[sdiy] Power Supplies in electronic-sea.net :)

[Oscar Salas]

Hello Neil,

The P2 (MIC2941) efficiency:
80VA transformer
1A output
Measured 0.25A in the transformer's primaries.
(30V*1A)/(0.25A*230V)= 0.52

The P1(LM317/337) efficiency:
100VA transformer
1A output
Measured 0.31A in the transformer's primaries.
(30V*1A)/(0.31A*230V)= 0.42

Maybe it might have been more appropriate to have written “with higher
efficiency” instead of “high efficiency”

Anyway, the purpose with the PS2 is to reduce the regulators' heat sinks,
and/or, to operate the regulator at lower junction temperature thus
increase its reliability. This is widely achieved. And this is specially
important when using passive dissipation.

The PS2, due the lower voltage drop of the MIC2941 regulators, (max 0.6V
at 1A) can operate with a 30VCT transformer at the same time that provides
acceptable immunity to mains voltage drop.
This factor and the MIC2941 lower junction to case's thermal resistance
(2C/W) allow to use smaller heat-sinks.

For example, for a 1A, +/-15V power supply, we want a heat-sink that
warranties the regulator's junction temperature below 125C under worst
case conditions; ambient temperature=40C and 10% high mains voltage.
The PS1(LM317/337)(with 100VA, 4700uF)will need a heat sink with thermal
resistance of 1.5CW for each regulator.
The PS2(MIC2941) will need a heat sink with thermal resistance of 8.6CW
for each regulator.
This is a huge difference, although, in this example, PS1 will provide
immunity to mains voltage drop up to about 18% and PS2 up to about1 14%.
However new version of PS2 could achieve also up to 18% of immunity to
mains voltage drop.

Regards,

http://electronic-sea.net/power_supply.html






> Hi Oscar,
>
>> 2)The last months I was studying the Power Supply. I developed one power
>> supply based with the well known LM317/LM337 regulators and another,
>> high
>> efficiency power supply, using LDO MIC2941 regulators.
>
> Great stuff!
>
> What is the typical efficiency you are seeing with the MIC2941?
>
> Cheers
> Neil
> --
> Modules and more :: www.cesyg.com
> Homepage :: www.njohnson.co.uk ::
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