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Dissapointed from a LED light bulb...

Discussion in 'General Electronics Chat' started by Externet, Dec 31, 2015.

  1. Externet

    Externet Member

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    Hi.
    Bought this 30Watt

    ----> http://www.aliexpress.com/item/1Pcs...b201644_4_79_78_77_82_80_62,searchweb201560_8

    with 102 leds, supposed to be for 85 to 265 VAC; gives less light than a 15Watt fluorescent CFL.
    Supposed to have cree brand leds, but they do not tell the type/model in order to measure/test if the bulb is correctly built/labeled/driven.

    Two equal circuits inside are each a 1.5uF/250V capacitor in series with a full wave rectifier to 4.7uF/400V electrolytic filter capacitor feeding series of 51 LEDs, no limiting resistor.

    1.5uF at 60 Hertz result in Zc = 1768 Ohms.

    A series of 51 white LEDs assumed at 3.3 Vf result in 168 Vf

    120V AC after the bridge rectifier and filter are supposed to yield 170V DC

    Measured Vf of one LED, shows 2.82V when bulb is lit;
    AC supply measured 120.4V;
    Capacitor drop measured 20.4V AC.
    20.4VAC in 1768 Ohms = 0.011 A
    So there is 100VAC / 141.4 V peak into 51 LEDs, resulting in 2.77Vf for each.

    Seems LEDs are underdriven.
    Do I raise the series capacitor to 2.0 uF for Zc = 1326 Ohm ? Or more ?

    Or, eliminate the mains bridge rectifier/capacitor/filter and connect the two sections of 51 series LEDs in counterparallel to mains ?

    Or, short circuit a few LEDs to raise Vf and If ?

    Or, could the bulb be mislabeled as for 120V and it is intended for 240V ?

    Or, what would you do ?


    Schematic----> http://s588.photobucket.com/user/Innernet/media/P1010590_zpsn1ztzgxb.jpg.html?sort=3&o=0
     
    Last edited: Jan 1, 2016
  2. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

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    I bought a R63 type for my kitchen.... Equivalent 55w.. Incredible!!! Lights up the whole kitchen on a tiny amount of power.... I guess some will be better than others..... I'll definitely replace them all with LED's when they blow..
     
  3. Externet

    Externet Member

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    R63 is only 9 Watts and pleases you... Same application here... kitchen, inside a glass globe that is not rated for higher heat than 50W incandescent, that is why I went LED, but something is wrong.
     
  4. dave

    Dave New Member

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  5. zahwi

    zahwi Member

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    Of course something is wrong. When the circuit is as you described it cannot be for 85-260V it can only be for one voltage. Only a switcher can do variable input.
    I guess what you have is for 220V.
     
  6. zahwi

    zahwi Member

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    Kitchens in England are much smaller than in US, 50W is enough.
     
  7. AnalogKid

    AnalogKid Well-Known Member

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    Making some light and making the rated light are two different things. With no regulation acoss an almost 3:1 input range, the only way to get rated light is at high line.

    ak
     
  8. ronv

    ronv Well-Known Member Most Helpful Member

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    Looks like you have a 220 volt one. It looks like they are Cree 5050 LEDs.
    You could parallel 2 1.5ufd and check that.
     
  9. Externet

    Externet Member

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    Thanks.
    If I knew the Cree 5050 part number, I could check specifications to put them on a ~85% of rated duty. Unsure if these LEDs should run at 20mA or 30mA, at what Vf.

    Perhaps the chinese vendor should specify "30W maximum at 240 V" instead of just 30W. But we know where chinese goof/mislead almost always... I will raise capacity and measure in steps.
    Still do not know the habit of designing these with full wave rectifiers... Perhaps to diminish flickering ?
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Just to confirm, LED lighting is great - I've replace ALL my home lighting (indoors and out) with LED bulbs and tubes - about half the price of CCFL to run, comes on instantly, and has a nice white light.

