Yes, I agree with Alan and fail completely to see why the driver
should have any effect on the ringing. It just cannot.
As I keep saying, such ringing is commonplace in SMPSUs and is due
to leakage inductance in the transformer. I don't like torroids as
they don't allow you to enclose the winding nearly as much as as ETD or pot
core type of construction does and I'm sure contribute more leakage L than
more enclosed core types. There is more wire facing outer-space
than there is facing ferrite when you have windings of only a couple or
turns. .
But everyone else just seems to have accepted torroids are the best
thing, so carry on. Someone must have originally said they're the
way forward but I'd love to know why no one just uses standard SMPSU
cores.
I'll just tootle along with switching power amps built with tank circuits
and only then into a transformer, and let everyone else go their own
way. It just seems such a simple and obvious route, I cannot
understand the need to generate a square wave, force it though an unwilling
transformer then use a complicated low pass filter to clean up.
The only LF amp I've built where push-pull FETs go straight into a
transformer is a linear (well, almost linear) one - just to see if it could be
done. About 40 - 50 Watts from a 28V supply, 60 - 70 watts
saturated with scope for improving it with better FETs
http://www.g4jnt.com/Linear_LF_PA3.pdf .
The output transformer for that was just an RM10 sized pot core of F44
material. I suspect that if pushed hard into saturation, and
the feedback CR removed from each drain-gate it would also show ringing on the
edges.
But there's little call for linear amps on the LF bands.
Andy G4JNT
