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Hi, I am trying to understand how MPPT works in a buck converter with resistive load by doing an LTSpice simulation. I have a PV model which works very accurately with a current sink load. And it works perfectly as in figure below (I can also change irradiance and its very accurate with the datasheet) But when I use a buck converter with a resistive load I can not achieve the left part of the IV curve. I am changing the duty cycle from 0 to 0.98 continuously (kind of) in 0.12s. I cant get the left part and I think this is logical because with a resistor at the output load there is no way that voltage will increase but current stay constant because resistor is a passive load. As in the figure below I added the figures in the folder "MPPT Resistive Load" Why I cant go to the left part of the IV curve ?

I can't remember when the UniversalOpamps first came into being, but there's a good chance there's been a bug in them from the start. Although I realised there was a problem long ago when I modified my copy of the old combined library file of UniversalOpamp2 to fix it, I had since forgotten about it. I failed to flag it up. However, when dealing with a query on another channel, I came across a significant shortfall in expected performance when using the latest stand-alone UniversalOpamp models. I was attempting to emulate the TI OPA2211 opamp with one. The datasheet for the OPA2211 states that the differential input resistance is typically 20kΩ, and the common mode input impedance is 2MΩ. Usually, the CM impedance makes little difference to the performance of most circuits because it is typically very high, so I was surprised when putting Rin=20k that the amplifier lost about 5dB of expected closed loop gain when the source impedance was significant, by comparison. I set up an impedance testjig for the UniversalOpamp3a that measured the input impedance in both modes. TL;DR: neither the differential or common mode input impedance was 20kΩ! The differential input resistance was 40kΩ, while the common mode input resistance was 10kΩ. WRONG ANSWERS! I've uploaded the test schematic: UniversalOpamp_bug1.zip The reason this happens is obvious when you look at the .subckt for UniversalOpamp3a: .subckt level3a 1 2 3 4 5 S1 5 3 N002 5 Q S2 4 5 5 N002 Q A1 2 1 0 0 0 0 N004 0 OTA G={Avol/Rout} ref={Vos} Iout={slew*Cout} Cout={Cout} en={en} enk={enk} in={in} ink={ink} Vhigh=1e308 Vlow=-1e308 C3 5 4 1p C4 3 5 1p R3 3 2 {2*Rin} noiseless G1 0 N002 N004 0 {1/Rout} R2 N002 0 {Rout} noiseless C1 N002 0 {X*Cout/Avol} R4 3 1 {2*Rin} noiseless R5 1 4 {2*Rin} noiseless R6 2 4 {2*Rin} noiseless G2 0 N004 4 N004 table(0 0 10 {2*slew*Cout}) G3 N004 0 N004 3 table(0 0 10 {2*slew*Cout}) R9 3 N004 {2*Rout} noiseless R10 N004 4 {2*Rout} noiseless .param Rout=100Meg .param Cout={Avol/GBW/2/pi/Rout} .model Q SW(Ron=10 Roff=10Meg Vt=0 Vh=-.1 Vser={Rail} ilimit={Ilimit} noiseless) .param X table(phimargin,29.4,3.5,32.1,2.9,33.8,2.6,35.8,2.3,38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,64.7,0.5,73,0.3,86.1,0.05) .param Avol=1Meg GBW=10Meg Slew=10Meg rail=0 Vos=0 ilimit=25m .param en=0 enk=0 in=0 ink=0 phimargin=45 Rin=500Meg .ends level3a Resistors R3-R6 implement the supposed input resistance. Essentially, both opamp inputs have resistors of 2*Rin connected to both supply rails, and by implication (with ideal voltage sources) - to ground. Therefore each input has a resistance of Rin to ground. But - and this is a big but: Rincm = (2*Rin//2*Rin)//(2*Rin//2*Rin) = 10kΩ Rindm = (2*Rin//2*Rin)+(2*Rin//2*Rin) = 40kΩ Since the default for the Rin parameter is 500kΩ, the issues this typically causes are small compared to other parameters with typical feedback network impedances. But with the Rin parameter set to match the desire differential input impedance commonly found on datasheets of (bipolar) low noise opamps, things can go awry with those same feedback components. This should be fixed. For practical components, the common mode I/P impedance is always higher than the differential I/P impedance. So, I'd say this was a bug. -- Regards, Tony

Hi, I tried to access LTspice Help Menu this morning to check the syntax of a Directive, but found that Help on the top bar of LTspice (left clicking on LTspice Menu) opens a Notepad file with the first lines as follows .... <?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE html> I'm sure this used to open a web page to the LTspice Menu. Is this a LTspice change or have I stuffed up some settings in my PC eg default settings?? I have dug around in App settings for Notepad .txt files but to no avail ... and my computer knowledge ends there. I am running Windows 11 (updated) and LTspice 24.0.12 At least I am trying to read the Help Menu .... :) :) , Ian

