Article

Lumen Depreciation Diagnosis in Modulated LED Lighting Systems

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Lumen depreciation is the condition that the light output of a light emitting diode (LED) lamp falls below a fraction of its peak output. In LED lighting systems with multiple LED lamps, lumen depreciation leads to undesired distortions in the rendered illumination distribution. Automatic diagnosis of lumen depreciation in LED lighting systems is thus an important problem. We propose an approach to diagnose lumen depreciation in individual LEDs using photosensors by modulating the LED lamp output with a unique identifier and encoding average drive current within, and a carrier sense multiple access on the optical channel. At the photosensor, the received signal is processed in the electrical domain. The average drive current corresponding to an individual LED lamp is extracted and a residual is computed with respect to a nominal value. A threshold detector based on testing the mean change of the residual signal is used to diagnose lumen depreciation of the LED lamps.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Lumen depreciation leads to undesired distortions in the rendered illumination distribution. The author proposed an approach to diagnose lumen depreciation in individual LEDs using photosensors by modulating the LED lamp output with a unique identifier and encoding average drive current within, and a carrier sense multiple access on the optical channel [32]. ...
... A new ADC-free digital-control switch-mode LED driver with 1MHz switching frequency, featured by digital counters, a PWM generator, and current comparators is designed by Hyung-Do Yoonin 2014 [32]. Further energy consumption is reduced by controlling the LED lights based on user movement is proposed by Sunghoi Park and resulted in 19.2% power saving [35].A buck converter is implemented for LED driver by J. Wang for power factor correction, reducing switching losses, long life & high efficiency and added quasi resonant switch with the said topology [35].Qian Wang found that conventional DC-mode technique produces flicker-free light and high luminous efficacy but poor dimming function, whereas pulse-width-modulation technique offers better dimming flexibility but inherent flicker in comparison to DC technique. ...
Conference Paper
Full-text available
This paper presents a review on existing LED driving technologies with reference to solid state luminaries (SSL). Various performance parameters and current challenges are discussed through the study of recent literature. Due to some obvious features such as high luminous efficiency, low losses, long life, safety, environment friendly, less temperature effect ,higher operating voltage range and so on , the use of LEDs lamps with LED drivers (Ballast) are spreading all over the world with a very fast rate. The several technical issues in the design of suitable LED drivers are selection of topologies, power factor correction(PFC), lumen per watt efficiency & characteristics of LED as lamp , life of capacitors, dimming techniques, lumen depreciation, voltage & current regulation, effect of voltage sag, harmonics, size and compatibility are observed in the investigation carried out by various researchers. Hence through this paper, understanding of the subject will be helpful for future research in solid state luminaries (SSL).
... Lumen depreciation leads to undesired distortions in the rendered illumination distribution. The author proposed an approach to diagnose lumen depreciation in individual LEDs using photosensors by modulating the LED lamp output with a unique identifier and encoding average drive current within, and a carrier sense multiple access on the optical channel [32]. ...
... A new ADC-free digital-control switch-mode LED driver with 1MHz switching frequency, featured by digital counters, a PWM generator, and current comparators is designed by Hyung-Do Yoonin 2014 [32]. Further energy consumption is reduced by controlling the LED lights based on user movement is proposed by Sunghoi Park and resulted in 19.2% power saving [35].A buck converter is implemented for LED driver by J. Wang for power factor correction, reducing switching losses, long life & high efficiency and added quasi resonant switch with the said topology [35].Qian Wang found that conventional DC-mode technique produces flicker-free light and high luminous efficacy but poor dimming function, whereas pulse-width-modulation technique offers better dimming flexibility but inherent flicker in comparison to DC technique. ...
Article
Full-text available
This paper presents a review on existing LED driving technologies with reference to solid state luminaries (SSL). Various performance parameters and current challenges are discussed through the study of recent literature. Due to some obvious features such as high luminous efficiency, low losses, long life, safety, environment friendly, less temperature effect ,higher operating voltage range and so on , the use of LEDs lamps with LED drivers (Ballast) are spreading all over the world with a very fast rate. The several technical issues in the design of suitable LED drivers are selection of topologies, power factor correction(PFC), lumen per watt efficiency & characteristics of LED as lamp , life of capacitors, dimming techniques, lumen depreciation, voltage & current regulation, effect of voltage sag, harmonics, size and compatibility are observed in the investigation carried out by various researchers. Hence through this paper, understanding of the subject will be helpful for future research in solid state luminaries (SSL).
