Fuel injector driver/input clamping circuit

Discussion in 'General Electronics Chat' started by oscaryu2, Jul 18, 2015.

  1. oscaryu2

    Thread Starter New Member

    Jul 18, 2015
    1
    0
    Hi there,

    I've got this following schematic and was trying to figure out what the two diodes do:

    [​IMG]

    I believe they're for input clamping (the input is from a thermistor), but I wasn't sure. Thanks!

    Also, in the following fuel injector circuit:

    [​IMG]

    There is no freewheeling diode. I assume this is because we want the fuel injector to close quickly (and NOT freewheel). Thus, would you simply just size your FET Vds rating to whatever the peak comes from the injector's inductive spike?

    Thanks!
    Oscar
     
  2. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    1) yes. They are clamping diodes.
    2) no, the mosfet is internally clamped.
     
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