Buck Converter In Continuous Conduction Mode Research Articles

Extended Feedback Linearisation Control of Non-ideal DCDC Buck Converter in Continuous-conduction Mode

Abstract This paper presents an extended form of Feedback Linearisation Control (FBLC), which is tested in a non-ideal buck converter in Continuous-conduction Mode (CCM). The FBLC is often used in power electronics to control a non-linear system, due to its advantageous properties. The application of the error integrator shows better steady-state and transient properties, such as a decrease of inrush current. The linearised system has been controlled by the pole placement and the technique is illustrated through an example and simulated via Matlab. The results have been compared by using a classical PID controller, allowing the benefits of FBLC to be highlighted.

A Capacitor Current and Capacitor Voltage Ripple Controlled SIDO CCM Buck Converter With Wide Load Range and Reduced Cross Regulation

It is well-known that the ripple control technique benefits from fast load transient response and small cross regulation for single-inductor dual-output (SIDO) dc–dc converter. However, existing capacitor current ripple (CCR) controlled SIDO buck converter suffers from incomplete operation state and single switching path. Thus, it has a limited stable load range. In order to extend the stable load range and suppress cross regulation of SIDO buck converter in continuous conduction mode (CCM), a novel ripple control technique, called as capacitor current and capacitor voltage ripple (CCVR) control, is proposed in this article. The operation principle of the proposed CCVR controlled SIDO CCM buck converter is presented, and its discrete iterative map model is established. Furthermore, the stability and stable load range have been discussed by using bifurcation diagrams. Based on the established small signal model, Bode plots are given to show the performance in suppressing cross regulation. Finally, simulation and experiment results are provided to verify the theoretical analysis. It shows that the proposed CCVR control technique can be applied to SIDO CCM buck converter to extend its stable load range and suppress its cross regulation.

Research on Dual-Carrier Pulse-Train-Controlled Buck Converter

In order to solve the low-frequency oscillation of pulse-train- (PT-) controlled switching converter operating in a continuous conduction mode (CCM), a dual-carrier pulse-train (DCPT) control technique is proposed in this paper. With the CCM buck converter as an example, the operational principle, pulse control law, and output voltage ripple of the DCPT-controlled converter are studied. The experimental results are provided to verify the theoretical analysis and simulation results. Compared with the PT-controlled converter, the DCPT-controlled CCM buck converter enjoys much better operating characteristics and smaller output voltage ripple.

Analysis, design, and performance evaluation of zero‐voltage‐ripple buck dc–dc converter

A buck dc-dc converter with ripple reduction has been proposed previously. However, detailed characterisation and performance analysis were not conducted. This study presents steady-state analysis, design, and performance evaluation of the zero-voltage ripple (ZVR) buck dc-dc converter in continuous conduction mode (CCM). The ZVR buck converter is capable of eliminating the output voltage ripple by employing a two-winding auto-transformer. The expressions for steady-state current and voltage waveforms are given. The equations for the design of the converter components are derived. A step-by-step procedure to design the auto-transformer for the ZVR buck converter using the area-product method is introduced. Derivations of expressions for the power losses in passive components, magnetic core, windings, and semiconductor devices are presented. A laboratory prototype of the ZVR buck converter in CCM with input voltage 12 V, output voltage 5 V, output power 10 W, and switching frequency 500 kHz was designed, built, and tested. Simulation results showing the superior performance of the ZVR buck converter over the poly-phase converters are given. Experimental results are provided to validate the theory. It was observed that the ZVR buck converter produces nearly zero ripples at any duty cycle with efficiency in the order of 90%.

Hybrid Modeling Method and Bifurcation Characteristics Analysis for Buck Converter with Constant Power Load

We establish a novel hybrid model of a continuous conduction mode buck converter with a constant power load based on the mixed logical dynamical modeling method. Based on the proposed model, the influence of the constant power load’s negative impedance (RCPL) on the dynamics of the buck converter with a constant power load is studied by computing bifurcation diagrams and the spectrum of the largest Lyapunov exponents with the variation of the absolute value of RCPL. Numerical results show that the system’s bifurcations exhibit two different types of behavior, namely, Hopf bifurcations and state jumping. Moreover, the accuracy and effectiveness of the established mathematical model are verified via simulation and experimental results. Because of including different discrete mappings of the system exhibited in different working modes in a unified model, the proposed hybrid model solves the problem of choosing different discrete mappings according to different working models. That is, the hybrid model in this paper provides a new unified model for future research on the dynamic properties and design of controllers for such systems.

Cross-Regulation Suppression and Stability Analysis of Capacitor Current Ripple Controlled SIDO CCM Buck Converter

For a single-inductor dual-output (SIDO) dc–dc converter operating in continuous conduction mode (CCM), load variation of one output will affect the voltage of the other output, i.e., there exists cross regulation between its two outputs. To suppress the cross regulation of the SIDO dc–dc converter operating in CCM, a novel ripple based control technique, called capacitor current ripple (CCR) control technique, is proposed in this paper. The operation principle of the SIDO CCM buck converter and the proposed CCR control technique are presented. The small signal model of the CCR-controlled SIDO CCM buck converter is established by the state space averaging method. Bode plots based on small signal model show that the proposed CCR-controlled SIDO CCM buck converter significantly reduces cross regulation and improves the transient performance compared with the peak current mode controlled SIDO CCM buck converter. In addition, the effect of the variation of loads on the stability of the proposed CCR-controlled SIDO CCM buck converter is analyzed by eigenvalues analysis. Finally, experimental results are provided to verify the analysis results.

