Hi team,
The Vcs threshold is too large, so the power loss of the current sense resistor is large. We want to check whether we can add a bias to the Vcs to make the power consumption lower. For example, resistor divider Vref or Vin. Do you have some suggestions about the solution which is ok to be used? Thanks.
Hi Frank,
The Vcs threshold for the UCC2897A is 0.5V and yes you can add a DC bias to the CS input in order to achieve a lower current limit.
This method is described in the UCC180x data sheet:
The problem with using this method of power loss reduction is that it makes the system more sensitive to noise pickup.
There is already an RC filter on the CS pin to filter out switching noise and if you add an offset you will probably need to reduce this filtering.
A better method perhaps is to consider using a current transformer.
You can replace the shunt resistor on the source with a current transformer and the sense power is reduced from Rcs*Ics^2 to Rcs*Ics^2/N
where is is the turns ratio of the current transformer
Regards
John
