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Hi Guys need help with a charger circuit please

Discussion in 'Repairing Electronics' started by Dr Bob, Sep 7, 2013.

  1. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Who knows? :D.
    Couldn't find a 60N06 model in the Yahoo libraries, but FET type shouldn't make much difference for the spice analysis provided Vturnon is <<~8V. I've tried a few different FETs and get similar results.
    BTW, on the 'fast' setting the charge pulses are in bursts whose duration(~0.5s) and period (~1.5s) are set mainly by the charge and discharge times of C3.
     
  2. Dr Bob

    Dr Bob Member

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    Ok, well it's supposed to be a 12 amp charger in fast mode, but in the sim I am seeing currents up to 60 amps mostly sometimes pulses of 120 or more?
     
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Try using realistic values for those resistances, e.g. 0.1Ohms for the transformer secondary etc. I was getting peak currents ~16A.
     
  4. dave

    Dave New Member

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  5. Dr Bob

    Dr Bob Member

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    Ok Alec will do mate
     
  6. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I've found that the duration of the burst I mentioned in post #41 increases slightly as the medium-term average charge current (averaging due to R42,C12) reduces, so there is current control of a sort.... a very slow PWM control.
     
  7. Dr Bob

    Dr Bob Member

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    That's good, what are you using as a mains source and transformer Alec? I can't find any transformers that you can set the primary and secondary voltages?
     
  8. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I didn't use a transformer; just a Voltage Source (i.e. like Vbat in my .asc file) to define the secondary voltage with a series resistance of 0.1 Ohm.
    To create a transformer in LTspice you use two inductors L1,L2 and a spice directive like "K1 L1 L2 1" as text (without the usual dot) to define the coupling factor K (nearly always 1) between the inductors. When considering turns ratio, remember that inductance (which you specify) is proportional to the square of the number of turns.
     
  9. Dr Bob

    Dr Bob Member

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    Thanks Alec, that wasn't the problem I did a transformer ok but it turns out that spice does not like a primary winding floating and bitches about nodes not connected, I had to connect a 100meg resistor from the primary to deck. Works now, I used the voltage source as the 50hz generator, I am only really just doing it to get familiar with the program. I did have as you can see the .015 and the .oo75 at the top in the circuit, but it wasn't until I introduced the transformer that I got the pulses and could see what you were saying. Incidentally, two things,
    The .0075 has the ammeter across it. And I suspected from the get go the pulses would be involved because the caps were missing but when I put a scope on it there are none to be seen, I can only asume the battery acts as a giant capacitor and smooths them out.
     
  10. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I was going to mention that. You've come up with the exact same solution I use. Without that bleed to ground the sim just can't make up its mind and takes forever.
    Seems likely.

    BTW, when running sims it speeds things up a lot (at least it does on my ancient laptop) if you can break the circuit down into independent sections (as is possible with your charger) and sim each section separately.

    Edit: I successfully logged into my Yahoo LTspice account without having to give a mobile number; but it did nag me to provide one (allegedly to enable a password reminder to be issued if necessary). Maybe a mobile number is now compulsory for new accounts?
     
    Last edited: Sep 15, 2013
  11. Dr Bob

    Dr Bob Member

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    Thanks for the tips Alec. yes it sure is and yet they deny it, people have and are complaining and they answered that the mobile number is not compulsory and to just leave the box empty, I tried it and it won't let you move past there unless you give one. they are obviously trying to collect enough to sell to sales companies, criminals :rolleyes:
     
  12. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Well it doesn't have to be your number (unless they actually do phone to give you some access code for the site) :D
     
  13. Dr Bob

    Dr Bob Member

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    You sort of got it, I tried that, I entered a make up number and then got a message saying they had tried to send a confirmation text and the number didn't exist
     
  14. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Hmm. Given that one third of the UK population (don't know about the rest of the world) doesn't have a mobile they seem to be cutting off their nose to spite their face.
     
  15. Dr Bob

    Dr Bob Member

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    Indeed, and it's not the first time I have encountered it. I have done internet orders where I come to check out and can't get past the mobile number box and so they have lost the sale over it, makes no difference to me.
     
  16. Dr Bob

    Dr Bob Member

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    Wow! I love the facility to have a component automatically changing value during a run, makes it easy to find the right resistor or cap for the job :D
     
  17. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Yes, that's handy. Sounds like you're climbing the learning curve quickly! There's heaps of LTS features I've yet to discover/use.
    One tip; set the Tools/Options to delete the .raw file when you exit the programme. Those files can be massive for a lengthy sim.
     
  18. Dr Bob

    Dr Bob Member

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    Ok Alec thanks mate, I did a lot of work with the protel designer 99 suit back in the day, similarities with regards to drawing the circuits, placing components, etc helps plus of course years of experience actually doing the job and fault finding with scopes meters and using the force :D


    I'm just comparing what is actually written in the library of a particular power fet and comparing it to it's data sheet, nothing seems to make sense or match at all! any idea why?
     
  19. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Ah yes, The Force. Never leave home without it.
    I've next to no understanding of the hieroglyphics/parameters in the models. Berkley Spice seems to be the basis of it all, but I've not had the energy to get stuck into it.
     
  20. Dr Bob

    Dr Bob Member

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    :D fair enough, I'm finding that when you go to certain suppliers sites and look at a particular component there is often a model zip file available which contains a spice library file, then you can use the automatic function to create the asy or adapt one from a similar device
     
  21. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    There are some details here.
    http://ltwiki.org/index.php5?title=Undocumented_LTspice

    E
     

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