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# Calculation of IGBT Switching Loss

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#### fethiyeli

##### Full Member level 4
Hi everyone, I am struggling to find IGBT switching loss for PFC circuit.

I have also measured Eon (peak) and Eoff (peak) by oscilloscope. I just want to make sure that both measured and calculated values are similar but they are not.

For measured values, I use below formulas. I multiply by 2 and divide by pi to average the losses. Is that correct ?

Psw,on = Eon * fsw * 2 / pi
Psw,off = Eoff * fsw * 2 / pi

For calculated values, I use Eon and Eoff from datasheet and scale it for the circuit requirements.

Sorry to be pinickity, but first we need to establish whether or not your boost diode is SiC or not?...so we can think about any reverse recovery contribution to switching loss.
I dont think the formulas can be right.....there needs to be an accounting for the actual emitter node transition time...(the "overlap" time).
Laszlo Balogh does a good guide on "high speed mosfet switching...."

When a Boost PFC FET switches ON...there is a short, initial interval where the entire power current flows through the full Vds(OFF) of the FET!...you need to calculate this interval, then calc the power for it.......Then there is the interval where vds is falling, and ids is rising (sorry to say "d" and "s" for an IGBT).....you need to calc the interval for that, and thence the power for it.

...and likewise for the Turn OFF.

You look at the Vbe(th) value..........there are two intervals where you have to calculate the time to go from Vbe(th) to the next step along the Vbe......(so its the time to charge the relevant junction capacitances)

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