Connect with us

Level shift question

Discussion in 'Electronic Design' started by David Grant, Jan 25, 2005.

Scroll to continue with content
  1. David Grant

    David Grant Guest

    I need to shift a PWM signal (switching freq - 300kHz) from (0 to 5V) to
    (-50 to -45V). Output is going into an IR2011 gate driver. Available
    supplies are +/- 50V, +5V and GND.

    I'm told I should be looking at using a PNP level shifting circuit, can
    anyone comment and elaborate as to what that is?

    Thanks,

    David.
     
  2. Ken Smith

    Ken Smith Guest



    ASCII art:


    VCC
    !
    /
    \
    /
    \
    !
    !/ e
    Signal ------! PNP
    !\
    !
    +-------- Load
    !
    /
    \
    /
    \
    !
    -50V
     
  3. Something like this (it also inverts) with R around 1K.


    +5V
    |
    .-.
    | | R
    | |
    '-'
    |
    |<
    0V/5V -|
    |\
    |
    |
    |
    |
    +-----------o -50V/-46V
    |
    |
    |
    .-.
    | |
    | | R
    '-'
    |
    |
    -50V




    Best regards,
    Spehro Pefhany
     
  4. Nico Coesel

    Nico Coesel Guest

    AFAIK there are gate drivers with integrated level shifters. You
    should look for those. If you connect the GND from the 5V to -50V, you
    can use 2 high side drivers.
     
  5. David Grant

    David Grant Guest

    This works well for no load, but when going into the gate driver input the
    signal amplitude shrinks to almost nill. Is something then fishy about the
    gate driver's input impedance?

    Dave.


    http://www.speff.com
     
  6. The IR2011 inputs have pulldown resistors- poorly characterized and
    temperature sensitive. If you use the ~1K resistors that I suggested
    it should work fine. If you don't like the ~200mW "on" power
    dissipation in the transistor, you can add a series resistor (maybe
    5.6K) on the collector to knock it down a bit.


    Best regards,
    Spehro Pefhany
     
  7. Ken Smith

    Ken Smith Guest


    OR

    You could, if you have the supply to do it, add a emitter follower pair at
    the MOSFET input.
     
  8. Fred Bloggs

    Fred Bloggs Guest

    View in a fixed-width font such as Courier.



    NON-INVERTING
    5V LEVEL SHIFT
    |
    |
    |\ 390
    |/ |
    |buffer |
    |cmos e
    | |/
    GND----+---------| 2N5401
    |\
    c
    |
    |
    /
    3.9K 1W
    /
    \
    |
    +-----> to IR2011
    |
    /
    390
    /
    \
    |
    -50V
     
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

-