Pascal Dupuis

Simplified models of LED ballasts for spice

This paper addresses the problematic of usage of electronic ballasts in modern LED lighting equipment. A sample of eleven LED lamps available on the market is analyzed in temporal and frequency based analysis. The topology of the ballasts is determined and modeled using Spice software in a simplified manner. Results of the simulations are verified. Pairs of the lamp models are simulated and compared to original waveforms.

Study of High-Brightness LED Samples Aged Under Stress Temperature Conditions: Electrical Characterizations and Signature Evolution Analysis

LED devices used in lighting or backlighting applications are expected to be stable with a long life time. Manufacturers are thus interested in early detection of well-know degradation mechanisms and relationship between electrical signature evolutions and aging in order to predict the end of life of LED devices. This report presents electrical analysis results of four kind of high power LEDs through accelerated aging under temperature stress conditions. The first part of this paper describes the device, the aging protocol used, and the thermal measurements performed to improve and/or quantify the homogeneity. In the second part, I-V and C-V electric characterizations are described using methods to avoid capacitance or temperature warm-ups artifacts. Aging signature of Nichia and thermal influence on I-V measurements of Bridgelux BXRA-W3500 are presented.

Retrofit LED lamps: Photometric flicker analysis

The paper exposes the topic of LED lamps photometric flicker. Aim of the paper is to evaluate the flicker of contemporary devices. A sample of commercially available LED retrofit lamps is analysed in terms of the photometric flicker under ideal sinusoidal power supply conditions. Therefore the flicker described here is not a power quality issue, but a characteristic of the analysed lamps. The flicker level is compared to an incandescent lamp. As shown in the paper, some of the LED lamps show very high flicker level.

LED lighting — Reduce the power consumption and increase the users comfort

With the vanishing of the fossil primary resources and the carbon impact issues, the efficient use of energy has become a major priority. Lighting is an important element of expenditure as it is easy to act on it. The Light Emitting Diode (LED) technology opens many perspectives in this field due to its higher energy efficiency. LED could indeed become in a near future a replacement for fluorescent tubes. LEDs tubes have specific thermal and electrical needs; this work is focused therefore on optimization studies in terms of association topologies: serial versus parallel. The starting point is electrical equivalent models extracted from single LED. The choice of combinations is guided by the required performance in terms of light quality by paying attention to the overall consumption of the lighting system. The final target is the evaluation of losses reduction when the individual AC/DC conversion circuits integrated in the lamp bases are replaced by a DC/DC global distribution scheme. This approach was adopted to power the lighting of single room from a low DC voltage weakly regulated power grid.

Power quality of energy saving lamps under wide voltage variations

PLN, State-owned Electricity Company in Indonesia has been promoting energy saving lamps (ESLs) through demand-side management (DSM) program since 2005. As a result, those lamps are widely used in Indonesia. To avoid outages on the customers, a brownout strategy (voltage reduction) is sometimes used. The lamps are in this case operated at a lower voltage than their rating. The paper aims to investigate the effect on power quality of those voltage variations through a laboratory test. Value of harmonics, power factor and waveform of ESLs were analyzed. The test relates to 16 sample lamps commonly used in residential and commercial area, divided in 11 LED lamps and 5 CFLs covering different manufacturers and different power ratings. The experiment uses power meter to obtain the electrical characteristics. The supply voltage applied during testing was generated by an ideal power source without voltage harmonics to avoid effects linked to device non-linear behavior. The test results show that 4 types of LEDs and 2 types of CFLs can be identified based upon the input current waveform. However, their responses under voltage amplitude variation differ. This paper focuses on this specific electrical property, which is not readily documented. It was observed that only a few ESLs have low level of harmonic currents and high power factor, in concordance with low sensitivity to amplitude variations. Moreover, the experimental results are compared with the standard harmonic limit allowable for lighting load as per IEC 61000-3-2.

Acoustic resonance detection using statistical methods of voltage envelope characterization in metal halide lamps

Acoustic resonance (AR) phenomenon occurs in metal halide lamps and can cause light flicker, lamp arc bending and rotation, lamp extinction, and in the worst case, arc tube explosion. This study takes place in the context of developing electronic ballasts with robust AR detection and avoidance mechanisms. To this end, a lock-in amplifier is used to measure and characterize lamp voltage root mean square (rms) short-term fluctuations. Statistical criteria based on the standard deviation of this rms value are proposed to assess AR presence and classify its severity. A set of metal halide lamps from different manufacturers and with different powers were tested. The average electrical power and AR level are controlled by adjusting the lamp operating frequency of high-frequency electronic ballast. The proposed criteria enable classifying healthy (without AR) and faulty (with AR) cases based upon either a two-dimensional plane or a boxplot. Regardless of lamp operating power, the results from this study show that the voltage rms variations and the defined criteria are significantly correlated with AR level.

Performance of energy saving lamps on power quality and luminous properties under voltage decreasing 240V–100V

As state-owned electricity company in Indonesia, PLN still has lack of capacity and long distribution network in several regions so that under nominal voltage still happens in those regions. Sometimes, a brownout strategy is still done to avoid outage, unfortunately it makes the voltage in area supplied by long network become worse in peak load. Lamps will operate at a lower voltage than their rating. Nowadays, energy saving lamps (ESLs) are widely used by customers in Indonesia. To investigate the effect of voltage decreasing on power quality and luminous properties, laboratory observations will be performed. Sixteen sample lamps consist of 5 CFLs lamps and 11 LEDs with different manufacturers and power ratings will be tested. The results of tests indicate that only a few of ESLs meet IEC 61000-3-2 requirements.

On correct evaluation techniques of brightness enhancement effect measurement data

Abstract. This paper aims to establish confidence intervals of the quantification of brightness enhancement effects resulting from the use of pulsing bright light. It is found that the methods used so far may yield significant bias in the published results, overestimating or underestimating the enhancement effect. The authors propose to use a linear algebra method called the total least squares. Upon an example dataset, it is shown that this method does not yield biased results. The statistical significance of the results is also computed. It is concluded over an observation set that the currently used linear algebra methods present many patterns of noise sensitivity. Changing algorithm details leads to inconsistent results. It is thus recommended to use the method with the lowest noise sensitivity. Moreover, it is shown that this method also permits one to obtain an estimate of the confidence interval. This paper neither aims to publish results about a particular experiment nor to draw any particular conclusion about existence or nonexistence of the brightness enhancement effect.

Performance changes of energy saving lamps under lumen maintenance and switching stress test

White LED lamp are gaining a lot of popularity both on the residential and street lighting markets. Those devices are advertised with a very long lifetime compared to conventional incandescent lamps. A measurement campaign including accelerated ageing and stress test is ongoing in Sweden; parts of the data are joined to data obtained in France. The aim of this paper is to report and analyze which factors can be correlated to LED performance changes. A few commercial lamps were bought anonymously in retail stores; each type comprised 12 samples. A first group undergo long-term lumen maintenance test; the second was stressed by frequent switching (50 000 cycles, 30 seconds on/30 second off); the third and the fourth by frequent cycling (3 000 cycles, 30 minutes on/30 minutes off) at 25 °C and 75°C respectively. The assesment are made based on the change of the lumen, lamp efficiency, Correlated Color Temperature and Color Rendering index of the produced light before and after the test.

Ageing characterization of colorimetric and photometric properties of commercial LED lamps

This paper analyzes the changes of spectral-derived characteristics of LED lamps during their operational life. The analysis is based upon a laboratory-controlled ageing experiment over 17 LED lamps samples. Each sample is put into its normal operating condition up to 20000 hours. As a comparison, lumen maintenance tests are also performed over another set of 9 lamps. In order to analyze the change in characteristics, the photometric and color quantities of the lamps are evaluated. The results show that the blue peak value and the re-emitted yellow component are decreasing independently over time. This implies that the ageing process induces a change of the color temperature and of the color rendering index of the output light. Four mathematical models are also proposed to investigate the relationship between color output and the operational time of the lamp. The selection of the best fitting is based upon the coefficients of determination from each model.