采用 RT8487 之 8W 低成本离线式 LED 驱动器

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<div class=WordSection1> <h1>采用 RT8487 之 8W 低成本离线式 LED 驱动器</h1> Low cost 8W off-line LED driver with RT8487 <h2 id="__Bookmark__0">摘要</h2> RT8487 是一具有内部高端驱动元件，可用于降压或升–降压架构中的边界模式恒流控制器，能提供恒定输出电流至 LED 负载。它包含了可实现高功率因数和低输入电流总谐波失真率 (THDi) 的特殊电路，同时也大大减少了外部元件数量。RT8487 所用的 SOT23-6 封装使它只需使用很小的 PCB 空间，并使它成为具有很高性价比的离线式 LED 驱动器解决方案。 本文提供了如何用 RT8487 设计一个 8W 降压型 LED 驱动器的详细信息。 <h2 id="__Bookmark__1">1. 简介</h2> 低成本离线式 LED 驱动器要求具备高效率、满足 IEC61000 C 级规格的高功率因数、低输入电流总谐波失真率 (THDi)、精确 LED 电流、快速启动、仅用低成本标准零组件构成和电路设计简单等条件。以下将探讨在浮动式降压架构下以 RT8487 设计而成的 8W LED 驱动器，它能符合上述所有的要求。 主要规格: <ul> <li>输入范围 230V +/-15% (稍作改变，可将此设计变成全范围输入) </li> <li>针对一般替代型照明应用：LED 灯串 27V，I-LED = 300mA +/- 5%，P-out = 8W </li> <li>输入电流总谐波失真率 (THDi) < 20% ，满足 IEC61000 C 级规格</li> <li>启动时间 < 300毫秒</li> <li>完整保护: 输出短路、LED 开路、过电流及过温度保护</li> <li>无变压器设计，使用标准低成本零组件，主要目的是降低材料清单 (BOM) 的成本</li> </ul> <h2 id="__Bookmark__2">2. 应用电路</h2> 以 RT8487 为核心所构成的 8W LED 驱动器的完整应用电路如下图所示： <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image001_zh-cn.jpg" ><img width=622 height=318 src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image001_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图一 在图一的完整应用电路图中，RT8487 被使用于浮动式控制器降压架构下。该芯片可控制高端开关 Q1 的导通时间，借着与电感器串联之电阻 RS 来检测 LED 的平均电流，如此可检测到真正的负载电流。边界导通模式 (BCM) 切换也是透过检测零电感电流（同样是透过RS）而成。在最小漏极-源极电压 (VDS) 时的谐振点开关则是透过由 R3 调整的、从零电流侦测点 (ZCD) 算起的导通延迟时间来实现的，并透过智能算法控制导通时间以获得高输入功率因数和低输入电流总谐波失真率 (THDi)。 IC 所需的偏压是由 D2 和 C2 构成的自举电路所提供，省去外加辅助线圈，所以只需用到一般的标准磁鼓线圈，而不需较贵、客制的变压器。因启动 IC 的偏压电流低，所以可用高阻值的启动电阻 R1 和 R2，且依然能达到快速启动（一般为 123 毫秒）。完整的应用电路可建构于一个 18 x 36 平方毫米的单面 PCB。 <h2 id="__Bookmark__3">3. 主要元件值的计算</h2> 以下各节将解释各应用参数的设定。 设定平均输出电流 流过 LED 灯串的平均输出电流可由连于 RT8487 之 GND 和 SENSE 两接脚之间的外部电阻 RS 决定。由于 RS 是串连于电感器，LED 的平均电流可以透过此电阻精确地检测到。输出电流 IOUT 和 RS 的关系如下: <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image002_zh-cn.png" ><img width=82 height=30 id="圖片 3" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image002_zh-cn.png" alt="Technical Document Image Preview"></a> 本应用中，LED电流定为300mA，所以<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image003_zh-cn.png" ><img width=129 height=30 id="圖片 5" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image003_zh-cn.png" alt="Technical Document Image Preview"></a> 选用电阻 1Ω//4.7Ω 以得 0.824Ω。 启动电阻 启动电阻 (R1+R2) 的选择条件是在最低输入电压下，经此二电阻的电流须大于 RT8487 的启动电流，否则 RT8487 的 Vcc 可能永远无法达到启动电压。其常规启动电流为 25μA。 启动电阻也不能使启动电流超过操作电流，否则 VCC 电压会比自举电路设定的 VCC 还高，因此 IC 可能会启动过压保护 (OVP)。操作电流通常为 1mA。 启动电阻值和 VCC 电容 C2 会决定启动时间，定义如下: <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image004_zh-cn.png" ><img width=109 height=36 id="圖片 9" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image004_zh-cn.png" alt="Technical Document Image Preview"></a> 其中 VUVLO 为 17V，而 Istart-up 可近似为：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image005_zh-cn.png" ><img width=105 height=41 id="圖片 10" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image005_zh-cn.png" alt="Technical Document Image Preview"></a> 大多数应用中，C2 多选用 1μF。 且 R1 和 R2 都选用 1MΩ，代入后，得其常规启动电流为：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image006_zh-cn.png" ><img width=140 height=35 id="圖片 15" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image006_zh-cn.png" alt="Technical Document Image Preview"></a> 启动时间则为：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image007_zh-cn.png" ><img width=137 height=30 id="圖片 16" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image007_zh-cn.png" alt="Technical Document Image Preview"></a> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image008_zh-cn.jpg" ><img width=346 height=258 id="Picture 8" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image008_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图二 图二显示在 230V 交流输入条件下 IC 启动时的波形。当交流電源輸入时，流经 R1 和 R2 的电流即开始对 C2 充电。当 IC 的 VCC 电压超过 UVLO 值时，功率开关即开始作开关动作，并快速地对输出电容进行充电。实际测得的启动时间为 150msec。 输入电容器的选择 对高功率因数的应用来说，输入电容 C1 必须够小，才能整流正弦波的输入电压。输入滤波电容器的额定电压 VCIN 须够大，以承受最大输入电压。100nF/500V 薄膜电容器会是一个恰当的选择。为减低差模电磁干扰 (EMI)，可由两个 47nF 电容器和一个适当的电感器组成 π 型滤波器来达成。 降压电感器的选择 由于在边界导通模式下切换，电感值会影响转换器的开关切换频率。若要较小尺寸的线圈，就选择小的电感值，但它通常受限于 IC 最小导通时间（通常是 0.5μsec）和最小关断时间（通常是 0.5μsec）。 最大电感值则受限于 IC 最大导通时间（通常是 15μsec）和最大关闭时间（通常是 33μsec）。 