    A 10W LED bulb is considerably brighter than a 60W incandescent one, or a 20W CCFL.
     
  11. ronv

    ronv Well-Known Member Most Helpful Member

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    This one I think.
    http://www.cree.com/~/media/Files/Cree/Chips-and-Material/Data-Sheets-Chips/CPR3ER.pdf
     
  12. chemelec

    chemelec Well-Known Member

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    It Appears to me that with the 2 caps in series, it is wired for 220 VAC.
    For 110 VAC, I would try Shorting out one of those Capacitors and see if your brightness is than up-to-par.

    PLEASE Let me Know as if they do work good this way.
    And I Might get some of these LED Lights.
     
  13. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Looking at the circuit at 120Vac and with the measured 20V across the 1.5uF cap I can't see how much current flows in the LEDs.
    At 220Vac I do get current.
    I am using 100V+68V Zener diodes for the LEDs. Blue trace is the voltage across 4.7uF.
    Green is LED current.
    The 4.7uF is too small to do its job. If C=470uf current is 50mA dc.
    upload_2016-1-1_10-3-56.png
     
  14. chemelec

    chemelec Well-Known Member

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    Or did I Misunderstand you?
    Are their Two of these Circuits, One Operating the Bottom Round Disk and the Other operating the Side Lights?
     
  15. ronv

    ronv Well-Known Member Most Helpful Member

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    Ron,
    You can use 1 LED - I used an A---- something that had about the right voltage drop. Then right click on the part number and add N=51 after it. Then Spice will treat it like 51 in series. That way you see the effect of lower Vf with lower current.
     
    • Informative Informative x 1
  16. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Because there is very little voltage across the 1.5uF cap, changing it value will have no/little effect.
     
  17. Externet

    Externet Member

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    Nigel :
    I have the 9W bulbs everywhere in my house, at <$2 each ! and are satisfactory:
    ----> http://www.lowes.com/pd_740058-43921-YGA03A41-A19-9W-830_1z10ht5__?productId=50423208&pl=1

    ronv : your data sheet linked does not correspond to the emitter. A closer guess is :
    ----> http://www.leds-buy.nl/datasheets/clp6b-wkw.pdf

    Chemelec : My plan at this point is to eliminate the 'driving circuitry' pictured at :
    Schematic----> http://s588.photobucket.com/user/Innernet/media/P1010590_zpsn1ztzgxb.jpg.html?sort=3&o=0
    and put both 'halves' in counterparallel directly into 120VAC mains. It is risky, but perhaps only one LED in the chain will vaporize and leave the others healthy if rating is exceeded. Will let know the color of the smoke...
    The two series of 51 LEDs are not segregated to round cap/sides, they are shared everywhere.

    ronsimpson : Thank you for the effort on your post/simulation. I believe you meant the 1.5uF/250V is too small to do its job. The 4.7uF shows reasonable smoothing on your simulation. Is it ?
     
    Last edited: Jan 1, 2016
  18. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    upload_2016-1-1_10-53-25.png
    Now I have the 20Vac across 1.5uF.
     
  19. ronv

    ronv Well-Known Member Most Helpful Member

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    Danger Will Robertson!
    Let Ron or I redo the simulation first. I didn't save mine.
    Ahh, there is Ron.
    Okay now try 3 Ufd.
     
  20. ronv

    ronv Well-Known Member Most Helpful Member

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    Well, I don't know what I did yesterday - but it was wrong. :banghead:
    I should have know that I guess. Typical white LED drop is around 3.3 volts X 51 is 168 volts - about the same as the peak line voltage. The trouble with just hooking them up is that as they heat the Vf goes down and they want to run away.
     
  21. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    ronv
    Here is the LT Spice file I use.
    rons

    ---edit---
    I think the HV capacitor should have 1/2 the line voltage across it. (not 20V)
    Are we sure the LEDs are 2x25 not 1x51 (25 parallel 25)?
     

    Attached Files:

    Last edited: Jan 1, 2016

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