What a ride!

Thanks, Professor, for a very interesting semester.

HW13

Can anyone provide direction on how to start this problem?  Originally I thought I would need to construct the boost input control loop to derive the equation for d(t).  To do this I created the large signal model then linearized to generate a SSM.  However, now I've confused myself after looking through the slides because I am wondering if part a is asking for large signal models of all three control loops?  Any advice is appreciated.

HW13 (d)&(e)

Anyone having any luck with part (d) and (e) of HW13?  I'm trying to figure out if we're supposed to build our own model to do plotting, etc?

Problem 18.14 a. choosing value of C

For 18.14 part a. I assume that we must first determine a value for C to satisfy the Gvd transfer function for the loop gain of Ti = (va/ig) * (Gc) * (1/Vm) * (Gvd). Is this the same approach other folks are using?

18.10d&c RMS Ripple Assumptions

In these problems it asks us to find the worst-case rms currents of the inductor, MOSFET and diode.  When it refers to rms currents is that over a line cycle such as in Table 18.3?

Furthermore, the expressions in Table 18.3 neglect the effect of switching ripple.  Does this mean that we cannot use the expressions given in Table 18.3 and that we need to derive new expressions that take into account the switching ripple with the inductor that we have chosen?

Question for 18.1

Hello,

I am confusing about the define of the LOAD POWER in 18.1 (d). Does this contain only the power on the resistor or also contain the power both on resistor and capacitor?

Thanks.
NY

Re for 18.2

So I am starting to confuse myself on what Re should be for 18.2.  Do we use the DCM boundary to determine the Re for DCM or is it the standard 2L/d^2Ts?  What decides Re?
It seems that because the vg/ig=Re in both the DCM of Chpt 11and in our current model, Re is the same but if this were a Cuk or Sepic then Re would be different.  Is this correct?

Suggestions for OpAmp model

I have suggestions for the OpAmp model to use for HW10 if you have problems.

Try using "UniversalOpamp2" instead of LT1368.
The default parameters for this model is sufficient for our simulation.
The ideal opamp seems to not work well for many people.

If the design is done correctly, there should be no convergence problems, and no need for initial conditions.

Beom

PWM comparator questions

I have not been able to find a comparator that will work in this application. I'm sure there is one, but I'm not having much luck with getting the output for d correct. I have the sawtooth, and Vm , but I'm struggling with the comparator.
Suggestions?

Extra Credit

Hi All,

I am a little confused as to what the difference is between the last part of problem 1d and the extra credit is... they both ask to verify problem 1 using spice...

Can anyone elaborate on what the difference is between the two?

Thanks!

HW10 P16.1

In part (d), I am a little confused about the question statement. Are we supposed to find two power factors, one for input (surface S1), and one for output (surface S2)? Thanks.
- KT

HW 10-1 Creating PWM Spice block.

Hi,

I've read in the text that the PWM block is modeled in Spice as simply vx/VM where vx is the input and VM is the sawtooth peak value. The text also says to limit the output to between 0.1 and 0.9. A couple of questions:
1) I used the LTSpice voltage dependent voltage source, put the output of the compensator into the component and set the scale factor to 0.5. Does this work?

2) Where do the limit values 0.1 and 0.9 come from and how can they be implemented?

Thanks.

-Drew

failure to find a DC operating point

* C:\Program Files\LTC\LTspiceIV\homework 9.asc
Vg 1 0 12 AC 1
L 2 4 4µ
R 4 0 1
C 4 0 100µ
XU3 Vc N003 N005 N006 5 CPM Rf=.1 Va=0.3125 L=4u fs=100k
E2 N005 0 1 4 1
E3 N006 0 4 0 1
H1 N003 0 value={i(L)}
XU1 1 2 2 0 5 CCM-DCM1 L=4uH fs=100k
XU2 N001 N004 Vc opamp Aol=100K GBW=10Meg
R1 4 N001 10k
R2 N001 N002 9.1k
C2 Vc N002 11n
C1 Vc N001 700p
Vref N004 0 5
.lib switch.lib
.ac dec 101 10 100k
.lib opamp.sub
.backanno
.end

--------------------------

With a higher value for R (around 10 ohms) spice can resolve to a DC operating point. At R = 1 I get "Failed to find DC finding operating points for AC analysis".

Any suggestions?

I have tried (most) of the suggestions listed. 

compensation circuit questions

On homework 7 we were given a type 2 compensation network for problem 2 as part of a Buck voltage regulator operating in discontinuous conduction mode. As we are using this same compensation circuit for Homework 9 I have a few questions regarding the solution given on homework 7.

I have a calculated transfer function of vc/v is equal to: (sC2R2 + 1)/[sC1R1*(1+sR2C1C2/(C1+C2))].  If the pole at C1R1 is designed to be equivalent to C2R2 then (sC2R2 +1)/sC1R1 becomes 1 + w/s, an inverted pole.

In the solution, it states that "at mid-frequencies around fc, Gc(s) = R2/R1". Can anyone give me any help on where this comes from and how we determine it?

Additionally, the equation used to determine the crossover frequency where T = unity gain is given as:
1/Vm * R2/R1 * Gd0 * fp/fc = 1
where does the fp/fc come from?


UDPATE: I actually found a good paper on the Intersil site that discusses this compensation network.
www.intersil.com/data/tb/tb417.pdf

I'm still confused about the unit gain equation, and anyone who can give help on this would be appreciated.

Gallium Nitride (GaN) presentation tonight in DLC

In last Friday's lecture Professor Maksimovic mentioned that the big trend at APEC was the increasing use of wide-bandgap and compound semiconductor devices, like those made from GaN and SiC.

I would like to invite you to my presentation tonight in the DLC called "Putting GaN To Work In Your Power Supply".  More information is here: http://www.denverpels.org/Meetings.html.

The meeting starts at 6 pm with pizza and networking.  This is a great way to meet local people working in power electronics.  The presentation will start about 7 pm.  The meeting is open to all interested persons.  You do not have to be a member of the IEEE or the IEEE Power Electronics Society to attend so please join us in you are interested.

Problem 9-2 factoring denominator

Hi,

I've started problem 9-2, and I've run into an issue. I began with the same analysis as the text and the lecture notes. I used equation 12.89 (for Buck) and substituted in Fm = Fm/(1+s/wx). The denominator becomes 3rd order which means you can't simply rearrange to find new expressions for Qc and wc.

Do we have to do some factoring of the denominator, or some approximation to isolate the effective high frequency pole?

Thanks.

-Drew

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!

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?

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?

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

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

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

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.

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

HW submission while D2L is down

Since it appears that problems with the D2L system could take more time, please use this alternative method to submit your work: send your files as email attachments to ecen5807@gmail.com. The due date for HW2 stays the same: Friday, February 1, 10am Mountain time.

error resolving equations

I was not able to successfully run the simulation from the first homework assignment. Matlab gave me an error that it was 'unable to resolve equation'. My state equations match those given in the solutions, and I followed the same set of steps as given in the step-by-step guide. If there is any suggestions that anyone can give on what might be giving this type of error I would appreciate it.

Laura

HW2 Prob 2A Stuck on Algebra

Hello:

I am having major trouble with the algebra for problem 2A.  There must be something that I am missing.

The voltage equation is fine and okay to put into the model.  However, when solving for i2, I cannot isolate (d'/d)*<i1> and when solving for i1, I cannot isolate (d/d')*<i2>.  Therefore I cannot solve the transformer.

The approach I am taking is to solve for Ion and then plug into the other current equation.  This leaves the currents multiplied by a factor of 1/(d+(tr/Ts)).  I can combine all of the terms by taking the common denominator, but this leaves a very messy numerator term which does not help much.

Also, if I add the two current equations, I can eliminate a lot of variables.  This results in <i1>+<i2> = Ion which is not much help.

Any assistance will be much appreciated!  Just some small hint will probably help me get to the next step so that I can proceed with the assignment.

If anyone is having similar problems, let's put our heads together to solve this.  I can email you what I have so far and then we can go from there.  I also am available for email, gchat, fb, or cell phone.

Thank you,
Alex

HW2 pblm 2

Do we have to use CCM5 model already present in switch.lib or can we create another model ? I havent got the model that is available in CCM5 my model looks different.

HW2: 1(b)

Is the idea that HW2: 1(b) requires us to write a MATLAB script (or modify Salient) to find the Load at which the pair RHP zeroes appear? Pretty simple by trial and error (esp w/i 10%), but want to clarify the the perceived requirement...anyone?

Netlist error?

I have the following CCM5 netlist (see below) as part of a larger schematic.  I get the following errors when I "run" it:
"Questionable use of curly braces in "b§er 1 1x v=v(5)*i(et)*{ron}+(1-v(5))*({et})*{rd}"
    Error: undefined symbol in: "[et]"
Questionable use of curly braces in "b§gd 4 3 i=({qr}/{ts})+({tr}/{ts})*i(et)+(1-v(5))*({et})"
    Error: undefined symbol in: "[et]"
Fatal Error: u1:gd:  -- Syntax Error --
Unknown symbol: et"

Any ideas why LtSpice does not like Et?

