Am I missing a 'Hidden' ESR in LTSpice XVII Capacitor/Inductor?

FHA_LLC_Deviation.asc

Dear all,

I am new to this forum, so hello to all of you! I am also relatively new to LTSpice, so this might even be an easy question for you to answer ;) 

I am currently working on an LLC converter, and I'm trying to verify my analytical calculations of the First Harmonic Approximation of the LLC in Maple with a FHA model of the LLC in LTSpice XVII.
This all works fine, however I am encountering one abnormality:

I am exciting the LLC at it's series resonant frequency of fr=141366 Hz, calculated by fr=1/(2*pi*sqrt(L1*C1)). This, in theory, should lead to the input voltage of Vin appearing across R1/L2 as well, since the series combination of L1 and C1 are acting as a short at their resonant frequency. However: I am losing around 4V pk-2-pk when comparing Vout with Vin. I have already set all ESR/EPR/ESI/ESC to 0 in the capacitor model and Series&Parallel resistance and Parallel Capacitance to 0 in the Inductor models.

Question: Am I missing any possibility of a 'hidden' series resistance here? Or how else can this deviation be explained?



Changed title to include a questionmark
[edited by: Bram_NL at 8:41 AM (GMT -5) on 17 Jan 2021]
Parents
  • +1
    •  Analog Employees 
    on Jan 18, 2021 5:54 AM 1 month ago

    Hi, 

    There is no hidden series resistance from the passive components on LTSpice.

    The difference in amplitude between the input and the output is probably due to the accuracy of your simulation. 

    You can modify it through the following steps:

    1. Go to Tools>Control Panel>SPICE and set the Reltol to a lower value. i.e, 0.00001. Lower value means higher accuracy and slower simulation.

    2. put a .op command ".options plotwinsize=0" (without the apostrophe)

    Regards, 

    Fritz 

Reply
  • +1
    •  Analog Employees 
    on Jan 18, 2021 5:54 AM 1 month ago

    Hi, 

    There is no hidden series resistance from the passive components on LTSpice.

    The difference in amplitude between the input and the output is probably due to the accuracy of your simulation. 

    You can modify it through the following steps:

    1. Go to Tools>Control Panel>SPICE and set the Reltol to a lower value. i.e, 0.00001. Lower value means higher accuracy and slower simulation.

    2. put a .op command ".options plotwinsize=0" (without the apostrophe)

    Regards, 

    Fritz 

Children