UCC39002 / Working at no load

Hello Kuramochi-san

The UCC39002 can force current sharing best at high loads where it is most important to be able to share the load and equalise the heating effects across multiple modules in the sharing system - especially so if the load current is greater than a single module can supply.

At light loads the heating effects are not so important so it is not as important to share the load current equally.

The main reason for the unequal current sharing is probably that the errors due to differences in the offset voltages in the amplifiers in the various UCC39002 devices become more important at light loads. At high loads these offset voltages don't create a significant imbalance in the current sharing but at light loads the offset voltages become comparable in magnitude to the real current sense signal and an imbalance is the result.

The UCC39002 can achieve better than 1% Current Sharing accuracy at full load. The error amplifier has a very low offset voltage (±100uV) but at light loads the CS signal will have a similar magnitude.

Regards
Colin