-04-20

If you do not require the highest level of isolation with VDE0884 etc., you could also consider the STSID140-12. This thyristor and TRIAC driver has a number of advantages over classic optotriacs, including:

reliable internal magnetic isolation
no degradation like an optoisolator, whose CTR becomes smaller over time
excellent EMI noise immunity (saves the expensive and space-consuming X2 capacitors required for EN55016)
board space savings with a compact and very small DFN package
much simpler schematics
can drive all four quadrants (although in your case, the TRIAC can only do three)

These bullets are explained in detail in this product presentation.

This device is the first representative of this kind; further ones with interesting parameters will follow.

There will also be an evaluation board for it soon: STEVAL-SID140V1, which also has switchable zero-crossing detection and processing, although this can only be implemented sensibly with unipolar thyristors.

Regards
/Peter

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