XL6009 Step up Regulator Min volt difference?

[bhvm]

Dear all,
I would like to use XL6009 Step up Chip to convert 9.75v to around 10.8V. This is to drive a string to 3 LEDs in series from a Battery source. I would like to know what is the minimum DIFFERENCE between the Input and output voltage for the said Chip?

I studied the data sheets and also searched online but could not find anything concrete?

Kindly assist.
Thanks.

[stj]

Re: XL6009 Step up Regulator Min volt difference?

that will be down to the inductor and diode as much as the chip.

[budm]

Re: XL6009 Step up Regulator Min volt difference?

Looking at the app notes circuit, it looks to be around 2.5V.
https://cdn.badcaps-static.com/pdfs/...13c6dcea54.pdf
Build the circuit and experiment with it, vary the input and the load current through out the range to see. You also need to regulate the current through the LED string. You should also look into LED driver IC.

[bhvm]

Re: XL6009 Step up Regulator Min volt difference?

thanks for finding the voltage. I guess getting 10.8v from 9.75 is not possible then. I will have to add led in series- parallel matrix. the led I'm using are rated 300ma @ 3.6v. I made 3 series for effectively 10.8v.


I will match their current by gradually increasing the voltage on regulator till they start pulling 300ma per string.

[stj]

Re: XL6009 Step up Regulator Min volt difference?

lookup DF6113

[ben7]

Re: XL6009 Step up Regulator Min volt difference?

thanks for finding the voltage. I guess getting 10.8v from 9.75 is not possible then.

Either way, that's a strange voltage ... 9.75V ... what is that coming from?!

tI will have to add led in series- parallel matrix. the led I'm using are rated 300ma @ 3.6v. I made 3 series for effectively 10.8v.

Yep, I was just about to mention that you could re-arrange the LEDs.

I will match their current by gradually increasing the voltage on regulator till they start pulling 300ma per string.

The best thing to do is to use a constant current driver, otherwise the LEDs might take too much current once they warm up, or as they get older, and they might have an early failure.

-Ben

[budm]

Re: XL6009 Step up Regulator Min volt difference?

You should use constant current source for your LED to maintain the constant so the Voltage source does not have to be regulated, that is how the constant current power supply functions, the output Voltage is adjusted by the circuit to maintain constant current through the load.

[bhvm]

Re: XL6009 Step up Regulator Min volt difference?

dear all.

I have considered and discarded the idea of a constant current source due to the reason below-
1. I'm. running a LOT OF leds. 24 to be precise. all of them are rated at 3.6v, 300ma. that's a very high Vf From a 9.75v source. so running them as a series string is out of question.

2. I would either need too many constant current drivers or a huge driver with very high current if I'm to put them in Parallel. here, I dread current imbalances due to string failure or mismatch or otherwise. also the costs would shoot. up.

3. a simpler.option here was to use xl6009 to step up the voltage and run lights in reasonable series strings of 3 led and then parallel them all.

4. I guess if 10.8v is not possible, I'll put 6 leds in series and run them at 21 volts via step up.

[stj]

Re: XL6009 Step up Regulator Min volt difference?

http://www.linear.com/products/step-...t)_led_drivers

[budm]

Re: XL6009 Step up Regulator Min volt difference?

That is why we suggested you to use LED driver IC.
So 3 LEDs per string, 24 LEDs = 8 strings in parallel, so how do you suppose to balance all 8 strings when each string will have perfectly matched Vf? and also no current limit resistor per each string? Just parallel all 8, no feedback circuit? build it and see as the experiment and see what kind of result you will get when you start building 100 of units and see how consistence result you can get.
They do not make LED driver IC for no reason. LED's are current device.
BTW, @300ma you better look into heat management also, I would never drive at full current spec if you expect it to last.
You are talking about 1W per LED, so 24 LEDs you will have about 24W of power.Also Vf of the LED depends on the current, so look at the graph spec of the LED.

[bhvm]

Re: XL6009 Step up Regulator Min volt difference?

bud,
I don't think we've been. property introduced,
perhaps a look at my page will change your perspective-

http://m.instructables.com/member/bhvm/

also,

1)string failure is less of a problem in constant voltage circuits compared to constant current ones. in CC setup one string failure will push higher current thorough remaining strings, hence cascading failure.

2) I will always grossly underdrive leds. my. projects running leds at 300ma will usually have 1a capable leds.

3) I use aluminum for massive heatsinks.


4) anyways I found my answers, will post when my lights are done thanks.

[budm]

Re: XL6009 Step up Regulator Min volt difference?

