- Joined Nov 10, 2018
Hello again, this is not about something that does not work but something that despite of what I read it works. I want to make a power supply based on two LM317. I connected the LM317 that does the voltage regulation to another LM317 that does current regulation. I read in different sources the current regulation unit should be before the voltage regulation. However my logic tells me that I should wire them the other way around and it worked. I used 12V as input to the first LM317, I did not go up to 40V. I set it to give a 8.3V regulated voltage and that fed to the second one. I experimented on the second one with resistors from 15Ω to 82Ω as I do not have such a potentiometer yet and seemed that it was working perfectly as a current limiter. As I was approaching lower values the current was increasing close to the limit and the voltage also at the output pin of the second LM317 closer to 8.3V. When I want a regulated voltage with a current limit I am thinking that I should use a DPDT switch to connect them together to have the configuration in the schematic, otherwise they will stay disconnected for voltage regulation only. So... it looks to good to be true, is it something I do not see?
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