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  1. #1
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    LFlex for XML and Li-ion

    Hi folks, I've been working on new flex driver prototype and since I've kicked off a run of boards I figure I may as well let you know what's going to be available in a few weeks...

    LFlex is a Linear Regulator style driver. It is NOT a stack of AMC7135 regulators but instead uses a high performance FET along with a uController to provide standard Flex features with constant current output care of the FET.

    The whole idea is to provide a solution for a single XML run for a single Li-ion cell where a buck driver would not be able to run effectively.

    The LFlex will have a few current tables to choose from with the highest at 3A for the XML. With an XML and its low Vf a single Li-ion cell will give good runtime and regulation throughout the useful battery voltage range. Dimming will be via adjustable current output with the lowest levels likely to be a PWM of a low current output - yet to be determined once I have production boards and port the flex UI-UNI2 firmware to them.

    LFlex will have battery monitoring (but no STAT output), it can warn via the main LED just like my other flex drivers. It'll have all the medium/low/cutoff settings as well. Given I'm thinking this would be a good helmet light solution, not having a separate STAT LED wouldn't be too much of a loss. The reason I can't provide the STAT is a) lack of pins on the uC and b) even if I use a higher pin count uC there is a lack of board real estate to fit it all while still keeping it a single sided board.

    LFlex will have the standard temperature monitoring of the other Flex drivers.

    Basically you can think of the LFlex as a D2Flex except the LFlex is regulated and provides voltage monitoring.

    LFlex will operate to at least 9V (likely higher after more testing of the current regulation scheme), so running 2 li-ion with 2 XML is also feasible.

    Size will be a hair under 20mm and components only on one side, bottom side should be thermally mounted to the housing/heatsink.

    Target cost is close to d2flex pricing since this doesn't have the expense of the switcher regulator core.

    I'll post up pictures when I get the production boards. I may post a picture of a kludged up d2flex mule - but it just looks like a d2flex with some bits and wires hanging all over it

    cheers,
    george.

  2. #2
    Light freak
    Reputation: scar's Avatar
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    Hey George, thanks for offering up yet another great driver option.

    20mm is still quite large to some people You ever think about making something smaller with maybe just two modes - 100% / 50%??

    Thanks again for all of the different options



    ****

  3. #3
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    This is great news George.
    I'm glad you posted as I was about to order a bunch of 7135 boards.
    I'll hold out for the LFlex for sure.
    Put me down for at least a few.
    Look, whatever happens, don't fight the mountain.

  4. #4
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    Now I'm happy! I'll take a few too. Can't wait to get my hands on them.

  5. #5
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    Quote Originally Posted by scar
    20mm is still quite large to some people You ever think about making something smaller with maybe just two modes - 100% / 50%??
    ****

    20 mm is pretty good size wise bearing in mind most usefull optics for th XML will be 20 mm or larger .

    and the heat handling properties of a case will determine the size of the light if you want to go to the max .


    Marvellous I see this being a cool driver for some pretty ace lights and single sided for ease of mounting .
    Thanks George

  6. #6
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    sounds bloody good to me... my search is over..
    I can run 2s1p with this new board george?

    If is a helmet light, who needs a stat led..
    cant see on top of my head

  7. #7
    Bigger is better!
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    Quote Originally Posted by troutie-mtb
    20 mm is pretty good size wise bearing in mind most usefull optics for th XML will be 20 mm or larger .
    Agree 100%

    Very good news, George!!

    Can you say anything about efficiency when running it from 1S vs 2S li-ion?

  8. #8
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    It's a linear regulator so the input current will be the same as the output current, except for the low modes where it gets more complicated due to the PWM. So efficiency will be Vout / Vin. Vout will be the Vf of the LED in most cases.

    For 1 li-ion cell with an XML at 3A

    3.3 / 3.7 = 89% efficient.

    Obviously it'll be less efficient in the first part of discharge of the battery when the voltage is above 3.7, and more efficient near the end when voltage is below 3.7. You also wouldn't want to run a single LED off a 2s pack. That would be terribly inefficient. Running 3 or 4 LEDs off 3 or 4 li-ion cells would start to get quite a bit less efficient as well because of the bigger difference between Vin and Vout.

