This budget DC-DC boost converter cranks up input voltage from as low as 2V to an output as high as 28VDC.
A benefit to mobile electronics is the spill-over we get in the form of really cool modules to build our designs. In this case, we're talking about DC-DC Step-up boosters using the AeroSemi MT3608 IC. Attach it to your input voltage, and twiddle the trimpot until you get the output voltage you need (but it has to greater than the input).
There's also step-down (with display), full-range (step up and down) DC-DC converters with different prices and size factors, but by limiting to one function, you save space and cost.
Dropping voltage is a relatively easy process, but creating a higher voltage out of a lower voltage almost seems like alchemy. The MT3608 uses a clever boost circuit with an inductor to turn a low input voltage into a usable higher output voltage.
It can source a good amount of current
It's simple to adjust to get your desired increase in voltage
AeroSemi MT3608 High Efficiency 1.2MHz 2A Step Up Converter design
2A maximum output current
2.0 to 24VDC input voltage range
28V maximum output voltage (trimpot adjustable)
93% peak efficiency (~200mA output current at 5Vin, 12Vout)
36 x 17 x 14mm