This circuit is suitable for a variety of uses. If you have a solar powered 12 Volt lead-acid battery power source, the circuit can be used to efficiently power lower voltage devices. It can be used to provide power to devices that normally use a set of small batteries for power. Common voltages such as 1.5V, 3V, 4.5V, 6V, 7.5V, and 9V can be produced by this circuit. The circuit has been used to power small fans, portable radios, a miniature TV, and more.
Buck Mode Switching Regulator for Solar Applications – [Link]