  9. #9
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    1s2p?

  10. #10
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    George, is there a prepay list? in for 2

  11. #11
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    Microlight v3.0 just got a bit smaller!

  12. #12
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    MtbMac has the efficiency info correct. This is a Linear (hence LFlex) driver and is a great single LED / single Li-ion solution. Efficiency is basically output voltage/ input voltage.

    Dimming will of course extend runtime since it will lower output current.

    Anyhow, it's not the perfect driver (haven't figured out how to make an arbitrary 100% efficient buck/boost that's 12mm in diameter yet ), but it ain't half bad either.

    2 LEDs and 2 Li-ion is likely the most I'd recommend from an efficiency/heat loss perspective, beyond that a true buck or boost driver will do a better job. It would be hard to beat the efficiency of a h6flex pushing 3A to 3 XML's from 4 li-ion cells.

    The key to this design is small size and single sided for ease of mounting to a heatsink to dump excess heat from the current regulating FET versus a bucket of 7135 chips. The other benefit is dimming is via lower output current so more efficient than PWMing a bunch of 7135 chips.

    Total headroom to regulate at 3A output is about 0.15V (less at lower currents), so it is what I would consider a very low drop out regulator design.

    No prepay list - I've NEVER done prepays and never will. If you are interested, email me and I'll add you to a first come/first served contact list that I'll email to before offering the drivers for general sale.

    It'll be around 3 weeks before they are available, I'll have boards in about 1 1/2 weeks and then I need to port the production code and test and characterize the current tables etc etc.

    Thanks for your interest,
    cheers,
    george.

  13. #13
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    nice.. two xmls with to cells will be a good combination

  14. #14
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    Sounds good George. Will it have reverse polarity protection?

  15. #15
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    Quote Originally Posted by JezV
    Sounds good George. Will it have reverse polarity protection?
    Yes, ALL my drivers have had reverse polarity protection for several years now.

    cheers,
    george.

  16. #16
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    I'll join the queue and I bet it will be long one.

  17. #17
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    wow, this is awesome! Simply awesome! I could knock out single XM-L + Regina helmet lamps like nobody's business with this driver using a simple 1in.sq "sled" design. I was going to try a Quazzle board, but this should be as efficient, throw better and be ~1/2 the price.

    could you list the differences between the h6flex and the Lflex? Largely so I can justify to myself that getting the h6flex was a good idea but also so I can think about future dual XM-L builds as this will seriously simplify housing design over the h6flex (and even the b2flex).

  18. #18
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    I just sent a PM but basically put me in for two when available.
    thanks

  19. #19
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    H6Flex is a damn fine driver - it is very robust. It is a buck driver, it will do DC/DC step down conversion and is very efficient. It can output up to 6.7A fully current regulated. It CAN'T operate from a single l-ion cell.

    The LFlex is a Linear regulator style driver - it BURNS excess voltage as heat, i.e. it does not do DC/DC conversion. Where it will excel is when input voltage is reasonably well matched with output voltage. It will also operate to low voltages before dropping out. I doubt you'll find a switcher based LED driver that can run from a single li-ion and drive a single white LED at 3A and do it efficiently. Such a switcher based driver would be very challenging to design and then to try and fit it into a 20mm envelope etc etc....

    So, the LFlex will fill in nicely where you have a single LED and single li-ion or 2 LEDs and 2 li-ion running at up to 3A.

    I don't see the LFlex stealing the H6Flex thunder, rather it filling in a gap at the single/double LED/cell end of the lighting spectrum. It will allow for a fully regulated and dimmable compact helmet type light where weight/size is an issue. It will provide voltage monitoring/warning/protection and thermal monitoring/protection while still having the same identical user interface as the rest of the flex drivers. So, you could have a bar mounted light and a helmet mounted light and operating the two would not require thinking what interface is on what light...

