Bode plot analysis of buck converter

Thread Starter


Joined Apr 26, 2020
Hey guys,
I'm currently designing a buck converter with a type-3 voltage-controlled compensator. I am simulating it in ltspice.
My buck takes an input of 12V and outputs a 1.8V. I've done the simulation. I've also ran an AC analysis to see the bode plot of the buck converter in open loop(without the converter).
My problem is the following : I am not really sure what I should be looking at in the bode plot to see/analyse the response of my buck converter in gain and phase.
Would you guys have some hints for me ? I put the results in the post and the simulation file.
Thank you very much !



Joined Mar 14, 2008
To do the Bode plot you need to include the compensation circuit and use a linear gain block for the PWM controller in the loop.
What you are simulating makes little sense.


Joined Feb 24, 2006
It does make sense to characterize the open loop response to know how to specify the compensator. This method is described in the LTspice help file and the new 17.1.6 Beta has the FRA element which is new to me, but allegedly performs a similar function. I have not had much time to play with it.
It takes about 2 minutes to run