Dimmable integrated CMOS LED driver based on a resonant DC/DC hybrid‐switched capacitor converter

This paper presents a 7.7 ‐ mm² on‐chip LED driver based on a DC/DC resonant hybrid‐switched capacitor converter operating in the MHz range with and without output capacitor. The converter operation allows continuously dimming the LED while keeping control on both peak and average current. Also, it features no flickering even in the absence of output capacitor and for light dimmed down to 10% of the nominal value. The capacitors and switches of the LED driver are integrated on a single IC die fabricated in a low‐cost 5 V 0.18‐μm bulk CMOS technology. This LED driver uses a small (0.7 mm²) inductor of 100 nH, which is 10 times smaller value than prior art integrated inductive LED drivers, still showing a competitive peak efficiency of 93% and achieving a power density of 0.26 W/mm² (0.34 W/mm³).     

A single‐stage high power‐factor bridgeless AC‐LED driver for lighting applications

An alternating‐current light‐emitting diode (AC‐LED) driver is implemented between the grid and lamp to eliminate the disadvantages of a directly grid‐tied AC‐LED lamp. In order to highlight the benefits of AC‐LED technology, a single‐stage converter with few components is adopted. A high power‐factor single‐stage bridgeless AC/AC converter is proposed with higher efficiency, greater power factor, less harmonics to pass IEC 61000‐3‐2 class C, and better regulation of output current. The brightness and flicker frequency issues caused by a low‐frequency sinusoidal input are surpassed by the implementation of a high‐frequency square‐wave output current. In addition, the characteristics of the proposed circuit are discussed and analyzed in order to design the AC‐LED driver. Finally, some simulation and experimental results are shown to verify this proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

高压大功率芯片封装的散热研究与仿真分析

以工作电压为70V、输出电流为9A的高压大功率芯片TO-3封装结构为例，首先基于热分析软件Flo THERM建立三维封装模型，并对该封装模型的热特性进行了仿真分析。其次，针对不同基板材料、不同封装外壳材料等情况开展对比分析研究。最后研究封装体的温度随粘结层厚度、功率以及基板厚度的变化，得到一个散热较优的封装方案。仿真验证结果表明，基板材料和封装外壳的热导率越高，其散热效果越好，随着粘结层厚度以及芯片功率的增加，芯片的温度逐渐升高，随着基板厚度的增加，芯片温度降低，当基板材料为铜、封装外壳为BeO，粘结层为AuSn20时，散热效果最佳。     

MEMS‐based Air Turbine with Radial‐inflow Type Journal Bearing

A microelectromechanical‐systems (MEMS)‐based air turbine with a new bearing system was designed, fabricated, and evaluated. The bearing system uses a radial‐inflow type journal bearing and a single‐sided hydroinertia thrust bearing. To fabricate the radial‐inflow type journal bearing, cavity‐through deep reactive ion etching (DRIE) in conjunction with silicon‐to‐silicon direct bonding was used. Two etched silicon substrates were directly bonded, and then the bonded silicon substrates were etched by DRIE through the inside cavities. A maximum rotation speed of 95 000 rpm was achieved. The measured and calculated frequency responses of the rotor‐bearing system suggest that the maximum rotation speed was probably limited by the pitching mode resonance. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Flip-chip packaging using micromachined conductive polymer bumpsand alignment pedestals for MOEMS

Using flip-chip bonding techniques with micromachined conductive polymer bumps and passive alignment techniques with electroplated side alignment pedestal bumps, a prototype microoptoelectromechanical systems (MOEMS) structure for optical input/output (I/O) couplers has been designed, fabricated and characterized. A top MOEMS substrate has through holes, contact metal pads, and side alignment pedestals with electroplated NiFe to align GaAs metal-semiconductor-metals (MSMs). Conductive polymer bumps have been formed on contact metal pads of GaAs MSMs using thick photoresist bump-holes as molding patterns. A diced GaAs photodetectors die with micromachined conductive polymer bumps was aligned to the side alignment pedestals and flip-chip bonded onto the substrate. This conductive polymer flip-chip bonding technique allowed a very low contact resistance (~10 mΩ), a lower bonding temperature (~170°C), and simple processing steps. The GaAs MSM photodetectors flip-chip mounted on the top of OE-MCM substrate showed a low dark current of about 10 nA and a high responsivity of 0.33 A/W     

