[Amps] Switching Power Supplies

[Will Matney]

Tony,

What is the waveform coming out? Is it a square wave, or is it a modified sine wave (a stair steeped square wave that supposed to mimick a sine wave)? If it were me, I'd want the square wave, rectify it, and then filter it well. All older modile tube amps worked this way, so did automotive radios that used a vibrator, and later semis to switch with. One needs to rectify it first, then filter it thoroughly the same as any other supply. In your case you'd probably be using a choke instead of a transformer, or will you be switching a transformer? There's several ways to set these up. In any instance, the weight savings is due to using a higher frequency.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/14/06 at 2:56 PM Tony King - W4ZT wrote:

>Tom W8JI wrote:
><snip>
>>  I can't imagine why an amateur would want to use a 
>> switching supply for a filament. What reason is there to do 
>> that?
>> 
>> 73 Tom 
>
>Tom,
>
>The reason I chose a small switcher for my filament supply was to 
>provide a stable DC filament voltage over changing input line voltages. 
>The switcher I found was a fully shielded commercial variety that 
>appears to be relatively RFI free, weighs less than the transformer 
>normally used and generates none of the heat an analog regulator produces.
>
>My experience with switchers may be limited compared to others but most 
>of the problems I have seen have been noise coupled to and radiated by 
>the incoming power line. The switcher for the amp filament has an output 
>which is very clean on the scope over varying loads and input voltages. 
>At the same time, there was very little detectable RFI from the line 
>cord sniffing across the HF bands.
>
>Well built switchers do exist but it certainly demands a proper 
>application of that technology as you pointed out with the coupling in 
>the ICOM and MFJ examples.
>
>Thanks for your comments.
>
>73, Tony W4ZT
>
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