Connect with us

P-Channel high side gate drive for 150Vbus BLDC motor drive

Discussion in 'Electronic Design' started by Mook Johnson, Apr 16, 2007.

Scroll to continue with content
  1. Mook Johnson

    Mook Johnson Guest

    Gents,

    I've seen several app notes showing using complementery N/P channel fets to
    drive a brushless DC motor with a low bus voltage (say 12 - 80VDC).

    I have an application that has a 150Vbus. Is there any reason I could not
    use a 250 - 400 watt P-channel with appropriate currnet rating?

    Id the appnote stop at 80 volts because the P-channel devices of the time
    were wimpy and not desired?

    I know I could use all n-channels but the floating gate drive is getting to
    be problematic due to the long duty cycles. It can be done and I'm
    investigating a small footprint solution.

    My problem is that the application is at very high temperature (>150C) and
    the standard "easy" answers don't work. (IR2110 or optocouplers). The next
    step is gate drive driving a carrier through the transformer and
    demodulating it on the other side.

    Seems like if it could work, a P-channel high side drive would be a better
    choice.

    What are your opinions on complememtary motor drive for a 150Vbus brushless
    motor driver.
     
  2. I'm sure you mean volt, not watt.

    A quick look at Farnell's site (which isn't the best-stocked, but has all
    the jellybean stuff) shows a single 250V P-Channel MOSFET, and that's a TO92
    device. After that they havbe only 100V parts.

    I don't know what makes it so hard to make decent P-channel power MOSFETs.
    Maybe it would be possible today, but there's no market because everybody
    has settled for N-channel only with floating high-side drivers.
    Go bipolar? Oh... just checked. Not much luck there either.

    My hunch is that even if there are high-power, high-voltage PMOS or PNP
    devices out there, they might be single-sourced and expensive. Personally,
    I'd definetely opt for all-NMOS and somehow wiggle my way around the other
    problems.

    robert
     
  3. John  Larkin

    John Larkin Guest

    High power, high voltage N-channel fets are cheaper and more
    available.

    Drive is easy: use a cheap potted dc-dc converter to get floating
    power, then an optoisolator and a chunky gate driver; maybe $12 for
    the whole thing.

    John
     
  4. Winfield

    Winfield Guest

    This approach is a bit more complex, but popular and very
    inexpensive.
    There are some reasonably-good 400 to 500V p-channel power
    MOSFETs, but as you say, they aren't as good as n-channel
    (e.g. a poorer Rds-on * price, etc., figure-of-merit). But
    if the O.P. feels the need... He may think p-channel-drive
    circuits are more simple, but after he's added the ability
    to drive high currents into the p-MOSFET gates, I dunno.
     
  5. John  Larkin

    John Larkin Guest

    Yup, I'm still using lots of the 300-watt Ixys parts you suggested.
    They're on the heatsink beast whose photo I posted to abse last week.

    But it seems to me that there wouldn't be much difference in gate
    drive complexity. You wouldn't want to capacitively couple directly
    into a p-channel gate, not with the source that far off ground. I
    guess if you had multiple p-fets working off the + rail, h-bridges
    maybe, you could share the dc-dc converter.

    Oh, did you ever used the drift step-recovery gadgets I sent? The
    project is dead on my end (ie, all the lawsuits are pretty much
    settled) so I don't consider the stuff to be secret any more.

    John
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-