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5W RGBW CC driver

xanaduxanadu Posts: 3,206
I need to run two 5W RGBW LEDs in parallel. 700mA max per LED, so around 2A cont. per channel (LEDs in parallel) would suffice.

Is there a such thing as a CC driver in a TO-220 style through hole package with that kind of rating?

Comments

  • 19 Comments sorted by Date Added Votes
  • Will you be using an aluminum PCB?
  • jmgjmg Posts: 11,657
    xanadu wrote: »
    I need to run two 5W RGBW LEDs in parallel. 700mA max per LED, so around 2A cont. per channel (LEDs in parallel) would suffice.

    Is there a such thing as a CC driver in a TO-220 style through hole package with that kind of rating?

    Do you mean linear, or switch-mode ? Usually you current regulate per-led, so that's 8 x 700mA drivers

  • Will you be using an aluminum PCB?

    Yes, with an oversized heatsink and 20mm 12V fan per PCB.
    jmg wrote: »
    xanadu wrote: »
    I need to run two 5W RGBW LEDs in parallel. 700mA max per LED, so around 2A cont. per channel (LEDs in parallel) would suffice.

    Is there a such thing as a CC driver in a TO-220 style through hole package with that kind of rating?

    Do you mean linear, or switch-mode ? Usually you current regulate per-led, so that's 8 x 700mA drivers

    SMPS.
  • I have to replace this -

    aslol.JPG
    418 x 509 - 34K
  • Xanadu,

    Is that top wire actually connected because it doesn't as secure as the other two.
  • jmgjmg Posts: 11,657
    edited July 28 Vote Up0Vote Down
    xanadu wrote: »
    SMPS.
    That's not really enough info. What Vin, and how is the LED brightness controlled, over what range ?

    Do you expect a module, with inductors included.

    With many LEDs to drive, alternatives are to use a low cost solution per LED, or have one SMPS block, Voltage out, and then linear current regulation from there, with minimal voltage loss.
    eg compact (SOT25) feedback regulators (200mV ref) like AL5815/AL5816 can drive external TO220 (etc) power devices, (MOSFET or BIPOLAR) and PWM DIM

  • After giving it some thought I figured it wouldn't make sense to parallel 2 LEDs using CC... No more late night forum posts haha. Also sorry for the vagueness, there are reasons.

    Here's a diagram of the existing setup. I'm replacing everything, VIN, uC, LEDs, wiring, etc.

    masl.JPG
    Genetix wrote: »
    Xanadu,

    Is that top wire actually connected because it doesn't as secure as the other two.

    There's an electrical connection. I wouldn't be surprised if the heat shrink was the only thing holding it in place.
    jmg wrote: »
    xanadu wrote: »
    SMPS.
    That's not really enough info. What Vin, and how is the LED brightness controlled, over what range ?

    Do you expect a module, with inductors included.

    With many LEDs to drive, alternatives are to use a low cost solution per LED, or have one SMPS block, Voltage out, and then linear current regulation from there, with minimal voltage loss.
    eg compact (SOT25) feedback regulators (200mV ref) like AL5815/AL5816 can drive external TO220 (etc) power devices, (MOSFET or BIPOLAR) and PWM DIM

    The VIN can be 5V to 15V. I can do SMPS before the regulators. They appear to be controlled via PWM, over the full range of brightness. As for modules and there is very limited space available. I've seen a few that fit the requirements but wouldn't be able to squeeze 8 of them onboard.

    I ordered some new LEDs so I have some numbers to work with. They are dimmer but I can get the same brightness by modifying the diffusers they're using.

    Power: 4 Watt (Max)
    Emitting Color: RGBW (Red Green Blue White)
    Recommended Current: 300mA / Color
    Forward Voltage: R:2.0-2.4V G:3.0-3.4V B:3.0-3.4V W:3.0-3.4V

    On Sunday I'll test the brightness and then if it goes well source parts, or a custom PCB. I need 6 sets of controllers, 8 channels each, CC, 6-7V VIN, PWM controlled. It would be nice to have a low part count.