要计算电感值，首先要计算在整流过的正弦波峰上 (Vpeak) 的最大尖峰电流值 (Ipeak): <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image009_zh-cn.png" ><img width=114 height=42 id="圖片 18" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image009_zh-cn.png" alt="Technical Document Image Preview"></a> 其中Pin为转换器的输入功率，a是LED电压与最高输入电压之比：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image010_zh-cn.png" ><img width=49 height=32 id="圖片 19" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image010_zh-cn.png" alt="Technical Document Image Preview"></a> 而F(K(a)) 是为 PFC 降压且能有低 THDi 的一个复变函数： <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image011_zh-cn.png" ><img width=509 height=30 id="圖片 20" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image011_zh-cn.png" alt="Technical Document Image Preview"></a> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image012_zh-cn.jpg" ><img width=355 height=289 id="Picture 9" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image012_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图三 在8W应用中，Pin可以由<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image013_zh-cn.png" ><img width=139 height=30 id="圖片 21" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image013_zh-cn.png" alt="Technical Document Image Preview"></a>算出。(以效率为86%作估计) 在整流过的正弦波峰上，因子 a 先被算出：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image014_zh-cn.png" ><img width=108 height=34 id="圖片 22" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image014_zh-cn.png" alt="Technical Document Image Preview"></a> 从图三或公式 (1) 可得，<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image015_zh-cn.png" ><img width=273 height=35 id="圖片 26" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image015_zh-cn.png" alt="Technical Document Image Preview"></a> 电感值的范围也可由此算出：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image016_zh-cn.png" ><img width=200 height=37 id="圖片 27" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image016_zh-cn.png" alt="Technical Document Image Preview"></a> 当电流绝对最大额定值为 1.2 A时，选择 330μH 作为 L1 值，这是在尺寸、成本和效率等方面考虑后的最佳折衷选择。 在正弦波峰上，开关频率可由此而得：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image017_zh-cn.png" ><img width=123 height=31 id="圖片 28" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image017_zh-cn.png" alt="Technical Document Image Preview"></a> (Tdelay 由连于 AND 接脚的电阻决定，见下小节。) 设定开关导通延迟时间 电感电流为零之后，电感和开关结点上的总电容会产生谐振，该电容主要为开关晶体的漏极—源极电容。为尽可能减少开关晶体管的开关损耗，RT8487 可灵活调整下一导通周期的延迟时间，以期能在最大谐振点时导通，该点即对应到最小漏极—源极电压值。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image018_zh-cn.jpg" ><img width=430 height=299 id="Picture 13" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image018_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图四 要决定所需的延迟时间，要考虑两个因子： a.从零电流侦测 (ZCD) 点到实际零电流点的延迟时间 (如图四之 t1)。因为 ZCD 点是定义在 Vsense = 20mV 时，ZCD 延迟时间可由此式算出：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image019_zh-cn.png" ><img width=103 height=32 id="圖片 6" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image019_zh-cn.png" alt="Technical Document Image Preview"></a> 在此应用中，其值为：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image020_zh-cn.png" ><img width=184 height=31 id="圖片 7" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image020_zh-cn.png" alt="Technical Document Image Preview"></a> b.从零电流点到开关谐振最大值的延迟时间 (如图四之 t2) 可由此式算出：<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image021_zh-cn.png" ><img width=114 height=22 id="圖片 8" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image021_zh-cn.png" alt="Technical Document Image Preview"></a> 其中 CSW 是开关结点的电容，主要就是开关晶体管的漏极—源极电容；在本应用中，此电容值为 38pF。谐振延迟时间即为<a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image022_zh-cn.png" ><img width=215 height=23 id="圖片 23" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image022_zh-cn.png" alt="Technical Document Image Preview"></a> 最佳谐振导通点所需的总延迟时间 Tdelay 即为 290nsec + 352nsec = 642nsec。 从零电流侦测点 (ZCD) 至下一开关晶体管导通周期的延迟时间 (Tdelay) 可藉电阻 R3 调整，R3 连接于芯片的 AND 接脚和 GND 接脚之间。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image023_zh-cn.png" ><img width=297 height=20 id="圖片 24" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image023_zh-cn.png" alt="Technical Document Image Preview"></a> • Tdelay = 大约的延迟时间，以 μs 为单位（从零电流侦测点即 Vsense = 20mV 时开始） • R3 阻值以 kΩ 为单位 根据公式 (2)，R3 = 8.2kΩ 时可得 628nsec 的延迟时间。但最后将 R3 值设为 6.8kΩ，以补偿由于开关晶体管的导通时间所造成的额外延迟。下面的图五显示了开关在最佳谐振点导通时的波形。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image024_zh-cn.jpg" ><img width=394 height=294 id="Picture 6" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image024_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图五 开关晶体管MOSFET的选择 开关晶体管的电压绝对最大额定值须够大，才能承受最大输入峰值电压及瞬间突起电源的裕量。最好选用漏极–源极绝对最大额定值至少 500V 的开关晶体管。开关晶体管的额定电流值和温度有关，为达到低成本、低功耗和高效率，折衷后选用 2A 的开关晶体管。 顺向二极管的选择 当开关晶体管关闭时，电流路径是流经连接于开关的输出点和地之间的二极管 (D1)。顺向偏压时，二极管必须有低顺向导通电压降和快速的恢复时间。二极管的反向电压绝对最大额定值则须大于最大输入峰值电压并加上裕量，而电流绝对最大额定值须大于电感的峰值电流。为求低功耗和较高效率，选用 600V/2A 的快速二极管。 输出电容的选择 为实现高功率因数和低输入电流总谐波失真率 (THDi)，电感电流会包含相当成分的低频纹波。