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Simulate LED-Backlight
Hello alltogether,
I want to simulate the LED backlight of a display and need help: I only have values of the LED voltage and current. Is it possible to simulate with these few parameters the backlight? If yes, how? I've read a lot about parametring your own LED, but I'm not sure if these few values are enough. Maybe someone of you can help. Greetings, Max |
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Re: struggling
Ganesan
I have been in the IC design business for over 30 yrs and in the
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component circuit design business for over 20 yrs. Exceeding the safe operating limit of a device even for a few pico seconds every clock cycle produces time dependent device failure.. My friend UN-KUN -MOON covered this in detail in a talk on Low Voltage CMOS circuits, a few years ago at the ISSCC.. The issue is not that you got away driving at 100mph.. the issues is that of when are you going to kill.? It is a matter of time.. Another company which tried to release +or-15v products (which normally require a 36V technology) in a 20-24 volts technology by playing circuit games learned a bitter lesson in field failures. In today's technologies , where operating limits are pushing the technology limits, it is even more imperative that these alarms be included in LTspice. Normally I don't like false alarms, because you got to search through the forest to find the needle; but in this case that is a better option than field failures.. cheers AG On 9/22/2011 10:11 AM, Joe Walsh wrote:
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Re: struggling
--- In LTspice@..., "E.A.Neonakis" <eaneonakis@...> wrote:
Hello Emmanuel A.Neonakis, You have it. An SMPS-IC with steady-detector is sufficient. Please try this example. Files > Examples > SMPS > buck_boost_efficiency.zip The necessary instructions are in the schematic. Best regards, Helmut Helmut wrote: |
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Re: struggling
Joe Walsh
--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:
I think I'll chime in on this one... It appears that what you want to do is perform SOA (Safe Operating Area) simulations? I'm an IC designer and I routinely violate the Safe Operating Areas on devices; my circuits only have to operate reliably for 10-100 hours out of a full IC lifetime of 10-15 years. I know, sounds wierd, but my circuits don't run in DC mode. If you are simulating a small circuit, LTSpice *may* work, but it will take some work on your part as I have not thought out thoroughly how this could be performed, nor have I actually tried it in LTSpice. However, I think it can be done with .MEASURE TRAN statements. If you are simulating a big circuit on LTSpice with 10's or 100's of components that could exceed the voltage ratings - forget it, too much work and headache. The "big boy" design tools such as Cadence Virtuoso allow for such capability, so I will describe it first. Each component: MOSFETs, capacitors, diodes, etc have 0-volt sources connected between each terminal. These voltage sources have acceptable range limits assigned to them along with a pre-canned error message. Once the circuit voltage exceeds the range on any of these voltage sources, the simulator outputs a message informing the designer that the voltage has been exceeded at time X. When the voltage comes back into the "safe" area, the simulator outputs another message indicating at time Y that the component is within normal range. The designer then has to wade through all the "errors" in the log file to find the real errors whose total time (Y-X) in the danger zone (i.e. exceeding SOA limits) exceed some threshold amount - purely up to the designer. The reason being that normal transient simulations may exhibit very short spikes that routinely exceed the limits, but rarely are longer than 1nsec in duration. So, in LTSpice, a designer could create .MEASURE TRAN statements to measure a voltage across a diode or FET for instance and capture when the voltage RISEs past the spec limit and also a corresponding .MEASURE TRAN statement when the voltage FALLs back within the spec limits. The designer then needs to parse the log file to measure the time delta between the two error messages to obtain the full time that the limits were exceeded. I've written such scripts (or had them written for me) to help weed out narrow spikes that were not of importance. I've routinely done this on large circuits and ended up with hundreds or thousands of "errors" that had to be checked manually - not a fun proposition and one reason I would not endeavor to try this on LTSpice that doesn't contain specialized tools or models to handle such behavior (minus what was already mentioned by Helmut in the previous post.) Once this is done, the designer can then plot the voltages (or currents) on the offending devices and fix his/her circuit. Sorry for the long post, Joe Walsh |
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Re: struggling
Dear Mr Sennewald,
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Is it necessary that the SMPS-IC from LTC is part of the design, or does it suffice that the IC is just present and trivially connected? If that is the case will you please be kind enough to suggest the simplest IC that will do the trick? I think a similar technique was suggested in order to enable the efficiency calculation and it worked. Best Regards, Emmanuel A.Neonakis Helmut wrote:
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Re: Monte Carlo beta and temp on 2N3904
Ganesan
I didn't get a confirmation ; so I am sending it again..
