It would not surprise me if this was a custom ASIC, OsRAM is a huge company= , and already doing ASIC's for other products, and if they are using a olde= r technology...say 56nm for this, this chip would be pennies. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of John C= oppens Sent: Thursday, November 01, 2018 7:58 AM To: piclist@mit.edu Subject: [EE] Unknown LED current regulator Hello all. I've been really surprised at the variations of the circuitry inside LED bu= lb replacements. A while ago, I bought a couple of bulbs ('Great Value'-bra= nd, a local Walmart product), which started showing failing after just a co= uple of weeks. Opening them up showed that they were fed by just a (linear)= series regulator. So much for green energy. Now I acquired a couple of OSRAM bulbs, and opened one up just to investiga= te. It did have a switching current regulator, but it used a 4-pin chip for= which I could not find any data. In fact, I didn't find _any_ 4-pin curren= t regulator IC. I've attached the circuit. I suspect the 1.8 Ohm resistor to be the current= -determining component. Strange is the (I suspect) transformer which is act= ually across the LEDs (I'm not positive about it's internal connections. I = measure 10 Ohm across two pins, 14k across two other pins, but without unso= ldering). 12 LEDs (I suspect triplets) are connected between + and -. Does anyone have an idea which IC this could be? It's marked 9938F and S1C0= 1X. No logo as far as I can detect. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .