High CRI LED Light Bar - Design

Hello BLF! I have had a project stirring in my mind for a while now, and I want to get serious about designing it. Like several others, I have been frustrated by the LED light bar market, which seems to be made up only of cheaply produced, inefficient, poor quality chinese mystery LED bars, or better quality but very very expensive LED bars. And on both sides, I can’t find any information on what kind of LEDs they are using. They all seem to be very cool white with low CRI. So I want to build my own light bar that hopefully hits the right balance of good color, tint, efficiency, and brightness.

I have read a few of the other light bar build threads on here, and I will be borrowing a lot of ideas from those as far as the design of the bar itself and the heatsink. But I want to design my own driver as well. Admittedly, part of my motivation is to just learn more about circuits and power electronics, and I can’t help but believe that I can build a much more efficient bespoke driver for this one task, rather than just using an off the shelf cc/cv board. I am currently at University for Electrical Engineering, so I have access to quite a bit of equipment for testing and design and want to take advantage of it while I can.

Right now I am thinking of doing a bank of around 15 or so Nichia 519A LEDs, across maybe an 18in light bar (maybe larger if I find I can dissipate the heat properly). The question I am having right now is if I should design the driver to drop the voltage to around 3V and drive all the LEDs in parallel, or if I should have 5 banks in parallel, with 3 LEDs in each bank. That way, the Vf for each branch is around 12V, and the driver doesn’t have to do as much work. Or, is it easier to just choose larger 12V LEDs, like the XHP 70? I know either way I am going to have to regulate the current, I am just trying to figure out which voltage set up will be easier to design for.

As for current control, I have read some things saying that PWM is the most efficient way to do that. I am anticipating having a microcontroller (probably just an Arduino for now, I have an extra one laying around) doing PWM on the gate of a MOSFET (or a few) to regulate the current. However, if there is a reliable way to do this with only analog components, I would be interested in that too.

Maybe I am biting off more than I can chew, but I am wrapping up a circuits class right now, and it’s got me all excited to build my own circuits. There is a lot of information out there about the LEDs themselves, but not nearly as much about drivers, and even what is there tends to be very general. I am hoping to get some feedback on if I am in the right ballpark on how to do this, or if anybody else has any better ideas. I am really just looking to learn.

Thank you.

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Yes, wire the LEDs in series groups of three. The driver is more efficient, the less the voltage drop from supply to load.
If you look at offroad lights, most have LEDs in multiples of three.
You can use PWM for dimming, but for current regulation in an automotive application, you want a buck driver.
This is an easy to use buck driver: https://www.st.com/en/power-management/led2001.html
And they have an online design tool: https://www.st.com/content/st_com/en/support/resources/edesign.html

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I am of no help here ,but wanted to comment because I had been gifted a beautiful ( large) bar that had me even remotely consider building a light bar.
After doing some quick math just for emitters I threw out the idea of ever even entertaining such a project.
I do like the thought of the nichias as one way of keeping emitter costs down .I thought about running cheaper leds every other emitter to make it look more uniform…but have the real ones doing all the heavy lifting.
I have no need or desire for a light bar ,but I do have a beautiful bar ,nice wiring and access to nice diffusion . I just can’t make sense of the numbers and can see why there are so many smaller junk light bars on the market.

See… I really had nothing to offer :slight_smile:)

Thank you! This is exactly the kind of information I was looking for.