HW6 #2 11.1 'd'

Has anyone found that Icrit is not a function of 'n', but only Vg, Re and D?

I have checked my work multiple times and can't find an error.  Having Icrit independent of 'n' seems a bit odd.

11.1 4)

Is anyone able to describe where equation 11.35 comes from?  There is no explanation in the book.  It appears to be simply given.  Not helpful when trying to solve 11.1 part 4.

HW6 Problem 1(b)

When finding Go, ix =0 implies that the opamp is taken out of the equations. What's left is a seemlingly simple circuit with vhat, R1, R2 and the feedback loop from vchat through C1 and R3. I'm trying to solve this circuit with mesh currents and the equations are getting very messy.

And I missing something that simplifies this circuit? Have I setup the circuit correctly? Thank you.

-Drew

Hw6 p1 a

Anyone else find that Spice simulations results of part a generate either a inverted pole or resistor in parallel at low frequencies (<100 Hz) resulting in a flattening of the inverted zero around 5dB?  Mathematically I can only derive the inverted zero.

LT Spice Printing / Scanning Issue

LT Spice creates plots with very thin lines and schematics with very thin wires and elements.  This results in poor scans that either "blotch out" from setting contrast too high, or using a setting other than 1-bit which results in large files.  Neither option seems acceptable.

Has anyone found a way to increase the line width / thickness in LT Spice plots and schematic prints so that reasonable prints & scans can be created?

HW5.3 Incorporating load resistance into model

Hi,

For HW5.3, I built the Simulink model of the boost converter using the structure as our first model of the buck converter. I compared the resulting ||ZD|| with the closed form solution on page 382 of the textbook, and they don't match. The textbook solution has the load resistor R in the solution. My model doesn't have this resistor because we model Iload directly.

Should my model include R directly or is it equivalent to model it using Iload=V/R?

Thanks.

-Drew

HW5 Sepic

Hello:

On the analysis for the zeros of the Sepic, it shows the step where the d^ voltage source divided by the d^ current source reduces down to -(D'/D)^2*R.  Why is the d^ voltage source treated as negative and thus the equivalent resistance is negative.

Thanks

IFilter_design_example.m Warning

Im running Matlab R2012a - student version. When I download and run IFilter_design_example.m I get this warning (at this point nothing has been modified its just as is out of the lecture website):


Warning: Ignoring all input names because of name conflicts.
> In warning at 26
  In DynamicSystem.DynamicSystem>DynamicSystem.plusInput at 1080
  In DynamicSystem.DynamicSystem>DynamicSystem.plusMetaData at 924
  In InputOutputModel.plus at 59
  In InputOutputModel.InputOutputModel>InputOutputModel.minus at 458
  In getZDZN at 66
  In IFilter_design_example at 34

Does anyone else see it? The plots and all look fine but I was curious coz it says "Ignoring all input names...".

HW 5 Prob 3 Simulink Boost Model for Zd & Zn

For the third problem, do we need to do exactly same as the example to design the filter? Since the equations for ZD and ZN are available, do we still need develop the Simulink model for boost to get the ZD and ZN? 

Interested in forming study group

Hello,

I am an off campus student working full time and I'm finding that the homeworks assigments are getting increasingly difficult. I was wondering if there are others like me that would be interested in forming a study group. My basic idea was the following:

1) Follow Dr. Maksimovic's advice and try and crank out the homework over the weekend and ask questions during office hours on Monday afternoon.
2) Get together for a homework study group session preferably Monday night. I live in Louisville, but I'm willing to travel to a convenient location.

If you are interested, drop me a line at: biz.drew@yahoo.com. Thank you.

-Drew

B4 calculation for Sepic

Hello:

When calculating b4 for the Sepic, why is the resistance that C2 sees equal to R?  It looks to me like R is in parallel to the series combination of the primary and secondary windings of the transformer.  Why are the series windings not considered a short circuit therefore giving Req= 0?

Thanks

Maybe I missed something, and if so I apologize...where is the solution to the SEPIC referred to in Problem 1 of HW#5?  Is this the solution from the previous HW#3?  The problem statement seems to indicate there's an attached solution which contains the error.

HW 5 P1b

In the SEPIC NEET problem at part (b) we are supposed to compare the magnitude and phase plots obtained from Spice simulation to the approximate results. Does this mean we need to turn in hand drawn Bode plots, or just compare our analytical corner frequencies and Q factors to the Spice results? Thanks.