    The real comparison is the LFlex versus the D2Flex.

    cheers,
    george.

  20. #20
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    Quote Originally Posted by georges80
    H6Flex is a damn fine driver - it is very robust. It is a buck driver, it will do DC/DC step down conversion and is very efficient. It can output up to 6.7A fully current regulated. It CAN'T operate from a single l-ion cell.

    The LFlex is a Linear regulator style driver - it BURNS excess voltage as heat, i.e. it does not do DC/DC conversion. Where it will excel is when input voltage is reasonably well matched with output voltage. It will also operate to low voltages before dropping out. I doubt you'll find a switcher based LED driver that can run from a single li-ion and drive a single white LED at 3A and do it efficiently. Such a switcher based driver would be very challenging to design and then to try and fit it into a 20mm envelope etc etc....

    So, the LFlex will fill in nicely where you have a single LED and single li-ion or 2 LEDs and 2 li-ion running at up to 3A.

    I don't see the LFlex stealing the H6Flex thunder, rather it filling in a gap at the single/double LED/cell end of the lighting spectrum. It will allow for a fully regulated and dimmable compact helmet type light where weight/size is an issue. It will provide voltage monitoring/warning/protection and thermal monitoring/protection while still having the same identical user interface as the rest of the flex drivers. So, you could have a bar mounted light and a helmet mounted light and operating the two would not require thinking what interface is on what light...

    The real comparison is the LFlex versus the D2Flex.

    cheers,
    george.
    never doubted the pedigree of the h6flex, I don't regret buying it at all. I do now understand the whole linear regulator thing better though - they key, as you say, is matching LED and cell no., i.e. 1 LED, 1S; 2 LED, 2S. I'm guessing that you can't do 3 LED/ 3S as the power burned as the Vin/Vout difference at that LED no. would be too great to safely dissipate, correct?

    I think this will make designing single LED lights (commuter or helmet) so much easier - I wish this was around when I started ordering parts for a bunch of commuter lights I'm building Still, there's finally a reason for people not to use those somewhat suspect DX/KD 7135 drivers

  21. #21
    Barrington Womble
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    George

    this is the good news my new year needed. Just started a new xml project but the most suitable driver I could find was from Shining Beam, and this was the best of a bad bunch!! I now have no excuse not to stand at the lathe in the cold workshop and get the basic housing sorted. Cheers.

  22. #22
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    Now all we need is a source for a cheap 4p li ion battery pack
    DIY LED Bike Lights:
    A few Dynamo builds and some Small battery lights

  23. #23
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    IMHO the diameter is too big. It should be matched with the cell - 18mm
    CNC LED light housing for DIY projects

  24. #24
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    Quote Originally Posted by zemike
    IMHO the diameter is too big. It should be matched with the cell - 18mm

    The diameter is what it is to fit the electronics on board. If you want 18mm, then I can leave off the bits that make it work and make the solder pads tiny or I can put components on both sides of the board and you can kiss away a good thermal path. Then you would end up with a kludge like a multi AMC7135 board with components on both sides and no good way to get rid of the heat.

    I already squeezed to make things fit well on this board AND to provide a good thermal path AND to allow the average person a chance of soldering the leads on that can carry 3A in/out of the driver. A round board is already a challenge from a layout perspective since you basically have square/rectangular components.

    Given the size of the optics needed and that the driver would have to be in that housing anyway if you want thermal protection and to minimize voltage drops in the system - i.e. a remote battery pack would not be a good idea either unless you are running THICK wires to deal with the up to 3A current draw... That light housing itself can't be too tiny - you will be dealing with upwards of 10 - 12W of heat you need to dissipate with a single XML at 3A....

    Here's a CAD layout of the board. Take it into photoshop etc and scale it to 0.78" and print it one to one and then see how tight everything is. Then draw an 18mm circle on it and that's what would have to be removed from the design



    cheers,
    george.

  25. #25
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    georges80
    George, am I right thinking that LFlex will work properly with 2 serial XML from 2s (7.4 v) LiIons?

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