Analysis of a boost converter with tapped inductor and reduced voltage stress across the buffer capacitor

Abstract

A step-up converter with tapped inductor is analyzed. Compared to the classical boost converter, the structure has been slightly modified which offers the advantage of reduced voltage stress across the buffer capacitor and due to a transformer the voltage transformation rate is changed. The classical and most common converter uses a simple inductor, leading to the disadvantage of extreme duty ratios when high voltage transfer ratios are needed. To meet such requirements, a tapped inductor (autotransformer) can be used instead of the ordinary inductor thus avoiding excessive duty ratios. After basic analyses in the continuous inductor current mode, important data for the dimensioning of the components, like the voltage and the current stress, and the equations for the component values are given. Moreover, a state space model and linearized transfer functions for the control of the converter are derived. When transformed into a bidirectional converter, it can be used for coupling two voltage links and as a two quadrant chopper for DC motors. To verify the proper function of this modified boost topology, a small test converter has been designed. Measurement results and a more precise model are given in the appendix.