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Buck Boost Converter

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This example shows the operation of buck boost converters using the inverting and non-inverting topologies.

Description

The buck boost converter is a DC/DC converter with the output voltage magnitude that is either greater than or less than the input voltage magnitude. It is comparable to a flyback converter where an inductor is used in place of a transformer. The theoretical transfer function of the buck boost converter is:

$abs(Vout) = D/(1-D) * Vin$

where $D$ is the duty cycle.

The inverting buck-boost topology produces an output voltage that is of the opposite polarity as the input voltage. The output voltage is determined by the duty cycle of the MOSFET transistor.

The non-inverting topology, also named the 4-switch topology, produces an output voltage that is of the same polarity as the input voltage. In the buck mode, the output voltage is determined by the operation of the MOSFET and diode D1. In the boost mode, the output voltage is determined by the operation of the IGBT and diode D2.