Question about the book "Switch-Mode Power Supplies SPICE Simulations and Practical Designs by Basso"

Thread Starter

BlackMelon

Joined Mar 19, 2015
102
Hi guys,

I would like to know if you find the variables in the aforementioned book confusing? Especially, those on equations and those on schematics usually do not match even they mean the same thing. If so, do you have any suggestion about good power supply books? I would like to design a control loop of current-mode DC/DC converters.

Sincerely,
BlackMelon
 

Papabravo

Joined Feb 24, 2006
14,700
Not particularly, but I'm not sure what you mean by the variables. Are you talking about the connection between the theoretical development and the particular dialect(s) of the spice netlist files. Is there a particular section you are having trouble with?
 

Thread Starter

BlackMelon

Joined Mar 19, 2015
102
Not particularly, but I'm not sure what you mean by the variables. Are you talking about the connection between the theoretical development and the particular dialect(s) of the spice netlist files. Is there a particular section you are having trouble with?
What I mean is like this:
I let a variable v = V + v_hat. The first one is a DC voltage, and the second one is an AC voltage. On the schematic, which is written on PSpice, I dropped "hat" from the AC voltage since PSpice doesn't allow me to type hat. This is one of the confusion I found on the textbook. There is a lot more confusing points.

Thank You
 

Papabravo

Joined Feb 24, 2006
14,700
What I mean is like this:
I let a variable v = V + v_hat. The first one is a DC voltage, and the second one is an AC voltage. On the schematic, which is written on PSpice, I dropped "hat" from the AC voltage since PSpice doesn't allow me to type hat. This is one of the confusion I found on the textbook. There is a lot more confusing points.

Thank You
Nowhere is it written in stone that there must be a one-to-one correspondence between what is written on the page for a theoretical derivation and in the textual representation of a model which is supposed to behave in the same way. The connection between the two can be either implicit or explicit. The task of students like us is to verify, in one way or another, if the model and the theory are in agreement as to what they represent. You not only have to understand the details of the derivation, you have to understand the semantics of the spice representation. As you are no doubt aware, a spice text files is a poor way to convey to a sentient being the details of a circuit. On top of that, even the best authors, make occasional mistakes. I have found and reported errors in textbooks. Read enough of them and you will too.

I will tell you that I can look at a printout of a spice file and tell you if it is syntactically correct. Under no circumstances can I tell you if it represents a correct or viable circuit. I have to convert it to a schematic to have any hope of doing that. I would not be willing to wager more than a trivial sum on the ability of anybody on the planet to tell you if a spice file is semantically correct. It is the same for any text file that represent a piece of software as well.

In your example, you are describing the linearization of equations about an operating point. One fact you may or may not realize is the a spice engine does this all the time under the hood without you even being aware of it. Expecting things to be explicitly relatable is unrealistic. Being able to do it take a much deeper understanding of what is going on.
 
Last edited:

Thread Starter

BlackMelon

Joined Mar 19, 2015
102
Papabravo.
Sir, the mismatch between a variable in an equation and PSpice is just an example of confusing points in the book. My trouble is in the attached pdf file. Starting from 2.3.3, this is the current mode control of a buck converter. In this book, the average values are represented by capital letter such as Ia and Ic in (2-149). The instantaneous ones are followed by (t). For perturbation, there will be a "hat" sign. For example, d = D0+d_hat, where D0 is a duty cycle at equilibrium point and d_hat is a perturbation.

On the last page, it said that I have to perturb the equations (2-157) and (2-149) to get the model in figure 2-64. I am trying to find what variable should I perturb apart from the inductor current. Even I read the previous sections and tried to perturb the equations by myself, I didn't get the same model.
I would like to hear any suggestions and appreciate your help in advance.

BlackMelon
 

Attachments

Papabravo

Joined Feb 24, 2006
14,700
Basso has at least one example in his book (2008 edition) of using the perturbation method to create a small scale model from a large scale one. To do this particular example you follow the identical procedure. Your question about what gets perturbed has a one word answer: EVERYTHING. Here is my handwritten development of the section in question. I hope you find it helpful.
 

Attachments

Thread Starter

BlackMelon

Joined Mar 19, 2015
102
Basso has at least one example in his book (2008 edition) of using the perturbation method to create a small scale model from a large scale one. To do this particular example you follow the identical procedure. Your question about what gets perturbed has a one word answer: EVERYTHING. Here is my handwritten development of the section in question. I hope you find it helpful.
Oh! I appreciate your help very much! It took me the whole 2 days trying to reread previous chapters again and again.
You are my savior! Thank You. ^_^
 

Papabravo

Joined Feb 24, 2006
14,700
Oh! I appreciate your help very much! It took me the whole 2 days trying to reread previous chapters again and again.
You are my savior! Thank You. ^_^
I actually learn things better when I have the opportunity to write them down. I also tend to keep my textbook notes whenever possible. My wife insists I have to dispose of 35% of everything I own each year.
 

Thread Starter

BlackMelon

Joined Mar 19, 2015
102
I actually learn things better when I have the opportunity to write them down. I also tend to keep my textbook notes whenever possible. My wife insists I have to dispose of 35% of everything I own each year.
If she were able to dispose those materials, it would be disastrous I guess. About the circuit we discussed, on the last page of the pdf file, I do KCL at node C and see if the result (ic_hat) match that of perturbating (2-149) and (2-157) or not. They don't match each other. I noticed that I got the term "d_hat" when doing perturbation while it is not so for KCL. So, I would like to know if the duty ratio is fixed?

Sincerely,
BlackMelon
 

Attachments

Top