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-------- Original Message --------
Subject: Re: [LTspice] Re: Monte Carlo beta and temp on 2N3904 Date: Thu, 22 Sep 2011 09:26:35 -0500 From: Ganesan <dg1@...> To: LTspice@... Hi Tony, In 10000 iterations the value 900 never seems to show up.. Is this a binning issue of the histogram or is there a bias in the "MC " function? "mc(val, tol) is a function that uses a random number generator to return a value between val-tol*val and val+tol*val" Thanks for proving MC to be uniform. ( I would have assumed the default would be Gaussian.. A word or two on how you generated the histogram would be very useful.. Obviously this capability is not in LTspice) cheers AG On 9/22/2011 2:18 AM, Tony Casey wrote:
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Re: Monte Carlo beta and temp on 2N3904
Ganesan
Hi Tony,
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In 10000 iterations the value 900 never seems to show up.. Is this a binning issue of the histogram or is there a bias in the "MC " function? "mc(val, tol) is a function that uses a random number generator to return a value between val-tol*val and val+tol*val" Thanks for proving MC to be uniform. ( I would have assumed the default would be Gaussian.. A word or two on how you generated the histogram would be very useful.. Obviously this capability is not in LTspice) cheers AG On 9/22/2011 2:18 AM, Tony Casey wrote:
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Re: struggling
--- In LTspice@..., "ian.ballard@..." <ian.ballard@...> wrote:
Hello Ian, LTspice checks Iave and Vpk when you run a simulation with an SMPS-IC from LTC using the "steady" option in ".tran". If the limit is exceeded, the diode will be marked with a black exclamation mark in a yellow filled circular area in the schematic. In every other simulation you have to check it by yourself. Best regards, Helmut |
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Re: Half Bridge IRF7317 or Si4500BDY
Tony Casey
--- In LTspice@..., ?????????¡Á ¨¢???????? <bordodunovalex@...> wrote:
Hello Alex, Thanks for your advice, I hope it helps someone. I tried setting Delta to 0 and 1, in the Si4500B example, and confirmed by looking at the data that there was almost no difference. The difference was never greater than 0.45% for the drain current. Perhaps, as you say, it affects smaller devices significantly more. I'm not a CMOS designer, so I learned something today, and it's not even lunchtime yet! Regards, Tony |
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Re: Half Bridge IRF7317 or Si4500BDY
§¢§à§â§Õ§à§Õ§í§ß§à§Ó §¡§Ý§Ö§Ü§ã§Ñ§ß§Õ§â
Hi Tony.
I have for you is good advice. It applies to models of transistors. I recommend to remove the parameter DELTA. This setting adjusts the threshold of the transistor when the transistor width. It makes a significant contribution to the width of transistors of the order of several microns or less. With the width of the transistor more than 100 microns in the threshold correction is very small. You can verify this by your example. Note the time of calculation. DELTA exception parameter reduces the computation time and improves the convergence. Bordodynov. |
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Re: Half Bridge IRF7317 or Si4500BDY
Tony Casey
--- In LTspice@..., "pascalrenard85" <pascalrenard85@...> wrote:
Hello Pascal, I don't particularly want to single you out for criticism, even though I obviously seem to be. For each of these devices, the manufacturers provide SPICE models for both N and P channel devices straight from the website. It took me 3 minutes to find them; probably less time in fact than it would have taken you to write two messages asking if anyone had them. What does this tell us? Now, if your question had been along the lines: "...I tried the manufacturers' models, but they don't seem to predict the datasheet behaviour" (which might still be true), or "...LTspice hangs when doing a .tran analysis and then says 'time step too small'", people would be more than keen to find out why and help. Now because I don't want to be wholly negative, I've made an example for one of the devices (Si4500B), which you can find in Files>Temp. Your assignment is to do the same for the other. How's that for fairness? Regards, Tony |
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Re: Ignoring empty pin current
--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:
Thank you Helmut. Kerim |
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Re: Monte Carlo beta and temp on 2N3904
Tony Casey
--- In LTspice@..., "Tony Casey" <tony@...> wrote:
I was wrong, actually the Help now clearly states it is uniform distribution. Regards, Tony |
