Design issues and performance analysis of CCM boost converters with RHP zero mitigation via inductor current sensing
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ORIGINAL ARTICLE
Design issues and performance analysis of CCM boost converters with RHP zero mitigation via inductor current sensing Mauro Leoncini1 · Salvatore Levantino1 · Massimo Ghioni1 Received: 23 June 2020 / Revised: 22 October 2020 / Accepted: 30 October 2020 © The Author(s) 2020
Abstract The right-half plane (RHP) zero in the control to output voltage transfer function of a boost converter operating in the continuous conduction mode limits the loop bandwidth. By injecting a scaled version of the inductor current into the loop, it is possible to shift the zero from the right-half plane to the left-half plane, which leads to increased stability of the control loop. This solution generates a static voltage error at the output of the converter (tracking error), which may be unacceptable in practical applications. A few strategies to mitigate or correct this tracking error have been suggested. However, they have never been fully assessed. This paper thoroughly investigates the impact of the RHP zero mitigation technique on the dynamic performance of a boost converter, and identifies the complex trade-off between the system stability, transient response, and tracking error correction capability. Based on these findings, design guidelines are provided to help maximize system performance. A representative case study is considered to highlight the performance benefits and simulation results are presented to validate the analysis. Keywords Boost converter · Right-half-plane zero · Transient response · Dynamic performance · Tracking error
1 Introduction Handheld devices with large LED displays require one or more high-efficiency step-up DC–DC converters occupying small footprints and being able to handle large instant line and load variations without impairing image quality. Stepup converters working in the continuous conduction mode (CCM) suffer from the presence of a right half plane (RHP) zero, which constrains the closed-loop bandwidth of the converter, which affects the speed of the transient response. This zero, which is inherently present in the control-to-output transfer function, usually limits the maximum bandwidth to a fraction of the frequency of the RHP zero. A typical solution is to force the converter to operate in the discontinuous conduction mode (DCM). In this mode of operation, the RHP zero is shifted to a much higher frequency, which increases the phase margin for a given bandwidth [1]. Unfortunately, this advantage comes at the price of a large inductor current ripple, which results in higher device * Mauro Leoncini [email protected] 1
Department of Electronics, Information, and Bioengineering, Polytechnic University of Milan, Milan, Italy
stress, lower efficiency, and potential magnetic core saturation. Numerous papers have been devoted to the RHP zero problem [2-16]. In [3-8], the unwanted zero is either moved to a higher frequency or eliminated by modifying the power stage topology. These solutions, despite providing excellent dynamic behavior, require an extra power MOS swi
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