after i finished some basic psus over the last weeks, i'm just thinking about tweaking them a bit further. one thing i realized while testing those lm317-circuits is that their voltage-regulation is prone to current-changes: usually i read a ~150mV decrease at 24v when i activate a 240mA dummy load (100 ohm resistor). similar results with my commercial mascot psu and three different diy lm317- and 7824 devices.
i did some research on how to stabilize the voltage a bit further - sticking with the lm317/337 -, but could need some help to understand the matter:
A) add a voltage reference:
(s.
lm336 datasheet)
this is an example i found in the lm336 (=voltage reference) datasheet. there are no further comments on it. the headline "precision power regulator" sounds appealing. but what "precision power" is meant here: precision sensu voltage accuracy with changing currents? or precision in terms of accuracy of voltage adjustment, that still will vary the same way under load i found it before? hm... i'd have to figure out the math behind it to adjust resistor-sizes to get a proper voltage range too.
B) tracking voltage regulator:
(s. lm317 datasheet)
an additional lm317 tracks the voltage output of the second one in series. could this be an even better solution? one drawback for sure: additional ~2v voltage drop...
any comments / explanations or suggestions are welcome!
voltage reference & tracking psu - some questions
