Results 1 to 5 of 5

Thread: Multiple Drivers on one diode?

  1. #1
    Join Date
    Jan 2018
    Posts
    2

    Default Multiple Drivers on one diode?

    My question stems from this video: https://www.youtube.com/watch?v=iVrJUbeuG44

    He states that he uses 24 drivers for his 8 5w blue diodes in the array. Does this mean that he is using 3 drivers for each diode? How does that work?

    Also it looks like he is using a simple convex lens to focus all the diodes or am I seeing it wrong?

    Thanks.

  2. #2
    Join Date
    Nov 2008
    Location
    Cleveland Ohio
    Posts
    2,599

    Default

    Those are not drivers. He used high power resistors to limit current. Not a good way to do it. Even using 317s would be better. He will experience e thermal run away at some point and toast the diodes. But given the video the level of smarts is pretty low. Wonder how his eyes are doing these days. Even the reflection is dangerous at those levels and in blue. Cataract city. If you are trying this....don’t.

    Now as for multiple drivers it’s a roll of the dice. If both devices share the load it might work but generally one of them will take more than the other and the load will be unbalanced. This can be solved with smart design and current limiting load balancing resistors but not the best way. If you need more current find a higher rated driver.

    It is possible in some designs to add more power devices with the load balancing resistors in a single driver. The regulation portion does not need to be repeated. It is the power handling section that requires more beef.

    First thing I’d do short of looking for new driver is beef up the traces on the driver with extra solder and try a higher power device in the active slot as well as increased heat sinking. Can’t give detail with out doing analysis but the traces on most boards can’t handle much more than 3-5 amps even beeefed up. You have to design heavier copper of do all high current off board which is way better.

    Just buy better driver.

  3. #3
    Join Date
    Oct 2012
    Location
    Germany
    Posts
    1,478

    Default

    ... I've heard in the video, that he's using 24x LM317 - but not clear, if as voltage drivers, or as current regulators.

    My older "simple-drivers" use either 5x LM317 or 5x LM338 in current regulating configuration and combined per jumpers in parallel for currents of up to 5Amps (with the LM317) or up to 15Amps (with the LM338)

    I can combine several of this drivers in parallel too, for higher currents ... but use then mostly my "smart-drivers" with OpAmp current regulating high power MOSFET's with currents of up to 20 or 40 Amps per driver.

    And yes -- he's more than crazy ... especially in his "role" as influencer of others

    Viktor

  4. #4
    Join Date
    Aug 2013
    Posts
    73

    Default

    Constant current drivers that operate on one side of the load* and share a common supply can be placed in parallel with no trouble. As long as they have separate feedback loops there should be no interaction. In fact this is exactly how you'd generally accomplish a high power constant current source if you can't fit your requirements into the SOA of a single transistor...you'd use an array of transistors with their own sense resistors and regulating loops, all controlled by a common setpoint. This arrangement does not require balancing resistors or anything, although you may want to trim the channels to match.

    * Meaning the pass transistor and sense resistor are on the same side of the load. Drivers that have the sense resistor on the low side and pass transistor on the high side, or vice-versa, would be problematic, but this isn't a terribly common arrangement. Drivers that have a positive step-down converter and low-side current source would be problematic as well unless the step down converters are designed to be paralleled.

  5. #5
    Join Date
    Jan 2018
    Posts
    2

    Default

    Thanks for the replies! Cleared up everything. Wealth of knowledge here.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •