Freeing a three-way LED light bulb’s insides from their captivity

Article By : Brian Dipert

引用一个past blog post of mine从2019年中开始：

我的一些最受欢迎的博客和拆解common theme … LED light bulbs! You all sure love your incandescent-successor illumination sources!

Well, here’s another one ;-). At the beginning of this year, one of the archaic three-way incandescent bulbs in our living room table lamps fully (more on that adverb shortly) failed. Exemplifying that Itoolove incandescent-successor illumination sources, not to mention that Ibleed green，我用基于LED的继任者代替了它。当我这样做时，我替换了另一台台灯中同样的老年（但仍然功能齐全的）伴侣，将白炽的前身降级为“紧急”助长了储存的存储。

动机here诚然,至少在一定程度上的审美;自从我was replacing the initial dead incandescent anyway, I also migrated from a “soft” (sometimes also called “warm”) white 3000K bulb to a more book reading-friendly 4000K “natural” (aka, “cool”, “natural” or “neutral”) white one. And since it’d look odd to have two lamps in the same room with different color temperature illumination sources…well…

Specifically, I found a three-way LED four-pack in claimed “Used-Like New” condition on亚马逊仓库为了less than $13, which was also less than half the brand-new four-pack equivalent price. Alas, as issometimes the casewith stuff acquired from the Warehouse area of Amazon’s website, while three of the bulbs worked fine, the fourth one was as dead as a doornail (or, if you prefer,a parrot）。一切都很好；亚马逊立即部分退还了我为支付非功能性灯具的费用所支付的费用的¼，我什至不需要将其发送回去。提示一个单词的想法……您猜到了……“拆除！”

我分析的一部分动机是个人的。从概念上讲，我已经弄清楚了三向白炽灯的工作方式。里面有两个细丝，具有不同的管腔光输出功能，并且在“关闭”，“低输出丝”，“高输出丝”和“低和高输出丝之间”之间选择了插座开关。(strictly speaking, therefore, they’re actually “four-way” bulbs). Common combinations are 30/60/100W and 50/100/150W; to my earlier “fully” adverb foreshadowing, when one filament burned out the other would still sometimes work for a while…which is why I must confess to having a couple ofotherThree-way incandescents also in “emergency” spares storage, one with masking tape stuck to it with the phrase “50W-only” scrawled on it, and the other adorned with “100W-only”. Thrifty of me, eh?

But how did the one/other/both/none switching work at the socket? And how did the operation translate to an LED bulb-based implementation? That’s what I wanted to find out, and to share with you. Voila our victim, without further ado:

这是最初的功能动作在基础上发生的地方：

您可能不会注意到什么是不同的，直到您看到了我的拆卸堆中的传统图像（尽管可变性）也是如此：

（顺便说一句，请注意此可调光的LED灯泡内部看起来像细丝结构的暗示。您将不得不等待将来的拆解才能找到更多信息！）

See the extra contact ring in the three-way? It’s the key. Here’s what an incandescent three-way equivalent looks like, courtesy of维基百科的条目：

And here are a couple of Wikipedia-provided images of an associated three-way socket:

I’d always figured that the three-way operational concept was pretty simple, but as the bulk of lights in my residences have either been traditional two-way (on-and-off) or fully variable dimmable, I’d just never bothered digging into the details until now. Here’s Wikipedia’s take:

A standard screw lamp socket has only two electrical contacts. In the center of the bottom of a standard socket is the hot contact (contact one in [earlier] photo), which typically looks like a small metal tongue bent over. The threaded metal shell is itself the neutral contact (contact three in photo). When a standard bulb is screwed into a standard socket, a matching contact on the bottom of the bulb presses against the metal tongue in the center of the socket, creating the live connection. The metal threads of the bulb base touch the socket shell, which creates the neutral connection, and this is how the electrical circuit is completed.

A 3-way socket has three electrical contacts. In addition to the two contacts of the standard socket, a third contact is added. This contact is positioned off-center in the bottom of the socket (contact two in photo). This extra contact matches a ring-shaped contact on the bottom of a 3-way bulb, which creates the connection for the second filament inside the bulb… The center contact of the bulb typically connects to the medium-power filament, and the ring connects to the low-power filament. Thus, if a 3-way bulb is screwed into a standard光插座只有中心接触，只有中型灯丝才能运行。

这是一个动画，讲述了所有这些的作用：

一切都很好，但是LED灯泡没有细丝。所以…？？？This particular bulb doesn’t work, as you already know, and I’m not going to rip the globe off a perfectly good one to observe it in illuminated operation, but maybe if we look inside this one, we can hazard a reasonable guess. Onward and inward:

这很有趣。中间是MT7606E高电流精密衬里LED驱动器from a中国公司称为Maxic Technology, a four-contact female connector (whose male equivalent, currently connected—as as you can see from the pins’ ends sticking through—presumably is soldered to the PCB in thebulb sleeve), and a passive (a resistor, if the PCB markings are correct). Surrounding them are two concentric rings of LEDs: 15 for the inner, and 36 for the outer. My guess is that the inner ring handles the 50W-equivalent “low” setting, while the outer does 100W-equivalent “medium” duties, and all LEDs illuminate for “high”.

让我们继续前进（新的LED灯泡肯定是easier to disassemble than their forebears!):

All we get is a peek at the PCB inside; for a fuller view, we first need to twist off the base:

注意从PCB延伸到灯泡端的三根电线；白色将灰色接触到中心的“热”接触，而灰色则转到偏心的“热”接触环。同时，在灯泡组件期间，黑色“中性”电线连接到底座。剪断前两根电线，底座与灯泡端分开，提供了两者的全面视角：

我们去了：

从LED板中断开PCB的连接使我们两者的两侧都没有打扰：

几个大帽子和一个变压器顶部：

在另一侧，一个二极管，两个电阻，两个MB10F桥梁整流器and a mystery IC labeled “MT7712S”. Presumably it’s也来自Maxic技术，但我在网上找不到任何信息；知识渊博的读者见解是始终欢迎的！

And这就是她（或更准确地说，在这种情况下，他）写道! I hope you’ve found this teardown “illuminating” (insert sad trombone sound). Sound off with your thoughts in the comments!

本文最初发表在EDN。

Brian Dipertis the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter。