Electronics > Projects, Designs, and Technical Stuff
Help with how this PSU works. (With revised design)
xavier60:
A resistor could be put across the 10K Pot, ideally a 1.1K.
A green CV LED can be added. LEDs can and do go open circuit. I would rather have the LEDs not included in the control path, instead have them wired from the opamps' outputs to + control rail with their own dropper resistors.
Make provision for compensation components. A capacitor from ouput to inverting input of the CC opamp.
A capacitor and series resistor from output to inverting input of the CV opamp. 200mil footprint will do for the capacitors.
xavier60:
If the CC loop is found to be unstable and a compensation capacitor added, it will have the side effect of slowing down the current limiting response to sudden overloads. A diode across R13 should improve the response. Could someone test this in a simulation?
Evangelopoulos Panagiotis:
--- Quote from: xavier60 on May 13, 2020, 07:57:44 am ---A resistor could be put across the 10K Pot, ideally a 1.1K.
A green CV LED can be added. LEDs can and do go open circuit. I would rather have the LEDs not included in the control path, instead have them wired from the opamps' outputs to + control rail with their own dropper resistors.
Make provision for compensation components. A capacitor from ouput to inverting input of the CC opamp.
A capacitor and series resistor from output to inverting input of the CV opamp. 200mil footprint will do for the capacitors.
--- End quote ---
A capacitor to stabilize the CC loop sounds like a great idea since the original PSU died from a sudden load I think.
Will a 1uF do the job for both the CC and CV loops? How can I choose the value of the series resistor in the CV loop?
The cathode of the diode across R13 should connect to the inverting input right?
xavier60:
--- Quote from: Evangelopoulos Panagiotis on May 13, 2020, 09:16:56 am ---
--- Quote from: xavier60 on May 13, 2020, 07:57:44 am ---A resistor could be put across the 10K Pot, ideally a 1.1K.
A green CV LED can be added. LEDs can and do go open circuit. I would rather have the LEDs not included in the control path, instead have them wired from the opamps' outputs to + control rail with their own dropper resistors.
Make provision for compensation components. A capacitor from ouput to inverting input of the CC opamp.
A capacitor and series resistor from output to inverting input of the CV opamp. 200mil footprint will do for the capacitors.
--- End quote ---
A capacitor to stabilize the CC loop sounds like a great idea since the original PSU died from a sudden load I think.
Will a 1uF do the job for both the CC and CV loops? How can I choose the value of the series resistor in the CV loop?
The cathode of the diode across R13 should connect to the inverting input right?
--- End quote ---
That's right about the diode.
100pF and 47K for the CV opamp.
10nF for the CC opamp.
Do some test first to see if the parts are really needed.
I have just realized that R24 will have some affect on loop gain. I'm not certain how it should be dealt with if at all.
:Try to make space for a capacitor across R24.
Evangelopoulos Panagiotis:
--- Quote from: xavier60 on May 13, 2020, 09:33:36 am ---That's right about the diode.
100pF and 47K for the CV opamp.
10nF for the CC opamp.
Do some test first to see if the parts are really needed.
I have just realized that R24 will have some affect on loop gain. I'm not certain how it should be dealt with if at all.
:Try to make space for a capacitor across R24.
--- End quote ---
I added them and If I see they are not needed I'll leave them unpopulated. Same thing for the capacitor across the R24 pot.
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