Switching controller that goes above and bellow Vin?

[Korken]

Hi all!

I've been working on a PSU where I need a switching controller that can with one inductor go above and bellow Vin.
I've been searching night and day but I'm unsure of what this type of switching controller is called so I'm unable to find one on Digikey.

Could someone help me with a push in the right direction?
If possible I'm looking for one with internal witching transistors and one with external.

Regards, Emil

[oPossum]

SEPIC: Single ended primary inductor converter

[aep9690]

I think you are looking for a buck boost converter.  It can either boost a voltage above VIN or buck it down below.  They are typically used for uncertain input voltages but I think it will work for what you want as well.

http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter

http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=753&uiTemplateId=NODE_STRY_PGE_T

There are also other solutions such as SEPIC or Cuk converters