Today I dismantled (I hope this is the correct verb) a flyback transformer. The thing that I've never seen is that one end of one of the windings is "glued" to the ferrite core (Before you ask; yes, the glued end is coated with solder).
Here's the schematic of the transformer (neglecting the dots):
Core: EE16 with center air gap
Bobbin: EE16 horizontal 2x5pin
Winding structure (from inner to outer):
1) 56 Turns - half of primary (Np1)
2) 35 Turns - Ng
3) 11 Turns - Secondary (Ns)
4) 13 Turns - Auxilliary (Na)
5) 50 Turns - Remaining half of primary (Np2)
One end of the Ng winding is GND and the other end is glued directly to the ferrite core. Ng is in phase with Na wrt GND.
So, I have a few questions:
1- What is the purpose of Ng winding? For better EMI performance?
2- Related to Q-1, is there any difference between direct ground connection and connection through a winding? Also, what if there was an external inductor (e.g. I-Core) instead of the Ng winding?
I know that iron-core power transformers are grounded for safety. But I think that this is different.