Hello All,
I have a question abouzt the UCC3595. We using it at our 5kW Power supply and it work in Voltage Mode (nor current feedback for the Ramp, but at moment I also try to operate in current mode). For Compensation we using external Operationampilifier circuits. The supply can change his output voltage and output current from 0% to 100%. Theoretical all work fine. But I found one problem, At some load points I get hard problems with switching noise, first I was thinking is is a problem with may layout and the compensator, any way (I can not exclude the Layout at this moment, but I will make a redesign after reading SULA501).
No I have make it very simple for testing and evaluating. Instead of my compensation and control circuit, i using a simple resistiver divider to set the duty cycle to check the behavior at different load points. Now I found one point which I not can easy explain.
If I change the control voltage from 1.33V up to 1.35V I get an jump at the duty cycle on time from 1.3µs to 3.9µs (periode time is about 12.5µs). At the voltage range lower 1.33V and higher then 1.35V there is no jump I can easy adjust the duty cycle. This is a very smal range of set voltage, but it has a high influence of the output.
If you want I can also send you some more information about my circuit. I can also send you some scope picture of the above descripted behavior.
I hope you can help me with this issue, or you can give me a advice or idea which is the possible cause of me problems.
Best regards, and a nice weekend.
Sascha