Why Some Constant Voltage Drivers Have 2 Sets of Output Leads

If you’ve looked at some of Mean Well’s larger HLG series constant voltage drivers, you may have noticed that some of the big boys have 2 sets of outputs leads (2 positive and 2 negative output wires), rather than 1. This can be a little confusing for newcomers, since the majority of the HLG series drivers only have a single set. Why would the big CV units have two?

Well, what do each of these drivers have in common? They all have very high output current levels. 

For example, the entire lineup of the HLG-600H series driver features dual outputs, all the way from the HLG-600H-12 (rated for a whopping 40 amps of current) through to the HLG-600H-54 (rated for 11.2 amps). Moving down to the HLG-480H driver, only the 24V, 30V, 36V, and 42V models have dual outputs. The 48V and 54V versions of the 480H don’t have dual outputs because they produce less current than their lower-voltage counterparts, and the double outputs are not required. This also goes for every single constant current version of the HLG series. All the HLG-C drivers produce a relatively low current, but with a higher voltage. Since the current is low, they do not require multiple outputs.

On a driver with 2 sets of outputs, the current is not somehow split up between the 2 sets inside the driver. If, for example, your driver was rated to output 20 amps of current, the 2 sets do not provide 10 amps each. They are simply internally paralleled within the driver. This means that you could get the full 20 amps from either one of the outputs by itself; it’s just not a great idea.

Having too much current on your wires is a bad thing. If your wire is too small (the higher the gauge number, the smaller the diameter of the wire: a 12 gauge wire is much larger than a 20 gauge wire), and you run too much current through it, the wire will overheat. This can melt the wire and  it presents a big fire risk. So, what are your options when you’re faced with having a lot of current on your run? You can do a couple things:

• You can increase the size of your wire. A thicker wire can handle more current. There are many handy charts available online like this one that can help you determine how much current each gauge of wire can handle. This works well for wiring backbone runs between wagos, but you usually can’t fit anything thicker than 18 gauge solid core wire into a COB, board, or strip connector.
• You can split the current by using multiple runs of wire. This is exactly what these dual-output drivers are allowing you to do.

Let’s say you have 4 Quantum Boards connected in parallel and they’re drawing 12 amps from your HLG-600H-54 driver. If you were to only utilize one of the output leads, you would have all 12 amps flowing through this single set of leads. Here’s what it would look like:

However, if you split your boards up and put half on one output lead, and half on the other output lead, then you’ve now reduced the current on each wire run to 6 amps, as shown below:

Now, granted, in the first image, the only wire that would be carrying the full 12A of current would be the driver lead itself, and I would imagine that Mean Well has engineered these leads to be beefy enough that they could support the full current of the driver, but I can’t say for sure whether or not they can, and it’s better to play it safe. Using only one of the two outputs becomes especially problematic in builds where the driver lead is being extended out to a Wago further down the line which then distributes wiring out to the strips. If you don’t have a big enough wire for this initial driver extension run, and have only a single wire to carry the current, you can end up with way too much amperage on the wire. This scenario would look something like the image below. As you can see, the full 12A is being placed across the extension wire, and this is no good if you’re using small wire:

In summary, if you have 2 sets of output leads, they’re there for a reason. Split your current draw up as evenly as possible and use both sets!