Reverse engineering a failed LED bulb

One of my LED bulbs failed yesterday so I decided to reverse engineer it, pretty much the way bigclivedotcom would himself do.

The PCB within my bulb is as per below:

PCB of my failed LED bulb by Luigi Di Fraia

PCB of my failed LED bulb

It looks like one of the LEDs failed (marked with a circle around it and an F nearby). Although the PCB provides pads for heat dissipation, I think the choice of materials is pretty poor and heat is eventually guaranteed to destroy one of the LEDs.

Here’s the back side:

PCB of my failed LED bulb by Luigi Di Fraia

PCB of my failed LED bulb

The burning is quite evident in the above image. In fact, the PCB looks quite cheap and thin: there’s no aluminium substrate for heat dissipation. Although aluminium helps with heat dissipation, it makes soldering a lot harder than on common PCBs as it is very effective at absorbing the heat from a soldering iron’s tip. So it looks like it might be a manufacturing trade-off.

Finally, here’s a scribble of the circuit in use by this LED bulb:

Schematics of my failed LED bulb by Luigi Di Fraia

Schematics of my failed LED bulb

As some of you might have guessed, this is a capacitive dropper circuit with four diodes to implement a bridge rectifier.
The bleeder resistor is used to discharge the capacitor on the left of the circuit when the bulb is taken out and avoid a tiny electric shock when its contacts are touched.

About luigidifraia

I am a Senior DevOps Engineer so I get to work with the latest technologies and open-source software. However, in my private time I enjoy retro-computing.
This entry was posted in Reverse Engineering, Technical and tagged . Bookmark the permalink.

2 Responses to Reverse engineering a failed LED bulb

  1. e5frog says:

    Lucky you, my latest broken LED light had the electronics epoxied, only the LED-panel was detachable.

  2. Pingback: Smart meters: what to know before you get one | Luigi Di Fraia's e-Footsteps

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