Capacitor for High Current Output
Posted by: aliaykan
on
Hi,
Is it possible to use electrolytic and MLCC paralleled as output capacitor together? For high output current flyback converters e.g. 12A capacitor output ripple is very high like 15-16A. This ripple current can be achieved with ~4-5 large electrolytic or polymer capacitor.
For example 680uf capacitor is enough for secondary control loop but output capacitor ripple is 15A. Can I use multiple MLCC parallel to this 680uf for achieving ripple current level?
Hi aliaykan,
Current ripple is generally divided among parallel capacitors based on their capacitance value. The higher the capacitance, the higher current it will draw.
If the current ripple through the polymer capacitor is to be reduced from 15 A to 4 A, this means that 3 more 680 µF capacitors must be in parallel to it.
If 22 µF MLCCs are to be used, it would take roughly 93 capacitors to have the required effective capacitance.
This would be clearly impractical and costly as compared to using 3 more low esr 680 µF polymer capacitors.
One thing to note as well is that for flyback topology, the secondary current ripple will be high.
Due to the secondary side only conducting during the primary switch off time, the secondary side current peak must be high to deliver the power to the load.
I hope to have helped you with your question. Feel free to ask again if you have any clarifications. Thanks!