Modelling of a Modified Buck Converter
DOI:
https://doi.org/10.62760/iteecs.5.3.2026.218Keywords:
DC/DC Converter, Signal flow graph, Transfer function, Large signal model, Small signal modelAbstract
DC/DC converters are very important system components in electronic devices and are used in consumer electronics, communications, computing, traction, robotics and so on. The studied converter is a modified step-down converter which reduces the input voltage to a lower output voltage. The modification concerns the position of the storage capacitor. It is not connected between the output terminals, but between one input and one output terminal. The model of the converter is calculated and presented, starting from the differential equations which describe the operational modes of the converter in the continuous inductor current mode. After combination to a nonlinear matrix differential equation, a linearization is done. This linearized model is step by step transformed into a signal flow graph. From this graph the transfer functions which describe the converter around an operation point are calculated. As an example one of these transfer functions is drawn. Using signal flow graphs helps to understand the converter, is a second opportunity to calculate the transfer functions and can be applied in a similar way to other DC/DC topologies. The transfer functions are necessary for the controller design, and the graphic representation is useful to understand more sophisticated control concepts, such as two-loop control or state space controllers. The models are compared with the circuit simulation and show a good coincidence.
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