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Help needed: how to simulate PWM controller system?

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MicroE

MicroE

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we do ac analysis when we elvuate the frequency response of an opamp. However, for the pwm controller system, how could we do the same analysis. I am urgently needing your kind help, thanks!
 

Hi
See **broken link removed**
I modeled the ti's tps54310 using Ben-Yaakov's theory.

YNHE
 

ynhe, thank you very much.

However, I am not requesting a model or tool. I need the priciple and know how to do such a simulation. As I have already had the total transistor level circuits. I wanna know if the system is stable.

Any kind members could help me?
 

Hi
I know your want.
There are two type of SMPS models,one is switching models and another is average models.
Switching models will exhibit the behavior of an electrical circuit exactly as if it were built on a breadboard with all of its nonlinearities.
You now have is switching model.
But SMPS circuits usually operate at high frequencies and have response times on the order of milliseconds,analysis times may be very long. Furthermore, it is practically impossible to evaluate the AC transfer function of the simulated circuit due to the switch.
Average models do not contain the switching components.
They contain a unique state equation which describes
the average behavior of the system.
So in order to analysis the system stability,you must first build the average model of your pwm controler.
I SUGGEST YOU STUDY MANY PAPER ABOUT THESE.

YNHE
 

ynhe said:
Hi
I know your want.
There are two type of SMPS models,one is switching models and another is average models.
Switching models will exhibit the behavior of an electrical circuit exactly as if it were built on a breadboard with all of its nonlinearities.
You now have is switching model.
But SMPS circuits usually operate at high frequencies and have response times on the order of milliseconds,analysis times may be very long. Furthermore, it is practically impossible to evaluate the AC transfer function of the simulated circuit due to the switch.
Average models do not contain the switching components.
They contain a unique state equation which describes
the average behavior of the system.
So in order to analysis the system stability,you must first build the average model of your pwm controler.
I SUGGEST YOU STUDY MANY PAPER ABOUT THESE.

YNHE
Click to expand...

Thanks a lot!
Could you offer me some beginnning papers on this topic?

Regards,
MicroE
 

if u want to simulate frequency responce of a PWM ganerator specially with feed back like those used in SMPS it is simple:
open the loop and add a small signal AC source to your reference DC voltage and use transient simulation, then after settling time (when the response of the circuit is in steady state) use FFT to find out the amplitude and the phase o the first harmonic of the input frequency, in this way u can find the bode plot of the loop ven though the pwm is nonlinear!
Remember that it is small signall analysis not large signal one.
by this method stability analysis of SMPS are possible even when the sampling frequency to loop bandwidth ratio is not very large!

BEST!
 

I hear the AC analysis of SMPS only be done by convert the switch mode to linear mode. It can be realized by macromodeling. But we must to determine the main pole and zero point. It is important to stability analysis.
 

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