On Aug 2, 2004, at 2:03 AM, peter.chadwick@Zarlink.Com wrote:
Is actual resonance what you want? The argument I've seen runs as
follows;
In a choke input supply, there's a critical minimum value of
inductance for
regulation. At low currents, this is very high, but if the choke is
tuned
slightly HF of the ripple frequency, it looks like a very much bigger
inductance. At resonance, it will look like a resistor, of course. As
the
load current increases, the critical value of inductance decreases,
and the
choke will start to lose inductance anyway.
From this, the choke needs to be tuned a tad HF at minimum load. This
certainly ahs worked for me. Incidentally, by using negative lead
filtering, you can rectify the ripple across the choke for a low
current
negative bias supply.....
I tend to go for negative lead filtering anyway to ease the choke
insulation requirements.
Peter -- In a typical, grounded-screen, AB1, grid-driven amplifier,
the negative lead of the screen PS is 1000 to 1500 V above
chassis/ground potential, and the positive lead is at ground potential.
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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