... Fault diagnosis and prognosis capabilities are usually implemented to increase safety and reliability of electric systems (e.g. transmission lines, converters, power circuits, etc . . . ) [13,14], however they are rarely integrated in lighting control systems, even if they are necessary to ensure energy savings [15][16][17], reliability of the system [18], and to maintain visual comfort even in case of LED failure. Following the trend of intelligent supervised systems, the developed control module operates in conjunction with a Fault Diagnosis and Prognosis module (FDP): ...
Article
Full-text available
The goal of this work is to develop a smart light-emitting diode lighting system for industrial and domestic use with several advantages over conventional systems, namely energy saving, high reliability, and visual comfort of interior lighting. This is achieved by integrating a smart control module and a fault diagnosis and prognosis module within a conventional lighting system. The first module controls the lighting level in an energy-efficient way, keeping a desired light level where it is needed while regulating it to a minimum where not required; this is achieved by fully exploiting fuzzy logic and proportional-integrative-derivative controllers. The second module performs fault diagnosis on the light-emitting diode system and predicts when light-emitting diode maintenance should be performed; this is achieved by employing both hardware redundancy and signal-based approaches. Interaction between the two modules permits maintenance of a desired level of light even in the case of failures on one or more light-emitting diodes. The overall system has been experimentally validated in three different scenarios.
... A very important challenge in complex systems (such as the developed lighting system) is to ensure that services are functional and available despite faults. Fault diagnosis and prognosis capabilities, however, are rarely integrated in lighting control systems, even if they are necessary to ensure the proper functioning and reliability of the system [9]. A Fault Diagnosis and Prognosis (FDP) supervision module has been developed to detect and isolate faults on the LED lamp. ...
Conference Paper
Full-text available
The goal of this work is the development of a LED driver system for industrial and domestic use, which integrates an AC-DC PFC interleaved boost converter, a resonant DC-DC LLC high efficiency converter, a low-level LED control and a fault detection component. Efficient energy use and harmonics reduction are the main goals to be achieved. AC-DC power stage has been designed to operate in interleaved mode and several control techniques have been tested to increase performances; a linear control has been implemented for the resonant converter; low-level LED control includes a fault detection capabilities. The approaches of simulation and rapid prototyping have been deeply exploited in this work to make faster design and test phases for each individual functional block and to minimize errors. The behaviour of the LED control component has been also compared with a real prototype.
Article
In order to help the engineers to improve quality level and reduce the failure rate in using of LED product, we should realize the failure mode, failure mechanisms and root causes of this kind of products. First, more than 300 failure analysis cases about LED product have been carried out by the authors. And the authors made a summary of these cases. The main failure modes of LED products are introduced. Then, based on these failure modes, the possible mechanism of each type of failure mode and the root causes of failures are analyzed in detail. Finally, a lot of cases are used to support the analysis in this article. All failure modes, corresponding failure mechanisms and root causes are summarized in a form for reference to engineers and technicians engaged in failure analysis and product improvement. The failure mode of LED products in the use is no light, or intermittently no light, or light intensity weakening, or device burnout. But its failure mechanism and related reasons are quite complex, such as the chip quality, packaging process, heat dissipation channel design and derating design related to LED.
Article
In this work, guidelines are provided for designing illumination-grade light-emitting diodes (LEDs) into luminaires. A generalized concept of deriving a multi-domain compact model of LED from data-sheet information is discussed, however, the process described can be applied to the design of any kind of LED luminaire. The most critical aspect of LED luminaire design is to decide on how many LEDs are required to meet the design goals. The rest of the design process revolves around the number of LEDs since it directly impacts the optical, electrical, and thermal aspects of a luminaire. The design process is not simple as it seems, it is not estimating the number of LEDs based on photometric characteristics listed on their datasheets and divides the target lumens from the design goals by that number. However, this approach looks too simple but not always will lead to a design that will meet the application’s illumination requirements. The photometric properties of a LED are dependent on a variety of factors, including drive current and junction temperature. The accurate number of LEDs can be estimated only when the inefficiencies of the optical, thermal and electrical systems are accounted for in the design process. This work serves as a guide to estimate some of the major losses.
Article
Full-text available
Lumen depreciation, the condition that the light output falls below a fraction of its peak output, is known to be the main failure mode in light emitting diodes (LEDs). In lighting systems comprising multiple LEDs, lumen depreciation leads to reduced average illuminance and a distorted illumination rendering. Diagnosing lumen depreciation in LED lighting systems is thus an important problem. We propose an estimation approach to diagnosing individual LED failures using a photosensor system. We specifically study the impact of perturbations in the photosensor positions on diagnosability by analyzing the sensor output matrix-the matrix relating the luminous flux values of the multiple LEDs to the measurements at the photosensor system. The conditions on diagnosability are first derived in terms of bounds on the smallest singular value of the sensor output matrix. Subsequently, sufficient conditions are derived on the photosensor positions to ensure that individual LED lumen depreciations are diagnosable. Numerical results are provided to validate our analytical results.
