In a recent video i took apart an led sign module. These are basically a string of modules that you mount behind signage, either with double-sided tape for a screw and it provides illumination for signage. But what intrigued me was the fact that this is a 240 volt bus ac. So these units take that ac in and then use it to power.

Just three leds and i was wondering how it did it when i opened one of the modules up and i'll zoom down on this. As a brief recap of, what's in them, i found there's a bridge rectifier, very minimalist, a linear current regulator and then just three leds and two resistors and to actually get the high voltage. These leds are actually really high voltage leds. So i thought, let's buy some blue ones and the reason for buying the blue ones is because they will have uh bare leds in them.

These ones do have blue chips in them, but they have the phosphor and that hides. What's actually inside you'll see a slight shimmer here, there's no smoothing in that there are no capacitors. There is a slight ripple on the camera, but not to the human eye. But anyway, i bought some led modules and i took one apart and then i took a good close look at that bare led in there.

Let me show you what i found i found. Let's turn it sideways, that's good, better and i'll zoom in might be a bit blurry. Only because i took this of the camera through a microscope inside are two led blocks and i'm guessing. The reason that they've got two led blocks is because the 120 volt version of this module system will just have one of these inside, but each of these blocks consists of one two, three four by one: two, three leds and they're all just coupled in series.

So, for instance, this gold bond comes on from one connection, goes through all these leds across through these leds across through these leds jumps across down through these ones up through these ones and down through these ones and then to the other connection. So, basically speaking, you end up with 24 leds in series and those 24 leds have a typical for a voltage of about 3 volts so 24 times the three volts. That's a 72 volts, i measured across it, so they are really high voltage leds very unusual construction. I thought it almost looks like separate chips because they don't seem 100 aligned, but maybe that's just the way they are deposited onto the material and also these little electrodes.

I thought that maybe they'll just be a sort of patch of light in the middle, but i powered one of the modules up with resistors to limit the current through it. So i could loot it through the microscope and the whole surface of these gallium nitride leds lit evenly very interesting, very unusual construction. So as another recap of the circuitry in these, i shall show you the structure again. Just in case you missed the original video, the power bus comes through, you've got live and you've got neutral.

It takes a tap off in the module to a bridge rectifier to convert it to east from ac to dc, and then it goes through an led, resistor, led, resistor and led. I can actually just lay them right on the thing here. Just so, you can actually see the leds and resistors the resistors are to limit what we decided on patreon. We decided they must be for a peak current so that in the time it takes the circuitry to stabilize these resistors will just kick in and they'll.

Just actually nip a little bit of the peak current off that to keep it to sensible levels. There's leds with 72 volts is about three volts dropped across the resistors, because at six milliamps it all adds up uh to a level whereby that, if, when you deduct it from the 240 volts, all that's being dropped across this little linear current regulator at the bottom Is 18 milliamps, so it's only dissipating one or 200 watts, depending on the sort of voltage. That's very impressive! That's the equivalent of just a quarter watt, resistor dissipation, very interesting circuitry, so um yeah. They were well worth.

Taking a look at. I wasn't expecting that they could even fit that number of leds in array, but it's just how things have gone these days. I wonder if they are. I don't think they're chip on.

I don't think they're flip chip leds think they're just dedicated purely to this task. Presumably uh designed specifically for led lamps to keep the circuitry symbol with the linear regulator and for these sound modules, but very interesting, well worth exploring and buying one of those just to actually take a look at the chip.