TheFishMan65
New member
I will try and remember 4994 rather than 200. Is there a trick to linking to a post on the page? I looked at but ondering if I have just missed a short cut. Thanks?
DIY LED driver for reef lighting
- Thread starter der_wille_zur_macht
- Start date
TheFishMan65
New member
Yes I knew that, but his link got back to the thread. So they can read the other 2 parts of the summary.
der_wille_zur_macht
Team RC
There are billions of 5v supplies, use anything you want really. Many of us are using these in conjunction with an Arduino or other DIY controller so we're tying into the 5v and GND from that. But really, anything will work - look for the word "regulated' in the supply's name or description and you can assume it will be OK but it's worth testing anyways.
Regarding the ground connections - yes, you want the negative (aka ground) connection from both DC supplies connected to the "GND" terminal on the driver board.
Regarding the ground connections - yes, you want the negative (aka ground) connection from both DC supplies connected to the "GND" terminal on the driver board.
Thanks DWZM! Now I might actually have to read this thread. I was trying to avoid the trap but it does not look like it now!
So, i am back to tell my driver story. The beginning of it, actually.
I actually have read the thread from page 1 to the last one this time. It took a week
I also have read all the datasheets mentioned here.
So, some time ago i asked why now use a simple scheme with PWM control and w/o current limiter because i used it before and it was fine.
Then i realized that in my application the current limiter was the battery i used, it simply cannot give more. So, for power supply application i NEED to make a current limiter.
I started to plan one (schematics and proteus simulation). Tried a simple one but it dissipated way too much power. So, i started to build a switching one. When i added the comparator i realized that i am building a chip from discrete components and i was still to add overcurrent protection and pwm control. Also, the efficiency was not very good. So, i stopped being silly and went to choose a good driver chip.
Now for the chip selection.
Here is the list of all mentioned drivers here:
CAT4101 - linear regulator
STCS1 - linear regulator
NCP3066 - 1.5A switching regulator, buck or boost (but not buck-boost), 250kHZ osc
ZXLD1366 - 1A, 60V buck
MBI6651 - 1A, 36V, buck
MIC3203 - 1A, 42V, buck
The problem is that i don't like all of them. Here is why:
Linear regulators are simple out of question. They need power supply very carefully matched to the Vf of the leds at certain current. Which is BTW fluctuates as it wants and is different for all led types. If, i will decide to increase or decrease current in the future, add or remove some leds i will need a new power supply. Also, i will need either match leds to the PS or buy a PS that can be regulator. If you look as such supplies you will see that they are pretty much never water protected and this is a no-go near a watter filled glass container. Best PS to use. i think, is a factory made notebook style one. It is pretty well protected from water, not very expensive, has high efficiency and high power output. So, no linears for me.
Now let's look at the BUCKs only. How much voltage i will need to provide to a driver if i want to driver at least 8 leds string? Aprrox 3.5x8=28V. What about 12 leds? Thats around 42V. Actually a few volts more than that in both cases. These are non standard voltages and i will need to buy not so popular power supply for it. Also, if i add more leds i might run into a problem in the future. Power supply issues are the same as for linears. I am not saying this is bad or anything, but it just does not feel comfortable for me.
The only boost here is NCP3066. The problem with NCP3066 is that i don't know how much boost it can give. How high can it go? With what efficiency? It has only 250Khz freq, so, for high boost it will need pretty big inductorl. Also, i don't like boost alone either, because then i am tied to a number of leds and ps voltage too because summ of Vf on leds MUST be higher than
PS voltage. Not versatile either.
So, the only option for me (me and only me, am not saying that everything else is bad) is a buck-boost configuration. And then i found this.
BEHOLD!
LTC3783 from LINEAR TECHNOLOGY
It does boost up to 54V, can be configured to use only one inductor in SEPIC configuration used external MOSFET to driver leds. The switching freq is up to 1MHZ + tons of neat features.
Has a good design examples in Design not 406 (dn406f.pdf - google will help)
It is very well documented in the PDF datasheet with examples and calculations.
