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  1. #1
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    Default Compatability of Constant Current LED Drivers to LED's

    Hi Guys,
    Is there anyone who is knowledgable on this matter?

    I have a Pierlite Gen 3 LED batten that the Constant Current LED driver has failed.
    Driver is rated for 40W, 58-114V DC Output and max output current is 350mA.

    Does a replacement have to be selectable to limit current to 350mA and if higher, will damage the LEDS ?

    Does the output voltage need to as high as that in order to drive the LEDS?

    I don't want to order a possible replacement and find it blows the LED or doesn't output a high enough voltage to drive the current needed......

    The same driver does not appear to be available. Very scant info on it although a found a data sheet.

    Thanks

    Steve


    https://photos.app.goo.gl/vgqobRUcqAWTDrnn7

    https://photos.app.goo.gl/7y6JB72UoXoqwSMG6

    https://photos.app.goo.gl/YwZmPsorxZGGYd1u9

  2. #2
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    Default

    Quote Originally Posted by Sterob View Post
    ....
    Does a replacement have to be selectable to limit current to 350mA and if higher, will damage the LEDS ?

    Does the output voltage need to as high as that in order to drive the LEDS?

    ....
    I will not claim to be an expert but have tinkered a little with low voltage LEDS
    A LED is basically a diode that emits light when a current flows in the forward direction -- white LEDs (actually a blue LED with a phosphor to emit other wavelength to look white) have a forward voltage drop of about 3V per junction. Like a diode there is limited increase in the voltage drop with increase current so the power supply must limit the current. So if the LEDs are rated at 350mA then exceeding this will be detrimental to the life of the LED (more power Voltage drop over the LED x current through the LED) overheats the LED and cooks it. Less current is OK, but there will be less light.

    Given each junction has a 3 volt drop, manufacturers of mains lights put multiple LEDs in series to reduce losses in the power supply. The 58 to 114VDC says there are between 20 and 30 LED junctions in series. If a power supply of less voltage is applied then the LED will not be forward biased sufficiently to allow it to carry its rated current. I have seen some LEDS in the string light and others not. If, as is likely, there are multiple strings in parallel, then due to variation in the LEDs, one string will carry what current flows, and in it only some LEDs will dimly light. So a low voltage is not going to produce the desired result.

    The reason for the range 58 to 114 is that the output voltage rises and falls a little as the power supply regulates its 350mA current through the LEDs in series. The power supply must have enough voltage to deliver the current needed to the string of LEDs.

    https://www.maximintegrated.com/en/d...es/3/3070.html is a page describing LEDs.. low current ones, but the principles are the same. Figure 7 shows the relationship between current and voltage.
    cheers
    David

    ------------------------------------------------
    A society grows great when old men plant trees whose shade they’ll never sit in. (Greek proverb)

  3. #3
    Join Date
    Sep 2012
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    Default

    Hi Steven, Guys,

    David is spot on ! You need to source a driver with the same specifications. You may find that its cheaper to simply replace the whole light batton.

    I recall mentioning earlier that there are some very clever LED driver chips about.
    Best Regards:
    Baron J.

  4. #4
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    Default

    Thank you gentlemen,
    So in summary, The replacement driver needs to have a high enough output voltage to drive the leds, at their rated current? ie 350 mA.


    Steve

  5. #5
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Steven, Guys,
    You may find that its cheaper to simply replace the whole light batton.
    I know what you mean. Would like to fix it if I can. I have 15 of these light fittings. If I can find a good cheap replacement for these drivers, I'll be able to keep then going, IF its only the drivers that keep failing......

  6. #6
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    Default

    Good Morning Steve,

    Fundamentally the driver is simply a variable voltage power supply that is current limited, essentially a resistor in series with a voltage and the LED string. The LED's are designed to fail short circuit, which is why you get one or more LED's not lit up whilst the rest are.

    A common topography is a switch mode power supply feeding a controller chip and series pass device, the chip measuring the current and regulating the voltage accordingly. It is quite uncommon for these devices to fail ! You might find that if you disconnect the output and measure the voltage, there will either be full voltage or non at all.

    If there is no voltage or a very low voltage then the driver has failed, measuring a normal voltage suggests that the tube has failed. The problem of course is that the tube can go open circuit as well as just individual LED dieing. It may also be that there is a thermal fuse in the tube that is designed to remove power from the tube. Measuring the output voltage with everything connected doesn't tell you very much. Substitution is one way of checking but risks damage to the substituted components.

    Hope this helps !
    Best Regards:
    Baron J.

  7. #7
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    Default

    Ive orderd two different power supplies to try.
    Will report back when I've done some tests.

    Steve

  8. #8
    Join Date
    Dec 2007
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    Adelaide
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    Default

    LED's might have a life of 50000 hrs but does that extend to the drivers ?


