High-power Arrays Research Articles

Research and Implementation of Miniaturized Underwater Wireless Optical Communication System Based on Field Programmable Gate Array and High-Power LED Array Light Source

Research and Implementation of Miniaturized Underwater Wireless Optical Communication System Based on Field Programmable Gate Array and High-Power LED Array Light Source

Design and Implementation of Automatic Cooling Case Based on High-Power and High-Density Power Supply Array

Multi-board electronic cases with high-density and power modules are widely used in industrial power supply management. Heat dissipation becomes an important factor in the design process in improving case performance and miniaturization requirements. The design of existing small electronic thermal methods ignores high-temperature and high-load environment tests without automation control. To solve these problems, a heat dissipation case is designed with a magnesium and aluminum alloy, for intelligent temperature control based on a high-power and high-density power supply array. Based on the extreme miniaturization design principle, a composite heat dissipation mode is adopted based on conduction and supplemented by forced air cooling. The results show that the heat dissipation design in this article can work normally in high-temperature and high-load environment tests. Finally, the existing cooling designs are compared and analyzed. The cooling performance parameters in this article are better than those in the existing case. It contributes to the thermal design of miniaturized electronic cases in power supply management.

High Voltage Solar Array Development for Space and Thruster-Plume Plasma Environments

High-power solar arrays are in development by the National Aeronautics and Space Administration (NASA) for near-term high-power solar electric propulsion (SEP) missions. These high-voltage (HV) solar arrays use deployable flexible blanket configurations and need to be able to operate in the plasma environment of high-power Hall thrusters operating at tens of kilowatts of power. Array voltages of 300–800 V are desired both to minimize the copper bus mass in the system and to potentially operate the SEP Hall thrusters directly at high specific impulse without an in- series power processing unit. Coupons with multiple strings of solar cells (SCs) have been tested to high positive and negative biases in a plasma environment representative of the edge of Hall thruster plumes. Proper encapsulation of the exposed metals and triple points is required to avoid excessive current collection and arc initiation. Fully encapsulated test coupons have been successfully been tested at highest anticipated thruster plume plasma densities at voltages from 600 to 1000 V, which enables both very high power arrays and direct drive configurations for SEP missions.

Research on the package structure of deep low-temperature and high-power resistor array

Research on the package structure of deep low-temperature and high-power resistor array

Fast Optical Investigation of Cardiac Electrophysiology by Parallel Detection in Multiwell Plates.

Current techniques for fast characterization of cardiac electrophysiology employ optical technologies to control and monitor action potential features of single cells or cellular monolayers placed in multiwell plates. High-speed investigation capacities are commonly achieved by serially analyzing well after well employing fully automated fluorescence microscopes. Here, we describe an alternative cost-effective optical approach (MULTIPLE) that exploits high-power LED arrays to globally illuminate a culture plate and an sCMOS sensor for parallel detection of the fluorescence coming from multiple wells. MULTIPLE combines optical detection of action potentials using a red-shifted voltage-sensitive fluorescent dye (di-4-ANBDQPQ) with optical stimulation, employing optogenetic actuators, to ensure excitation of cardiomyocytes at constant rates. MULTIPLE was first characterized in terms of interwell uniformity of the illumination intensity and optical detection performance. Then, it was applied for probing action potential features in HL-1 cells (i.e., mouse atrial myocyte-like cells) stably expressing the blue light-activatable cation channel CheRiff. Under proper stimulation conditions, we were able to accurately measure action potential dynamics across a 24-well plate with variability across the whole plate of the order of 10%. The capability of MULTIPLE to detect action potential changes across a 24-well plate was demonstrated employing the selective Kv11.1 channel blocker (E-4031), in a dose titration experiment. Finally, action potential recordings were performed in spontaneous beating human induced pluripotent stem cell derived cardiomyocytes following pharmacological manipulation of their beating frequency. We believe that the simplicity of the presented optical scheme represents a valid complement to sophisticated and expensive state-of-the-art optical systems for high-throughput cardiac electrophysiological investigations.

