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Simple power supply?

dorke

Jun 20, 2015
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Sorry to say but,
you don't understand the meaning of dropout voltage!
Read about it till you get it...
 

Mike Taylor

Sep 11, 2015
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When I
Mike,
We need to keep in mind that the LM350 is a Voltage Regulator.
Hence it is specified like a VR :
Load and Line regulations being the most important characteristics and
ref. voltage accuracy and adj. current change the 2nd in importance.

Look at the datasheet from Ti,
they spec only for Vin-Vout= "dropout voltage" greater than 3V.
and for load regulation above 5V!

If we want a solid design(worse case design),
we should comply with the manufacture's specs.
The device may still work if we don't ,but the results are not to spec anymore.

So,like you said:
"I have observed the 350 still supplying current
to 6v batteries with a delta as low as 2 v"

Was your design a voltage regulator?what was the regulated voltage and it's stability?
Or was it a current source?what was the regulated current and it's stability?
In any case the out of spec working conditions had an effect on
charging current,charging time,and maybe battery life time etc.


View attachment 22362




I guess you studied vacuum-tubes as well...
Yes we forget a lot(and it is frustrating ,me too).
Nowadays in EE field ,2 years are a generation ,10 years an era...o_O
when I started EE in 1960 it was all vacuum tubes. When I finished in 1965 it was all transistors. I did an IEEE paper on LED's in 1964. This was when Bell Labs first started producing them in their lab. My instructor gave me an A+ on the paper. I still have it somewhere.

Mike
 

davenn

Moderator
Sep 5, 2009
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when I started EE in 1960

dang, Mike, you must have a few yrs on me LOL I was born in 1959 ;)


stick in there buddy, there's always time to learn new things :)
spend time reading operation descriptions in datasheets, ask questions on anything in particular you don't understand
and one of us will do our best to guide you through the new territory :)


Dave
 

Mike Taylor

Sep 11, 2015
21
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dang, Mike, you must have a few yrs on me LOL I was born in 1959 ;)


stick in there buddy, there's always time to learn new things :)
spend time reading operation descriptions in datasheets, ask questions on anything in particular you don't understand
and one of us will do our best to guide you through the new territory :)


Dave
That day you quit learning is the day you die. And if you're not dead then you might as well be.
 

dorke

Jun 20, 2015
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Mike,
You are my kind of guy...:cool:

Furthermore, learning is so easy now days with the web,keeps the rust away.

For every open mind in the universe, I warmly recommend these great sites (free!) :
www.coursera.org
www.edx.org
 

dorke

Jun 20, 2015
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eetech,
Now that is much better!... still think it will not work.;)

I wonder what are the exact conditions of the simulation.
For instance,
can you make it simulate different temperatures,350 device variances,R and C accuracy etc.
purpose being worse case scenario design
 

eetech00

Nov 17, 2014
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eetech,
Now that is much better!... still think it will not work.;)

I wonder what are the exact conditions of the simulation.
For instance,
can you make it simulate different temperatures,350 device variances,R and C accuracy etc.
purpose being worse case scenario design

LTspice is capable of that...but I didn't model the LM350 to include temperature simulation:)
That would take a lot more effort. The best I could do for now is just show the drop with decreasing input voltage. I would have felt better if the OP had used a transformer with at least a 14v output. :(
 

dorke

Jun 20, 2015
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eetech,
Mike only has a 12V transformer.
A simple thing would be to use a higher filter cap for the first LM350.
The 4700uf value is somewhat marginal(theoretically) but will do,
adding 1000uF or more will clear the case.
 
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