Yes, it is not easy to solder (TSSOP package) and need tons of external components. But the components are dime a dozen and one such driver can drive at least 12 leds and i believe actually more.
For boost it can give 95% efficiency, for buck-boost 93%. Using such driver in buck-boost configuration i can choose any PS and then put any number of leds, even one just to see if the thing work (though the number of leds
will affect efficiency, so i need to calc everything to maximize efficiency for a prospected number of leds).
What do you think?
DATASHEET: http://cds.linear.com/docs/Datasheet/3783fb.pdf
APP NOTE: http://cds.linear.com/docs/Design Note/dn406f.pdf
Also, i looked at the CREE leds specs and i am lost why everyone drives them at 500-700mA? They are best driven at 1A and live long at that current.
I actually have read the thread from page 1 to the last one this time. It took a week
I also have read all the datasheets mentioned here.So, some time ago i asked why now use a simple scheme with PWM control and w/o current limiter because i used it before and it was fine.
Then i realized that in my application the current limiter was the battery i used, it simply cannot give more. So, for power supply application i NEED to make a current limiter.
I started to plan one (schematics and proteus simulation). Tried a simple one but it dissipated way too much power. So, i started to build a switching one. When i added the comparator i realized that i am building a chip from discrete components and i was still to add overcurrent protection and pwm control. Also, the efficiency was not very good. So, i stopped being silly and went to choose a good driver chip.
Now for the chip selection.
Here is the list of all mentioned drivers here:
CAT4101 - linear regulator
STCS1 - linear regulator
NCP3066 - 1.5A switching regulator, buck or boost (but not buck-boost), 250kHZ osc
ZXLD1366 - 1A, 60V buck
MBI6651 - 1A, 36V, buck
MIC3203 - 1A, 42V, buck
The problem is that i don't like all of them. Here is why:
Linear regulators are simple out of question. They need power supply very carefully matched to the Vf of the leds at certain current. Which is BTW fluctuates as it wants and is different for all led types. If, i will decide to increase or decrease current in the future, add or remove some leds i will need a new power supply. Also, i will need either match leds to the PS or buy a PS that can be regulator. If you look as such supplies you will see that they are pretty much never water protected and this is a no-go near a watter filled glass container. Best PS to use. i think, is a factory made notebook style one. It is pretty well protected from water, not very expensive, has high efficiency and high power output. So, no linears for me.
Now let's look at the BUCKs only. How much voltage i will need to provide to a driver if i want to driver at least 8 leds string? Aprrox 3.5x8=28V. What about 12 leds? Thats around 42V. Actually a few volts more than that in both cases. These are non standard voltages and i will need to buy not so popular power supply for it. Also, if i add more leds i might run into a problem in the future. Power supply issues are the same as for linears. I am not saying this is bad or anything, but it just does not feel comfortable for me.
The only boost here is NCP3066. The problem with NCP3066 is that i don't know how much boost it can give. How high can it go? With what efficiency? It has only 250Khz freq, so, for high boost it will need pretty big inductorl. Also, i don't like boost alone either, because then i am tied to a number of leds and ps voltage too because summ of Vf on leds MUST be higher than
PS voltage. Not versatile either.
So, the only option for me (me and only me, am not saying that everything else is bad) is a buck-boost configuration. And then i found this.
BEHOLD!
LTC3783 from LINEAR TECHNOLOGY
It does boost up to 54V, can be configured to use only one inductor in SEPIC configuration used external MOSFET to driver leds. The switching freq is up to 1MHZ + tons of neat features.
Has a good design examples in Design not 406 (dn406f.pdf - google will help)
It is very well documented in the PDF datasheet with examples and calculations.
Yes, it is not easy to solder (TSSOP package) and need tons of external components. But the components are dime a dozen and one such driver can drive at least 12 leds and i believe actually more.
For boost it can give 95% efficiency, for buck-boost 93%. Using such driver in buck-boost configuration i can choose any PS and then put any number of leds, even one just to see if the thing work (though the number of leds
will affect efficiency, so i need to calc everything to maximize efficiency for a prospected number of leds).
What do you think?