High-Power Closed-Loop SMPC-Based Photovoltaic System Characterization under Varying Ambient Conditions

Photovoltaic energy generation potential can be tapped with maximum efficacy by characterizing the source behaviour. Characterization refers to the systematic terminal measurement-based PV modeling which can further facilitate output prediction and fault detection. Most of the existing PV characterization methods fail for high-power PV array due to increased thermal losses in electronic components. Here, we propose a switched-mode power converter-based PV characterization setup which is designed with input filter to limit switching ripple entering into PV array under test, thereby enhancing system life and efficiency. The high resonant frequency input filter ensures its compactness with high-speed characterization capability. To further enhance the system performance, a closed-loop current control of the system is designed for high bandwidth and stable phase margins. Variation of the controller parameters under varying ambient conditions of 200–1000 W/m2 irradiation and 25–70 °C temperature is documented and an adaptive PI controller is proposed. Experimental and simulation results validate the high performance of the closed loop operation of the PV characterization at 1.2 kW range power level in real-time field conditions. Compared to the open loop operation, the closed-loop operation eliminates the waveform ringing by 100% during characterization.

High-resolution linearity measurements of photovoltaic devices using digital light processing projection

Although photovoltaic (PV) devices are rated at standard testing conditions (STCs), these STCs are rarely met, either outdoors, or when PV devices are used for indoor applications. Thus, it is beneficial to fully characterise the linearity of PV devices with respect to irradiance. Moreover, high accuracy linearity measurements are essential for reference cells (RCs), as they ensure the precision of the measured irradiance. This work presents a new technique for linearity measurements of PV devices based on digital light processing (DLP). The proposed system uses a digital micromirror device coupled with projection optics and a high-power LED array. By creating a series of patterns projected on the device under test with a specific number of bright and dark pixels, linearity measurements can be implemented through a spatial dithering process. Since the dithering process is mechanical, it is expected that any spectral variability effects for the different dithering levels or electrical non-linearities of the light source are avoided. The developed system can provide thousands of measurement points on the linearity curve of a device in seconds, which is impossible with any other currently established methods. Measurements of RCs with known linearity curves are acquired and are validated by conventional methods. Results demonstrate that the DLP method provides equal measurement accuracy compared to conventional systems, but at significantly higher resolution (points on the linearity curve) and order of magnitude higher measurement speed.

On-line state observation and fault diagnosis of high-power LED array dynamic light source based on dynamic kernel principal component analysis

大功率LED阵列动态光源工作过程中光电热参数具有不确定性和时变时滞非线性特点，利用动态核主元分析方法（DKPCA）对大功率LED阵列动态光源进行在线状态观测与故障诊断能有效地捕捉观测数据的非线性和相关性特征，根据历史数据的主元特征计算出的统计量阈值和在线数据的统计特征实现故障检测，利用重构贡献图法实现故障的分离。仿真实验表明，对大功率LED阵列动态光源典型的传感器和执行器故障进行有效监测和诊断相对于核主元分析方法对故障更为敏感，故障检测率最高提高了7.5%，误检率下降了4.2%。

Structural optimization and numerical thermal analysis of ultraviolet light-emitting diodes with high-power multi-chip arrays

In this paper, the finite element method and experiment were used to systematically study the influence of different factors on the heat dissipation of high-power ultraviolet light-emitting diode (UV LED) module, including chip spacing and structure, sub-mount, adhesive materials, the packaging area and void ratio of adhesive. The package structure was optimized by introducing Al barrier plate and changing the spacing between adjacent chips. Considering the balance of junction temperature and irradiance, the appropriate chip spacing (∼ 2.5 mm) should be chose. The simulations analysis demonstrated that both sub-mount and adhesive materials play an important role in the thermal performance of the UV LED module. The area ratio (∼0.9) between the adhesive area and the chip area can not only realize the excellent heat dissipation but also minimize the use of adhesive materials. During reflow soldering, the lager coalesced voids should be decreased as soon as possible, which have worse heat dissipation performance than the distributed voids. Furthermore, the reliability and validity of the numerical simulation were verified by the experiment data. The present conclusions provide significant insight on designing and optimizing high-power UV LED devices.

Fast beam steering with an optical phased array.

Optical phased arrays (OPAs) are devices that use the coherence of light to control the interference pattern in the far field, which enables them to steer a laser beam with no moving parts. As such, OPAs have potential applications in laser communications, target acquisition and tracking, metrology, and directed energy. In this Letter, we present a control architecture for an actively phase-locked OPA, capable of steering a laser beam at speeds limited by the actuation bandwidth of electro-optic modulators. The system achieved an output phase stability of λ/770 and steering speeds up to 1 MHz. The digital control architecture can be extended to GHz steering speeds, is readily scalable to hundreds of emitters, and is compatible with high-power arrays.

Towards Clinical Translation of LED-Based Photoacoustic Imaging: A Review.

