Output ripple analysis of switching DC-DC converters

State space averaging methods are used to derive time-invariant models that bound the envelope of trajectories of pulsewidth modulated (PWM) dc-dc converters. The results are compared to conventional averaging methods used in power electronics, and it is shown that, at times, designing a dc-dc converter based on the averaged output of a converter can be ineffective because peak output values sometimes significantly deviate from the averaged output. This paper attempts to quantify this deviation by using both small-signal transfer functions and nonlinear models to model the maximum and minimum values of outputs of PWM converters. Issues in simulation and control loop design are also mentioned.     

Adaptive two-loop Voltage-mode control of DC-DC switching converters

A new two-loop control scheme for voltage-mode control (VMC) of dc-dc switching converters is presented. The proposed method adds a high-gain robust loop with two controllers to the conventional VMC loop, achieving an analog "adaptive" loop in which the "equivalent voltage regulator" varies with the changing power stage parameters given as follows: 1) input voltage; 2) load; and 3) component tolerances. The loop significantly improves the disturbance rejection of the control system, i.e., closed-loop output impedance and audiosusceptibility while preserving the stability and the loop gain crossover frequency to a significant extent. Both the small-signal analysis and the experimental results carried out on a buck converter demonstrate the superiority of the proposed scheme with respect to the conventional single loop.     

Large-signal modeling and simulation of switching DC-DC converters

A general nonlinear continuous formulation procedure for large-signal analysis of switching DC-DC converters is presented. The method can be applied in either of the two conduction modes, and it is easily programmed for computer-aided analysis with small simulation time. A boost regulator operating in constant-frequency current-programmed mode is used to illustrate the application of the method. A stability graph is subsequently developed to facilitate the design of DC-DC switching regulators for large-signal applications. The graph provides an estimation of the values of input voltage and load resistance leading to a stable regulator behavior     

An improved LQR-based controller for switching DC-DC converters

A general approach for controlling pulse-width-modulated (PWM) -type switching DC-DC converters digitally using state-feedback techniques and linear optimal control theory is reported. The methodology for redesigning the state estimator is investigated, and a method derived from the general linear-quadratic-regulator (LQR) problem, is proposed. The method is found to offer better transient responses and robustness to uncertainties in plant parameters when compared with the typical eigenvalue-assignment method. Special attention is directed to plant models with possible migrations of the open-loop zeroes across the stability boundary during operation. Results of applying these techniques to a published Cuk converter are reported to illustrate different points of interest     

Dynamical effects of missed switching in current-mode controlled DC-DC converters

Past investigations on nonlinear phenomena in DC-DC converters assume ideal switching and ignore the practical issue of switching ripples, for which the sampled data models yield piecewise smooth but continuous maps. In this brief, we show that the unavoidable nonidealities in the switching result in discontinuity in the map, which drastically changes the bifurcation structures. We demonstrate these effects experimentally, and develop simple one-dimensional models that account for switching delay and transients, and can predict the bifurcations in such systems with reasonable accuracy. Using the recent developments in bifurcation theory, we derive the limiting conditions for a reliable period-1 operation when these effects are considered.     

Designing a compact soft-start scheme for voltage-mode DC-DC switching converters

In this paper, a compact soft-start scheme is proposed and successfully applied to typical voltage-mode DC-DC switching converters. The adaptive current limitation implemented through DAC control will largely reduce the overshoot voltage under a wide range of output current. Proven experimentally by a buck converter implemented in a 0.5 μm CMOS technology, the post-simulation results show that when the converter starts up, the maximum overshoot (2.7% at I_LOAD=0 A) by the proposed soft-start scheme is less than that with the conventional scheme by 5% under the same condition. The start-up time can be adaptively adjustable depending on load current and the maximum start-up time is around 760 μs with 22 μF output capacitor. The circuits which realize the soft-start scheme can also be fully integrated into the control chip of DC-DC switching converter resulting in low cost.     

