X射线管灯丝参数及其温度分布计算的研究

X射线管的焦点尺寸、功率和寿命是评价X射线管性能的主要技术指标,这些参数主要取决于灯丝的参数设计和工作时的温度分布。首先根据X射线管灯丝的典型电压、最大工作电流以及最大管电流的设计要求,利用灯丝热辐射表面积与热电子发射表面积相等的方法,推导了X射线管灯丝直径和长度参数的计算公式,同时可以获得灯丝的最高平均工作温度;再结合傅里叶导热微分方程,提出等间隔温度迭代的方法从灯丝两端开始计算温度,并引入螺旋遮挡系数δ进行修正,研究了灯丝在不同灯丝电压下的温度分布以及热电子发射分布。实验测量了X射线管在不同灯丝电压下的灯丝电流和管电流,用测量的灯丝电流计算灯丝温度分布,通过热电子发射电流公式转换为管电流,最后与实验测量的管电流值进行比较,结果表明两者变化趋势一致,最大误差小于±7.7%。     

大功率白光LED伏安特性和正向电压温度特性研究

在Ga N基大功率白光发光二极管(LED)老化过程中,有部分器件在小电流驱动下出现亮度不一致的现象,对其伏安特性和正向电压温度特性进行了研究。实验结果发现在小电流驱动下发光微弱的LED漏电流严重增大,在高温和大电流驱动的情况下LED正向电压随温度的变化偏离了线性关系,正向电压随温度的变化系数由负数变为正数。同时,通过对比实验表明这种器件出现的反常现象会伴随着寿命和可靠性问题。     

AV功放原理与维修讲座(6)——第六讲 荧光屏显示和驱动原理

<正> 真空荧光显示屏(称VFD)能显示外文、中文、图形(如商标),并在单片机CPU及驱动IC的共同控制下,可产生静止、闪动、移动等特技效果。它具有高亮度、宽视角、高对比度,宽温、色鲜、抗干扰等特点,已广泛应用于影碟机、功放机、组合音响、仪表等。 VFD由灯丝、栅极、阳极三个基本电极组成,其中灯丝极为热电子发射源,栅极用于加速和控制电子,阳极上的荧光粉受电子撞击而发光。VFD的工作原理与电子管的工作原理基本相同。 VFD分为静态屏和动态屏两种。静态屏采用静态工作方式,动态屏采用动态工作方式。静态工作方式的特点是栅极始终加有正电压,所有阳极(笔段)都单独与电极端子连接。根据这种工作方式,设计出没有栅极引出脚的静态屏以降低成本。     

真空荧光显示器阴极灯丝的可靠性设计分析

为了确保真空荧光显示器(Vacuum Fluorescent Display,VFD)阴极灯丝发射电子的稳定性,建立了灯丝变形问题的简化模型,推导了在冲击载荷作用下挠度和最大应力的解析公式,通过与有限元计算结果对比证实了解析解的可靠性,并提出了灯丝关于结构参数可靠性设计的判据.结果表明:解析解准确地描述了不同冲击载荷下VFD阴极灯丝的变形问题;最大挠度与最大应力发生在冲击载荷和VFD灯丝中点重合的位置,两者均随着灯丝加长或变细而增大,且直径对这一增大幅度的影响更明显;VFD灯丝关于长度和直径的设计判据精准高效、简单可行.研究结果可为真空荧光显示器灯丝的可靠性设计给予定性支持,并为改进灯丝性能提供结构参数优化设计的定量依据.     

InGaN蓝光LED量子效率与注入电流的关系研究

研究了InGaN蓝光LED量子效率随注入电流的变化关系,当注入电流还未达到额定电流时,LED量子效率就随着注入电流增加而快速降低。通过Matlab计算出在俄歇复合的无辐射复合机制下量子效率与注入电流的理论关系式。与实验值的拟合结果显示,大电流注入下,LED的效率衰落同时由俄歇复合及其产生的热电子从发光有源区泄露引起。由蓝光LED这一效率-电流特性,提出了增强InGaN蓝光LED效率的途径。     

高效高亮度硅基顶发射有机电致发光器件的研制

以半透明超薄金属银作为阴极,紫外臭氧处理的厚金属银作为阳极,制备了高效率高亮度的黄光硅基顶发射有机发光器件。当电压为9V时,器件的最大电流效率为4.9cd/A,当电压为17V时,器件的亮度达到14 040cd/m2。通过增加掺杂浓度及阳极厚度对器件结构进一步优化后,器件性能显著提高,其电流效率在外加电压为10V时达到11cd/A,相应亮度为21 748cd/m2.顶发射器件中存在的微腔效应能有效提高器件的发光效率以及亮度,但是也会使器件的共振波长随着观察视角的增大而蓝移。由于采用合适的发光材料,本实验制备的器件的发光峰值在0°~75°视角范围内几乎没有变化。     

高频数字X射线管灯丝发射特性对比研究

选择X射线DR摄影系统用国产与进口X射线管,进行灯丝发射特性对比研究,评估国产X射线管满足高频数字X射线机使用的有效性。采用万东50kW高频高压发生器,在相同负载条件下,分别测试进口和国产X射线管的大小焦点灯丝初级电压、灯丝初级电流、高压初级电流,并将灯丝初级电压和初级电流换算成灯丝次级电压和次级电流进行数据分析。对应选择的多档kV,在25~100mA管电流范围内,两种X射线管的小焦点发射特性均呈线性。在125~630mA管电流范围内,两种X射线管的大焦点发射特性呈线性。在相同管电压情况下,进口X射线管小焦点发射效率高于国产X射线管平均9%左右;进口X射线管大焦点发射效率低于国产X射线管平均2%左右。国产X射线管灯丝发射特性能够匹配国产高频数字X射线机,满足临床X射线诊断使用。配套DR专用摄影系统时,可将小焦点实际焦点宽度适当减小,既可提高影像质量,也可降低灯丝损耗。     

工业微波磁控管开关电源系统设计

研究了磁控管驱动电源的设计方法.主电路采用谐振拓扑结构,易于实现软开关,利用升压高频变压器的漏感作为谐振电路的一部分,简化了主电路设计.采用磁控管阳极高压和灯丝供电电压分开方案,实现灯丝电流随功率变化,来提高磁控管的使用寿命.使用PWM芯片设计了主控制电路,通过外部给定信号实现电源功率调节.设计的电源具有灯丝电流过小、高压过压、过功率、高压短路和过温等多重保护.在1500W的样机上进行了实验,对设计方法的有效性进行了验证.     

空穴传输层厚度对有机发光二极管性能的影响

采用聚乙烯基咔唑(PVK)作为空穴传输层,8-羟基喹啉铝(Alq3)作为发光层,制备了结构为ITO/PVK/Alq3/Mg∶Ag/Al的有机发光二极管(OLED),通过测试器件的电流-电压-发光亮度特性,研究了空穴传输层厚度对OLED器件性能的影响,优化了器件功能层的厚度匹配.实验结果表明,OLED的光电性能与空穴传输层的厚度密切相关,空穴传输层厚度为15nm时,OLED器件具有最低的启亮电压,最高的发光亮度和最大的发光效率.     

利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

Enhanced carrier balance by organic salt doping in single-layer polymer light-emitting devices

We have showed that the doping of an organic salt into a PVK-based polymer emissive layer could enhance the carrier balance greatly to result in higher luminance and luminous efficiency. It is found out that the salt-doped devices show the similar operating characteristics of frozen-junction light-emitting electrochemical cells (LECs). With the salt doping of 0.6 wt.% and an appropriate salt activation process, the fabricated PVK-based polymer light-emitting diodes (PLEDs) shows the luminous efficiency of 15 cd/A at the highest luminance of 55,000 cd/m² even without an electron-injecting LiF layer. Due to the enhanced carrier balance, the luminous efficiency is found to be maintained from the turn-on voltage to the voltage for the maximum luminance, which means a linear relationship between luminance and current density.     

Improvement of luminance and luminous efficiency using addressvoltage pulse during sustain-period of AC-PDP

To improve the luminance and luminous efficiency of a surface-discharge alternate current plasma display panel (ac PDP), auxiliary voltage pulses were applied to the address electrode during a sustain-period. The luminance and luminous efficiency exhibited maximum values at an address voltage of 100 V and pulse width of 1 μs. An improved luminance of 21.4% and luminous efficiency of 24% were simultaneously obtained based on the proper adjustment of the widths and amplitudes of the address voltage pulse. Accordingly, the proper control of the amplitudes and pulse widths of the auxiliary address voltage during a sustain-period can improve both the luminance and the luminous efficiency in a surface-discharge ac PDP     

试论真空荧光显示屏技术发展

真空荧光显示屏(VFD)是由阴极、栅极和表面涂有荧光粉的阳极真空电子管发展而来的,vFD以发光亮度高、多色显示容易、显示图案灵活、视角大、可靠性高和寿命长、自发光、驱动电压低等优点而被广泛地应用在各个领域.     

Experiment study of forming and activation of conductive film of the surface conduction electron emitter display

The flat panel SED (surface-conduction electron-emitter display) is a photoelectric display device based on field emis- sion theory. It belongs to FED (Field Emission Display). SED combines the advantages of CRT (Cathode Ray Tube) and of FPD (flat panel d…     

Fabrication and field emission characteristics of a novel planar-gate electron source with patterned carbon nanotubes for backlight units

This paper describes the fabrication of backlight units(BLUs) for a liquid crystal display(LCD) based on a novel planar-gate electron source with patterned carbon nanotubes(CNTs) formed by electrophoretic deposition. The electric field distributions and electron trajectories of this triode structure are simulated according to Ansys software.The device structure is optimized by supporting numerical simulation.The field emission results show that the emission current depends strongly on the cathode-gate gap and the gate voltage.Direct observation of the luminous images on a phosphor screen reveals that the electron beams undergo a noticeable expansion along the lateral direction with increasing gate voltage,which is in good agreement with the simulation results.The luminous efficiency and luminance of the fabricated device reaches 49.1 lm/W and 5500 cd/m2,respectively.All results indicate that the novel planar-gate electron source with patterned CNTs may lead to practical applications for an electron source based on a flat lamp for BLUs in LCD.     

Organic Electroluminescence Using TPD as the Emitting Layer

Organic electroluminescent thin film using TPD as an emitting layer with structure of Glass/ITO/TPD/Al is fabricated. Its V-I curve, V-B curve and electroluminescent spectra are measured and analysed.The blue emission with luminance of 0.74 cd/m 2 and luminous efficiency of 1.35×10 -3 lm/W is achieved at DC voltage of 24 V.     

彩色等离子体显示器用荧光粉

本文阐述了荧光粉的发光特性对彩色等离子体显示器（ＰＤＰ）性能影响。介绍了荧光粉激发光谱和相对发光效率的测试方法，并对常用真空紫外荧光粉的发光特性进行了比较。最后分析说明了荧光粉的涂覆面积、厚度、颗粒度大小等因素对ＰＤＰ亮度和光效的影响。     

GaN基白光LED温度特性实验研究

实验研究了恒流驱动条件下,GaN基白光LED的正向电压、发光光谱和发光效率随环境温度的变化情况.结果表明,在输入电流恒定的情况下,随着温度的升高,结电压和发光强度与温度具有良好的线性关系,并且GaN基白光LED的发光颜色总是向蓝光漂移,而小电流驱动时比大电流驱动时蓝光漂移更明显.根据实验结果,分析了器件的最佳额定工作电流.

Abstract：

Under a constant driving current, the changes of the forward voltage, emission spectrum and luminous efficiency of GaN-based White LEDs with the ambient temperature are studied experimentally. It is found that the forward voltage and the luminous intensity depend on the temperature linearly with constant injection current, and luminous colors of GaN-based White LEDs always shift towards blue. And the blue shift with low driving current is more obvious than that with high driving current. According to the results, the best rated operating current of GaN-based white LEDs is discussed.