Controlled DC-DC Buck Converter Research Articles

Maximum Power Tracking and Current Control for Solar Photovoltaic System Applications, Hybrid Dynamical System Approach

The problem of a DC-DC buck converter control to extract the maximum power from a photovoltaic (PV) system is considered in this paper. A controller is proposed based on the hybrid dynamical system approach dealing with both voltage and current control. This approach allows the system to track a desired voltage using the maximum power point tracking (MPPT) algorithm while keeping the output current at a moderate level. The stability of the closed loop of the full system is demonstrated by means of Lyapunov theory. The simulation utilizes realistic PV array parameters obtained using particle swarm optimization (PSO) identification algorithm. Experimental results are also presented showing the good performance of the proposed controller.

DC transformer modeling and control of DC-DC buck converter

Switching Power Converters convert one form of power to another with high ef-ciency and accurate control.One of the most widely used DC-DC Converter is Buck Converter. Control is invariably required to maintain the output voltage/current in spite of variations in source/load. In order to design the controller and gain insight about the system a dynamic model needs to be developed. Modeling techniques widely used are state space averaging and PWM switch model. In this paper DC transformer modeling technique is used to develop the averaged model of the converter. One of the advantages of this model is that it can be implemented in Spice simulator using basic circuit elements. The same model can be used for time domain as well as frequency domain analysis. Analog type-II compensator is designed to compensate the system. Simulation and experimental results for start-up transient and load transient are shown to validate the model.

Optimized Active Disturbance Rejection Control for DC-DC Buck Converters With Uncertainties Using a Reduced-Order GPI Observer

The output voltage regulation problem of a PWM-based dc-dc buck converter under various sources of uncertainties and disturbances is investigated in this paper via an optimized active disturbance rejection control (ADRC) approach. Aiming to practical implementation, a new reduced-order generalized proportional integral (GPI) observer is first designed to estimate the lumped (possibly time-varying) disturbances within the dc-dc circuit. By integrating the disturbance estimation information raised by the reduced-order GPI observer into the output prediction, an optimized ADRC method is developed to achieve optimized tracking performance even in the presence of disturbances and uncertainties. It is shown that the proposed controller will guarantee the rigorous stability of the closed-loop system, for any bounded uncertainties of the circuit, by appropriately choosing the observer gains and the bandwidth factor. Experimental results illustrate that the proposed control solution is characterized by improved robustness performance against various disturbances and uncertainties compared with traditional ADRC and integral model predictive control (MPC) approaches.

Online Built-In Self-Test of High Switching Frequency DC–DC Converters Using Model Reference Based System Identification Techniques

A built-in self-test (BIST) technique that enables tracking of loop parameters of integrated DC–DC converters without affecting the normal mode of operation is presented. A digital pseudo-noise based stimulus and a mixed signal cross-correlation based analysis technique is used to derive on-chip impulse response, with minimum computational requirements in comparison to a digital correlator approach. Using measured impulse response, open-loop phase margin and closed-loop unity-gain frequency are estimated within 5.2% and 4.1% error, respectively, for the load current range of 30 mA to 200 mA. Converter parameters, such as natural frequency, $Q$ -factor, and center frequency are estimated within 3.6%, 4.7%, and 3.8% error, respectively, over load inductance of 4.7 $\mu \text{H}$ to 10.3 $\mu \text{H}$ , and filter capacitance of 200 nF to 400 nF. A 5 MHz switching frequency, 5 V to 8.125 V input voltage range, voltage-mode controlled DC-DC buck converter is designed for the proposed model reference based parametric and non-parametric BIST analysis. The converter output voltage range is 3.3 V to 5 V and supported maximum load current is 450 mA with a peak efficiency of 87.93%. The proposed converter is fabricated on a 0.6 $\mu \text{m}$ 6 layer-metal SOI technology with a die area of 9 mm2. The system identification circuitry occupies 3.8% of the converter area with 530 $\mu \text{A}$ quiescent current during operation.

A Reduced-Order Enhanced State Observer Control of DC-DC Buck Converter

This paper presents a reduced-order-enhanced state observer (RESO)-based control strategy for the PWM dc–dc buck converter. With the proposed RESO control strategy, the output voltage regulation of the dc–dc buck converter is able to achieve robust characteristics against the external disturbance and the internal parameter variation even without output current measurement. In addition, by incorporating the RESO in the controller, the output voltage regulation can be easily achieved with only a proportional gain to realize a zero steady-state error. Finally, the parameter design is discussed and the effectiveness of the proposed control strategy is verified with an experimental case study.

