Electronics > Projects, Designs, and Technical Stuff
Adjustable Voltage Supply: Schematic Concerns
LoveLaika:
Thanks for your reply. I found a 1-ohm sense resistor on digikey rated for 6 watts, but in the worst case, one trick I saw from the video is to take precision, high-watt resistors in parallel to get down to 1-ohm and not worry about power dissipation.
I see what you mean regarding the load connections. Depending on the load, that would be a problem. Working with the negative circuit by itself, it seemed okay when I was running it in SPICE, but now I see the problems that occur when the load output share a common ground. It's always the issue with the negative output current sense circuit that's causing all sorts of problems, and here I was hoping that I had it figured out. If I move GND to NEG_RETURN, R6 can't get an accurate measurement of the current going to the load from the negative side, and the feedback loop won't be able to accurately compensate for R6's voltage drop.
LoveLaika:
What do you mean by might be stable? You think there's too much capacitance at the output that's affecting the comparator op-amp? I went with high capacitance in order to reduce the output ripple.
LoveLaika:
So, with a capacitor by itself, it'd be an integrator. A capacitor/resistor parallel together would form an LPF. That's an interesting thought. I'll give that a try. Thanks for the comments. I'm learning more issues with my circuit as I read responses along with some ideas that I'd like to try out.
xavier60:
--- Quote from: LoveLaika on May 10, 2020, 02:16:00 am ---So, with a capacitor by itself, it'd be an integrator. A capacitor/resistor parallel together would form an LPF. That's an interesting thought. I'll give that a try. Thanks for the comments. I'm learning more issues with my circuit as I read responses along with some ideas that I'd like to try out.
--- End quote ---
A capacitor by itself forming a Miller Integrator works with linear designs, then it occurred to me that extra lag caused by the inductor would likely cause it to make things worse.
Putting a resistor in series with the capacitor allows some proportion response, reducing lag.
If the CC loop is really unstable and oscillating, the resulting audible squealing could be annoying.
David Hess:
--- Quote from: LoveLaika on May 10, 2020, 02:10:03 am ---What do you mean by might be stable? You think there's too much capacitance at the output that's affecting the comparator op-amp? I went with high capacitance in order to reduce the output ripple.
--- End quote ---
I mean the LC output filtering on the switching regulator may reduce the high frequency gain enough before a phase lag of 180 degrees is reached that the feedback loop may be stable.
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