One-cycle control of switching converters

A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects switching errors in one switching cycle. There is no steady-state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with a constant frequency buck converter have demonstrated the robustness of the control method and verified the theoretical predictions. This new control method is very general and applicable to all types of pulse-width-modulated, resonant-based, or soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode. Furthermore, it can be used to control any physical variable or abstract signal that is in the form of a switched variable or can be converted to the form of a switched variable

STUDY OF FULLY-INTEGRATED LOW-DROPOUT REGULATORS

Department of Electrical EngineeringThis thesis focuses on the introduction of fully-integrated low-dropout regulators (LDOs). Recently, for the mobile and internet-of-things applications, the level of integration is getting higher. LDOs get popular in integrated circuit design including functions such as reducing switching ripples from high-efficiency regulators, cancelling spurs from other loads, and giving different supply voltages to loads. In accordance with load applications, choosing proper LDOs is important. LDOs can be classified by the types of power MOSEFT, the topologies of error amplifier, and the locations of dominant pole. Analog loads such as voltage-controlled oscillators and analog-to-digital converters need LDOs that have high power-supply-rejection-ratio (PSRR), high accuracy, and low noise. Digital loads such as DRAM and CPU need fast transient response, a wide range of load current providable LDOs. As an example, we present the design procedure of a fully-integrated LDO that obtains the desired PSRR. In analog LDOs, we discuss advanced techniques such as local positive feedback loop and zero path that can improve stability and PSRR performance. In digital LDOs, the techniques to improve transient response are introduced. In analog-digital hybrid LDOs, to achieve both fast transient and high PSRR performance in a fully-integrated chip, how to optimally combine analog and digital LDOs is considered based on the characteristics of each LDO type. The future work is extracted from the considerations and limitations of conventional techniques.clos

Dynamic analysis and QFT-based robust control design of switched-mode power converters

The use of switched-mode power converters is continuously growing both in power electronics products and systems, e.g. in Telecom applications, commercial grid systems etc. The switching converters are required to provide robust behavior and to operate without instability under a variety of operation conditions. Hence the converter system may be subject to disturbances due to load, input voltage, and system parameter variations. In the thesis a robust control design procedure based on the QFT method (Quantitative Feedback Theory) is applied successfully for switching-mode DC-DC converters in order to achieve robust output in spite of different uncertainties. Simulation results are presented to demonstrate and validate the control design, showing good dynamic performance of the QFT controller. When designing large-scale systems it is often impractical to analyze and design the system as a whole. Instead, it is desirable to divide the system into manageable subsystems which can then be designed independently. The subsystems may then be connected together to form a complete integrated system. One of the major difficulties in integrated subsystems is the stability performance degradation due to the interaction between the subsystems. A formalism to analyze the interaction between subsystems using the unterminated two-port small-signal representation is derived. Two-port models are first defined as unterminated models, where the effect of load is excluded but may be easily included using the developed reflection rules. The use of the impedance ratio as a minor loop gain, which can be used to check system stability, is outlined. Recently, there has been increasing interest in the parallel operation of DC-DC converters for reasons of increasing system reliability, facilitating system maintenance, allowing for future expansion, and reducing system design cost. However, paralleled DC-DC converters require a systematic modeling methodology and a categorical current-sharing mechanism to improve a performance of the overall system. In order to achieve desirable characteristics when operating converter modules in parallel, a unified systematic approached for modeling of parallel DC-DC converter with current-sharing control, is proposed, developed, and analyzed

Switched Capacitor DC-DC Converter for Miniaturised Wearable Systems

Motivated by the demands of the integrated power system in the modern wearable electronics, this paper presents a new method of inductor-less switched-capacitor (SC) based DC-DC converter designed to produce two simultaneous boost and buck outputs by using a 4-phases logic switch mode regulation. While the existing SC converters missing their reconfigurability during needed spontaneous multi-outputs at the load ends, this work overcomes this limitation by being able to reconfigure higher gain mode at dual outputs. From an input voltage of 2.5 V, the proposed converter achieves step-up and step-down voltage conversions of 3.74 V and 1.233 V for Normal mode, and 4.872 V and 2.48 V for High mode, with the ripple variation of 20–60 mV. The proposed converter has been designed in a standard 0.35 μm CMOS technology and with conversion efficiencies up to 97–98% is in agreement with state-of-the-art SC converter designs. It produces the maximum load currents of 0.21 mA and 0.37 mA for Normal and High modes respectively. Due to the flexible gain accessibility and fast response time with only two clock cycles required for steady state outputs, this converter can be applicable for multi-function wearable devices, comprised of various integrated electronic modules

Semiconductor optical amplifiers: performance and applications in optical packet switching [Invited]

Semiconductor optical amplifiers (SOAs) are a versatile core technology and the basis for the implementation of a number of key functionalities central to the evolution of highly wavelength-agile all-optical networks. We present an overview of the state of the art of SOAs and summarize a range of applications such as power boosters, preamplifiers, optical linear (gain-clamped) amplifiers, optical gates, and modules based on the hybrid integration of SOAs to yield high-level functionalities such as all-optical wavelength converters/regenerators and small space switching matrices. Their use in a number of proposed optical packet switching situations is also highlighted

Diffractive sidewall grating coupler: towards 2D free-space optics on chip.

Silicon photonics has been the subject of intense research efforts. In order to implement complex integrated silicon photonic devices and systems, a wide range of robust building blocks is needed. Waveguide couplers are fundamental devices in integrated optics, enabling different functionalities such as power dividers, spot-size converters, coherent hybrids and fiber-chip coupling interfaces, to name a few. In this work we propose a new type of nanophotonic coupler based on sidewall grating (SIGRA) concept. SIGRAs have been used in the Bragg regime, for filtering applications, as well as in the sub-wavelength regime in multimode interference (MMI) couplers. However, the use of SIGRAs in the radiation regime has been very limited. Specifically, a coarse wavelength division multiplexer was proposed and experimentally validated. In this work we study the use of SIGRAs in the diffractive regime as a mean to couple the light between a silicon wire waveguide mode and a continuum of slab waveguide modes. We also propose an original technique for designing SIGRA based couplers, enabling the synthesis of arbitrary radiation field profile by Floquet- Bloch analysis of individual diffracting elements while substantially alleviating computational load. Results are further validated by 3D FDTD simulations which confirm that the radiated field profile closely matches the target design field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Self-oscillating control methods for the LCC current-output resonant converter

Abstract—A strategy for self-oscillating control of LCC current-output resonant converters, is presented, based on varying the phase-angle between the fundamental of the input voltage and current. Unlike other commonly employed control methodologies,the proposed technique is shown to provide a convenient, linear system input-output characteristic suitable for the design of regulators. The method is shown to have a similar effect as controlling the dc-link supply voltage, in terms of output-voltage/current control. The LCC converter variant is used as an application focus for demonstrating the presented techniques, with simulation and experimental measurements from a prototype converter being used to show the practical benefits. Third-order small and large-signal models are developed, and employed in the formulation of robust output-voltage and output-current control schemes. However, notably, the presented techniques are ultimately generic and readily applicable to other resonant converter variants