By the way, the supply current to the transformer with no load is around 4mA, I've just noticed it climbs too but not as fast, have attached an output wave form after the input has climbed to approx 500mA.
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By the way, the supply current to the transformer with no load is around 4mA, I've just noticed it climbs too but not as fast, have attached an output wave form after the input has climbed to approx 500mA.
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It may be bad ground, no decoupling capacitor on power lines.
If you use a E-I transformenr,a little gap may help avoid saturation. Put a thin paper in between.
HTH,
Ioannis
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Thx - I'll try gapping the ferrite core a little - one thing I cant get my brain around tho is: How come a slight imbalance in drive can cause the core to saturate when push pulling, but it's ok to just switch DC pulses through a transformer and only drive it in one direction without it saturating?
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I've found this in the data sheets - my core is N97 operating at 25kHz tho the data sheet says:
"Large E/ETD, RM/PM cores made of N27, N97, N87 (with large core cross sections (Ae ≥250 mm2), on account of eddy-current losses N87 must be used even where f <100 kHz)"
Is this likely to be my problem? I cannot find an N87 core in my transformer size. Is it worth me getting a different size bobbin and starting from scratch?
Gapping and decoupling didnt seem to help much, is the topology with half bridge suppling one side of transformer and a capacitive divider on the other (as attached) likely to be easier for me to accomplish successfully?
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Do you have any means to compare the two transistors used in the circuit?
The idea of two capacitors as voltage divider in my opinion is very bad.
In general I avoid this kind of circuits, as the parts should be identical (as much as possible).
Sorry I cannot help any more.
Ioannis
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