DC link capacitor

[khalid4145]

Hi guys,,,



I am building a multilevel dc/dc converter with has four input power supplies each one of them is 30V total of 120V drawn a maximum load current for resistive load of 10A. i want to use a dc link capacitor across each power supply. my questions are:



1- why dc link capacitor important?



2- is it important in my application?



3- how do i choose a suitable value? which is better 100uf or 33000 uf?? or other values?



please advice

 

[dknguyen]

Sounds like a homework question because the way the questions are more like what someone would ask you to see what you know, rather than what someone would ask when they want to understand how it works. Also because you posted on other forums the same question as well.

 

[khalid4145]

Thanks for fast response. No it is not a homwork question!!!!

guys,,,I need more explinations. would you please answer all the questions. different openions will help. Thanks in advance.

 

[dknguyen]

They are important, but you don't need them (but you have to have an inductor if you do not not use one). You need one, or an inductor, or both because if you did not you would a lot of ripple on the output (a waveform that is jumps between a peak voltage and 0V.

Ideally, bigger the capacitor the better. But real capacitors have parasitic inductance which rises with capacitance. So eventually the inductance is so large it blocks the AC components you want to filter out from even getting into the capacitor (so then it appears on the output as ripple). You want the capacitor to be big enough capacitance, but small enough parasitic series inductance to get the output ripple that you want.

**broken link removed**