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[IEEE 2019 IEEE 62nd International Midwest Symposium on Circuits and Systems (MWSCAS) - Dallas, TX, USA (2019.8.4-2019.8.7)] 2019 IEEE 62nd International Midwest Symposium on Circuits and Systems (MWSCAS) - Multi-Channel LED Driver with Accurate Current Matching for Portable Applications
摘要： In this paper, we present a multi-string LED driver based on a current-limiting hysteretic boost converter, which is capable of driving ten LEDs in five parallel strings. An accurate current matching circuit with low voltage headroom requirement is implemented to match currents in all LED strings. Dynamic compensation of the LED forward voltage mismatch between the strings is achieved with the introduction of a minimum voltage selector block. A PFM dimming circuit is designed to operate with a 200 kHz clock and has 11 programmable dimming ratios, ranging from 2:1 to 2048:1. This LED driver is implemented in 0.6-μm CMOS process and operates from a Li-ion battery with a voltage range 3 – 4.2 V. It is suitable for backlight LED displays in mobile devices.
关键词： dimming,hysteretic controller,DCM,current matching,LED driver,forward voltage mismatch
更新于2025-09-12 10:27:22
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High-Voltage AlInGaN LED Chips
摘要： A high-voltage light-emitting diode (LED) flip chip based on an AlInGaN heterostructure is developed and fabricated. The LED flip chip consists of 16 elements connected in series, each of which is a conventional LED. The chip with a total area of 1.25 × 1.25 mm is intended for a working current of 20 mA and a forward voltage of 48 V. To improve the current-distribution uniformity over the active region of the chip elements and to minimize the losses of the element area occupied by the n-type contact, the n-type contact pads in them are arranged inside the p-type contact region due to the two-level metallization layout with an intermediate insulating layer of dielectric. The arrangement topology of the contact pads is developed using numerical simulation. An increase in the quantum efficiency of the chip is provided by the application of combinations of metals with a high reflectance at the LED emission wavelength, which are used when fabricating n- and p-type contacts as well as current-carrying strips.
关键词： light-emitting diode,flip-chip design,LED chip,gallium nitride,high-voltage chip
更新于2025-09-12 10:27:22
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A Heat Pipe Cooler for High Power LED’s Cooling in Harsh Conditions
摘要： The paper presents an innovative method for High Power LEDs cooling in harsh conditions. To take full advantage of the benefits of LEDs, proper thermal management must be realized. This paper describes the limits of the cooling solution based on heat pipe, to maintain the junction temperature close to the nominal value, to avoid the color shift, recoverable light output reduction, voltage decreases. The most important, the reliability of any LED is a direct function of junction temperature, knowing that the higher the junction temperature, the shorter the lifetime of the LED.
关键词： LED Cooling,Energy Efficiency.,Heat-Trap,Heat Pipe
更新于2025-09-12 10:27:22
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Output current ripple reduction of LED driver using ceramic‐capacitor‐input circuit and buck‐boost converter
摘要： This article proposes an LED driver that consists of a ceramic-capacitor-input rectifier and a buck-boost converter. The LED driver has an advantage of long life because it does not contain any electrolytic capacitors. However, the issue with electrolytic capacitor-less LED driver is that the ripple of the smoothed voltage becomes large due to insufficient capacitance of the smoothing capacitor. The proposed method, which uses the discontinuous current mode of a buck-boost converter, reduces the output current ripple under such conditions. Experimental results using a 5.7 W LED driver prototype demonstrate that the proposed method reduces the output current ripple and that the percent flicker becomes 4.4%, which is smaller than the recommended upper limit of 8%.
关键词： ceramic capacitor,LED driver,buck-boost converter,electrolytic capacitor-less,discontinuous current mode
更新于2025-09-12 10:27:22
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Near infrared radiation shielding using CsxWO3 Nanoparticles for infrared mini Light-Emitting Diodes
摘要： Recently, near infrared LEDs have been used in small electronic devices due to the trend of manufacturing compact systems. The intensity of near infrared (NIR) optical device needs to be moderated if the chip emits too much power. In tradition, color pigments are used as additives in the encapsulant of LEDs to reduce the intensity of over irradiated NIR, a strategy which results in unaesthetic appearance. Cesium doped tungsten trioxide (CsxWO3) nanoparticles (NPs) have good near infrared absorption ability. Applying very few amount of CsxWO3 NPs into the encapsulation materials of NIR optical device can decrease NIR intensity while still maintain high visible light transmittance without losing aesthetic touch of those devices such as LED transmitters. The addition of only 0.0021 wt% CsxWO3/PMA dispersion in epoxy encapsulant can drop 15.5% NIR (860 nm) intensity but barely reduce visible light (only 3.2% at 450 nm). The excellent performance of CsxWO3 NPs; i.e., good NIR absorption and visible light transmission properties, can be suitable for maintaining the moderate luminescence intensity of small optoelectronic devices like NIR mini- or micro- light-emitting diodes.
关键词： nanoparticles,Mini-LED,Near-infrared shielding,nanocomposites,Cesium doped tungsten trioxide
更新于2025-09-12 10:27:22
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Effect of Different Bonding Materials on Flip-Chip LED Filament Properties
摘要： This article researches the effect of Sn-based solder alloys on flip-chip light-emitting diode LED (FC-LED) filament properties. SEM images, shearing force, steady-state voltage, blue light luminous flux, and junction temperature were examined to demonstrate the difference between two types of FC-LED filaments welded with two solders. The microstructure surface of Sn90Sb10 filament solder joints was smoother and had fewer voids and cracks compared with that of SAC0307 filament solder joints, which indicates that the Sn90Sb10 filaments had a higher shearing force than the SAC0307 filaments; moreover, the average shearing force was beyond 200 gf (standard shearing force). The steady-state voltage and junction temperature of the Sn90Sb10 solder-welded FC-LED filament were lower, and the Sn90Sb10 filament had a relatively higher blue light luminous flux. If high reliability of the solder joints and better photoelectric properties of the filaments are required, this Sn90Sb10 solder is the best bonding material for FC-LED filament welding.
关键词： reliability,lead-free solder,photoelectric properties,FC-LED filament
更新于2025-09-12 10:27:22
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[IEEE 2019 Joint International Symposium on Electromagnetic Compatibility, Sapporo and Asia-Pacific International Symposium on Electromagnetic Compatibility (EMC Sapporo/APEMC) - Sapporo, Japan (2019.6.3-2019.6.7)] 2019 Joint International Symposium on Electromagnetic Compatibility, Sapporo and Asia-Pacific International Symposium on Electromagnetic Compatibility (EMC Sapporo/APEMC) - Time and Frequency Domain Evaluation Method of Current Noise on the Power Line connected Multiple LED Bulbs
摘要： The electromagnetic noise generated from the inverter circuit in the LED lighting unit has become a problem influencing to the communication system. The purpose of this research is to examine the evaluation method under the condition of the multiple LED bulbs connected to power line. When the spike-shaped current waveforms generate by switching of inverter, the large amplitude noise at wide frequency band is observed. The current waveform converts to frequency spectrum by short time fast Fourier transform (STFT). Since the spike-shaped waveform diminishes over time, current noise amplitude at time zone during which noise is not generated is very small. The amplitude variation at the peak frequency is small. As the peak frequencies are estimated the power line resonance, current noise generated by spike-shaped noise does not decrease. On the other hand, at the 20 LED bulbs, the current waveform synthesized from each LED bulbs is non-periodic and non-uniform. The variation of amplitude is larger than that of one LED bulb due to distance between LISN to LED bulbs or individual specificity of each LED bulbs. The effective current variating to time is calculated. The maximum histogram at each frequency is coincided with effective current. These methods can be possible to evaluate the noise from the multiple LED bulb.
关键词： current noise,STFT,multiple LED bulbs,effective current
更新于2025-09-12 10:27:22
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A double-layer white light converter with high efficiency heat transfer structure for high-power NUV LEDs/LDs
摘要： As a next-generation lighting technology, high-power light-emitting diodes (LEDs) and lasing diodes (LDs) lighting have attracted great attention to high-brightness applications. However, producing an efficient illumination-grade color converter with a conspicuous color rendering index (CRI) and a suitable correlated color temperature (CCT) remains an outstanding challenge in the field of high-power LEDs/LDs lighting. In this work, a double-layer white light converter with high efficiency heat transfer structure was designed and prepared by precisely coating a blue/green emitting phosphor-in-silicone (PIS) film on red emitting transparent ceramic substrate. The well-designed double-layer converter exhibits excellent optical properties that the optical-optical conversion efficiency can achieve 156 lm/W with conspicuous CRI (92.6), CIE chromaticity coordinate (0.332, 0.335) and suitable CCT (5511K), respectively. Furthermore, the heat transfer efficiency of the double-layer converter was analyzed and simulated by using infrared thermal imaging and steady state thermal simulation, which reduce the temperature efficiently than single-layer converter under high-power NUV LEDs/LDs excitation. These comprehensive performance show that the double-layer converters are promising as NUV LEDs/LDs-driven phosphors in high-power solid-state lighting devices.
关键词： high-power LED/LD,transparent ceramic,white light converter,thermal performance,double-layer structure
更新于2025-09-12 10:27:22
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - 120m 10Mbps Ethernet Transmission Based on Visible Light Communication using a Single Commercially Available LED
摘要： In this paper, a VLC system is implemented,which combines with existing network (10Base-T). The transmitter uses a LED, and the receiver uses an APD. The system can realize real-time data transmission of 10Mbps Ethernet over 120m under strong background light.
关键词： LED,VLC,10Mbps Ethernet,Differential Manchester encoding,RJ-45
更新于2025-09-12 10:27:22
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A room-temperature polariton light-emitting diode based on monolayer WS2
摘要： Exciton polaritons that arise through the strong coupling of excitons and cavity photons are used to demonstrate a wide array of fundamental phenomena and potential applications that range from Bose–Einstein-like condensation to analogue Hamiltonian simulators and chip-scale interferometers. Recently, the two-dimensional (2D) transition metal dichalcogenides (TMDs), because of their large exciton binding energies, oscillator strength and valley degree of freedom, have emerged as a very attractive platform to realize exciton polaritons at elevated temperatures. Achieving the electrical injection of polaritons is attractive both as a precursor to realizing electrically driven polariton lasers as well as for high speed light-emitting diodes (LEDs) for communication systems. Here, we demonstrate an electrically driven polariton LED that operates at room temperature using monolayer tungsten disulfide (WS2) as the emissive material. The extracted external quantum efficiency is ~0.1% and is comparable to recent demonstrations of bulk organic and carbon nanotube-based polariton electroluminescence (EL) devices. The possibility to realize electrically driven polariton LEDs in atomically thin semiconductors at room temperature presents a promising step towards achieving an inversionless electrically driven laser in these systems as well as for ultrafast microcavity LEDs using van der Waals (vdW) materials.
关键词： room temperature,transition metal dichalcogenides,exciton polaritons,van der Waals materials,electrically driven polariton LED
更新于2025-09-12 10:27:22