# bode plot of LM3481 as boost converter

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:

Expected forme of the phase response

• please can anyone knows what I have missed ? You haven't told us what you're expecting to see :) – KingDuken Sep 20 '19 at 3:58
• 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°. – luxina pado Sep 20 '19 at 4:11
• 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. – KingDuken Sep 20 '19 at 4:22
• 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 – luxina pado Sep 20 '19 at 4:36
• 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. – Verbal Kint Sep 20 '19 at 6:36