If you want to ramp DC voltage for your purpose, the schematic below appears 5V/0.5A Step Up Regulator Circuit Diagram using LM2621. It is known to be low input voltage step up DC-DC converter, according to the LM2621 datasheet. The design of this Step Up Regulator Circuit are described in the depth of the datasheet such as setting the output voltage, bootstrapping, setting the switching frequency, inductor selection, output diode selection, I/O filter capacitors selection and PC board selection.
5V/0.5A Step Up Regulator Circuit Diagram using LM2621 can be seen completely here in the datasheet (source: national.com).
