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

[Jake]

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