Hi,
I have bought some LP3783BM from lcsc, and now I'm testing them for now, I have prepared a spreadsheet based on an1028 from BCD Semiconductor Manufacturing, which I have attached it,
I have build and tried 3 different transformers, the transformer is EFD15 and I got it from a no brand supplier in china, my first problem is how to extract the core properties?
also I have winded 3 transformers, I can get around 7W out put for these configues
first config
Np =110 turns and wire size 0.12mm Naux = 26 turns and wire size 0.12mm Ns = 19 and wire size 0.45mm, I assumed Efficiency = 0.85 and the Switching Frequency = 85KHz in this config the output is around 7W
Second config
Np =79 turns and wire size 0.12mm Naux = 21 turns and wire size 0.12mm Ns = 16 and wire size 0.45mm, I assumed Efficiency = 0.8 and the Switching Frequency = 110KHz in this config the output is around 7W
For the first two configs the transformer gets hot around 25-30C above ambient
Third config
Np =57 turns and wire size 0.35mm Naux = 15 turns and wire size 0.12mm Ns = 11 and wire size 0.45mm, I assumed Efficiency = 0.8 and the Switching Frequency = 155KHz in this config the output is around 6W and the transformer gets very hot, I think in the order of 60C-70C above ambient
Also the output is around 7.5W at the beginging and when the things warms up it goes around 6.7W
I have seen they could done it around 10W with an EFD15 core size, so I want to increase the output power to 10W, do you have any Ideas?
Also I have calculated the upper feedback res to be 4.4K but I have put a 4.99K res to get 12V at output any Idea?
for now I have only 0.12mm, 0.35mm and 0.45mm wires, so is it possible to do it with these wires?
The circuit diagram

This is how I placed the air gap with some tapes to get the primary inductance near what's calculated, note that this is for the second config and it's slightly lower, but for the first config and the thrid config I was very close, almost what's been calculated


This is my active load and the output voltage and current for the second config and when the cicuit starts up and it's cool

And here is the output dropped about 1V and it has passed about 15 minutes, and the circuit warms up.

The circuit itself on a proto board
Top of the board

Bottom of the board

Also mornsun-power has some EFD15 cores that they claim they can output 10W,
https://www.mornsun-power.com/html/product/AC-DC-Transformer.htmlSo how can I get better efficiency? and calculate the core properties and calculate the transformer correctly? what am I doing wrong?