How to Choose the Right Led Power Supply?
So you need some type of constant voltage power supply that can convert your AC household voltage down to a safe DC voltage. There are many things that factor into finding the right power supply for your needs. First, we should lock down the power we require from our power source.
Wattage of Led Power Supply
To get started, find out how many watts your light will consume. If you hope to run more than one light off of one power supply, you must sum the wattages up to find the total watts used. Make sure to have a large enough power supply by giving yourself a 20% cushion over the total wattage you calculate from your LEDs. This can easily be done by multiplying your total wattage by 1.2 and then finding a power supply rated for that wattage.
Say for example we have 4 runs of LED strips that run at about 12 watts each. Simply multiplying these will show that our system wattage should be right around 48 Watts. Now we can add the 20% recommended cushion on with 48 x 1.2 = 57.6 Watts. A 60-Watt (or higher) power supply will suffice for this project.
Voltage/Current Led Power Supply
When building an LED fixture or replacing a bad power supply, it is important to first verify that the output voltage is compatible with the LEDs voltage. LED products with built in current regulators will usually be pretty good about specifying what input voltage should be used. For instance, a 12V power supply would be used with our LED flex strips as that is what they require.
Another common application is using high power LEDs with constant current drivers that require a DC voltage input. Say we have six Cree LEDs running off of a Mean Well LDD-H driver. Each LED runs at about 3.1 volts. With four of these our total voltage in this series circuit would be 18.6VDC. Typically, low voltage drivers like the Mean Well LDD-H work better if you have a small cushion over the voltage they require. For this setup I would use a power supply outputting at least 24VDC. Note that you should always make sure the low voltage driver in use (Mean Well LDD-H in this case) is rated for the voltage you want to input. The Mean Well LDD-H can take 9-56VDC so we are all set in this situation. Find more about calculating your voltage within different circuits here.
Also, be sure to make sure the power supply you select can handle the input power you have. Line voltage will change depending where you are in the world. Make sure you know whether you have low-line AC power (90-120VAC) or high-line AC power (200-240VAC). A lot of power supplies, such as Mean Well products, will be rated for the full range but it is always helpful to know your AC input and make sure that the power supply you use is suited for this.