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From this video: https://youtu.be/klaJqofCsu4
Each LED here is actually a strip of 21 LEDs, thus the high voltage of 42V per LED in the schematic here. Big Clive (the video maker) measured 227 volts across the LED array (which makes for 57V across each LED strip), but for some reason it only goes up to 159 volts in this simulation. (Increasing the voltage for each LED strip to increase the total voltage to above 159V causes the LEDs to lose brightness and flicker badly.)
You may also notice that the LEDs are run well below their 20mA rating (Big Clive doesn’t mention a current rating for the LEDs, but he does say they are under-fed current). This is because the less current you supply to an LED, the more efficient it is and the longer its life is.
You may also notice a linear regulator (the MOSFET and BJT together with a few resistors make a regulator). This keeps the brightness constant even through variations of a few volts in the power supply (as Big Clive demonstrates can happen by turning on his electric kettle). I also expected it to eliminate flicker, but with only two 4.7μF caps the power supply is too ripply and exceeds the 12V range of the linear regulator, although only slightly.
The 330kΩ resistor is to provide a discharge path for the 4.7μF capacitors to prevent the lamp from very dimly glowing when off. Since the wires in a house are very weakly capacitively and inductively coupled simply due to proximity, even a disconnected wire (for example, one connected to a light switch in the “off” position) will have nearly full voltage on it, although capable of only a few milliwatts of power. This can make cheap LEDs glow very dimly when they should be off, but thanks to the 330kΩ resistor that doesn’t happen here.
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