Understanding primary side regulation in this Flyback converter

[blue_diode]

I'm going through this Reference Design (https://www.ti.com/lit/pdf/tidrlf7) and there is something I don't get. The controller LM5020MM-2 was not designed for primary side regulation, how does this power supply regulate through the auxiliary winding? How precise it is? Does it require certain minimum load to regulate?

 

[Easy peasy]

easy, it looks at its own aux supply and scales from there to repsresent the output - the 10 ohm resistor & 1uF MLCC cap take off the leading edge leakage inductance spike to make it more representative - the 10k o/p load res helps too ( might need to be lower ohms om practice ) - note this is an app note only and is likely not fully tested ...