Discussion in 'Homework Help' started by bcassidy9, Jun 12, 2013.

  1. bcassidy9

    Thread Starter New Member

    Nov 27, 2012
    Program: LTspice
    Purpose: Work on compensation feedback networks

    I am using a simple LC circuit to work on feedback compensation. I chose the corner to be at 1000 Hz. I am using a type 3 compensator fed back into a Voltage Controlled Voltage Source. I chose to design the new crossover frequency to be 9000 Hz. Attached is the .asc file of my design. I am running into some trouble with the crossover frequency NOT being where I want it to be and there being a ton of Q introduced when the circuit decides to fall off. I am not too worried about the Q at this point; however, I do want to know why the corner is so far out? Right now it rolls off at about 90000 Hz, which is a decade above where I want it to be. If I change the multiplier from 10 to 1 on the VCVS, it comes back down to approximately 10 kHz. What am I missing here? This happens with both a type 2 and type 3 compensator. The peak seems to change with respect to the RC zero frequency of the capacitor in the LC network.

    Fundamentally I am missing something huge here. I designed the type 3 compensator correctly and have tried several designs. However, I cannot fix this problem.

    I am not looking for a solution necesarilly. If you have one, great. If not, any guidance or suggestions will be appreciated. This is my first post, so if I messed something up, sorry! haha.

    Thanks for any help!