Re: GDT --> Optron

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

>Why not using an optical coupler? Simple and
>reliable............... No headache with transformers..
>What do you think??????????

Some people do use optos. Terry Fritz designed a nice driver for his 
DRSSTC around the Toshiba TLP250. They are very popular in variable 
speed drives etc. where the gate drive waveform contains a low 
frequency component that a ferrite transformer can't handle.

But my own opinion is that for SSTC use, a transformer works better 
and is actually simpler to make, once you take into account the need 
for a floating DC supply and high current booster on the other side 
of the opto. (the TLP250 has the booster built in though.)

A ferrite transformer is also a lot cheaper than four fast 
optoisolators: you can buy a nice ferrite ring for about 2 dollars. 
Regular optoisolators like the 4N35 are far cheaper, but they are way 
too slow for SSTC work.

I'm currently w orking on IGBT brick drivers, and even for these I 
chose to use transformer isolation (along the lines of Steve Ward and 
Dan Strother's design) instead of optos. The page is somewhat out of 
date, I must get round to updating it.

http://www.scopeboy.com/tesla/drsstc/brickdriver/

Steve Conner
http://www.scopeboy.com/