I am attempting to design a dual rail power supply PCB for a university project. There are a number of restrictions – namely that it maintains > 80% efficiency regardless of the current draw. I was originally just going to use a single battery (Maybe LiPo) with a voltage divider to provide a virtual ground connected to the common pins of both a 7805 and a 7905 to provide +-5V (For a microcontroller + numerous op amps), however, they have a relatively horrible efficiency.
I should also note that I need to supply enough current for 4 x 10 DIL BAR LED's, up to 10 op amps, an Arduino Mini. I've roughly estimated this at 0.5A to be on the safe side.
My current solution involves a TL2575-05 switch mode regulator for the +5V @ 1A, hooked up as per the example in the datasheet. My -5V is currently problematic. I've looked at the LT1074HV, but I can't find its efficiency, and it's ~$22 a unit.
Surely there must be a simple way to produce a +-5V power supply from a single battery, that is both efficient and cost effective?
EDIT: Current schematic
Best Answer
There are specific converters for this purpose, named Split Rail Converters. These ICs consits of two converters in one package and have two output, +Vout, -Vout for each. Adventage is that the design will be much simpler and BOM size will be smaller too.
Example, TPS65133 :
This one is arround 2.6$. Note that this particular example could not supply as much current as you need, but I am sure that you can find a suitable one now. I just wanted to point out to search for one converter instead of two.