I've got a component within a larger device that requires both +15 and -15V, drawing about 100mA per rail.
In addition, the main power supply of the larger device is providing +/- 28V, with a common ground.
My initial thought was to use good old linear regulators - 7815 for +15 and 7915 for -15. However I want something a little more efficient...
...and it just so happens I have a bunch of these fancy R-7815-0.5 switching regulators (PDF) by Recom. They accept 18-35V on the input, and produce +15V on the output (500mA). In addition, they can be used to convert positive to negative, albeit at a lower output current (200mA).
I want the +28V from my supply to step down to +15... no problem there, one of the Recom devices will work perfectly. In addition, it makes sense to me that the -28V be stepped down to -15V.
However, I can't determine whether a switching regulator like this can be wired up to accept a negative voltage input, and thus produce my desired negative output voltage. To be clear, I don't want to do any voltage conversion - I want to my input +28V to produce my +15V, and my -28V to produce my -15V, to ensure that approximately the same load is being placed on both my + and - supply evenly.
In the world of compact, all-in-one switching regulators, there don't seem to be "79xx" equivalents which would make this easy!
- Is it possible to do this with the devices I have - i.e. wire the R-7815-0.5 to accept a negative input?
- If not, what would be the best way to efficiently produce +/-15V from my supply, placing an even burden on each +/-28V rail?