I am to design a switched mode psu without IC components.Help please

[dorke]

Thank you very much for your help. The link you put also looks very very helpful. The name of the course is Electronic Circuits I

That specific name doesn't mean much.
Could you post the syllabus of the course .

 

[Herschel Peeler]

Thank you for your help. However, we have not covered anything like oscillators or flip flops in class. Its not in our syllabus for the semester.

Are you limited to material covered in the classroom?

 

[Oluwatimilehin]

That specific name doesn't mean much.
Could you post the syllabus of the course .

Diodes and Diodes Applications
BJT analysis (AC and DC)
FET Analysis
Transistor Amplifiers

This is basically all I am covering this semester.

 

[Oluwatimilehin]

Are you limited to material covered in the classroom?

Well I don't think so. The only restriction is to not use IC circuits.

 

[dorke]

Did the course cover BJTs and MosFETs as switches?
Have you covered Schottkey diodes?
What about about op. Amps?

Edit: What about differential Amplifiers ?

 

[Oluwatimilehin]

Did the course cover BJTs and MosFETs as switches?
Have you covered Schottkey diodes?
What about about op. Amps?

Edit: What about differential Amplifiers ?

1) BJT and MosFETs as Switches: Its been mentioned but not in depth.
2) Scholkey diodes: Nope.
3) Op amps: Nope, thats for next semester.
4)Differential Amplifiers: Nope

 

[dorke]

What about zener- diodes ?

 

[Oluwatimilehin]

What about zener- diodes ?

Yeah

 

[Oluwatimilehin]

I have been in electronics for 50 years and I would not know where to start with a switch-mode design.
Even a practical circuit would take weeks to design, build and test and modify.
That's the IGNORANCE of most teachers.
I sent letters to 2,300 IT teachers in Australia with a set of kits and projects. I got 19 replies 18 months.
I asked WHY?
Because we haven't a clue how to fix a project if it doesn't work.

Yeah it sucks. I wish I had a choice.

 

[Oluwatimilehin]

This is the sort of thing I am thinking of. This is how your block diagram should look. This is an example only and your blocks may differ and some blocks you may not implement on your design.
Adam

View attachment 26229

Hi Adam, I decided to go with designing a buck converter circuit per a recommendation here and I found a few helpful resources. I have been using this( http://www.arrl.org/files/file/QEX_Next_Issue/Jan-Feb 2013/Dildine.pdf)material and I have been able to calculate my inductor value. However when it got to the value of my output capacitance, I found this (http://www.ti.com/lit/an/slva477b/slva477b.pdf) material because the formula is clearer.
My problem here is that there is a value of ESR that I need to get, I have no idea how to get that value and I seem to have searches all over. Can you please help?
My parameters are:
Vin= 220v;
Vout= 15v;
I(load) = 1A;
Duty Cycle = 15/20 = 0.0682;
F = 50hz.

Also, is a buck converter circuit a regulated circuit?
Thank you.

 

[Arouse1973]

Hello, The ESR of a capacitor will be in the data sheet for the capacitor you choose. A buck convertor is only regulated if it has feedback into the control circuit so the PWM can change to allow for different load currents.
Adam

 

[Oluwatimilehin]

Hello, The ESR of a capacitor will be in the data sheet for the capacitor you choose. A buck convertor is only regulated if it has feedback into the control circuit so the PWM can change to allow for different load currents.
Adam

Thank you. Do you think a flyback converter can be used here instead of a buck converter?

 

[Arouse1973]

Flyback convertors are a buck boost, do you need that? Also they have isolation from the transformer, I guess you will need this with your design. So you decide. If you don't need boost then go for a forward converter.
Adam

 

[Oluwatimilehin]

Flyback convertors are a buck boost, do you need that? Also they have isolation from the transformer, I guess you will need this with your design. So you decide. If you don't need boost then go for a forward converter.
Adam

I think I'll go with designing a forward converter.. I have been looking for some help online on how to go about it but everything seems to be going way over my head. Do you have any recommended tutorials?

 

[Arouse1973]

I think I'll go with designing a forward converter.. I have been looking for some help online on how to go about it but everything seems to be going way over my head. Do you have any recommended tutorials?

Hello, no sorry I don't have any tutorials. I would recommend purchasing a book on SMPS design.
Adam