Adaptive Efficiency Optimization For Digitally Controlled Dc-dc Converters

The design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement at that design point because of the components, temperature, and operating point variations. The ability of digital controllers to perform sophisticated algorithms makes it easy to apply adaptive control, where system parameters can be adaptively adjusted in response to system behavior in order to achieve better performance and stability. The use of adaptive control for power electronics is first applied with the Adaptive Frequency Optimization (AFO) method, which presents an auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency. The AFO controller adjusts the DC-DC converter switching frequency while tracking the converter minimum input power point, under variable operating conditions, to find the optimum switching frequency that will result in minimum total loss and thus the maximum efficiency. Implementing variable switching frequencies in digital controllers introduces two main issues, namely, limit cycle oscillation and system instability. Dynamic Limit Cycle Algorithms (DLCA) is a dynamic technique tailored to improve system stability and to reduce limit cycle oscillation under variable switching frequency operation. The convergence speed and stability of AFO algorithm is further improved by presenting the analysis and design of a digital controller with adaptive auto-tuning algorithm that has a variable step size to track and detect the optimum switching frequency for a DC-DC converter. The Variable-Step-Size (VSS) algorithm is theoretically analyzed and developed based on buck DC-DC converter loss model and directed towered improving the convergence speed and accuracy of AFO adaptive loop by adjusting the converter switching frequency with variable step size. Finally, the efficiency of DC-DC converters is a function of several variables. Optimizing single variable alone may not result in maximum or global efficiency point. The issue of adjusting more than one variable at the same time is addressed by the Multivariable Adaptive digital Controller (MVAC). The MVAC is an adaptive method that continuously adjusts the DC-DC converter switching frequency and dead-time at the same time, while tracking the converter minimum input power, to find the maximum global efficiency point under variable conditions. In this research work, all adaptive methods were discussed, theoretically analyzed and its digital control algorithm along with experimental implementations were presented

Unified Steady-state Computer Aided Model For Soft-switching DC-DC Converters

For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a simulation block that covers common unified soft-switching cells operations and can be used in topologies simulation. The simulation block has a simple interface that enables the user to choose the switching cell type and connects the developed simulation model in the desired topology configuration. In addition to the measured information that can be obtained from the circuitry around the unified simulation model, the simulation block includes some additional nodes (other than the inputs and outputs) that make internal switching cell information, such as switching voltages and currents, easy to access and debug. The model is based on mathematical equations, resulting in faster simulation times, smaller file size and greatly minimized simulation convergence problems. The Unified Model is based on the generalized analysis: Chapter 1 discusses the generalized equation concept along with a detailed generalization example of one switching cell, which is the zero current switching quasi-resonant converter ZCS-QRC. Chapter 2 presents a detailed discussion of the unified model concept, the unified model flow chart and the unified model implementation in Pspice. Chapter 3 presents the unified model applications; generating the switching cell inductor current and the switching cell capacitor voltage steady-state waveforms, the State-Plane Diagram , the feedback design using the unified model, and the chapter concludes with how the model can be used with different topologies. Finally, chapter 4 presents the summary and the future wor

Unified Steady-State Computer Aided Model For Soft-Switching Dc-Dc Converters

A unified steady state Pspice® model is developed for soft-switching cells in this paper to facilitate the simulation and design of soft-switching cells and to provide designers, educators, and students with time domain response figures, accurate steady-state gain solution, and state-plane diagrams. The model concept and mathematical equations behind the model are discussed. Pspice implementation concepts are summarized and a simulation example with simulation results is presented. © 2006 IEEE

Design Considerations And Expiremantal Results Of An Adaptive Frequency Controller Under Variable Line And Load Conditions

This paper presents critical design guidelines and consideration for the adaptive step size function of the previously proposed ASSAT controller that tracks the optimum switching frequency with improved convergence speed and accuracy to maximize power converter efficiency. It is revealed how the adaptive step size function is affected by several factors and it is shown how the function should be designed to guarantee good convergence stability, speed, and accuracy. The design is verified by experimental results. ©2010 IEEE

Dsp-Based Stable Control Loops Design For A Single Stage Inverter

The design of stable DSP-based controller for a new single stage inverter architecture with solar energy input is discussed in this paper. The proposed architecture uses two dependent control loops to track the maximum available power of a solar array source, and to supply a sinusoidal current to the utility grid. If not well designed, the control loops in this inverter configuration suffer from instability when operating at different regions of the solar array power curve, namely the Right Hand Side region (RHS) and the Left Hand Side region (LHS). This paper presents a mathematical analysis to the source of instability, and proposes a robust controller for stable system design. Experimental results are presented to verify the validity of the designed controller. © 2006 IEEE

Analysis And Experimental Results For A Multivariable Adaptive Digital Controller

A Multivariable Adaptive digital Controller to optimize DC-DC converter switching frequency and dead-time at the same time, for maximum efficiency under variable conditions, is presented in this paper. The Multivariable Adaptive digital Controller (MVAC) adaptively adjusts the DC-DC converter switching frequency and dead-time while tracking the converter minimum input power (maximum efficiency) point under variable conditions including variable load, variable input voltage and variable temperatures. In this paper, the MVAC method is discussed and analyzed. MVAC digital control algorithm and experimental implementation are presented. © 2010 IEEE

Drive Voltage Optimization Controller To Improve Efficiency

An adaptive digital controller with maximum efficiency point tracking to optimize the FETs\u27 switches driving-voltage is presented in this paper. The Driving-Voltage-Optimization (DVO) method adaptively changes the FETs driving voltage magnitude while tracking the converter minimum input current/power (maximum efficiency) point. The DVO digital controller continuously finds the optimum FETs driving voltage that will result in a minimum total combined FETs driving and conduction losses while converter parameters and conditions vary. In this paper, the DVO method is discussed, analyzed, and its digital control algorithm and experimental implementation are presented. ©2006 IEEE

Design Considerations And Dynamic Technique For Digitally Controlled Variable Frequency Dc-Dc Converter

A dynamic algorithm to avoid limit cycle oscillation problems and to improve stability in digitally controlled power converters with variable switching frequency operation is presented in this paper. Employing Variable switching frequency at light loads is one way to improve the efficiency of DC-DC converters. However, varying the switching frequency digitally introduces additional considerations that do not exist in variable frequency analog controllers. In this paper a dynamic algorithm to maintain system stability and dynamics at different switching frequencies and to avoid limit cycle oscillation problems is discussed and experimentally verified. © 2007 IEEE

Adaptive Variable Switching Frequency Digital Controller Algorithm to Optimize Efficiency

An adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency is presented in this paper. The Adaptive-Frequency-Optimization (AFO) method changes the DC-DC converter switching frequency while tracking the converter minimum input power (maximum efficiency) point under variable conditions including variable load and variable input voltage. The AFO digital controller continuously finds the optimum switching frequency that will result in the minimum total loss while converter parameters and conditions vary. In this paper, the AFO method is discussed analyzed and its digital control algorithm and experimental implementation are presented. © 2007 IEEE

Adaptive Variable Switching Frequency Digital Controller Algorithm To Optimize Efficiency

An adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency is presented in this paper. The Adaptive-Frequency-Optimization (AFO) method changes the DC-DC converter switching frequency while tracking the converter minimum input power (maximum efficiency) point under variable conditions including variable load and variable input voltage. The AFO digital controller continuously finds the optimum switching frequency that will result in the minimum total loss while converter parameters and conditions vary. In this paper, the AFO method is discussed analyzed and its digital control algorithm and experimental implementation are presented. © 2007 IEEE