Sunday, March 6, 2011

HW 7 problem 2 steady state

HW 7 problem 2a seems pretty straightforward in nature, but I am having a difficult time with the number of unknowns in the problem. It seems like the problem does not give us R, R1, or V. Because of this, I am having trouble finding equations for D1 and D2 that are not dependent on these unknown quantities. I have solved for I(D1,D2) as the average value of the inductor current, and I have the buck equation for M(Re, R) and Re(D) in DCM from the book, but I am still having trouble piecing it together with these unknowns. Could anyone give me a hint on what I am missing?
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2 comments:

  1. KYiMarch 6, 2011 at 9:24 PM

    Vref is given. So you can get V. Then M, Re etc.

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  2. AudreyMarch 7, 2011 at 7:00 PM

    Thanks for the response.

    This is what was confusing me: VRef is the input to the op amp, which tells us that the other side of the ideal op amp is the same voltage, but there might be voltage drop across R1.

    I think I have convinced myself that since I=V/R, there is only small signal ripple current going through the feedback loop and therefore the average voltage across R1 for the DC model would be 0.

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