Voltage-mode Control Scheme Research Articles

고효율 및 슬림형 전압 평형 3-레벨 벅 컨버터

The 3-level buck converter features half the switch voltage stress of the conventional synchronous buck converter. The operating frequency of the output inductor is also twice the switching frequency. The slope of the inductor current can be reduced as well due to the flying capacitor voltage, which can greatly reduce the size of the output inductor. Therefore, the 3-level buck converter can achieve high efficiency and high power density. The flying capacitor voltage must be half the input voltage to achieve the abovementioned strength. Most conventional control schemes for the voltage balance of the flying capacitor adopt a peak or valley current mode control method using real-time current sensing. Therefore, the control algorithm is complicated, and high performance and expensive digital controller is required. This study proposes an independent two-loop voltage mode control scheme that can guarantee the flying capacitor voltage to be half of the input voltage. The proposed control scheme can be simply implemented without current detection and does not require complicated control algorithms. Thus, simple and low-cost micro controller can be used. Experimental results from a rated prototype of 500 W are provided to verify the performance of the proposed control scheme.

Design-oriented fast response voltage mode buck converter with adaptive ramp control

This paper proposes a new adaptive ramp voltage mode control scheme. Instead of using the conventional slow compensation path of the voltage mode, the proposed scheme adds an extra feedback path to adjust the amplitude and DC-offset of the ramp signal and to directly accelerate the duty cycle according to the output voltage variation. In addition, a design-oriented analytical method is adopted to intuitively analyzes the loop characteristics and provides accurate instructions for the implementation and optimization of the compensator. A 5–1 V buck converter is implemented in the proposed adaptive ramp control scheme with optimized compensation. Simulation and measurement results show that the converter achieves a bandwidth of up to 591 kHz with a 3 MHz switching frequency and a 65° phase margin. In addition, the undershoot voltage and the recovery time are 16 mV and 19 μs with a load change from 0.5 to 1 A. The proposed control scheme shows superior transient response performance while maintaining fixed frequency operations with a simple system structure.

Improved Set-Point Tracking and Disturbance Rejection of DC–DC Converters Using Voltage-Mode Digital Control

In this article, a voltage-mode control scheme with two degrees of freedom is developed for improving servo and regulatory responses of a boost-type dc–dc converter operated in the continuous conduction mode. The servo behavior is shaped using two model-based digital controllers, namely modified Dahlin’s controller (MDC) and the Vogel–Edgar controller (VEC). To handle input saturation during the transients, a novel antireset windup scheme is proposed and integrated with VEC and MDC. To improve the regulatory response, without altering the design of VEC or MDC, a model-based robust internal-loop compensator (RIC) is introduced, which attempts to reject unmeasured disturbances before the feedback controller can start reacting to their effects. To assess the efficiency of the proposed integrated control scheme, simulation studies and experimental verifications have been carried out for a variety of servo and regulatory scenarios. Analysis of simulation results reveals that if tuning parameters of the RIC are chosen judiciously, then the proposed scheme significantly improves the regulatory behavior of VEC and MDC without significantly altering their servo behavior. The closed-loop responses obtained in the experimental evaluations closely resemble the responses of simulations and corroborate conclusions reached through the analysis of simulation results.

Sliding-Mode Control of AC Voltages and Currents of Dispatchable Distributed Energy Resources in Master-Slave-Organized Inverter-Based Microgrids

This paper proposes a current-controlled voltage-mode control scheme for dispatchable electronically coupled distributed energy resource (DER) units based on sliding-mode control (SMC) strategy. The proposed control strategy provides fast and stable control on the terminal voltage and frequency of DER unit and ensures protection of the power-electronic interface to external faults. In addition it maintains the quality of the output voltage of the host DER unit in spite of unbalanced and/or distorted load currents. Performance of the proposed SMC strategy is demonstrated through time-domain simulation of a single islanded DER unit, starting from black-start and subjected to various operating scenarios, and it is compared to the performance of a proportional-integral (PI) based control strategy. Also a current-mode control strategy is proposed for DER units based on SMC. The performance of both voltage- and current-mode control strategies are demonstrated in a sample master-slave organized three-unit microgrid.

Dynamic Power Management System Employing a Single-Stage Power Converter for Standalone Solar PV Applications

This paper presents a dynamic power flow management system for a solar photovoltaic (PV) system employing a single-stage single-inductor-based dual-input/output dc–dc converter feeding standalone dc loads backed up by a rechargeable battery. A time-sharing voltage-mode control scheme has been proposed for power flow management between solar PV, a battery, and a standalone dc load, and it also maintains a constant dc load voltage and performs maximum power point tracking operation of solar PV. The implementation of the control scheme has been described in detail. The steady-state performance of the single-stage converter has been explained with the relevant analytical expressions derived along with the characteristics. A state-space average model was developed for simulating the transient behavior and validating the working of the system for step changes in the input solar PV power and the dc loads. A hardware prototype of the proposed system has been fabricated, and the proposed controller has been implemented using the dSPACE DS1103 real-time interface board. The working of the proposed scheme for different levels of input solar insolation and dc load power demand has been satisfactorily demonstrated, and the corresponding results are also provided.

