Swathika Posted May 29, 2007 Report Share Posted May 29, 2007 In a SMPS design Ferrite Transformer Inductance is in what way related to SMPS output Power?How?Why? Quote Link to comment Share on other sites More sharing options...
AN920 Posted May 29, 2007 Report Share Posted May 29, 2007 Power in SMPS will be mainly limited by:Effective core areaSwitching frequencyCore loss at switching frequency vs peak flux swingCopper lossSwitching losses of the active deviceRectifier losses Quote Link to comment Share on other sites More sharing options...
indulis Posted May 31, 2007 Report Share Posted May 31, 2007 Don't forget the winding window area as a factor... Quote Link to comment Share on other sites More sharing options...
AN920 Posted May 31, 2007 Report Share Posted May 31, 2007 Because in practical situations only about 40% of the core window area is filled with copper. The rest is used up by the bobbin and insulation. Winding packing factor is normally considered a constant with, Ku ~ 0.4 Quote Link to comment Share on other sites More sharing options...
indulis Posted June 1, 2007 Report Share Posted June 1, 2007 Is it really that low?If you are doing a planar, or it's a wire wound non-isolated application, seems that that constant would be unusable. On the bench right now I have a interleaved flyback (current mode) 1/4 brick running at 250KHz with planar's (16 layer PCB with 3oz Cu) that uses RM6 N92 cores (8mil gap) and I'm getting a bit over 120W out if it with efficiencies in the low 90's. While I haven't calculated it out, I don't think it would be in the 40% range. Quote Link to comment Share on other sites More sharing options...
AN920 Posted June 1, 2007 Report Share Posted June 1, 2007 Typical Ku factors for standard converters:Forward 0.4Full and 1/2 bridge 0.4Push Pull w CT 0.4 ~ 0.5 (0.5 for the single ended secondary output)This sounds low but due to the shape of standard round copper wire, if you do the math only about 78% of the available window area can be filled. Take the insulation of the wire, any other layer insulation, mandatory creepage distances, RFI and safety screens. Add the bobbin and you can start to see the picture.Construction with foil windings will also improve KuPlaner designs may have slightly higher factors. Quote Link to comment Share on other sites More sharing options...
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