Tag: Constant Current

Exceeding Voltage Range on Constant Current Drivers

This is a subject I touched on in an earlier video  where I tried to run about 175 volts worth of LED (5 COBs) off of a driver only rated for 143 volts max. The result in that test was that the driver maintained its full voltage (~143v), but put out next to nothing for current. What I set out to test this time was what would happen if you were trying to pull just a handful of volts more than the driver was rated for, as opposed to trying to pull 30+ more than rated. By adding resistors in series with my 4 COB lights, I was able to slowly increase the voltage drop of my circuit to meet and exceed the max rating of my driver and see how it reacted.

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What Happens When Your Total Voltage Drop is Outside of Your Driver’s Constant Current Region?

In this video, we’ll have a look at what happens when the sum of your COB voltage drop in a circuit is below the minimum constant current region voltage of your driver, as well as what happens when it’s above the maximum constant current region voltage of your driver.

How COB LEDs Work on Constant Voltage and CC+CV Drivers

The Best Drivers for Single COB Systems

There’s a ton of information out there about finding drivers for your 4+ COB systems, but not a whole lot regarding drivers for setups with only 1 COB. The main problem is that most of the popular drivers for bigger systems have constant current ranges that are too high for a single COB, so they won’t work. We’ll need to find smaller drivers with similar characteristics in order to properly power your single COB grow light.

This post will examine a few different constant current drivers that will work for single COBs of different voltages. Note that these models are chosen with 120V AC power in mind, and may not work if your mains are 230V or whatever else. Always check the input voltage rating in the data sheet to be sure.

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COB LED Constant Current Driver Selection Tool


  1. Select a COB from the dropdown
  2. Enter the quantity of COBs
  3. Select a drive current.

The spreadsheet will calculate your total forward voltage and highlight all of the Mean Well HLG-C drivers that are compatible with the parameters you entered. All data is pulled from manufacturer product simulator tools. If the total forward voltage (Vf Total) of your system falls within the rated constant current range of a driver (between V_min and V_max), that driver will turn green, indicating it is a match. I welcome any and all feedback on how to improve this tool – if you notice an error, have a suggestion, or would like to see other COBs or drivers, leave a comment.

Please note that even though big drivers may be capable of driving tons of COBs in series at low current, the high voltage generated by wiring the COBs in series may exceed the rating of your COB holders or connectors (a number of common holders are rated for a maximum of 250V – this would equate to a max of about 7x 36V COBs in series per driver). Always check your equipment specs to verify it can handle the total voltage.

UPDATE 04/17/2017: Citizen CLU COBs updated to Version 6 (F1), Quantum Board 288 and 304 models added.

UPDATE 05/30/2017: HLG-480H-C Drivers added.

UPDATE 06/16/2017: 72V Cree CXB3590 added.

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Wiring Identical COBS in Parallel on a Constant Current Driver

I’m away from my plants tonight so I’ll have to update my grow tent progress tomorrow – here’s a little video I recorded instead!

Constant Current vs. Constant Voltage Drivers

When it comes to wiring LED COB circuits, series configurations with constant current drivers are generally the easiest way to go – especially if you’re new to electronics. Since LEDs are semi-conductors and operate a little differently than most basic circuits, it’s far easier to simply drive them at their rated current with a constant current driver than it is to try and produce that current by providing a constant voltage. If you check the datasheet and find that your LED COB has a typical forward voltage of 36V at 2400mA, you don’t want to strive to give the LED 36 volts, you want to strive to give it 2400mA at whatever voltage that current happens to occur at.

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