Inside a Samsung LED retrofit tube. (Older style?)

I was expecting the circuitry in this tube to be simple, but I was very wrong.
This is an older style Samsung retrofit LED tube that can be put into existing fluorescent fixtures without bypassing the original inductive ballast.

Some notes that will make more sense after viewing the video.
The big MOSFET might be purely a safety feature that only enables the switching of the inductor once the chips circuitry is stable. It might be to avoid stability glitching at power-up that could damage the chips own FET. I don't think it will be used for the high frequency switching of the inductor given the surrounding circuitry. It will also probably shut the drive off quickly when the tube is powered down. Those are guesses though. It's quite odd circuitry.

The use of two large electrolytics across the LEDs are to reduce flicker. The positioning of one at the incoming supply end is partly to use the available space for more capacitance, but also has the advantage of being in the vicinity of cooler circuitry and therefore not likely to degrade too fast and cause visible flicker over time.

The 420 reference apparently relates to a holiday date (20th April) when certain plants are celebrated.

If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.