Multiple LED driver with different power ratings - Page 1
Forum section: electronics / projects

author: WaldPinkler
author_rank: Contributor
timestamp: December 08, 2022, 06:04:33 am
content: I'm wanting to make over engineered lights for my yacht. I'm wondering on the best approach to drive 3 different LEDs.A warm light, white light and a red light for night sailing. I already have the heatsinks which can easily fit 3 COB LEDs.It's 12V driving 37V 300mA for the main ones. The red one is much lower power.How do I go about adapting a boost controller to drive 3 the different lights?Some thoughts I had...- Mosfets to switch to different loads.- Multi channel power ic - costs much more though.- I could just over drive the lower power LEDs but PWM dim them. I don't know how acceptable that is.I will add a simple MCU for dimming and for switching to night mode. Not sure on how to communicate that from a central location, I guess UART is fine.My first version is done and working. Just a simple driver for one LED with a 555 timer for PWM dimming. Time for the next. I'm enjoying the process.Thanks for any advice or pointing me in the right direction.

author: Faranight
author_rank: Unknown
timestamp: December 08, 2022, 05:24:26 pm
content: Hello. I've been doing some LED lighting stuff myself recently, so, perhaps I can share a few thoughts.What kind of LED drivers are you planning to use? Because LED's are generally current-driven (constant current) devices rather than voltage-driven (constant-voltage). With a constant-voltage driver you could probably get away by adding an appropriate series resistor to the LED's. So, with a lower power LED you could use the same driver and add a bigger series resistor to dissipate some power and lower the LED's voltage to tolerable levels. This approach would be less energy-efficient though. Using a constant-current driver along with series resistors or additional PWM driver would not be a good idea.You could use three separate boost drivers (one for each LED color), but this would be more costly as you have already figured out. Maybe check on ebay?If you're looking for a DIY-solution then PWM is also an option. But I'm unsure how big of a problem this would be on a ship... PWM tends to cause lots of EMI. I've been dealing with some EMI-related things myself as of late.

author: ajb
author_rank: Super Contributor
timestamp: December 08, 2022, 07:41:07 pm
content: So the red module is lower power, but is it lower voltage, lower current, or both? And you're trying to use a single driver for all three?If all three LEDs have the same current rating (or at least all have a current rating above what you need) then you could use a single constant current driver and then switch which LEDs are connected to it. You'd ideally want to turn the driver off before switch loads, though.You could probably overdrive the red module and PWM, provided you're not going crazy overboard. Does the datasheet give a peak current rating? Some LED drivers allow the output current to be externally programmed, so that could be an option as well.Using three separate drivers would bring some nice feature advantages, like the ability to crossfade from one color to another rather than just making a hard cut. You could even sort of do a tunable color temp white--only 'sort of' in this case because you won't be able to mix the output of two separate COBs very well.

author: John B
author_rank: Frequent Contributor
timestamp: December 08, 2022, 08:34:28 pm
content: You can buy off the shelf DC/DC step up CC LED drivers which have PWM and/or analogue dimming inputs. These would probably be best as they are sealed and potted which would be a good idea in a salty environment.Here's a typical example - may not be exactly what you need though:https://www.farnell.com/datasheets/2864649.pdfThen you only have to DIY the PWM signal interface, which could all be achieved with a single microcontroller.

author: WaldPinkler
author_rank: Contributor
timestamp: December 08, 2022, 08:54:31 pm
content: The main white LEDs are 300mA at 37V. I've found some aliexpress red ones DC 15-17V(5W) / 240-300mA. So maybe a single driver can work. I'll try play around with an arduino and switch loads with my driver.I'm not getting any interference issues with the current driver and PWM. It's at 500kHz. I can't remember what I set the 555 adjustable timer at. Something much less.I mostly have to watch out for marine frequencies of ~150-160Mhz.I like that cross fading idea but I'll try and limit the features for now!There shouldn't be too much salt to worry about. I mean all the other non sealed devices run fine (solar controllers, inverter, laptop, radios).

author: WaldPinkler
author_rank: Contributor
timestamp: December 08, 2022, 08:55:21 pm
content: I didn't consider having to turn off the LED driver when switching loads. What issues could there be?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 09, 2022, 06:46:21 am
content: You need to control the led currentAnd at 37volts are you playing with 100watts led by the way ??Just use an dimmable led driver .... you have ones with a dial, some with remotesome like thishttps://www.amazon.ca/Dimmable-Switches-Channel-Constant-Controller/dp/B075NZPTSQhttps://omnify.lighting/home-2-2/led-lighting-accessories/dimming-options/rgbw-dimmable-driver/