Also, is the CCM5 model found in switch.lib the correct model for HW2, problem 2?

Thank you,
CD

**********************************************************
* MODEL:    CCM5
* Application:    two switch PWM converters, includes
*         conduction loses due to Ron, VD, RD, Qr,
*        and tr for Ts
* Limits:    CCM only, no transformer
*
* Implementation:
* i1, v2 = independent variables
* v1, i2 = dependent variables
* <v1> = d(<i1>*Ron) + d'( <i1>*RD + VD + <v2>)
* <i2> = Qr/Ts + (tr/Ts)*<i1> + d'(<i1>)
**********************************************************

* Parameters:
*    Ron = transistor on-resistance, ohms
*    VD  = diode forward voltage drop, volts
*    RD  = diode on-resistance, ohms
*    Qr  = recovered charge, coulombs
*    tr  = recovery time, seconds
*    Ts  = sample frequency period, seconds
**********************************************************

* Nodes:
* 1: transistor positive (drain for an n-channel MOS)
* 2: transistor negative (source for an n-channel MOS)
* 3: diode cathode
* 4: diode anode
* 5: duty cycle control input
**********************************************************
.subckt CCM5 1  2  3  4  5
+params: Ron = 0.01 VD = 1 RD = 0 Qr = 0.00000015 tr =0.00000003 Ts = 0.000005
Er 1 1x value = {v(5)*i(Et)*Ron + (1-v(5))*(Et)*RD}
Et 1x 2 value = {(1-v(5))*(VD + v(3,4))}
Gd 4  3 value = {(Qr/Ts) + (tr/Ts)*i(Et)+(1-v(5))*(Et) }
.ends
**********************************************************

HW2 Prob 2A

Hello:

Since we will be solving this problem for a boost converter, can we use the equiv switch network for the Boost Converter (Fig 7.50b) for this problem?

Thanks,
Al

HW1 Solutions 7.16A

Good Morning:

On HW1 Solutions for problem 7.16A, why does Vd not appear in the equations or in the model?

Thanks,
Alex

HW 2 problem 2

I am having problems getting the ratio between the two currents to match the ratio between the two voltages (i.e. I can't use a transformer to model the equations I am coming up with).  Is it a requirement for the equivalent circuit we create to have a transformer, or can we use dependent voltage and current sources in our equivalent circuit?

fprintf function in MATLAB

Maybe somewhat trivial, but the fprintf function should print to the screen, correct?

Library function help

Can someone please describe how to use the library function "salient"?  I am new to MatLab and have NO IDEA how to use this script.  Am I supposed to edit the library file, or create a new script with salient('syncbuck_OL_LPfilter') embedded?  Do we ever edit the library files?  I've attempted to create a new script similar to when getSSM is used, but get the error below:


EDU>> salient_script
Undefined function 'zero' for input arguments of type 'char'.

Error in salient (line 6)
z = zero(sys);

Error in salient_script (line 11)
filter = salient('syncbuck_OL_LCfilter');

Any advice is appreciated.

Can't figure out how to use getSSM

I have had absolutely no success trying to use the getSSM library function.  I did see the "algebraic loop" error Colin mentioned - it was buried in a host of other errors.  I tried to back up and start simply: 
* I made sure I had linearization I/O points defined in the syncbuck_OL model and ran the bodeplotter on the model with success. 
* This left "ssm" defined in the workspace, so I ran >>salient(ssm) and got results consistent with the bode plot.
* However >>ssm = getSSM(syncbuck_OL) produced 3 error messages, probably all related to the first message:
"Error using linearize.ModelLinearizationParamMgr.getInstance (line 63)
Unexpected error. The getInstance method requires a model name argument."
Somehow a model name is missing??
Can anyone point me to some tutorial examples using this function?  This class is my first experience with MATLAB.  With such a fundamental level of failure, I have no idea where to start...

Algebraic loop issues with HW2 Problem 1

Does anyone else see algebraic loop issues with HW2 Problem 1 even with a gain block in the 'ig' path to invoke the Matlab algebraic loop solver?

I see issues if Rload is below a threshold.  No issues simulating with Rload above that threshold though.  Not sure if this has anything to do with the LHP -> RHP pole threshold or not.

