UCC28880 audible noise

Elliott Yang

Prodigy 60 points

Other Parts Discussed in Thread: UCC28881, UCC28910, UCC28880

Hi All

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

But there has very annoying audible noise, I've checked L2 switch side, is it any problem here?

Reducing the inductor value doesn't work. Even I tested UCC28880EVM-616 (TI developed board), it's same problem....

Can anyone help, plz?

Here is my schematic:

over 7 years ago

0 Mike O' over 7 years ago

TI__Guru 65885 points

Hello Elliot,

I had designed with the UCC28881 and had the same issues. This a very inexpensive controller with an internal FET for buck applications. The peak current limit has a variation of 2.1 to 1.

To design for worst case you need to select the inductor based on the minimum peak current limit and the output current. The controller was designed to give packets of 62 kHz PWM pulses. If you design this way the controller will be delivering packets of energy at roughly a 50% duty cycle. The frequency of the energy transform will be 15.5 kHz. Which is in the audible range.

The only way that I found to reduce audible noise with this device is varnish the magnetics. You also may have to incase the magnetics in potting material. Gluing down the magnetics and components that might vibrate is also worth trying.

The other alternative is to switch to the UCC28910 which has an internal FET and a more accurate peak current limit. This device will still be susceptible to audible noise in this application as the load reduces.

Regards,

Mike

0 Elliott Yang over 7 years ago in reply to Mike O'

Prodigy 60 points

Hi Mike

Thank you for your kindly reply.

As you said, UCC28880/UCC28881 is low cost AC to DC converter without transformer. UCC28910 isn't suitable for us, sorry.

I tried to reduce the C12(1uF) to 0.01uF, the switch frequency was shift to 22KHZ. now I got a quiet product !!

Could I do that? Might be batter than Gluing down the magnetic components..

Regards,

Elliott

0 Mike O' over 7 years ago in reply to Elliott Yang

TI__Guru 65885 points

Hello Elliot,

You can decrease the Cfb capacitor to increase the switching frequency. As the load decreases the converter will enter the audible range.

The converter can also enter the audible range if there are variations in the peak current limit from what you are seeing in your prototype.

It still might be a good idea to varnish the magnetic just in case.

Regards,

Mike

0 uMin over 6 years ago in reply to Mike O'

Intellectual 860 points

Hi,

My customer is also facing similar issue with UCC28881, high pitch noise was heard.

Perform sound spectrum analysis on the noise and found that it has noise peaks at 9.7khz and 19.4khz, when the output is connected to a 200ohm dummy load.

Is there a easy way to eliminate the noise or move it out of audible range ?

Thanks,

CM.