Is there a standard calculation for the ripple current requirements of an output capacitor of a SMPS, particular a boost converter in this case? It's a bit complicated since at maximum output power the ripple current is a non 50% duty cycle steep ramp with a high peak at (in this case) 50khz.
Simulation waveform attached.
Simulation waveform attached.
Attachments
Simulation will normally provide an rms calculation. Cap datasheet will have frequency multiplier.
The rms value of a continuous, periodic triangle or sawtooth signal based on 0 offset is Irms1=peak value / sqrt(3)=6.25A/1.73=3.608A in this case. But here you have a 0 domain, so the energy is spread to a longer period (T), so Irms2=Irms1*sqrt(T1/T)=3.608A*sqrt(8us/20us)=2.28A. But when I calculated this I introduced a DC content to push the base up to 0, so I have to subtract the power of it, therefore the final value is Irms=sqrt(Irms2^2-IrmsDC^2)=sqrt(2.28^2-1.2^2)=1.94A
The whole formula: Irms=sqrt((Ipp/1.73*sqrt(D))^2-(Inegative peak)^2)
D=T1/T (=duty cycle)
The rules I used: powers (mean square value) of different frequency signals are added,
and energy of signal slices in non-overlapping time domains are also added.
The whole formula: Irms=sqrt((Ipp/1.73*sqrt(D))^2-(Inegative peak)^2)
D=T1/T (=duty cycle)
The rules I used: powers (mean square value) of different frequency signals are added,
and energy of signal slices in non-overlapping time domains are also added.
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