I am designing a single phase SPWM inverter as a project. I am using IRF740 as MOSFETs (all N channels.) My low side MOSFET keeps getting shorted.

I have checked through DSO - there is no cross conduction as I have applied a dead time using Arduino programming.

I have tried everything but I can't figure out the problem. My gate driver IC is a TLP250. I am using a separate DC supply for my gate driver and my pin 5 of lower side MOSFETs are connected to the (-ve of 10 V supply) and pin 8 is connected to 10 V. My high side MOSFETs (pin 8) are connected to 10 V and pin 5 is connected to source to drain of half bridge inverter.

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  • \$\begingroup\$ Welcome! Please show Vgs and Vds waveforms of top and bottom MOSFET. What switching frequency are you running? \$\endgroup\$
    – winny
    Commented Apr 14, 2023 at 11:00
  • \$\begingroup\$ Could you draw in the forward-biased diode? \$\endgroup\$ Commented Apr 14, 2023 at 13:09
  • 2
    \$\begingroup\$ With the basic mistakes you are making, you should not be working with 240V yet. It's dangerous. \$\endgroup\$
    – DKNguyen
    Commented Apr 14, 2023 at 14:06
  • \$\begingroup\$ My SPWM switching frequency is of 10 Kilo hertz. I will share the Vds graph soon, Here is my Vgs Graph. \$\endgroup\$ Commented Apr 14, 2023 at 21:03

1 Answer 1


You can't have common 10 volt supplies to the upper MOSFETs because of the way in which they switch independently with their respective sources rising and falling out of phase with each other.

Only the lower MOSFET drivers can use a common DC supply. In your circuit you need three supplies that are galvanically isolated from each other: -

enter image description here

Red, blue and green need to be independent supplies. Red and blue need to be sourced from an isolated supply else, use a bootstrapped driver instead of the TLP250.

In case you are following what I said above, please be clear in your diagram as to how the drivers are independently powered and show those power supply circuits.

The forward biased diode note on each upper supply doesn't make sense.

You should also note that the minimum recommended operating supply for the TLP250 is 15 volts and, you appear to be running them at maybe 10 volts (if your power supply anomalies were sorted out): -

enter image description here


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