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Replace electrolytic capacitors with ceramic or tantalum capacitors.

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luiHS:

Hello.

Is it possible to replace, in the circuit of a switched power supply, electrolytic input and output capacitors, by ceramic or tantalum capacitors?

To assemble with my pick and place machine, it would be better to reduce the size of these components (SMD), but I am not sure if enough that the capacitors are of the same value.

Regards

MagicSmoker:

--- Quote from: luiHS on April 13, 2019, 11:22:00 am ---Is it possible to replace, in the circuit of a switched power supply, electrolytic input and output capacitors, by ceramic or tantalum capacitors?
...

--- End quote ---

Not something I would do without careful analysis of the circuit because the ESR of the humble aluminum electrolytic can actually be helpful in some situations. For example, the ESR of the input elko reduces ringing/overshoot that can occur when power is suddenly applied while the ESR of the output elko inserts a zero that helps stabilize the control loop.

Psi:
It's usually ok to do this.

But as said above, watch out for things going unstable.
Low Dropout linear regs are the worst for this but switchmode regs can also go unstable if you push the ESR very low.

Using tantalum's in place of electrolytics is less likely to make things unstable than using ceramics.
Because while tantalum's have low ESR ceramics have very low ESR.

Downside of tantalum's is price and they have a tendency to fail very easily if you don't respect their voltage rating (including spikes exceeding the rating).

Miti:
Check this out if you intend to use smd tantalum caps.
http://www.kemet.com/Lists/filestore/Derating%20Guidelings%20for%20Tantalum%202011%20(3).pdf

Siwastaja:

--- Quote from: luiHS on April 13, 2019, 11:22:00 am ---Is it possible to replace, in the circuit of a switched power supply, electrolytic input and output capacitors, by ceramic or tantalum capacitors?

--- End quote ---

Not easily. It's a complete redesign wrt capacitors, and requires the full understanding about said capacitor types, in said circuit. This is far from trivial. At least the following apply:
* Control loop stability,
* Stray LC snubbing, especially related to inrush voltage overshoot and ringing
* Surge current ratings (tantalums may catch fire)
* Board flex with large ceramics

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