Analysis and control of a single switch wider step‐down gain DC–DC converter for low‐voltage applications

Abstract

This paper presents a point-of-load transformerless DC-DC converter having a wider step-down conversion ratio. In comparison with quadratic/stacked buck converter variants, the presented topology exhibits nonpulsating source current, more effective switch utilization at small voltage gains, and reduced current stress on components. Its comprehensive steady-state analysis is carried out under continuous and discontinuous modes of inductor currents, and design criteria to select L-C components are established. State variable dependency feature in the topology, imposing a reduced fourth-order dynamics, is discussed and subsequently verified from its average model. A fixed frequency sliding mode controller is then designed with a step-by-step evaluation of sliding surface existence, reachability, and stability conditions. The equivalent control law devised in this scheme is duly constituted from source side inductor current dynamics and load voltage error information, so it facilitates simple realization as well as better transient response. Remarkable operational characteristics of the presented converter are studied analytically and demonstrated with experimental observations on a laboratory prototype. K E Y W O R D S buck converter, charge pump network, equivalent sliding mode control, wider voltage gain 1 | INTRODUCTION The recent shift in paradigm toward low-power electronic systems has evolved several variants of DC-DC stepdown converter to be incorporated in advanced point-of-load (PoL) applications. 1,2 Battery chargers, data servers, automotive drivetrains, photovoltaic (PV) energy systems, and LED ballasts are some typical PoL examples 1-3 powered from unregulated 36/42/48 V DC bus or battery packs as shown in Figure 1 to operate within 1.2-12 V range, drawing high currents up to 20 A. Because a traditional buck converter (TBC) offers simple dynamics and low-cost advantages, it has predominantly governed the power supply market. However, key structural limitations such as restricted range of duty ratios (below 10%) to realize lower voltages, poor efficiency and transient performance at such narrow duty ranges, and elevated source current ripples have overshadowed TBC benefits. 3 Without forgoing TBC's eminent structural characteristics, extreme voltage step-down becomes an arduous task. High frequency DC transformer inclusion on source side although provided a reliable addressal measure, but it came through hefty compromise on topological bulkiness, cost, and magnetizing losses. 3,4 Modern [*Corrections added on 14 August 2020, after first online publication: The correct ORCID Id of Mummadi Veerachary has been added.]

Analytical tuning of 2‐DOF smith predictor control scheme for DC‐DC boost converter: A process control perspective

“…Moreover, in most of the processes using boost converter, it is possible to effectively use theorems proved in this paper to obtain (i) gains of PID controllers and (ii) parameters λ , ζ , based on circuit parameters for, better response than the basic heuristically tuned PID without set point filter. One of the interpretation of 2‐DOF‐1‐TP is that it not only provides an additional tuning parameter in the controller, it also enhances the bandwidth of the close loop system, see Figure 7 1–17 …”

“…The presence of an RHP zero in mathematical model (2) poses serious difficulties in design of control law for boost converter. These difficulties continue in any other power electronics systems of which boost converter is an integral part, namely, interleaved boost converter, or renewable energy conversions 4,8–12 . In nutshell, among all power electronics converter, the task of designing a control law to regulate the output voltage for boost converter is the most difficult task as compared to other power converters of which boost converter doesn't constitutes a part.…”

“…These difficulties continue in any other power electronics systems of which boost converter is an integral part, namely, interleaved boost converter, or renewable energy conversions. 4,[8][9][10][11][12] In nutshell, among all power electronics converter, the task of designing a control law to regulate the output voltage for boost converter is the most difficult task as compared to other power converters of which boost converter doesn't constitutes a part. More precisely, an RHP zero is equivalent to a pole in terms of phase shift but behaves as a zero when the magnitude is considered.…”