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EEZ Bench Box 3 - Sequel to EEZ H24005

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prasimix:
Ok, glad to hear that you managed to fix that with calibration. it seems that low range (50 mA) required recalibration.

Mike G:
The fault only showed up above 50mA so I assumed the problem was with the High current calibration.
Anyhow all ok now, seems strange this only showed up after upgrading.
The thing I noticed was that the dodgy DCP had four calibration points when I checked, two of them very low current, less than 50 mA so I erased the two low ones and just recalibrated at 50mA and 4.8A.  The DCP that showed no problems only had calibration points at 50mA, 2A and 4.8A  so I suspect the problem was caused by having calibration points below 50mA in the high current calibration :-//

prasimix:
Good, to know. Just be sure that you have at least 4 calibration points in total: two for low range (50 mA) and two for high range (5 A).

Kleinstein:
The CC led going on could be related to an offset in the set current limit. So if the current limit is set very low, it may actually be set below 0 and than cause the CC mode to engage when off.  It should not cause a problem - more like a bit confusing because of the LED, but hardly any change to the output.

Chances are that on turn on of the outout the CC mode will engage anyway for a short time ( ~ ms, so may not be very visible) until the voltage reaches it's set values. I asume the DCP does not copy the R&S supply "bug" in setting high the current limit for a few ms when the voltage is supposed to rise.
The Firmware update may have changes to off part - looks like that in off state the current limit is also set down (not sure if actually needed, maybe in the hope to reduce overshoot in some cases).

prasimix:
@kleinstein, currently we have the following situation: When power output is enabled, we don't have any overshoot. For "R&S" setup, i.e. Uset=3.3 V and Iset=1 A with 2R load we're entering CC mode like this:



However there is another scenario that Dave didn't tested: a "list programming" (that could be R&S's EasyARB). Here we can overshooting for ~1 ms if Uset is fixed (e.g. 3.3 V) and current is programmed between 20 mA and 1 A when current range is set in BEST:



A note about that is exists in our User manual:

Important: when power module is operating in CC mode, and load is changed dynamically that current vary between low and high current range, switching between ranges will generates voltage overshoots due to finite switching speed. Set current range manually in that case to avoid voltage overshoots.

If we just change current range selection from BEST to HIGH then everything is fine again:



Perhaps we should force current range selection from BEST to HIGH when list programming is selected to avoid this issue.

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