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Thread: DX Driver Board Tests - Efficiency Results Included

  1. #1

    Default DX Driver Board Tests - Efficiency Results Included

    Update :

    10/06/2010 - DX 1.5V~4.2V 3W Step-Up (Boost) Driver SKU.25505, Test results at post #79
    02/08/2010 - DX 5V~8.4V 15W 5*Cree Step-Up Driver SKU.26106 Test [Detailed] at post #46
    11/20/2009 - I have drawn back the PT4115 chip results for checking them again.
    11/17/2009
    - Test Results for 2*, 3*, 4* serial connected XR-E driven with Mr16 1*3W Driver. results on #28
    11/16/2009 - Added efficiency table for Mr16 1*3W Driver (PT4115 Chip) at post #23

    Hi Friends,

    I have ordered these DX sku.3256 boards about 40 days ago at last I have received them. Theese were totally revised versions, no more using Zetex C310, uses new chip with lots of advantages. I make some measurments. I have measured standart configuration. Add a 1 Ohm paralel resistor to R27 sense resistor and make some more measurments.

    At standart config board gives a solid 0,91A from 4V to 16V
    At hacked config board gives a solid 1.16A from 4V to 16V

    +No heat (Also hacked 1.16A config)
    +Very solid I out
    -Sense resistor eats the efficiency (but also has 90% efficiency)

    And measurment table,



    Note: I wrote "Efficiency of Board without Sense resistor" this is a wrong expression I think. If we have a chance to use board without Sense resistor (But we can not) and all the power (Pout and Psense) goes to a LED, what would be the board efficiency.

    Thanks,
    EpRoM
    Last edited by eprom; 10-06-2010 at 03:41 AM. Reason: P sense 1.16 Corrected,

  2. #2
    Flashaholic* VegasF6's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by eprom View Post
    Hi Friends,

    I have ordered these DX sku.3256 boards about 40 days ago at last I have received them. Theese were totally revised versions, no more using Zetex C310, uses new chip with lots of advantages.
    Don't leave us in suspense, what chip does it use now? By the way, the last time I ordered these I think they actually had a C300, but nearly the same.

  3. #3

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    It is hard to say because chip top was sanded.

    But my suggestion is AX2002, because I used PT4105 at 1 amp level and efficiency was only 70%. AX2002 datasheet specs are very close to my findings.

    Datasheet of AX2002 = http://www.micro-bridge.com/data/Axelite/AX2002.pdf

    Edit:

    I have controlled the Pt4105 and PT4115 datasheets. Neither of them can drive led at ~1A with R27 resistor. Only AX2002 can do this.

    PT4105 can drive led ~700ma with R27
    PT4115 can drive led ~350ma with R27

    Quote Originally Posted by VegasF6 View Post
    Don't leave us in suspense, what chip does it use now? By the way, the last time I ordered these I think they actually had a C300, but nearly the same.

  4. #4

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    I think you have a small math error. Your calculation of Pout is the power draw of the LED, based on Vf*If. That number should not change regardless of what the sense resistor loss is. The LED is still going to draw the same power.

    To estimate what the efficiency could be for an ideal sense resistor setup that draws no power, you should subtract Psense from Pin to get the amount of power that the driver would have to deliver without being weighed down by any sense resistor losses.

    It is interesting that your measured drive currents of 0.91A and 1.16A are almost exactly what you'd calculate based on the sense resistor formula in the AX2002 datasheet.

    Check out KD1640. That driver also uses the AX2002 buck IC.

  5. #5

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Hi Justin,

    System efficiency calculated by Pout/Pin
    Ideal System calculated like all the Power (Pout and Psense) goes to an virtual LED. This Pout and Psense feed by Pin at last. Yes you are right but I can not get the measurments/numbers of system without sense resistor so this is the only way I can do.

    Thanks for your comments,
    EpRoM

    Quote Originally Posted by Justin Case View Post
    I think you have a small math error. Your calculation of Pout is the power draw of the LED, based on Vf*If. That number should not change regardless of what the sense resistor loss is. The LED is still going to draw the same power.

