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|4th July 2016, 06:49 PM||#1|
Join Date: Sep 2004
Capacitor Ripple Current vs Operational Temp
I'm trying to decide between two caps for the regulator section of a power supply. They are the pre and post capacitors for +/-15V regulators.
Nichicon KW - 1000uf 25V
Ripple Current: 950mA
Lifetime at Temp: 2000 Hrs at 85 deg C
Nichicon KA - 1000uf 25V
Ripple Current: 680mA
Lifetime at Temp: 2000 Hrs at 105 deg C
The KW allows for higher ripple current, but the KA shows a higher temp rating. Based on my reading on ripple current ratings, it looks to be a sliding scale based on temperature. If I am correct in my assumptions, a capacitor will have a higher ripple current capability when operated at a lower temp. So, ultimately, what is the real difference between these two capacitors.
These will be pre/post regulator filters for the op amp sections of a DAC. There are 5 Class A op amp circuits (each with about 28ma quiescent current), so there will definitely be some current being run through the system. The caps will be mounted right next to the regulator heatsinks, which will measure about 55-60 degrees C. The caps will warm up with the current and will run somewhere between 30-40 deg C.
Of course, I'm really after sound quality, since these caps will not be run in an auto or industrial scenario. However, which one of these caps will perform better in my situation?
|4th July 2016, 06:57 PM||#2|
Use the 105C parts as they will have a longer life. That would be my advice. Your actual ripple current is going to be way below either parts maximum, and although either will perform well initially, in 10 or 20yrs time it may be a different story... and yes, a well designed circuit should certainly hold its performance for at least 10 to 15 years before any hint of cap trouble creeps in.
Manufacturers often learnt this the hard way. Dried out and failed 'standard cooking grade' parts are a fact of life in busy service departments.
Installing and using LTspice IV. From beginner to advanced.
|4th July 2016, 07:25 PM||#3|
Join Date: Nov 2009
Location: Los Angeles
Where did you find caps with such lousy ripple current?
These would be fine and there are MANY others.
EEU-FM1E102 Panasonic Electronic Components | Capacitors | DigiKey
EKZE250ELL102MK20S United Chemi-Con | Capacitors | DigiKey
Note the longer life hours and higher ripple current and the price is OK.
Heat is what kills electronics so if you want things to last, don't cook them.
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