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H-BRIDGE schematics

Discussion in 'General Electronics Discussion' started by reviser, Sep 26, 2013.

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  1. reviser


    Sep 26, 2013
    I'm developing an h-bridge to control the speed and direction of rotation of a DC motor.
    The motor I need to control is 24V 10A.
    I've created a schematic for the the h-brigde but I'd like to hear some opinions about the overall schematic and/or the specific components I've selected.
    Any suggestion is welcome.

  2. BobK


    Jan 5, 2010
    I cannot open your attachment.

  3. reviser


    Sep 26, 2013
    Maybe now you'll see it

    Attached Files:

  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Your design looks pretty good to me.

    You should have decoupling capacitors on the inputs and outputs of the 78xx regulators. I'm sure you knew that!

    I have a few other suggestions but I have little experience with H-bridges so please take my comments with a grain of salt.

    The IR2110 looks well-suited to this application but the data sheet doesn't have any application guidelines. Is there an application note for this device? I notice you've added diodes across the gate resistors; these are a good idea but they're not shown in the sample schematic in the data sheet.

    The diodes across the gate resistors should be fast. 1N4007s turn off too slowly. Also they may need to be rated for more than 1A. The data sheet claims 2A positive and negative output current from the drivers but obviously this current does not flow continuously, so I guess any diode with a peak current comfortably higher than 2A should be suitable.

    This also applies to the diodes from VCC to VB. They need to be fast. Something like a 1N5819 would probably be suitable.

    The MOSFETs you've chosen have a maximum Rds(on) of 14 milliohms. At 10A they will drop 0.14V each (1.2% of your total voltage will be lost) and have a static dissipation of 1.4W. I would probaby go for devices with lower Rds(on) values. I did a search on Digikey and found several NXP devices with Rds(on) figures in the range 4~7 milliohms for half the price of the IRFZ48N. They also have much higher power dissipation specifications.

    Also, you should tell us what PWM frequency you're planning to use.

    Again please take my advice with a grain of salt.
    Last edited: Sep 27, 2013
  5. reviser


    Sep 26, 2013
    @KrisBlueNZ, thanks for you explanation and suggestions.
    I'll do some research and see if I can find components that suits your suggestions on my local distributor.

    The PWM I'll use is arround 500HZ.
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    I can see why you call yourself "reviser" ;-)

    Edit: The "DELETED" and duplicated posts that I was referring to are now gone... And I can't delete this post! Now I'm the one that looks like the "reviser"!
    Last edited: Oct 1, 2013
  7. Fish4Fun

    Fish4Fun So long, and Thanks for all the Fish!

    Aug 27, 2013

    500hz is pretty slow. Make sure to read AN-978 from IR, it works through calculating the boot strap caps based on switching frequency. I have run into real trouble trying to use the H-Bridge HS drivers by neglecting to heed the 30 pages of information in AN-978. Even with careful attention to detail there can be un-forseen troubles. If this is a production project, then it is like well worth your time to prototype and debug these chips, but if this is a short-run or one-off, you are likely far better off to simply get a small 12V transformer and a bridge rectifier and create a Vcc + 12V floating rail, then use optoisolators to switch the high side (it turns out there is nothing particularly difficult about switching the low side, lol).

    Good Luck!

  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Good advice Fish.
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