    To estimate what the efficiency could be for an ideal sense resistor setup that draws no power, you should subtract Psense from Pin to get the amount of power that the driver would have to deliver without being weighed down by any sense resistor losses.

    It is interesting that your measured drive currents of 0.91A and 1.16A are almost exactly what you'd calculate based on the sense resistor formula in the AX2002 datasheet.

    Check out KD1640. That driver also uses the AX2002 buck IC.

  6. #6

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Yes, I know that efficiency is Pout/Pin. What I am saying is that when you calculate your efficiency without the power drain from the sense resistor, your efficiency equation should be Pout/(Pin-Psense), not (Pout+Psense)/Pin.

    Pout is a constant. If you have a constant current driver and it sends If to the LED (resulting in a voltage Vf), then Pout will be If*Vf. It doesn't matter if you have a sense resistor power loss or not. Adding Psense to Pout doesn't make any physical sense.

    With a sense resistor power loss, the driver has to generate that much more power so that it can deliver Pout to the LED. That means Pin includes the sense resistor power, which reduces the efficiency percentage. By subtracting Psense, you estimate the higher efficiency you'd get if the driver didn't have to generate the extra wattage to feed the sense resistor.

  7. #7

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    I looked like this,

    Isense resistor connected serially to the LED so IC work like pushing a LED with 3,61V Vf + 0,25V Isense resistor. I mean system work like pushing a LED with 3,86V Vf at 1.16A. So I used this equation to calculate and this is my point of view.

  8. #8
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    So with that in mind, has anyone done the actual numbers?

  9. #9
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Nice work. Could you measure 4 V and 4.5 V input please.

    Quote Originally Posted by eprom View Post
    I have controlled the Pt4105 and PT4115 datasheets. Neither of them can drive led at ~1A with R27 resistor. Only AX2002 can do this.

    PT4105 can drive led ~700ma with R27
    PT4115 can drive led ~350ma with R27
    The PT4115 needs over 8 V anyway.
    No, a torch does not always mean flames.
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  10. #10

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by eprom View Post
    I looked like this,

    Isense resistor connected serially to the LED so IC work like pushing a LED with 3,61V Vf + 0,25V Isense resistor. I mean system work like pushing a LED with 3,86V Vf at 1.16A. So I used this equation to calculate and this is my point of view.
    But what is the source of the feedback pin voltage? Isn't it from the reference voltage built into the IC, with an error amplifier providing the feedback? Hence, this power drain seems to be an inherent part of the driver, not the load. It also seems more traditional, at least IMO, to consider driver efficiency as the ratio of the power drawn by the device/load of interest (the LED) to the power drawn by the driver. It would seem less sensible to include other sources of power draw in the numerator. Also, if you are considering a hypothetical driver that doesn't burn any wattage in the sense resistor network, then shouldn't you be subtracting off that wattage, not adding it in, when making that efficiency calculation?

    Either way, the difference in the calculated efficiency is small. Just trying to use the right formula.

    BTW, do you have a photo of the driver?
    Last edited by Justin Case; 11-12-2009 at 06:48 PM.

  11. #11

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Hi TorchBoy,

    The board starts to regulation at ~0,5V over the Vf.

    At 4,08V board start to hold regulation for my sample.

    EpRoM

    Quote Originally Posted by TorchBoy View Post
    Nice work. Could you measure 4 V and 4.5 V input please.


    The PT4115 needs over 8 V anyway.

  12. #12
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by eprom View Post
    The board starts to regulation at ~0,5V over the Vf.

    At 4,08V board start to hold regulation for my sample.
    Ooh, that's nice. Thanks for checking that. I wonder how low it'll go. Do you have any LEDs with a lower Vf? And will it happily drive more LEDs at once?
    Last edited by TorchBoy; 11-13-2009 at 04:00 AM.
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  13. #13

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    I am using it with Cree MC-E parallel wired, Vf= 3,10V @1.16A on 4D maglite. Input is 5.3V 0,77A with Energizer D size Alkalines.

