This article discusses two driving methods for LED lighting: constant current drivers and constant voltage drivers. The choice between them depends on application requirements. Constant current drivers are suitable for large-scale applications, while constant voltage drivers are ideal for cost-sensitive scenarios that require flexible adjustments to the number of LEDs.

Constant Current or Constant Voltage LED Drivers: Which is Better for You?

If you've decided 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, both can work, but each has its pros and cons.

Constant Voltage Drivers

Constant voltage drivers operate by providing a fixed voltage to the LEDs. They maintain the overall power level by regulating the current output. If your LEDs or LED strips are explicitly rated for a specific voltage, a constant voltage driver may be your best choice. Constant voltage drivers typically come in 12V or 24V specifications. They are generally cheaper than constant current drivers because they require fewer components. Additionally, constant voltage drivers make it easier to replace LEDs. You can add or remove LEDs as needed, and as long as the voltage requirements remain unchanged, the driver should adjust the current to accommodate the new setup (provided all LEDs' current requirements are within the driver's range). When using them, your LEDs need built-in overcurrent protection (OCP). This is usually achieved through resistors, as shown in the red circle in the DigiKey model 289-1316-ND below:

JKL 289-1316-ND LED Strip

When using a constant voltage driver, if the voltage requirement changes slightly (e.g., due to temperature fluctuations), the current may vary significantly to maintain the same power level. This can easily exceed the LED's current limit, leading to fluctuations in light output, reduced lifespan, or even direct damage to the LEDs. Therefore, having OCP on the LEDs is crucial. If your LEDs are designed with this in mind, using a constant voltage driver is safe.

Constant Current Drivers

Constant current drivers operate by providing a fixed current to the LEDs. They maintain the overall power level by regulating the voltage output. Although precise control of current output is easier than voltage output, it requires more components, making it generally more expensive. However, when using constant current drivers, LEDs typically have more stable light output, higher reliability, and better efficiency. The downside is that constant current drivers are more cumbersome when making lighting changes. Altering the number of LEDs naturally changes the system's current requirements, which may cause the driver to increase the voltage to unsafe levels for the LEDs. Therefore, the driver needs to be adjusted or replaced based on the new current requirements.

Constant current drivers are a good choice for most large-scale applications, especially in terms of power usage and maintenance costs. If your LEDs do not have built-in overcurrent protection, you must use a constant current driver, as shown in the example of the 1416-1344-ND model below. Note that this LED strip does not have resistors between the LEDs, so a constant current driver is required.

Lumileds 1416-1344-ND LED Strip

All LEDs requiring constant current should list their current requirements and the acceptable voltage range to avoid damage. Ensure that the driver you choose meets the current requirements and that its voltage output is within the specified range of the LEDs to prevent overdriving them.

SLKOR produces a variety of driver chips, such as the popular model SL27517, which meets automotive-grade requirements. It is an ideal alternative to the Texas Instruments UCC27517DBVR.

The SL27517 is a single-channel 4A high-speed low-side gate driver that efficiently and safely drives MOSFETs, IGBTs, and emerging wide-bandgap power devices. With characteristics of low propagation delay and compact SOT-23, it can achieve the MOSFET switching frequency of hundreds ofkHz.The chip is applicable to synchronous rectification driving of servers and communication power supply. In this condition,the dead time of the synchronous tube MOSFET leads to direct influence on efficiency of the converter. The 4.5V to 20V wide ranges VDD supply voltage can drive MOSFET or GaN power devices effectively.The integrated UVLO protective function can ensure the output low level in abnormal conditions. The -5V to 24V independent input pin voltage ranges can ensure stable working in condition ofover-shoot caused by stray inductance.The voltage threshold value of the input pin is compatible to the TTL level input.

SLKOR SL27517

In Summary

• Constant current drivers are more efficient and less likely to damage your LED investment but are more cumbersome to adjust in the system.

• Constant voltage drivers are cheaper and easier to adjust in terms of the number of LEDs but are more prone to damaging LEDs, consume more energy, and require LEDs to have built-in overcurrent protection. The choice depends on your application needs.