A dc-dc converter which has to supply an output voltage of 5 V with the output power from 2.5 W to 25 W. The variation of the output voltage of ±5% is acceptable, however, the high frequency ripple resulting from the switching process has to be limited to ±1% in order to control the noise problems. The converter is to operate from various dc sources within a range of 9 V to 16 V. You can assume that apart from the amplitude variation the input source is an ideal voltage source. The isolation is not required for this converter. The design includes a control system. The output voltage should be used for full feedback control. The only energy source in the system is the input source, therefore the power for the supply of the control block needs also to be drawn from the input source. As the power dissipation of the control block is very small compared with the load power, you can use a simple voltage regulator for this power supply. We can use the following components to design in LT spice using NE555 Resistors, including variable resistors, Capacitors, Inductors, Diodes, Zener diodes, Bipolar transistors, NE555 precision timer

I have uploaded 2 files to the temp section that model a 120 degree PTC thermistor, (the Epcos B59008C0120A040 from: http://www.epcos.com/inf/55/db/ptc_03/01770179.pdf ) including the nonlinear behavior, modeled as 4 different temperature coefficient resistors in series parallel. The model is in file PTC1.asc and the symbol is PTC_resistor.asy The model also includes the internal temperature rise and thermal time constant (which I guessed at, for lack of hard data). The symbol I created for it has a third node that produces a voltage that represents the internal temperature, with 1 volt = 1 degree C. The curve across the resistor symbol indicates the 4 slopes in the model. Everything I see this model doing looks pretty reasonable, but I would appreciate anyone going over the whole thing and making suggestions for improving it. This was my first foray into model building with Spice.

Hi All, In the uploaded file test.asc, I’m having a problem with a simulation getting stuck. Would appreciate a look. Thanks, Chris

Hello , My name is Mario Martinez , i want to know about sumulation circuits of squematics what represented for analisys of energy quality and energy efficient , i am ecuatorian

I have a fairly large model that I need to probe many of its components for Voltage, Current, and/or Power over a run period. Not difficult once I get the syntax correct, for individual parts withy clear net names, but it gets hairy, or at least tedious, to build up the .meas statements for many parts. In the plot pane, in Add Traces, I see a syntax like “Id(M1), Ie(Q1), I(u1:E1), etc.” Is there a form of that for Voltages, referring to other component pin numbers, “V(R1:1)” or the like? Dave

On 03/04/2025 09:26, jacfev via groups.io wrote: This is not such a simple question. What are your parameters for switching speed? Presumably rise and fall times? How about delays times? You can still have fast rise and fall times, but with a significant delay time if the transistor is driven into saturation. I would say that Bf is not one of the most influential parameters for speed. More important are the internal capacitances: Cje and Cjc, and transit times: Tf and Tr. Tr sets the reverse recovery time, i.e. charge storage in the base region on switch off - this is critical in saturated BJT switching circuits. To assess the speed, you need to .MEAS the rise and fall times at the output, and the turn-on and turn-off delay times referenced to the input source waveform. -- Regards, Tony

I am trying to build 6T SRAM using 20nm but when i run the simulation i am having the errors saying parameter level = 72 and also other bunch of errors. my 180nm file ran properly but when i tried for 20nm it's not working although i changed W/L ratio from L=0.18 ,W= 0.64 to L= 0.02 to W= 0.3. What should i do ?

I am trying to work with the CD4000_v.lib and am getting errors when trying to run. Would someone provide me some guidance as to what is set up in error? File uploaded to temp: CD_test.zip This is using the CD4013 as a counter. I have included the latest CD4000_v.lib and the CD4013B symbol from the files section to make it easy.

Hello , in the attacehd zipped file I have created a basic PNP biasing circuit . The simultion is in time domain , I added plots of different ports. Is a there a way by clever type of sweep to recreate the basic characteristics plot of the attached PNP plot? Current vs Vce plot. Thanks. /g/LTspice/files/Temp/03_01_25.zip

Dear all, I am trying to simulate a circuit with negative conductance using transistors and passive components. Does anyone have a circuit for this? Best regards. Sebastian

Hi, This should be the first time I will be using a SW to test a RIAA preamp response. I was thinking of copying the settings I use for testing power amps, but I am not sure it's correct. They are: PULSE(-.4 .4 0 10n 10n 25u 50u 10) Would they be fine for this new test? Thanks! Carlos

Am designing a low pass filter for the 20m amateur band, code below. (My apologies if this violates group protocol. Advise and I will adhere in the future.) I note that the display shows this model to initially be -6dB and wonder why. Again, truly a beginner. Links to appropriate material gratefully received. Thank you in advance. -- William, k6whp -------------------- "Cheer up, things could get worse. So I cheered up and things got worse."

