tag 标签: wled

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  • 热度 1
    2013-5-8 23:24
    506 次阅读|
    0 个评论
    We are usually being told that using WLEDs (White Light-Emitting Diodes) for lighting purpose has many advantages. For example, high efficiency, high brightness and much longer lifetime than fluorescent lights. However, since many manufacturers wish to reduce the cost of production and to increase the light intensity, the WLEDs are being 'pushed' to the maximum power they can affort... As a result, the lifetime of those WLEDs will be shortened (or more precisely saying, the light intensity and efficiency decreases significantly) in a period of time. More importantly, the driver / controller will be burnt due to the excess loading or temperature due to the heat generated. Fig. A burnt controller in a MR16 (4x1W) WLED bulb   Although the controller PCB which is very cheap (RMB$2) can be replaced easily, many people may throw those LED bulbs which are out of order away, even if only the controller is burnt.... The result contradicts the original intention that using WLEDs for lightening up the environment.
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    时间: 2019-12-27 20:53
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    上传者: wsu_w_hotmail.com
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    降低WLED驱动器中辐射EMITexasInstrumentsIncorporatedPowerManagementReducingradiatedEMIinWLEDdriversByJeffFalinSeniorApplicationsEngineerMostmobilephonesusewhiteLEDs(WLEDs)asthestrengthofacapacitorisdirectlyproportionaltoitscapac-backlightfortheirdisplays.Li-Ionbatterieswithanoutputitanceandthevoltageacrossitsterminals.Thecapacitancerangeof2.7to4.2Varethemostcommonpowersourceisinverselyproportionaltothedistancebetweenthetermiformobilephones.SinceseveralWLEDsinseries,eachnals.Ideally,theICandcomponentsarelaidoutonthewithforwardvoltagesaround3.6V,aretypicallyusedforboardtomini……
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    时间: 2019-12-28 19:40
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    驱动WLED未必需要4V的电压驱动WLED未必需要4V的电压白光发光二极管(WLED)应用相当普遍,主要原因在于白光发光二极管可用于提供便携式电子产品显示器的背光。一般认为单一WLED需要4V的驱动电压。由于锂电池提供3.6V的电压,因此一般业界认定需要升压转换器(step-upconverter),才能以单节锂电池为WLED供电。因此,许多IC都可用于驱动WLED,其中大部分需要外部电感或飞驰电容器(flyingcapacitor),才能将电池电力提升到足够的电压。由于WLED技术日渐成熟,因此需要正向电压的需求逐渐减少。目前有许多LED的一般正向电压(VF)范围介于3.2至3.5V之间,最大范围则介于3.7至4V之间。资料表通常针对大约15至25mA的LED电流指明这类电压。本文探讨较低电流的应用,以及这些应用如何影响WLED的正向电压。文中也以德州仪器TPS75105这款全新的LED驱动器为例,说明如何以较小体积与较低成本有效驱动这些较低电压LED。LED正向电压d压超过临界值时,reWLED与其它标准p-n接面二极管类似,必须有足够的正向电压才能导电。会以WLED的正向电压提升正向电流。当电……
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    时间: 2019-12-28 20:09
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