    EpRoM

    Quote Originally Posted by TorchBoy View Post
    Ooh, that's nice. Thanks for checking that. I wonder how low it'll go. Do you have any LEDs with a lower Vf? And will it happily drive more LEDs at once?

  14. #14
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Sounds ideal. When will that setup drop out of regulation? Will 16 V input drive the four dice in series?
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  15. #15

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by TorchBoy View Post
    Do you have any LEDs with a lower Vf?
    I have a KD1640 (another AX2002-based buck driver) order in-transit and plan to test it on an XP-G R4. On another XP-G R4 driven by 3xAMC7135, I measured Vf ~3.1V (tx101 also measured 3.1V when using an SOB1000). With an SOB1227 (1196mA measured drive current), I got Vf ~3.3V.

    I have another AX2002-based KD1640 driver that's mod'ed to deliver 1400mA, and it runs a 2S2P MC-E in regulation at ~7.0V in (Vf ~6.2V). In comparison, an SOB1227/2S2P MC-E reaches regulation at ~8.1V (Vf ~6.3V) and an SOB1000/2S2P MC-E reaches regulation at ~7.6V (Vf also ~6.2V). The SOB1227/MC-E case seems anomalous -- not sure why the voltage overhead is so high. The SOB1000/MC-E overhead seems in-line with what I'd expect.

  16. #16
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Is the overhead related at all to the drive current or the number of LEDs driven? Or is the overhead fixed? I wish I had a better test bed.
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  17. #17

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    The overhead probably is weakly/moderately dependent on drive current, to the extent the "parasitic" voltage of relevant components depends on current. For the SOB, I think that the two biggest drivers are 1) the buck IC duty cycle is not 100% (it's 87% max), and 2) the Schottky diode forward voltage spec is relatively high at 0.5V. For example, for voltage overhead component #1, the dependence of the voltage overhead on drive current is through the resultant LED Vf. The voltage overhead = Vf/0.87 - Vf ~ 0.15Vf, and Vf increases as drive current increases.

    I re-tested the SOB1227/2S2P MC-E setup and it looks like I get full regulation at about 7.7V, not 8.1V. This new value seems reasonable to me. Not sure what the reason is for the discrepancy, other than I did re-work the solder joints to the MC-E a while ago. The Vf I reported above was measured after the re-work but the bench power supply testing was done before the re-work. So maybe the solder connections to the LED were not optimal, resulting in a high contact resistance.
    Last edited by Justin Case; 11-18-2009 at 12:15 PM.

  18. #18
    Flashaholic* Aircraft800's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    I thought you were talking about this one
    SKU 26110 18V 5W Cree Circuit Board for Flashlights (16.8mm*5.5mm) ?


    Which one is the R27 sense resistor? ^

    I thought it was the new Kennan replacement?
    Last edited by Aircraft800; 11-13-2009 at 05:40 PM.

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    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by Aircraft800 View Post
    Which one is the R27 sense resistor? ^
    The one marked R22.
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  20. #20

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    The board I have tested is http://www.dealextreme.com/details.dx/sku.3256

    You can see the R27 on this photo
    http://www1.dealextreme.com/producti...sku_3256_3.jpg


    Quote Originally Posted by Aircraft800 View Post
    I thought you were talking about this one
    SKU 26110 18V 5W Cree Circuit Board for Flashlights (16.8mm*5.5mm) ?


    Which one is the R27 sense resistor? ^

    I thought it was the new Kennan replacement?

  21. #21
    Flashaholic* Aircraft800's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Thanks, I didn't know the resistors numbering all started with a "R". How do determine the Ohm value? Is the numbering value R27 a .27 Ohm? What would a 1 Ohm say 1R? So now you have total of a .21 Ohm sense resistor?

    I'll have to see if the local Radio Shack carries them for a little upgrade.

    Thanks for the help! (sorry, been away from electronics since college)

  22. #22
    Flashaholic* VegasF6's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by Aircraft800 View Post
    What would a 1 Ohm say 1R? So now you have total of a .21 Ohm sense resistor?
    Wouldn't that just make too much sense (hah)
    I think it depends on the manufacturer some. Here is a chart from vishay.
    http://www.vishay.com/docs/20020/smdmark.pdf
    See, it depends on the tolerance, at least in there case.
    http://www.talkingelectronics.com/Ch...Resistors.html

  23. #23

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Hi Friends,

    I got theese boards from postal service and make some measurments. First batch of theese boards has PT4105 chip, now has PT4115 chip.