DATASHEET: http://cds.linear.com/docs/Datasheet/3783fb.pdf
APP NOTE: http://cds.linear.com/docs/Design Note/dn406f.pdf
Also, i looked at the CREE leds specs and i am lost why everyone drives them at 500-700mA? They are best driven at 1A and live long at that current.
der_wille_zur_macht
Team RC
It looks like a nice chip. It strikes me as very very similar to the LM340x chips from national, only in a slightly harder to solder package. If I were in your shoes I would definitely check them out before proceeding.
Efficiency and lifetime differences are significant. Of course, this is a personal choice and some people will value outright intensity more than efficiency or lifetime, but for me, I'm leaning slightly towards efficiency and lifetime, since I can get intensity by simply adding more LEDs. Check the output/current graphs in those datasheets - most of these LEDs will lose 30%+ efficiency going from 500 - 600mA to 1A.
I see your point about current and efficiency. I was thinking about current in terms of lifetime and that is not not really important i think, the lifetime is huge. But efficiency is important, especially when you say 30% is lost. I will have to recalc things.
As for LM340x series:
LM3401 - seems to be buck
LM3402 - buck
LM3404 - buck
LM3405 - buck
LM3406 - buck
LM3407 - buck
LM3410 - boost, SEPIC , but only up to 24V
So, nothing is close to LTC3783 amongst LM340x
As for LM340x series:
LM3401 - seems to be buck
LM3402 - buck
LM3404 - buck
LM3405 - buck
LM3406 - buck
LM3407 - buck
LM3410 - boost, SEPIC , but only up to 24V
So, nothing is close to LTC3783 amongst LM340x
der_wille_zur_macht
Team RC
Take another look at those datasheets - I know at least a few of them can be configured in boost, and most or all of them have HV versions that are good to 75v i/o - also, look back a few pages for a design by user theatrus, which iirc uses one of these chips in buck/boost topology.
terahz
1x10^12 Hz
What is the problem with using the adjustable power supply almost all of us use? (http://www.mpja.com/prodinfo.asp?number=16854+PS) It can be adjusted from ~18V to ~25V. Yes, it is not waterproof, but put it in a plastic container and it will be as much waterproof as a laptop one.
At least that's how I see it.
heis his quote:
"The efficiency reason and allowing multiple types of LEDs per supply was part of my motivation for the LM3404HV buck converter version."
As i said: LM3404 is a BUCK only regulator.
As for the datasheet. Here are the names of the parts copid from the datasheets (i actually also searched each for the "boost" word -non found in regards to a described driver):
LM3401 - Hysteretic PFET Controller for High Power LED Drive. Had to read the datasheet. It seems like boost only.
http://www.national.com/ds/LM/LM3401.pdf
LM3402 - 0.5A Constant Current Buck Regulator for Driving High Power LEDs
http://www.national.com/ds/LM/LM3402.pdf
LM3404 - 1.0A Constant Current Buck Regulator for Driving High Power LEDs
http://www.national.com/ds/LM/LM3404.pdf
LM3405 - 1.6MHz, 1A Constant Current Buck Regulator for Powering LEDs (can gen Vboost up to 26V)
http://www.national.com/ds/LM/LM3405.pdf
LM3406 - 1.5A Constant Current Buck Regulator for Driving HighPower LEDs
http://www.national.com/ds/LM/LM3406.pdf
LM3407 - pdf of protected, but it is 350mA buck
http://www.national.com/ds/LM/LM3407.pdf
LM3410 - 525kHz/1.6MHz, Constant Current Boost and SEPIC LED Driver with Internal Compensation
http://www.national.com/ds/LM/LM3410.pdf
I actually looked at all high current led drivers from National. The only SEPICS/buck-boosts are in 342x series and they give up yo 32V for boost and have tons and tons of external components.
Absolutelly nothing is wrog with them. I am sure they are good power supplies. I just don't like to idea of building everything for a certain voltage, the circuit must be adjusting to PS, not PS to the circuit, that's IMHO. And i don't like building a plastic box and they water seal all the holes in it and between the parts and the think if it will live okay with air flow at all.
