data/text/DLP1/899515

UCC28950EVM-442: UCC28950 EVM-442 light load efficiency poor

Part Number: UCC28950EVM-442 HI sir I tested the demo board data and found that the efficiency is poor at light load . Because my design that fan is not working at light load In this case,the Phase-Shifted Full-Bridge MOS loss is very larger and breaking The actual test is as follows. Is there any way to improve it? Test data: Pin :17.4W Vout/Iout:12V/0.1A Pin :18.7W Vout/Iout:12V/0.2A Pin :19.8W Vout/Iout:12V/0.3A Pin :20.6W Vout/Iout:12V/0.4A Pin :21.6W Vout/Iout:12V/0.5A TKS

Hello The UCC28950 (and UCC28951) has a burst mode to reduce dissipation at light loads. Please check that the EVM is operating in Burst Mode at light loads. Also, check that the SR drives are disabled (OUTE = OUTF = 0V). You can increase the TMIN threshold so that the controller enters burst mode at a higher current level. I have run my EVM in my lab at no load continuously without any problems so your unit is behaving a little differently. Please check the above items and let us know how you get on. Regards Colin

HI Colin I have recheck EVM that has a burst mode and the SR drive is disable at light load(0.1A~0.5A) THE EVM at no load is no problem ,but if add load at 01~0.5A,you will be find that input w is very large and efficiency is poor Pls be check your EVM at 0.1~0.5 load Finally I will try to adjust the TMIN to improve it ?

Hello If you increase the Tmin value then that will increase the power level at which the EVM enters burst mode - Due to Covid-19 restrictions here in Ireland I won't be able to get into the lab for the forseeable future but I'd expect that my EVM behaves the same as yours. Let me know how you get on Regards Colin

Hello Just wondering if you had been able to make any progress on this - Regards Colin