Re: Interupting xenon flash current ?



Mike wrote:

I was reading about how autoexposure and speed flash units work and found out that in modern units IGBTs are
used to turn off the tube current at the proper time. I scrounged up the parts to flash a tube and measured
the current pulse during discharge. For my test setup I measured the the current peak to be about 1900A and am
fairly certain that number is pretty close. The current was above 1000A for about 6us and still at 300A after
200us then finally decayed to 0 after about 600us. How is it possible for any reasonably priced/sized IGBT to
survive under that kind of stress?

I believe there is a mistake with your measurement. In the common cameras, the flash current is at the order of 100A and the duration is ~tens of milliseconds. They handle it with IGBT of SOT-223 form factor.

However there are the special pulse tubes for use with lasers, etc. They have higher rate of the current increase and the shorter flash duration.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
.

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