[Noisebridge-discuss] DC-DC Power conversion - Cheapish finds!

[Jake]

On Tue, 8 Jan 2013, Nicholas Granado wrote:
> it might be useful to examine (it was to me) the mintyboost circuit 
> (uses a buck converter). there's a great write up by ladyada 
> here: http://www.ladyada.net/make/mintyboost/process.html

no, the mintyboost uses a BOOST converter.  Similar but different.  Also i 
think the chip she uses is a bit hard to find, although it's quite 
powerful.

> On Tue, Jan 8, 2013 at 5:27 AM, Jake <jake at spaz.org> wrote:
>       For me, when i want a DC stepdown regulator up to an amp or so (maybe two amps) i just grab a cellular phone car charger.  They are all the same, a tiny
>       circuitboard inside with a DIP version of the 34063 buck converter.
>
>       up to 14 or 15 volts input, 5 volts output, just drop it in.  If you need a different output voltage, just add a resistor across one of the two resistors in the
>       resistor-divider network.  If you need more than 15 volts input (up to 40v) just replace the capacitor with a higher voltage (unless it is already rated at least
>       10% higher than your working voltage).
>
>       If you need more current, and/or want to be able to make buck converters from scratch, the LM2576 is great.  There is a fixed 5v-output version (so the only parts
>       you need are inductor, diode, and two capacitors) or a variable output version (add two resistors to select voltage).  It's simple enough that you can put it
>       together without a circuitboard if you're in a hurry.  Just ask Zach!
>
>       The LM2576 goes up to 40V input, and the LM2576-HV goes up to 60V!
>       Both can put out THREE AMPS of current.
>
>       http://www.ti.com/lit/ds/symlink/lm2576.pdf
>
>       Garrett, when you mentioned the 7805 you missed that we were talking about PWM-style buck converters, which are up to 90% efficient.  A 7805 linear regulator is
>       basically just an automatic resistor which burns up the extra voltage, times the current you're using.  So, powering something with 5V from a 15V power source,
>       you're literally burning off twice as much power as you're making use of (33% efficiency).
>
>       -jake
>
>       Garrett wrote:
>             This is better/cheaper for 5V 500mA from 6.5-36V:
>             http://www.digikey.com/product-detail/en/V7805-500/102-1709-ND/1828602
>
>             And the big brother for 1000mA:
>             http://www.digikey.com/product-detail/en/V7805-1000R/102-2178-ND/2352137
> 
> 
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