negative input with a postive output dc/dc - automotive grade with ~90% efficiency

[Jeff Colwell]

Anyone have ideas on how to build a dc/dc with a negative rail input, a single rail positive output with a max load of ~160mA?

 

[ronsimpson]

This is a typical "boost" supply. Normally this is a +12 to +24 supply. But I changed to -12 to +12V.

This is not right because it is trying to make 24V from -12 to +12V. If Vin is -11V then the out put will be 13V.

Below I changed the feed back circuit. Below it is trying to make +12. If Vin is -11V then the output will be 12V.