Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

MOSFETs pulsing at a frequency out-of-phase

  1. May 28, 2017 #1
    <Moderator's note: Spin-off from a related thread: https://www.physicsforums.com/threads/h-bridge-diodes-or-rather-the-lack-of.915992/>

    I've always wondered: What do people usually use for gate drivers for mosfets and H-Bridges?
    For example; say I wanted to have a couple MOSFETs pulsing at a frequency out-of-phase with each other, what would I use to drive the gates?
    Last edited by a moderator: May 29, 2017
  2. jcsd
  3. May 29, 2017 #2


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    A PIC microcontroller would be ideal
  4. May 29, 2017 #3
    Ah, I was afraid of that, no easy way.
    Are there chips you can get where you can set an approximate oscillation frequency with resistors, to pulse on and off, and use that chip to drive a MOSFET or H-bridge?
    (That way I could just use a NOT gate to drive the opposite too?)

  5. May 29, 2017 #4


    User Avatar
    Science Advisor

    Google search for: 555 timer
    over 800 000 hits for data sheets and circuits
  6. May 29, 2017 #5

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    Learn basics of PWM by starting with a TL494
    that family has devices of any complexity you want but i've only played with the 494

    then tack behind it an H-bridge driver - any search turns up too many of them to comprehend.
  7. May 29, 2017 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    Sympathy. Personally I would think of it in terms of hardware. If the phase relationship is to be fixed and a simple fraction of a cycle then I would use a clock oscillator or n times the final frequency where n is a convenient value so that you can have a divider / counter with two output clock signals which are an integral number of fastclock periods apart. The two output signals are then as firmly bolted together as gear wheels, driven by the same shaft.
    The micro controller solution is a piece of cake if you already have experience of driving and programming the device. Could be time worth spending in learning but it would depend on when you may need to do something similar in the future.
  8. May 29, 2017 #7

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

  9. May 30, 2017 #8
    There are more says to control the H bridge and other SMPS - than there are topologies.

    As for the use of the Driver:

    The Switch's( MOSFET or IGBT ) gate needs more power or current than the controller can provide.
    The Switch's gate needs a different Voltage than the controller provides.
    Most systems use N type devices for both top and bottom and thus needing to offset the Gate signal to the relative Voltage of the individual switch,
    Provide isolation between the Controller ( sensitive) and the Power Electronics ( noisy)
    The gate circuit needs to be tightly controlled for best performance ( Long leads and runs to from the controller to the Switch are problematic) - the noisy Power Electronics environment needs small local system to help prevent interference from the switching events.

    there are others - TL-DR; POWER electronics and control electronics don't get along very well.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: MOSFETs pulsing at a frequency out-of-phase