How to Filter periodical DC noise in DC Power Supply Lines?

[Sigma|Six]

power supply noise

Hi,

My DC power supply system suffers from a periodical noise 1V p-p at the ouput.
The bad thing is it couples into the other subsystems~! OMG

The input of the system is derived from 5V & 12V of the ATX chassis, and I have determined that the 1V p-p is actually comes from this unit, probably caused by a switch mode power supply.

Can someone tell me how to eliminate the noise without affecting the performance of the DC power supply? is adding a big capacitors at the inlet of my PSU system a good idea or a Low Pass Filter is a must?

Please share your thoughts

Sigma|Six

 

[renwl]

Re: How to Filter periodical DC noise in DC Power Supply Li

what's the period? I prefer to simple rc filter. the period determine the rc.

 

[sengyee88]

Re: How to Filter periodical DC noise in DC Power Supply Li

I think some LC filters may solve your prob. I don think you can use RC flter for power supply filtering, as it give large IR drops and basically the R need to be power resstor, that giving even more noise.

Btw, 1Vpp noise is huge if your supply is 5V. It could have some low impedance paths to some points that causing this 1Vpp ripple.

 

[khaled fayed]

Re: How to Filter periodical DC noise in DC Power Supply Li

I think if u still suffer from problems after the above suggestions u may try to add a low dro out linear regulator (LDO)

 

[zenisle]

use RC filter is ok

 

[artem]

ATX power supply should not generate such high noise. Have a look to example supply specifications :
**broken link removed**

Such values for your measurements could be:
- faulty power supply
- not properly choosen points to measure voltage . measure voltage on the point where it comes out of power supply. Ground and VCC terminals must be on same ATX power connector.
- current consuming switching load which generate such noise. Switching supply load regulation can manage changing load at some extend in terms of frequency spectre of current consumption by device. Thus high freq switching devices connected to supply will generate noise which can not be managed by supply itself (via feedback regulation). You have to filter them by decoupling capacitors, put as close as possible to switching load.

Good luck

 

[hung_wai_ming@hotmail.com]

Looks like your grounding from ATX chasis is BAD