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MOSFET is not turning off need help

  1. Mar 26, 2012 #1
    hello everyone,
    I am designing Single ended primary inductor cell(SEPIC) converter. the objective is to get output voltage from 5V to 20V and 1 A current when we change the duty cycle of the pulse supplied to gate of MOSFET. when i simulated the circuit in proteus MOSFET is unable to turn off. I researched about snubber circuits as well but it didn't help me. Is there any snubber circuit for SEPIC converter? My calculation and simulation results are attached with it. please have a look and please help me.

    thank you

    Attached Files:

  2. jcsd
  3. Mar 26, 2012 #2
    That's a big circuit. I'll solve it but it will take time. So, be patient. OK?
  4. Mar 26, 2012 #3
    ok thankyou
  5. Mar 27, 2012 #4
    I've simulated your first circuit in pspice and I don't see any problem.
    However the output current I got was 35mA.

    Below is the SPICE code I used.
    The diode and mosfet models are taken from datasheets.

    Attached Files:

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