Prognostics and health management of light emitting diodes

Prognostics is an engineering process of diagnosing, predicting the remaining useful life and estimating the reliability of systems and products. Prognostics and Health Management (PHM) has emerged in the last decade as one of the most efficient approaches in failure prevention, reliability estimation and remaining useful life predictions of various engineering systems and products. Light Emitting Diodes (LEDs) are optoelectronic micro-devices that are now replacing traditional incandescent and fluorescent lighting, as they have many advantages including higher reliability, greater energy efficiency, long life time and faster switching speed. Even though LEDs have high reliability and long life time, manufacturers and lighting systems designers still need to assess the reliability of LED lighting systems and the failures in the LED. This research provides both experimental and theoretical results that demonstrate the use of prognostics and health monitoring techniques for high power LEDs subjected to harsh operating conditions. Data driven, model driven and fusion prognostics approaches are developed to monitor and identify LED failures, based on the requirement for the light output power. The approaches adopted in this work are validated and can be used to assess the life of an LED lighting system after their deployment based on the power of the light output emitted. The data driven techniques are only based on monitoring selected operational and performance indicators using sensors whereas the model driven technique is based on sensor data as well as on a developed empirical model. Fusion approach is also developed using the data driven and the model driven approaches to the LED. Real-time implementation of developed approaches are also investigated and discussed

Prognostics and health monitoring of high power LED

Prognostics is seen as a key component of health usage monitoring systems, where prognostics algorithms can both detect anomalies in the behaviour/performance of a micro-device/system, and predict its remaining useful life when subjected to monitored operational and environmental conditions. Light Emitting Diodes (LEDs) are optoelectronic micro-devices that are now replacing traditional incadescent and fluorescent lighting, as they have many advantages including higher reliability, greater energy efficiency, long life time and faster switching speed. For some LED applications there is a requirement to monitor the health of LED lighting systems and predict when failure is likely to occur. This is very important in the case of safety critical and emergency applications. This paper provides both experimental and theoretical results that demonstrate the use of prognostics and health monitoring techniques for high power LEDs subjected to harsh operating conditions

GAN LIGHT EMISSION CONTROLLED DC-DC CONVERTER

This work demonstrates the very first implementation of electroluminescence from a gallium nitride vertical diode as a feedback mechanism for real-time current control of a power converter. Current estimation via electroluminescence provides a galvanically isolated sensor capability that is not susceptible to electromagnetic interference, which is inherently produced in switch mode power supplies. The light feedback is converted to an electrical signal that is further digitally filtered to construct a 3D current calibration surface. This surface converts duty cycle and light signal intensity into a real-time current estimation utilized as a feedback parameter in a buck converter control system. The accuracy of current estimation is shown to be within 5% of steady-state current over various load conditions. Transient-state response was also demonstrated for step changes in commanded current and voltage within the power converter. Methods of increasing accuracy and reducing current estimation delay time are discussed.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

Study and analysis of state-of-the-art FCS-MPC strategies for thermal regulation of power converters

La degradación en los convertidores de potencia basados en silicio, enmarcados en sistemas de tracción eléctrica y fuentes de energías renovables, es un tema de estudio de especial interés para aquellas aplicaciones donde los fallos amenazan la seguridad de personas o donde el mantenimiento es particularmente costoso. Motivado por la influencia de los fallos en IGBTs sobre los fallos habituales en los convertidores de potencia comunes, este trabajo utiliza la herramienta software PLECS como marco de trabajo para la simulación de algoritmos de control predictivo basado en modelo con conjunto finito de acciones de control (FCS-MPC) que pretenden -simultáneamente a conseguir el seguimiento eléctrico- extender directa o indirectamente la vida útil de los IGBTs. El trabajo se enfoca principalmente a la simulación en ordenador de los algoritmos controlando un inversor de dos niveles conectado a una carga RL. Además, pretende también introducir la implementación de éstos sobre un microcontrolador para su estudio controlando el inversor simulado en la plataforma PLECS RT Box 1, con el fin último de poder desarrollar validaciones de los controladores basadas en técnicas Hardware-In-the-Loop.Degradation of silicon-based power electronics converters in traction and renewable energy systems is a topic of interest particularly where module failure supposes a safety threat or where maintenance becomes especially expensive. Motivated by the influence of IGBT aging in usual power converters, this work uses the software tool PLECS as framework to simulate Finite Control Set Model Predictive Control (FCSMPC) algorithms that, simultaneously to achieving a certain current tracking, aim to directly or indirectly extend IGBTs’ lifetime. Whilst the work focuses on offline simulation of the algorithms on PLECS, it also targets to pave the way to implement algorithms in a micro-controller and to study how they control a two-level inverter connected to a RL load simulated on a PLECS RT Box 1 platform. The ultimate goal is to develop validations based on Hardware-In-the-Loop techniques of the control algorithms.Universidad de Sevilla. Máster Universitario en Ingeniería Electrónica, Robótica y Automátic

Design and implementation of an electronic system for a microgravity experiment

The focus of this thesis is to design and develop a complete electronic system consisting of a heating subsystem, an acoustic wave subsystem, and an instrumentation subsystem for an experiment in microgravity. The aim of this work is to ensure the correct performance of all these subsystems in order to demonstrate that convection can be achieved using acoustic waves in microgravity conditions

A Low-Power Optoelectronic Characterizer for CubeSat: LOCC and III-V Nitride Based LEDs

III-V semiconductor materials exhibit robustness and natural hardness when exposed to ionizing radiation and temperature swings. With these characteristics in mind, III-V Nitride Light Emitting Diodes (LEDs) are ideal devices for space-based applications and missions. The effects of ionizing radiation on optoelectronic devices comprised of III-V materials have been studied, but results have been obtained through experiments performed in terrestrial laboratories. While these laboratory tests may lend insight into device lifetimes, performance degradation, etc., they are no substitute for similar measurements and characterization performed in space.;Interest in small satellite applications have grown over the past decade. These solutions range from Earth imaging to communication networks. Small satellites provide a unique opportunity to gain an understanding of the reliability and operational characteristics of III-V based materials and other semiconductor devices while exposed to the environment of space. To meet the constraints of the small satellite, a Low-powered Optoelectronic Characterizer for CubeSat (LOCC) has been developed in PC/104 form, measuring 3.6 by 3.8 inches. LOCC performs current-voltage and electroluminescent measurements of LEDs while in space. The LOCC system is designed using low-power integrated circuits that can supply over 100 mA of current to LEDs while maintaining low power of 3.2W under operation.;This thesis presents the design, implementation, and control of the LOCC system. This includes system block diagrams, printed circuit board layouts, interfacing, firmware, and software. Additionally, the resulting current-voltage measurements, required wattage, and required data storage are presented to illustrate functionality. This instrumentation enables the study of optoelectronic devices in space, allowing future research to focus on producing radiation hard light emitting devices that can operate in environments with reduced shielding against ionizing radiation while maintaining device reliability

Estimation of the Internal Junction Temperatures of Resin Encapsulated IGBT Power Modules

Power electronics converters used in applications requiring high reliability require an accurate thermal manage- ment for each component. Therefore, several methods for the estimation of the junction temperature of power devices are reported in the literature, having different features in terms of sensitivity, linearity and calibration process. Nevertheless, state of the art technologies in power modules packaging, such as the resin encapsulation technology, have shown that junction temperature estimation is still an open issue. In such modules, the lack of physical access to the die has led a growing interest in estimation methods based on thermo-sensitive electrical parame- ters. This paper proposes a non-invasive method for the junction temperature estimation of high current resin encapsulated IGBT power modules. The proposed solution is suitable for the thermal model validation of industrial converters thanks to the off-the- shelf components and the easiness of implementation

Temperature controlled light-emitting diode lamp for photovoltaic rural applications

In recent years, interest in light-emitting diode (LED) lighting has been growing because of its high efficacy, lifetime and ruggedness. This paper proposes a better adaptation of LED lamps to the technical requirements of photovoltaic lighting domestic systems, whose main quality criteria are reliability and that behave as voltage power supplies. As the key element of reliability in LED lamps is temperature, a solution is proposed for driving LED lamps using voltage sources, such as photovoltaic system batteries, with a control architecture based on pulse width modulation signal that regulates the current applied according to the LED lamp temperature. A prototype of the LED lamp has been implemented and tested to show its good performance at different temperatures and at different battery voltages

Online Switching Time Monitoring of SiC Devices Using Intelligent Gate Driver for Converter Performance Improvement

Most intelligent gate drivers designed for new state of the art WBG devices typically only focus on protection and driving capabilities of the devices. This paper introduces an intelligent gate driver that incorporates online switching time monitoring of silicon carbide (SiC) devices. For this specific case study, three timing conditions (turn-off delay time, turn-off time, and voltage commutation time) of a SiC phase-leg are online monitored. This online monitoring system is achieved through transient detection circuits and a micro-controller. These timing conditions are then utilized to develop converter-level benefits for a voltage-source inverter application using SiC devices. Junction temperature monitoring is realized through turn-off delay time monitoring. Dead-time optimization is achieved with turn-off time monitoring. Dead-time compensation is obtained with turn-off time and voltage commutation time monitoring. The case study converter assembled for testing purposes is a half-bridge inverter using two SiC devices in a phase-leg configuration. All timing conditions are correctly monitored within reasonable difference of the actual condition time. The half-bridge inverter can operate at 600 V DC input and successfully obtain a junction temperature measurement through monitored turn-off delay time and the calibration curve. In addition, dead-time control is realized to reduce device power loss and improve AC output power quality. Furthermore, the proposed online time monitoring system is board-level integrated with the gate driver and suitable for the chip level integration, enabling this practical approach to be cost-effective for end users