while that aspect has to be debated, i feel, it better to have fewer mosfets of higher capacity , rather than more mosfets as the gates would be common increasing the total capacitive load.masifshahzad said:Thank you so much for your replies.
OK let me redesign the mosfets driver circuit and check it again.May be the problem is with 4047 ic or the 7667 ic. I let u know by sending the new driver schematic.
One thing to ask is can i use mosfet as a pre-driver to drive these 2 sets of parallel mosfets. that pre-driver mosfet will be drived by the mosfet driver icl7667.????
Thanks.
After power off, only a small remanent flux is kept in the transformer. It's polarity actually plays a certain role,One suggests me to short the output or input winding of transformer after switching OFF the circuit to discharge the saturated core.
This way, you should be able to fix the problems. I suggest an overcurrent detection fed to the PIC as additional option.Yes i m redesigning the PWM circuit using PIC microcontroller.
Perhaps you need to have a minimum of double or little more Vds than the working voltage. The auxilary supply serving the electronics including gate drive should have adequate capacity to prevent under drive that could cause temperature raise.masifshahzad said:Hi,
@ MVS SHARMA - You are right but problem is that high rating mosfets are usually not available in my area and if available then they are so much costly. IRF3205 is available, its Id is 110A but problem is with Vds which is just 55V which is quiet near to 48V. Can you suggest any high rating mosfet with high Id, Vds and low on resistance???
Added after 6 minutes:
Hi,
@ FVM - .......
Thanks.
Weak gate drivers won't explain why the power stage is blown at no load. I fear, it may a problem of high inrush currents due to core saturation. Starting the inverter operation with a halfwave of 10 ms duration implies doubled flux compared to periodic operation. To avoid saturation, the first halfwave should be shortened to 5 ms.
Or use any other means to limit the inrush current, e.g. a current limiting resistor. Furthermore, it seems appropriate to have some kind of overcurrent shutdown for a high power inverter.
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