[Ken] needed to supply 3.3 volts of regulated power. He started by using a linear voltage regulator but after a few calculations he discovered that 72% of what he put in was lost to heat. The solution to this is a switched-mode power supply. Rather than burn off energy through a voltage divider, an SMPS turns the power on and off very quickly to achieve the desired voltage.
A car charger-type USB regulator was chosen as [Ken’s] donor device. He figured that making adjustments to the resistors inside would affect the output voltage and he was right. He adjusted the potential divider and ended up with a steady 3.295V.
Above is [Ken’s] hand drawn schematic. After conversing with him about this project he grabbed a jeweler’s loupe and was able to identify the DC-DC converter in the circuit. It’s an MC34063 whose datasheet can be found here (PDF).