Analysis and Modeling of Fractional-Order Buck Converter Based on Riemann-Liouville Derivative

In previous studies, researchers used the fractional definition of Caputo to study fractional-order power converter. However, it is found that the model based on Caputo fractional definition is inconsistent with the actual situation. The fractional definition is crucial for the application of fractional-order theory into electric engineering, which directly influences the accuracy of model and operational characteristics of power converter. This paper analyzes fractional-order Buck converter according to the fractional definition of Riemann-Liouville. Firstly, the converter model operating in continuous conduction mode (CCM) is established under Riemann-Liouville fractional definition, and it shows that voltage gain and inductor current are relative with the order, but they are independent of order in the model of Caputo fractional definition. Secondly, the different steady-state characteristics of CCM Buck converter are researched under the models of Caputo and Riemann-Liouville derivative. Finally, the feasible simulations and experiments verify that the model derived by Riemann-Liouville fractional definition is more accurate and suitable for analyzing Buck converter.

Critical output‐capacitor ESR for stability of V 2 controlled buck converter in CCM and DCM

It has been reported that subharmonic instability exists in the V2 controlled buck converter in continuous conduction mode (CCM) when the duty ratio is above 0.5 (D > 0.5) and no stability issue exists in discontinuous conduction mode (DCM) when 0 < D < 1. However, the CCM and DCM instabilities will appear in the safe duty ratio range when the equivalent series resistance (ESR) of the output capacitor is below a critical value. The critical output-capacitor ESR for the stabiiity of a V2 controlled buck converter in CCM and DCM is investigated by using the discrete-time model and verified by circuit simulations.

Low-frequency oscillation of continuous conduction mode buck converter with pulse skipped modulation

Low-frequency oscillation phenomenon in pulse skipped modulation (PSM) buck converter operating in continuous conduction mode (CCM) is reported in this paper. Energy transfer difference between the PSM-controlled buck converter operating in discontinuous conduction mode (DCM) and that in CCM is studied. The mechanism of low-frequency phenomenon in PSM-controlled CCM buck converter is revealed, and a discrete-time model of PSM-controlled buck converter operating in CCM is established. Based on this model, the border collision bifurcation with variations of the ESR is studied; meanwhile, the inhibition effect of output capacitor equivalent series resistance (ESR) on low-frequency oscillation is presented. Based on the above analysis, a capacitor current pulse skipped modulation (CC-PSM) technology is proposed; the energy transfer principle of CC-PSM controlled buck converter is analyzed. The control pulse of CC-PSM is generated by the comparison between the sampled capacitor current and preset peak reference current, and thus the range of inductor current ripple is limited. Results show that CC-PSM effectively eliminates the low-frequency oscillation in CCM buck converter under classical PSM when the ESR is low. Finally, the experimental results validate the correctness of theory and simulation analysis

Pulse-Train-Controlled CCM Buck Converter With Small ESR Output-Capacitor

The pulse-train (PT) control technique for switching dc-dc converters is simple to design and benefits from excellent control performance. Up to now, almost all of the works on PT control are focused on switching dc-dc converters operating in discontinuous conduction mode, with few works reported on PT control of switching dc-dc converters operating in continuous conduction mode (CCM). In this paper, a PT-controlled CCM buck converter is studied and a unique low-frequency oscillation phenomenon is revealed, which results in large undesired inductor-current and output-voltage variations. The effect of equivalent series resistance (ESR) output-capacitor on the low-frequency oscillation is examined. The results indicate that such oscillation occurs when the ESR output-capacitor is relatively small and disappears when it is relatively large. However, a larger ESR will result in a large output-voltage ripple. In order to avoid the low-frequency oscillation and, at the same time, to ensure a small output-voltage ripple, the ICRIF circuit is applied. In this way, a small ESR output-capacitor can be used to decrease the output-voltage ripple. Simulation and experimental results are provided to verify the theoretical analysis.

Charge Balance Analysis and State Transition Analysis of Hysteretic Voltage Mode Switching Converters

Charge balance analysis and state transition analysis are presented in analyzing hysteretic voltage mode switching converters working in the steady state. It is shown that the ideal buck converter with a current-sink load can only work in discontinuous conduction mode (DCM) but not in continuous conduction mode (CCM), and the same converter with a resistive load can work in CCM, but the output voltage ripple is very large compared to the hysteresis window. Previously published CCM designs are functional because their operations actually rely on the small but nonzero equivalent series resistance (ESR) of the filtering capacitor. For the CCM buck converter with nonzero ESR, our proposed state transition analysis gives a much more accurate switching frequency than previous approaches. The hysteretic voltage mode boost and buck-boost converters are then analyzed, and shown to have no feasible operating region. Crucial simulation results are presented to confirm the analyses.

Analysis of low-frequency oscillation phenomenon in the pulsetrain controlled buck converter

In this paper, the low-frequency oscillation phenomenon in a pulse train (PT) controlled buck converter operating in continuous conduction mode (CCM) is found and studied. The mechanism of this low-frequency oscillation phenomenon and the way to suppress it are studied. The time-domain simulation results and their corresponding phase portraits indicate that the equivalent series resistance (ESR) of the output filter capacitor has a critical effect on this low-frequency oscillation phenomenon. When the ESR is zero or small enough, such a low-frequency oscillation phenomenon appears in the PT controlled CCM buck converter because the output voltage can not be regulated timely. With the increase of ESR, the PT controlled CCM buck converter operates chaotically. The output voltage can be regulated timely and such a low-frequency oscillation phenomenon can be suppressed effectively. Experimental results are provided to verify the theoretical analyses and the simulations.