Hi all,
i used a TPS54561 in my desing with following parameters:
Input Voltage 48V, Output Voltage 13.8V Output current 5A, Switching frequency 600kHz.
The converter works fine, until i reach a 2.5A at the output. Then the voltage drops near zero. The duty is about 30% when Input is 48V, output 13,8V / 1A, at the 2.5A point, the duty starts decreasing. I designed this to be at least 4A power supply, and i dont know where error can be. I tried change compansation, adding capcitors at input and output but with no results. The inductor is 47uH with saturation current of 9.5A and rated current 6.5A. Diode is 8A. I noticed one thing, that converter is not switching at 600kHz but instead at 374kHz and change in RT has no effect on the switching frequency.
At lower input or output voltage (Tried to change output divider if it helps), the converter starts limiting at the same point, around 2.5A.
The voltage at the COMP pin is around 1V at the 2.3A at the output. Then, it starts rising sharply and saturates at 2V, then converter is in curent limiting.
Thank you.
