Calculating average current drain

[Mosaic]

I want have a uC running a circuit which has significant transient current spikes @ 120Hz (fixed) with a variable duty cycle of 1 to 5%. Kinda like running a strobe. It's a DC DC converter.

Say I have a pwr supply charging a 15Kuf low esr cap (to between 30 to 40VDC) which fires off @ 120Hz thru around a .1 ohm load.

How can I use the uC (16f886) to calc. the average current drain?

Thx!

 

[Mosaic]

Further digging reveals a solution:

using the equation C x dV = I x dt ; where C is in Farads, V volts, I Amps & t Seconds

I can use the 8.3ms period (less the 100uS (or so) pulse) to sample the starting (post pulse) and Peak voltages (pre pulse)of the charging cap. LTspice confirms the calculations!

Averaging these calcs over a couple seconds should give a decent result!