A Highly Integrated Series–Parallel Switched-Capacitor Converter With 12 V Input and Quasi-Resonant Voltage-Mode Regulation

This paper presents an integrated circuit (IC) implementation of a hybrid switched capacitor converter based on a modified series-parallel architecture. The converter operates in a quasi-resonant mode to regulate a nominal 3.7 V output from a 12 V supply. The design uses zero-current detection and nested 1-b regulation to autotune the zero-current switching state, simplify the design of a digital voltage-mode control scheme, and achieve partial zero-voltage switching. The modified architecture is able to operate with single-voltage rated devices without degrading the voltage times current product of the converter. This paper discusses details of level shifting, gate driving, and bootstrapping for an all n-channel powertrain, including a precharge circuit, to facilitate safe startup. The converter IC was designed in 180-nm bulk CMOS with a 5 V option for power devices. It was tested in a flip-chip assembly with a 36 nH 0402 inductor to deliver up to 4.6 W at 87.5% efficiency at a power density of 0.23 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Achieving Monotonic Variation of Spectral Composition in DC–DC Converters Using Pulse Skipping Modulation

This paper presents a new type of pulse skipping modulation (PSM) in a dc-dc converter, which is controlled by a voltage mode scheme. The duty ratio of the pulses, instead of being constant as in the conventional PSM, is controlled using a voltage mode control scheme along with a feed-forward path of the input voltage and an adjustable voltage. In the conventional PSM, spectral composition varies nonmonotonically which results in problems due to electromagnetic interference (EMI). We show, both analytically and experimentally, that the proposed scheme results in monotonic spectral behavior for a wide range of input voltage and load resistance. Hence one can obtain the small signal model of the system. Because of the synchronism with the external clock, it facilitates the design of an input filter for reduction of EMI.

Two-loop voltage-mode control of coupled inductor step-down buck converter

A simple two-loop voltage mode control scheme for the two inductor step-down buck converter is proposed. This is a voltage-mode control scheme in which the external sawtooth generator for the PWM generation is not required. The controller implementation requires only a single error amplifier and gives almost current-mode control performance. The proposed converter gives lower ripple in the input current and reduces the input filtering requirements as compared to the conventional buck topology. To reduce the input current ripple even more, integrated magnetic components with ripple steering phenomena are proposed. For modelling the converter a signal-flow-graph approach is developed to find the converter open, closed-loop small-signal transfer functions and to eliminate the complexity in the mathematical analysis. A unified signal-flow-graph model of the converter, from which the complete behaviour can be predetermined, is developed. Effectiveness of the proposed control scheme and performance improvement is demonstrated through simulations. Experimental results of load voltage regulation against line and load changes are provided to validate the proposed modelling and control scheme.

SINGLE-LOOP CURRENT-MODE CONTROL OF A PWM BOOST DC-TO-DC CONVERTER WITH A NON-SYMMETRIC PHASE CONTROLLER

An extensive small-signal analysis of a single-loop current-mode control strategy for a pulse-width-modulated (PWM) boost DC-to-DC power converter operating in continuous conduction mode (CCM) is proposed using a new non-symmetric phase controller. To model the boost power stage, a linear circuit model is used which includes all parasitic components such as the equivalent series resistance (ESR) of the filter capacitor, the ESR of the inductor, the transistor ON-resistance, and the diode forward resistance and offset voltage. A boost power stage design example gives component design equations and will serve to illustrate the closed-loop converter design. A design procedure for the new non-symmetric phase controller is presented. Open-loop and closed-loop circuit models and transfer functions are derived for the boost PWM converter and illustrated by Bode plots. An approach is presented for simplifying closed-loop transfer functions, using Euler's identity, into a format which is conducive to modeling in any high level programming language on a personal computer. Bode plots are obtained using a data analysis software package Axum 3.0 which combines a programming language, spread-sheet, and publication quality technical graphics. The proposed control scheme directly controls the inductor current and indirectly controls the load current and output voltage. The closed-loop transfer functions of the proposed control scheme do not contain a righthalf plane (RHP) zero, in contrast to the closed-loop transfer functions of a single-loop voltage-mode control scheme. The absence of the RHP zero provides better stability by making it easier to obtain large or specified gain and phase margins.