Greetings,
I recently began work on a adjustable power supply using an LM350 adjustable voltage regulator. I am aware that the LM350 has short circuit protection but no visible means of indicated that it is experiencing overcurrent due to a shorted load. So, a comparator circuit was added with a red and green LED to indicate this but to also short the adjust pin of the regulator to ground which results in the voltage dropping to ~1.8VDC. When I built the circuit to test it, I shorted it to test the protection. It worked, some what but not in a way I expected. The voltage did drop however, with the short circuit in place of the load, high amps were still being drawn from the circuits power source. I am under the impression that the circuit needs to be redesigned to remove current but if I remove it, there will be no power being fed through the short circuit to feed the comparator to indicate a short. Is there anyone who can help with improvement of this design? The circuit is currently under space constraints so I'm trying to minimize adding too many components and I didn't want to build it using any 'exotic' parts.
Originally, the circuit used an 741 instead of a 321 OpAmp, but for some reason, I am having better results with the 741. A 2n5060 SCR is shown without a reset switch in the case of a trigger event for clarity. I tried using a BC547 but it didn't work for the regulator, the power settings were always stuck. :/
Is there a way to change it to a self resetting design? Whereas , it would pull power from the load, indicate a short but would return to normal operation once the load was removed or corrected. I was given an idea from someone to use a 1M ohm shunt to bypass the regulator to continue feeding the comparator but I didn't want to add a relay and use a second mosfet instead. Is this appropriate to do this or is there a better or more correct way to do this?
I have posted the current schematic below. Any help in this matter is greatly appreciated.
I recently began work on a adjustable power supply using an LM350 adjustable voltage regulator. I am aware that the LM350 has short circuit protection but no visible means of indicated that it is experiencing overcurrent due to a shorted load. So, a comparator circuit was added with a red and green LED to indicate this but to also short the adjust pin of the regulator to ground which results in the voltage dropping to ~1.8VDC. When I built the circuit to test it, I shorted it to test the protection. It worked, some what but not in a way I expected. The voltage did drop however, with the short circuit in place of the load, high amps were still being drawn from the circuits power source. I am under the impression that the circuit needs to be redesigned to remove current but if I remove it, there will be no power being fed through the short circuit to feed the comparator to indicate a short. Is there anyone who can help with improvement of this design? The circuit is currently under space constraints so I'm trying to minimize adding too many components and I didn't want to build it using any 'exotic' parts.
Originally, the circuit used an 741 instead of a 321 OpAmp, but for some reason, I am having better results with the 741. A 2n5060 SCR is shown without a reset switch in the case of a trigger event for clarity. I tried using a BC547 but it didn't work for the regulator, the power settings were always stuck. :/
Is there a way to change it to a self resetting design? Whereas , it would pull power from the load, indicate a short but would return to normal operation once the load was removed or corrected. I was given an idea from someone to use a 1M ohm shunt to bypass the regulator to continue feeding the comparator but I didn't want to add a relay and use a second mosfet instead. Is this appropriate to do this or is there a better or more correct way to do this?
I have posted the current schematic below. Any help in this matter is greatly appreciated.