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| Bench CC/CV PSU Based on Daves uSupply (Not Anymore) |
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| not1xor1:
--- Quote from: Kleinstein on March 26, 2019, 08:41:39 pm --- The way with sensing across the one OPs inputs has an about 50% chance to work, depending on the OPs offset. So unless there are high resistors used to make sure the offset is defined sign the breadboard would not give a reliable answer. It still is near 50% chance, depending on the chip. The better way is to compare the outputs of the two regulating OPs instead. :horse: --- End quote --- are you kidding? The LEDs in my schematic diagram are connected to the outputs of the regulating opamps!!! and the output of the regulating opamp has to be at least 0.6V less than that of the saturated one otherwise the CC/CV mode switch would just not work. That voltage difference would be enough to switch on the LED connected to the saturated opamp (it is a sort of OFF indicator) while the other diode+LED pair would either be reverse polarized or have just not enough voltage to get any sensible current through. |
| iMo:
@not1xor1: Kleinstein is referring to the blinking version with the opamp which inputs are wired in parallel to the IC1B opamp. I would add 100nF ceramics in parallel to the 2x1000uF as well as to the output capacitor. With 8 opamps it seems the PSU is a bit over-engineered :) My simulation also shows the not1xor1's blinking works, there is a region where the both may lit (Iout pretty close to the SlowCC limit) but that situation is rather rare. With Vout from 124mV to 25V (30V V+) the current of each LED is always 0mA or 1.6mA with 15k resistor while blinking - see below. I would also leave the 560k there, you may or may not populate them. If somebody decided to use cheap potentiometers the resistors could become handy. I would go back to the 4opamps version, with the buffer for the I_set, buffer for the Vref, and the CC and CV opamps. And blinking according to not1xor1. PS: doublecheck the labels on your opamp power. Looks like both are V-. Use better names for the labels. PPS: Why your previous main V+ is now called V- in your schematics? That is weird..weird.. :palm: I would highly recommend you to rename it back to V+. Or better, when you are getting confused by too many sources with 2 chars long names, use the appropriate long names like for example: --- Code: ---Vpower+ or Vpower_P for the main 18V power Vpower- or Vpower_N for the -1.3V created on the 2 diodes Vopamp+ or Vopamp_P for the opapm's positive power Vopamp- or Vopamp_N for the opamp's negative power --- End code --- otherwise you may easily create a big mess on your PCB. Also do use underscores instead of spaces in the label names. 73 |
| Edd:
KCOPPH . . . . . Not so much that you made the PCB smaller . . .but MORE importantly was that you made that schematic of =https://www.eevblog.com/forum/projects/bench-cccv-psu-based-on-daves-usupply/?action=dlattach;attach=688722;image Smaller . . . so much that the alpha numerics aspects are now too small to reliably be able to read. You were so image density stingy /limiting, that your whole schematic page came out as ~ 805 X 621 pixels. Best that you doubled . . 2X'd that size . . . to then be fully readable. 73's de Edd I KNOW the speed of light . . . .So, what is the speed of dark? |
| KC0PPH:
--- Quote from: imo on March 27, 2019, 06:18:09 am ---@not1xor1: Kleinstein is referring to the blinking version with the opamp which inputs are wired in parallel to the IC1B opamp. I would add 100nF ceramics in parallel to the 2x1000uF as well as to the output capacitor. Easy enough to do. With 8 opamps it seems the PSU is a bit over-engineered :) I agree its getting a bit complicated. My simulation also shows the not1xor1's blinking works, there is a region where the both may lit (Iout pretty close to the SlowCC limit) but that situation is rather rare. I checked my wiring and it was wrong on the breadboard. I did notice the issue at low voltage (around 400mV) that the LED's did not light up. But I dont plan on really using it that low. With Vout from 124mV to 25V (30V V+) the current of each LED is always 0mA or 1.6mA with 15k resistor while blinking - see below. I would also leave the 560k there, you may or may not populate them. If somebody decided to use cheap potentiometers the resistors could become handy. Ill put them in the schematic as 100Meg and not populate them. I would go back to the 4opamps version, with the buffer for the I_set, buffer for the Vref, and the CC and CV opamps. And blinking according to not1xor1. Too Easy PS: doublecheck the labels on your opamp power. Looks like both are V-. Use better names for the labels. Opamps are Powered by OA_V+ and OA_V- PPS: Why your previous main V+ is now called V- in your schematics? That is weird..weird.. :palm: I think the issue is I am doing both a Print to PDF and a Screen Capture. I believe you are looking at the screen capture and its not very clear. If you look at the PDF you will see everything is correct. I agree its a bit odd that its not showing up correctly. I would highly recommend you to rename it back to V+. Or better, when you are getting confused by too many sources with 2 chars long names, use the appropriate long names like for example: --- Code: ---Vpower+ or Vpower_P for the main 18V power Vpower- or Vpower_N for the -1.3V created on the 2 diodes Vopamp+ or Vopamp_P for the opapm's positive power Vopamp- or Vopamp_N for the opamp's negative power --- End code --- otherwise you may easily create a big mess on your PCB. Also do use underscores instead of spaces in the label names. Eagle does not let you use Spaces in Net Names, plus the programmer in me always uses underscores. Once again I think the screen capture is not working correctly. PDF shows this clearly. 73 --- End quote --- 73's |
| Kleinstein:
With no variable load, there is no need for an extra buffer of the reference. So one could use 4 OPs as. 1 x CC mode regulator 2 x CV mode regulator 1 x Current set buffer 1 x CC/CV indication between the outputs of the first 2 OPs. Just using the LEDs with no OP between the outputs of the OPs would give a variable intensity and would not work with voltage near the upper limit. The CC limit can also be reached at a relatively high voltage. The TL431 itself can do some amplification like 2.5 V to 5 V or 7 V. The LM329 would be 7 V directly. So no extra OP is needed to buffer the reference. |
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