Sunday, March 17, 2013

Fig 12.21 and 12.22

Hi All,

I am struggling a little with Figures 12.21 and 12.22.  In lecture 23 we were told that the -D^2/R value of Figure 12.21 was wrong (inverse)... I don't quite follow why...

from 12.53...
-v1hat*I1/V1 term... I1 = D*I2 and I2 = V2/R, so I1 = D*V2/R which results in (D*V2)/(R*V1), V2/V1 = D, so -v1hat*I1/V1 = -v1hat*D^2/R... which is what I think it shows on Fig 12.21

I am running into a similar situation on Fig 12.22...

After perturbation and linearization I get I2*v2hat + V2*i2hat = V1*ichat + Ic*v1hat

which results in a -v2hat*I2/V2 term... since I2 = V/R, V2 = V and v2hat = vhat, I get -vhat/R for the term. It looks like Figure 12.22 shows a +R term for this (Inverse and opposing sign of the equation I get)...

I don't quite follow why both are inverse from what the equations show and why I have a negative term in the Figure 12.22 equation.  Everything else matches from what I got...

Can anyone help out to where I went wrong?

Thanks!

Thursday, March 7, 2013

Table 11.4

Why is the f2 frequency different when computed using table 11.4 vs using the formula f2 = fs/(pi*D2)

Hmwk 7 problem 2 part b

"Plot (by hand) magnitude and phase Bode plots of the loop gain T for the two extreme load current values, and determine the cross over frequency fc and the phase margin in both cases. "

I assume that this is the loop gain for the entire feedback loop and not just the compensator. Is this the assumption others have made as well?

Wednesday, March 6, 2013

Hw7 pblm1

I have a question regarding the magnetizing inductance of the transformer. In simulation do we have to specify the value of Lm twice once for transformer model and once for the CCM-DCM2 model?

Tuesday, March 5, 2013

HW7 Variables Question

Is the omission of V and R intentional in problem 2 of HW7?

DCM buck compensator circuits

Hello:

Are we supposed to design two compensators (one for Imin and one for Imax); or should we design only one circuit that meets the requirements for all values of current?

Thanks,
Alex

Monday, March 4, 2013

HW7 P1 b plot questions

I have the following questions setting up spice plots:

1.  What is the syntax which causes spice to generate three plots on a single figure where the first plot employs Vd = x, R1 = xx, second employs Vd = y, R1 = yy, and the third employs Vd = z, R1 = zz?

I tried:
.param Vd = {Vd}
.step PARAM Vd LIST x y z

.param R1 =  {R1}
.step PARAM R1 LIST 1 2 3

but I don't see multiple plots

2.  How does one remove the black back-ground in the splice plots?

Thank you,
CD

Sunday, March 3, 2013

HW7 P1a

I am trying to verify my answers to part (a) in LTspice. I am having trouble with the CCM-DCM 2 model block, meaning I can't plot any reasonable output voltages. An astronomical voltage is being measured but not plotted. I only know this from putting the "probe" over the output and then looking in the lower left corner of the schematic window where there is some information displayed during a simulation. Using the HW4 CCM3 block, I have been able to check what I believe to be the CCM modes, but I'm at a loss for the CCM-DCM 2 block. Anyone else having problems?
- KT

Expression for D2 in HW6 Solution for 11-1-d

Hello:

Where does the expression for D2 (D2 = n*(Vg/V)*D) come from in the posted solution for 11-1-d?

Thanks

Saturday, March 2, 2013

Midterm Exam Process

Professor Maksimovic,

The calendar on the course Web site says the the Midterm exam will be handed out in class on Friday, 8 March 2013.  Is this true, or will the exam be made available through D2L?

The calendar also says that the exam is due at the beginning of class on Friday, 15 March.  Will we be turning in our midterm exam solutions on paper on the 15th, or will we be submitting our exam solutions through D2L?

Thank you.