Modelling a DC filament supply in PSU Designer II

[G]

I have tried to model a filament supply in PSU Designer II several times in the past and I never get an accurate result. Why? Let's say that I want to use a 6.3v 2.5A winding and I rectify it with a bridge rectifier followed by a series .5 ohm resistor and then a 4700 uf 25v capacitor. Now the load on this is 6.3v@1.55 amps which is a load of basically 4 ohms. Why will this not model correctly in PSU Designer?

[SY]

Did you use the right transformer parameters (i.e., correct off-load voltage and source resistance)?

[G]

Originally posted by SY
Did you use the right transformer parameters (i.e., correct off-load voltage and source resistance)?

Yep. I had it model for 30 seconds after a delay of 10 seconds. Maybe this is just something I will need to actually build a tweak huh? I would think that if the winding can supply the current using AC voltage then it should be able to supply the current using DC voltage right? I wonder if there is something very simple that I am missing.

[Bandersnatch]

Originally posted by G


I would think that if the winding can supply the current using AC voltage then it should be able to supply the current using DC voltage right? I wonder if there is something very simple that I am missing.

hey-Hey!!!,
You've noticed the effect of increasing the RMS current delivery to the capacitor filter through your resistance. You need big current delivery spikes to keep the capacitor charged. Between the added R, and the winding resistance you've got too much.

In PSUDii look at V across the R part of the filter, it won't be as small as you thought.
cheers,
Douglas