scholarly journals Dimming Techniques Focusing on the Improvement in Luminous Efficiency for High-Brightness LEDs

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2163
Author(s):  
Kun-Che Ho ◽  
Shun-Chung Wang ◽  
Yi-Hua Liu
Keyword(s):  
Output Power ◽  
Characteristic Curve ◽  
Flux Ratio ◽  
Digital Signal ◽  
Luminous Efficiency ◽  
Average Output ◽  
Theoretical Derivation ◽  
High Brightness ◽  
Power Curves ◽  
Pwm Dimming

The pulse width modulation (PWM) dimming mode features good dimming linearity and has been widely used for driving high-brightness light-emitting diodes (HBLEDs), in which the brightness change is reached by modulating the duty cycle of the dimming signal to regulate the average current flowing through LEDs. However, the current-illuminance characteristic curve of most LEDs is nonlinear in nature. Namely, under the same lighting power fed, the conventional PWM dimming cannot make the LED exert its best luminous efficiency (LE) specified in datasheets. This paper focuses on the study of further improving LED luminous efficacy via dimming manipulation. Thereby, two multilevel current dimming techniques with varied dimming signal voltage and varied current sensing resistance are presented. With limited dimming capability, the proposed dimming strategies can efficiently raise the luminous flux ratio without increasing the power consumption. A prototype constructed for a 115 W HBLED driver is developed and the devised dimming schemes are realized by a digital signal controller (DSC). Experimental results exhibited with illuminance-power curves and CIE1931 and CIE1976 chromaticity diagrams are given to validate the theoretical derivation and effectiveness. Compared with conventional PWM dimming, under the same illuminance, the driver average output power is respectively reduced by 17.08% and 13.17%; the improvement in average illuminance under the same output power is 13.66% and 11.17%, respectively. In addition, the entire average LE boost has respectively increased by 21.36% and 16.37%.

scholarly journals Continuous-Wave and Passively Q-Switched Er:Y2O3 Ceramic Laser at 2.7 μm

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Zhipeng Qin ◽  
Guoqiang Xie ◽  
Jian Zhang ◽  
Jingui Ma ◽  
Peng Yuan ◽  
...  
Keyword(s):  
Output Power ◽  
Continuous Wave ◽  
Maximum Output Power ◽  
Maximum Output ◽  
Average Output ◽  
Semiconductor Saturable Absorber ◽  
Infrared Spectral ◽  
Maximum Average Output Power ◽  
Ceramic Laser ◽  
Stable Passive

We report on a continuous-wave (CW) and passively Q-switched Er:Y2O3 ceramic laser in mid-infrared spectral region. In the CW regime, a maximum output power of 2.07 W is achieved at 2717.3 nm with a slope efficiency of 13.5%. Stable passive Q-switching of the Er:Y2O3 ceramic laser is demonstrated based on semiconductor saturable absorber mirror. Under an absorbed pump power of 12.4 W, a maximum average output power of 223 mW is generated with a pulse energy of 1.7 μJ and a pulse width of 350 ns at 2709.3 nm.

scholarly journals Pengaruh Algoritma Peturb & Observe pada Irradiance, Suhu dan Beban Bervariasi

AVITEC ◽  
2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Ernando Rizki Dalimunthe
Keyword(s):  
Output Power ◽  
Maximum Output Power ◽  
Maximum Power ◽  
Maximum Output ◽  
Average Output ◽  
Point Tracking ◽  
Power Simulation ◽  
Power Point Tracking ◽  
Duty Cycles ◽  
Power Point

Optimizing the output power value of a solar cell requires a tracker. The tracking is called the maximum power point tracking (MPPT) which will produce a maximum output power value. Each component in this system is modeled into Simulink. This simulation is designed to optimize the work of solar cells by searching maximum power points using perturb and observe (P & O) algorithms, then duty cycles are output  of the algorithms become Buck-Boost Converter inputs as switching so they can produce output power with better output  power. Simulation results show that MPPT can increase the average output power on changes in the value of sun irradiation, temperature and load than systems that do not use MPPT. The factor of the average difference in power is 37.82%.

Copper laser with high-average-output power

1995 ◽  
Author(s):  
Nikola V. Sabotinov ◽  
Chris E. Little
Keyword(s):  
Output Power ◽  
Average Output Power ◽  
Average Output

Diode-pumped passively mode-locked Nd:KGd(WO_4)_2 laser with 1-W average output power

2002 ◽  
Vol 27 (16) ◽  
pp. 1478 ◽  
Author(s):  
A. Major ◽  
N. Langford ◽  
T. Graf ◽  
D. Burns ◽  
A. I. Ferguson
Keyword(s):  
Output Power ◽  
Average Output Power ◽  
Average Output ◽  
Diode Pumped

SM green fiber laser operating in CW and QCW regimes and producing over 550W of average output power

2014 ◽  
Author(s):  
Valentin Gapontsev ◽  
Alexey Avdokhin ◽  
Pankaj Kadwani ◽  
Igor Samartsev ◽  
Nikolai Platonov ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Output Power ◽  
Average Output Power ◽  
Average Output

scholarly journals High-brightness lasing at submicrometer enabled by droop-free fin light-emitting diodes (LEDs)

2020 ◽  
Vol 6 (33) ◽  
pp. eaba4346
Author(s):  
Babak Nikoobakht ◽  
Robin P. Hansen ◽  
Yuqin Zong ◽  
Amit Agrawal ◽  
Michael Shur ◽  
...  
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Extraction Efficiency ◽  
Electrical Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Recombination Processes ◽  
Current Densities ◽  
New Generation

“Efficiency droop,” i.e., a decline in brightness of light-emitting diodes (LEDs) at high electrical currents, limits the performance of all commercial LEDs and has limited the output power of submicrometer LEDs and lasers to nanowatts. We present a fin p-n junction LED pixel that eliminates efficiency droop, allowing LED brightness to increase linearly with current. With record current densities of 1000 kA/cm2, the LEDs transition to lasing, with brightness over 20 μW. Despite a light extraction efficiency of only 15%, these devices exceed the output power of any previous electrically driven submicrometer LED or laser pixel by 100 to 1000 times while showing comparable external quantum efficiencies. Modeling suggests that spreading of the electron-hole recombination region in fin LEDs at high injection levels suppresses the nonradiative Auger recombination processes. Further refinement of this design is expected to enable a new generation of high-brightness LED and laser pixels for macro- and microscale applications.

scholarly journals Effect of dust deposition on the performance of photovoltaic modules in Taxila, Pakistan

2017 ◽  
Vol 21 (2) ◽  
pp. 915-923 ◽  
Author(s):  
Hafiz Ali ◽  
Muhammad Zafar ◽  
Muhammad Bashir ◽  
Muhammad Nasir ◽  
Muzaffar Ali ◽  
...  
Keyword(s):  
Output Power ◽  
Photovoltaic Module ◽  
Strong Impact ◽  
Dust Deposition ◽  
Average Output ◽  
Photovoltaic Modules ◽  
Time Period ◽  
Different Types ◽  
The Difference ◽  
Module Efficiency

The air borne dust deposited on the surface of photovoltaic module influence the transmittance of solar radiations from the photovoltaic modules glazing surface. This experimental work aimed to investigate the effect of dust deposited on the surface of two different types of photovoltaic modules (monocrystalline silicon and polycrystalline silicon). Two modules of each type were used and one module from each pair was left exposed to natural atmosphere for three months of winter in Taxila, Pakistan. Systematic series of measurements were conducted for the time period of three months corresponding to the different dust densities. The difference between the output parameters of clean and dirty modules provided the information of percentage loss at different dust densities. The dust density deposited on the modules surface was 0.9867 mg/cm2 at the end of the study. The results showed that dust deposition has strong impact on the performance of photovoltaic modules. The monocrystalline and polycrystalline modules showed about 20% and 16% decrease of average output power, respectively, compared to the clean modules of same type. It was found that the reduction of module efficiency (?clean ? ?dirtv) in case of monocrystalline and polycrystalline module was 3.55% and 3.01%, respectively. Moreover the loss of output power and module efficiency in monocrystalline module was more compared to the polycrystalline module.

Linearly polarized Q-switched pulse Yb fiber laser with average output power over 10 W

2009 ◽  
Vol 6 (6) ◽  
pp. 461-464 ◽  
Author(s):  
Y.X. Wang ◽  
D.Z. Yang ◽  
P.P. Jiang ◽  
Y.H. Shen
Keyword(s):  
Fiber Laser ◽  
Output Power ◽  
Average Output Power ◽  
Average Output ◽  
Linearly Polarized
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