Hi,
I designed a DCDC converter using lm5088-2 with specs:
Vin: 44-56V
Vout: 30V
Iout: 1.6A
The converter regulates properly when I apply a load ranging from 0.01A to 1.6A at any input voltage.
however at no load, it only regulates at 23V.
here are some comparisons between significant values at loaded and no load condition.
Vcc wrt gnd: Same
Vboot wrt Vsw: 7.4V (L) drops to 4.3V (NL)
Vss wrt gnd: 1.44V (L) drops to 1.09V (NL)
Frequency: Same
Venable: Same
Vfb: adjusts accordingly when Vss drops -- 1.28V (L) drops to 1V (NL)
Vcomp: 4.8V (NL) drops to 2.2V (L)
I already placed an Rramp as advised in another thread, but it does not improve matters.
It seems that the problem resides in the Vss level. As I understand from the datasheet, the Vref will revert to the Vss level once it drops below 1.205V. Any ideas on why the Vss drops?
Any advice on additional tests?
Thanks