Author Topic: Xantrex/Sorensen XHR 40-25 schematic?  (Read 36041 times)

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Offline ifonlyeverythingTopic starter

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Re: Xantrex/Sorensen XHR 40-25 schematic?
« Reply #50 on: May 07, 2024, 01:30:11 am »
Been trying to understand the CV offset issue for a day or two, kind of stuck. Would appreciate any help. It's a variable offset (see below for examples) and I have discovered two scenarios that will create this problem.

At a CV of 36.0V I see a swing up to 36.8V. Delta of 0.8V.
At a CV of 22.5V I see a swing up to 23.9V. Delta of 1.4V.
At a CV of 12.4V I see a swing up to 13.1V. Delta of 0.7V.

Scenario 1:
STANDBY enabled.
I click V/I and dial in my CV limit of 22.5V.



STANDBY disabled.
I click V/I and my commanded CV limit has changed to 23.9V.
Notice the change from 2.755V to 2.920V, an offset of +0.165V.



Scenario 2:
STANDBY enabled.
I click V/I and dial in my CV limit of 22.5V.



STANDYBY remains enabled.
REMOTE programming enabled.
I click V/I and my commanded CV limit has changed to 23.9V.
Notice the change from 2.755V to 2.920V, an offset of +0.165V.



R230 measures 10K and the voltage drop across it at all times in all of these scenarios is 0.000V -- it's not a source of current being injected.

This is what the 10-turn (R35), V/I check button (SW75A), REMOTE button (SW73), and STANDBY button (SW74) are doing on the front panel. Keep in mind clicking V/I doesn't change the value on the non-inverting pin (as per my measurement), it just does an analog to digital conversion and displays it on the front panel.

« Last Edit: May 07, 2024, 11:10:10 am by ifonlyeverything »
 

Offline ifonlyeverythingTopic starter

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Re: Xantrex/Sorensen XHR 40-25 schematic?
« Reply #51 on: May 26, 2024, 12:00:21 am »
Spent some more time playing with this. I've pinpointed it to Q194 causing VCTL to droop when shutdown is enabled i.e., Q194 is pulling the non-inverting pin of U199D (pin 12) to ground. I wonder if this is a "design flaw." The worst delta is at around 22.4V (swings up to 23.9V for a 1.4V error) and is around 6% so it's not too bad. Just annoying that it exists in the first place.  :-\

My guess is that increasing R219 would help (and decreasing C220) but I don't particularly feel like finding out what other potential downstream impacts might be...
« Last Edit: May 26, 2024, 12:02:04 am by ifonlyeverything »
 


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