The Basics of LED Drivers and How to Choose the Right One

What are LED Drivers?

What is an LED Driver?

An LED driver is an electrical device that regulates power to an LED or a string of LEDs. It is a crucial piece to an LED circuit and to operate without one will result in system failure.

Using one is very important in preventing damage to your LEDs as the forward voltage (Vf) of a high-power LED changes with temperature.

The Forward Voltage is the amount of voltage needed to get current to flow across a diode. As temperature increases, the forward voltage of the LED decreases, causing the LED to draw more current.

The LED will continue to get hotter and draw more current until the LED burns itself out, and this is also known as Thermal Runaway.

The LED driver is a self-contained power supply which has outputs that are matched to the electrical characteristics of the LED(s). This helps avoid thermal runaway as the constant current LED driver compensates for the changes in the forward voltage while delivering a constant current to the LED.

Constant Current LED Drivers

Constant current LED drivers are designed for a designated range of output voltages and a fixed output current (mA).

LEDs that are rated to operate on a constant current driver require a designated supply of current usually specified in milliamps (mA) or amps (A). These drivers vary the voltage along an electronic circuit which allows current to remain constant throughout the LED system.

The 15W DA Series Constant Current Dimmable LED Driver by LTF is a good example shown on the right.

Higher current ratings do make the LED brighter, but if not regulated, the LED will draw more current than it is rated for.

Thermal Runaway refers to excess current beyond the LEDs maximum drive current which results in drastically lower LED life-spans and premature burn outs due to increased temperature.

A constant current driver is the best way to drive high power LEDs as it maintains a consistent brightness across all LEDs in-series.

Advantages of Using a Constant Current LED Driver

When you’re building your own fixture or working with high powered LEDs, it is of your best interest to use constant current drivers because:

a. They avoid going way beyond the maximum current specified for the LEDs, therefore avoiding burnout/thermal runaway.

b. They are easier for designers to control applications, and help create a light with more consistent brightness.

Constant Voltage LED Drivers

Constant voltage drivers are designed for a single direct current (DC) output voltage.

Most common constant voltage drivers (or Power Supplies) are 12VDC or 24VDC. An LED light that is rated for constant voltage usually specifies the amount of input voltage it needs to operate correctly.

A constant voltage power supply receives standard line voltage (120-277VAC). This is the type of power that is typically output from your wall outlets around the home.

Constant Voltage Drivers switch this alternating current voltage (VAC) to a low direct current voltage (VDC). The driver will always maintain a constant voltage no matter what kind of current load is put on it.

An example of a constant voltage power supply is the 96W DS Series Linear Constant Voltage Driver by LTF.

Advantages of Using Constant Voltage LED Driver

You use a constant voltage LED driver only when using an LED or array that has been specified to take a certain voltage. This is helpful as:

a. Constant voltage is a much more familiar technology for the design and installation engineers.

b. The cost of these systems can be lower, especially in larger scale applications.

What to Consider When Choosing an LED Driver?

A. Type and Number

Determine the type and number of LED lights you’ll be using in your setup and how they’ll be arrayed.

If your lights are wired in series, such as with ground lights or decking lights, you’ll require a constant-current LED driver.

If they’ll be wired in parallel, such as with LED tape or LED strip lights, then you’ll need to have a constant-voltage LED driver.

B. Milliamp Rating

You’ll need to ensure that the milliamp rating on your lights matches the milli-amp rating of your LED driver.

Electrical current is measured in amps and milliamps. While there are a number of different milliamp ratings for LED lights, the most common are 350mA and 700mA.

C. Wattage Rating

Check to ensure that the wattage rating of your LED driver is greater than or equal to the total wattage of all lights wired to that driver.

As an example, if you have five 3-watt ground lights wired to your driver, the driver must have a wattage rating of at least 15 watts.

When using LED tape, you need to multiply the wattage rating per meter of tape times the length of the tape.

As an example, if the tape is rated at 15 watts per meter and the total tape length is 3 meters, your LED driver will have to carry at least a 45-watt rating.

D. Output Voltage

Make sure that the output voltage of the LED driver is compatible with the input voltage of your LED light(s).

Some constant-current LED drivers have a wide range of output voltage, such as 6 to 24 volts, making them more universal and compatible with a number of different LED lights.

Constant-current LED drivers, however, may output a very specific voltage, which may not work with your LED lights. Damage may be caused by using incorrect voltage, so it’s important to carefully check this.

Important Factors When Buying an LED Driver

#1 Output Voltage

Always consider the voltage required by your light(s). If they require 12 volts for operation, use a 12-volt driver.

When using a constant-current LED driver, consider the LEDs’ current output (in amps or milliamps) and ensure your driver will produce power within your lights’ specified range.

With constant-current drivers, both current range and voltage have to be considered. With constant-voltage drivers, only the voltage range needs to be considered.

#2 Input Voltage

While most LED drivers will accept a range of input voltages, ensure that the voltage available at your location is compatible with the driver you’re using.

Most household voltage is 120 volts, while most commercial and industrial voltages are 277 volts. If you’re unsure, check with your electrician.

When dealing with constant-current LEDs, consider their current input as well.

#3 Wattage

Calculate the total wattage of your light or lights and ensure your driver has a maximum wattage capability greater than this.

Don’t use a driver with a light or lights that exceed its max wattage or that use less than 50% of its max wattage.

#4 Dimming

Constant-current and constant-voltage LED drivers can both be made with the ability to dim, but the dimming capability must be stated on the dimmer’s specs, otherwise it’s safe to assume the system is not dimmable.

Thank you for reading along and hopefully this post has provided you with the information needed in understanding and choosing the right LED Driver for your application.

Meanwhile, you may want to learn more and browse through our wide range of LED Drivers.