I have simulated an open loop boost converter using LM3481 average model, given by texas instruments and I got a very strange bode plot (More precisely, strage phase response), please can you tell me why I did not get the general forme response?

Here is the circuit simulated in TINA TI simulator: enter image description here

Expected forme of the phase response enter image description here

  • \$\begingroup\$ please can anyone knows what I have missed ? You haven't told us what you're expecting to see :) \$\endgroup\$ – KingDuken Sep 20 '19 at 3:58
  • \$\begingroup\$ I have added what I'm expecting from my simulation, If you notice, as the frequency increases, the phase decreases. In my simulation as the frequency increases, the, the phase tends to 0°. \$\endgroup\$ – luxina pado Sep 20 '19 at 4:11
  • \$\begingroup\$ That's helpful, thank you. Have you figured out the appropriate transfer function for this circuit? I think that could help you see how to plot the bode plot correctly. \$\endgroup\$ – KingDuken Sep 20 '19 at 4:22
  • \$\begingroup\$ I did not find it in the datasheet, but it says that it is a current mode boost converter controller, so I'm expecting the device to behave like a standard current mode controller, this is why i give you the standard response of current mode controller. The link bellow helps you understand the transfer function of this kinf of controllers: ti.com/lit/an/slva452/slva452.pdf \$\endgroup\$ – luxina pado Sep 20 '19 at 4:36
  • \$\begingroup\$ If you are operating that converter in continuous conduction mode (CCM), then you should see a the effect of the right-half-plane zero bringing the phase further down. Unless it is located at high frequency and the converter is in light CCM? Also, unless heavy internal compensation, sub-harmonic poles effects should show up at \$F_{sw}/2\$ as the second plot shows, stressing phase lag at this point. \$\endgroup\$ – Verbal Kint Sep 20 '19 at 6:36

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