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

Discussion in 'Electronics Homework Help' started by Oluwatimilehin, Apr 12, 2016.

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  1. Oluwatimilehin

    Oluwatimilehin

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    Apr 12, 2016
    I am supposed to perform certain calculations to get the desired outputs and then design and test my circuit on a software before I start building it. I am not asking anyone to do my project for me, I just need directions on how to go about the calculations and eventually designing my circuit on a software. I have no idea about how to go about this.
    I would appreciate if someone could literally walk me through this please?
    The project question is uploaded as an attachment. I circled the question which pertains to me. Also, I am supposed to choose only one of the outputs,not all of them. Thank you!
     

    Attached Files:

  2. Herschel Peeler

    Herschel Peeler

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    65
    Feb 21, 2016
    Take a look at a data sheet for any switching regulator. That will give you an idea of what stages you need and a general design. Rectify the line voltage. Chop it up at some desired frequency, run it through a transformer. Transformer secondaries provide the desired voltages at certain currents. Provide for some feedback mechanism to regulate the output voltage. Regulate the output by varying the width of the pulse from the oscillator.

    Step one: choose an IC to emulate.
     
  3. Alec_t

    Alec_t

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    Jul 7, 2015
  4. Oluwatimilehin

    Oluwatimilehin

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    Apr 12, 2016
    My post says I need a circuit without IC components...Also, your explanation is definitely not simple enough for someone with little or no experience in electronics/
     
  5. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    They are expecting you to design a switch mode power supply without a controller IC and you don't have any experience in electronics. That's a bit unfair don't you think.
    Adam
     
  6. Oluwatimilehin

    Oluwatimilehin

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    Apr 12, 2016
    Yeah but theres nothing I can do about it. My school kinda sucks so I just gotta do this project if I want to get my grades and I don't know how to go about it.
     
  7. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Ok I am going to bed now, I'll have a think about it and try and help tomorrow. But there is a great bunch of far more knowledgeable guys on here than me that will most likely beat me to it.
    Adam
     
  8. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Did they teach you anything about Switch Mode Power Supply?

    What "Innovation" are they talking about?:(
    Sorry to say this ,
    but this sounds like a pompous teacher/school ,full of B.S
     
  9. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    I am not suggesting you use the I. Only get an idea of what stages are in the switching regulator and some possible designs. Are you taking a class you are not ready for?
     
  10. Oluwatimilehin

    Oluwatimilehin

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    Apr 12, 2016
    Let's just say I thrive in the theoretical aspect of the course i.e BJT analysis and all that but when it comes to the practical aspect, I am not very good at it.
     
  11. Oluwatimilehin

    Oluwatimilehin

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    Apr 12, 2016
    Nope he didn't. The teacher sucks and majority of students usually fail his course. That's why I'm here desperate for help.
     
  12. dorke

    dorke

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    Jun 20, 2015
    Well,
    We can help you with that design.
    But,
    you should do most work yourself(so that you will learn).

    Start and show what you have come-up with and get feedback.
    Ask questions freely.

    The issue of SMPS design isn't very simple it has a lot of issues involved with it.
    I would design a Buck-converter also called a step-down converter.
    Select the lowest current from the list(i.e ±15V /1A).

    To make things simpler create
    a dual unregulated DC voltage P.S at a voltage of a few volts higher than the needed voltage ,
    This should use a Line transformer at the line voltage and frequency in your country (this isn't the most efficient way only for simplicity).

    It is important, so that you wont need to get into transformer magnetic design(not a simple issue at all).
    Find out what transformers are available in your lab, remember you should use a center taped one
    (to create ±vt) that can deliver a current more than the 1A required .

    Look here for details.

    BTW,
    What is the name of the course?
     
    hevans1944 and Arouse1973 like this.
  13. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    Such is the objective of a school; theoretical to practical.

    So starting ... what do most switching regulators have in common to their design? We have an oscillator whose leading edge sets a flip flop. rthr flip flop is cleared by a "good voltage" signal of some kind. The output of this flip flop is what drives the output. So we need:
    1) oscillator
    2) flip flop
    There is your starting point. Suggestions from others are also valid approaches to starting. All these aspects must be covered.
    In your classes on theory what does a transistor oscillator look like?
     
    Last edited: Apr 13, 2016
    Arouse1973 likes this.
  14. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Ok that's a great start. I personally would start a block diagram of the circuit showing power connections and output / inputs coming from and going to the relevant blocks. You can then take one block at a time and look at a circuit for that. Then you build the next block and so on. It's sometimes easier than being overwhelmed with the thought of designing everything in one go.
    Adam
     
  15. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    Good. Build and test the same way, stage by stage. Sid you say the teacher wanted you to do simulations before building? That is good procedure. Design then simulate stage by stage as you go along.
     
    Arouse1973 likes this.
  16. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    You teacher is hard?
    If you want to accomplish big things do not surround yourself with people who ask too little of you.
     
  17. Oluwatimilehin

    Oluwatimilehin

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    0
    Apr 12, 2016
    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.
     
  18. Oluwatimilehin

    Oluwatimilehin

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    0
    Apr 12, 2016
    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
     
  19. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    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

    BD.PNG
     
  20. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    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.
     
    hevans1944 and Arouse1973 like this.
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