[time-nuts] potential low-RFI power supply

[Bob kb8tq]

Hi



> On May 18, 2020, at 1:19 PM, Joseph Gwinn <joegwinn at comcast.net> wrote:
> 
> On Mon, 18 May 2020 12:00:02 -0400, time-nuts-request at lists.febo.com 
> wrote:
> Re: time-nuts Digest, Vol 190, Issue 30
> 
>> Message: 1
>> Date: Sun, 17 May 2020 12:53:42 -0600
>> From: Eric Scace <eric at scace.org>
>> To: Time Nuts email list <time-nuts at lists.febo.com>
>> Subject: [time-nuts] potential low-RFI power supply
>> Message-ID: <C1DDF9AF-78D7-4DF1-876B-4FAE5F398D65 at scace.org>
>> Content-Type: text/plain;	charset=utf-8
>> 
>> Pro Audio Engineering announced a sale (through Friday) on its 
>> nominal 14 Vdc 4A switching supply 
>> <https://proaudioeng.com/products/pae-kx33-low-rfi-ac-power-supply/>. 
>> The test results 
>> <https://proaudioeng.com/products/pae-kx33-low-rfi-ac-power-supply/> 
>> webpage compares noise on the DC output and noise frequency spectrum 
>> under a variety of conditions with a lead-acid battery, an Astron 
>> linear supply, and a variety of switching supplies from other 
>> manufacturers.
>> 
>> I have not used this and can?t vouch for its performance. Given 
>> recent discussions here on supplies, the analysis might be 
>> interesting. At least the supplier has attempted to quantify the 
>> performance of its power supply and make that information available 
>> to the prospective purchaser.
>> 
>> It would be interesting to see comparable (or more suitable) 
>> measurements made by others posted here.
> 
> Given that this power supply is intended for audio applications such as 
> mixer boards, if the switching frequency exceeds say 200 KHz, none of 
> the ripple spurs will matter, as they are far above the band.  Hmm.  
> Unless that get too close to the sampling rate of some delta-sigma 
> converter I suppose.

If it was only that simple …..

Switchers go into a variety of modes depending on what state they are in. 
One common mode “burps” the output when the load current is low. This 
significantly improves efficiency. It also takes the “crud frequency” way down. 

We often use one of these devices at a load well below the rated max. That
makes getting into these sorts of modes a fairly common thing. 

Bob


> 
> Joe Gwinn
> 
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