Buck-Boost (Switch Mode) Regulator Provides 12V from 5-35V Supply

This is positive buck-boost regulator circuit. Using this circuit, we can implement a step-down/up converter with a positive output voltage. This circuit produces an output voltage of 12 V. Here is the circuit :

This circuit requieres input voltage between 5 V and 35V. The output voltage is given by Vo=Vin·D/(1-D).  The maximum output current is Iout=1x(1-D). The term (1-D) reduces current capability because only during the OFF phase, current flowing trough the internal power switch is delivered to the output. [Source: STMicroelectronics Application Note]