一种基于MEMS技术的新型对称式微波功率传感器

A novel symmetrical microwave power sensor based on MEMS technology is presented. In this power sensor, the left section inputs the microwave power, while the fight section inputs the DC power. Because of its symmetrical structure, this power sensor provides more accurate microwave power measurement capability without mismatch uncertainty and temperature drift. The loss caused by the microwave signal is simulated in this power sensor. This power sensor is designed and fabricated using GaAs MMIC technology. And it is measured in the frequency range up to 20 GHz with an input power in the 0-80 mW range. Over the 80 mW dynamic range, the sensitivity can achieve about 0.2 mV/mW. The difference between the input power in the two sections is below 0.1% for an equal output voltage. In short, the key aspect of this power sensor is that the microwave power measurement is replaced with a DC power measurement.     

Optically Powered Pressure Sensor with Optical Fiber Link

An optically powered sensor for measuring pressure which is linked by optical fiber is developed in new scheme.Its pulse positio modulation(PPM)optical signal and op-tical supply power for electronics in probe are transmitted via a single optical fiber.The opti-cal power is carried by a 1300nm laser diode(LD)and the sensing data are carried by a 850nm LED.The remote ptobe uses all CMOS chips and particular modulations(PPM and PWM).Its electrical consumption including signal manipulation and LED driven current from optically converted is less than 100μW.The laser diode supplies 5mW optical power into fhe fiber.A Photodetector converts suffichently this power into electrical power to drive the whole probe operation.The optically powered distance gets up to 500m.The novel sen-sor combines optical fiber and electronies technology into a system.Because of using the prin-ciple of ratio measurement between measured and reference signals.as well as light feedback,the system is available with high reliab,outstanding accuracy and repeatability.     

基于门控多路环形振荡器的时间数据转换器

A gated ring oscillator(GRO) based time-to-digital converter(TDC) is presented.To enhance the resolution of the TDC,a multi-path structure for the GRO is used to achieve a higher oscillation frequency and an input stage is also presented to equivalently amplify the input time difference with a gain of 2.The GRO based TDC circuit is fabricated in TSMC 65 nm CMOS technology and the core area is about 0.02 mm~2.According to the measurement results,the effective resolution of this circuit is better than 4.22 ps under a 50 MHz clock frequency. With a 1 ns input range,the maximum clock frequency of this circuit is larger than 200 MHz.Under a 1 V power supply,with a 200-800 ps input time difference,the measured power consumption is 1.24 to 1.72 mW at 50 MHz clock frequency and 1.73 to 2.20 mW at 200 MHz clock frequency.     

Thermal analysis of LED lighting system with different fin heat sinks

This paper designs a 3 × 3 light emitting diode (LED) array with a total power of 9 W, presents a thermal analysis of plate fin, in-line and staggered pin fin heat sinks for a high power LED lighting system, and develops a 3D one-fourth finite element (FE) model to predict the system temperature distribution. Three kinds of heat sinks are compared under the same conditions. It is found that LED chip junction temperature is 48.978 ℃ when the fins of heat sink are aligned alternately.     

Thermal analysis of LED lighting system with different fin heat sinks

This paper designs a 3×3 light emitting diode(LED) array with a total power of 9 W,presents a thermal analysis of plate fin,in-line and staggered pin fin heat sinks for a high power LED lighting system,and develops a 3D one-fourth finite element(FE) model to predict the system temperature distribution.Three kinds of heat sinks are compared under the same conditions.It is found that LED chip junction temperature is 48.978℃when the fins of heat sink are aligned alternately.     

Sensitivity of MEMS microwave power sensor with the length of thermopile based on Fourier equivalent model

A Fourier equivalent model is introduced to research the thermal transfer behavior of a terminating-type MEMS microwave power sensor.The fabrication of this MEMS microwave power sensor is compatible with the GaAs MMIC process.Based on the Fourier equivalent model,the relationship between the sensitivity of a MEMS microwave power sensor and the length of thermopile is studied in particular.The power sensor is measured with an input power from 1 to 100 mW at 10 GHz,and the measurement results show that the power sensor has good input match characteristics and high linearity.The sensitivity calculated from a Fourier equivalent model is about 0.12,0.20 and 0.29 mV/mW with the length at 40,70 and 100μm,respectively,while the sensitivity of the measurement results is about 0.10,0.22 and 0.30 mV/mW,respectively,and the differences are below 0.02 mV/mW. The sensitivity expression based on the Fourier equivalent model is verified by the measurement results.     

终端式MEMS微波功率传感器的设计与制作

A terminating type MEMS microwave power sensor based on the Seebeck effect and compatible with the GaAs MMIC process is presented. An electrothermal model is introduced to simulate the heat transfer behavior and temperature distribution. The sensor measured the microwave power from –20 to 20 dBm up to 20 GHz. The sensitivity of the sensor is 0.27 mV/mW at 20 GHz, and the input return loss is less than –26 dB over the entire experiment frequency range. In order to improve the sensitivity, four different types of coplanar waveguide （CPW） were designed and the sensitivity was significantly increased by about a factor of 2.     

A New Low Voltage RF CMOS Mixer Design

A new architecture of CMOS low voltage downconversion mixer is presented.With 1.452GHz LO input and 1.45GHz RF input,simulation results show that the conversion gain is 15dB,IIP3 is －4.5dBm,NF is 17dB,the maximum transient power dissipation is 9.3mW，and DC power dissipation is 9.2mW.The mixer’s noise and linearity analyses are also presented.     

Compact yellow-orange Nd:YVO4/PPMgLN laser at 589 nm

We propose and make a compact yellow-orange laser of the Nd-doped yttrium vanadate (Nd:YVO4)/periodically poled Mg-doped lithium niobate (PPMgLN) module by Raman frequency-doubling at 589 nm. By reasonably designing the size of the Nd:YVO4 and 5 mol% PPMgLN crystals, cavity length and coating parameter, a compact 589 nm laser module with a total size of 3 mm×10 mm×1.5 mm is fabricated. In the laser module, the input surface of Nd:YVO4 crystal is end-pumped by an 808 nm laser diode (LD). Under the effect of linear resonant cavity structure, the output surface of PPMgLN crystal with a period of 9.48 μm generates 589 nm yellow-orange light. The experimental results show that the maximum output power at 589 nm is 390 mW at the pump power of 3 W with the optical-optical conversion efficiency of 13% and the stability of the output power is less than 2% within 3 h.     

一种采用分区RESURF技术并应用多金属环终端技术的新的电平位移结构

A new structure of a lateral n-MOST and a new level-shifting structure with multiply metal rings （MMRs） by divided RESURF technique have been proposed. The device and electrical performances of the structure are analyzed and simulated by MEDICI. In comparison to the level-shifting structure with multiply floating field plates （MFFPs） used before, the structure stated here improves the reliability and diminishes the voltage difference between the voltage of the power supply of the high-side gate driver and the voltage of the output terminal of the level-shifting structure, which is also that of the input terminal of the high-side gate driver. The maximal voltage difference of the level-shifting structure in this paper is 30% lower than that used before. Therefore, good voltage isolation and current isolation are obtained. The structure can be used in the level-shifting circuit of various applications.     

Thermal analysis of high power LED package with heat pipe heat sink

The goal of this study is to improve the thermal characteristics of high power LED (light-emitting diode) package using a flat heat pipe (FHP). The heat-release characteristics of high power LED package are analyzed and a novel flat heat pipe (FHP) cooling device for high power LED is developed. The thermal capabilities, including startup performance, temperature uniformity and thermal resistance of high power LED package with flat heat pipe heat sink have been investigated experimentally. The obtained results indicate that the junction temperature of LED is about 52 °C for the input power of 3 W, and correspondingly the total thermal resistance of LED system is 8.8 K/W. The impact of the different filling rates and inclination angles of the heat pipe to the heat transfer performance of the heat pipe should be evaluated before such a structure of heat pipe cooling system is used to cool high power LED system.     

Experimental study on high-power LEDs integrated with micro heat pipe

Micro heat pipe (MHP) is applied to implement the efficient heat transfer of light emitting diode (LED) device. The fabrication of MHP is based on micro-electro-mechanical-system (MEMS) technique, 15 micro grooves were etched on one side of silicon (Si) substrate, which was then packaged with aluminum heat sink to form an MHP. On the other side of Si substrate, three LED chips were fixed by die bonding. Then experiments were performed to study the thermal performance of this LED device. The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power, the optimum filling ratio changes from 30% to 48%, and the time reaching stable state is reduced; when the input power is equal to 2.5 W, only the LED device with filling ratio of 48% can work normally. So integrating MHP into high-power LED device can implement the effective control of junction temperature.     

一种高功率LED射灯的散热设计与实验研究

以一款MR16 LED射灯为模型,采用ANSYS有限元软件进行热分析。以散热器翅片保持60℃为标准,通过实验与仿真相结合的方法,分析了LED射灯的热流功率、散热器基座厚度、LED芯片间距、对流面积对整个系统散热性能的影响。结果表明,散热器对流面积是影响灯具散热性能的最重要因素;对一定的散热器,存在一个有效的最大芯片输入功率。现有MR16 LED射灯的散热器最大散热功率只能达到2.5 W左右,要使散热功率增大并且发挥散热器最佳性能,必须增加散热器的对流面积。对该结构散热器散热性能的定量研究对今后高功率LED灯具的生产具有一定的指导意义。     

应用于大功率LED器件的回路热管散热研究

为解决大功率LED的散热问题,提出一种应用于大功率LED散热的微型回路热管,研究了充液率和倾斜角度对热管冷却大功率LED的启动性能、结温和热阻等特性的影响.研究结果表明:热管的最佳充液率为60％,系统的总热阻为7.5 K/W,此时对应的热管的热阻为1.6 K/W;热管的启动时间约为6.5 min,LED的结点温度被控制在42℃以下,很好地满足了大功率LED的结温稳定性要求.     

基于LED的校园照明节能控制系统

设计了一套适用于高校校园的LED照明节能控制系统,包括LED恒流驱动电源、光照度检测模块、红外热释电传感模块、计数模块和GPRS无线通信模块等。配套了18 W T8型LED灯管和50 W面板型两种LED灯具,分别用于替换教室荧光灯和校园道路路灯。驱动电源通用性好,支持12 V和24 V两种直流输入电压,最大输出功率可达150 W,且输出电压自适应,使其能够兼容多种串并方式的LED灯具。该系统同样适用于博物馆、大型酒店、地下停车场等照明需求量大的应用场合。     

大功率LED照明装置微热管散热方案分析

设计了一种新型的带有百叶窗的平板式大功率发光二极管(LED)照明装置。该装置采用高导热系数的铝基板作为多颗大功率LED的散热电路板,用0.4mm的铝片作为散热翅片,结合沟槽式微热管构成集发光与散热一体化的输入功率为21W的照明模组,该模组可根据照明亮度要求重构成不同功率的照明装置。对功率为144W的照明装置进行了理论分析与实验研究。根据理论计算,每个照明模组的发热量约为18W,每个照明模组的传热量约为47W;模拟结果表明,在环境温度为30℃,自然对流换热系数为10W/(m2·K)时,LED芯片最高结温Ta=75℃,而实验测得Ta=75.7℃。     

Thermal characterization of multicolor LED luminaire

The LED based dynamic lighting scheme, require compact and thermally efficient luminaire. This paper presents the thermal investigation on the conceptual design of 36 W multicolor light emitting diode (LED) luminaire. The developed prototype design includes configuration and placement of the multichip LED package, RGBW and single die amber LEDs in a 5 × 3 array on the heat sink. LED configurations with low power input are placed between the LEDs having the high power input. The proposed configuration and placement of LEDs reduces the local heat concentration in the centre region of the heat sink. The temperature of 72 °C at LED chip base plate is reduced to 32.1 °C on the heat sink surface. The numerical results are experimentally validated. The proposed method contributes to a reduction in the size of the luminaire and also enhancement of heat dissipation for improving the longevity of the multicolor based LED luminaire.     

Thermal transient characteristics of die attach in high power LED PKG

The reliability of packaged electronics strongly depends on the die attach quality because any void or a small delamination may cause instant temperature increase in the die, leading sooner or later to failure in the operation. Die attach materials have a key role in the thermal management of high power LED packages by providing the low thermal resistance between the heat generating LED chips and the heat dissipating heat slug. In this paper, thermal transient characteristics of die attach in high power LED PKG have been studied based on the thermal transient analysis using the evaluation of the structure function of the heat flow path. With high power LED packages fabricated by die attach materials such as Ag paste, solder paste and Au/Sn eutectic bonding, we have demonstrated for characteristics such as cross-section analysis, shear test and visual inspection after shear test of die attach and how to detect die attach failures and to measure thermal resistance values of die attach in high power LED PKG. From the differential structure function of the thermal transient characteristics, we could know the result that die attach quality of Au/Sn eutectic bonding with the thermal resistance of about 3.5 K/W was much better than this of Ag paste and solder paste with the thermal resistance of about 11.5–14.2 K/W and 4.4–4.6 K/W, respectively. From this results, it is possible to fabricate high power LED with a small thermal resistance and a good die attach quality by applying Au/Sn eutectic bonding die attach with a high reliability and a good repeatability.     

Thermal characteristics and fabrication of silicon sub-mount based LED package

In this paper, the cost of a light emitting diode (LED) package is lowered by using a silicon substrate as the base attached to the chip, in contrast to the conventional chip-on-board (COB) package. In addition we proposed an LED package with a new structure to promote reliability and lifespan by maximizing heat dissipation from the chip. We designed an LED package combining the advantages of COB based on conventional metal printed circuit board (PCB) and the merits of a silicon sub-mount as a substrate. When an input current 500–1000 mA was applied, the fabricated LED exhibited the light output of approximately 112 lm/W at 29 W. We also measured and compared the thermal resistance of the sub-mount package and conventional COB package. The measured thermal resistance of the sub-mount package with a reflective film of Ag and the COB package were 0.625 K/W and 1.352 K/W, respectively.     

大功率照明白光LED恒流驱动芯片设计

基于0.6μm标准CMOS工艺,研究设计了一款大功率照明白光LED恒流驱动芯片,可为两路功率型LED分别提供恒定的350mA驱动电流。驱动电路的输出级大功率管采用蛇形栅结构的设计,在标准CMOS工艺线上实现了功率器件与控制电路的单片集成。采用单电源供电,最高输出功率可达3W以上;单电源电压在4～7V范围内,芯片能够实现良好的恒流驱动功能,驱动电流恒流失配度保持在3.09%以内;当标准5V电源有10%的变化时,驱动电流的变化可控制在1.42%之内,恒流失配度保持在2.84%以内;而当环境温度在10～90℃范围内变化,驱动电流最多增大1.75%,恒流失配度保持在3.15%以内。采用双电源供电时,芯片电源转换效率可达83%。