| Electronics > Projects, Designs, and Technical Stuff |
| Bench CC/CV PSU Based on Daves uSupply (Not Anymore) |
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| Kleinstein:
--- Quote from: KC0PPH on March 26, 2019, 08:13:14 pm --- --- Quote from: not1xor1 on March 26, 2019, 05:38:22 am --- --- Quote from: jaycee on March 25, 2019, 11:24:42 am ---edit: AS others have said about the current limit LED, you can simply connect the cathode of the LED to I_SENSE and use a suitable limiting resistor. When the current limit is not in operation, the output of the opamp will be close to the +V rail, and the LED wont light. When it is operating, it will be somewhere near the -V rail and thus the led will light. --- End quote --- IMHO this is much simpler and provides both CV and CC monitoring. Notice that the opamp are ... criss-crossed as the voltage regulation opamp drives the CC LED and vice-versa. It is a sort of OFF indication and since either of those 2 opamps has to be ON... :) --- End quote --- I did this on the breadboard and it was inconsistent at best. I used RED LED's. I need to breadboard the way I have it on my schematic --- End quote --- 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: |
| KC0PPH:
--- Quote from: Kleinstein on March 26, 2019, 08:41:39 pm --- --- Quote from: KC0PPH on March 26, 2019, 08:13:14 pm --- --- Quote from: not1xor1 on March 26, 2019, 05:38:22 am --- --- Quote from: jaycee on March 25, 2019, 11:24:42 am ---edit: AS others have said about the current limit LED, you can simply connect the cathode of the LED to I_SENSE and use a suitable limiting resistor. When the current limit is not in operation, the output of the opamp will be close to the +V rail, and the LED wont light. When it is operating, it will be somewhere near the -V rail and thus the led will light. --- End quote --- IMHO this is much simpler and provides both CV and CC monitoring. Notice that the opamp are ... criss-crossed as the voltage regulation opamp drives the CC LED and vice-versa. It is a sort of OFF indication and since either of those 2 opamps has to be ON... :) --- End quote --- I did this on the breadboard and it was inconsistent at best. I used RED LED's. I need to breadboard the way I have it on my schematic --- End quote --- 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 --- Something like this? |
| KC0PPH:
Added all of the feedback into the schematic. I will be replacing the Diodes with SMD ones. I also made the board smaller. We will see how things go when I route it. The autorouter is not having much difficulties doing it, although the via count has slowly increased from 0 to 40. First batch of boards will be 2 layer. I will hand route the important things (high current and sense lines) and let the auto-router do the rest. For the final board it will be 4 layers which should make life much easier. |
| KC0PPH:
Was curious if JLC charges extra for lots o holes. Set Via to 0.2mm drill and 0.45mm dia and went crazy. Still $2USD for 10 boards. So I can do a decent job of via stitching the Top and bottom GND planes together. |
| not1xor1:
--- Quote from: KC0PPH on March 26, 2019, 08:13:14 pm --- --- Quote from: not1xor1 on March 26, 2019, 05:38:22 am --- --- Quote from: jaycee on March 25, 2019, 11:24:42 am ---edit: AS others have said about the current limit LED, you can simply connect the cathode of the LED to I_SENSE and use a suitable limiting resistor. When the current limit is not in operation, the output of the opamp will be close to the +V rail, and the LED wont light. When it is operating, it will be somewhere near the -V rail and thus the led will light. --- End quote --- IMHO this is much simpler and provides both CV and CC monitoring. Notice that the opamp are ... criss-crossed as the voltage regulation opamp drives the CC LED and vice-versa. It is a sort of OFF indication and since either of those 2 opamps has to be ON... :) --- End quote --- I did this on the breadboard and it was inconsistent at best. I used RED LED's. I need to breadboard the way I have it on my schematic --- End quote --- I only tested it in simulation, but I do not see how it can't work in the real world (I can't test it before may-june), provided you wired it properly and did not swap LED or diode polarity. Even if the individual opamps saturate to a slightly different high voltage, that voltage would always be higher than that of the unsaturated one otherwise the PSU would not be able to switch between CV/CC mode. It works (in LT spice) even with different LEDs (one green and one red) and different diodes in series (one 1N4148 and 4102) and with the voltage and current set on the verge of the switch (i.e. max out voltage min current over the limit). Just check the current through the LEDs vs. output current/voltage in the attached LTSPICE sim. |
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