Hello Everyone, I am trying to simulate very simple circuit using PyLTSpice. However, simulation takes too much time. It takes 1 second for the simulation to complete. Even when I increased the complexity of the circuit, time taken for simulation still stays approximately the same. I increased-decreased number of freuqncy points in my ac analysis, this had little to no effect on simulation runtime. I feel like most of the simulation time is spent reading-writing files. Does anybody has any suggestions that can be beneficial to speeding up the process? Currently, I am using LTSpice simulator, as seen on the third line. import time from PyLTSpice import SimRunner from spicelib.simulators.ltspice_simulator import LTspice # Create the netlist file (simple_lc.cir) netlist_content = """* Simple LC Resonant Circuit V1 N001 0 AC 1 L1 N001 N002 10uH C1 N002 0 1pF R1 N002 0 50 .ac lin 1500 40Meg 60g .save V(N002) .end """ # Save netlist netlist_filename = "simple_lc.cir" with open(netlist_filename, "w") as f: f.write(netlist_content) LTC = SimRunner(output_folder='/temp', simulator=LTspice) # init simulation runner for i in range(1,10): # iterate ove reverything t1 = time.time() LTC.run(netlist=netlist_filename) LTC.wait_completion() print(f"{t1 - time.time()} - Simrun")

I’m frustrated by failure of a time measurement I’m trying to make. My circuit generates a pulse train with parameterized width, Pw. I want to measure a delay, from a rising edge of one node, N0, to the next rising edge of another node, Nx. Due to a filter action, the amplitude of V(nx) is dependent upon a resistor whose value is stepped, from run to run. Because of that, I want to make the trigger (target) amplitude a variable, say 90% of the MAX() amplitude of node Nx. .meas VNx MAX V(Nx) FROM {5*Pw} TO {25*Pw} .meas T1 TRIG V(N0)=2.25 TD=3u RISE=1 TARG V(Nx)=250m TD=3u RISE=1 Measurement 1 correctly returns a peak value from say 0.5V to 4.5V. Measurement 2 returns a time that’s too close to the stat of Rise, instead of near the peak level. T1 Fails if I use this instead: .meas T1 TRIG V(N0)=2.25 TD=3u RISE=1 TARG V(Nx)={0.9*VNx} TD=3u RISE=1 Help?? Dave

Hi! I try to model an inductor using table. When i simulate this inductor, inductance value initially is changed according to the table that i include, but close to end off table inductance value didn't respect value from table. I try to change simulation time, and this make a negative effect on inductance (i don't know why!). Can someone help me with this? blob:/29cb438c-88fc-4eab-81d2-06d860dc8640 this is how inductance need to be changed with bias current. blob:/906f8161-46e1-4558-a50a-630d24f881b5 -- Circuit blob:/c5224e18-4379-40dd-b2de-90c8572811c4 -- Simulation result Text in InductorTable.txt: B1 tb 0 V = Table(I(V2), -70, 30u, -50.24, 30u, -49.75, 32u, -48.48, 37u, -46.35, 42u, -43.83, 45u, -41.60, 50u, -39.46, 57u, -37.51, 63u, -35.57, 69u, -33.52, 79u, -31.57, 86u, -29.52, 96u, -27.67, 107u, -26.10, 119u, -24.54, 127u, -23.26, 138u, -21.79, 149u, -20.13, 162u, -18.95, 173u, -17.67, 184u, -16.69, 195u, -15.50, 208u, -14.13, 222u, -12.94, 237u, -11.76, 250u, -10.67, 263u, -9.39, 276u, -8.20, 292u, -7.02, 305u, -6.13, 318u, -5.04, 330u, -3.86, 344u, -2.88, 351u, -1.80, 357u, -0.83, 362u, 0, 364u, 0.83, 362u, 1.80, 357u, 2.88, 351u, 3.86, 344u, 5.04, 330u, 6.13, 318u, 7.02, 305u, 8.20, 292u, 9.39, 276u, 10.67, 263u, 11.76, 250u, 12.94, 237u, 14.13, 222u, 15.50, 208u, 16.69, 195u, 17.67, 184u, 18.95, 173u, 20.13, 162u, 21.79, 149u, 23.26, 138u, 24.54, 127u, 26.10, 119u, 27.67, 107u, 29.52, 96u, 31.57, 86u, 33.52, 79u, 35.57, 69u, 37.51, 63u, 39.46, 57u, 41.60, 50u, 43.83, 45u, 46.35, 42u, 48.48, 37u, 49.75, 32u, 50.24, 30u, 70, 30u) My question is: Why inductance value didn't respect the table ? Thanks for your help ?

Hi, : May I ask about FFT feature ? If in a waveform viewer, I want to do FFT analysis of a chosen node, which may has multiple frequency components varying during whole simulation time interval. Can it be done to separate the whole simulation time into several intervals by eg: zoom-in feature, then run the FFT feature only for the "zoom-in"ed waveform data, to see what's the freq component in these data ? I say so, because, some applications , eg: OFDM modulation, may have the multiple freq components in modulated signal, and may vary the amplitude depending on transmitted data in different time interval. It helps to analyze if FFT could do analyzing of separated time interval in a single waveform. Is this feature supported ? Thank you very much. Best regards.

BF970 is an PNP transistor for UHF band (fT=1000 MHz) from Vishay. I visited Vishay site but there was no sign of BF970 (very old). I hope its spice model exists somewhere or of equivalent UHF PNP transistor. Thank you.