Other Parts Discussed in Thread: LM3411
I’m running into some issues with the TL103WB, I was wondering if you could have a look at my circuit. I’m getting around double the expected voltage (6.6V instead of 3.3V) out of the flyback. I’ve tried both replicating the open-emitter drive and just direct-driving R38 with the output of the new op amp, the behavior is pretty similar either way.
The existing flyback circuit pretty closely-follows TI App Note AN-1095, here’s an excerpt of the actual circuit I’m working with. The attached PDF is a scan of my red-line drawing that replaces U14 (the LM3411) with the TL103WB.
The main difference between the two ICs besides the open-emitter output appears to be that the original part uses a VCC-referenced fixed voltage on the non-inverting op amp input whereas the new op amp puts a ground-referenced fixed voltage on the non-inverting op amp input. However, my updated feedback divider values should have compensated for that. The only other thing I noticed is that I’ve effectively doubled the value of Rf (100k vs 52k internal to the original part), but I’m not sure that would effect the output regulation vs just affecting the loop response in the transfer function. Either way, my next step is going to be trying 16.9k and 52.3k resistors on the divider in place off the 32.4k and 100k that are currently in there.
