Switching losses doesn't change when I change the switching frequency

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1

Hello!

I am doing a simulation on a simple buck-boost converter.(The picture of the circuit is attached) I want to see how will the switching losses change when I change the switching frequency. The first value and final value of the frequency doesn’t really matter, it can be 20kHz and 100kHz or 5kHz and 50kHz. I just want to observe how the frequency affects switching losses.

But the problem is, I get the similar result for all these frequencies! What am I missing? What setting should I change apart from the frequncy in the pulse generation block (which generates the pulse for the mosfets to switch)

Here I have attached the result when I set the switching frequency to 5e3 and then to 50e3 (5kHz and 50kHz) and as you can see they are pretty the same!

And should I use the Switch Loss Calculator block? or use the probe block and drag-and-drop the mosfets and diodes to it and connect it to the scope? I mean, how different are these two ways of calculating switching losses? which one is more accurate?

(I have used the thermal data of C3M0065090D from Wolfspeed for the mosfets and C3D02060A for the diodes)

Thank you in advance!

Samar

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2

With the Switch Loss Calculator, you are 1) monitoring both switching and conduction losses it appears and 2) averaging these values over 10us. You should isolate the switching losses only and also change your averaging interval to be 1/Fsw (it changes based on what Fsw value you choose).

As compared to using a standard Probe block, the Switch Loss Calculator has the built in averaging (whereas you otherwise have to add this averaging inline yourself using Filter blocks), and also provides the breakouts for turn-on and turn-off losses separately. But if you add averaging to the output of a Probe block that is looking at the switching losses of the device, you should see the same results as with the Switch Loss Calculator block looking at that same device and with the same averaging interval.