The Experts below are selected from a list of 783 Experts worldwide ranked by ideXlab platform
R B Ridley - One of the best experts on this subject based on the ideXlab platform.
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small signal modeling of average current mode control
IEEE Transactions on Power Electronics, 1993Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control method is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. This control scheme is suitable for applications where the average inductor current needs to be controlled, as in power factor correction circuits and battery charger dischargers. The Subharmonic Oscillation, commonly found in peak current-mode control, also exists in this method. This Subharmonic Oscillation can be eliminated by properly choosing the proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
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small signal modeling of average current mode control
Applied Power Electronics Conference, 1992Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. By closing the current loop, a flat control-to-inductor current transfer function, up to half the switching frequency, can be achieved. This control scheme enables the converter to behave as an ideal current source. The Subharmonic Oscillation, as frequently reported in peak current-mode control, also exists in this control. This Subharmonic Oscillation can be eliminated by choosing a proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
F C Lee - One of the best experts on this subject based on the ideXlab platform.
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small signal analysis and optimal design of external ramp for constant on time v bf 2 control with multilayer ceramic caps
IEEE Transactions on Power Electronics, 2014Co-Authors: Shuilin Tian, F C Lee, Paolo Mattavelli, Kuangyao Cheng, Yingyi YanAbstract:Recently, constant on-time V2 control, and its variety named constant on-time control, or constant on-time ripple-based control is more and more popular in industry products due to features of high light-load efficiency, simple implementation, and fast transient response. However, Subharmonic Oscillation occurs when using multilayer ceramic caps due to the lagging phase of the capacitor voltage relative to the inductor current. External ramp compensation is one simple solution to solve the instability issue. However, the characteristics of constant on-time V2 control with external ramp are not fully understood and no explicit design guidelines for the external ramp are provided. This paper investigates the small-signal characteristics of constant on-time V2 control with external ramp compensation by providing a factorized, easy-to-use small-signal model. The external ramp is a critical parameter because it directly affects the position and damping of two pairs of double poles. Based on this fact, design guidelines of the external ramp for optimal dynamic performance are provided. Moreover, the effect of duty cycle is investigated. Finally, the small-signal experimental results and load transient performance are presented to verify the small-signal analysis and proposed design guideline.
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small signal modeling of average current mode control
IEEE Transactions on Power Electronics, 1993Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control method is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. This control scheme is suitable for applications where the average inductor current needs to be controlled, as in power factor correction circuits and battery charger dischargers. The Subharmonic Oscillation, commonly found in peak current-mode control, also exists in this method. This Subharmonic Oscillation can be eliminated by properly choosing the proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
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small signal modeling of average current mode control
Applied Power Electronics Conference, 1992Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. By closing the current loop, a flat control-to-inductor current transfer function, up to half the switching frequency, can be achieved. This control scheme enables the converter to behave as an ideal current source. The Subharmonic Oscillation, as frequently reported in peak current-mode control, also exists in this control. This Subharmonic Oscillation can be eliminated by choosing a proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
Fang Chung-chieh - One of the best experts on this subject based on the ideXlab platform.
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Unified Subharmonic Oscillation Conditions for Peak or Average Current Mode Control
'Wiley', 2014Co-Authors: Fang Chung-chiehAbstract:This paper is an extension of the author's recent research in which only buck converters were analyzed. Similar analysis can be equally applied to other types of converters. In this paper, a unified model is proposed for buck, boost, and buck-boost converters under peak or average current mode control to predict the occurrence of Subharmonic Oscillation. Based on the unified model, the associated stability conditions are derived in closed forms. The same stability condition can be applied to buck, boost, and buck-boost converters. Based on the closed-form conditions, the effects of various converter parameters including the compensator poles and zeros on the stability can be clearly seen, and these parameters can be consolidated into a few ones. High-order compensators such as type-II and PI compensators are considered. Some new plots are also proposed for design purpose to avoid the instability. The instability is found to be associated with large crossover frequency. A conservative stability condition, agreed with the past research, is derived. The effect of the voltage loop ripple on the instability is also analyzed.Comment: Subharmonic Oscillation conditions of a class of nonlinear systems (triangular wave generator with linear feedback) are obtained. Any current-mode-control DC-DC converter can be modeled by such such a nonlinear system and its Subharmonic Oscillation condition is obtained. This second version adds Nomenclature, parameter lables in figures, and Fig. 2
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Closed-Form Critical Conditions of Subharmonic Oscillations for Buck Converters
