UCC28070: Can i use this chip as a single channel PFC controller, and what happens in light load when it goes into DCM?

Hi

Why do you want to use the UCC2070 as a single channel PFC ?

TI has a more cost competitive solution in the UCC28180 8 pin CCM controller,

Regards

Peter

Hi

Thankyou. The problem with the UCC28180 is that it doesn’t sense the half sine HVDC bus…as such, when the UCC28180 goes into light load, then it goes into DCM and the power factor is not good. The power factor also deteriorates at full load near the zero crossings as it goes into dcm there too.

As you know, if the HVDC bus is not sensed, then it is simply not possible to make the current track the voltage in a close way, when it goes into DCM

Also, the UCC28180 needs a diode on its ISENSE pin...this diode must have a vf > 0.438v and <1.1v over all temperature.....thats asking too much. So i dont believe we can use this chip.

Hi

Many customers use a 1N4148 type diode, the temperature range depends of course on the application but for most PFC's it does not go as low as -40C maybe -25C. The current in the diode is limited by the resistor from the RC filter so its usually 1 to 2mA during the inrush at turn-on.

The UC3854B is another single channel controller that you might find suitable,

Regards

Peter