For the reference there is no real need to plan with an 78L05 - it's normally lower stability than the cheaper TL431. The LM329 is 7 V.
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.
..So a few questions:
1) Is my V_SENSE voltage divider correct? If not where did I go wrong?
2) Is my resistor networks for IC1B Correct? I believe I should get 0-5 on inverting input (Based on 0-15Vout). I am guessing I need a 0-1V signal on I_SET for 0-1A but I am pretty sure I am wrong.
3) Are my Pots Correct? Assuming I want a 0-5V and 0-1V on the wipers.
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.
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...
The TL431 has to be wired this way when used as a Vref:
Your resistor's values:
The Vout will be the voltage on the Vset pot's wiper multiplied by the divider's ratio, in your case 51k/25k=3.04, therefore Vout = 3.04 x Vset. That is what I calculated so perfect. For final design Ill need to modify a tad as I want a bit more than 12V and my ref will be 4.096V. 15V was just a nice even number. 13.5V should be enough but Ill adjust those resistors on the final board and not on this one.
The SLowCC will be set to 1A with 1V on the Iset pot's wiper when all 4 resistors around the Isense opamp IC1B will have the same value AND the Rshunt will be 1ohm.
Once again I think my calculations are correct if I understand you right.
Note: above is valid when the 560k resistors are not populated.
I believe the 560K resistors are there if for some reason the SET lines ever loose their connection to the pot. I am not sure this would be a common failure point and it might be worth removing them.
The pots and resistors in series with them look ok.
Because of the 560k resistors there will be a small nonlinearity in the pot's scales.
I think these should be removed unless there is a good reason to keep them.
Also the Iset's pot wiper voltage will be influenced by the network around the Isense opamp.
I will buffer it as you suggested.
PS: the I_set's setting looks to be an issue
The setting is heavily influenced by the resistor's values in the Isense IC1B diff amplifier and the Vout.
The I_set has to be either
a) pretty low impedance, or
b) the resistors around IC1B have to be pretty large values.
It seems you need to buffer the I_set.
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.
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...
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
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.
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...
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 schematicThe 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.
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.
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...
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
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.
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
@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..
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: [Select]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
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