Hello,
The Error Amplifier inside the LT3799 is unusual. Usually, a “generic” error amplifier has an incoming signal_to_be_regulated coming into one of its pins, and then the other input pin of the error amplifier is a reference voltage.
The Error amplifier inside the LT3799 doesn’t seem to be like that. …It has a reference voltage on one pin, (or all three of them as it takes the lowest of the three CNTRL voltages) but the other input pin seems to be connected to the output of the scaled DC Bus voltage signal.
When a “generic” error amplifier is regulating, then the voltage on both of its input pins usually should be the same. But in the case of the LT3799 that would mean the scaled dc bus voltage being a constant voltage…..which it shouldn’t be…obviously.
It doesn’t make sense. Do you know what’s going on with the error amplifier inside the LT3799?
The attached LTspice simulation (and pdf schematic) shows two almost identical simulations of the LT3799. The only difference is that one has a 100n capacitor connected as feedback on its internal error amplifer…whereas the other one shorts this capacitor out…so the error amplifier behaves as a simple voltage follower…………………..the circuit waveforms for both simulation circuits, as you can see, are the same……so what on earth is the point of the Error Amplifier inside the LT3799?