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     

Low-power design of 8-b embedded CoolRisc microcontroller cores

Low-power and low-voltage embedded microcontrollers are required more and more for portable applications. Power reduction can be addressed at the software level as well as at the architecture level while searching to reduce the number of executed instructions for a given task. An 8-b RISC-like pipelined microcontroller family is presented achieving one clock per instruction. It is compared to various architectures of existing 8-b microcontrollers. According to an efficiency model taking into account the architecture as well as the number of registers, the presented 8-b microcontroller cores provide four to ten times better performances than existing microcontrollers. On one hand, the operating frequency can be reduced to execute a given task in the same execution time. On the other hand, delivering 10 MIPS performance, more than 2000 MIPS/W can be achieved at 3 V     

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.     

Implementation of pulse-width-modulation based sliding mode controller for boost converters

This letter addresses the various issues concerning the implementation of a pulse-width modulation (PWM) based sliding mode (SM) controller for boost converters. The methods of modeling the system and translation of the SM control equations for the PWM implementation are illustrated. It is shown that the control technique is easily realized with simple analog circuitries. Various experiments are conducted to test the static and dynamic performances of the system.     

A 5-V CMOS line controller with 16-b audio converters

A 5-V CMOS line controller is presented. The circuit was designed using a 2-μm CMOS technology with two layers of polysilicon and two layers of metal. The total circuit area is 15 mm², of which 6.5 mm² is used for converters, 1.6 mm² for the DC feed controller, and 1.5 mm² for the digital interface; the rest is overhead for periphery. Audio converter performances, such as 16-b dynamic range or 15-b A/D linearity, and their stability over process and operating condition variations point out the efficiency and robustness of the selected design techniques. These are a tone-tolerant second-order delta-sigma modulator design, a matching-independent 2-b D/A conversion scheme, a clock-feedthrough compensation technique, and a two-stage amplifier with a noise bandwidth limited by the switches. Converter performances and DC feed controller absolute accuracy and programmability match the new line card design targets and indicate that this circuit is viable for large volume production     

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.     

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.     

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     

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.     

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.     

Random discrete PWM method for DC-DC power converters

A random discrete pulse-width modulation (RDPWM) scheme is examined and compared with the randomised pulse-position modulation (RPPM) method for DC-DC power conversion. The RDPWM method has no switching harmonics while the RPPM method has significant switching harmonics. Power spectral characteristics of the two methods are presented and discussed     

High-performance error amplifier for fast transient DC-DC converters

A new error amplifier is presented for fast transient response of dc-dc converters. The amplifier has low quiescent current to achieve high power conversion efficiency, but it can supply sufficient current during large-signal operation. Two comparators detect large-signal variations, and turn on extra current supplier if necessary. The amount of extra current is well controlled, so that the system stability can be guaranteed in various operating conditions. The simulation results show that the new error amplifier achieves significant improvement in transient response than the conventional one.     

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.     

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.     

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.     

An improved cosine-mode controller for SCR converters

An improved cosine-mode controller for silicon-controlled rectifier (SCR) power converters is presented. The proposed scheme linearizes the input/output transfer function of SCR power converters. The replacement of monostables by AND gates in the controller eliminates false turn-ons due to bouncing inside analog comparators. Experiments have been performed and satisfactory results are recorded     

Optimal controller of a buck DC-DC converter using the uncertain load as stochastic noise

This work presents an optimal design approach for the pulsewidth modulation switching control of a buck DC-DC converter by modeling the converter as a stochastic linear system with noise of uncertain load. Firstly, we temporarily assume that the stochastic system is available with complete state, and then derive an optimal state feedback control for the optimal noise regulation in steady state. Secondly, from the steady-state viewpoint, the optimal state feedback control is transferred into an equivalent error-driven servo controller, and then the designed optimal control law is implemented using a phase lead-lag controller. A distinctive advantage of this approach is that the optimal controller's parameters are actually independent of the statistics of the assumed uncertain load noise, so the benefit of optimal noise regulation is assured for global operation. Furthermore, the optimal controller is easily implemented. As a matter of fact, by just using the simplest possible operation amplifier circuits, the controller can be implemented.