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Constant Voltage vs. Constant Current Drivers

Constant Voltage vs. Constant Current Drivers

LED lights require a driver in order to provide and properly deliver the required output. Whether internally or externally incorporated depends on the type of LED bulb. For example an A19 LED light bulb has an integrated internal driver while cove lights, downlights, and tape lights require an external driver. LED drivers  are available in either constant current or constant voltage, so what’s the difference?

Both constant current and constant voltage drivers act as a power supply for an LED light source, but the delivery methods differ. Similar to ballasts for fluorescent lamps or transformers for low voltage bulbs, LED drivers provide and regulate the necessary voltage in order to maintain a safe and consistent operation.  Understanding the difference between the two types can not only assist in properly powering your LEDs but also help avoid some serious damages to your lighting investments.

What is a Constant Current LED Driver?

                       Constant Current LED Driver

                       Constant Current LED Driver

Constant current LED drivers are designed for a range of output voltages and a fixed output current (amps). An LED which is rated to operate on a constant current driver requires a designated supply of current (amps). This type of driver varies the voltage along an electronic circuit which allows a constant electrical current through the device. An example of a constant current LED driver is displayed below.

Constant Current Example
Input Voltage Output Voltage Output Current (Amps)
90-264VAC 4-10VDC 700mA*
Note* The current is set to only one designated value.

Even though a higher amp rate does make the LED brighter, if it is not regulated it will eventually over-drive what the LED is rated for. Thermal-runaway refers to excess current beyond the LED’s rating which results in reduced life-span and premature burn out. Since the light can maintain a consistent brightness, constant current is typically used for signs, back-lighting, and commercial LED displays. As the name implies, only constant current LEDs are compatible with these types of drivers.

What is a Constant Voltage LED Driver?

                      Constant Voltage LED Driver

                      Constant Voltage LED Driver

Constant Voltage drivers are designated for a single direct current (DC) output voltage, usually 12VDC or 24VDC. An LED light rated for a constant voltage requires a consistent amount of output voltage to ensure a proper operation. The driver receives a standard voltage around 120-277 volts, typically found in residential receptacles (outlet). This voltage is in the form of alternating current voltage (VAC), which the driver steps-down into a low direct current voltage (VDC). This means that the driver will maintain a constant voltage no matter the load current.  An example of a constant voltage LED driver is displayed below.

Constant Voltage Example
Input Voltage Output Voltage Output Current (Amps)
120-277VAC 12VDC** 1 Amp Max
Note** The voltage is set to only one designated value.

With a set voltage, the driver will maintain a constant voltage as long as the current stays below the 1-amp maximum shown in the example. Most often, constant voltage drivers are implemented in signage when the amount of LED loads will vary. Constant voltage applications include cabinet lights and tape lights but are not limited to those categories.

Which LED Driver is Better?

Constant current and constant voltage products are generally not compatible with each other, although there are drivers that are able to function as both. Even though a constant voltage driver may be slightly less efficient, it enables a full flexibility to allow a greater final load size. On the other hand, constant current LED drivers are manufactured to only operate constant current devices with specific ratings, making them the more efficient of the two drivers.

When selecting the right LED driver, verify the specs to determine whether it operates on either constant current or constant voltage to prevent frying your LEDs. If you still have questions on which type of LED driver is the best fit for you, contact our customer service team at 1-800-624-4488 Monday through Friday (7 am to 7 pm CST). Check our blog frequently for more articles about the wonders of lighting and keep in touch with us via FacebookTwitter, Google+LinkedIn, or Pinterest.

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