Galvanically Isolated MOSFET/IGBT Gate Drive

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
I just want to lower the need to put less semiconductors in the gate driver section so as to maintain lower semiconductor foot print and minimizing cost. And there is no need to worry about the driver being destroyed by Transient spikes.
 

Lestraveled

Joined May 19, 2014
1,946
The TS is right. Using an opto-isolator, with a mosfet gate driver, that is referenced to the source of the high side mosfet, that is pulsing 100 to 300 volts is a tough design. Also requires a regulator and at 100 to 300 volts will dissipate a lot of heat. An isolated transformer works also but that is extra parts. Controlling a high side mosfet at 300 volts is difficult, to say the least.
 

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
@Lestraveled

You are Perfectly Correct ,The reasons that you have stated are my current point of concern and I just dont wish to burn up my drives by using Semiconductor based Stuff.SO I opted Transformer based drive.
I have find some thing from Maxim App
 

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shortbus

Joined Sep 30, 2009
10,045
Guess I'll show more of my ignorance. How will a transformer prevent problems from the 'failure' in the IGBT side of the circuit? If a high enough voltage on the gate to destroy the driver should happen, won't that also go through a transformer? A higher than normal voltage at the secondary of the transformer would then make the secondary the primary, back feeding it, wouldn't it?

There are many industrial motor drives out there not using a gate drive transformer. But using a high voltage gate driver chip. Not only motor drives but welders, plasma cutters, inverters use them also. The IRF web site shows many of them. That is why there are so few gate drive transformer circuits out there today, below 600V they aren't needed.
 

cmartinez

Joined Jan 17, 2007
8,219
@Lestraveled

You are Perfectly Correct ,The reasons that you have stated are my current point of concern and I just dont wish to burn up my drives by using Semiconductor based Stuff.SO I opted Transformer based drive.
I have find some thing from Maxim App
Excellent document, I've just added it to my Mosfet drivers library. Thanks for posting!
 

PeterCoxSmith

Joined Feb 23, 2015
148
Hello Peoples,
I am working on a High Voltage MOSFET/IGBT gate driver that is to be used as a half bridge with independent control signal from a isolated source(M.C.U) . I need to drive high power IGBT 600v @ 100A .With a sampling frequency of 15khz to 25khz.
The main problem is the availability of off-the-shelf Isolated drivers and the huge cost involved to buy them.
Could some one through some light on a the Gate driver for our purpose.
you can get gate drive transformers integrated into gate drive module such as this:

http://www.analog.com/en/products/i...d-gate-drivers/adum3223.html#product-overview
 

Lestraveled

Joined May 19, 2014
1,946
Peter, that is a excellent part (ADUM3223) you recommended! Also, they are only $5 each in small quantities. I never thought about Analog Devices for this kind of part.
 
As we're discussing opto isolators driving power transistor gates. I have observed that for common units such as a 4n35, grounding the OPTO NPN base output via a 39K while driving a PNP stage into the GATE provides a significant cut in 'switch-off' latency. Around a 50uSec reduction! On the switch-on side the latency is just a few uSec.

It appears that the photo transistor gets 'hard switched' when it is not base biased resulting in a switch off slowdown common to hard switched bipolar transistors.
 
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