This power supply circuit diagram is based on the ADP1261 fixed-frequency, pulse-width modulation (PWM), current-mode, step-up converter controller. It drives an external n-channel MOSFET to convert the input voltage to a higher output voltage. The ADP1621 can also be used to drive flyback, SEPIC, and forward converter topologies, either isolated or nonisolated.

The ADP1621 eliminates the use of a current-sense power resistor by measuring the voltage drop across the on resistance of the n-channel MOSFET. This technique, allowed up to a maximum voltage of 30 V at the switch node, maximizes efficiency and reduces cost.

The input voltage range that is required by the ADP1621controler is from 2.9 V to 5.5 V. Also higher input voltages are possible with the use of a small-signal  NPN pass transistor or a single resistor. The switching frequency is set by an external resistor over a range of 100 kHz to 1.5 MHz and can be synchronized to an external clock by using the SDSN pin. The ADP1621 has a thermal shutdown feature that shuts down the gate driver when the junction temperature reaches approximately 150°C.

The circuit presented here will provide a maximum 12 volts output at a maximum 1 ampere current from an 3.3 volts  input supply voltage .

D2 is a common signal diode , D2 can be a Vishay SSC53L diode and M1 transistor can be IRF7470 .