If you’ve made the decision to install LED lighting, you may have noticed there are multiple ways to power it. One of the biggest decisions is whether to use a constant current driver or a constant voltage driver. In some cases, either will work but there are advantages and disadvantages to both.
Constant Voltage Drivers
Constant voltage drivers work by supplying a fixed voltage to your LEDs. They accomplish this by varying the current output to maintain the overall power level. If your LED or LED strip specifically call out that it’s for use with a specific voltage, this is likely your best option. These are often seen in 12V or 24V varieties. Constant voltage drivers tend to be less expensive than constant current drivers, as they require less components. Also, constant voltage drivers are easier when it comes to making LED changes. You can add or remove LEDs as needed and as long as the voltage requirements stay the same the driver should be able to increase or reduce the current to match the new setup (assuming the current requirements for all LEDs don’t go outside the driver’s range). In order to use them, your LEDs need to have built-in Over Current Protection (OCP). Generally, this is in the form of resistors as seen circled in red on DigiKey part number 289-1316-ND below:
With constant voltage drivers, if the voltage requirement changes even slightly (such as with a change in temperature), there can be a very dramatic change in current in order to keep the same power level. This can easily exceed the current limits of the LEDs causing light output fluctuations, shortened lifespan, or even outright failure of the LED. This makes having OCP on the LEDs extremely important. If your LEDs are designed for this, you should be safe using a constant voltage driver.
Constant Current Drivers
Constant current drivers work by supplying a fixed current to your LEDs. This is done by varying the voltage output to maintain the overall power level. While it is easier to precisely control the current output than the voltage output, it does require more components and thus is usually more expensive. But, with properly controlled current driving your LEDs you’ll typically have a more stable light output, better reliability, and better efficiency. A downside is constant current drivers are also a bit more finicky when it comes to making lighting changes. Changing the number of LEDs will of course change the current requirements of the system, which could cause the driver to raise the voltage to levels unsafe for the LEDs. This necessitates changing or adjusting your driver to the new current requirements.
Constant current drivers are a good choice for most large-scale applications where power usage and maintenance costs are a factor. LEDs without OCP built in also require them, 1416-1344-ND below is an example. Notice the lack of resistors between the LEDs and therefore must be used with a constant current driver.
All LEDs that need constant current should list both the current requirements, along with a voltage range that they can accept without damage. Make sure that your selected driver matches the current requirement, and the voltage output is within the LED specified range to prevent overdriving the LEDs.
In short, Constant Current Drivers are more efficient and are less likely to damage your LED investment but make changing your system more cumbersome. Constant Voltage Drivers are less expensive and make it easier to change the number of LEDs but are more prone to damaging your LEDs, use more energy, and require your LEDs have built-in Over Current Protection. What is right for you depends on your application needs. To see what DigiKey offers in both, click the links below.
Constant current examples
Constant voltage examples
As always, if you need help choosing something to fit your needs, feel free to reach out here on our forum and one of our technicians will be happy to assist you.