Electronics > Projects, Designs, and Technical Stuff
Bench CC/CV PSU Based on Daves uSupply (Not Anymore)
jaycee:
C6 basically works as a "speedup" capacitor to improve the response time to voltage transients. Try removing it and you'll see the effect
KC0PPH:
To be honest I just downloaded LTSpice for the first time, so just getting started playing with it. I need to RTFM as I could not get the Load to work correctly. I replaced it with just a Resistor and made a few tweaks.
First I made a 1 Ohm Current Shunt -- I want a bit more of a voltage drop as I will be using a 13 bit ADC and just want a bit more flexibility to play a bit.
Second I tweaked the voltage dividers to achieve a 12V 1A @ 4.096. Some of the resistors are not a common value but I can figure something out. I need to now dig into some datasheets and figure out if I have transistors and diodes on hand that will work for this circuit to test out. I also have some learning to do as I have no clue about how a few parts of the circuit work.
Thank you for your help, i think this is going to be even more enjoyable.
-Keith
jaycee:
I noticed I goofed something - Q6 should be a 2N3904, and R9 should be 68 ohms.
I would not adjust the gain of the current sense amp like that - it is best to keep R5 = R6 and R3 = R4. Look up "differential amplifier"
Try R5=R6=1K2 and R3=R4=47K. For the voltage sense, try R18 = 68K, R8 = 8K2 and R19=39K
For odd values of resistors, you can simply put resistors in series... for example the 1K2's you could use 1K + 220
jaycee:
Also be aware that the higher the value of the current shunt, the more power it will dissipate. I would stick to 0.1 ohms... this is not a hard value to get. The resolution of your ADC doesnt really matter here as the gain of the current sense amp can be adjusted to suit, and you can connect the ADC to I_SENSE.
What problems did you have with the I1 load ?
If you're not sure how anything works, ask ;) As for transistors... the 2N3904/2N3906's are not critical and can be e.g. BC847/BC857. If you're breadboarding, BC546/BC556 are fine. BCP56 can be a BD139 - I simply chose BCP56 because it's a good surface mount part for the job. ES1D's can be 1N4004s. TIP35C can likely be any power transistor, TIP3055/2N3055 for example. Make sure that is heatsinked - an old CPU cooler is ideal!
KC0PPH:
Thanks for all the replies..
Well I found 2 2n3055 that I can use as the pass transistor. I have a bunch of 1n400x that I can use for the diodes. I also found some LM118 that claim they are good to use in A/D circuits. I found some LM324 and also LF147. Ill use the 324 to start with as they are cheap and I have a pile of them. I might have to wait to do this as I cant find ANY transistors. I though i had a pile of TO-92 2n390x...
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