Help with This circuit (H-Bridge 1ph full wave inverter)

Discussion in 'The Projects Forum' started by Ahmed Waleed, Mar 9, 2009.

  1. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    Dear All,
    Please help me to find the error in this circuit.
    The circuit is H-Bridge 1ph full wave inverter.
    I built this circuit using Proteus 7 Prof. like a ready made model in MATLAB but it doesn't work and it gave me some errors.
    Please see it and tell me where is my mistake.
    thanks in advance
     
  2. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    please try to help me, i can't do it myself as i'm new in the filed of electronics.

    I have fired the MOSFETs using the output from PIC18F452, it's a square wave with 50% duty cycle and max. voltage of 5 volts.
    the output frequency from PIC is 244 Hz.
    I hope this helps you to correct me.

    Thanks
     
    Last edited: Mar 9, 2009
  3. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    17 persons watched the topic and no reply. am i asking for something really hard or it's just too easy to answer....please help me I'm really in deep need of it.
     
  4. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    please guys i want your help..................:(
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,635
    2,342
    Hello,

    I think the main problem is that the difference between gate and source voltage of the FET is to low.
    The gate must be ca. 10 volts higher as the source to fully open the FET.
    The ground position if the bridge can also cause problems.

    [​IMG]

    I have put the schematic in again so the others can give their comments too.

    Greetings,
    Bertus
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    If you are new to this stuff why you try to make advanced things?

    To make your circuit work you will need a MOSFET driver IC to drive your MOS.
    MOS typically require 10V Vgs to fully turn on unless they are logic level MOS. By only 5V from the PIC they won't turn on. Also, the high side MOS will need a bootstrap circuit to be able to turn on unless you use p-channel ones.
    What is more, a PIC can't supply enough current during the switching and the MOS will turn on slowly, dissipate more heat and may burn.

    What kind of AC load are you planning to supply?

    What is the required output AC voltage? Where is your step up transformer?
     
  7. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    Thanks for your help and I think you'll be a good support for me.
    To tell the truth it's something I'm forced to do otherwise I'll fail in the project in my final year Engineering.
    I didn't knew that the MOS needs 10v. to fully turn on so I think I will use FET to externally fire it, and about the MOS driver do you recommend one for me.
    about the required AC voltage is 220V with 60Hz (i'll manage the frequencuy using the PIC)
    and about the load, I think I'll use an small induction motor for it.
    About step up transformer, I don't know what you're up to with it coz I don't know why i'll use it.
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    You need to use Logic Level Mosfets, The IRL3075 series looks like it would work if you are dealing with automotive voltages. If working with other voltages, look up the specs at International Rectifier's site.

    As Mik3 stated, you will need a MOSFET driver for each MOSFET if staying with the IRF540s.

    Regarding response time, just a tip:
    The more useful/visible information you have in the original post, the more likely replies/suggestions will be prompt. A schematic image with a text description of inputs/outputs desired, as well as information on what you are getting experiencing can give enough information to shortcut questions. A proprietary netlist/formula file inside a ZIP doesn't make that information easily accessed.
     
  9. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    thanks for the tip but I can't find any information about IRL3075, if i used FET with an external circuit as a dirver for the mos, will it work? or I'll face the same problem.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
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    I'm not sure. Not enough information.

    You mention 220V and a motor, I see a 12V battery.

    Is it the same circuit?

    Information and application helpers available at http://www.irf.com/
     
  11. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    yes you're right, I started simulation with 12 V battery and if it succeeded I'll use number of batteries in series to get the 220V.
    I'm in the trying period, i didn't made a real circuit yet.
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If that's the plan, I'm guessing I won't be of any help.
     
  13. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    I don't know If I've offended you or not but thank you for all your help and thanks for all guys who answered and tried to help me.

    I think I'm useless and still ignorant.
    anyway, maybe I can manage it by myself and I'll give you updates.

    Thanks
     
  14. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    If you use n-channel MOSFETs then you will need a MOS driver for sure because the gate voltage of the high side MOS needs to be bootstrapped as to compensate foe the increase of the source voltage due to the voltage drop across the load.

    You will need a transformer to step the 12V pulsating voltage up to 120V AC.
     
  15. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I didn't mean to be rude, I'm just having a hard time picturing a 150 AA Battery holder, or 19 car batteries tied together to 4 mosfets in a real life application.
     
  16. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    Thanks mik3, this really helps me and teaches me the use of step up transformer
     
  17. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    here's the practical model for what you need
    anyway i blame you nothing, you've tried to help me as you can and i'm thankful for you.
     
  18. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    May I please suggest if you intend to produce potentially lethal high voltages (albeit generated from a seemingly harmless 12V battery) that you give due consideration to the overall electrical safety of the equipment and most importantly - your own safety when working on it!
     
  19. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    In the diagram you posted I see a high DC voltage.

    Are you allowed to produce it by using a rectifier in your project?

    If yes, then you won't need a transformer.
     
  20. Ahmed Waleed

    Thread Starter Member

    Mar 4, 2008
    22
    0
    thanks, and I'll take your words into consideration...but what can i say, I'm stuck with this and I don't have a clue.
    Anyway, thanks for all of you guys for your help.
    I have learned that without knowledge about things you intend to do it's better not to do it.
    By the way my misery will not stop here, I'm willing to make a suitable design for Sinusoidal PWM Multi-Level Inverter.
    so this 1ph bridge will be nothing compared to it.
    it's 3 am here and I have to go to sleep.
    Thanks :)
     
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