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I just took a deeper look at LM3423. I was wrong about it. It can boost up to 75V and it has also status pin, which is nice to have and also high speed dimming (up to 50Khz) and the datasheet says it can be dimmed very low, basically it depend of the pwm generator.
If it is all so then LM3423 seems very interesting too. I am lost here, which one to select
http://www.national.com/ds/LM/LM3421.pdf
If it is all so then LM3423 seems very interesting too. I am lost here, which one to select
http://www.national.com/ds/LM/LM3421.pdf
kcress
New member
kcress
New member
And check Maxim-IC
http://www.maxim-ic.com/datasheet/index.mvp/id/5541
Check also their:
MAX16816.pdf
MAX16818.pdf
MAX16821-MAX16821C.pdf
MAX16831.pdf
MAX16834.pdf
Don't forget the Zetex:
www.diodes.com/datasheets/ZXLD1370.pdf
http://www.maxim-ic.com/datasheet/index.mvp/id/5541
Check also their:
MAX16816.pdf
MAX16818.pdf
MAX16821-MAX16821C.pdf
MAX16831.pdf
MAX16834.pdf
Don't forget the Zetex:
www.diodes.com/datasheets/ZXLD1370.pdf
LT3755 - yes, its very interesting too, open led condition signal here.
http://cds.linear.com/docs/Datasheet/37551fd.pdf
MAX16812 - PWM is only 100:1, 500khz switch. Docs suck.
MAX16816 - tqfn package only, no way i am messing with package at home on a home make (TT) PCB. I CAN do it, but this is just plain wrong and i am not in the mood for schmartboards.
MAX16818 - tqfn only
MAX16821 - tqfn only
MAX16831 - tqfn only
MAX16834 - has sop No ENABLE pin, has fault output, datasheet sucks. NO idea how much voltage can it boost safely.
ZXLD1370.pdf - i am lost in their datasheet. What max voltage can it boost to? Look at page 8. No 18V power supply and no more than 8 leds on the graphs. Why? Crazy.
Otherwise it is a good doc. The chip has fault state output info, good pwm resolution at 1KHZ. BUT not internal OVP, so, has to build OVP externally.
Actually, i find LINEAR device more appealing because their datasheet are more detailed, they describe how to select each component, give a lot of examples with real components. They also specify efficiency almost for each example application. I feel more confident with such docs. Big plus for Linear.
So, thus far i have:
LTC3783 - 100% sure it will work.
LT3755 - 100% sure.
LM3421 - pretty sure it will work nicely.
ZXLD1370 - is a nice one, but need to know how much it can boost and what the deal with the graphics on page 9.
All of the are TSOP package variants, so, it is hand solderable at home.
http://cds.linear.com/docs/Datasheet/37551fd.pdf
MAX16812 - PWM is only 100:1, 500khz switch. Docs suck.
MAX16816 - tqfn package only, no way i am messing with package at home on a home make (TT) PCB. I CAN do it, but this is just plain wrong and i am not in the mood for schmartboards.
MAX16818 - tqfn only
MAX16821 - tqfn only
MAX16831 - tqfn only
MAX16834 - has sop
No ENABLE pin, has fault output, datasheet sucks. NO idea how much voltage can it boost safely.ZXLD1370.pdf - i am lost in their datasheet. What max voltage can it boost to? Look at page 8. No 18V power supply and no more than 8 leds on the graphs. Why? Crazy.
Otherwise it is a good doc. The chip has fault state output info, good pwm resolution at 1KHZ. BUT not internal OVP, so, has to build OVP externally.
Actually, i find LINEAR device more appealing because their datasheet are more detailed, they describe how to select each component, give a lot of examples with real components. They also specify efficiency almost for each example application. I feel more confident with such docs. Big plus for Linear.
So, thus far i have:
LTC3783 - 100% sure it will work.
LT3755 - 100% sure.
LM3421 - pretty sure it will work nicely.
ZXLD1370 - is a nice one, but need to know how much it can boost and what the deal with the graphics on page 9.
