Electronics > Projects, Designs, and Technical Stuff
LM317 digital control
ZeTeX:
--- Quote from: Maobuff on May 22, 2016, 02:05:53 pm ---
--- Quote from: Kleinstein on May 22, 2016, 09:03:29 am ---Turning of the supply to the regulator in case of over-current is risky. A inductive load might give quite some kickback and thus damage the regulator. So there should be some over-voltage protection, at least a diode from the input to main filter cap.
--- End quote ---
Can i move relay to output of supply?
--- Quote from: ZeTeX on May 22, 2016, 02:02:23 pm ---So basically you just disconnect the power to the LM317? I dont think it is that good, the caps need to discharge and the regulator need to turn on \ off if you have something that gets current limited in a very fast pulses. I will test it in ltspice
--- End quote ---
Yes, that why im thinking of moving relay to output
--- End quote ---
relay for current limiting is very slow, when I build a circuit using the LT317 I got the current limiting 300us to start limiting.
(the circuit needs to be redesigned, but you can get the idea).
Maobuff:
--- Quote from: ZeTeX on May 22, 2016, 02:22:20 pm ---relay for current limiting is very slow, when I build a circuit using the LT317 I got the current limiting 300us to start limiting.
(the circuit needs to be redesigned, but you can get the idea).
--- End quote ---
Using one LM317 for CC and CV is not a good solution, its lowing voltage to lower current, but what if i short wires? Its gonna drop voltage to minimum (1.25) but resistance is low enough to consume more current that I set with CC part of circuit. And relay speed is fine.
ZeTeX:
--- Quote from: Maobuff on May 22, 2016, 03:24:32 pm ---
--- Quote from: ZeTeX on May 22, 2016, 02:22:20 pm ---relay for current limiting is very slow, when I build a circuit using the LT317 I got the current limiting 300us to start limiting.
(the circuit needs to be redesigned, but you can get the idea).
--- End quote ---
Using one LM317 for CC and CV is not a good solution, its lowing voltage to lower current, but what if i short wires? Its gonna drop voltage to minimum (1.25) but resistance is low enough to consume more current that I set with CC part of circuit. And relay speed is fine.
--- End quote ---
no no no, its gonna drop the voltage to 0V because I'm using negative supply. Its a closed loop feedback, the op amp is going to do whatever it has to do to get 0V output.
relay is too slow for current limiting for sure.
Maobuff:
--- Quote from: ZeTeX on May 22, 2016, 03:41:31 pm ---no no no, its gonna drop the voltage to 0V because I'm using negative supply. Its a closed loop feedback, the op amp is going to do whatever it has to do to get 0V output.
relay is too slow for current limiting for sure.
--- End quote ---
Why relay is slow? In my design if load consume more current its disconnect load from PSU.To connect it back i need to reset flipflop manually (or with help of MCU).
ZeTeX:
--- Quote from: Maobuff on May 22, 2016, 03:52:58 pm ---
--- Quote from: ZeTeX on May 22, 2016, 03:41:31 pm ---no no no, its gonna drop the voltage to 0V because I'm using negative supply. Its a closed loop feedback, the op amp is going to do whatever it has to do to get 0V output.
relay is too slow for current limiting for sure.
--- End quote ---
Why relay is slow? In my design if load consume more current its disconnect load from PSU.To connect it back i need to reset flipflop manually (or with help of MCU).
--- End quote ---
so lets say your circuit tell the relay to switch off or switch on.
Relay takes some time to switch off or on because the mechanical pin has to move a couple of mm in the air, it might sound like really fast, but really if its over 1ms its too much. not to mention that a relay is kinda loud and you will probably hear it every time your PSU will go into cc mode and you will want to destroy it.
Also you circuit will oscillate badly, because when lets say your load want to draw 3A while your CC set to 1.5A so the relay is gonna disconnect the load, so the cc circuit will see 0A doe gonna switch the relay on, so the current is going to shoot up to 3A and then over and over again, with NPN or MOSFET his happens much faster that it is easy to stabilize, with a relay.. not really.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version