    MR16 1*3W Driver, using PT4115 chip. (Don't forget this design have rectifier diodes to work on AC/DC applications. Theese diodes eat efficiency a little)

    Results Drawn back until checked and confirmed again.

    Thanks,
    EpRoM

  24. #24
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Thanks again for these results eprom, but can you please test to lower voltages? Enquiring minds want to know just when it drops out of regulation, and how. Is it sudden or gradual?

    Does the efficiency improve running multiple LEDs? Have you seen any with the EQB8L chip?
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  25. #25

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    It starts regulation at 6.5V and 0,45A. Under 6.2V board does not work.

    I Will measure the performance for 4 LED setup.

    Quote Originally Posted by TorchBoy View Post
    Thanks again for these results eprom, but can you please test to lower voltages? Enquiring minds want to know just when it drops out of regulation, and how. Is it sudden or gradual?

    Does the efficiency improve running multiple LEDs? Have you seen any with the EQB8L chip?

  26. #26
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    No, a torch does not always mean flames.
    Ian.
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  27. #27
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    Str Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Quote Originally Posted by Aircraft800 View Post
    I thought you were talking about this one
    SKU 26110 18V 5W Cree Circuit Board for Flashlights (16.8mm*5.5mm) ?


    Which one is the R27 sense resistor? ^

    I thought it was the new Kennan replacement?
    I've burned 2 of those with 16v input . They are rated for 18v. It seems that the yellow capacitor that sits in between chip and inductor was turned in ash. Seems that both capacitors are identical, so I hope I could still make a working one from 2.
    Does anyone know the value of those? it saids on it S 160C
    Thanks

  28. #28

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Hi, Like I promise I complete the tests for 2*, 3*, 4* serial connected LED's driven by PT4115

    Results,

    Results Drawn back until checked and confirmed again.


  29. #29
    Flashaholic* TorchBoy's Avatar
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    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Here's a random thought. The spec sheet of the SS14 Schottky diode (which is used for rectifying in the EQB8L version of the DX SKU.13577 driver I have) has a Vf just over 0.4 V at 0.45 A. Two in the rectifier make 0.8 V, which at the peak efficiency an input current of 0.45 A will be 0.36 W, so 4.2% of the input power is being dissipated in the rectifier. 97.26% + 4.21 % = 101.47%. That's the sort of driver efficiency I like!

    But seriously, I have no idea what's going on there. Thanks heaps for those test results, eprom.
    No, a torch does not always mean flames.
    Ian.
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  30. #30

    Default Re: Newly Designed DX Buck Driver (Kennan Like) 90% Efficiency

    Hi TorchBoy,

    I am using a Laboratory DC Power Supply,



    Problem with this Supply is Amp. Meter has only two digits after dot and Volt Meter has only one digits after dot. So when I make a amp. measurment like 1.69A it could be 1.685A, 1.689A or 1.694A. And when I make a volt measurment like 4.0V it could be 3,95V~4,04V So it has a faulire rate on measurments. And it is effective on small measurments under 1A. But this is the best I can do. I dont have an amp. meter has an three digits after dot.

    I wish this would be acceptable.
    EpRoM


    Quote Originally Posted by TorchBoy View Post
    Here's a random thought. The spec sheet of the SS14 Schottky diode (which is used for rectifying in the EQB8L version of the DX SKU.13577 driver I have) has a Vf just over 0.4 V at 0.45 A. Two in the rectifier make 0.8 V, which at the peak efficiency an input current of 0.45 A will be 0.36 W, so 4.2% of the input power is being dissipated in the rectifier. 97.26% + 4.21 % = 101.47%. That's the sort of driver efficiency I like!

    But seriously, I have no idea what's going on there. Thanks heaps for those test results, eprom.

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