输出电容会过滤开关的和低频纹波的电流以传输低纹波电压至 LED 灯串。有了输出纹波电压的大小与 LED 灯串的微分电阻即可决定流过 LED 的纹波电流。在此低成本的设计中，选用 220μF 的电容器，大约可过滤 330mApp 流过 LED 灯串的纹波电流。为了减少这种纹波，须要选用较大的输出电容。 <h2 id="__Bookmark__4">4. 主要性能的量测</h2> 图六显示了输入和输出端的电压和电流的波形。 从交流输入波形可看出有高 PFC 和低 THDi，输出的 LED 平均输出电流则精确地落在 296mA 上。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image025_zh-cn.jpg" ><img width=604 height=245 id="Picture 14" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image025_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图六 图七为开关工作波形。为要实现低 THDi，电感电流峰值最好是 LED 平均电流的四倍之高。从单一开关周期可看出在最小漏极–源极电压时，开关在边界导通模式 (BCM) 下切换的情形。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image026_zh-cn.jpg" ><img width=602 height=255 id="Picture 17" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image026_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图七 下表列出了整个设计的主要性能参数。在电源电压范围内，它具有优异的 LED 电流稳定性，典型的效率 (efficiency) 为 86%，且有满足 IEC61000 C 类规格的低 THDi。 <div> <table class=MsoNormalTable border=1 cellspacing=0 cellpadding=0 width=600 style='width:450.0pt;border-collapse:collapse;border:none'> <tr> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;background:#009EB8; padding:.75pt .75pt .75pt .75pt'> Vin ac </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Pin ac </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> PF </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> THD </td> <td width=95 style='width:71.25pt;border:solid #009EB8 1.0pt;border-left: none;background:#009EB8;padding:.75pt .75pt .75pt .75pt'> V-LED </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> I-LED </td> <td width=95 style='width:71.25pt;border:solid #009EB8 1.0pt;border-left: none;background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Pout </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Efficiency </td> <td width=60 style='width:45.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Ploss </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 195.5 </td> <td width=60 style='width:45.0pt;border-top:none;border-left:none;border-bottom: solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 9.59 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.96 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 11.6 </td> <td width=95 style='width:71.25pt;border-top:none;border-left:none; border-bottom:solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt; padding:.75pt .75pt .75pt .75pt'> 27.69 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.299 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 8.279 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 86.3% </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1.31 </td> </tr> <tr style='height:13.5pt'> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt; height:13.5pt'> 231.8 </td> <td width=60 style='width:45.0pt;border-top:none;border-left:none;border-bottom: solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt; height:13.5pt'> 9.64 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 0.94 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 13.3 </td> <td width=95 style='width:71.25pt;border-top:none;border-left:none; border-bottom:solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt; padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 27.74 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 0.299 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 8.294 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 86.0% </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 1.35 </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 264.2 </td> <td width=60 style='width:45.0pt;border-top:none;border-left:none;border-bottom: solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 9.68 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.90 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 17.7 </td> <td width=95 style='width:71.25pt;border-top:none;border-left:none; border-bottom:solid #009EB8 1.0pt;border-right:solid #009EB8 1.0pt; padding:.75pt .75pt .75pt .75pt'> 27.68 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.300 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 8.304 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 85.8% </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1.38 </td> </tr> </table> </div> <h2 id="__Bookmark__5">5. 材料清单</h2> 一个完整的 8W LED 驱动器的材料清单如下所示： <div> <table class=MsoNormalTable border=1 cellspacing=0 cellpadding=0 width=600 style='width:450.0pt;border-collapse:collapse;border:none'> <tr> <td width=50 style='width:37.5pt;border:solid #009EB8 1.0pt;background:#009EB8; padding:.75pt .75pt .75pt .75pt'> Item </td> <td width=50 style='width:37.5pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Quantity </td> <td width=80 style='width:60.