Although there exist very high bandwidth optocouplers, I’ve found many IGBT/MOSFET drivers still use pulse transformers for isolation. Why is it the case, when we know that optocoupler has no need for number of turns calculation, winding, etc. and is easier to assemble and does not require extra latch/Schmidt trigger circuits. Someone told me pulse transformer gives better and more reliable Isolation, is it the case?
Thanks for replies in advance

 

It is an interesting question. What is your experience with either method?

 

I would suggest three reasons:

1) Pulse transformers were about LONG before opto-couplers.

2) Pulse transformers are much more reliable.

3) A pulse transformer can actually transfer power, simplifying the secondary circuit.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

4) you need alot higher isolation then commercial opto's provide thus winding yr own can provide this
5) you have silly design rules that say "tho shall not use opto-electronics"

__________________
Nothing is impossible.
Once a problem is realised, the rest is just details

 

Not only simplifying the secondary circuit but it can also eliminate the need of aditional isolated power supplies to feed the optocoupler's output

__________________
E Cerfoglio
Buenos Aires
Argentina

 

The LED in opto-couplers fades with time so the output becomes less and less. A transformer doesn't.

__________________
Uncle $crooge

 

I suspect that opto-isolators have replaced pulse transformer in many applications, but there may always be cases where the transformer may have advantages as already stated and say where you require a center tapped secondary so that two 180 degree out of phase signals are available.

Lefty

__________________
Measurement changes behavior

 

Thank you all. Besides, pulse transformers are bidirectional, you can send PWM and receive fault signals via the same transformer (in the form of very short duration impulses).

 

Why hasnt anyone stated the most obvious reason.

Opto-couplers cannot provide AMPS of gate current to switch a power device fast. A pulse transformer CAN.

 

Haven't you read the third post in the thread?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Can they be use for communication say RS 232 ??

 

Optocouplers can of course. But this has nothing to do with the topic at hand.