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inrush current estimation:
assumption: Vin apply to C with Resr only, can view as a simple R+C network.
i(t)=(V-Vc)/Resr
Vc(t)=V(1-exp(-t/τ)), where τ=Resr*C
===> i(t)=V/Resr*exp(-t/τ)
===> i_inrush= i_max=lim_t->0 i(t)=V/Resr
usually Resr is small, (e.g. 50m ohm)
if V=5V, Resr=50m, then i_inrush=5/50m=100 A
I think this equation is too simple, and it doesn't the real case.
I don't know this question yet, but if the inrush current from this equation is too far from the real one, then that is no use for designer. OK?
I assume a non-isolated buck converter. During start-up, the PWM signal can be assumed to be 100% (in real case, it may be 95% only). Therefore, looking from the input of the buck converter, there is a inductor, a resistor (the on-resistance of MOS switch) and a output capacitor connected in series. From this model, you can solve the differential equation and get the maximum inrush current quring start-up.
I think this equation is too simple, and it doesn't the real case.
I don't know this question yet, but if the inrush current from this equation is too far from the real one, then that is no use for designer. OK?
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