What aboutthere is no single formula to cover all situations
Sure, that is, by definition, equal to power dissipation. But that's only useful if you measure the waveforms in a real circuit (extremely difficult if your switching times are fast. Any skew between Ids and Vds waveforms will cause large errors), or a simulation (which requires an excellent device and parasitics model to give useful results).What about
Average of (V_ds(t) * I_d(t))
For the "output" side.
You may do the same with the gate (input) side.
Losses incurred during reverse recovery of the body diode of the freewheeling device.
The dynamics of this process are determined by the properties of the body diode, turn-on of the control MOSFET and the stray inductance in the triangle: forward MOSFET, freewheeling MOSFET and input capacitor (depicted as LSTRAY in Figure 2). A body diode is an inherently slow device and a substantial amount of reverse charge must be delivered during the recovery process (see the big current spike on the Figure 3). This charge is delivered under the voltage approximately equal to VIN and results in a large amount of power loss. It also extends the duration of the turn-on transition of the forward mosfet causing further degradation in efficiency. The calculation of these losses is difficult to conduct precisely because of poorly characterized properties of the body diode in the manufacturer's data. They also vary significantly with the temperature, forward current and the duration of the recovery process.
An error introduced by reverse recovery is usually the biggest factor behind inaccuracy of the overall prediction of the efficiency. It is however necessary to estimate the magnitude of this source of losses because of its significant contribution.
It's about loss. But capacitive currents are no loss (at first). The energy is stored in the capacitors.how do account for capacitive currents in Vds? ,
I'd say they perfectly do. Power_loss (heat) = power_input - power_output. .. is true for every electric device.external measurements cannot give accurate loss
I interpreted this "cover all situations" as "total Mosfet loss".there is no single formula to cover all situations
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