Constant current vs. constant voltage: Which LED driver do you need?

Light-emitting diodes (LEDs) are one of the most efficient and long-lasting light sources available today. However, for LEDs to be operated reliably and with optimum performance, they require a stable power supply - a so-called LED driver. The reason for this lies in the electrical characteristics of LEDs. In contrast to conventional light bulbs, which are connected directly to a voltage, LEDs have a non-linear current-voltage characteristic. This means that even slight fluctuations in the voltage can lead to significant changes in the current flow, which in turn affects the service life and efficiency of the LED.

An LED driver ensures that the LED receives the correct amount of current or voltage. There are two basic types of LED drivers: constant current and constant voltage drivers. Which variant is the right one depends on the type of LED circuit. While some LEDs are designed to operate at a constant current, there are others that require a constant voltage. The right choice of driver is crucial to avoid overheating, brightness problems or even premature damage to the LEDs.

Constant current LED driver: functionality and advantages

A constant current LED driver regulates the current flowing through the LED and keeps it at a fixed value. LEDs have a characteristic forward voltage that can vary slightly depending on temperature and manufacturing tolerances. However, as the current flow is directly related to the brightness of the LED, a constant current driver ensures that the LED operates at a constant light intensity.

A typical constant current driver outputs a defined current, for example 350 mA, 700 mA or 1 A. The output voltage can vary within a certain range in order to keep the specified current constant. This is particularly important for high-power LEDs or LED modules that are connected in series. As the LEDs are connected in series, their forward voltages add up while the current in the entire circuit remains the same.

The great advantage of a constant current driver is that it enables the LED to operate safely and efficiently. There is no risk of the current rising uncontrollably due to fluctuations in the supply voltage and thus overloading the LED. This type of driver is therefore particularly suitable for high-power LEDs and professional lighting systems.

Constant voltage LED drivers: properties and areas of application

In contrast to constant current drivers, constant voltage LED drivers supply a fixed voltage, for example 12 V or 24 V. These drivers are mainly used for LED strips and LED modules that already have integrated current regulation. In such applications, series resistors or small constant current sources are often installed in the modules to ensure that the LED elements receive the correct current.

A constant voltage driver is ideal for applications where several LEDs are connected in parallel or where a simple installation is preferred. They are particularly practical for decorative lighting, backlighting or LED strips that are flexible and modular. As the power consumption of such systems depends on the number of connected LEDs, the driver must provide sufficient power to supply all connected elements.

Important differences: When you should choose which driver

The choice between a constant current and a constant voltage driver depends entirely on the design of the LEDs used. If you are operating high-power LEDs or LED modules without integrated current regulation, you need a constant current driver. This ensures uniform brightness and protects the LEDs from overloading.

If, on the other hand, LED strips or prefabricated LED modules with integrated current regulation are used, then a constant voltage driver is the better choice. In these cases, it is more important to provide a stable voltage, as the current regulation is already provided by resistors or other circuit elements in the modules.

Typical mistakes when choosing an LED driver and how to avoid them

A common mistake is choosing the wrong type of driver. If an LED that requires a constant current is operated with a constant voltage driver, this can lead to uncontrolled current flow, which can damage the LED. It can also happen that a constant current driver is selected for an application with parallel LEDs, resulting in uneven brightness or even failures.

Another mistake is not calculating the power requirements of the LEDs correctly. If too weak a driver is selected, the LEDs may not operate at full power or the driver may be overloaded. On the other hand, an oversized driver can work inefficiently or lead to high inrush currents.

To avoid such errors, you should always check the technical data of your LEDs and ensure that the driver matches your application exactly in terms of voltage, current and power.

Calculating the right driver power: what you need to look out for

To select the right LED driver, you need to know the exact electrical specifications of your LEDs. For constant current drivers, it is important to determine the correct current, while the voltage is adjusted by the driver within a certain range. Example: If an LED has a forward voltage of 3.5 V and you want to operate four LEDs in series, the driver must provide an output voltage of at least 14 V. At the same time, the specified current (e.g. 700 mA) must be maintained exactly.

With constant voltage drivers, it is crucial that the output voltage corresponds exactly to the nominal voltage of the LED strips or modules. In addition, the driver must deliver enough power (watts) to supply all connected LEDs. A simple way to calculate the minimum power is to multiply the total current consumption by the operating voltage. For example, a 12V LED strip with 2A current consumption requires at least a 24 watt driver.

The right LED driver for your project

Choosing the right LED driver is crucial for the performance, efficiency and service life of your LEDs. Constant current drivers are ideal for high-power LEDs and offer precise control of the current, ensuring uniform brightness and a long service life. Constant voltage drivers, on the other hand, are ideal for LED strips and modules with integrated current regulation as they provide a stable voltage.

Before deciding on an LED driver, you should always check the technical data of your LEDs and calculate what power is required. Errors in selection can lead to overloading, uneven lighting or even defects. However, with the right knowledge, you can ensure that your LED project works reliably and delivers the best possible quality of light.