    I fitted a full complement of LED style fluro tubes in my workshop after 5 yrs 4 have failed out of 12 in total - I first off tried to replace the drivers with a generic driver but found the light output much reduced, I also tried to replace all of the passive components (capacitors) on the failed driver board and had no luck. I gave up and decided that rather than keep putting $ into the failed drivers I would just replace the complete tube - part of my problem might be that I'm close to a distribution transformer and my mains voltage hovers around 245-247V - most led drivers specs state input voltage 110-220V. I plan - one day - to install a 240 - 220V isolating transformer that I salvaged from a large CRT type colour TV some years back.

  9. #9
    BobL is offline Member: Blue and white apron brigade
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    Default

    I installed 20 LED fluoro replacements (15 in the shed and 5 elsewhere) 6.5 years ago and one has died in that time.

  10. #10
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    Default

    I replaced all the down lights in my house (probably about 50 - they were everywhere) with Osram LED fixtures about 7 years ago. They were expensive but none have failed yet.

    A shonky builder put 12 wall lights on a building for me 2 years ago and all have failed - some blink, some are dim, some are just dead.

    I installed three cheap Chinese LED floodlights about three years ago and 2 have failed. They are on all night.

    I pulled a few of the defective lights apart and checked them out. Interestingly, the power supplies tested as functional, but a lot of the LED elements were not.

    My take on this is, like anything else, you get what you pay for. The 50,000 hour life quoted on cheap LED fixtures is not what they got by exhaustive testing, but from a quick look at the Cree/Philips/Osram specs...

    Leigh


    Sent from my iPad using Tapatalk

  11. #11
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    Quote Originally Posted by Ambrosia View Post
    I replaced all the down lights in my house (probably about 50 - they were everywhere) with Osram LED fixtures about 7 years ago. They were expensive but none have failed yet.

    A shonky builder put 12 wall lights on a building for me 2 years ago and all have failed - some blink, some are dim, some are just dead.

    I installed three cheap Chinese LED floodlights about three years ago and 2 have failed. They are on all night.

    I pulled a few of the defective lights apart and checked them out. Interestingly, the power supplies tested as functional, but a lot of the LED elements were not.

    My take on this is, like anything else, you get what you pay for. The 50,000 hour life quoted on cheap LED fixtures is not what they got by exhaustive testing, but from a quick look at the Cree/Philips/Osram specs...

    Leigh
    Hi Leigh, Guys,

    Your post basically confirms my findings, that the power supplies (drivers) rarely fail and its the tubes that go bad !

    What seems to happen is the odd LED fails, then another and so on until either the current becomes too high and the voltage falls to a lower limit switching the power supply off, or a thermal fuse in the tube goes open and disconnects the tube.

    It seems that the cost of good LED tubes are quite expensive about half the cost of a new baton. Some of the electrical wholesalers do keep generic replacement power supplies/driver bricks for some fittings. Most don't preferring to sell a complete light fitting.
    Best Regards:
    Baron J.

  12. #12
    BobL is offline Member: Blue and white apron brigade
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    Default

    The 50,000 hours quoted for LEDs are not the actual expected lifetimes but "mean time to failure".

    Hence for any given set of LEDs, on average some might run for less 50,000 hours while other may last for longer.

    One thing they don't tell you is that LEDs do lose brightness over time (as do regular fluoros). I noticed that when I replaced the one that stopped working and the new one right alongside a used one is considerably brighter.

  13. #13
    Join Date
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    Default

    My battens are of a reputable brand ( I hope ) and cost me about $80 each , from a reputable Electrical business,so I HOPE this failure is a rare one.
    My intension was to buy good, and buy once.
    We will see if I have messed up or not....lol

    Steve

  14. #14
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    Default

    I found the OEM Led Driver for $18 and bought 2.
    Batten is working again, so all good.

    It just goes to show the mark up on these things. If the led driver is $18 retail, how much do they cost to make? $8?
    Would be surprised if the whole thing costs $30 to make.

    Steve

  15. #15
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    Quote Originally Posted by Sterob View Post
    I found the OEM Led Driver for $18 and bought 2.
    Batten is working again, so all good.

    It just goes to show the mark up on these things. If the led driver is $18 retail, how much do they cost to make? $8?
    Would be surprised if the whole thing costs $30 to make.

    Steve
    Hi Steve,

    I'm glad that you found suitable ones ! As far as cost to make, I doubt more than a couple of dollars. The retailer will double the price he paid and the distributor will do the same, so the manufacturer would be looking at half that.

    I used to be able to buy 240v to 12 volt 50 watt PSU for low voltage halogen lighting, very cheaply, now they are like rocking horse poo !
    Best Regards:
    Baron J.

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