Hi all,

I want to know how to calculate the inrush current due a ultracaps bank. This is because i'm designing a DC DC converter and i don't want to break the semiconductors. Is there a way to calculate it knowing the capacitance, ESR, voltages (ΔV) and switching frequency? Does the same procedure applies for normal capacitors?

Thanks a lot.

 

Hi all,

I want to know how to calculate the inrush current due a ultracaps bank. This is because i'm designing a DC DC converter and i don't want to break the semiconductors. Is there a way to calculate it knowing the capacitance, ESR, voltages (ΔV) and switching frequency? Does the same procedure applies for normal capacitors?

Thanks a lot.

It would appear that you could use the ESR to do this... if my understanding from a quick Wikipedia( ) search is correct, the current will be the voltage/ESR...

 

It depends on the ESR of the capacitors, the resistance of the connections and the rate of rise of the applied voltage.

You will need to soft-start your DC to DC. Or have some kind of active current limiting.

 

Does the inrush current apply only to a capacitor in t=0 with Vc=0? If the cap is pre-charged to at least 1/4 of its rated voltage and then the voltage is increased, an inrush current is expected?

Thanks

 

Hi all,

I want to know how to calculate the inrush current due a ultracaps bank. This is because i'm designing a DC DC converter and i don't want to break the semiconductors. Is there a way to calculate it knowing the capacitance, ESR, voltages (ΔV) and switching frequency? Does the same procedure applies for normal capacitors?

Thanks a lot.

The design has to incorporate current limiting or soft-start which protects the converter during charge up or it won't survive. The best type is pulse-to-pulse limiting as used in a current mode converter.