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I bought several LED bulbs about 2 years ago, and now before turn LEDs steady on, some of them flash for some time. Frequency of flashing may differ from bulb to bulb. After some time flashing, they turn LEDs steady.

Here's the device it (supposed) to use: BP2832, but datasheet shows BP2832A chip, while my bulbs use chip without A code.

Interestingly, I opened one of bulbs, and drew its circuit diagram, and it differs with datasheet. I hardly believe that adding A code will change pin assignment, and think there's mistake in datasheet. Edit: datasheet in Chinese language shows correct pin assignment!

So here's the actual circuit:

Actual circuit of the LED bulb

(sorry for childish drawing, I want to show differences with typical circuit shown in datasheet). "+" means two resistors in series, "|" means two resistors in parallel.

Here's the board from both sides:

enter image description here enter image description here

Nothing really damaged, the only green plastic coating torn off one of the capacitors, and big resistors (15R+15R) become kind of grayish because of heating of the bulb.

If you came across this "blinking" issue, or even had been dealing with this buck LED driver, please share what do you think is the cause of issue and what is possible order of replacement.

Thank you!

Update: here're caps

enter image description here

400 V caps are 105 degrees C rated, 50 V is 125 C rated. As Spehro reasonably noticed, I did mistake in 50 V cap value - it is 22 uF.

I do not have equipment to measure capacitance or ESR, I will just look for replacement.

To be continued...

Update: Here's the follow up question with the bulb redesign.

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  • \$\begingroup\$ Blinking can be caused by internal protection ; OCP, OTP (150'C) or OVP controlled by L value, string size and ROTP or defective parts \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 17 '16 at 1:02
  • \$\begingroup\$ It looks like they made a mistake on original pin#'s but corrected by picture upside downs and order changed in schematic to 1423. pin#'s should be always CCW from top. 1234 from dot in bottom left. Then it was fixed in "Revision A " \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 17 '16 at 1:06
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A reasonable guess is that the electrolytic capacitors have dried out a bit and the increased ESR (Equivalent Series Resistance) is causing some instability.

The circuit is very compact and does not look particularly efficient, so the parts probably are running rather hot. The lifetime of an electrolytic cap at full rated temperature is only a few thousand hours (2000 for a low cost type).

If you have an ESR meter, try removing the caps and testing them. Look up comparable size and voltage/capacitance rating parts and compare measured ESR to the specs. Incidentally, I suspect your value is incorrect on the 50V capacitor, since the size is similar to that of the 400V parts it is probably much higher in value.

enter image description here

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  • \$\begingroup\$ Thank you very much. I updated the question with pictures of caps, and you were right I was wrong with value for 50 V cap. \$\endgroup\$ – Anonymous Oct 26 '16 at 13:52
  • \$\begingroup\$ I have side question for you though. Bulb is heating heavily. What do you think is the principal source of heat - this circuit (two big resistors) or LEDs? They are covered by one big round body aluminium heat sink, I can not identify what is heating more making bulb extremely hot that I can not touch it. \$\endgroup\$ – Anonymous Oct 26 '16 at 15:44
  • \$\begingroup\$ It's probably distributed around - hard to say what is the primary source - that PSU does not look very efficient, but the LEDs will have irreducible power dissipation. If you can keep it cooler it will last longer. \$\endgroup\$ – Spehro Pefhany Oct 26 '16 at 16:57
  • \$\begingroup\$ As a follow up to your recommendation, I am thinking to completely discarding this circuit, and build own converter for whole chandelier. The circuit above is having 2 parallel sets of LEDs, 7 each. BP2832 supplies 254 mA of constant current @ 43 V, thus single LED is 127 mA @ 6 V (if I calculated it properly). Chandelier has 5 bulbs = 10 sets of 7 LEDs. Can you please recommend the circuit for such application? Thank you. \$\endgroup\$ – Anonymous Dec 6 '16 at 18:54
  • \$\begingroup\$ @Anonymous This is really a very separate question. There are many, many options for LED drivers. \$\endgroup\$ – Spehro Pefhany Dec 6 '16 at 18:56

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