MOSFET burning / need help

Discussion in 'General Electronics Chat' started by ratheeshvaram@yahoo.com, Nov 10, 2013.

  1. ratheeshvaram@yahoo.com

    Thread Starter New Member

    Nov 10, 2013
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    0
    hai every one,
    I am designing a variable inverter, output- 100V-300V, (40Hz-70Hz) 10W and input-12V,1A. for this I chose one DC-DC converter and DC-AC converter.
    my first step is to get a max. DC voltage from DC-DC converter, give the output of this converter to the supply voltage of MOSFET in DC-AC converter Hbridge, provide a SPWM signal according to the desired output AC voltage, and finaly design a filter to get pure AC wave.

    in DC-DC converter: I use pushpull topology (50Khz) , PIC16F716, IR2113 (driver), IRF3205 (MOSFET). the outpout of transformer is fed to the bridge rectifier (UF4007) and finally to a filter 47uF/400V. I got the output as ~400VDC, when i connected an LED through 200K resistor.
    -duty cycle is 50%.
    -10K is used form gate to ground
    -using a 0.01uF and 56ohm (snubber) in parallel to primary.

    In the DC-AC converter: I use full bridge topology (30KHz), PIC 16F716, IR2113 (driver), IRF830 (MOSFET). I use only 60 devision for sin wave generation. when I am connecting 12V in place of MOSFET supply, I am getting a SPWM signal across a 1K resistor, and nearly 8V AC on multimeter.

    But when I connected the DC-DC converter output to MOSFET supply,in the very next moment the two MOSFET in one side of H Bridge burned.
    I used 22uF/50V (electro) in parallel to 0.1uF as bootstrap cap.
    -the load is 1K resistor
    -the ground is common for entire circuit.
    -12K is connected from gate to source.
    -no snubber connected.

    friends what will be the reason for MOSFET burning...???
    is any one feel something wrong in above explanation???
     
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  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    The image is too small to see anything.
     
  3. ratheeshvaram@yahoo.com

    Thread Starter New Member

    Nov 10, 2013
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    ........................
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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    For schematics and PCB. Use the PDF format if you can, and try to avoid using bitmap format. I use this free tool http://sourceforge.net/projects/pdfcreator/
    It is a PDF printer driver for Windows. Then you want to to create a PDF. Just print out documents to a PDF file.
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    It looks pretty good. Just a couple of comments:
    22Ufd for the boost cap is big, but then you have the 12k pull downs on the high side FETs. I would get rid of R7 & 10 and then resize the bootstrap cap. But having said that I doubt that is your problem. The fact that they were on the same side of the H suggests they were both on at the same time. The diode resistor combo in the gates looks like an effort to prevent shoot thru, but 22 ohms may be to small. If you can add a small resistor to measure the current in the bottom of the H you could see how it looks with 12 volts if you have a scope.
     
  6. ratheeshvaram@yahoo.com

    Thread Starter New Member

    Nov 10, 2013
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    0
    thank u,
    Ok I will reduce the cap value, eliminate gate to source resistor fo high sigh side and reduce the gate resistor value(27ohm)..
    - what about the Ground???
    - can I connect all together?
    - ie, all ground of dc dc converter and dc ac converter?....
     
  7. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I would leave the gate resistor as it is (27 ohm) maybe make it a little bigger.
    Yes all grounds together is good. Most important if you can do it is to see how much current is being drawn when the high side is turning off and the low side (on the same side of the H) is turning on.
     
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