Hi Jim. Been years since we've talked (back in the auto tuner days),
hope all's well with you.
The average current in must equal the average current out. The filter
capacitor CANNOT charge to the peak voltage of the transformer if there
is any load current.
Because of the diodes, this is a nonlinear circuit and you really need
to be more analytical. But even in the verbal analysis, if you assume
constant 1A of load current, flowing continuously, then the peak diode
current MUST be very much larger to supply the same number of coulombs
in the short charging interval at the peak of the AC waveform.
In other words, dc load current flows continuously, diode current flows
over a shorter interval, so the diode current (when it flows) must be
larger than the load current. The diode current in a real supply has a
huge peak with a higher RMS value that the dc current flowing to the
load. That's why, in the olden days, transformers were always rated for
less load current with capacitor-input filters than for choke input
filters. Now capacitor input filters are so common that distinction
isn't stressed any more, but the physics of the situation hasn't
changed.
I few minutes with SPICE and you can accurately predict what happens.
Regards - Bill - W7AAZ
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