Photoacoustic imaging, with the capability to provide simultaneous structural, functional, and molecular information, is one of the fastest growing biomedical imaging modalities of recent times. As a hybrid modality, it not only provides greater penetration depth than the purely optical imaging techniques, but also provides optical contrast of molecular components in the living tissue. Conventionally, photoacoustic imaging systems utilize bulky and expensive class IV lasers, which is one of the key factors hindering the clinical translation of this promising modality. Use of LEDs which are portable and affordable offers a unique opportunity to accelerate the clinical translation of photoacoustics. In this paper, we first review the development history of LED as an illumination source in biomedical photoacoustic imaging. Key developments in this area, from point-source measurements to development of high-power LED arrays, are briefly discussed. Finally, we thoroughly review multiple phantom, ex-vivo, animal in-vivo, human in-vivo, and clinical pilot studies and demonstrate the unprecedented preclinical and clinical potential of LED-based photoacoustic imaging.

High-power light-emitting diode array design and assembly for practical photodynamic therapy research.

.Significance: Commercial lasers, lamps, and light-emitting diode (LED) light sources have stimulated the clinical translation of photodynamic therapy (PDT). Yet, the continued exploration of new photosensitizers (PSs) for PDT often requires separate activation wavelengths for each agent being investigated. Customized light sources for such research frequently come at significant financial or technical cost, especially when compounded over many agents and wavelengths.Aim: LEDs offer potential as a cost-effective tool for new PS and multi-PS photodynamic research. A low-cost-per-wavelength tool leveraging high-power LEDs to facilitate efficient and versatile research is needed to further accelerate research in the field.Approach: We developed and validated a high-power LED array system for benchtop PDT with a modular design for efficient switching between wavelengths that overcome many challenges in light source design. We describe the assembly of a low-cost LED module plus the supporting infrastructure, software, and protocols to streamline typical in vitro PDT experimentation.Results: The LED array system is stable at intensities in excess of with 2.3% variation across the illumination field, competitive with other custom and commercial devices. To demonstrate efficacy and versatility, a primary ovarian cancer cell line was treated with two widely used PSs, aminolevulinic acid and verteporfin, using the LED modules at a clinically relevant light dose that induced over 90% cell death for each treatment.Conclusions: Our work provides the community with a tool for new PS and multi-PS benchtop photodynamic research that, unlike most commercial light sources, affords the user a low barrier to entry and low-cost-per-wavelength with the goal of illuminating new insights at the forefront of PDT.

High-brightness and high-speed vertical-cavity surface-emitting laser arrays

High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modern lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly desirable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle ( ∼ 14 ∘ at 1 / e 2 ) under maximum output power, and a fast rise time ( < 100 p s ). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength.

Engineered Stresses for a Functional Si Light Emitter at Bandgap: An Overview

Interfacing various materials results in stresses and strains that typically alter the properties of either or both interfaced surfaces. In this work, we focus on enhanced light emission properties at the bandgap for silicon interfaced with silica or layers of silica and silicon nitride. This discovery is corroborated by several evidences of engineered stresses and strains at the bulk or interface such as implantation and/or diffusion of dopants in silicon and rough silicon surfaces formed by wafer cutting or etching and patterning. Silicon light emitters are being eagerly sought, and upon achieving reasonable efficiencies, they may be at hand soon. The significant investment in Si-photonics by dominant semiconductor players implies that such devices will be welcomed particularly in applications such as optical emitters for next-generation integrated optical circuits and interconnects; all-Si transceivers and cross connects for integrated circuit chips; light-wave components and high-power discrete and array emitters. Engineered stresses and strains modulate the indirect Si bandgap, resulting in enhanced radiative electron–hole recombination, which competes more effectively with non-radiative recombination.

Investigation on the Mutual Coupling of High-Power Dual-Branch Helical Antennas

The mutual coupling in high-power dual-branch helical antennas (DBHAs) is investigated, with the purpose of improving the power capacity of high-power antenna arrays further. Unlike common measures, the maximum ${E}$ -field difference between a single antenna element and its array is proposed to evaluate the strength of mutual coupling. This measure is suitable for high-power antenna arrays and validated by comparing with other indexes, such as S-parameter, gain, and axial ratio. Because high-frequency current and the ${E}$ -field are closely related, the full-wave method is used to calculate the current amplitude distribution over a single helical antenna and the scattering ${E}$ -field of an antenna array. Since the antenna elements mutually coupled through the air, several approaches are discussed for suppressing the mutual coupling. It is verified that using cavity not only isolates the antenna elements well but it is also with high power capacity. The results indicate that each antenna element is able to handle high pulsed power. Besides, it could be seen that the decrease in mutual coupling is helpful for improving the power capacity.

Beam Steerable Array Antenna Based on Rectangular Waveguide for High-Power Microwave Applications

A high power, high gain, and beam-steerable array antenna for high-power microwave applications is presented in this paper, which is fed by rectangular waveguides. A C-shaped slot on the narrow wall of the rectangular waveguide is applied to couple energy from the waveguide to the helical unit, which is used to radiate circularly polarized microwave. 2-D beam scanning is achieved through fewer control units. Simulation results indicate that a 2-m-long linear array achieves a gain of 26.3 dB, an aperture efficiency of 90.43%, and a power-handling capacity of 96.5 MW. A prototype of 20 × 15 array shows the beam scanning range is about ±35° in both typical vertical planes, while the gain decreases by less than 2.0 dB.

Subarray Decomposition for Radiation Measurement of High-Power Excited Electrically Large Phased Arrays of Antennas in Regular Anechoic Chambers

This letter presents a practical measurement scheme to characterize the radiation of electrically large phased arrays of antennas with high-power excitations. In particular, the proposed scheme is applicable to conduct the measurement in an ordinary anechoic chamber with limited power supply to simulate the radiation scenario of realistic high-power phased array antennas. This scheme first decomposes the original large array into virtually overlapped subarrays whose radiation patterns are used to compose the original radiation pattern. In addition, the subarrays' radiation patterns may serve as field basis functions to synthesize a desired pattern anticipated in the original phased array of antennas for radiation calibration.

Deconvolution of spectral power distribution of high-power laser diode arrays.

A novel method is proposed to predict the spectral power distributions (SPDs) of individual emitters in a high-power laser diode (LD) array. The proposed method deconvolutes the SPD of an LD array by taking into account the thermal cross-talk effect as well as the current competition effect. A complete analytical expression to deconvolute the SPD of an LD array is described. The expression contains four key parameters that are to be measured experimentally: (1) the normalized SPD of the central emitter, (2) the temperature coefficient of wavelength, (3) the current competition constant, and (4) the maximum power of the center emitter. The method is implemented with a commercial water-cooled high-power LD array. The SPD of the LD array predicted from the SPDs of individual emitters are compared with the experimentally measured SPD of the LD array. The results show excellent agreement in both shape and magnitude, which corroborates the validity of the proposed method.

Experimental study of electroluminescence and temperature distribution in high-power AlGaInN LEDs & LED arrays

Comprehensive analysis of current spreading, temperature distribution, and near-field electroluminescence of high-power “face-up” AlInGaN LEDs and LED Arrays was performed by combination of different experimental methods. Measurement results of thermal impedance and temperature distribution (mapping) of powerful light-emitting diode assemblies are described. A thermal resistance characterization consists in investigations of transient processes of temperature-sensitive parameter under heating by step-form or harmonically pulse-width modulated direct current and analysis using a thermal equivalent circuit (the Cauer and Foster models). By the involved method, thermal resistances of internal elements of the LEDs are determined. At the same time high resolution mapping of EL and thermal radiation was obtained by optical microscope and infrared images technique. It has been established correlation of the thermal resistance with a change in the current distribution (current crowding) at high excitation levels.

High-Power Array Antenna Based on Phase-Adjustable Array Element for Wireless Power Transmission

Based on a polarization twist reflector, a novel single-fed high-power and phase-adjustable array element is presented. Without a complicated feeding network, the element is simply excited by a balanced-fed dipole. By rotating the polarization of the driven dipole, the element can provide a continuous and linear phase in the far-field region. With the phase-adjustable property, the element can be a substitute for a digital phase shifter. In addition, field distributions of the element are analyzed through simulation, which prove its advantage of high power-handling capacity. The proposed element is also used to form an 8 × 8 array antenna. Compared to the array with conventional phase shifters, this array not only can achieve a high-accuracy beam control within a small scanning angle, but also can handle high power. The array element and array prototypes are designed, simulated, and measured. The results reveal that the element has an aperture efficiency of 97.7% and a linear phase change from 0° to 53.5° at 5.8 GHz. Additionally, the 8 × 8 array with an unequal power divider can obtain a sidelobe level of -20.2 dB, and its measured maximum gain and aperture efficiency are 27.7 dBi and 85.6%, respectively.