Adjusting Chinese 100W LED driver?

Discussion in 'General Electronics Chat' started by MikeA, Apr 25, 2014.

  1. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    Does anybody have experience with these LED drivers?

    This specific board seems to be the "standard" driver used in many millions of Chinese made LED light fixtures. I purchased a few of these drivers, and most seem to work just fine. That is they take in 100W on the AC, and convert it to around 3000ma @ 30v on the output.

    But some drivers that I have only take in 85W on the AC side, and put out about 2600-2700ma on the DC output. The LEDs connected to these drivers are visibly dimmer, especially when side by side with a driver that takes the full 100W. :mad:

    Any idea why this is happening? Just poor tolerances of the components on the board?:confused:
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    I think you've answered your own question.

    caveat emptor
     
  3. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    They did claim 3000ma +/- 5% on the spec sheet. So 2600ma is out of spec. :rolleyes:

    Does this look like a typical switching power supply? Think there is a single resistor somewhere that can be adjusted to "up" the current limiting circuit? :D
     
  4. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    On the back:

    (U3) STMicroelectronics M101AI Switching Controller
    (U1) STMicroelectronics L6562 TRANSITION-MODE PFC CONTROLLER
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    What's the Vf on your LEDs. Maybe it's LEDs and not driver problems.
     
  6. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    It's the standard 100W LED designed for these power supplies. Or these power supplies are designed for these 100W LEDs. The standard array of 10-series by 10-parallel. 30-32v forward @ 3000ma.
     
  7. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    Looks like R33 and R36 on the board are the shunt resistors, 0.043ohms each. Then a lead going down to the M101AI which measures voltage drop.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,791
    1,103
    Have you checked to see if all drivers have exactly the same board layout and component values? Perhaps there has been a board revision?
     
  9. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    It's possible, but they are all spec'ed 3000ma. So anything outside +/- 5% is out of spec. Just have to figure out what resistor to adjust. :D
     
  10. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    My guess is they just cut it to close. Your LEDs can be 32 to 34 volts, and while the spec on the regulator says 30 to 36 volts, the data sheet has a recommended maximum voltage of 32 volts. Even if they ran it at it's absolute maximum rating of 36 volts it doesn't leave much for current sense and such.
     
  11. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    M101AI might be up to 32v only, but it's not known if it's also doing voltage control. It's most definitely doing current control, using the R33 and R36 shunt resistors in parallel (0.043ohms each).

    I have one supply that takes 105W from the wall, and outputs exactly 100W through the LED. Ain't bad efficiency. :D
     
  12. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    So the resistors are 0.043% ohms each (R043), and since they are 3 digits, that means they are 5% tolerance. Right?

    And there's 2 of them in parallel, so it's a 0.0215 ohms together. If the supply is currently providing only 2600ma, then 2600ma across 0.0215 ohms would be 55.9mv voltage drop across the these resistors. Right so far?

    So if I want the M101AI to provide more current, I'll need so solder another resistor across the 2 already there, so the voltage drop decreases, and the M101AI compensates by sending more current to get the voltage drop it thinks is appropriate.

    How does this plan sound? :D
     
  13. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
  14. MikeA

    Thread Starter Member

    Jan 20, 2013
    125
    17
    I've tried connecting a big resistor parallel with the LED, and the total current remains the same while the LED dims and resistor gets hot. So it's def tuned to 2600ma. :rolleyes:

    Which R2 or R2 are referring to? The pictures of the circuit board or some schematic from the spec sheet?
     
  15. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    The spec sheet. You would have to find the ones for your board.
     
Loading...