'Institute of Electrical and Electronics Engineers (IEEE)', 2012Co-Authors: Fang Chung-chiehAbstract:A general critical condition of Subharmonic Oscillation in terms of the loop gain is derived. Many closed-form critical conditions for various control schemes in terms of converter parameters are also derived. Some previously known critical conditions become special cases in the generalized framework. Given an arbitrary control scheme, a systematic procedure is proposed to derive the critical condition for that control scheme. Different control schemes share similar forms of critical conditions. For example, both V2 control and voltage mode control have the same form of critical condition. A peculiar phenomenon in average current mode control where Subharmonic Oscillation occurs in a window value of pole can be explained by the derived critical condition. A ripple amplitude index to predict Subharmonic Oscillation proposed in the past research has limited application and is shown invalid for a converter with a large pole.Comment: Submitted to an IEEE Journal on Dec. 23, 2011, and resubmitted to IEEE Transactions on Circuits and Systems-I on Feb. 14, 2012. My current six papers in arXiv have a common reviewe
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Boundary Conditions of Subharmonic Oscillations in Fixed-Switching-Frequency DC-DC Converters
'Springer Science and Business Media LLC', 2012Co-Authors: Fang Chung-chiehAbstract:Design-oriented boundary conditions for Subharmonic Oscillations are of great interest recently. Based on a Subharmonic Oscillation boundary condition reported in a PhD thesis more than a decade ago, extended new boundary conditions are derived in closed forms for general switching DC-DC converters. Sampled-data and harmonic balance analyses are applied and generate equivalent results. It is shown that equivalent series resistance causes the boundary conditions for voltage/current mode control to have similar forms. Some recently reported boundary conditions become special cases in view of the general boundary conditions derived. New Nyquist-like design-oriented plots are proposed to predict or prevent the occurrence of the Subharmonic Oscillation. The relation between the crossover frequency and the Subharmonic Oscillation is also analyzed.Comment: Title changed. Submitted to a journal on 2/24/11, and resubmitted to IJCTA on 8/10/11. Added: S-plot to determine the required ramp slope, V2 control, a counterexample (Example 5) of the ripple index hypothesis. The key results traced back from my 1997 PhD thesis, available: http://www.lib.umd.edu/drum/. My five IJCTA papers in arXiv have two common reviewer
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Using Nyquist or Nyquist-Like Plot to Predict Three Typical Instabilities in DC-DC Converters
'Elsevier BV', 2012Co-Authors: Fang Chung-chiehAbstract:By transforming an exact stability condition, a new Nyquist-like plot is proposed to predict occurrences of three typical instabilities in DC-DC converters. The three instabilities are saddle-node bifurcation (coexistence of multiple solutions), period-doubling bifurcation (Subharmonic Oscillation), and Neimark bifurcation (quasi-periodic Oscillation). In a single plot, it accurately predicts whether an instability occurs and what type the instability is. The plot is equivalent to the Nyquist plot, and it is a useful design tool to avoid these instabilities. Nine examples are used to illustrate the accuracy of this new plot to predict instabilities in the buck or boost converter with fixed or variable switching frequency.Comment: Submitted to an IEEE journal in 201
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Sampled-Data and Harmonic Balance Analyses of Average Current-Mode Controlled Buck Converter
'Wiley', 2012Co-Authors: Fang Chung-chiehAbstract:Dynamics and stability of average current-mode control of buck converters are analyzed by sampled-data and harmonic balance analyses. An exact sampled-data model is derived. A new continuous-time model "lifted" from the sampled-data model is also derived, and has frequency response matched with experimental data reported previously. Orbital stability is studied and it is found unrelated to the ripple size of the current-loop compensator output. An unstable window of the current-loop compensator pole is found by simulations, and it can be accurately predicted by sampled-data and harmonic balance analyses. A new S plot accurately predicting the Subharmonic Oscillation is proposed. The S plot assists pole assignment and shows the required ramp slope to avoid instability.Comment: Submitted to International Journal of Circuit Theory and Applications on August 9, 2011; Manuscript ID: CTA-11-016
W Tang - One of the best experts on this subject based on the ideXlab platform.
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small signal modeling of average current mode control
IEEE Transactions on Power Electronics, 1993Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control method is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. This control scheme is suitable for applications where the average inductor current needs to be controlled, as in power factor correction circuits and battery charger dischargers. The Subharmonic Oscillation, commonly found in peak current-mode control, also exists in this method. This Subharmonic Oscillation can be eliminated by properly choosing the proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
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small signal modeling of average current mode control
Applied Power Electronics Conference, 1992Co-Authors: W Tang, F C Lee, R B RidleyAbstract:A recently proposed average current-mode control is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. By closing the current loop, a flat control-to-inductor current transfer function, up to half the switching frequency, can be achieved. This control scheme enables the converter to behave as an ideal current source. The Subharmonic Oscillation, as frequently reported in peak current-mode control, also exists in this control. This Subharmonic Oscillation can be eliminated by choosing a proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >
Hao Min - One of the best experts on this subject based on the ideXlab platform.
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predictive digital current control of single inductor multiple output converters in ccm with low cross regulation
IEEE Transactions on Power Electronics, 2012Co-Authors: Zhonghan Shen, Xuegui Chang, Weiwei Wang, Xi Tan, Na Yan, Hao MinAbstract:This paper presents a new digital current-mode control technique for single-inductor multiple-output converters in continuous-conduction mode. This predictive control method can calculate all the required duty cycles corresponding to the outputs for the next switching cycle. Since the calculation is based on every current reference representing the load current, all current control loops corresponding to different outputs are theoretically independent, which can greatly reduce the cross regulation. To avoid Subharmonic Oscillation, proper predictive digital current control is adopted. Inductor current estimation is used to remove the current sensing circuit, and corresponding calibration techniques are presented. Simulation and experimental results are given to verify the effectiveness of this control technique.
