Using MAX668 integrated circuit you can build a very simple and high efficiency power supply . With Max668 you can design various power supply circuits using few external components . This power supply circuit based on the MAX668 integrated circuit is a high efficiency step up converter that will provide an fixed output regulated voltage around 12 volts at a maximum output current of 2.3 amperes . This step up converter circuit will provide a 12 volts output voltage from a 3.3 to 5.5 input voltage .
As you can see in the table bellow you can see how the output voltage vary in concordance with the input voltage .
R1 from this circuit senses the inductor current for current mode controller and with some internal comparators provide a current limit. R5 in conjunction with C9 filters the switching noise on the sense resistor to prevent false triggering of the current limit. The MAX668's internal current-limit threshold is fixed; changing the resistor, R1, adjusts the current-limit setting. The resistor, R2, sets the operating frequency.
The external components of the MAX668 can have high-voltage ratings that provide greater flexibility for high-power applications.