Hi All,
How do I reduce noise ripple in a DC-DC Power supply PCB, I tried by using a 10uF output capacitor. At present my noise ripple value is approximately 150mV. I need to bring it down to anything less than 80mV. Any suggestions is highly appreciated. Thanks in advance.
Hello,
I am not sure about this one. One of our Engineers will take a look and come up with some solution.
1 Like
Hello @suhas,
A few ideas:
-
Use a pi filter composed of two capacitors and a power inductor.
-
Use linear Low Drop Out (LDO) regulator.
Please tell us more about your project so that we may provide an improved answer.
Best wishes,
APDahlen
3 Likes
@APDahlen’s suggestions are nearly bulletproof solutions I’ve used myself.
For a possible lower cost solution I’d try adding some smaller value capacitors in parallel with the 10uF cap. This often works because a 10uF capacitor is not very good at lowering the highest frequency components of ripple in a switching power supply.
If you have an oscilloscope you can quickly see what values work best on your specific circuit. I often end up with one or more additional 100nF to 1nF caps along with the larger bulk capacitor in sensitive circuits.
3 Likes
Along the lines of APDahlen’s suggestion of a Pi filter/inductor, ferrite beads used in combination with capacitors can be used,
Texas Instruments Application Note:
ISR Input/Output Filters (Rev. A) (ti.com)
Hi suhas,
The responses by the others are all right on. Two things you didn’t mention are the nature of the noise (frequency ranges) you are seeing and the type of capacitor you are using.
The frequency range will determine the value of components you might use in creating output filters.
Regarding capacitors, standard aluminum electrolytic capacitors tend to be much worse than other types, such as ceramic, tantalum-polymer, and aluminum-polymer capacitors because they tend to have higher equivalent series resistance (ESR) and higher series inductance than other types.
As @PaulHutch suggests, simply adding a lower value ceramic capacitor such as 1.0uF or even 0.1uF in parallel may be enough to fix the problem. Replacing your cap with one of the above mentioned alternative types of capacitors might also make a significant difference. A combination of changing the type of capacitor and adding another lower-value ceramic cap might further improve it.
If that doesn’t work, then going with the Pi filter, as @APDahlen suggests would be the next option. Going beyond that, his suggestion of using an LDO regulator will have a very significant effect on reducing ripple. However, that would require more parts and more space, and one would need to increase the output voltage of your DC-DC converter to above the minimum drop-out voltage of the LDO so that it can regulate to your required output voltage.
1 Like
To tackle that noise ripple, you might want to try adding a larger capacitor or pairing your 10µF with a low ESR cap for better filtering. Also, check your PCB layout and grounding—sometimes, that can make a big difference.