24-48v mosfet driver circuit

Discussion in 'The Projects Forum' started by niclatrique, Mar 22, 2006.

  1. niclatrique

    Thread Starter New Member

    Mar 22, 2006
    3
    0
    Hi everybody.

    I work on a stepper motor driver circuit. I decided to use an L297 stpper controller associated with two MOSFET H-bridges.

    As I'm new to MOSFET driving circuitry, I'd like to have some ideas on how to drive them without using a dedicated mosfet driver IC. Is there a way to achieve this using cheap discrete components.

    The high side of the H-bridge works with P-channels fets and the low side with N-channel fets.

    Does anyone have a schematic ?

    Thank you so much

    Nic
     
  2. Papabravo

    Expert

    Feb 24, 2006
    9,905
    1,723
    If this is your first experience with stepper motors and drive circuits then I would recommend keeping your life simple; use the L297. As you learn more about its properties and the properties of the devices, you can experiment with alternatives.

    The problem with discrete solutions is that you have an additional set of issues to deal with that have already been solved by the IC designer.

    In business:
    1. First make it work
    2. Second make it cheap
    3. Third make it elegant

    Don't aim for number 2 while missing number 1
     
  3. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    First, is your motor supply ranging from 24V to 48V? It would be much easier to design the driver circuit with a fixed supply voltage.

    Second, what is your motor current rating? Do you need to provide a dead-time? Have you selected any MOSFET yet? The gate drive depends on the MOSFET specifications.

    If the L297 output has sufficient current and voltage rating and your motor does not need large current and no dead-time, you could drive the MOSFET directly through a resistor. You could use a small BJT, like 2n3904 and a pull-up resistor to provide the current for small MOSFETs or for large ones a totem-pole BJTs.
     
  4. niclatrique

    Thread Starter New Member

    Mar 22, 2006
    3
    0
    Thank you guys for answers.

    I've chose the L297 because of the simplicity and all the pain it'll save me in the design of the PWM current-chopper. I've chose the MOSFETs for two reasons; they are cheap and I can supply a voltage higher than those L298 darlington based stepper drivers.

    Why would I want to make it work under 24 AND 48 volts ? We are two friends building each a different CNC. My friend want it at 24 and I want it at 48. As we'll send only one design to the PCB shop, here why I want it like that.

    If you all tell me that I should use mosfet drivers instead of making it like "made-on-the-corner-of-the-table-on-sunday-with-radio-shack-parts", then I'll go for it. But if there is a way to achieve something elegant with discrete parts then I'll go for it.

    Here are the MOSFET I bought on Digi-Key:

    IRFR9014
    IRFR014

    Once again, if somebody has a chematic or scratch to start with, I'd appreciate

    Thanks

    Nic


    If you want to fly like an eagle, don't hang around with turkeys !!
     
  5. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Because the MOSFET driver circuits would be different. If you have no idea why, maybe you should think on how much gate voltage a MOSFET can stand and current differences for the same circuit supplied at 24V and 48V. Anyway, you would hit the same problem even if you use a MOSFET driver IC.
     
  6. niclatrique

    Thread Starter New Member

    Mar 22, 2006
    3
    0
    I've been on the microchip site to have a look at their fet drivers. Am I correct or there is no fet driver which can support a voltage over 30v ??

    What can I do in the case of a supply of 48 volts ?

    thanks

    nic
     
  7. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    For discrete design, limit the gate voltage to 12V or so. A few zeners and some ingenuity would do the trick.

    For MOSFET driver IC, you could always find one that supports supply voltage of 48V, with some luck you might find one. Although, I've never seen one and therefore I can not help you.

    Edit:
    You might want to talk to the guy in this thread. He's doing CNC with step motors as well. I'm sure he wouldn't mind showing you his MOSFET driver.
     
  8. fraujansen

    New Member

    Apr 1, 2009
    1
    0
    Hi Niclatrique!
    I want to make also a mosfet driver for somekind the same circuit. It's also a H-bridge. The high side of the H-bridge works with P-channels fets and the low side with N-channel fet, like yours. It generates a sawtooth signal to move a motor.
    The motor works with 28V.
    The MOSFETs should be able to switch very fast. Of which factors does it depend?
    if it does help ask me for a schematic of my circuit. Thank u.
    Can you send me your schematic so i can learn of how you have done it?
    thank u very much
    daniel
     
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