Calculate the Input/Output Capacitor Value on DCDC converter


Thread Starter


Hi everyone,

I have a general question on how to calculate the input and out capacitor values for a DCDC converter for filtering/smoothing.

My example:

DCDC Converter: Synqor NQ60W60QTC25NRS
Input Voltage: 36v
Output Voltage: 12v
Load: 5A

Are there any mathematical formulas to find what capacitor values to use?
Is there any rule of thumb?

Also, I have read that for the specific purpose (filtering/smoothing) better to use a ceramic capacitor instead of an electrolytic, is that right?

Thanks in advance for your answers!


No. Electrolytics and ceramics serve different purposes:
  • Electrolytics with their high capacitance serve to buffer a lot of charges to provide high currents for a long time (comparatively).
  • Ceramics with their low capacitance but also very low ESR to filter primarily high-frequency noise.
Usually, a combination of both types (and even ceramics of different capacities) is used to cover a wide range of frequencies.