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DC-DC Converter/ Feedback/ Verilog-A

Pyroblast

Hi  dear fellows,

I am trying to design a DC-DC converter using Cadence/Spectre environment.

That said, what I want to do is to measure the feedback loop. I've been told that HSPICE has a simulation option that allows one to break the feedback loop and measure it. The person who told me that didn't knew if the same would be possible with spectre.

After searching around the web, I found a website where they were talking about the stb analysis. From what I've understood and read on the spectre manual this stb analysis allow:

"The loop-based and device-based algorithms are available in the Spectre circuit simulator for small-signal stability analysis. Both are based on the calculation of Bode’s return ratio. The analysis output are loop gain waveform, gain margin, and phase margin."

"Linearizes the circuit about the DC operating point and computes loop gain, gain margin, and phase margin for a specific feedback loop or an active device. The stability of the circuit can be determined from the loop gain waveform. The probe parameter must be specified to perform stability analysis."

On that website they did this analysis with a Single-ended Opamp simulation. To perform this analysis, a iprobe component was needed.

I haven't tried this yet.

 So what I'd like to ask is if someone here as used this kind of analysis and if it was successful.

Based on this, I was wondering if it is possible to do the same thing but in a feedback loop of a dc-dc converter? Break it on a particular part, block th AC signal and let the DC pass.

Taking the advantage of this post, I'd like to as anoter thing.

I don't know if some of you guys that are reading this post are familiar with DC-DC Converter. Picking the Basso's book, where he teaches how to simulate DC-DC Converters using PSPICE, he uses a switch model to model the power devices. He uses a transformer, current sources, etc.

It is possible to implement such models in Cadence? Transformers, current sources, etc.

Please feel free to comment, give an opinion, share experiences. If you can give some tips too I would appreciate.

Sorry for the long post.

Kind regards

 

EDIT: Can someone tell me where can I find some good Verilog-A models for comparator, ramp generator, PWM, etc?

Parents
  • Pyroblast

    Hi shawn,

    Thanks for your reply. I appreciate. 

     I've understood that, howeve I am afraid that you didn't got my point.

     If you notice, at certain part of my posts, I've written:

     "But, what if I want to get the bode plot only the converter itself (to see how the converter it behaves), not resorting to the transfer function (obtained for example through SSA) and then matlab, can I still use the PSS + PSTB analysis to do this?"

     Putting into another words, I want to  plot the bode plot of the converter without any kind of feedback loop.

     What is the kind of procedure if you want to label it like this, that people do? They get the transfer funcion of the converter then they go to MATLAB and plot the bode response of the converter. Then, based on that they design the controller. Isn't it?

    So, and if I don't want to go to the MATLAB environment can I plot the same converter bode plot (alone without the feedback loop) using cadence?

    Mr. Mark answered yes by using a  "pss + pac analysis" but "obviously need a source component with the parameter "PAC Magnitude" set (usually to 1).".

    Ok.

    Since I don't have yet the feedback part of the control designed, I want to know where I must put the source component? NOTE: I odn't even know if it's possible to do that, get the bode plot of the converter only without the feedback loop. But as Mr. Mark said it is, I hope that someone can answer me to this.

    I don't know if I am explaining myself clear. I think I am. But if not, please let me know that I will make a sketch on paper and put here a picture taken by my cellphone.

    The design is pretty simple. Is a sync buck converter like that on the presentation the Mark has posted. There is nothing special. Imagina that circuit but without the feedback loop.

     

    I am looking forward to hear from you.

    Regards. 

Reply
  • Pyroblast

    Hi shawn,

    Thanks for your reply. I appreciate. 

     I've understood that, howeve I am afraid that you didn't got my point.

     If you notice, at certain part of my posts, I've written:

     "But, what if I want to get the bode plot only the converter itself (to see how the converter it behaves), not resorting to the transfer function (obtained for example through SSA) and then matlab, can I still use the PSS + PSTB analysis to do this?"

     Putting into another words, I want to  plot the bode plot of the converter without any kind of feedback loop.

     What is the kind of procedure if you want to label it like this, that people do? They get the transfer funcion of the converter then they go to MATLAB and plot the bode response of the converter. Then, based on that they design the controller. Isn't it?

    So, and if I don't want to go to the MATLAB environment can I plot the same converter bode plot (alone without the feedback loop) using cadence?

    Mr. Mark answered yes by using a  "pss + pac analysis" but "obviously need a source component with the parameter "PAC Magnitude" set (usually to 1).".

    Ok.

    Since I don't have yet the feedback part of the control designed, I want to know where I must put the source component? NOTE: I odn't even know if it's possible to do that, get the bode plot of the converter only without the feedback loop. But as Mr. Mark said it is, I hope that someone can answer me to this.

    I don't know if I am explaining myself clear. I think I am. But if not, please let me know that I will make a sketch on paper and put here a picture taken by my cellphone.

    The design is pretty simple. Is a sync buck converter like that on the presentation the Mark has posted. There is nothing special. Imagina that circuit but without the feedback loop.

     

    I am looking forward to hear from you.

    Regards. 

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