The bulk of the technologies and products based on them that I encounter in my everyday interaction with the consumer electronics industry are evolutionary (and barely so in some cases) versus revolutionary in nature. A laptop computer, a tablet, or a smartphone might get a periodic CPU-upgrade transplant, for example, enabling it to complete tasks a bit faster and/or a bit more energy-efficiently than before. But the task list is essentially the same as was the case with the prior product generation…and the generation before that…and…not to mention that the generational-cadence physical appearance also usually remains essentially the same.

Such cadence commonality is also the case with many LED light bulbs I’ve taken apart in recent years, in no small part because they’re intended to visually mimic incandescent precursors. But SANSI has taken a more revolutionary tack, in the process tackling an issue—heat–with which I’ve repeatedly struggled. Say what you (rightly) will about incandescent bulbs’ inherent energy inefficiency, along with the corresponding high temperature output that they radiate—there’s a fundamental reason why they were the core heat source for the Easy-Bake Oven, after all:

But consider, too, that they didn’t integrate any electronics; the sole failure points were the glass globe and filament inside it. Conversely, my installation of both CFL and LED light bulbs within airflow-deficient sconces in my wife’s office likely hastened both their failure and preparatory flickering, due to degradation of the capacitors, voltage converters and regulators, control ICs and other circuitry within the bulbs as well as their core illumination sources.

Evolutionary vs revolutionary

That’s why SANSI’s comparatively fresh approach to LED light bulb design, which I alluded to in the comments of my prior teardown, has intrigued me ever since I first saw and immediately bought both 2700K “warm white” and 5000K “daylight” color-temperature multiple-bulb sets on sale at Amazon two years ago:

They’re smaller A15, not standard A19, in overall dimensions, although the E26 base is common between the two formats, so they can generally still be used in place of incandescent bulbs (although, unlike incandescents, these particular LED light bults are not dimmable):

Note, too, their claimed 20% brighter illumination (900 vs 750 lumens) and 5x estimated longer usable lifetime (25,000 hours vs 5,000 hours). Key to that latter estimation, however, is not only the bulb’s inherent improved ventilation:

Versus metal-swathed and otherwise enclosed-circuitry conventional LED bulb alternatives:

But it is also the ventilation potential (or not) of wherever the bulb is installed, as the “no closed luminaires” warning included on the sticker on the left side of the SANSI packaging makes clear:

That said, even if your installation situation involves plenty of airflow around the bulb, don’t forget that the orientation of the bulb is important, too. Specifically, since heat rises, if the bulb is upside-down with the LEDs underneath the circuitry, the latter will still tend to get “cooked”.

Perusing our patient

Enough of the promo pictures. Let’s now look at the actual device I’ll be tearing down today, starting with the remainder of the box-side shots, in each case, and as usual, accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:

Open ‘er up:

lift off the retaining cardboard layer, and here’s our 2700K four-pack, which (believe it or not) had set me back only $4.99 ($1.25/bulb) two years back:

The 5000K ones I also bought at that same time came as a two-pack, also promo-priced, this time at $4.29 ($2.15/bulb). Since they ended up being more expensive per bulb, and because I have only two of them, I’m not currently planning on also taking one of them apart. But I did temporarily remove one of them and replace it in the two-pack box with today’s victim, so you could see the LED phosphor-tint difference between them. 5000K on left, 2700K on right; I doubt there’s any other design difference between the two bulbs, but you never know…

Aside from the aforementioned cardboard flap for position retention above the bulbs and a chunk of Styrofoam below them (complete with holes for holding the bases’ end caps in place):

There’s no other padding inside, which might have proven tragic if we were dealing with glass-globe bulbs or flimsy filaments. In this case, conversely, it likely suffices. Also note the cleverly designed sliver of literature at the back of the box’s insides:

Now, for our patient, with initial overview perspectives of the top:

Bottom:

And side:

Check out all those ventilation slots! Also note the clips that keep the globe in place:

Before tackling those clips, here are six sequential clockwise-rotation shots of the side markings. I’ll leave it to you to mentally “glue” the verbiage snippets together into phrases and sentences:

Diving in for illuminated understanding

Now for those clips. Downside: they’re (understandably, given the high voltage running around inside) stubborn. Upside: no even-more-stubborn glue!

Voila:

Note the glimpses of additional “stuff” within the base, thanks to the revealing vents. Full disclosure and identification of the contents is our next (and last) aspiration:

As usual, twist the end cap off with a tongue-and-groove slip-joint (“Channellock”) pliers:

and the ceramic substrate (along with its still-connected wires and circuitry, of course) dutifully detaches from the plastic base straightaway:

Not much to see on the ceramic “plate” backside this time, aside from the 22µF 200V electrolytic capacitor poking through:

Integrated and otherwise simple = Cheap

The frontside is where most of the “action” is:

At the bottom is a mini-PCB that mates the capacitor and wires’ soldered leads to the ceramic substrate-embedded traces. Around the perimeter, of course, is the series-connected chain of 17 (if I’ve counted correctly) LEDs with their orange-tinted phosphor coatings, spectrum-tuned to generate the 2700K “warm white” light. And the three SMD resistors scattered around the substrate, two next to an IC in the upper right quadrant (33Ω “33R0” and 20Ω “33R0”) and another (33Ω “334”) alongside a device at left, are also obvious.

Those two chips ended up generating the bulk of the design intrigue, in the latter case still an unresolved mystery (at least to me). The one at upper right is marked, alongside a company logo that I’d not encountered before, as follows:

JWB1981
1PC031A

The package also looks odd; the leads on both sides are asymmetrically spaced, and there’s an additional (fourth) lead on one side. But thanks to one of the results from my Google search on the first-line term, in the form of a Hackaday post that then pointed at an informative video:

This particular mystery has, at least I believe, been solved. Quoting from the Hackaday summary (with hyperlinks and other augmentations added by yours truly):

The chip in question is a Joulewatt JWB1981, for which no datasheet is available on the internet [BD note: actually, here it is!]. However, there is a datasheet for the JW1981, which is a linear LED driver. After reverse-engineering the PCB, bigclivedotcom concluded that the JWB1981 must [BD note: also] include an onboard bridge rectifier. The only other components on the board are three resistors, a capacitor, and LEDs.

 The first resistor limits the inrush current to the large smoothing capacitor. The second resistor is to discharge the capacitor, while the final resistor sets the current output of the regulator. It is possible to eliminate the smoothing capacitor and discharge resistor, as other LED circuits have done, which also allow the light to be dimmable. However, this results in a very annoying flicker of the LEDs at the AC frequency, especially at low brightness settings.

Compare the resultant schematic shown in the video with one created by EDN’s Martin Rowe, done while reverse-engineering an A19 LED light bulb at the beginning of 2018, and you’ll see just how cost-effective a modern design approach like this can be.

That only leaves the chip at left, with two visible soldered contacts (one on each end), and bare on top save for a cryptic rectangular mark (which leaves Google Lens thinking it’s the guts of a light switch, believe it or not). It’s not referenced in “Big Clive’s” deciphered design, and I can’t find an image of anything like it anywhere else. Diode? Varistor to protect against voltage surges? Resettable fuse to handle current surges? Multiple of these? Something(s) else? Post your [educated, preferably] guesses, along with any other thoughts, in the comments!

—Brian Dipert is 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.

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