There are various types of LED drivers (or LED power supply) on the market, including constant voltage, constant current, constant power, DALI, Emergency, Wireless, Dimming, etc. Among them, constant current and constant voltage LED drivers are the most common. Constant current drivers are more popular in the market because they can better avoid thermal runaway. But why is the constant voltage LED driver also necessary? Let's find out the basic knowledge and application requirements behind it.
What is Constant Voltage LED Driver?
Unlike constant current driver, which focuses on maintaining a constant current, constant voltage LED drivers (CV LED drivers) are power supplies that provide a fixed output voltage (usually 12V or 24V DC), and the current fluctuates based on the required power. The constant voltage driver is suitable for powering low-voltage LED systems. To help you understand better, take the example of the specifications of UPSHINE's constant voltage LED driver.
If the current is lower than the 3.2 amperes maximum shown in the table, the VNG-75TV-24 driver will maintain a constant 24VDC voltage.
To ensure that the LED operates safely at a constant voltage, LEDs using constant voltage drivers often have built-in current limiting resistors to prevent thermal runaway. Because the voltage-current characteristic of LEDs is nonlinear, small voltage changes can cause dramatic current changes (see the figure below). Without these resistors, the current could become too high and damage the LED.
Constant voltage LEDs are usually connected in parallel. This means that each LED unit in the circuit receives the same voltage. For example, if you are powering three 12V LED strips in parallel, the constant voltage driver ensures that each strip receives a stable 12V voltage, while the total current varies depending on the number of strips.
How to Choose a Constant Voltage Driver that Complies with LED Product Labels？
There are several important criteria to consider when choosing a compliant constant voltage LED driver for a particular LED product. The LED voltage, current and total power are the main considerations. The output power of the LED driver should be equal to or greater than the total power requirement of the LED. Let's take the product label of the LED light strip as an example:
Firstly, determine the LED voltage
You need to know the voltage data of the LED light strip. As shown in the figure, the input voltage is 12V.
Secondly, calculate the LED total power
Total Power = Power/Meter x Total Length. The label in the figure above shows that the power of the light strip is 8W/Meter. If a 5-meter-long light strip needs to be installed, the total power is 40W (5M * 8W/M = 40W).
Finally, choose a suitable LED driver
The power of the constant voltage LED driver must be greater than or equal to the total power of the LED strip. So in this example, an LED driver with at least 40W power needs to be selected. Besides, the output voltage of the LED driver should be equal to the LED strip voltage; that is, the output voltage of the constant voltage driver requires 12V.
Summary: Constant voltage LED drivers and LED product matching must meet the following two conditions:
- The output voltage of the constant voltage LED driver is equal to the input voltage of the LED product.
- The LED driver power is greater than or equal to the LED total power.
Outdoor Protection Rating of Constant Voltage LED Drivers
Constant voltage LED drivers are usually external LED drivers that are separated or remotely located from the LED. This is to prevent the heat dissipated by the driver from negatively affecting LED life.
External constant voltage drivers are inevitably exposed to the outside environment, so we need to emphasize the IP rating of this driver.
The IP rating indicates the protection of the driver enclosure against external environmental factors. The protection rating is expressed as two digits. The first digit indicates the protection against solid objects. The second digit indicates the protection against water. The protection rating ranges from safe and dry indoor environments (IP20) to harsh outdoor environments (IP67).
The specific standards are shown in the following table:
Dimming Function of Constant Voltage LED Drivers
Dimming is a key function in many LED lighting applications, which enables users to adjust brightness and create dynamic lighting effects. Constant voltage LED drivers also have dimming function options.
Generally, the dimming option must be indicated in the specification; if not, the driver is not dimmable by default.
Dimmable constant voltage drivers usually need to be used with external dimmers or control devices specified in the data sheet. And make sure the driver and dimming type match exactly.
The output voltage of a constant voltage non-dimmable LED driver is pre-set to a fixed value that strictly matches the LED system requirements. For example, the driver will continue to output precise 24 volts when the lighting system requires a 24V power supply. So it is suitable for scenarios with constant light intensity requirements.
When Should You Choose a Constant Voltage LED Driver?
Constant voltage LED drivers are commonly used in LED light strips, linear lights, batten lights, etc. These products have strict requirements for maintaining consistent lighting and often have current regulatory mechanisms inside. This is in line with constant voltage drivers with a fixed forward voltage.
Here are some common applications:
Linear Lighting
LED strips are long and have many light beads inside, so they are often connected in parallel.
Also, these products usually have built-in resistors or current regulators, so they only need to provide the correct voltage for optimal performance. Constant voltage drivers can ensure uniform brightness across the entire strip.
In projects that require long rows or continuous LED strips, such as architectural lighting, constant voltage drivers can also easily provide the same voltage to multiple strips.
Low Voltage LED Systems
When using low voltage LED systems (such as 12V or 24V), constant voltage LED drivers are necessary to ensure safe operation. This is usually used in automotive lighting, such as dashboards and taillights.
Another common low voltage lighting area is signage lighting. Using constant voltage drivers can ensure uniform lighting across the signage.
By understanding the basic knowledge, dimming capabilities and outdoor protection levels of the constant voltage LED driver, combined with its specific application requirements, you can select and apply them more effectively. You can also consider a constant current driver solution for products with high power or high precision requirements.
For more guidance on choosing the right driver for your products, please feel free to contact us or browse our range of constant voltage LED drivers.
