Design and Control of a Buck-Boost DC-DC Power Converter

A study on the properties and control of a promising circuit topology for a DC-DC buckboost power converter is presented. The circuit contains four transistors operated synchronously in couples. We propose a set of mathematical models to describe this circuit, and an approach to determine the behavior of the losses occurring inside of it. These are then combined in order to achieve a control scheme that drives the circuit while minimizing said losses. The control strategy proposed here is based on a combined feedback (MPC) and feedforward action. Control performance parameters such as disturbances rejection capability have been investigated as well. 1.1 Motivation and Objectives The present work deals with the design and control implementation of a BuckBoost DC-DC power converter. DC-DC power converters are employed in order to transform an unregulated DC voltage input (i.e. a voltage that possibly contains disturbances) in a regulated output voltage. For example, a DC-DC power converter can transform an unregulated (i.e. distorted) 9V input voltage in a regulated (i.e. ”clean”) voltage of 12V at the output. Some DC-DC power converters have a fixed output reference and ensure that such voltage is always delivered, no matter what the input is; some others can have a variable output reference, which can be therefore set depending on the current need of the device the power converter is used in. The converter discussed in this work belongs to this second category. In particular, the converter is able to deliver output voltages both higher as well as lower than (or even equal to) the input voltage; this is why it is referred to as a ”buck-boost” (or ”step-up/step-down”) power