Right Mosfet for my project

Discussion in 'The Projects Forum' started by scelesticsiva, Feb 14, 2014.

  1. scelesticsiva

    Thread Starter New Member

    Nov 29, 2013
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    I am doing my project on multilevel converters and i have no idea,how to select the appropriate MOSFET for my converter.Is it enough if i measure the voltage across the mosfet in simulation and get the ratings based on that?

    Input voltage =16.5 v
    Output voltage = 94 v
    Peak Voltage across switch = 33v
     
  2. wayneh

    Expert

    Sep 9, 2010
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    3,060
    No, current is usually the most important criterion. Peak voltage certainly matters. But it's the peak and continuous current rating, and the power dissipation requirement, that usually dictate the minimum MOSFET specs.

    Also, the gate-source voltage required to fully turn on the MOSFET is important. Regular MOSFETs need about 10V whereas logic level MOSFETs need <5V to reach their minimum Rdson.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    Efficiency also depends upon the ON resistance of the MOSFET so that needs to be considered, along with the voltage rating, current rating, and Vgs voltage needed to fully turn it on.
     
  4. #12

    Expert

    Nov 30, 2010
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    You must also include a, "safety factor" when deciding on a transistor. Simulated and real world voltage measurements are typically steady state conditions. Transient voltages have killed many transistors.

    Please go to, "User CP" and add what country you are in so we will be able to look up parts if you need them.
     
  5. scelesticsiva

    Thread Starter New Member

    Nov 29, 2013
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    0
    @wayneh i have planned to interface the converter with a PV module,current rating of the module is 0.6 A,now how do i decide the rating of MOSFET?
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,060
    If you have no other power source than the panel, and that 0.6A rating is quoted at a short circuit (ie. a real maximum), then a 1A MOSFET should be fine. And easy to find. The panel might never supply more than 200mA under actual load conditions and that would leave you a nice safety factor.

    But to choose a MOSFET, you need to know what gate voltage you have available to control it. If you don't have a good 10V, you'll need a logic level MOSFET.

    A schematic of what you are thinking about would get you better feedback.
     
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