Tuesday, April 12, 2011

HW10 Prob 1

I'm working on finding the range for Vc in problem one. I found the range of duty cycle using V/Vg=1/D' and used it as a reference for finding Vc. Looking at the mid-band gain I come up with Vm(t)=(R2/R1)Vrf, with Vrf=Rf*I. At turn-off Vm(t) should be at maximum. I used R2=(R1/Vrf)*Vm(t) to find R2. I get R2=350K. This results in a range of .286 to .5 for Vc, using Vc=(10R1/R2)*Vm(t), but it ends up being a lot of mid-band gain for the compensator, ~30dB. I'm not confident in this approach. I'm using Vrf=Rf*I=.05V which is true at steady state but it doesn't account for the inductor current ripple. I haven't had a chance to simulate it yet. Is my lack of confidence in this approach warranted?
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2 comments:

  1. Nitish AgrawalApril 13, 2011 at 11:38 AM

    Hello,

    I am not following your approach. You can find Vc (steady state values) by regarding the capacitors Cp and Cz open.....then you will be left with two resistors (R1 and 10R1) in series, with a potential of -IL*Rf on the end of R1 that is connected to Rf and Vc on the end of 10R1 (with a potential of zero between R1 and 10R1). Since you have calculated the duty cycles for the two input voltages, you can calculate the (steady state) IL for those two cases as well. Now you have everything to solve for Vc.
    Nitish

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  2. wrichApril 13, 2011 at 8:18 PM

    Thanks Nitish. I think I have it worked out now.

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