Regarding input filter design

Hi,
As it was discussed in Friday session, the filter design is done after control loop design. Then it is suggested to minimize the effect of the filter design in the overall design using the proposed theory.
I was wondering why the filter design is not performed before control loop design. This would provide the chance to design the control loop in such a way to compensate for both filter and converter working together. What is the disadvantage of that approach?
Regards,

Netlist to Schematic?

Is it possible to convert the netlists listed on the course website to schematics as displayed in appendix B?

If so then what are the steps?

If we are expected to build a schematic from scratch then how does one add the (I'm guessing) component CCMx?

Thank you,
CD

HW2 Prob 2

Hi All,

I am getting a little confused on how to combine models I guess... When I try and incorporate switching loss and conduction loss in the same model, I am getting what I feel as an incomplete model... since the switching loss shows up as a current, when I use i1 and i2 as my ports to incorporate them in the model, the Ron and Vd don't come into play for the large signal model... I get a model that is very similar to Fig 7.56, with the exception of some different d(t) and d'(t) values... I assume that the large signal model should also have Ron and Vd in it, am I incorrect in my thinking?

Simplification of circuit for 7.15b

For problem 7.15b, after setting dhat to zero, I end up with the same small-signal equivalent circuit as shown in Fig 7.53 of the text (without the conduction loss terms). I tried to use the transfer function derivation shown in section 8.2.1 of the text, but I ran into difficulty handling the fact that the inductor is connected through the bottom of the ideal transformer and it is not clear how to "push" this impedance through the transformer in order to simply the circuit. Any suggestions?

7.15 Transfer function derivation

Hello:

For problem 7.15:

What is the method used to derive Gvg from the average switch small signal model?  I am not able to derive a transfer function because in my model, the positive side of the inductor is connected to the negative side of the primary, the positive side (dot) of the secondary, and the tail of the arrow for the current source.

I am trying to manipulate this into the canonical form, and I am able to push the current source to the primary side.  However, it is not apparent on how to push the inductor to the secondary.

Does the transformer need to be split apart into two transformers?

Thanks,
Alex

Input Filter CCM-Buck: OL or CL?

Good Morning:

For problem 2 (input filter), a value of D = 0.36 is given.  On the schematic given in Figure 1,
there are no feedback control loop elements shown except for Vc and VM.  Are the other feedback elements assumed to be in the circuit and not pictured in Figure 1?

Does this mean that we are to simulate the sync-buck converter with input filter in "open-loop" form?

I understand that in order to get the transfer functions requested, we will have to use the averaged model (uncheck the "switching model?") box.  This would lead one to believe that the given information of D = 0.36 is irrelevant to the questions being asked.

Thanks,
Alex

Problem 7.15

Hi All,
For Prob. 7.15, do I need to prove the two approaches give out the same equivalent circuit, or only to prove they have the same Gvg?
Thank you.
Zhiyuan

Mac OS 10.8 Mountain Lion Not Fully Compatible with Matlab

After upgrading to Mountain Lion over the break, Matlab starts, but can not compile functions in Simulink.  The following is Matlab's official compatibility policy:
http://www.mathworks.com/support/solutions/en/data/1-IXBVKD/index.html?solution=1-IXBVKD

Matlab is not guaranteed to work with Mountain Lion, except r2012b, which is not available as a student version.  There is no student version available that they guarantee to work with Mountain Lion.

They have FAQ's which supposedly help some users:
http://www.mathworks.com/matlabcentral/answers/56413-help-on-cpp-mex-file-compile-failed
http://www.mathworks.com/support/solutions/en/data/1-FR6LXJ/

Personally, I have reinstalled Mountain Lion, Matlab r2012a, and experimented with both Xquartz and Xcode 4.5.2 without success at Simulink compiling.

Has anyone else run across issues with Matlab on Mountain Lion and found a solution?

Frequency range setting for bode plots

I cleared most of the original post to unclutter the blog...  a summary:
1) re: original post -- I had bad state equations, but got no errors and had a very limited frequency range for a bode plot with no apparent data.  ...should have kept trouble-shooting before posting.
2) If you want to explicitly control the bode plot frequency range, the reply below has an example of one way to do that.
3) I'm still curious if anyone knows how Matlab/simulink determines the frequency range for our ac analyses.  (But it's not an urgent question.)
4) Many thanks to Dr. Maksimovic for extending the HW deadline and to whoever asked for the extension!

SRC PCs' Compiler Issue

Warning.

The ECEE SRC computers do not have the proper installation for Matlab/Simulink to compile Matlab/C functions.  Every time the SRC PCs are restarted (and booted from an image), they need to have .NET 4.0, then Windows SDK installed, which takes 10's of minutes to complete.  The following Matlab support page has links to both installs:
http://www.mathworks.com/support/compilers/R2012a/win64.html

After spending the time to complete the install on one SRC PC, I was able to perform HW#1, but do not know if all compiler issues are resolved.

