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DER385 & LLC Output Capacitors

Posted by: aliaykan on

DER385-Output Capacitors

 

1. I need to advice about LLC output stage capacitors' selection for high output current and long reliability.

As you know LLC converters need to lower capacitance for output stage. Polymer aluminum solid electrolytic capacitors

seems best solution for high ripple current performance at lower capacitances. But their lifespan restricted to

5K hours(best in class) and in practical ambient conditions, only can reach up to 20-30K Hours.

 

Aluminum electrolytic ones' such as Panasonic FR, endurance rate about 10K hours and can reach up to 100K hours at

10-15 degree below the spesified temperature. Negative side is it has very high capacitances for LLC output stage.

 

So, do you have any advice for using long life (100K hours apprx) output capacitors? Is it resonable approximation

adding a low capacitance capacitor parallel to higher one for avoiding auto restart mode in startup? 

 

 

 

2. Is in the DER385/Figure-5 pointed connections missed? According to layout R34 parallel to opto's led as usual and

ground connection.

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Comments

Submitted by PI-Neela on 02/01/2016

PIXL tool provide calculation for output capacitors in your design. Check that capacitrance value and determine if ceramic cap is practical.

Please re example the temp derating curve of your choice of polymer cap since they have different temp derating characteristics than Al cap.