Low-Cost Method for Wiring Multiple Constant Current LED Luminaires

1 December 2020

If you are wiring multiple constant current luminaires MEAN WELL has a low-cost solution. 

Instead of using a separate 240VAC to constant current DC LED driver for each luminaire you could use a low cost DC to DC constant current LED driver on each lamp, and power the DC to DC drivers from a single constant voltage LED driver instead. This will substantially reduce the cost of the hardware.  

Example of Low-Cost Method for Wiring Multiple Constant Current LED Luminaires 

Let’s presume you wish to wire 10 x LED luminaires.  

Each requires a 350mA LED driver with a 15-28VDC forward voltage range.  

Your initial approach may be to source 10 x 350mA LED drivers with a power output of around 10-15 Watts.  

However, instead you could use 1 x LDD-350HW per luminaire. These have an output of 350mA with a forward voltage of 2-52VDC. 

Ideally you should use a LED driver with the exact current required to power the LEDs. You can go a little lower if needed, but don’t go higher. You may overdrive the LEDs and cause them to burn out. Please note of you do use a lower current LED driver, the luminaires may not be quite a bright as expected.  

The LED driver you select must have a forward voltage range that can accommodate the range required by the LED luminaires. In this example our luminaires require 15-28VDC, so the 2-52VDC forward range of the LDD-350HWs is more than adequate. The LDDs need an input voltage 3V higher than the output to make them work. So, for 28V LEDs, a 36V input is a good choice. All that is required now is a constant voltage LED driver to take the 240VAC and convert it to DC to power the 10 x DC to DC LED drivers. 

To calculate the size of constant voltage LED driver required, you first work out the maximum power each could draw. This is done by multiplying the output current by the top of the forward voltage range. So, in our example above this would be 350mA (0.35A) x 28V = 9.8W. You then multiply this maximum power rating x the number of luminaires: 9.8W x 10 = 98W. Then add another few Watts for headroom.  

We need a constant voltage LED driver with at least 100W output. In this case you would use a 150-Watt LED driver, such as the ELG-150-36A-AUP. The ‘-AUP’ suffix denotes that the LED driver has an Australian flex and plug fitted, which makes installation a lot easier and far more cost effective.  

One thing to watch out for is the minimum operating voltage of the driver supplying the input voltage. A 36V driver will operate down to 18V before it senses an overload and starts to “hiccup”. This limits the minimum usable voltage with this technique. If your LEDs run at 10V, the power supply will try to provide power at (10+3) Volts and will sense an overload and start to “hiccup”  

The below wiring diagram shows how an ELG-150-36-AUP and 10 LDD-350HWs should be installed: 

Low cost method for wiring multiple constant current LED luminaires

In this example, your hardware cost would be approximately 50% cheaper if you had used the single ELG-150-36-AUP to power 10x LDD-350HWs instead of buying 10 x 350mA 240VAC constant current LED drivers.  

If you have any questions about this installation method, please do not hesitate to contact MEAN WELL Australia.