Re: Interupting xenon flash current ?

On Thu, 06 Dec 2007 09:18:20 +1100, John Tserkezis
<jt@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

John Larkin wrote:

The IGBT itself will limit the current. And waste some energy, I
assume.

This isn't a case of "current limit". It actually does indeed interrupt the
flash tube current abruptly.

That's the only way that modern flash can work predictably, controllably and
repeatably.

I looked into this (for a non-commercial application) some time back and
couldn't find any off the shelf (one piece) semis that could do it. I
couldn't find any specific data on the way it was done, so suspected they used
two devices, an SCR as per normal, and a more traditional semi switch to turn
it off after the predetermined delay.

A couple of people make ICs that do the whole function: flyback
converter, trigger stuff, IGBT gate driver with timing.


Shunt igbt, wastes energy:

http://focus.ti.com/lit/an/slva197/slva197.pdf


Series:

http://www.onsemi.com/pub/Collateral/NCP5080-D.PDF


There are several others.

John



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Relevant Pages

  • Re: Interupting xenon flash current ?
    ... flash tube current abruptly. ... two devices, an SCR as per normal, and a more traditional semi switch to turn ... converter, trigger stuff, IGBT gate driver with timing. ... In looking at the data sheet and their demo board info, I see they are dealing with an 80A pulse with only 1J ...
    (sci.electronics.design)
  • Re: Interupting xenon flash current ?
    ... John Larkin wrote: ... flash tube current abruptly. ... That's the only way that modern flash can work predictably, ... I couldn't find any specific data on the way it was done, so suspected they used two devices, an SCR as per normal, and a more traditional semi switch to turn it off after the predetermined delay. ...
    (sci.electronics.design)