    If anyone is interested in fabricating the boards, PM me and we can talk on the phone.

    Thanks.
    571 x 472 - 31K
  • jmgjmg Posts: 11,657
    edited July 28 Vote Up0Vote Down
    xanadu wrote: »
    The VIN can be 5V to 15V. I can do SMPS before the regulators. They appear to be controlled via PWM, over the full range of brightness. As for modules and there is very limited space available. I've seen a few that fit the requirements but wouldn't be able to squeeze 8 of them onboard.

    I ordered some new LEDs so I have some numbers to work with. They are dimmer but I can get the same brightness by modifying the diffusers they're using.

    Power: 4 Watt (Max)
    Emitting Color: RGBW (Red Green Blue White)
    Recommended Current: 300mA / Color
    Forward Voltage: R:2.0-2.4V G:3.0-3.4V B:3.0-3.4V W:3.0-3.4V

    .. I need 6 sets of controllers, 8 channels each, CC, 6-7V VIN, PWM controlled. It would be nice to have a low part count.
    How long are the wires ? Can the LEDs be driven CA or CK, or do they come fixed as which one ?
    eg simple switching parts like AL8861, will prefer short connections (same PCB) and need access to both ends of each LED.
  • Short wires, 3-4". The LEDs are RGBW - 8 pin.

  • jmgjmg Posts: 11,657
    xanadu wrote: »
    Short wires, 3-4". The LEDs are RGBW - 8 pin.
    So not on the same PCB ?
    The AL179x series looks useful, but may be tight on your minimum VIN.
    That has a simple PG signal for LED dropout, and can drive up to 4 channels of common anode LEDs, PWM dim.

    What is the PWM frequency & control range ?
  • xanaduxanadu Posts: 3,206
    edited July 28 Vote Up0Vote Down
    The LEDs are on the same PCB, is that what you were asking?

    I'm not sure what the freq or range is on the existing equipment. I'm replacing it with a Propeller and my own code, so I'm flexible.





  • Example LED.

    Capture.JPG
    363 x 297 - 19K
  • jmgjmg Posts: 11,657
    edited July 29 Vote Up0Vote Down
    xanadu wrote: »
    They're not on the same PCB, and need the gap between them.

    I'm not sure what the freq or range is on the existing equipment. I'm replacing it with a Propeller and my own code, so I'm flexible.
    If you have a Prop there, that makes HW side simpler.. - you can use the Prop to adjust the SMPS pre-regulator to have just enough linear-drop.

    I'd suggest the KISS but efficient path, and use (eg) 4 x AL5816, plus any suitable decent NPN regulator transistor (not a FET) plus a LM339 quad comparator connected B-C on every LED's NPN.

    That LM339 is used to tell the Prop "VLED-too-low", and it ramps a shared SMPS UP - Join 2 for 2 channels.
    In operation the Prop+SMPS sits bouncing against that VLED lower limit, and that keeps the linear drop across the NPN to no less than ~0.7V
    SMPS-VLED is nominally 3.4V+0.2V sense drop + 0.7V Vce = 4.3V at 2.4A - any SMPS will do here.

    With a Prop, one alternative approach to VCE sense, would be to use a series R divider to the Logic threshold (~ 1.65V) from each LED cathode. (8 pins)
    An OR test on those shows if any are getting close to dropout.
    LM339 gives (0.7)*300m = 0.21W per linear transistor
    Simpler 3v3 Prop Threshold sense, gives (1.65-0.2)*300m = 0.435W per linear transistor. (+ more on RED, unless you add a series diode)

    Addit: a pair of dual BAT54A can analog 'or' the lowest-of-4 LED-K voltage, & may be simplest.
    No MCU needed, and that can feedback to the SMPS directly to set the Linear headroom.

    Low Sat NPN is used, good Hfe, perhaps NJT4031NT1G (SOT223), or ZXT690BK (DPAK) or NSS1C301ET4G or 2STD1665 etc - or if you want small, maybe PBSS4560PA,115 ? 3-HUSON (2x2) or Dual ? PHPT610030NKX

  • Thanks JMG this gives me a lot to run with. My new LEDs arrived yesterday.

