Hi Folks,
I should probably know this but I am unsure...
I want to electrically modify the output of a buck converter board...
All the boards I have looked at use a monolithic buck chip with an additional diode, conductor and caps externally.
There is a single sens pin fed by a decider across the output. The values alter depending on the requirement of the chip but the one I messed with last maintains circa 1.4 V at the sens input.
I noted that current limiting was implemented by adding a diode, fed from an op amp output, that turns on and feeds current onto the sens pin, biasing it higher and thus doping the output voltage.
However what I want to do is have two distinct voltage set-points, with one as a default and one activated by either a low or high input, preferably a low as I want to control it with a PLC output and pulling it to ground seems like a better plan than driving it with 24V.
Now I could play with this but I am short on time and was hoping for a bit of guidance to reduce the tinkering time.
I considered an open NPN collector switch to pull sens lower via a trimmer but then realised that the threshold voltage of the transistor may cause problems...
Would it ? Can I do it anyway?
Is there a better way?
I am looking for outputs of around 22V & 15V with a 24V supply
I appreciate that some buck converters will require more headroom than that but that is a separate issue.
The application is to torque limit a small motor, whilst still retaining the ability to start it easily. Or increase the torque for any other reason for that matter.
Both voltages will need o be adjustable, although not via the PLC, and I may well install a bypass relay to deliver the full 24V rail.
Any thoughts and suggestions would be much appreciated.
Thanks,
Al
I should probably know this but I am unsure...
I want to electrically modify the output of a buck converter board...
All the boards I have looked at use a monolithic buck chip with an additional diode, conductor and caps externally.
There is a single sens pin fed by a decider across the output. The values alter depending on the requirement of the chip but the one I messed with last maintains circa 1.4 V at the sens input.
I noted that current limiting was implemented by adding a diode, fed from an op amp output, that turns on and feeds current onto the sens pin, biasing it higher and thus doping the output voltage.
However what I want to do is have two distinct voltage set-points, with one as a default and one activated by either a low or high input, preferably a low as I want to control it with a PLC output and pulling it to ground seems like a better plan than driving it with 24V.
Now I could play with this but I am short on time and was hoping for a bit of guidance to reduce the tinkering time.
I considered an open NPN collector switch to pull sens lower via a trimmer but then realised that the threshold voltage of the transistor may cause problems...
Would it ? Can I do it anyway?
Is there a better way?
I am looking for outputs of around 22V & 15V with a 24V supply
I appreciate that some buck converters will require more headroom than that but that is a separate issue.
The application is to torque limit a small motor, whilst still retaining the ability to start it easily. Or increase the torque for any other reason for that matter.
Both voltages will need o be adjustable, although not via the PLC, and I may well install a bypass relay to deliver the full 24V rail.
Any thoughts and suggestions would be much appreciated.
Thanks,
Al