0
\$\begingroup\$

I made a simulation of a closed-loop buck converter with simplis.

the basic parameters of the open-loop circuit are listed below:

\$V_g=12V,V_{out}=5V\$

\$D=0.52\$

\$C=100\mu F,ESR=5m\Omega; L=30\mu H,ESR=5m\Omega\$

Then I made the compensation of the open-loop circuit.

The closed-loop circuit is this: enter image description here I derived the both the ideal tf of the buck converter and the closed-loop tf.

Using matlab, I got the ideal closed-loop bode like this enter image description here

It is weird that when I build up the compensation circuit in simplis, the bode plot totally went wrong.

Neither the gain graph nor the phase graph suits the ideal bode plot of matlab.

enter image description here

However the transient result looks good.

enter image description here

I think the derivation and the result of matlab are correct and there should be some mistakes in simplis simulation. I really appreciate your help if you can explain it for me.

\$\endgroup\$
2
  • 1
    \$\begingroup\$ You are plotting the open-loop gain of a converter operated in closed-loop conditions. Regarding SIMPLIS, I would not place the stimulus source where you installed it. Please try inserting it in series above \$R_4\$ as I did in the platforms that I described there. Also, are you sure a 5-V bias is enough to properly drive the IRF530 MOSFET? I always prefer to start with controlled switches, check that it works, then complicate later on. \$\endgroup\$
    – Verbal Kint
    Commented Apr 4, 2021 at 15:58
  • \$\begingroup\$ Finally, when you graph magnitude and phase responses, I've found that having symmetrical scale ends makes it easier to read and interpret (+/- 50 dB and +/- 180° for instance). If you plot the phase and the magnitude on the same chart, then having them share a common 0 reference makes phase and gain margins easier to extract in my opinion. \$\endgroup\$
    – Verbal Kint
    Commented Apr 4, 2021 at 16:01

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.