Delayed capacitor discharge in SMPS

[vectorplane]

Thanks Poobah

Let's talk about amp-seconds (coulombs). Say you want to put 1 Amp-second into a capacitor, forget about voltage for the moment, awssume the capacitor is large the voltage doesn't really change, and the capacitor has 1 Ohm of internal resistance.

The 1 Ohm, is that the ESR?

vectorplane

 

[poobah]

Right Vector,

Not a practical number for ESR... but easy on the head. And as it applies to switchers, you can forget about the voltage on the cap in question because, for the sake of argument only, you assume the capacitance is infinte.

Most all of the equations for switchers are all roughly based on this assumtion... that is of course until it's time to select capacitors; and then you choose caps more by their voltage rating and ESR... not the capacitance value.

Cheers dude -