Electronics > Beginners
Current limiting schematic
chiken:
So i found this schematic circuit of cheap 30V 3A power supply, and could anyone tell me which part is in charge of regulating constant current (shunt and opamp??)
https://drive.google.com/file/d/0B7Bk3JifFLbSU255VzE2ZHJJVU0/view
FInished board looks like this
https://img.staticbg.com/thumb/large/oaupload/banggood/images/94/40/5a8647d5-1287-468f-ac31-75f6f9b2ae7a.jpg
Benta:
R7 and Q1.
chiken:
Well, it seems like thats it,
i thought that i would be different,
Does anyone know where could i find a bit of explanation of "mechanism" like this?
Jwillis:
Q1 is for short circuit protection. Under normal operation Q1 is nonconductive because the resistor R14 through the base of Q1 is held at negative voltage. But when negative voltage starts to fall, the transistor Q1 becomes conductive (due to the positive voltage on its base through resistor R13), and thus connects the output of U2 to the ground and locks the transistor Q2, so it shut down the output voltage through Q4 .U3 and R7 are for holding constant current based on the adjustment of U1 .
floobydust:
Just so you know, that 0-30V 2mA-3A PCB layout is shit because the traces to the current-sense resistor are not properly done. People cut the trace and run a wire to the correct spot. Otherwise the current-limit is not so stable. That PSU has been discussed at great length here in many threads.
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