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Low side mosfet driver for half bridge — Parallax Forums

Low side mosfet driver for half bridge

BitsBits Posts: 414
edited 2011-11-02 12:53 in General Discussion
Anyone have a suggestion for a low side N-chan MOSFET driver that does not require the source to be tied to ground? I am considering the PVI5033RPBF, but its rather expensive. here is a peek at the test schematic.

*Nodes A,B, and ref control the half bridge polarity - the 2 mosfets will be either fully on or fully off. Amp node is a circuit that uses a transistor with feedback to control current through the half bridge.

Attachment not found.

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-11-02 08:37
    If you don't need super-fast switching, you could use a photovoltaic optoisolator like this one:

    In fact, you could use one in both the top and bottom sides, with nMOSFETs in each.

    -Phil
  • BitsBits Posts: 414
    edited 2011-11-02 08:39
    Phil

    That link is dead please re-post.
  • BitsBits Posts: 414
    edited 2011-11-02 08:43
    Is this it Phil?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-11-02 08:44
    Try it now.

    -P.
  • BitsBits Posts: 414
    edited 2011-11-02 08:52
    Looks great, here is what Ill be testing soon - ordering the parts today. Thank you Phil.:lol:
    Attachment not found.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-11-02 09:01
    'Hope it works out! Why did you cross the output wires from the isolator, though? Pin 6 should go to the gate, and pin 4 to the source.

    -Phil
  • BitsBits Posts: 414
    edited 2011-11-02 09:17
    Opps that is a good catch. Ill switch that around now so I don't make the same mistake twice.
  • AleAle Posts: 2,363
    edited 2011-11-02 11:47
    Just wondering if a small transformer can be used instead, I mean if the frequency allowed by the optoisolator is too low.
  • Capt. QuirkCapt. Quirk Posts: 872
    edited 2011-11-02 12:34
    For about 50 cents you could use a 74ac08, 74hc08 depending on your needs. Just tie the inputs together.
  • BitsBits Posts: 414
    edited 2011-11-02 12:53
    Ale:
    Thanks for the suggestion but I am just using DC to turn on the mosfets on / off so the freq = 0Hz.

    Capt:
    Capt. Quirk wrote: »
    For about 50 cents you could use a 74ac08, 74hc08 depending on your needs. Just tie the inputs together.
    I don't think this would work since I need to have a voltage greater than 5 on the gate with respect to the source.
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