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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

    Ok. It makes sense.

    Allow me to put my thoughts here regarding this issues that I am trying to address.

    (I don't know if you are familiar with DC-DC Converter operation and theory) 

    As I said before, maybe not in a clear way, something that had confused me (after reading the SMPS: Spice Simulations and Practical Designs (from Basso) as well as the book Power Electronics Principles (from Erickson) and then go after a solution to get what I am trying to do) was the fact that because we are in the presence of a time-arying circuit with non-linear components (Switches), the authors from the books I referred had modeled the switches in such a way so that they could become linear and from there be inserted into the overall converter to be simulated. The PWM is another example, it is another non linear circuit, modeled too in a way to become linear and so on.

    With all this done, the circuit becomes time invariant and linear. In this way we can simulate the circuit without problems, "break" the loop and see the stability and so on.

    Now in my searchs I found this solution PSS + PSTB that we're talking in here.

    So when you say that the system is linearized around the time-varying operating point found by the PSS analysis, we can say this is similar/equivalent to insert that linear model that I talked just now into the circuit? Or it doesn't have nothing to do with that?

    Can I ask you to elaborate what means "performed for the zero sideband (the frequencies around DC)"?

    Thanks for you time!

     

    Regards. 

Reply
  • Pyroblast

    Ok. It makes sense.

    Allow me to put my thoughts here regarding this issues that I am trying to address.

    (I don't know if you are familiar with DC-DC Converter operation and theory) 

    As I said before, maybe not in a clear way, something that had confused me (after reading the SMPS: Spice Simulations and Practical Designs (from Basso) as well as the book Power Electronics Principles (from Erickson) and then go after a solution to get what I am trying to do) was the fact that because we are in the presence of a time-arying circuit with non-linear components (Switches), the authors from the books I referred had modeled the switches in such a way so that they could become linear and from there be inserted into the overall converter to be simulated. The PWM is another example, it is another non linear circuit, modeled too in a way to become linear and so on.

    With all this done, the circuit becomes time invariant and linear. In this way we can simulate the circuit without problems, "break" the loop and see the stability and so on.

    Now in my searchs I found this solution PSS + PSTB that we're talking in here.

    So when you say that the system is linearized around the time-varying operating point found by the PSS analysis, we can say this is similar/equivalent to insert that linear model that I talked just now into the circuit? Or it doesn't have nothing to do with that?

    Can I ask you to elaborate what means "performed for the zero sideband (the frequencies around DC)"?

    Thanks for you time!

     

    Regards. 

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