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LAN_403

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Wed Jul 09 2008, 08:51PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

Yeah, and a new DRSSTC project.

this drsstc will be the peak of my developement in driver technology. suited with a 4 channel optical toslink driver and seperate high side driver for each igbt. no more signal errors due to the extremely fast toslink technology which has a rise time of only 10nS!

an active overcurrent control unit on the front with a 12 led display for current and a rotary switch to adjust the max current for 100-1200A is the new standard. modulator input via toslink,.

the modulator is a highly complex unit. cause i want to use this drsstc for theatre and university etc, it has to be bulletproof. the modulator has an active on and off time control counter, completely digital to prevent failures. dont know the right design yet, but i have 3 weeks of time to find a way :P

the design is really straight forward. a nice case made of 19mm high density mdf safes the components. 2 big 120mm 230v fans with 30 watts for cooling the mmc and the bridge.

finally, the drsstc should look like this one i build a few months ago for the max planck insitute in hannover germany..

the circuit i developed for this drsstc will be used for the new one with a few changes. the driver electronic is completely optical, no need for a gdt etc.

two big skm200gb123D igbts for the fullbridge.

ha, that will be fun.

whenever i add new pics etc, iÂ´ll post it in this folder

here we go :)

Tonic

Wed Jul 09 2008, 11:08PM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

Say, what are benefits from switching to optical connections?

Mike

Thu Jul 10 2008, 12:11AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

well i have no actual idea but most people use opto isolaters to get rid of any type of interference. just a guess though.

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Thu Jul 10 2008, 08:14AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

First of all, optical connections cant pick up interferences nearby so the signal being send is clean.
cause this is my first drsstc with high side drivers, i thought it would be a good choice to use optical connections. for high side drivers you have to use a gdt or optocouupler for the signal fed in. and toslink is the fastest optical connection technique i could get. its not really cheap but i think its worth it. rise times of 10nS without the risk for interferences, without being affectet from the dense em field of a teslacoil etc. i think there are many good reasons why to use optical connections. another good reason, its really cool :)

Steve Conner

Thu Jul 10 2008, 10:24AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Better check whether TOSLINK have response down to DC or not. There have been threads about that on the board before. As far as I know, the receiver is AC coupled with automatic threshold control and its behaviour is undefined when the LED is off. Some of them go to zero, some spit out random noise.

I'm sure I remember some guy had to modulate his signal onto a 4MHz carrier to make it go down a TOSLINK, and Chris Fredin abandoned his thyratron Tesla coil altogether because of problems with the TOSLINKs. I read about this stuff and decided to use Agilent HFBR-24xx series instead.

Another gotcha is that the plastic package of a TOSLINK receiver might not stop EMI 100%. The signal at the photodiode is only microamps. Toshiba's appnotes actually warn about this. That was another reason I liked the HFBR-24xx, they are available in a metal housing that covers the diode completely.

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Thu Jul 10 2008, 12:24PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

i used this toslinks in my previous drsstc for the modulator without problems. had no problems with dc or other weird things such as undefined noise etc.
the totx 173/torx173 are complete ttl compatible toslink modules. with the led off there is no noise etc. the output is simply 0v. there is no duty cycle limit or something.

And steve, i wouldnt spend much money and effort into this project, when im not sure about the succees. im working on this circuits for month now, and im really sure, that this circuit will work without causing trouble. its been tested a few weeks ago on breadboard etc, so i know that it works.
Heres the new toslink high side brick driver.

GeordieBoy

Thu Jul 10 2008, 12:59PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

I'd also question the need for optical isolation with 10ns response times if your power semi's have something like a 600ns Â±300ns turn-on and turn-off delay?

Steve Conner

Thu Jul 10 2008, 02:01PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

That's cool that the part you're using is specified down to DC. I'm just mentioning that I've seen people bitten in the past by TOSLINK receivers that weren't specified down to DC.

My other warning about EMI with plastic cased receivers still stands.

teslacoolguy

Thu Jul 10 2008, 02:29PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

Dr. Conner wrote ...

My other warning about EMI with plastic cased receivers still stands.

Take the receivers out of the plastic case and then put aluminum tape on the inside of the case. I did this with my dc motor controller that has to run near a tc and it works without a problem.

Reaching

Thu Jul 10 2008, 03:31PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

mhh. why should a toslink receiver pick up noise ??
for sure, a gdt with a long connection cable can pick up noise too and no one talks about that. just put the gdt close to the igbts and connect them with a cable to the driver.

do you want to say that a 1x1cm small plastic package can pick up as much noise as a 30cm long gdt connection cable???

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