I amused myself by dismantling a failed 220V mains LED bulb of this type and thought the results might be of interest.

There are 75 LEDs arrayed on a flexible pcb wrapped round a hexagonal-sectioned hollow ceramic(?) former, shown here (damaged at the base during dismantling):

This is the LED array with the pcb unwrapped and flattened out:


The flattening resulted in fracture of parts of the embrittled pcb.
I was unable to trace out the circuit, but the LEDs appear to be in at least one series string. Mains is input top left and goes to a MB10F bridge rectifier. The other two semiconductor devices are both LED string drivers, type PT4515C, suggesting there are two strings. However, on testing the array I found only one dud LED, so would have expected the non-affected string to light if there were indeed two strings .... but it didn't.

 

Maybe the 2 string is for 110v versions of the bulb?

That bulb would have still be working on 110v then, at 50% brightness. Just more evidence that 110v is far superior to the inferior 220v.

 

To learn more about various types of LED bulbs, look for Big Clive's youtube channel. He frequently dissects LED bulbs, reverse-engineers the schematic and explains the circuits in detail.

 

Here's a 100W Cree ConnectedMax bulb:


The LEDs around the perimiter are 9 strings in series. Haven't checked how the singles are connected. The 4 6-pin LEDs in the center are very bright RGB.

The missing white LED on the outer perimeter is from a botched attempt to remove it using soldering tweezers. The board is attached to an aluminum heat sink and I'm going to try using a hot plate. They each have 3 LEDs in series. Haven't checked the orange ones yet.

Don't know how it works. It was given to me in a box of stuff, already partially torn down.

 

Maybe the 2 string is for 110v versions of the bulb?

I wondered about that, but have since done the maths.
Each PT4515C is configured by its associated 40R2 Ohm resistor to limit current to 0.6V/40R2 = 15mA.
110V x 15mA x 2 = 3.3W. But the bulb is rated 7W.
The only thing that now makes sense to me is that there is only one string and the two chips are acting in parallel to drive it. 220V x 15mA x 2 = 6.6W.