A Study on the Working Performance of Dimming Methods for Single- and Multichip Power LEDs

Abstract

Light emitting diodes (LEDs) have many positive features, such as long life, low power consumption, and high luminous efficacy. Consequently, they are very attractive for use in many applications. Also, the use of LEDs ensures energy savings. Power LEDs have increasingly been used for general lighting via multichip module technology. The output of power LEDs should be controlled to obtain life and illuminance values in catalog. In this study, the effects of different dimming methods are investigated for single-and multichip LEDs. To achieve this aim, pulse width modulation (PWM) and current variation (CV) dimming methods are applied to single and multichip power LEDs during ten stages of dimming. A current-regulated DC source is used for current variation (CV) dimming, and a driver designed by the researcher is used for pulse width modulation (PWM) dimming. Moreover, all of the applications are made for active and passive cooling. Finally, the results are compared.

Power Quality and Harmonic Analysis of End User Devices

“…Current harmonics with significant amplitude can be found up to about the 10th harmonic.  cosφ 1 and PF are very close to the unit value, indicating that voltage and current first harmonics have a little phase shift and harmonics in current waveform do not have a strong impact on the quality in the energy conversion [19]. (a) (b)…”

“…Also in this case, voltage harmonics due to harmonic current absorption are negligible and the small value of THD V is related only to the harmonic pollution already existing into the grid [19].…”

“…In the present paper, three experimental studies are performed, investigating the power consumptions and harmonic absorptions of different types of indoor luminaries. The first experimental survey regards two indoor LED panels supplied by external DC switched power supply with dimming system [19]. The second experimental survey regards four LED spots with embedded electronic ballast.…”

Disturbances Generated by Lighting Systems with LED Lamps and the Reduction in Their Impacts

“…The use of such light sources is also economically advantageous-the long life means lower investment costs, and the low active power consumption translates into lower operational costs. Despite many advantages, the electroluminescent light sources have one major drawback-they cause strong distortions in the current [13][14][15][16][17][18][19][20][21][22][23][24].…”

“…If the number of LED lamps connected to electrical systems constitutes a significant part of all of the electrical light sources in a facility, then, because of the level of power consumed, problems with the impact of higher harmonics in such mains occur. In many scientific centres from all over the world, research related to the quality of the electricity in the power systems of LED lamps is conducted [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. At the same time, different solutions aimed at the improvement of the electricity quality parameters in these systems are proposed [33][34][35][36][37][38][39][40][41][42][43][44][45][46].…”