Problem with SMPS design for high power ultrasonic


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  1. #1
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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?

  2. #2
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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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  3. #3
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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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