A single‐stage LED streetlight driver with PFC and digital PWM dimming capability

This paper proposes a single‐stage light‐emitting diode (LED) driver that offers power‐factor correction and digital pulse–width modulation (PWM) dimming capability for streetlight applications. The presented LED streetlight driver integrates an alternating current–direct current (AC–DC) converter with coupled inductors and a half‐bridge‐type LLC DC–DC resonant converter into a single‐stage circuit topology. The sub‐circuit of the AC–DC converter with coupled inductors is designed to be operated in discontinuous‐conduction mode for achieving input‐current shaping. Zero‐voltage switching of two active power switches and zero‐current switching of two output‐rectifier diodes in the presented LED driver decrease the switching losses; thus, the circuit efficiency is increased. A prototype driver for powering a 144‐W‐rated LED streetlight module with input utility‐line voltages ranging from 100 to 120 V is implemented and tested. The proposed streetlight driver features cost‐effectiveness, high circuit efficiency, high power factor, low levels of input‐current harmonics, and a digital PWM dimming capability ranging from 20% to 100% output rated LED power, which is fulfilled by a micro‐controller. Satisfying experimental results, including dimming tests, verify the feasibility of the proposed LED streetlight driver. Copyright © 2016 John Wiley & Sons, Ltd.     

Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Au–Au‐bonding‐based wafer‐level vacuum packaging technology using in‐plane feedthrough of thick Au signal lines was developed for high‐frequency micro electromechanical system (RF MEMS). Compared with conventional technology based on glass frit bonding, the developed technology is advantageous in terms of smaller width of sealing frames, lower process temperature, and smaller amount of degas. To guarantee the hermetic sealing, the adhesion between the thick Au lines and a SiOx dielectric frame is improved by an Al₂O₃ interlayer by atomic layer deposition. The steps of the dielectric frame above the thick Au lines are absorbed by an electroplated Au seal ring planarized by fly cutting. The thermocompression bonding of the Au seal rings of 20‐100 μm width was done at 300 ºC. A cavity pressure of about 500 Pa or lower was measured by “zero balance method” using Si diaphragms. Vacuum sealing was maintained for more than 19 months, and the leak rate is less than 8×10‐16 Pa m3/s. The isolation of open signal lines was measured up to 10 GHz for different designs of the sealing ring and SiOx dielectric frame. The influence of the in‐plane feed through to the isolation is as low as 2‐3 dB, if the width of the sealing ring is 20 μm and the thickness of SiOx dielectric frame is larger than 10 μm. The developed wafer‐level packaging technology is ready for applications to an radio frequency (RF) MEMS switch.     

紫外LED与计量技术

紫外LED是一种新型的紫外辐射源,具有小巧便携、环保安全的特点。COVID-19疫情的出现加深了人们对深紫外LED杀菌消毒产品的认知。紫外LED与气体放电灯的光谱分布、照射距离、均匀性、功率水平等方面不同,基于传统紫外辐射源形成的计量测试方法,并不能直接套用于紫外LED的测量。本文介绍了现有紫外辐射测量仪器,分析了其用于紫外LED测量时影响测量结果不确定度的关键因素,给出了从仪器标定方法、标准器选择、积分球涂层选择和荧光评价等方面出发,提高测量结果准确度的方法,并对积分型紫外辐射照度计的改进方向提出了建议。     

AuSn20焊料制备技术及发展趋势

随着电子产品小型化、无铅化的发展,对焊接材料提出了更高的要求。无铅焊料AuSn20由于具有优良的性能,在高可靠性气密封装和芯片焊接中被广泛应用。本文介绍了AuSn20焊料的性能和制备方法,指出了传统的铸造拉拔轧制法、叠层冷轧复合法及电镀沉积法的不足,提出了研究及制备AuSn20合金焊料的技术改进方案。     

Near-Field Scanning Nanophotonic Microscopy—Breaking the Diffraction Limit Using Integrated Nano Light-Emitting Probe Tip

We introduce a novel scanning ldquonanophotonicrdquo microscope through monolithic integration of a nanoscale LED (Nano-LED) on a silicon cantilever. We review two recent trends of incorporating miniature light sources on the scanning probes for near-field scanning optical microscopy: one is to attach fluorephores at the tip to define a small light source, while the other is to integrate an LED and a nanometer aperture into scanning probes, based on silicon microfabrication techniques. The creation of Nano-LED combines the advantages of previous two approaches: no external sources are required and the reduction of the light source size directly leads to resolution improvement. Two types of Nano-LEDs have been successfully demonstrated utilizing nanofabrication and microelectromechanical systems technologies: 1) formation of thin silicon dioxide light-emitting layer between heavily doped p + and n+ silicon layers created by a focused ion beam and 2) electrostatic trapping and excitation of CdSe/ZnS core-shell nanoparticles in a nanogap. We employed these probes into a standard near-field scanning and excitation setup. The probe successfully measured optical as well as topographic images of chromium test patterns with imaging resolutions of 400 and 50 nm, respectively. In addition, the directional resolution dependence of the acquired images suggests the size and shape of the light source. To our knowledge, these results are probably the first successful near-field images directly measured by such tip-embedded light sources. With the potential emission capability from near UV to IR and additional mass producibility, the nanophotonic microscope presents exciting opportunities in near-field optics, integrated circuit technology, nanomanufacturing and molecular imaging, and sensing in biomedicine.     

Numerical Investigations of Smart Card Module: Parametric Analysis and Design Optimization

Ultrathin silicon chips are becoming more and more popular because of market demand for small, light, and high-performance products with noticeable request of reliability and flexibility. In this paper, the flexibility of the Integrated Circuit package is investigated using finite-element (FE) analysis. ANSYS software is used to analyze a single ultrathin die package in a smart card under four-point bending with the aim of developing flexible smart card modules using chips with thickness below 50 $muhbox{m}$. Thicknesses of different layers and Young's modulus of the die adhesive and the encapsulation resin are investigated to find their relative influence on the bending stress field in silicon. The thicknesses of some layers have important influence on bending stress distribution in the module. Decreased copper thickness can reduce considerably the maximal bending stress in silicon die under the same bending condition. As a result, some criteria for the design optimization are given in order to improve the flexibility of the package.      

Low‐temperature direct bonding of poly(methyl methacrylate) for polymer microchips

A low‐temperature, direct bonding method for poly(methyl methacrylate) (PMMA) plates has been developed by employing surface treatment by atmospheric pressure oxygen plasma, vacuum oxygen plasma, ultraviolet (UV)/ozone or vacuum ultraviolet (VUV)/ozone. Reasonable bonding strength, as evaluated by a tensile test, was achieved below the glass transition temperature (T_g). The highest bonding strength among the achieved results is 1.43 MPa (about three times the value for conventional direct bonding) at an annealing temperature of 50 °C and an applied pressure of 2.5 MPa for 10 min. Low‐temperature bonding prevents deformation of the PMMA microstructure. A prototype PMMA microchip that has fine channels of 5 µm depth was fabricated by hot‐embossing using a Si mold. After atmospheric pressure oxygen plasma activation, direct bonding was carried out at an annealing temperature of 75 °C and an applied pressure of 3 MPa for 3 min. The method gives good bonding characteristics without deformation and leakage. This low‐temperature bonding technology can be applied to polymer micro/nano structures. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

不同固晶材料对超高亮度LED性能的影响

固晶材料是超高亮度发光二极管(LED)封装过程中必备的关键材料之一,是决定LED性能,特别是寿命的重要因素。本文分别以银胶和绝缘胶为例,对比分析其对蓝、白光LED光学性能及光衰减过程的影响,在此基础上,提出一种评价和对比超高亮度LED性能优劣的算法,可以更可观准确地为LED封装设计和选材提供依据。     

Improved Output Power of 380 nm InGaN-Based LEDs Using a Heavily Mg-Doped GaN Insertion Layer Technique

High-performance InGaN-based 380 nm UV LEDs are fabricated by using a heavily Mg-doped GaN insertion layer (HD-IL) technique. Based on the transmission electron microscopy, etch pit density, and cathodoluminescence results, the HD-IL technique can substantially reduce the defect density of GaN layer. The double-crystal X-ray diffraction results are in good agreement with those observations. The internal quantum efficiency of LED sample with an HD-IL shows around 40% improvement compared with the LED sample without the use of HD-IL. When the vertical-type LED chips (size: 1 mm $times$ 1 mm) are driven by a 350 mA current, the output powers of the LEDs with and without an HD-IL are measured to be 203.4 and 158.9 mW, respectively. As much as 28% increased light output power is achieved.      

聚合物光纤传光束用白光LED光源

介绍一种新颖的白光LED聚光灯,用于聚合物光纤（POF）传光束,以得到高效率和均匀的功率耦合。采用一种椭球反射镜（反光杯）,将普通T1-3／4封装的φ5mm白光LED出射光线会聚到15°角以内,可满足POF传光束的数值孔径要求。理论和实验结果表明,该光源输出光强分布均匀。     

白光LED用几种Eu^2＋激活的红色荧光体的性能

本文对固态照明白光LED用Eu^2＋激活硫化钙、Eu^2＋激活的氮化物和氮氧化物三种高效红色荧光体的物理化学和发光特性进行对比和分析。氮（氧）化物红色荧光体的性能稳定。四种材料适合用作InGaN蓝光LED光转换红色荧光体,和YAG：Ce黄粉组合,使制作的白光LED的显色指数Ra大大提高,有利实现LED普通照明。     

Output characteristics model for an a‐Si ISFET pH sensor

A mathematical model for the calculation of the output characteristics of amorphous silicon hydrogenated (a‐Si:H) ion‐sensitive field‐effect transistors (ISFET) is developed, which depends on the integration of the conductivity channel versus gate voltage curve at fixed drain voltage. Single curve integration was changed to integration with many simple lines to obtain the I_D − V_D characteristics using computer programming. The results of this model were tested with those of experiments. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Output current ripple reduction of LED driver using ceramic‐capacitor‐input circuit and buck‐boost converter

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%.     

Dimmable MR16 LED drivers with low output ripple and wide duty ratio operating range

In this paper, a novel single‐switch DC–DC converter is proposed for dimmable MR16 light‐emitting diode (LED) drivers. The proposed driver can achieve very low output voltage ripple without using MHz switching frequency; therefore, small non‐electrolytic capacitors can be used to achieve longer lifetime and higher efficiency. Also, because of special merit of the proposed converter, it can be designed so that much wider duty ratio operating range can be achieved for LEDs. Hence, better digital dimming level resolution can be attained. Finally, a prototype driver for MR16 LED lamps is constructed to demonstrate the effectiveness of the converter. Experimental results show that a maximum efficiency of 92% can be achieved. Copyright © 2016 John Wiley & Sons, Ltd.     

Numerical modeling of a CMOS UV/blue photodetector based on MOSFET and lateral photosensitive diode

A complementary metal‐oxide semiconductor photodetector with ring‐shaped structure is presented in this paper, which consists of a p‐channel metal‐oxide‐semiconductor field‐effect transistor and lateral photodiodes and can be applied for ultraviolet (UV)/blue detection. The p‐channel metal‐oxide‐semiconductor is enclosed by ring‐shaped lateral photodiodes and lateral ring‐shaped photodiodes for enlarging near‐surface depletion region of the photodetector. Photoelectric conversion process of the photodetector has been modeled, and some performance parameters of photodetector have been derived and evaluated. The simulation results show that the photodetector can exhibit a high current responsivity of 1 × 10⁻³ Å even for ultra‐weak light such as 0.01 μW. The composite photodetector is fabricated in a standard 0.18 µm complementary metal‐oxide semiconductor technology. The test results reveal that the presented photodetector, which just like predicted by the model, is an effective way to solve the low response of silicon‐based UV detector. In a word, the presented photodetector has a big potential application value in weak light and UV/blue light detection. Copyright © 2015 John Wiley & Sons, Ltd.