Is my design correct? Proteus simulates it but I need to change some values.

[Circuitmonster1032]

Hello everybody,

I'm designing a firing circuit for an SCR TIC106D, the datasheet shows a maximum Igt current of 200uA. But if I simulate it in proteus it doesn´t work as expected. Here are some screenshots of my design.

I still don´t have the real parts, so I can´t test it. Therefore I was wondering If this would work.


With this values the simulation runs and I get the expected waveform:


According to my calculations if the max gate current is 200uA I need a resistor of around 800K. If I enter this value in proteus the optocoupler is not activated.
Am I doing something wrong?

will appreciate your help,

Regards

 

[KlausST]

Hi,

You marked the thread as solved...

According gate current:
It's a bit confusing. The gate may withstand 200mA, but to trigger it needs max 0.2mA, so you should drive the gate with a current somewhere inbetween.

And it seems both scr are in series. Is this what you want? Maybe this causes some problems.

Klaus

 

[FvM]

The meaning of the waveform is unclear (which voltage shown, connected load, time base, applied trigger).

Why are you using a series connection of two SCRs? The shown circuit has a problem with negative cycles, the opto triacs can be triggered but the SCR doesn't. The SCR will be most likely damaged by high negative Vgk.

 

[Circuitmonster1032]

Thank you for your responses. Now I understand the gate current. I'm using them in series is because I'm trying to achieve a cycloconverter and I need current flow just in this section, I send pulses to specific scr in order to get a desired waveform. 30hz, 20hz, 15hz.

 

[Circuitmonster1032]

Now I got the parts and it's working!! well partially, I just did the first set of scr, Also I added a diode(thanks fvm) between the optocoupler and gate for each scr. I'm getting the desired waveform.