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Reference </td> <td width=110 style='width:82.5pt;border:solid #009EB8 1.0pt;border-left: none;background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Part / Value </td> <td width=80 style='width:60.0pt;border:solid #009EB8 1.0pt;border-left:none; background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Footprint </td> <td width=110 style='width:82.5pt;border:solid #009EB8 1.0pt;border-left: none;background:#009EB8;padding:.75pt .75pt .75pt .75pt'> Remark </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> F1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1A/250V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> --- </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Fuse 1A </td> </tr> <tr style='height:13.5pt'> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt; height:13.5pt'> 2 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> LX1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 4.7mH (DR0612) </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> DR0612 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> EMI drum coil </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 3 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> L1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 330μH (CKPK1012) </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> DR1012 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Buck drum coil </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 4 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> CX1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.1μF/275Vac </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> DIP </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> X-capacitor </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 5 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> C1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.1μF/450V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> DIP </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> MPP Cap </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 6 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> C2 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1μF/50V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1206 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 7 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> C3 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0.1μF/50V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0603 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 8 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> C4 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1nF/50V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0603 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 9 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> EC1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 220μF/35V </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> DIP </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Output E-cap </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 10 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> RX1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 10K </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1206 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 11 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 2 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> R1, R2 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1M </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1206 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr style='height:13.5pt'> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt; height:13.5pt'> 12 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> R3 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 6.8K </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 0603 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 13 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> R4 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 10R </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0805 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 14 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> R5 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 100R </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0603 