On Jul 11, 4:07=A0pm, mrdarr...@[EMAIL PROTECTED]
wrote:
> On Jul 9, 6:39 pm, emailaddr...@[EMAIL PROTECTED]
wrote:
>
>
>
>
>
> > On Jul 9, 9:26 pm, emailaddr...@[EMAIL PROTECTED]
wrote:
>
> > > I have an application in which I need to determine if a transformer
i=
s
> > > suitable.
> > > Perhaps a little more info about the project is in order.
=A0Followin=
g
> > > the transformer there'll be a bridge rectifier, smoothing cap...
then
> > > a linear regulator suppling constant current to charge batteries.
=A0=
The
> > > circuit is a bit more involved than only this (protection diodes,
> > > charge controller, etc) but this is the subsection in question and
th=
e
> > > rectified output of the transformer will need to stay above roughly
> > > 12.3VDC so I'm trying to figure out what constant current this
> > > transformer (or others) can supply.
>
> > Another thing I am wondering is if a basic, typical small brick AC-DC
> > switching supply is stable powering this kind of load. =A0Stripping
dow=
n
> > the circuit to the basic topology, what if it had for example:
>
> > AC-DC SMPS -> LM317 -> 1.25 Ohm resistor (LM317 in current regulating
> > config) -> 1A into Battery Pack + LM317 feedback
>
> > Since the SMPS is trying to regulate to it's spec'd voltage, let's say
> > that is 13V even if an uncommon value, will it run stable doing so and
> > if so, is that at the same constant output wattage from the SMPS the
> > whole time, with the linear regulator simply dropping more voltage,
> > creating more heat at the beginning of a battery recharge cycle since
> > it's suppling constant current to batteries that are at a lower
> > initial, low state-of-charge voltage?
>
> Why so many LM317s? =A0They will generate heat too, and waste energy.
First, the example is not something I intend to build at all, it is
just providing an example, a load.
Second, in the example there is only one LM317, when I mentioned
"LM317" the 2nd and third time I was only describing the typical
topology of using one LM317 in the context of it being in current
limiting mode. I used an example that is straight from National's
LM317 datasheet since many would presumably be familiar with it.
>
> What are you charging? =A0What supply voltage do you need?
>
I am not building that example. The first example or something fairly
similar I did build a few years ago but now I have no need to consider
the charging or other aspects of the circuit beyond the supply to it,
because it used to be a stationary charger with capability of charging
several different sized packs but it has been reused now for a single
set of packs all with 6 cells. Therefore the most desirable supply
has changed from what it used formerly to something more closely
matched. However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.
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