    I went back and looked at the setup. They're using IRFZ44N to drive the LEDs.
  • tonyp12tonyp12 Posts: 1,914
    edited July 29 Vote Up0Vote Down
    So the plan is that the two LED's have its color output is unison?
    Put Red+Red in series at 9-12V, same with the other colors, as a 8pin led have separate cathode and anode I take it? (always include part number when asking in forum)

    use 4 of these: https://www.mouser.com/datasheet/2/115/AL8860-1019719.pdf

    Or a single 4channel led driver (but some only do global dimming):
    https://www.mouser.com/Semiconductors/Driver-ICs/LED-Lighting-Drivers/_/N-7zhqfZ1yzvvqx?P=1yzvta6Z1z0wbyxZ1z0vzanZ1z0wd8oZ1z0wbz3Z1z0wbyqZ1z0wd73Z1z0wadvZ1z0wc12&Ns=Pricing|0

    fancy: http://www.ti.com/lit/ds/symlink/lp8860-q1.pdf
    it only do 150mA/channel so use 5 weaker led in series, as this IC boost voltage.
    String-LED's share the current but each one do a voltage drop.

    or a 8 channel if not putting LED in series:
    https://www.mouser.com/Semiconductors/Driver-ICs/LED-Lighting-Drivers/_/N-7zhqf?P=1yzxao1Z1yx7o2fZ1yzt4toZ1z0w877Z1z0wd8oZ1z0w2kx&Ns=Pricing|0
  • jmgjmg Posts: 11,657
    edited July 29 Vote Up0Vote Down
    xanadu wrote: »
    Thanks JMG this gives me a lot to run with. My new LEDs arrived yesterday.

    I went back and looked at the setup. They're using IRFZ44N to drive the LEDs.

    That's a 17.5 mOhm MOSFET, tho the 17.5 mOhm matters little as it will be linear-mode operated.
    You just need a low enough Rds on to allow a low overhead, even 100mOhms, will be 30mV at 300mA

    With the analog-or option I added above, you do not need the NPN base voltage, so NPN stipulation drops & you can choose any package/part.

    A broad search helps these days, as often 'higher rated' parts are cheaper !

    eg if I filter 10mOhm to 100mOhm, these compact dual N-MOSFETs look good, if size matters to you. I choose a package that looks easy to cool, and tolerable to handle and solder...

    TSM200N03DPQ33 RGG 2 x 30mOhms at 4.5V, 3x3 package with flat-tabs, for good copper connect.
    AON7804 2 x 26mOhms at 4.5V - both ~ 18c/1k

    These would have a common SMPS pre-regulator, either one for every 4, if you expect future expansion, or one for every 8.
    These days, a SMPS that does not need an external schottky can be found.
    eg the ST ST1CC40 looks appealing - Sync rectifier and up to 3A, and can be used as either 100mV iSense LED SMPS, or you can divide ~4V DC to 100mV FB, for DC-pre-regulator use.
  • Thanks. Yes, the two LEDs need to have power output in unison. They all have separate cathode and anode. Here's link, there's a few pics, no datasheet. https://www.amazon.com/gp/product/B01DBZIXJ0/ref=oh_aui_detailpage_o00_s00

    Thanks for all of the suggestions.

  • I needed something to show today so I built a 4x4 array of SK6812 RGBW to mimic the 4W LED. It was easier than troubleshooting the existing mess. They liked the array so much I installed it. There's just enough room for it, a Prop mini, 5V@3A SMPS and 10 amp PTC. Problem solved.

    I didn't think it would be bright enough, but I found another layer of diffusion that could be removed. The person that made it was driving it too hard, then reducing the brightness with diffusion. I have the parts on order for the CC driver so I'm still going to make at least one. Maybe more, I have a pile of 4W RGBW LED.
  • tonyp12tonyp12 Posts: 1,914
    edited July 31 Vote Up0Vote Down
    As LED's pretty much have a linear cost-per-watt, I don't see why using two super powerfull LED's just to defuse them.
    Using a dozen smaller one gives you pre-defused light.


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