MCU Driving a 20A+ MOSFET

Discussion in 'General Electronics Chat' started by kaneneville, Nov 6, 2012.

  1. kaneneville

    Thread Starter New Member

    Mar 7, 2009
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    0
    I want to drive a power mosfet for a 35V 20A+ buck converter by a atmega88. The frequency will be around 200kHz. I found the TC4431 and TC1411N are able to drive such a big power FET. Is there any other way to drive the FETs ? Can I use a Optocoupler for this application?
     
  2. kaneneville

    Thread Starter New Member

    Mar 7, 2009
    9
    0
    Schematic is just like the attached circuit from Microchip application note. My goal is to build a MPPT solar controller.:D
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,790
    There are two problems with an opto-coupler.
    1. Delay
    2. Parameter variation with time, specifically CTR
    Depending on the frequency of the PWM control the 3-5 second delay might affect the behavior of the MOSFET switch. The big problem for a MOSFET drive is charging and discharging the usually large gate capacitance. Delays in the gate waveform can lead to large current flows in the channel potentially destroying the switch.

    CTR the current transfer ratio tells you how much current the output can sink for a given diode current. Typical opto-isolators will have a value from 20%-300%. Whatever value the part has when it is new it will get worse over time.

    The circuit you want to drive the gate has to minimize the amount of time between ON and OFF. This will determine success or failure of your design.
     
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