Battery Charger SMPS, How'd they do it?
RogerN
microprocessor controlled voltage and current limiting. Here's a link to
something similar:
http://www.amainhobbies.com/product_info.php/cPath/2_389_390/products_id/18362
So, how do you think they are getting 250W 10A at ~0 to near 30V from a 11V
to 28V input? Would this be SEPIC, multiple SEPIC's in parallel, Boost then
Buck, switched capacitor or what? The same company also has a 180W 10A
charger that has an output of over 50V for up 12 LiPo cells or 1-30 NiMh,
NiCd.
I'm wanting something similar, doesn't have to be 250W but it would be nice.
I want to be able to sell it with open source code so that I and others can
customize the firmware to add features and new charging algorithms as new
battery technologies come out.
On an earlier posting someone mentioned SEPIC but I haven't found anything
with the power I'm wanting so far, still looking...
Thanks!
RogerN
Martin Riddle
"RogerN" <re...@midwest.net> wrote in message
news:ssOdnZrQ4MbxTXXV...@earthlink.com...
Ti or Onsemi has good app notes on SEPIC converters. I think the
coupling
Cap ESR will limit your effiency.
Cheers
RHRRC
> I'm wanting to come up with a battery charger that is basically a SMPS with
> microprocessor controlled voltage and current limiting. Here's a link to
> something similar:
>
>
> So, how do you think they are getting 250W 10A at ~0 to near 30V from a 11V
> to 28V input? Would this be SEPIC, multiple SEPIC's in parallel, Boost then
> Buck, switched capacitor or what? The same company also has a 180W 10A
> charger that has an output of over 50V for up 12 LiPo cells or 1-30 NiMh,
> NiCd.
>
> I'm wanting something similar, doesn't have to be 250W but it would be nice.
> I want to be able to sell it with open source code so that I and others can
> customize the firmware to add features and new charging algorithms as new
> battery technologies come out.
>
> On an earlier posting someone mentioned SEPIC but I haven't found anything
> with the power I'm wanting so far, still looking...
>
> Thanks!
>
> RogerN
Why particularly SEPIC?
There are lots of app notes around on buck/boost switchers -just make
sure you understand the technologies involved before spending money
on, or marketing , anything.
RogerN
"RHRRC" <h.l...@connect-2.co.uk> wrote in message
news:46457364-fc92-41db...@t54g2000hsg.googlegroups.com...
<snip>
Why particularly SEPIC?
There are lots of app notes around on buck/boost switchers -just make
sure you understand the technologies involved before spending money
on, or marketing , anything.
I'm just wanting to be able to take 12V from a lead acid battery and charge
from 0V (shorted cell) to ~30V-50V. I don't care if it's SEPIC or
buck/boost. Most applications I've seen are for variable input and fixed
output. I need ~11-16V in and 0- ~30V out.
Thanks!
RogerN
MooseFET
> I'm wanting to come up with a battery charger that is basically a SMPS with
> microprocessor controlled voltage and current limiting. Here's a link to
> something similar:
>
>
> So, how do you think they are getting 250W 10A at ~0 to near 30V from a 11V
> to 28V input? Would this be SEPIC, multiple SEPIC's in parallel, Boost then
> Buck, switched capacitor or what? The same company also has a 180W 10A
> charger that has an output of over 50V for up 12 LiPo cells or 1-30 NiMh,
> NiCd.
Since this is a battery charger, every thing but the current limiting
can be slowish. This could make doing the whole PWM process within
the micro practical.
> I'm wanting something similar, doesn't have to be 250W but it would be nice.
> I want to be able to sell it with open source code so that I and others can
> customize the firmware to add features and new charging algorithms as new
> battery technologies come out.
>
> On an earlier posting someone mentioned SEPIC but I haven't found anything
> with the power I'm wanting so far, still looking...
250W is at the high end but within the reach of the SEPIC topology.
The same can be said for the transformer coupled flyback. You have
said that you want to make it open source so I assume that this means
that you would rather not use any custom parts. For this reason I
suggest that the boost-buck be your choice.
If you look at the buck regulator, you will notice that all the
switching happens on the input end of the inductor. If you look at a
booster, all the switching happens on the output side.
You can do both types of switching with the same inductor. When you
are bucking, the boost circuits inductor is always off. When you are
boosting, the buck transistor is always on. This means that the micro
only needs to PWM one device at a time.
The current limit system needs to be able to turn the buck transistor
off quickly. It may be practical to allow the micro to be in this
path. An interrupt can be generated by the over current circuit and
the micro could get the transistor off before any damage is done.
The inductor you are going to use will have to be somewhat huge.
Getting inductors this large off the shelf is not very easy. You can
use a string of lower value inductors in series.
whit3rd
> The inductor you are going to use will have to be somewhat huge.
> Getting inductors this large off the shelf is not very easy.
So, instead of a shelf system, think in terms of pallets, forklifts,
and the like...
Seriously, most large inductors are carefully designed and
custom-made for an application, not stocked at distributors.
In onesies, cannibalizing a PC power supply is the easiest
way to find a suitable bag of components for a gizmo
like this. I've designed and wound my own inductors, but
the safety-critical nature of the high voltage/high current
parts means extra pitfalls. Just remove the filter capacitors
from a PC power supply and replace its voltage sense
feedback with something battery-charge-relevant,
it'll deliver all the current your batteries could want.
And when you make a mistake, the builtin fuse will indicate
and no house-burn-down event is expected.