magnetics question

[Michael Robinson]

A lot of people have built the circuit in this Home Power article.

http://alton-moore.net/graphics/desulfator.pdf

There's also an active discussion forum
http://leadacidbatterydesulfation.yuku.com/

In my opinion it's an elegant design, very creative, and maybe it could be
made even better.

Here is an equivalent circuit using an n-fet and reversing the polarity
overall (view in proportional font).
Nothing new there.

D1
,------+->|-+------,
| | | |
| ( ) |
| L1 ( ) L2 |
| ( ) |
| ( ) -----
| | | ---
| '--+-' -----
_| | ---
--||_ ---- |
| ---- C4 |
| | |
'---------+--------'


L1 and L2 are separate inductors. They are not linked.
I arranged them in parallel to illustrate something:
why not use magnetically coupled windings?


,------, ,------,
| | | |
| *( || )* |
| ( || ) |
| 1 ( || ) 2 |
| ( || ) -----
| | | ---
| '--+-' -----
_| | ---
--||_ ---- |
| ---- C4 |
| | |
'---------+--------'


The same pulse that appears at winding 1 when the mosfet turns off will
appear at winding 2.
This means you can pulse the battery without having to wait for a diode to
come out of reverse bias and start conducting.
(Of course, in a physical circuit you could have stray inductance and
imperfect coupling between the windings
so I might include D1, but I left it out of the drawing to get the idea
across.)

This brings up another question about an effect that I think magnetically
linked windings would have.
Would coupling the windings with the indicated polarity reduce ripple on the
capacitor, as compared to the original circuit?

I think that when the mosfet is on, current is ramping up in winding 1, and
the "back emf" in winding 1
that opposes the impressed voltage will be reflected into winding 2 and push
current into the capacitor node at the same time
winding 1 is drawing circuit from that node. Is my analysis correct?

 

[Michael Robinson]

"Michael Robinson" <nospam@billburg.com> wrote in message
news:S7iFn.906$yx.87@newsfe13.iad...

A lot of people have built the circuit in this Home Power article.

http://alton-moore.net/graphics/desulfator.pdf

There's also an active discussion forum
http://leadacidbatterydesulfation.yuku.com/

In my opinion it's an elegant design, very creative, and maybe it could be
made even better.

Here is an equivalent circuit using an n-fet and reversing the polarity
overall (view in proportional font).
Nothing new there.

D1
,------+->|-+------,
| | | |
| ( ) |
| L1 ( ) L2 |
| ( ) |
| ( ) -----
| | | ---
| '--+-' -----
_| | ---
--||_ ---- |
| ---- C4 |
| | |
'---------+--------'


L1 and L2 are separate inductors. They are not linked.
I arranged them in parallel to illustrate something:
why not use magnetically coupled windings?


,------, ,------,
| | | |
| *( || )* |
| ( || ) |
| 1 ( || ) 2 |
| ( || ) -----
| | | ---
| '--+-' -----
_| | ---
--||_ ---- |
| ---- C4 |
| | |
'---------+--------'


The same pulse that appears at winding 1 when the mosfet turns off will
appear at winding 2.
This means you can pulse the battery without having to wait for a diode to
come out of reverse bias and start conducting.
(Of course, in a physical circuit you could have stray inductance and
imperfect coupling between the windings
so I might include D1, but I left it out of the drawing to get the idea
across.)

This brings up another question about an effect that I think magnetically
linked windings would have.
Would coupling the windings with the indicated polarity reduce ripple on
the capacitor, as compared to the original circuit?

I think that when the mosfet is on, current is ramping up in winding 1,
and the "back emf" in winding 1
that opposes the impressed voltage will be reflected into winding 2 and
push current into the capacitor node at the same time
winding 1 is drawing circuit from that node. Is my analysis correct?

As I look at the circuit I see that the two windings can't have the same

number of turns. Then current from the battery through the mosfet would
just flow through both windings and the inductance would cancel, like a
common mode choke.
Gotta think which side would need more turns, if it could be made to work
this way.