LED technology is a completely different lighting method than other conventional lighting types. For one, LED's require an LED driver to control the electrical current. They often look similar to a fluorescent ballast but come in all shapes and sizes. Some are even hidden within what you might consider to be the "bulb", such as an A19 or T8 LED.
Ins & Outs of LED Drivers
Although LED lighting has many great benefits -- including energy efficiency, long life, and environmental friendliness -- one of its potential disadvantages is that LEDs require a flow of consistent and constant electrical current at all times, at the exact voltage it requires. Doing this allows the LEDs to stay a consistent temperature. If an LED runs too hot, it may begin to malfunction and experience poor performance.
To help keep LEDs running in top form is where an LED driver comes in.
What is an LED Driver?
An LED driver is a device that does exactly what it sounds like -- it drives the power to one or more LEDs.
As we mentioned previously, a good thing about LEDs is that they are energy efficient -- they do not require a large amount of power to get them going. LEDs actually work on DC power at a rather low voltage -- usually between 2V to 4V. Because of that, they require something that will convert AC into DC for them, and also will help keep them protected from any power surges that might occur, causing the LEDs to become overheated and become problematic.
The LED driver acts not only as an electrical current management system, but also as a protective buffer. It's like Baby Bear in the Goldilocks tale -- everything is just right.
As you look at the variety of LED driver products out there today, you'll notice there are two distinct types -- constant voltage and constant current. Both versions are for different things in different situations. It's important to read the product specifications of your LED lamp to make sure you are using the correct type. They are not usable interchangeably.
Constant Voltage LED Driver
A constant voltage driver is used for LED products that require a steady and constant DC voltage to keep it performing well. Many times a constant voltage will be used with an LED lamp or other product that has a built-in driver for the current already installed. All it really needs is something to keep the voltage consistent. It is also mainly for applications where the LEDs are in a strip configuration and are all in a parallel connection to the driver. It ensures that every LED receives the same amount of voltage from the driver.
LEDs often use constant voltage drivers for illuminating landscape and accent lighting, back-lighting for advertising signs, and huge high-definition LED displays. Usually they are available in a number of different wattages, and can also come with dimming capabilities.
Constant Current LED Driver
Rather than regulating the voltage, a constant current LED driver manages the actual current that comes in to the LED's diode that is required to get things jumping in the p-n junction. Additionally, this type of driver helps regulate the amount of forward current that can occur between the LEDs. This is a result of photon creation when the LED is on. Too much of this forward current can potentially overheat the LED, causing it to malfunction.
A constant current driver is primarily for situations where an LED lamp does not already have a current driver built in. It keeps a consistent current running through a string or series of LEDs. Constant current drivers are available in a variety of different configurations.
A key piece of understanding how LED drivers work is knowing the different LED configurations. The two most common LED configurations are series and parallel.
In a series configuration, one LED's anode (aka positively charged electrode) is connected to another's cathode (aka negatively charged electrode). This enables a single, non-stop current to flow through all the LEDs in the series, usually called a string.
Important to note that in order to keep the entire string of LEDs running, you have to make sure you're providing enough voltage for the sum of them all. So, for instance, if each LED needs 2V to illuminate and you have 10 LEDs, they will require 20V.
Another standard configuration for LEDs is a parallel configuration. Here we would connect multiple strings of LEDs in parallel -- or side-by-side -- to a driver. So, for instance, if you had 50 LEDs you could have five strings of 10 LEDs each running parallel, rather than all 50 in one string. A parallel configuration is for situations where you want to limit the voltage necessary to operate the strings of LEDs.
You can also configure parallel strings of LEDs in a matrix. This happens when sets of parallel strings of LEDs connect to each other in a series.
Dimming & Color Sequencing
Depending on their specifications, some LED drivers can also facilitate dimming and/or color sequencing.
Depending on the type of LED driver you select, their dimming skill can cover the full range. The driver dims the LEDs by either shortening the amount of leading current going through it, or by a method called pulse width modulation (PWM). Most drivers that offer dimming use PWM. This allows dimming without flickering and with usually very little color change in the LEDs.
It is good to note that dimming does not affect an LED's competence. It also will not have a negative impact on how long it lasts. In fact, dimming can potentially help LEDs last longer as it will reduce the heat it creates when lit.
With color sequencing or changing, many times an LED string or product may have LEDs of different colors. In fact, many times a "white" colored LED lamp is actually not using "white" colored LEDs. Rather, it uses different colors that when shown together produce white light. So with a driver with this capability, you would be able to control the different colors of LEDs in the product to create a full rainbow of colors depending on which are on and which are off.