State-space control structures for buck converters with/without input filter

Power supplies normally provide a constant output voltage. In most of the applications a DC/DC-converter is controlled by a voltage mode or a current mode controller. These controller types are well known and there are a lot of PWM controller ICs on the market. The controllers are often combined with feedforward techniques of the input voltage or output current, because these variables are disturbance variables. In this paper three state-space control structures are introduced. Based on the state-space representation an easy controller is designed first. The second one is improved as it works with an inner one-cycle controller and an outer I-controller for improving robustness. The third controller is designed for a buck converter with an input filter. The advantages of state-space controllers are pole placement and easy implementation. The input filter requires no resistor for damping and the filter elements can be much smaller. For each of the three controllers an example is shown with controller design, simulation and results. Experimental results are shown for the state-space controller with inner one-cycle controller and outer I-controller