PWM-switch modeling of DC-DC converters

The introduced PWM-switch modeling method is a simple method for modeling pulse-width-modulated (PWM) DC-DC converters operating in the continuous conduction mode. The main advantage of this method is its versatility and simple implementation compared to other methods. The basic idea is the replacement of the switches in the converter by their time-averaged models. These switch models have been developed in such a way that the converter model provides the same results as the state-space-averaging technique but not including nonlinear effects. Simple rules for determination of the switch models are obtained. The resulting model is a time-averaged equivalent circuit model where all branch currents and node voltages correspond to their averaged values of the corresponding original currents and voltages. The model also includes parasitics, second-order effects and nonlinearities, and can be implemented in any circuit-oriented simulation tool. The same model is used for the simulation of the steady-state and the transient behavior     

NEW PERTURBATION TECHNIQUE FOR TRANSIENT ANALYSIS AND ITS APPLICATIONS IN DC-DC PWM SWITCHING POWER CONVERTERS

An improved perturbation technique proposed in a recent paper (Int. J. Electronics, vol. 63, pp.403-414) has been successfully applied to steady-state analysis of PWM switching converters. This paper extends the algorithm to transient analysis of a broader class of non-linear systems. As an example, the transient response of a Boost PWM switching converter is analyzed to demonstrate its simplicity and accuracy.     

Duty-cycle control boosts DC-DC converters

An improved design for a switched-capacitor pulsewidth modulated (PWM) DC-DC converter with adjustable conversion ratios is presented. The converter provides a nominal power of 40 W and nominal voltage conversion ratio of 12/5. The same structure can provide other conversion ratios, as required. Such low power supplies use relatively small, low-value capacitors, and could conceivably be realized with IC technology     

Novel zero-Voltage-transition PWM DC-DC converters

A new family of zero-voltage-switching (ZVS) pulsewidth-modulated (PWM) converters that uses a new ZVS-PWM switch cell is presented in this paper. Except for the auxiliary switch, all active and passive semiconductor devices in the ZVS-PWM converters operate at ZVS turn ON and turn OFF. The auxiliary switch operates at zero-current-switching (ZCS) turns ON and OFF. Besides operating at constant frequency, these new converters have no overvoltage across the switches and no additional current stress on the main switch in comparison to the hard-switching converter counterpart. Auxiliary components rated at very small current are used. The principle of operation, theoretical analysis, and experimental results of the new ZVS-PWM boost converter, rated 1 kW, and operating at 80 kHz, are provided in this paper to verify the performance of this new family of converters.     

Control features of dual-channel DC-DC converters

This paper presents the steady-state behavior of a two-channel resonant converter family in symmetrical operation. Six configurations will be investigated, including step-down, step-up/down, and step-up ones in continuous conduction mode (CCM) and in discontinuous conduction mode (DCM). Exploring the conditions of transition from CCM to DCM or back, it becomes evident that the CCM operation is definitely restricted, that is, sometimes the converter cannot he operated in CCM at all. The most important relations among the input, output, and control variables are derived and verified by simulation and experimental results.     

Automatic modeling of PWM DC-DC converters

Different small-signal models are available for describing the dynamics of pulse width modulators (PWM) dc-to-dc converters. Discrete time models reach the best compliance in real life situations. Some converter control modes, in particular phase shifting, provide advantages of modeling in discrete time. On the other hand, the burden of getting such exact models is often tedious. Currently, automatic tools are available that are able to provide the state-space model in discrete time of any PWM dc-dc converter switching at constant frequency. The authors claim that the use of these tools is advisable for the analysis and control optimization of switching power supplies. To support their opinion, this letter refers to a new, very accurate small-signal model of a phase-shifting converter which has been published recently. Its excellent performance, as well as the difficulties of the derivation procedure, are compared with the precise forecasts and the short processing time of an automatic modeling tool. The paper concludes in favor of automatic modeling.     

降压PWM DC/DC开关稳压系统仿真分析

集成CMOS脉冲宽度调制开关电源系统因为高效率、高集成度等优点在通信、计算机系统方面被广泛应用.文中通过分析建立一个PWM DC/DC稳压系统的闭环响应传输函数,研究如何在瞬态响应速度和稳定性方面进行取舍;在此基础上用Matlab建立小信号模型仿真,并通过Hspice 实现仿真验证.     

