Should have written, instead of "losses will be mostly resistive" it ought to be "inductor losses will be mostly resistive" since gate charge losses CAN be significant.
Jim Wagner
Oregon Research Electronics
On May 23, 2014, at 12:54 PM, Jim Wagner
wagnejam99@... [LTspice] wrote:
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Those voltage dependent FET capacitances are modeled well, if a good model is supplied, For an external FET switcher, that is up to you.
The switching loss estimate is as good as your model. For example, if the inductor stays well away from saturation, then the losses there will be mostly resistive. If you have a reasonable series resistance in that model, then its good. But, if it is driven into saturation and you do not have a model that includes saturation, then the loss number will be overly optimistic, maybe by a lot.
Jim Wagner
Oregon Research Electronics
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Hello,
LTspice calculates a switching loss of 1.07W in the FET of the buckboost smps that I have uploaded to the Temp Files area. "Buckboost SMPS _switching loss.asc".
How accurate is this to the real circuit? I mean, the switching Mosfet capacitances, especially Cgd, are voltage dependent, and this would need modelling to make the switching losses accurate. How accurate is it in LTspice?
