# Forum: Analog Circuits HELP PULSE VOLTAGE FALLS

 Author: sirlakidis giannis (geosig) Posted on: 2013-10-30 18:37
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Good afternoon, everyone here, and congratulations on the work delivered
...
We need the voithia on a problem faced ..

Well in principle have a look at the schematic ..
guide two parallel-connected mosfet to drive an electromagnetic it takes
12 amp
with a pulse at regular intervals ..

the problem I presented is that the voltage +12 volt creates ladders ..
Look at the picture 2 ..

aware anyone here Experienced,help me how to stabilize them the
Thanks in advance .......

: Moved by Moderator
 Author: Rush (Guest) Posted on: 2013-10-30 18:52

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From my point of view, the 10000uF of the capacitors are not sufficient
to supply the current the pulse draws from the powersupply. Take in
mind, that for the time the MOSFETs are powered the supply sees some
what like a short circuit. So the internal resistance of the pwr supply
is very high compared to the inrush current of the coil.
And the capacitors are not able to support the pwr supply as needed.
You have to improve:
First the pwr supply, so that it can source more current in a short
period of time to withstand the short of the pulse from the coil and to
recharge the capacitors.
And second, add more capacity to the capacitors.
Search this forum for "powersupplies" to find the correct formula to
calculate the capacity. The user MaWin has plenty of knowledge to this.

Hope, that will help you further.

 Author: c-hater (Guest) Posted on: 2013-10-30 19:36

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sirlakidis giannis schrieb:

> the problem I presented is that the voltage +12 volt creates ladders ..
> Look at the picture 2 ..

What did you expect?

Simply simulate this piece of shit and you'll (hopefully) understand
what happens.

Hint: It's not required to simulate the whole driver stage to understand
what is wrong in this design. Replace it by simple pair of complementary
driven switches for simulation. This will speed up the simulation and
allows you to focus the core of the problem. Keep in mind: the impedance
of real world power supplies is never zero.

Did anyone ever calculate this shit before it was build? I'm afraid
none.

 Author: Rush (Guest) Posted on: 2013-10-30 19:49

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c-hater schrieb:
> this shit before it was build?

Ack!

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