Inside an LED Light Bulb
What's Inside a LED Lamp
There's more than you think! If this was an incandescent bulb you'd expect to find a glass blown bulb with a single filament inside. All one has to do to light the old fashion light bulbs, is supply the right voltage into it, and the internal filament self limits itself and a certain current flows, producing light.
LEDs are nothing like this, especially the high power one's for residential and commercial lighting.
The lens on this LED spot light disperses the light to a particular angle and produces an even super bright glow. It's also an easy access way. Chipping an edge off it allows it to be pried out with a small screwdriver.
LED Die Exposed
With the lens removed, the LED die can be seen (yellow). This is the spot where all of the light comes out of. The die itself is nearly paper thin, but gets incredibly hot when operational. This is the reason for the overly sized metallic frame built around it, which acts as its heat sink. Removing the LED die from the heat sink will make the LED inoperable for any amounts of time over about 2 seconds, unless some type of cooling is in place. In the past, I've used water cooling, by simply submerging the LED into a cup of water. This works well for experimenting, but ultimately may cause water assisted corrosion.
Terminal Connector of LED Spot Light
Underneath the lens of the lamp are two screws. Simply removing these screws and cutting out the wires leading to the LED die, allow the bottom terminal cylinder to be detached from the cone of the lamp. Seen above, the cylinder is filled with a gray epoxy jelly material which is difficult to remove. This is where the electronics are housed. Let's try to break in.
Slowly Chipping Away at Epoxy
With a small flat head screwdriver, a few millimeters depth was removed from the gray plastic protection inside the LED lamp base. In the picture above, the large 100uF blue electrolytic capacitor is becoming visible, as well as the green PCB circuit board across the diameter. After a long attempt my success with this method began to decline.
Applying a diamond cutter to the perimeter of the hardened plastic of the LED lamp base finally yielded success. I was careful not to damage the internal components I had already discovered. as well as anything that might have still be hiding inside. Cutting all the way around the base of this fixture, split the thing into two halves.
Buck Converter Revealed
Splitting the two halves of plastic apart revealed the internal circuitry. Surprisingly, the gray epoxy stuff did not make too much of a mess on the PCB itself and was easily removed.
After a quick observation, my initial hypothesis was confirmed. This circuit board is a non-synchronous buck converter (step-down). An identification on the main control chip (integrated circuit) revealed that the circuit can operate with an input voltage from 4.5 to 40 volts, and current regulates with about 85% efficiency to the high power LED.
I noticed a lot of small "problems" with this commercial design that could have improved the efficiency significantly. Since LED lighting is generally only preferable by those wishing to cut electricity use and get more light for their buck, it would seem that the driver circuit would be built to push out every last bit of power to save as much money for the consumer as possible. This, unexpectedly, isn't the case.
But, overall, the circuit is pretty small and pretty cool. I really like the design. It even has a polarity insensitivity protection (diode bridge rectifier - seen in picture above as four diodes in a square shape). Plus, the circuit layout looks pretty symmetrical, from an artistic perspective... I wonder if the designer ever thought someone would have gone through all the trouble to open it up and take a peek.
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