Hi Chris
In my experience most SMPS that were designed for computer use require a minimum load to operate correctly. Some will not turn on at all until a minimum load is present. It also strikes me that the operating frequency of the RF Amp is very close to the likely switching frequency of the SMPS, especially given that the output filter capacitors are frequently part of the computer not the SMPS.
73
George G6HIG
________________________________________
From: hp_agilent_equipment@... <hp_agilent_equipment@...> on behalf of Chris Wilson chris@... [hp_agilent_equipment] <hp_agilent_equipment@...>
Sent: 29 April 2017 14:46
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] HP ESP120 Server 52V SMPS load removal question
29/04/2017 15:44
I am curious as to whether uncontrolled voltage regulation on the
drains of big FETs used in a push pull low frequency (136kHz) RF amp
run in quasi Class D may be caused by the 52V at 57 Amps HP computer
server SMPS not liking sudden load removal? I haven't the knowledge to
test whether the uncontrolled voltage waveform when the drive to the
amp is suddenly removed is from the antenna and loading coil, or from
the PS. But from a max of 130V peak to peak square wave on the drains
seen on my scope when running at 52V supply I can sometimes see the
pretty uncontrolled waveform go beyond 400V before decaying. Could it
be these SMPS can't cope with sudden load removal, and is there a way
to minimize or fix it? My only thought was a secondary, permanent
current draw in parallel with the 20 odd Amps the amp draws, maybe 10
Amps, but that's a lot of heat to dissipate. Any opinions welcome
please. Thanks.
The supply is exactly the same as these shown on Ebay:
--
Best Regards,
Chris Wilson.
mailto: chris@...
