I'll work for the first time with a Hockey Puck type SCR with a high di/dt application. So far I've mounted it properly, with the proper clamp and heatsinks. Now I'm concerned with the gate drive, since this article is saying the following:
In respect to the second quote, I see that I have to apply a sufficiently high driving voltage, but I don't know which paramater in the datasheet I should look at.
This application note shows a graph of the gate current with steeply rising on-state anode current:
I assume the curve B occurs because there's a reverse gate-cathode voltage that's opposing to the applied one. Is that correct?
The datasheet of the device I'm working with has the following paramaters for gate:
As far as I understand, I should apply at least 3.5V (Vgt) to gate-cathode in order to trigger the SCR. But since I'm working with high di/dt, I should apply a higher voltage, but not higher than Vfgm (20V), as the previous article explains (I'm not sure if I got it right):
So, how high should be the voltage applied? Looking into another thyristor datasheet, with similar ratings, I've found that:
In the datasheet, it doesn't specify the Vfgm parameter, but it says that I should apply at least 30V in the gate. So, did I misunderstand the Vfgm parameter? Is that the maximum reverse gate-cathode voltage that occurs during the high di/dt anode current? And so decreases the gate current? If so, I must apply at least 20V.
Finally, is there any problem if I apply a constant current to the gate instead of this shape of the last image? Even if it's constantly strong (say, constantly applying Igm)? I know that there are some commercial gate drivers like this one but I'd like to use my own, using optocouplers.
The diagram of my circuit is similar to the following: