基于自适应牛顿算法的LED视频显示系统的研制

LED显示屏已被广泛应用于各种场合,通常情况下,需要对视频图像进行缩放处理,从而符合LED显示屏的物理分辨率.针对传统LED插值缩放算法在插值后导致图像边缘模糊的现象,提出了一种自适应牛顿播值算法,通过在插值之前进行像素相关度的自适应判断,可以较好地保留图像的高频信息,消除图像边缘模糊的问题.同时,给出了基于自适应牛顿算法的LED视频显示系统的FPGA实现,系统最终可以实现较好的显示效果.     

基于ATmega128单片机的点阵广告屏设计

为了实现AVR单片机对LED点阵显示系统的控制,采用ATmega128作为下位机MCU,通过接收上位机发送的显示内容和显示模式的串行信号,实现16×32高亮点阵屏的一行多个文字或符号的显示。系统实际运行稳定,显示效果良好,便于多块点阵屏的扩展,作为高职学生的大学生实践创新有较高的实践意义。     

基于双同步斩波模式的LED声控灯驱动电源设计

提出了基于双同步斩波模式的微功耗LED声控灯驱动电源设计方法。该驱动电源用一个单片机控制两个开关管分别为主电源和待机电源提供工作电流。主电源采用全波斩波工作模式为LED灯组提供工作电流;待机电源采用半波斩波工作模式,从而大幅降低了待机功耗。该驱动电源结构简单,可在50~60 Hz频率的180~250 V的宽电压范围内工作,具有恒流驱动功能和微功耗特性,且稳定可靠和较高的性价比。     

Failure analysis on reflector blackening between lead frame electrodes in LEDs under WHTOL test

Blackening induced lumen decay in a QFN LED after WHTOL reliability test was reported and analyzed in this paper. A new LED blackening failure mechanism was proposed based on solid experimental results. We concluded that the failure process underwent delamination between lead frame and reflector polymer composites followed by chemical penetration, composite corrosion, silver migration, and finally caused blackening failure. Delamination and corrosive de-flash agent were the key factors for the failure mode. Besides, we also estimated the influence of the failure to the optical performance through simulation. Apart from other reported factors, this study highlighted that both composite corrosion and Ag migration could generate serious illumination decrease as well. The outcome of this study is valuable for LED manufacture and quality control in the future.     

双通道PWM的冷暖白光LED混色模型研究

LED光色度的动态调节是实现智能照明的基础, 采用冷暖白光LED和双通道脉冲宽度调制(PWM)法,基于1931CIE标准建立混合光源模型,推导出混合光源色坐标、相关色温 、最大亮度、显色指数与双通道调制脉冲 占空比比值的关系式。采用暖白光(色温3282 K)和冷白光(色温12930K)两种白光LED进行 混色实验, 通过微控制器输出PWM信号控制LED驱动电源,改变冷色光和暖色光的比重,得到的混合 光源色坐 标、最大亮度、相关色温及显色指数值与理论计算值吻合很好,证明了理论模型的正确性。 理论和实验结 果还表明,混合光源在双通道调制脉冲占空比比值为1的附近可得到低色温、高显色性和大 光通量的混合白光。     

LED负载恒流驱动电源电路的研究

提出一种由过零检测电路、可控硅整流电路、高频滤波电路与PWM隔离驱动电路组成的非隔离驱动方式的高效LED驱动电源电路。通过可控硅整流器(SCR)控制角α的程控调节与隔离驱动PWM占空比的自适应负载变化,分别实现LED负载恒流驱动的粗调与细调。对各电路模块的仿真与LED负载电流调节实验均验证了系统设计的正确性。     

LED在矿灯应用的技术探讨

本文简述LED光源矿灯的发展现状,分析该矿灯的特点,提出发展该技术的主要关键。     

Site-selective occupation and luminescence property investigation of Ca18Na3Y(PO4)14:Eu2+ phosphor for full-spectrum LED

Cyan-emitting phosphors have attracted widespread attention as an integral part to realize full-spectrum lighting. Understanding the site occupation of luminescence centers is of great importance to design and clarify the luminescent mechanism for new cyan-emitting phosphors. Here, we report a cyan-emitting phosphor Ca₁₈Na₃Y(PO₄)₁₄:Eu²⁺ synthesized by the high-temperature solid-state method. The crystal structure is characterized by X-ray diffraction and refined by the Rietveld method. The diffuse reflectance spectra, excitation/emission spectra, fluorescence decay curves, thermal stability, and related mechanism are systematically studied. The results show that Ca₁₈Na₃Y(PO₄)₁₄:Eu²⁺ crystallizes in a trigonal crystal system with space group R3c. Under excitation at 350 nm, a broadband cyan emission can be obtained at 500 nm with a half-width of about 120 nm, which is caused by Eu²⁺ occupying five different sites in host, namely, Na2O₁₂ (450 nm), (Ca3/Na1)O₈ (485 nm), Ca2O₈ (515 nm), Ca1O₇ (565 nm), and (Ca4/Y)O₆ (640 nm), respectively. Moreover, crystal structure, room and low temperature spectroscopy, and luminescence decay time are used to skillfully verify the site-selective occupation of Eu²⁺. Finally, a full-spectrum light-emitting diode (LED) lamp is fabricated with an improved color rendering index (∼90.3), CCT (∼5492 K), and CIE coordinates (0.332, 0.318). The results show that Ca₁₈Na₃Y(PO₄)₁₄:Eu²⁺ has the potential to act as a cyan emission phosphor for full-spectrum white LEDs.