Negative Triac supply

[kaushalyas]

Hi, 

I have a requirement to drive a Triac from the MCU powered by a DC/DC converter. The AC supply is typ 24 VAC @ Rc terminal with respect to C terminal. The Triac is to be driven as attached. The MCU GND should always regulated at Rc - 3V3. The MCU output which drives the gate preferably will be connected straight, without the BJT. The gate current is II/III quadrants is typ 5 mA.

 

How do I configure a buck regulator and its input to achieve this?

Cheers,

Kaushalya

[Peter BENSCH]

Welcome @kaushalyas, to the community!

You may want to use a DCDC because you want to drive the triac negatively. However, it may be possible to implement the control in a simpler way. You will find hints on this in the application notes AN2986 and AN440, which may help you with the development. There is still the very old AN442, which refers to the obsolete 8-bit MCUs ST6, but the principle can also be used with modern MCUs like the STM32.

Hope that helps?

Regards
/Peter