The people in charge of the SRC images have been notified, but may not be able to do anything this semester, as they usually do not change images mid-semester to avoid deleting student information which may be present.

I do not know if this information applies to Matlab/Simulink as installed in other university labs.

OL vs CL plots

Whenever I plot the transfer functions of Gvg and output impedance, I get identical plots for the open loop and closed loop cases. This doesn't seem correct to me. All that I did was change the locations of the inputs and outputs. Is there something else that I need to do that I am overlooking?

Outpout Impedance Plot

Hello Everyone,

I have a question that someone may know better than me while doing the Bode plot for output impedance.  It seems that in Simulink you will get a plot of iLoad/vout if you plot it normally.  Do we plot 1/smm or smm (in the coding terms of BodePlotter_script.m) while using iLoad and Vout as the variables?

I would expect the output impedance to be in a "v" form like on Figure 8.65 in the text, but it looks inverted to me when I plot smm... any insights?

Zipped MatLab files OK?

Does anyone know if it will be acceptable to submit our MatLab scripts and models as a single zip file, perhaps one .zip per problem? 
(Will Dr. Maksimovic accept these and will D2L allow .zip file submissions?)

-Thanks!

Algebraic loop in syncbuck with input filter

After building the LC filter as described in homework 1, I tested it to make sure the simulation runs. To add the input filter to the syncbuck converter, I connected the output of the syncbuck, ig, to the input of the LC filter, ig. I also connected the output of the LC filter, vg, to the input vg of the syncbuck. When I try and simulate the system, I get an error stating that there is an algebraic loop present. Has anyone encountered this same error, and if so, any suggestions on how to fix it?

Open loop check option

When we check "Open loop check options" for the output node in Simulink, what does the "Open loop check options" function do?
Because it is not checked in "syncbuck_OL" simulation, but it checked in "syncbuck_CL".

HW1 Prob 1 Clarification

Hi All,

In problem 1 it asks to plot the open loop and closed loop output impedance and "input-to-output (i.e. line-to-output)".

By "input-to-output (i.e. line-to-output)" I assume that means line to output transfer function, Gvg... AKA (v^/vg^), is this the correct interpretation?

Lecture Recording Download Link?

Is there a download link for the recorded lectures available for non-CAETE students?

MATLAB/Simulink & C Compiler Problems

Last weekend I thought I would try to run some of the models to make sure everything was working with my copy of MATLAB/Simulink (I am off campus and have the commercial version, R2012a).  I wanted to give those working with their own MATLAB/Simulink installations a heads up on problems I found.

When trying to run the model I received an error message from MATLAB about a C compiler not being found.  As instructed I ran the MATLAB  mex -setup command.  It did not find a compatible compiler even though I had the Visual C/C++ Express 2010 toolset installed.  It only wanted the Visual C/C++ Professional 2010 version or the version found in the Windows 7 Software Development Kit (SDK).

When I tried to install the Windows SDK the install kept failing.  It would find the Visual C/C++ Express 2010 compiler but it was a later build than the one in Windows SDK (4nnn versus 3mmm).  The Windows SDK said that it was not necessary to uninstall the later version of the compiler.

Liar.  I had to completely uninstall the Visual C/C++ Express 2010 kit before the Windows SDK would install.  I spent several hours of Web searching and debugging before getting the SDK to install.

Once the Windows SDK was installed the models from the class ran fine.

I have not tried to re-install the Visual C/C++ Express 2010 kit.  To me this a failure on Mathworks' part in that they do not recognize or cannot use a valid compiler.  It is also a failure on Microsoft's part in that the Windows SDK won't install with a later version of the compiler already installed.

I hope that my experience helps someone else avoid a frustrating, hair pulling experience trying to get the Simulink models to run.

Welcome to Spring 2013 ECEN5807 blog

I would like to encourage both on-campus and off-campus students to use this blog to exchange questions, comments, ideas, discussions or pointers related to class materials or homework assignments. I may use the blog to answer posted questions for the benefit of the class. However, I will  not moderate or edit your posts (except in cases of course policy violations), so you should not assume that any comments or ideas posted by other students here have been approved, verified for correctness, or endorsed by the instructor. 

The blog includes an archive of posts from Spring 2011. You are welcome to look through these old posts, but keep in mind that references to specific homework problems may be wrong since Spring 2013 assignments and lectures may be modified and updated.