Unified control of DC-DC buck converter using dynamic adaptive controller for battery operated devices

The problem considered in this paper is improving the dynamic response of DC-DC converter system with internal parameter uncertainties. The methodology of sliding mode control in existing works is based on Proportional Integral and Derivative Controller (PID).The present work addresses various issues on a unified approach for design and application of pulse-width modulation (PWM) based Digital Adaptive Sliding Mode equivalent (ASM) control technique to buck converter for mobile phones operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The controller is gain scheduled to monitor the output loading condition, and adaptively changes the control parameters to give optimal dynamic performance corresponding to any load variations. Further stability is analytically verified using Lyapunov stability criterion and system is proved to be globally asymptotically stable. Finally effectiveness of proposed method is verified by simulation and experiment. Stable steady state response with reduced ripple is obtained.

Integrated Chip Current Mode DC-DC Buck Converter for Wireless Power Receiver

In this paper, we propose integrated chip DC-DC buck converter for wireless power receiver. The control of DC-DC buck converter is designed by current-mode technique. The DC-DC converter is an essential power management circuit that adjusts the output voltage based on portable electronic device applications. In addition, it reduces the energy loss due to thermal degradation and noise generated at power transmission. Therefore, DC-DC converter that operates at high efficiency is a major design constraint for wide input voltage variation. The proposed DC-DC converter is implemented andfabricated using 0.18μm BCD process. The DC-DC converter comprises of OTA, compensator, current sensing circuit, clock and ramp signal generator and a comparator. It is designed for 85% peak efficiency with a 1MHz switching frequency, 5.5V to 10V input voltage and 400mA maximum load current. The maximum accuracy for sensing current reaches 99%.

A control strategy for PV stand-alone applications

This paper proposes a stand-alone photovoltaic (PV) system study in domestic applications. Because of the decrease in power of photovoltaic module as a consequence of changes in solar radiation and temperature which affect the photovoltaic module performance, the design and control of DC-DC buck converter was proposed for providing power to the load from a photovoltaic source.In fact, the control of this converter is carried out with integrated MPPT (Maximum Power Point Tracking) algorithm which ensures a maximum energy generated by the PV arrays. Moreover, the output stage is composed by a battery energy storage system, dc-ac inverter, LCL filter which enables higher efficiency, low distortion ac waveforms and low leakage currents. The control strategy adopted is cascade control composed by two regulation loops.Simulations performed with PSIM software were able to validate the control system.The realization and testing of the photovoltaic system were achieved in the Photovoltaic laboratory of the Centre for Research and Energy Technologies at the Technopark Borj Cedria. Experimental results verify the effeciency of the proposed system.

FPGA-Based Expert PID Controller for Buck DC-DC Converter

In this paper, an expert PID controller used for digitally controlled DC-DC buck converters is proposed. It is designed bycombing expert theory with traditional PID theory, basing on the controlled objects and the knowledge of control laws. The controller uses the expert experiences to regulate the PID parameters online according to the dynamic characteristics of the system. The simulation and practical results indicated that, comparing with conventional PID controller, the expert PID controller which has faster startup transient response, smaller overshoot and more stable steady-state response, is better than conventional PID controller. It is well fit for the demand of control system.

Dynamics and Stability Issues of a Discretized Sliding-Mode Controlled DC-DC Buck Converter Governed by Fixed-Event-Time Switching

This paper finds and investigates the application of fixed-event-time based discretized sliding mode (DSM) controller in dc-dc buck converter, to achieve fast transient response and high robustness under wide parameters variation. We show that how these can be achieved by integrating the concept of Utkin's equivalent control law and discontinuous border-collision bifurcation (DBCB) theory developed for 2-D discontinuous piecewise smooth (PWS) maps. Moreover, based on derived 2-D discontinuous maps of DSM-controlled converter, we investigate its inherent steady-state dynamical properties or bifurcation behaviors under different parameters variation. Numerically as well as experimentally obtained bifurcation diagrams are then presented to show the domains of existence of different oscillatory modes and their sequence of occurrence. Such phenomena are not only useful to study the robustness of the system but may also facilitates to design the input filter with fast transient response. The performance of DSM controller is experimentally verified and compared with hysteresis and classical peak current-mode controller.

