Re: Interupting xenon flash current ?
- From: Jim Thompson <To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx>
- Date: Wed, 05 Dec 2007 11:24:24 -0700
On Wed, 05 Dec 2007 12:52:21 -0500, Mike <nomtrxspam@xxxxxxxxxxx>
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 was going to try interupting the pulse, but the only IGBT I have is one I
took from a dead microwave oven inverter and it's only rated at 150A for 1ms. My test setup isn't all that
powerful, only about 37J (600uf flash cap charged to 350v). I'm also curious about why it takes 20us from the
time of the HV trigger to the time the tube starts to conduct. It may not be, but that just seems like and
awfully long time. Not enough trigger voltage maybe? Also, it takes another 15us for the current to reach
it's peak. Unfortunately I don't have any data for the flash tube. It is fairly large, 80mm long and 8mm dia.
The trigger is a thin wire spirally wrapped the entire length of the tube.
Mike
If there is no absolute truth then nothing can be known.
I did that in the '60's, but used an SCR, read my patent at...
http://analog-innovations.com/SED/Pat-3496411.pdf
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
.
- Follow-Ups:
- Re: Interupting xenon flash current ?
- From: JosephKK
- Re: Interupting xenon flash current ?
- References:
- Interupting xenon flash current ?
- From: Mike
- Interupting xenon flash current ?
- Prev by Date: Re: LCD Voltage Meter Module Source
- Next by Date: Re: Interupting xenon flash current ?
- Previous by thread: Re: Interupting xenon flash current ?
- Next by thread: Re: Interupting xenon flash current ?
- Index(es):
Relevant Pages
|