All of the are TSOP package variants, so, it is hand solderable at home.
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kcress
New member
Nice synopsis!
I agree with all your findings.
Maxim data sheets don't suck but sure aren't great.
Almost without exception Linear data sheets are da-bomb.
Of course Linear parts all cost a small fortune. May be that's to pay the documentors.
But! If you want the best in assessment, nothing beats the National Work Bench tool to see if a part will do what you want.
I agree with all your findings.
Maxim data sheets don't suck but sure aren't great.
Almost without exception Linear data sheets are da-bomb.
Of course Linear parts all cost a small fortune. May be that's to pay the documentors.
But! If you want the best in assessment, nothing beats the National Work Bench tool to see if a part will do what you want.
Well, i don't know about the fortune. Nationals LM costs just 3$ less than LINEAR's LT. So, what's the big deal if yhou spend over 200$ on the leds anyway? This is simply in the cost estimation error margin. Now consider that LT3755 can output 75V at 0.7A! That's around 20 leds from one driver at 700mA (for cree xp-g). So, what is cheaper now?
By that tool you mean MULTISIM or something else?
I want to return to a question about LED efficiency at different current.
I look at the XP-G datasheet.
http://www.cree.com/products/pdf/XLampXP-G.pdf
Let's take XPGWHT-L1-0000-00FE4 (neutral white)
at 350mA - 100% of flux, 122lm, Vf=3V, P=1.05W, 116 lm/W, let's count it as 100% eff
at 700mA - around 190% ,232lm, Vf=3.2V, P=2.24W, 104 lm/W , eff 89%
at 1000mA - 250% flux, 305lm, Vf=3.3V, P=3.3W, 92 lm/W, eff 79%
So, it does not seems like 30% loss of efficiency at 1000ma. More like 20%, but that a lot too. 350mA would require too many leds, so, it seems like 700 mA is a good choice.
The interesting thing here is how some fight to gain extra 1-3% of driver efficiency while the led itself goes inefficient by 10%.
What i cannot find is a doc with a graph showing led life vs driving current.
I looked here: http://www.cree.com/products/xlamp_xpg.asp#xrcdocs
By that tool you mean MULTISIM or something else?
I want to return to a question about LED efficiency at different current.
I look at the XP-G datasheet.
http://www.cree.com/products/pdf/XLampXP-G.pdf
Let's take XPGWHT-L1-0000-00FE4 (neutral white)
at 350mA - 100% of flux, 122lm, Vf=3V, P=1.05W, 116 lm/W, let's count it as 100% eff
at 700mA - around 190% ,232lm, Vf=3.2V, P=2.24W, 104 lm/W , eff 89%
at 1000mA - 250% flux, 305lm, Vf=3.3V, P=3.3W, 92 lm/W, eff 79%
So, it does not seems like 30% loss of efficiency at 1000ma. More like 20%, but that a lot too. 350mA would require too many leds, so, it seems like 700 mA is a good choice.
The interesting thing here is how some fight to gain extra 1-3% of driver efficiency while the led itself goes inefficient by 10%.
What i cannot find is a doc with a graph showing led life vs driving current.
I looked here: http://www.cree.com/products/xlamp_xpg.asp#xrcdocs
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I just realized that i totally overlooked the safety issue. And if a boost regulator will boost up to 50V then it can possible give out 33mA through the body if everything is dry. If you are wet it can be a lot worse. 33mA.
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.
So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current
And the PS must be sealed and kept above the floor.
What do you think?
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.
So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current
And the PS must be sealed and kept above the floor.
What do you think?
kcress
New member
I just realized that i totally overlooked the safety issue. And if a boost regulator will boost up to 50V then it can possible give out 33mA through the body if everything is dry. If you are wet it can be a lot worse. 33mA.
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.
So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current
And the PS must be sealed and kept above the floor.
What do you think?
1) Yes certainly 50V is a hazard. If you have the heatsink properly grounded and a splash shield there should be minimal hazard.
2) If you short things the controller will drop the voltage to try to get down to the programmed current.
3) Off the floor is definitely better than on the floor.
