Mosfet always broken in Inverter circuit

[knec]

mosfet inverter circuit

Hi all,
I have a design about inverter with full bridge topology,and use 60kHz for inverter frequency.Why mosfet always broken when i test with load at maximum current.I would like to know how is critcal point of design.

Thank you,

K.Nisit

 

[zx_sa]

inverter circuit mosfet

Without more specifics about the load and maximum current and also the FETs, it's difficult to say.

Obviously if the FETs blow, it's because the current (heat) is too much for them to handle.

The reason could be the frequency. At 60kHz you may find that the time it takes for the FET to switch off is rather long, and you may switch on the other FET (in the H-bridge pair) before the switch off is complete.

Try to ensure more dead-time -- this is a short time period when BOTH FETs in the H-bridge pair are switched off.

Other than that, either use FETs with higher current rating, or stick a bigger heatsink on your FETs. In power electronics you always need to do a proper thermal design as well!