mosfet gate driver IC

Discussion in 'General Electronics Chat' started by dmta, Jun 10, 2013.

  1. dmta

    Thread Starter Member

    Mar 24, 2013
    32
    1
    Hi all,

    Can you recomend me a MOSFET gate driver IC for me from Texas Instruments. This is for a H bridge to control a brushed DC motor. I am using IRF530.

    Regards
     
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
    1,531
    Not enough information to help you. A schematic of what you are wanting to do is needed. Also the voltages you. are working with.
     
  3. dmta

    Thread Starter Member

    Mar 24, 2013
    32
    1
    Thank you for replying shortbus!!!!!!!!!!!

    This is the schematic. I am ready to ut the PWM inputs to the lower MOSFETS if needed.

    untitled.JPG
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
    1,531
    Couple of things about the circuit. And I'm no real expert, just a hobbyist, so could be wrong.

    Why are you using those mosfets? Reason I ask is, the Rds is pretty high compared to other new mosfets. The higher Rds will mean more heat and voltage drop.

    You have the PWM on the high side(HS) mosfet. It is usually better on the low side(LS) mosfet. When on the HS it is called hard switching, when PWM is on the LS its called soft switching. Soft switching is a better way to go.

    And lastly, why a Texas Instrument driver? Your using International Rectifier mosfets. TI is good, but IRF has a better selection of drivers.

    What voltage are you going to use for the gates of the mosfets? What switching frequency for the PWM?
     
  5. dmta

    Thread Starter Member

    Mar 24, 2013
    32
    1
    Thank you for your suggestions shortbus.

    I used the 530 because I have a couple of them at hand. I searched for driver ICs and found some. The thing is unfortunately where I live (Sri Lanka) those parts are not available. TI is the only place where they give out free samples to our country. Very sad situation !!!!!!!!!!!
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
    1,531
    This is why putting your location in your member profile is good, helps us help you.

    TI doesn't have a very good selection of drivers. Futurlec.com ships to and from Asia, maybe look there and see if they can help. http://www.futurlec.com/OrderingInformation.shtml Have a look and pick ones you think will work. Post and I or some one will check for you. The "free" parts aren't always free, after you pay shipping and any import fees.

    The last drivers I got were from Fairchild they have a similar selection to the IRF ones.
     
  7. dmta

    Thread Starter Member

    Mar 24, 2013
    32
    1
    Hi shortbus, thank you for the reply.

    I went through the HS and LS concept and as I understood it, to switch ON the LS mosfet you need the specifiied Vgs value which in this case is about 10V. To switch ON the HS mosfet you need that 10V(Vgs) plus the supply voltage to the H bridge. Am I correct ?

    There is another thing which is, all these drivers come with a specified output current. I'm assuming it is the current needed to charge and discharge the gate at high frequencies. How do I calculate it for my application. The PWM frequency is about 10kHz.

    Regards
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
    1,531
    First, I made a mistake on the hard and soft switching statement. You were correct in the way your schematic showed, the PWM on the high side. Hard switching is when you switch both high and low at the same time. When using a half-bridge driver the PWM switching of the high side will allow the recharging of the boot strap capacitor. This is needed to keep the motor on for long times of use.

    The half-bridge driver (two needed for a H-bridge) uses what is called a "boot strap circuit" to give the high mosfet its gate voltage. The boot strap is a diode and capacitor in series between the voltage supply of the drive and the source of the mosfet.

    If you just want to do a H-bridge simply or if the the motor will only be reversed occasionally there are other ways of doing it...

    One is to make your H-bridge with P mosfets as the high side switches. Google will show many circuits. Doing this will not need any half bridge drivers.

    Another way is to use one N mosfet for the low side and PWM. With the high side switches being either relays or an actual toggle switch.

    About the different amp ratings on drivers, I always choose the highest amp rating available. This way you only need to keep one part number around. The mosfet will only use what it needs to turn on, and higher amperage will turn it on faster. This means less heat in the mosfet from the switching. Since most of the drivers cost are similar and size is the same just having one part on hand makes sense to me. Others may disagree though.

    Again I'm sorry about the mistake on the soft/ hard switching. Here are a couple of application notes that might help with understanding the boot strap circuit.
     
Loading...