triac negative gate current

[spartekus]

negative gate current for triac

Hi all,

I need to do mcu based triac for inductive load. Microcontroller will decide when to open and close triac.
As much as i have learnt, there are 4 quadrants to drive triac. and fourth quadrant is not good. So it needs to be done with 2. 3. quadrants.

For that i need to give negative gate current to triac (please correct me, if i am wrong).
Does anyone know, how to create negative gate current for Triac, from Microcontroller?
Thanks a lot
Best regards

 

[schmitt trigger]

On a microcontroller, the usual way to power it is
Vdd= +5, and Vss =0 = common

To create negative current sourcing, it must be powered the other way around.
Vdd= 0 = common, and Vss = -5.

If this confuses you, there are Triacs which are specified to be triggerable in 4 quadrants, like these:
https://www.littelfuse.com/products/switching-thyristors/triac/qxx10xx-qxx10hx/q4010r4.aspx

The 4th quadrant trigger current will always be higher than the other three.

Or you can use a Triac optocoupler like the MOC3020 and trigger on quadrants 1 and 3.

 

[spartekus]

thanks for your answer.
i should use 3 quadrant i think, because of my inductive load.

Can i use optocoupler with a microcontroller(microcontroller will give order and optocoupler will create positive and negative impulse),
can it be done like on the photo below?(it will be then 1. and 3. quadrants)

 

[schmitt trigger]

Read the MOC3020 datasheet for the proper driving circuit and snubber.

There are optocoupler variants that require lower LED current (around 5 mA) to trigger properly. I would recommend to use those, to reduce the microcontroller's current output.