I actually would like some advice regarding the flyback transformer design. Perhaps this enquiry can be passed on to someone with expertise in this area.
I had wound two transformers on RM10 cores with turns ratio of 34:4:7. One transformer worked extremely well and the other gave results of more than 2% less efficient. I thought that I had wound these identically and they had the same inductance and leakage. I then realised that I had wound the secondaries in opposite directions which I thought would not matter because I had phased the wings correctly anyway.
As a last resort, I unwound the worst transformer and rewound it to be identical with the better performing transformer. this solved the discrepancy and both transformers work well BUT, the secondaries are in fact wound in the OPPOSITE DIRECTION to the primaries. When wound in the same direction the performance is not as good.
At 30V/2.5A output, before rewinding, one unit had less than 90% efficiency and the other 92% efficiency with a mains input of 240VAC. After rewinding, both units perform at 92% efficiency.
I must add that this is using synchronous rectifiers in the ground side.
Our transformer supplier cannot explain this so I am trying to find out if there is something more to this and I thought someone at T.I. may help or give me a lead.