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 15 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> R6 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 47k </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 0805 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 16 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> RS </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1R // 4R7 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1206 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'></td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 17 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> D1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> SF28 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> DIP </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Fast 2A/600V </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 18 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> D2 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> FFM107 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> SOD-123L </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Fast 1A/1000V </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 19 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Extra-D </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1N4148 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> SOD-123 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 250mA/75V </td> </tr> <tr style='height:13.5pt'> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt; height:13.5pt'> 20 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> DB </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> TB6S </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> --- </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt;height:13.5pt'> 600V/1A diode bridge </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 21 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> Q1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> STD2HNK60 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> TO-251 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 2A/600V MOSFET </td> </tr> <tr> <td style='border:solid #009EB8 1.0pt;border-top:none;padding:.75pt .75pt .75pt .75pt'> 22 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> 1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> IC1 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> RT8487GJ6 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> TSOT23-6 </td> <td style='border-top:none;border-left:none;border-bottom:solid #009EB8 1.0pt; border-right:solid #009EB8 1.0pt;padding:.75pt .75pt .75pt .75pt'> LED driver controller </td> </tr> </table> </div> <h2 id="__Bookmark__6">6. 印刷电路板 (PCB) 的布局</h2> 可将 8W LED 驱动器的应用电路建构于一个很小的单面 PCB 上。因为是浮动式控制器的拓扑结构，IC 周围的零组件都要紧密排放且靠近 IC。布局时，应为高电压振幅提供足够的沿面距离和隔空间隙的裕量。 要注意的是，这里只是初步的布局。若要达到更优化的性能表现，还需要进一步微调：降压电感器相对于 EMI 线圈的方向需要作些修正，因目前 L1 的杂散磁场会耦合到 LX1，反而量测到较高的 EMI 读数。 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image027_zh-cn.jpg" ><img width=603 height=164 id="Picture 5" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image027_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图八 <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image028_zh-cn.jpg" ><img width=603 height=175 id="Picture 7" src="/content/dam/richtek-eds/resources/application-notes/an019/html-images-zh-cn/image028_zh-cn.jpg" alt="Technical Document Image Preview"></a> 图九 <h2 id="__Bookmark__7">7. 结论</h2> 使用 RT8487 能够设计出极具成本效益，同时具备良好性能，且满足现今市场对 LED 驱动器要求的 8W LED 驱动器。 请浏览立锜的网站<a href="http://www.richtek.com/LED/?utm_source=AN019&utm_medium=RTWWW&utm_campaign=AppNote" target="_blank" class="link">http://www.richtek.com/LED/</a>，以了解更多立锜科技创新的 LED 驱动器解决方案的相关讯息。 <div> <table border="1" cellspacing="0" cellpadding="0" style="width: 637.5pt; border-collapse: collapse; border: medium none;" class="3-51"> <tbody> <tr style="height: 17pt;"> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #009eb8; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;" colspan="2"> 相关资源 </td> </tr> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> 立锜科技电子报 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href="http://www.richtek.com/My%20Richtek/Newsletters" target="_blank">订阅立锜科技电子报</a> </td> </tr> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> 档案下载 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href="http://www.richtek.com/Design%20Support/Technical%20Document/~/media/AN%20PDF/AN019_CN.ashx">PDF 下载</a> </td> </tr> </tbody> </table> </div> </div>

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