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Old 20th October 2006, 12:30 AM   #11
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attached please find the picture with the choke supplied with coldamp

the amplitude is about 1 volt
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Old 20th October 2006, 12:32 AM   #12
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now with the choke and 0.47uF after forming a pi filter

only 300mV amplitude.

Next will be a test on the UCD modules
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Old 20th October 2006, 12:37 AM   #13
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This is how they are connected up
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Old 20th October 2006, 01:18 AM   #14
mourip is offline mourip  United States
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Default SPS30

Hi Sergio,

Any information on availability of the SPS30 yet? I am thinking of using one with mu UCD180s.

Thanks,

Paul
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Old 20th October 2006, 03:58 AM   #15
ssanmor is offline ssanmor  Spain
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It is in last production phase, around 6 weeks left aprox.
However, SPS80 can also be used with Ucd180, as the voltage is selectable at ordering time between +/-40V and +/-60V.
Best regards,
Sergio
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Old 20th October 2006, 04:05 AM   #16
Eva is offline Eva  Spain
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Quote:
Originally posted by ackcheng
This is how they are connected up
Long capacitor leads are hurting the efficiency of the filter.

Also a SMPS transformer should not buzz unless there is either a control loop instability problem, some current limiting is being triggered, or a low mains voltage condition is causing the PSU to operate open loop at maximum duty cycle. That's something worth checking.

In SMPS there is usually audible transformer noise with very low loads, but that's due to harmless pulse skipping.
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Old 20th October 2006, 05:17 AM   #17
ssanmor is offline ssanmor  Spain
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As Eva pointed out, if you connect no load, the is some audible noise, due to the controller stopping the pulses from time to time in order to keep the voltage at the desired level. This is easily solved by drawing some mA from each rail (that's what the 2K7/2W resistors at each rails are for).
The transformer buzzing under load is not really a buzz, and definitely not due to instability in the feedback loop, as it is implemented with low loop gain and is unconditionally stable, nor to current limit (you can get much more than 440W from it, that's tested). The duty cycle is near max. at that power, however, and mains line variation can be appreciable ;-)
You all should hear it, the "buzzing" is very very low and I think Ackcheng simply commented about it as a side note.

Every transformer/inductor submitted to high current levels can buzz a bit, due to the windings vibrating a little bit around the core and its deformation due to magnetostriction. Even the cores of Class-D amplifiers sound when you output high power ;-)
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Old 20th October 2006, 05:53 AM   #18
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Yes, the "buzzing" is a very very low noise indeed, and when we did the test, it was 3:00am in the midnight!
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Old 21st October 2006, 08:07 AM   #19
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by Eva


Long capacitor leads are hurting the efficiency of the filter.

Also a SMPS transformer should not buzz unless there is either a control loop instability problem, some current limiting is being triggered, or a low mains voltage condition is causing the PSU to operate open loop at maximum duty cycle. That's something worth checking.

In SMPS there is usually audible transformer noise with very low loads, but that's due to harmless pulse skipping.

Yes, that was my first reaction too, make the wires to the cap as short as possible. You can also add like a 470uF cap or, that further smooths the ripple (did that with another SMPS I have).

Best regards

Gerrjan
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Old 21st October 2006, 08:14 AM   #20
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by ackcheng
now with the choke and 0.47uF after forming a pi filter

only 300mV amplitude.

Next will be a test on the UCD modules

If you want to see what it does with the UcD modules, then my advice is to do the following.

Connect the supply to the UcD module. With the scope, monitor the voltage over one of the 470uF caps on the UcD board. Do that with the UcD in standby mode. Then you will see that hardly any noise from the supply rails reached that 470uF cap (the UcD supply rail on board). The LC filter on the UcD board does a very good job keeping HF power supply rail noise out. If you turn the UcD on, you will see quite a lot of noise over those 470uF caps, this noise is induced by the UcD itself and is much bigger in amplitude then the noise from the SPS80. So any remaining noise from the SPS80 should be no issue at all.

Best regards

GErtjan
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