Stats

  • Locked Locked
  • Replies 5
  • Subscribers 125
  • Views 15327
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

A few questions regarding using PSS for rectifier design

MenghanSun

Dear all,

I'm using PSS for rectifier simulation and try to look at the voltage and currents in steady state. I'm trying to improve the accuracy of the PSS and try to get the same results as in the transient simulation (after it settled).

Currently, I use the Harmonic Balance mode. However, I heard Shooting Newton is better as it is only a wrapper for transient simulation. But, personally, I find HB to be more stable. From reading the user manual, when the over_sampling factor is set to be very big, the accuracy is very high. But how big should we set to this over_sampling factor to be? The higher, the better? Also, is there any additional way to improve the accuracy of the pss simulation? max_iters?

Also, does PSS support multi-thread? How to activate this?

I found PSS HB sometimes giving the correct results (i.e. the same as transient), other times not giving the correct result. Is this because I'm not setting the convergence parameters properly?

I know the port element in cadence only provides power in reference to 50 Ohm. Could you please recommend a solution if we have to use a port that has complex impedance? For example, a rectifier driven by custom antenna whose impedance conjugatively matched to the rectifier.

I use mmsim14 + ic616.

Thank you very much,

Menghan

Parents
  • Andrew Beckett

    Menghan,

    I suspect you would  be better off contacting customer support - it's hard to answer all your questions particularly without knowing quite what your circuit looks like. Some broad answers (to some of the questions):

    1. I'm not sure why you think HB is "more stable". If the circuit is a highly nonlinear circuit (or is a switching circuit) then generally shooting is preferable to harmonic balance, because it naturally follows sharp edges rather than relying on the solution being accurately found by specifying enough harmonics. With shooting the number of harmonics doesn't (significantly) affect the accuracy, whereas with harmonic balance the number of harmonics strongly affects the accuracy.
    2. The oversampling factor is a way to increase the number of points in the period where the frequency domain solution is converted back into the time domain. This can increase the accuracy when you have sharp transitions in the waveform and is not as expensive as increasing the number of harmonics. More harmonics increases the size of the solution, but oversample of 2 (say) means that  you are sampling at twice the number of points you would have got by the harmonics alone (2*harms+1). You still need enough harmonics to be able to reasonably represent the solution though. Typically I would use (if needed) oversample of 2 or 4 but rarely much higher than that. I suggest you ensure you have a good understanding of this rather than throwing random values at the problem (that's a good way of slowing down the simulation with little benefit)
    3. maxiters is unlikely to improve accuracy. Most of the time I leave this alone.
    4. The main way to improve accuracy is the errpreset setting, and then tightening reltol (a little further) if needed. For harmonic balance, the number of harmonics is also very important for accuracy.
    5. multithreading is supported for PSS (shooting and harmonic balance). You have to enable APS for this (on the Setup->High Performance form) and you can control the number of threads.
    6. I have no way of knowing why you're not getting the correct results - this is why you should contact customer support.
    7. You asked earlier about the port element - you don't have to use the port element - you can use vsource/isource too. Also, the port element can provide power with reference to whatever impedance you like. You can specify a complex impedance (when using harmonic balance) - there's a "harmonic port" option which allows you to specify different complex impedances at different harmonics. This can't be done in the time domain (shooting) because it's not physical - the impedance can't be discrete complex values at different impedances.

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    Menghan,

    I suspect you would  be better off contacting customer support - it's hard to answer all your questions particularly without knowing quite what your circuit looks like. Some broad answers (to some of the questions):

    1. I'm not sure why you think HB is "more stable". If the circuit is a highly nonlinear circuit (or is a switching circuit) then generally shooting is preferable to harmonic balance, because it naturally follows sharp edges rather than relying on the solution being accurately found by specifying enough harmonics. With shooting the number of harmonics doesn't (significantly) affect the accuracy, whereas with harmonic balance the number of harmonics strongly affects the accuracy.
    2. The oversampling factor is a way to increase the number of points in the period where the frequency domain solution is converted back into the time domain. This can increase the accuracy when you have sharp transitions in the waveform and is not as expensive as increasing the number of harmonics. More harmonics increases the size of the solution, but oversample of 2 (say) means that  you are sampling at twice the number of points you would have got by the harmonics alone (2*harms+1). You still need enough harmonics to be able to reasonably represent the solution though. Typically I would use (if needed) oversample of 2 or 4 but rarely much higher than that. I suggest you ensure you have a good understanding of this rather than throwing random values at the problem (that's a good way of slowing down the simulation with little benefit)
    3. maxiters is unlikely to improve accuracy. Most of the time I leave this alone.
    4. The main way to improve accuracy is the errpreset setting, and then tightening reltol (a little further) if needed. For harmonic balance, the number of harmonics is also very important for accuracy.
    5. multithreading is supported for PSS (shooting and harmonic balance). You have to enable APS for this (on the Setup->High Performance form) and you can control the number of threads.
    6. I have no way of knowing why you're not getting the correct results - this is why you should contact customer support.
    7. You asked earlier about the port element - you don't have to use the port element - you can use vsource/isource too. Also, the port element can provide power with reference to whatever impedance you like. You can specify a complex impedance (when using harmonic balance) - there's a "harmonic port" option which allows you to specify different complex impedances at different harmonics. This can't be done in the time domain (shooting) because it's not physical - the impedance can't be discrete complex values at different impedances.

    Regards,

    Andrew.

Children
No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.