"1)string failure is less of a problem in constant voltage circuits compared to constant current ones. in CC setup one string failure will push higher current thorough remaining strings, hence cascading failure." That is a known problem if you use simple design.
Not if you choose the correct design. Just do the search on how to drive LED Array.
https://www.badcaps.net/forum/showpo...&postcount=121
https://www.badcaps.net/forum/showpo...&postcount=117
look at the LED traffic lights some time, they have a way of not allowing the whole LED assembly to fail if some LEDs have gone out.
it is just the matter of your requirement of what you want to achieve and what compromise you will want to accept in the final products.
Cost, quality, reliability, manufacturing ability, etc. I am talking from the experience in many years in the manufacturing point of view.
Regulated Power supply + current limiter resistor + LEDs: that will be the most simplest way, It is all up to you.

[bhvm]

Re: XL6009 Step up Regulator Min volt difference?

"1)string failure is less of a problem in constant voltage circuits compared to constant current ones. in CC setup one string failure will push higher current thorough remaining strings, hence cascading failure." That is a known problem if you use simple design.
Not if you choose the correct design. Just do the search on how to drive LED Array.
https://www.badcaps.net/forum/showpo...&postcount=121
https://www.badcaps.net/forum/showpo...&postcount=117
look at the LED traffic lights some time, they have a way of not allowing the whole LED assembly to fail if some LEDs have gone out.
it is just the matter of your requirement of what you want to achieve and what compromise you will want to accept in the final products.
Cost, quality, reliability, manufacturing ability, etc. I am talking from the experience in many years in the manufacturing point of view.
Regulated Power supply + current limiter resistor + LEDs: that will be the most simplest way, It is all up to you.

I've worked with Osram to test and develop High CRI LED prototypes. Im also working to design an LED projector Low beam for street cars. However, there are times when you don't need much finesse and you want to keep the costs down. These are just DIY lights for hobby use. Not for mass production or Commercial use.

LEDs are my subject, Power Regulators not so much.

I've designed 100s of LEDs on Both Constant current and Constant voltage designs. Both are reliable depending on what you want. Constant current drivers are better where you have a lot of Input voltage. (Eg 10~20 LEDs from 240v AC Source).

For DC-DC use I will use either step-up or step down DC_DC rectifier. Once I tune the Regulator on my multimeter, They work for years without a sweat.

DC-DC constant current source is not favoured due to low Input voltage (Usually 5~12v) that limits my ability to put LEDs in Strings. Also, tons of things (Drivers) are not always available in India and that compells us to use whatever we have at hand.

I stopped using resistor for anything more than a 5mm LED. Resistors are simply waste heat and anything better like a 1W Luxeon star deserves more "respect" regarding a proper voltage.

[budm]

Re: XL6009 Step up Regulator Min volt difference?

Lots of LED driver ICs use boost converter that boost the input Voltages (that is typical topoloy used these day) up into >100VDC and also has constant current circuits built-in to drive many strings. I see that you use the LED with current limiter resistor as shown in your link. Too bad you cannot get the supply of ICs in your country, especially you are close to China source.
Like I said what is you final design decision as what you willl accept is up to you so why don't you just build and experiment with the circuits and find out what you do want to accept as the solution, do the costed BOM. BTW, since you work with Osram then you should have lots of info and you can adapt of what they use in your application, I do that all the time with app engr. from Osram, LITEON, CREE, TI, ST Micro, they provide lots of info on the design and do & don't.
BTW since you work with OSRAM to test and develop High CRI LED prototypes, then you should easily have access to the app Engr and be able to ask for suggestion about what you are trying to do I would think.
OSRAM application notes:
http://www.osram-os.com/osram_os/en/...otes/index.jsp

[budm]

Re: XL6009 Step up Regulator Min volt difference?

So much info out there, there are so much to learn unless someone already know everything that need to know about LEDs.
Electronics designs are always full of trade off and compromise.
App notes and App notes Engr. are your friends.
Cree:
http://www.cree.com/xlamp_app_notes









ON semi:
https://cdn.badcaps-static.com/pdfs/...fa93992782.pdf
https://cdn.badcaps-static.com/pdfs/...501b5f63e8.pdf

[bhvm]

Re: XL6009 Step up Regulator Min volt difference?

thanks for the wealth of information.

[mariushm]

Re: XL6009 Step up Regulator Min volt difference?

You will need to use proper current based led drivers.

With a plain boost regulator, if one led dies shorted, the remaining leds will receive more current than the set 300mA and they're probably light up much brighter or they'll downright burn out.

With LED drivers you can also put more leds in series, not just 3... settle for 6 or 8 leds in series and a driver for each string. With the right driver, you'd also be able to pwm the leds to adjust the brightness if you want to.

Here's a selection of led drivers that should fit your needs (just pay attention to minimum and maximum voltage they support) : http://goo.gl/4rmqYL

IS31LT3505 seems like a very fine boost driver for your needs, and relatively cheap too: http://www.digikey.com/product-detai...8-1-ND/2863846

AL8820 is also decent : http://www.digikey.com/product-detai...ICT-ND/5027703