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From: George Jefferson on 16 Jul 2010 05:57
I want to replace a CT full wave rectifier for a 200A+ battery charger with
a active rectifying system.

http://www.nxp.com/documents/data_sheet/PSMN2R5-30YL.pdf

Are some 100A 80W logic level fets which means I can parallel 3 or 4 of them
and increase the efficiency of the charger(there are other reasons for doing
it too).

I'll be driving the mosfets using a driver circuit instead of a uC of
course(just to reducing cross conduction problems).

In any case the real issue I have is how to do this on a pcb, if it is even
possible. Not only are the leads to the packages somewhat small I can't
think of any way how this can be done on a pcb(30oz pcb's?) or large solder
traces in any decent fashion.

Are thee any tricks to defeat mother nature or will I have to design some
special module that uses a copper bus bar like thing with the mosfets
soldered directly to it?

From: Uwe Hercksen on 16 Jul 2010 06:23


George Jefferson schrieb:

> In any case the real issue I have is how to do this on a pcb, if it is
> even possible. Not only are the leads to the packages somewhat small I
> can't think of any way how this can be done on a pcb(30oz pcb's?) or
> large solder traces in any decent fashion.

Hello,

there are some pcb manufacturers who can make pcbs with very thick
copper, about 300 �m instead of the usual 35 �m. You may even get pcbs
with normal and thick copper on both sides. You may need special thermal
pads for easy soldering. Just ask some manufacturers about pcbs with
thick copper for high currents.

Bye

From: Robert Baer on 16 Jul 2010 06:27
George Jefferson wrote:
> I want to replace a CT full wave rectifier for a 200A+ battery charger
> with a active rectifying system.
>
> http://www.nxp.com/documents/data_sheet/PSMN2R5-30YL.pdf
>
> Are some 100A 80W logic level fets which means I can parallel 3 or 4 of
> them and increase the efficiency of the charger(there are other reasons
> for doing it too).
>
> I'll be driving the mosfets using a driver circuit instead of a uC of
> course(just to reducing cross conduction problems).
>
> In any case the real issue I have is how to do this on a pcb, if it is
> even possible. Not only are the leads to the packages somewhat small I
> can't think of any way how this can be done on a pcb(30oz pcb's?) or
> large solder traces in any decent fashion.
>
> Are thee any tricks to defeat mother nature or will I have to design
> some special module that uses a copper bus bar like thing with the
> mosfets soldered directly to it?
Methinks you will absolutely need to use a copper busbar - and a
lotta FETs.
From: John Larkin on 16 Jul 2010 09:53
On Fri, 16 Jul 2010 04:57:11 -0500, "George Jefferson"
<phreon111(a)gmail.com> wrote:

>I want to replace a CT full wave rectifier for a 200A+ battery charger with
>a active rectifying system.
>
>http://www.nxp.com/documents/data_sheet/PSMN2R5-30YL.pdf
>
>Are some 100A 80W logic level fets which means I can parallel 3 or 4 of them
>and increase the efficiency of the charger(there are other reasons for doing
>it too).
>
>I'll be driving the mosfets using a driver circuit instead of a uC of
>course(just to reducing cross conduction problems).
>
>In any case the real issue I have is how to do this on a pcb, if it is even
>possible. Not only are the leads to the packages somewhat small I can't
>think of any way how this can be done on a pcb(30oz pcb's?) or large solder
>traces in any decent fashion.
>
>Are thee any tricks to defeat mother nature or will I have to design some
>special module that uses a copper bus bar like thing with the mosfets
>soldered directly to it?

This could be done on a pcb, but 200 amps is getting serious. The
problems will of course be getting rid of the heat from the fets,
getting rid of heat from the pcb traces themselves, and getting all
that current on and off the board.

Surface-mount fets aren't a good choice here, unless you are willing
to use a lot of them. They are hard to keep cool, and there will be
current crowding in the pcb traces getting into and out of them.

The best way to get on and off a board like this is to use lots of
relatively small wires, again to avoid current crowding in the traces.
Fastons soldered to the board, mating with #14 wire maybe, is pretty
good. The external leads are mechanically friendly as compared to a
single hunk of #4, and the lead resistances help equalize currents on
the board.

Is this for production or one-off? If single-unit, it would be a lot
easier to build with TO-247s with aluminum heatsink+busbar
construction. Expect to blow it all up a couple of times.

Do you need control as well as rectification? If not, mayhe just use
schottky diodes on a heat sink.

John


From: Vladimir Vassilevsky on 16 Jul 2010 10:20


George Jefferson wrote:

> I want to replace a CT full wave rectifier for a 200A+ battery charger
> with a active rectifying system.
>
> http://www.nxp.com/documents/data_sheet/PSMN2R5-30YL.pdf
>
> Are some 100A 80W logic level fets which means I can parallel 3 or 4 of
> them and increase the efficiency of the charger(there are other reasons
> for doing it too).
>
> I'll be driving the mosfets using a driver circuit instead of a uC of
> course(just to reducing cross conduction problems).
>
> In any case the real issue I have is how to do this on a pcb, if it is
> even possible. Not only are the leads to the packages somewhat small I
> can't think of any way how this can be done on a pcb(30oz pcb's?) or
> large solder traces in any decent fashion.
>
> Are thee any tricks to defeat mother nature or will I have to design
> some special module that uses a copper bus bar like thing with the
> mosfets soldered directly to it?

The 200A could be done on 2oz copper with careful layout. Watch for the
narrow spots and always calculate the trace resistances. Don't make any
assumptions.
You may have to reinforce a couple of tough places with bus bars; that
could ease up the layout.

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