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removing input capacitor

Posted by: fairfix on

Hi I am using the following schematic. I am wonder if it is possible to remove one of the input capacitors and increase the other capacitor to 10uf for example?

I just don't have enough space on my PCB so I am looking to reduce the number of components.

 

If above change is not possible, do you have any advice on how to reduce the number of components?

 

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Comments

Submitted by fairfix on 05/25/2017

no one here to help me please? I was wondered if I could remove one of the input capacitors and use one big capacitor(twice the suggested size).

 

 

Hi fairfix,

Thank you for using Power Integrations' part.

You can do that but you will have problem or difficulty passing EMI.  You can try putting ceramic cap so you can still have pi filter (C-L-C) at your input and check if you can pass your EMI.  Thank you.

Submitted by fairfix on 05/29/2017

Thanks for replying. I have another question.

The online simulator suggest 35v 100uf as output capacitor. What would happen if I replace this with a higher voltage capacitor? 63v, 100v etc. does it harm the circuit at all?

Also if having inductor and two capacitors as filter is compulsory for emi, why simulation software replaces the inductor with a 100ohm resistor when I reduce the output current to under 0.08A ?

 

 

Hi fairfix,

It will do no harm on your circuit.  For the same capacitance with higher voltage rating, it will just make your capacitor bigger and more expensive.

With your simulation result, it only shows electrical performance at specific condition.  You can't pass EMI just by simulation, you really have to test it and debug since a lot of factors are affecting your EMI from PCB layout, transformer construction, snubbers, filter values, etc.  Thanks.