[Amps] Resonant choke filter

[R.Measures]

On Aug 2, 2004, at 2:03 AM, peter.chadwick at 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