UCC28880 noise

Elliott Yang

Prodigy 60 points

Other Parts Discussed in Thread: UCC28880

Hi all

I have made one PCB to get AC110~220V to DC5V/100mA by using UCC28880.

Here is my schematic:

The 5V is OK, but the noise(sound) is annoying. I think it's coming from L2.

I don't know what's going on this circuit, Could any one tell me?

Thanks,

Elliott

over 10 years ago

0 Elliott Yang over 10 years ago

Prodigy 60 points

Here is the DRAIN pin waveform:

0 Bing -PSC Lu over 10 years ago in reply to Elliott Yang

TI__Intellectual 1615 points

it appears you are switch at about 6khz. this is at the audible frequency range and this is why you hear the audible noise. you can reduce the inductor value to push your switching frequency higher to avoid the audible noise. at lighter load, you'll enter audible frequency again. hopefully your load is stable and you can avoid audible noise. at higher output voltage, due to the fast discharging rate, it is much easier to achieve no audible noise.

0 Elliott Yang over 10 years ago in reply to Bing -PSC Lu

Prodigy 60 points

At the low side Buck, 5V output is NOT recommended ? because of the switching frequency can't be higher enough ?

0 Bing -PSC Lu over 10 years ago in reply to Elliott Yang

TI__Intellectual 1615 points

you can adjust the switching frequency through different inductor value. This the way to avoid audible noise for low voltage output

Power management

Power management forum

UCC28880 noise