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Re: Ignoring empty pin current
--- In LTspice@..., "nicenchrispy" <hsuperchrispy@...> wrote:
Hello, I had sent the version Ring_2.zip to Mike and asked for an advice. He came back with the solution. --- from Mike --- There's an error in the way the library is set up. Remove ".lib 035a.lib" from the file csinv.asc . --- end --- I tried his advice and indeed the pin current can now be probed. Best regards, Helmut |
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Re: Monte Carlo beta and temp on 2N3904
Tony Casey
--- In LTspice@..., Ganesan <dg1@...> wrote:
Hello AG, By default, the seed is the same each time, so the MC series is repeatable. However, there is an option to randomise the seed. This was discussed in detail here quite recently; check the message archive. You're right, it doesn't say what distribution it uses, but it's not that hard to find out. So I did. I ran 10000 iterations of mc(1k,0.1). You can see the resultant histogram in Files>Temp. Regards, Tony Regards, Tony |
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Re: Half Bridge IRF7317 or Si4500BDY
Thanks Tony,
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Sorry if my question was not clear. Let me rephrase it. What I am looking for is lib/model of one of these half bridges running on LTSpice. Thanks for your feedback, Regards, Pascal. --- In LTspice@..., "Tony Casey" <tony@...> wrote:
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Re: New Member and Updated Help File
Lewis
Good news! I've finished converting the LTspice help file for use in
LTwiki <> . It's all ready for folks to comment and extend at will... You'll see it under "LTspice Annotated and Expanded Help" Iframes are generally a risk, but the Iframe Widget parses any suspicious activity, or so I'm told. The Widget succeeded in breaking about 80 characters in the original help, so I'm having to go make them '&' type characters. The wiki is free to export, so that may be a stand-alone method one day... still swimming in the on-line version details. btw... I'm not sure on the traffic, but I think it's about 100-200 visitors a day. Thanks everyone for the encouragement and support of this wiki. best regards, Lewis --- In LTspice@..., "Tony Casey" <tony@...> wrote: security products and experts, and were sometimes blocked. I presume that's not an issue now, or may be it never was? document that can be browsed without being online? It's possible it would be most useful if it could be used, at least initially, as an alternative to the standard help, for those people that don't or can't get on with the regular one; although I realise this would be much more problematic regarding rights, permission and good will, particularly since you have already obtained permission for it to be used on the Wiki. the help at all is hard enough, but the more "helps" there are, the less likely they will be to use any of them, I fear.
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Re: unknown parameter "wavefile"
John Woodgate
In message <j5dc45+pmdv@...>, dated Wed, 21 Sep 2011, Helmut <helmutsennewald@...> writes:
I have difficulties to read the wave-command above, because of "strange" characters. Maybe you have used a rare language code for text on your PC.That's the mangling you get with HTML, even on some web pages. The message reads OK in ASCII. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting. |
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Re: unknown parameter "wavefile"
John Woodgate
In message <94F7017DC15C44F7B9AF4FC9DE557E9E@KeithPC>, dated Wed, 21 Sep
2011, Keith Kawate <kkawate@...> writes: When trying to import a .wav file into a current or voltage source, IAccording to the Help, you can use 'wavefile' with I or V sources, B is not mentioned. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting. |
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Re: Monte Carlo beta and temp on 2N3904
Ganesan
The example MonteCarlo.asc suggests
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"mc(val, tol) is a function that uses a random number generator to return a value between val-tol*val and val+tol*val" It doesn't say what the distribution of "Val" would be (Gaussian, Uniform, Poisson,etc.)? Also no word on how the First Guess is made? Would different simulations result in different First Guesses? (If I run the simulation 10 times do i get 10 time the number of random samples or do i get 10 repetitions) Is there a comprehensive help anywhere on Monte Carlo Analysis? (Wiki and Help or nonos.) cheers AG On 9/21/2011 1:47 AM, Tony Casey wrote:
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