Design issues for monolithic DC-DC converters

This paper presents various ideas for integrating different components of dc-dc converter on to a silicon chip. These converters are intended to process power levels up to 0.5W. Techniques for integrating capacitors and design issues for MOS transistors are discussed. The most complicated design issue involves inductors. Expressions for trace resistance and inductance estimation of on-chip planar spiral inductor on top metal layer of CMOS process are compared. These inductors have high series resistance due to low metal trace thickness, capacitive coupling with substrate and other metal traces, and eddy current loss. As an alternative, a CMOS compatible three-dimensional (3-D) surface micromachining technology known as plastic deformation magnetic assembly (PDMA) is used to fabricate high quality inductors with small footprints. Experimental results from a monolithic buck converter using this PDMA inductor are presented. A major conclusion of this work is that the 3-D "post-process" technology is more viable than traditional integrated circuit assembly methods for realizing of micro-power converters.     

三电平DC-DC变换器的统一建模研究

三电平变换器的统一建模是对变换器进行控制和优化的基础.但是,对于三电平变换器而言,其开关数目多,工作模态复杂,用传统建模方法对之进行统一建模相当困难.脉冲波形积分法是一种新的统一建模方法,为此,本文首次采用脉冲波形积分法,对三电平变换器的统一建模进行了研究.以非隔离三电平变换器为例,详细阐明了其统一建模原理,并给出了输入输出共地和输入输出不共地的Buck变换器的统一建模方法.仿真分析与实验结果表明,脉冲波形积分法是一种对三电平变换器进行统一建模的有效工具,为三电平变换器的有效控制奠定了基础.     

Quasi-linear modeling and control of DC-DC converters

A quasi-linear approach is proposed for modeling and control of DC-DC power converters. The method presented is derived by perturbing an approximate large signal equation around a varying operating point in a reduced variable space. This differs from the usual practice of applying the perturbation technique around a fixed operating condition. In the proposed algorithm, the control equation and the control parameter are constantly adjusted according to environmental changes to meet the specified dynamical requirement     

Unified steady-state analysis of soft-switching DC-DC converters

In this paper, based on the switching cell approach, a unified steady state analysis for families of soft-switching DC-DC converters with complete unified design equations will be presented. The concept of the unified approach and step by step procedure for a generalized process are discussed and applied to selected soft-switching families such as zero-voltage-switching (ZVS) and zero-current-switching (ZCS)-quasi-resonant converter families, ZVS-clamped voltage quasi-square-wave (QSW) family, ZCS-clamped-current (CC) QSW family, and zero-voltage-transition and zero-current-transition pulse-width modulation families. Also, it has been noted that all the analyzed families have one generalized transformation table. The basic unified equations are summarized and the cell-to-cell comparison will be introduced. It will be shown that the unified analysis leads to several advantages such as improving the computer-aided analysis and design, simplified mathematical modeling, and giving more insight into the converter-cell operation.     

Active-clamp snubbers for isolated half-bridge DC-DC converters

In conventional isolated half-bridge dc-dc converters, the leakage-inductance-related losses degrade converter efficiency and limit the ability to increase the converters' switching frequencies. In this paper, a novel active-clamp snubber circuit for half-bridge dc-dc converters is proposed to recycle the energy stored in the leakage inductance by transferring this energy to a capacitor with zero-voltage zero-current-switching switched auxiliary switches, such that body-diode conduction of primary-side main switches are prevented and primary side ringing are attenuated resulting in improved converter efficiency. Principles of operation and simulation analysis are presented and supported by experimental results that show significant improvement in efficiency.     

Flyback DC-DC converters stabilized by using ripple

An instructive block diagram for development of the flyback DC-DC converters is given. Two derived examples, one from 5 V to 2000 V and another from 3 V to 7.5 V are presented. The converters use output ripple for direct determination of operating frequency which compensates all instabilities in the circuit except a change of a reference voltage. This approach is suitable for development of the supply for detectors and electronics in radiation protection instrumentation and other applications where load and source voltages are variable.