LTSpice - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: June 26, 2017, 01:29:31 pm
content: Hi everyone,Why cant I get 15 volts or so on the lm317 output?--- Operating Point ---V(n001): 18 voltage-------------------------------------- V(n002): 3.28882 voltageV(n003): 2.55671 voltageV(n008): 0.0112638 voltageV(n004): 0.812597 voltageV(n009): 1.58001 voltageV(nc_01): 2.46341 voltage-------------------------------------------V(out): 1.64052 voltageV(nc_02): 0.812597 voltageV(n006): 1.64046 voltageV(n005): 1.64052 voltageV(dumpingcap): 2.4602 voltageV(n007): 1.63158 voltageIc(Q3): -8.40439e-013 device_currentIb(Q3): 8.3048e-013 device_currentIe(Q3): 8.88178e-015 device_currentIc(Q2): 1.66089e-012 device_currentIb(Q2): -1.65157e-012 device_currentIe(Q2): -1.11022e-014 device_currentIc(Q1): 0.00121647 device_currentIb(Q1): 0.00688217 device_currentIe(Q1): -0.00809864 device_currentI(C5): 2.47622e-017 device_currentI(C4): 8.19737e-016 device_currentI(C3): 8.2792e-020 device_currentI(C1): 1.8e-018 device_currentI(D3): 0.818979 device_currentI(D2): 0.818979 device_currentI(D1): 0.00121647 device_currentI(R3): 0.818979 device_currentI(R6): 8.07435e-020 device_currentI(R5): 0.000348823 device_currentI(R4): 0.000348823 device_currentI(R2): 0.00155767 device_current---------------------------------------------------I(R1): 0.812597 device_currentI(V1): -0.820696 device_currentIx(u1:1): 0.820696 subckt_currentIx(u1:2): -7.61966e-006 subckt_currentIx(u1:3): -0.820688 subckt_currentIx(u2:VN): -8.25408e-006 subckt_currentIx(u2:CONTROL): -3.38813e-021 subckt_currentIx(u2:VP): 8.25408e-006 subckt_currentRegardsJPD

author: Ian.M
author_rank: Super Contributor
timestamp: June 26, 2017, 01:53:37 pm
content: What do you expect when you connect a LM317 to a load consisting of two diodes and a 1R resistor all in series? With 16V across it the LM317 model I have here limits its output current to 400mA for short-circuit protection.You appear to be using a different LM317 model, and you haven't supplied your LMC555 CMOS 555 model. When posting a LTspice sim here, if it relies on models and symbols not provided in a 'vanilla' LTspice IV install, make sure they are in the sim's folder and zip them up with the .asc simulation file. As a poor alternative, at least provide links to the extra models and symbols you have used.

author: Audioguru
author_rank: Super Contributor
timestamp: June 26, 2017, 03:42:19 pm
content: The voltage "doubler" with lots of ripple is overloading all the active devices since the R3 load is only 1 ohm.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: June 26, 2017, 06:55:13 pm
content: I gather among my folders....

author: mikerj
author_rank: Super Contributor
timestamp: June 26, 2017, 08:22:46 pm
content: The doubler may not even be running, just the two diode drops and the 1 ohm resistor is enough to drag the supply rail down before you even consider the effects of the doubler.

author: Ian.M
author_rank: Super Contributor
timestamp: June 26, 2017, 08:27:39 pm
content: The models and symbols missing from your "Chargeur 12v.asc" aren't in that zip file.I found your LMC555 symbol and model on the LTSPICE wiki:http://ltwiki.org/files/LTspiceIV/lib/sym/SBORKA/TIMER/LMC555.asyhttp://ltwiki.org/files/LTspiceIV/lib/sub/Sborka.libI've got no idea where you got the LM317 model as the symbol size doesn't match the usual one from the Yahoo group. Please locate the symbol "lLM317.asy" that you are using, and attach it and also open it in the LTspice symbol editor, do 'Edit Attributes' from the menu, and find whatever file is referenced on the 'ModelFile' line of the Symbol Attribute Editor and attach that. Cancel out of the Symbol Attribute Editor and close the LM317.asy symbol without saving so you dont accidentally make any changes.There may be a problem with the Vcc connection to the LMC555. When I open "Chargeur 12v.asc", I notice the Vdd connection runs down the left edge of the LMC555 symbol. Dragging it away from the symbol to bring the wire in to the pin at rightangles as is normal practice reveals it extended past the pin down the edge by another grid increment. *PLEASE* don't draw wires to pins like that - its confusing at best and at worst may lead to the wrong pins being connected. There are also problems with the Out and Adg pins of the LM317 and the base of Q1 where the wire connects to the pin then continues into the symbol and you should tidy those up as well. If you have to, you can move the offending symbol out of the way with the 'Move' tool, grab the offending wire end by boxing it with the 'Drag' tool and drag it clear, move the symbol back the drag the wire end back onto the correct pin.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: June 26, 2017, 09:12:24 pm
content: Hi,The file was lm317.subThe corrected asc file.

author: Ian.M
author_rank: Super Contributor
timestamp: June 26, 2017, 10:13:33 pm
content: Well, I've tidied it up a bit more and added a few net names and .op voltage and current labels, and its obvious that Q1 is hard on, and is dragging the LM317 Adj pin to one LED Vf drop above ground, thus limiting the output to a maximum of 3.28VThe diodes and R3 are dragging the regulator output down. If you increase R3 to 100R, the regulator output goes up to 15.44V before the 555 and charge pump circuit drags it down. However the LM317 model you are using doesn't seem to be very stable and the LMC555 model certainly doesn't like a rapidly varying supply voltage so the simulation time becomes unreasonably long - its a brute and probably indicates its behaviour would be unpredictable in real life.I assume the 555 and charge pump circuit is meant to be a desulphator - you should get the basic CC/CV charging regulator circuit working first, then redesign the desulphator with a constant supply voltage to the 555, and maybe change to a pumped LC series resonance design powered by the incoming supply to the regulator so that it draws no net DC current from the battery. A choke to isolate the desulphator pulse from the regulator would also be helpful.Tidied up sim attached with all models and symbols reqquired. Caution: its *S*L*O*W!