A non-isolated DC/DC converter topology.

A boost converter is a non-isolated DC-DC converter topology used to step up voltage. It is one of the most fundamental converter topologies in existence.

The basic boost converter power train is comprised of an inductor, a diode, a switch (usually a MOSFET or transistor), and a capacitor.

From Wikipedia

The duty cycle of the switch determines the ratio of load voltage to supply voltage:

$$\frac {V_{out}}{V_{in}}\mbox=\frac{1}{1-D}$$

or

$$D=1-\frac{V_{in}}{V_{out}}$$

Wikipedia: Boost converter