Transformer at 200KHz design and results

Hello,

I am trying to build a 200KHz transformer, with a primary voltage of pure sinusoidal 4V peak, and secondary voltage of 50 Volts peak into nominal load of 1K Ohm.

Because winding transformers is not easy (too fiddly and pain in the back side), I have built 4-5 to try out various approaches. I have so far used the EPCOS RM10, RM12 and RM14 sizes. On the firdst ones I made I have also forgotten how many turns I have wound :)

The table below shows the results:

Voff and Von is voltage off and on load. Reg % is the calculated regulation. N ratio is the ratio of turns.

As you can see the best regulation I can get is 20%. I am not sure if this is a good regulation or not. Ideally I would like max 5% regulation because the load varies, I do not want "spikes" when the load happens to be low.

One thing I am certain of, is what the turns ratio must be, but I have no idea how many turns are best.

I have tried to measure the coil inductances in case I can discover some relationship between coil inductance and regulation but again I am not sure how to measure coil inductance on a transformer.

So I guess my first question would be, can you make better than 20% regulation? How?

PS forgot to qualify: Von and Voff is voltage peak-to-peak. The input voltage is 8V peak to peak and the expected output voltage is 100V peak to peak.

According to my calculation if Xs = ~ 10 X Rl (10K) then Xs can be as low as 8mH - save some wire! How much does Vp change on/off load? - could be where the trouble is? Another thing that occurs to me is that if N1/N2 = 16, then L1/L2 = 16 X 16 (256). For your first coil Ls = 25.4, your Lp should be ~.1mH not .19. This would seem that you have some magnetic leakage as you need twice as much inductance.
Frank

When off load the primary is on +/-4 V as it is meant to be. When on load the primary curve shifts slightly, changes shape slightly, and becomes larger, maybe +/- 4.2V.

According to the calculation the Lp should be 0.1mH, but I am measuring it as 0.19 uH (micro not milli). So it seems I am not measuring it properly. What is the correct way to measure the two inductances?

Also does this regulation seem good, or can I get better with better design?

- - - Updated - - -

I re-wound the primary using multi-core wire (plenty of cores) and got ever so slightly better regulation, Voff:126.4, Von=106.8, reg = 18.35%, effective turns ratio (calculated with Voff vs Vprimary) = 15.8


I removed the ferrite core and measured the two coils. Lp = 0.400 uH and Ls = 41.65 uH. Still it does not match, because based on the second coil's inductance, the primary ought to be 0.17 uH not 0.4 uH.