Article
Full-text available
This paper describes a new design concept of automatically diagnosing and compensating LED degradations in distributed solid state lighting (SSL) systems. A failed LED may significantly reduce the overall illumination level, and destroy the uniform illumination distribution achieved by a nominal system. To our knowledge, an automatic scheme to compensate LED degradations has not yet been seen in the literature, which requires a diagnostic step followed by control reconfigurations. The main challenge in diagnosing LED degradations lies in the usually unsatisfactory observability in a distributed SSL system, because the LED light output is usually not individually measured. In this work, we tackle this difficulty by using pulse width modulated (PWM) drive currents with a unique fundamental frequency assigned to each LED. Signal processing methods are applied in estimating the individual illumination flux of each LED. Statistical tests are developed to diagnose the degradation of LEDs. Duty cycle of the drive current signal to each LED is re-optimized once a fault is detected, in order to compensate the destruction of the uniform illumination pattern by the failed LED.
Article
Visible light communication (VLC) uses solid-state lightings to transmit information; therefore, it is necessary that modulation schemes for VLC provide dimming control. In this letter, we propose a multiple pulse position modulation (MPPM) to offer both functions of modulating data-stream and control- ling the brightness at the same time. According to the dimming level, we control the number of pulses of MPPM in one symbol duration. We analyze communication performance in terms of the normalized power requirement and spectral efficiency. From our studies, we show that MPPM is superior to variable on-off keying (VOOK) and variable pulse position modulation (VPPM) proposed in the IEEE 802.15 VLC task group.
Article
White LEDs were invented the 1990's. Since then they have been extensively researched and applied in various ways. Compared with conventional lighting devices, the white LED has lower power consumption, lower voltage requirements, longer lifetime, smaller size, faster response, and cooler operation. The white LED will eventually replace incandescent or fluorescent lights in offices and homes. We have proposed an indoor visible light wireless communication system that utilizes multiple white LED lighting equipment. In this system, the equipment is used not only for illuminating rooms but also for an optical wireless communication system. The system has significantly higher power levels than infrared wireless communication systems, since it also functions as the main lighting equipment. One problem is we tend to install many lighting sources on a ceiling in order to illuminate the room as evenly as possible. While the number of sources permits site diversity transmission over LOS links, the optical path difference between the multiple sources triggers intersymbol interference (ISI), which significantly degrades system performance. This paper overcomes the ISI problem by proposing an adaptive equalization system. We elucidate the most effective training sequence interval for channel estimation in a mobile environment. And we show that the adaptive equalization system with the effectual interval alleviates the influence of shadowing.
Article
This paper considers frequency division multiplexing (FDM) based illumination sensing in light emitting diode (LED) lighting systems. The purpose of illumination sensing is to identify the illumination contributions of spatially distributed LEDs at a sensor location, within a limited response time. In the FDM scheme, LEDs render periodical illumination pulse trains at different frequencies with prescribed duty cycles. The problem of interest is to estimate the amplitudes of the individual illumination pulse trains. In our previous work, an estimation approach was proposed using the fundamental frequency component of the sensor signal. The number of LEDs that can be supported by this estimation approach is limited to around 100 LEDs at a response time of 0.1 s. For future LED lighting systems, however, it is desirable to support many more LEDs. To this end, in this paper, we seek to exploit multiple harmonics in the sensor signal. We first derive upper limits on the number of LEDs that can be supported in the presence of frequency offsets and noise. Thereafter, we propose a low complexity successive estimation approach that effectively exploits the multiple harmonics. It is shown that the number of the LEDs can be increased by a factor of at least five, compared to the estimation approach using only the fundamental frequency component, at the same estimation error.
Article
Spectrally efficient data transmission with white light-emitting diodes (LEDs) is a topic of increasing interest. In this letter, we report a visible light communication link operating at 200+ Mb/s net transmission rate (230 Mb/s gross) with a bit-error ratio for uncoded data below 10(-3). The link is based on a thin-film high-power phosphorescent white LED and offline signal processing of discrete multitone signals. Transmission at the brightness levels of about 1100 and 550 lx was investigated. Our results indicate that the achievable data rates are limited by detector noise.
White light wireless transmission at
  • J Vucic
  • C Kottke
  • S Nerreter
  • A Buttner
  • K.-D Langer
  • J W Walewski