CCM3 Simulation

Hello,

I'm trying to simulate the Flyback Converter in LTSpice for 10.4c. I've read on a different posts to use CCM3 from the switch.lib. CCM3 allows you to set a 1:n turns ratio, but how do I set up a magnetizing inductance? I found a way to create a transformer on LTSpice by coupling two inductors and using a SPICE directive called K-statement and setting the n = 1 in the CCM3 model. Would this approach work or does anyone know how to add Lm to CCM3?

Thanks for the help!
Claire

Overlaying Plots from Different Sims in LTSpice

For Problem 10.4, section 'c', we must verify that our input filter satisfies the conditions of section 'b'.

Verifying the attenuation of the filter over frequency to see gain at 200kHz is simple.  However to verify the impedance conditions, different AC sources and circuit schematics must be used to plot each of Zo, Zd and Zn (or am I wrong about this?).

Given three different sim schematics and simulation runs, how does one overlay a plot from each of three different sims onto one display window for relative comparison of results?

Is creating three independent plots the only way to view these impedances?  That would be extremely cheesy and I assume LT Spice isn't that poor a tool so this must be user error/ignorance.

Any assistance would be appreciated.

Thanks,
Colin

Attenuation calculation from Lecture 12 Example

Hello:

In the lecture 12 example for the cascaded filter design, you solved for ff1 by using the following equation:

(fs/ff1)^2 = attenuation.

How is this derived?  I do not see this in the book.

Can we use this equation in our homework problem 1 and 2 or is it specific to the cascaded Rf-Lb parallel form?

Thanks,
A Dub

Clarification on Filter

Hi All,

A silly question, but I want to make sure I am interpreting this properly.  When the problem asks for 100 dB of attenuation at the switching frequency (as in 10.4b), I interpret that as being 100 dB below the converter (in this case roughly -40 dB)... I don't need to be at -100 dB at fs do I?  That would be a gigantic capacitor...

HW4 problem 1A

Hello:

For this problem should we use the small-signal average switch model, or can we use a model similar to Fig 7.27?

Thanks,
Alex

HW 3 Prob 3b

Hi All,

I am wondering if anyone is running into the same issue that I am seeing.. when I gather my Gvd together, I get a normalish looking transfer function (with two poles) and an additional term that I got when doing superposition of the current source... so I am getting Gvd = 1/D'^2*[Gvo/(1 + s/Qwo + s/wo^2) + I_2*D'/D]... I don't know what to do with the I_2*D'/D term any ideas?  I am wondering if my equation should have more terms and be more complex like Zd is, but I am not seeing it... any help would be greatly appreciated.

additional material on circuit manipulation

In various examples and homework problems we're asked to manipulated sources and elements across the transformer or into other forms to make the analysis easier. Is there any material available to help better understand how to perform these manipulations?

Zn for Hmwk 3 prob 2

Given that we only have three impedance sources in our model, and we are replacing one with a source as part of the extra element theorem, with v_hat = 0 we have no impedances for Zn. I'm confused what v_test/i_test should be in this case.

test sources clarification & HW3 P2a

Can someone please comment on how I am interpreting the use of test sources.

- When adding an extra element in the place of a short in the original system a voltage test source will enable you to find Zd.  If you elect to use a current test source instead you will end up finding 1/Zd.

- When adding an extra element in the place of an open in the original system a current test source will enable you to find Zd.  If you elect to use a voltage test source instead you will end up finding 1/Zd.

That said for problem 2a) if I wanted to treat the inductor as an extra element while creating a short in the original system then I should add a voltage test source to find Zn and Zd?  By nulling vout does this effectively short the transformer leaving only the capacitor impedance for Zn?

Thanks,

HW#3, P2a Gvg

What is the trick to push the test voltage (i.e. L) to the secondary side?

HW 2 Solutions: LTSpice modeling?

Hey all,

I'm looking at the ccm5.asy file included in the HW2 solutions.

I am unfamiliar with spice.  I can build the circuit as shown in the .asc file in the solutions, but am lost when it comes to building and using the CCM5 subcircuit.  Could I get a step by step procedure on how to do this?

Thanks,
Vincent

HW 3 P1b

In part (b) we are supposed to plot the magnitudes of ZN, ZD, and Resr. So far, so good. But there are two questions about how Resr affects the transfer function. I am not sure how plotting Resr is helpful to answer the questions. It seems like Gnew(s) needs to be plotted. Is this the case or are we to answer these questions based on expressions for f0, Q, etc. derived in part (a) which contain Resr? Thanks.
- KT