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In Reply to: Re: Take a look at I(T1) posted by dave slagle on May 9, 2007 at 07:10:11:
"This is when i noticed that the current waveform for the "real choke input" seemed to have the most HF content."I don't understand. Are you saying that this will throw more RF than the one in the link below?
There are two "spikes" per cycle in both waveforms and these are much smaller than the spikes without the choke.
Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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In this scale, RF content is represented by a vertical line. the more the line approaches a pure vertical, the higher the frequency content. The magnitude of the signals has nothing to do with this. By adding a small choke in front of the first C you end up greatly reducing the narrowness of the current draw "spike" netting what appears to me to be a current draw with much less high frequency content than even a "real" choke input filter.
"By adding a small choke in front of the first C you end up greatly reducing the narrowness of the current draw "spike" netting what appears to me to be a current draw with much less high frequency content than even a "real" choke input filter."In this example, what value choke would be "best".
Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The best choke would be the one chosen by ear, but since we are in sim land you first have to decide what you want the current to look like then decide what looks best. How that translates to what sounds best is still up for discussion.
Anything that adds resistance/impedance between wall power and first cap will help increase conduction angle. Any increase in conduction angle moves you closer to a real choke input supply.Play around....up the transformer DCR...go to FWCT and a 5U4....try an RC filter stage. There is no best here. It is more of a mental exercise and to see if what looks "pretty" on the scope/sim.....and/or.....to see/hear if drawing current at a steady constant level (that reverses each 1/2 cycle) is better than drawing current in sine wave manner. Don't forget to increase load as needed.
Being who and what we are here, I reckon when we see an evil square wave we freak and think "sum of odd order harmonics".
but russ, that Evil R instantly converts distorted current into distorted voltage.
I didn't mean best in that way. When I add a small choke it lowers the amplitude but doesn't change the shape. Am I missing something?Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
if it lowers the amplitude, it has to change the shape. Assuming the same power into the load, the area under the plots must remain the same independent of filter type, so if you decrease amplitude, you must widen the trace at some point to keep the area constant.
It appears that the total magnitude is higher for green, but green drops off faster/more with increasing frequency. I'm a little hesitant to mindlessly trust the sim results. It would be interesting to build just these two simple supplies and measure the actual noise.
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