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 is
> > suitable.
> > Perhaps a little more info about the project is in order. Following
> > the transformer there'll be a bridge rectifier, smoothing cap... then
> > a linear regulator suppling constant current to charge batteries. The
> > circuit is a bit more involved than only this (protection diodes,
> > charge controller, etc) but this is the subsection in question and the
> > 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. Stripping down
> 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? They will generate heat too, and waste energy.
What are you charging? What supply voltage do you need?
Lots of surplus 12, 15 or 18VDC switching power supplies from old
laptops - see a thrift store, or a surplus electronics store
Michael
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