Hello,
I have a Feit overhead lamp (43W) I was trying to install. It slipped out of my hands and banged hard on one side. When I tested it, it flashed on/off once every two seconds (i.e. on for a second, off for a second). I took it apart, and disconnected the LEDs and a "motion sensor" from the power board, and I still heard the on/off sound (I think via ringing of an inductor, so figured the problem was still there and I could isolate it to this PCB). I had to learn about SMPS to begin to figure out what was going on, and how a mechanical impact could damage something to cause this. I have removed various parts to confirm the high power side is fine, and the post bridge rectifier DC voltage is stable (at ~130VDC). The MOSFET seemed to be okay. Various diodes seem to be okay. In frustration, I started to map out the circuit. I do not know if I got it exactly right, but I think it is pretty close. What I don't understand is how the IC is powered from a transformer auxiliary coil when the primary coil isn't powered on until the MOSFET is turned on, which doesn't happen unless the IC is powered?! I will attach the circuit diagram, but if you could offer help on a) how is this suppose to work to produce what I believe is the 60V constant current needed to power the strip of 60 LEDs? and b) how can an impact cause the behavior I'm seeing? That is, what could be damaged to cause this? Please note that I do have a basic understanding of how the SMPS works, but many schematics show the IC powered from the DC side before depending on the MOSFET to power the transformer. This circuit is different and confuses me. Also, my suspicion is the IC is powering on, then off, and maybe that's why it cycles (perhaps no current sense, or low voltage, etc.)? But not at that cycle rate. I don't see anything in the specs to suggest 1 second on/off anywhere. Thanks for any help or insight you can provide!

I have a Feit overhead lamp (43W) I was trying to install. It slipped out of my hands and banged hard on one side. When I tested it, it flashed on/off once every two seconds (i.e. on for a second, off for a second). I took it apart, and disconnected the LEDs and a "motion sensor" from the power board, and I still heard the on/off sound (I think via ringing of an inductor, so figured the problem was still there and I could isolate it to this PCB). I had to learn about SMPS to begin to figure out what was going on, and how a mechanical impact could damage something to cause this. I have removed various parts to confirm the high power side is fine, and the post bridge rectifier DC voltage is stable (at ~130VDC). The MOSFET seemed to be okay. Various diodes seem to be okay. In frustration, I started to map out the circuit. I do not know if I got it exactly right, but I think it is pretty close. What I don't understand is how the IC is powered from a transformer auxiliary coil when the primary coil isn't powered on until the MOSFET is turned on, which doesn't happen unless the IC is powered?! I will attach the circuit diagram, but if you could offer help on a) how is this suppose to work to produce what I believe is the 60V constant current needed to power the strip of 60 LEDs? and b) how can an impact cause the behavior I'm seeing? That is, what could be damaged to cause this? Please note that I do have a basic understanding of how the SMPS works, but many schematics show the IC powered from the DC side before depending on the MOSFET to power the transformer. This circuit is different and confuses me. Also, my suspicion is the IC is powering on, then off, and maybe that's why it cycles (perhaps no current sense, or low voltage, etc.)? But not at that cycle rate. I don't see anything in the specs to suggest 1 second on/off anywhere. Thanks for any help or insight you can provide!