Hi Team,
What is the impact of negative temp. coefficient of BJT on switching effects in case of using UCC28722?
Is there something incorporated in the IC to counter that?
Regards,
Harmeet
Harmeet,
The ucc28722 dynamically adjusts the base current from DRV from 19-mA to 37-mA depending on the peak current in the BJT. At higher temp, higher hfe, higher peak current, the drive will change toward its maximum.
From a protection standpoint this device has cycle-by-cycle peak current limit so it will prevent current runaway.
One design consideration would be to be sure to size your transformer for the max power st highest operating temperature. In this way you will maximize the frequency of operation at full load, max temperature to use the full dynamic range of the IC's control. Be sure to use the excel design calculator from the ucc28722 tools folder on Ti.com.
I also recommend to review this app note:
Regards
John