FPGA-based parallel architecture for PID control algorithm and HDL co-simulation

This paper aims to describe a dedicated high throughput parallel architecture for digital proportional-integral-derivative (PID) controller along with its field programmable gate array (FPGA) and application specific integrated circuit (ASIC) implementations. The processing speed of the controller depends on design of arithmetic units. In this context, this design incorporates parallel multipliers and a parallel adder to enhance the processing speed. This design is deeply pipelined to achieve high throughput. The algorithm is prototyped on Xilinx FPGA and implemented in 180 nm technology using cadence RTL complier. The performance of the controller is analysed by the results from a dc-dc buck converter control system through hardware descriptive language (HDL) co-simulation. Electronic design automation (EDA) simulator link interacts with hardware and software in MATLAB/Simulink environment and in this environment the response of the buck converter control system prior to hardware implementation is shown.

Simple Fuzzy PID Controllers for DC-DC Converters

A fuzzy PID controller design method is proposed for precise robust control of DC-DC buck converters. The PID parameters are determined reflecting on the common control engineering knowledge that transient performances can be improved if the P and I gains are big and the D gain is small at the beginning. Different from the previous fuzzy control design methods, the proposed method requires no defuzzification module and the global stability of the proposed fuzzy control system can be guaranteed. The proposed fuzzy PID controller is implemented by using a low-cost 8-bit microcontroller, and simulation and experimental results are given to demonstrate the effectiveness of the proposed method.

A 90–240 MHz Hysteretic Controlled DC-DC Buck Converter With Digital Phase Locked Loop Synchronization

This paper reports a digital phase locked loop (D-PLL) based frequency locking technique for high frequency hysteretic controlled dc-dc buck converters. The proposed converter achieves constant operating frequency over a wide output voltage range, eliminating the dependence of switching frequency on duty cycle or voltage conversion range. The D-PLL is programmable over a wide range of parameters and can be synchronized to a clock reference to ensure proper frequency lock and switching operation outside undesirable power supply resonance bands. The stability and loop dynamics of the proposed converter is analyzed using an analog equivalent PLL behavioral model which describes the dc-dc converter as a voltage-controlled oscillator (VCO). We demonstrate a 90-240 MHz single phase converter with fast hysteretic control and output conversion range of 33%-80%. The converter achieves an efficiency of 80% at 180 MHz, a load response of 40 ns for a 120 mA current step and a peak-to-peak ripple less than 25 mV. The circuit was implemented in 130 nm digital CMOS process.

Study of Sliding Mode Control of DC-DC Buck Converter

In this paper, a robust sliding mode controller for the control of dc-dc buck converter is designed and analyzed. Dynamic equations describing the buck converter are derived and sliding mode controller is designed. A two-loop control is employed for a buck converter. The robustness of the sliding mode controlled buck converter system is tested for step load changes and input voltage variations. The theoretical predictions are validated by means of simulations. Matlab/Simulink is used for the simulations. The simulation results are presented. The buck converter is tested with operating point changes and parameter uncertainties. Fast dynamic response of the output voltage and robustness to load and input voltage variations are obtained.

Low-frequency oscillation in digitally controlled DC-DC Buck converters

The z-domain model of digitally controlled Buck converter is derived by only considering the effect of sampler-and-holder. Based on the z-domain model, the cause of the low-frequency bifurcation is analyzed. The location and type of the bifurcation point when a system loses stability is predicted in terms of the system eigenvalues. Moreover, the frequency and the amplitude of the low-frequency oscillation, i.e., the wave equations, are deduced. These theoretical results are verified by PSpice simulations.

Design and analysis of adaptive sliding-mode-like controller for DC–DC converters

An adaptive sliding-mode-like controller for DC-DC buck converters is proposed. Constant switching frequency can be achieved with the proposed approach. An adaptive item is included to adjust the controller parameter online and eliminate the steady-state error. The adaptive scheme is based on a feedback policy that suitably modifies the corresponding power losses term in the controller equation. In addition, this adaptive term will speed up the system response and will stabilise the error dynamics of the closed-loop control system. The controller performance can be examined via traditional small-signal analysis. The implementation of the proposed closed-loop control scheme is illustrated with simulation and experiment.