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From: El Loco Mateo on 29 Jan 2010 05:30
Hello,

I would like to build my own studio strobe, based on the following
design [I am well aware about the risks of high voltage/current!]:

http://www.diyphotography.net/diy-home-made-power-pack-flashes#great-idea

The only thing I would like to further implement is a control on the
flash duration/power. To my understanding, one has to replace the SCR
with an IGBT, in the triggering circuit. Could some one please confirm
this point?

Unfortunately IGBTs are new to me and I would really appreciate some
hints/tutorial on how to replace the SCR based trigger with an IGBT
based circuit?

Could someone here help me improve my knowledge please?

Best regards,

Mat'
From: osr on 29 Jan 2010 09:02
Fairchild has a application note on small IGBT controlled strobes.

Steve
From: MooseFET on 29 Jan 2010 09:19
On Jan 29, 2:30 am, El Loco Mateo <ellocoma...(a)free.fr> wrote:
> Hello,
>
> I would like to build my own studio strobe, based on the following
> design [I am well aware about the risks of high voltage/current!]:
>
> http://www.diyphotography.net/diy-home-made-power-pack-flashes#great-...
>
> The only thing I would like to further implement is a control on the
> flash duration/power. To my understanding, one has to replace the SCR
> with an IGBT, in the triggering circuit. Could some one please confirm
> this point?
>
> Unfortunately IGBTs are new to me and I would really appreciate some
> hints/tutorial on how to replace the SCR based trigger with an IGBT
> based circuit?
>
> Could someone here help me improve my knowledge please?


If you know about MOSFETs and bipolar transistors, you and think of an
IGBT as an N channel MOSFET feeding a PNP transistor.


You need to apply a pulse to the gate of the IGBT that is about 10V
tall and lasts for as long as you want the current to flow. The gate
of the IGBT must be moved from near zero to the near 10V and back
quickly. Holding it high and low is the easy part.

The IGBT must be in the path of the current through the tube. You
can't control the tube via the trigger electrode once it is fired.
The plasma inside the tube is a short circuit. You need to open one
end connection of the tube by turning off the IGBT in that path.
From: El Loco Mateo on 29 Jan 2010 18:10
On 2010-01-29 15:19, MooseFET wrote:
> If you know about MOSFETs and bipolar transistors, you and think of an
> IGBT as an N channel MOSFET feeding a PNP transistor.
>
> You need to apply a pulse to the gate of the IGBT that is about 10V
> tall and lasts for as long as you want the current to flow. The gate
> of the IGBT must be moved from near zero to the near 10V and back
> quickly. Holding it high and low is the easy part.
>
> The IGBT must be in the path of the current through the tube. You
> can't control the tube via the trigger electrode once it is fired.
> The plasma inside the tube is a short circuit. You need to open one
> end connection of the tube by turning off the IGBT in that path.

Thank you both for your comments! Is an IGBT the only solution to
achieve my goal? What other alternative do I have, should I want to
reach currents higher than say 150A?
From: John Fields on 29 Jan 2010 19:31
On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo <ellocomateo(a)free.fr>
wrote:

>On 2010-01-29 15:19, MooseFET wrote:
>> If you know about MOSFETs and bipolar transistors, you and think of an
>> IGBT as an N channel MOSFET feeding a PNP transistor.
>>
>> You need to apply a pulse to the gate of the IGBT that is about 10V
>> tall and lasts for as long as you want the current to flow. The gate
>> of the IGBT must be moved from near zero to the near 10V and back
>> quickly. Holding it high and low is the easy part.
>>
>> The IGBT must be in the path of the current through the tube. You
>> can't control the tube via the trigger electrode once it is fired.
>> The plasma inside the tube is a short circuit. You need to open one
>> end connection of the tube by turning off the IGBT in that path.
>
>Thank you both for your comments! Is an IGBT the only solution to
>achieve my goal? What other alternative do I have, should I want to
>reach currents higher than say 150A?

---
Not trying to be difficult, but are you sure you understand the comments
stating that in order to stop the discharge through the tube you must
interpose a switch between either the high or the low end of the tube
and what that end is connected to?

JF
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