UCC28950: Using another current sensing technique other than a CT

Hi Tony

The best approach is that shown in the schematic for the UCC28950 EVM - it's in the user's guide. If the input voltage is fixed then the current sense signal which is usually taken from the input rail can be scaled to give a current limit at an appropriate level. You need to scale the output of the current transformer so that it reaches 2V at the desired current limit point. This is the method used on the UCC28950 EVM. We use a current transformer because it is a low dissipation way to measure high currents. Note that as Vin increases and decreases then the fixed input current limit will correspond to an increasing and decreasing output current limit, for example 5% variation in Vin will give 5% variation in the output current limit point.

You could use a current sense resistor in the input line, but you will need an isolation amplifier and its associated power supplies, to gain up the signal to 2V peak and give you a ground referenced signal.

I hope this answers your question - please feel free to re-post if you need any further information.

Regards
Colin