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AC Analysis of COT Control of Buck Converter

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Hi,

I would like to learn how to obtain the Control-to-Output Frequency Response of a Contant On-Time (COT) Control of a Buck Converter using the Multitone Analysis tool. The parameters of the Converter are as follows:

  • L = 300e-9 H
  • C = 56e-6 F/560
  • DCR = 0 Ohm
  • ESR = 6e-3 Ohm
  • R = 120e-3 Ohm
  • Ton = 0.33e-6 s
  • Fsw = 300e3 Hz;

The COT Controller was implemented using FSM. I've applied a perturbation signal to the reference input (Vref) and measured the reponse. Then using the Multitone Analysis Tool, used the following parameters

  • Initial simulation period: 1e-4 (s)
  • Frequency range: [1e3 150e3]
  • Amplitude: 1e-3
  • Perturbation: vref'
  • Response: vo'

The image below ilustrates the schematic of the regulator.

The image below ilustrates the implementation of the COT Control using FSM.

The ideia is to get the Control-to-Output Transfer Function according to what was obtained in the following paper "New Modeling Approach and Equivalent Circuit Representation for Current-Mode Control", by Jian Li and Fred. C. Lee.

When I try to obtain the same results using the Multitone Analysis, this is what I get.

 

Thanks in advance.
 

asked Dec 13, 2022 by luizgsmartins (12 points)
I see that the plots have a similar behavior as the ones from the paper (we can probably help you to get a "cleaner" Bode plot result), but is your main question the gain magnitude? Are you sure you are comparing the circuit parameters exactly to the model proposed in the paper?

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