What is the difference between constant current and constant voltage LED drivers?
The main difference between the two is in how they regulate and deliver electrical power to the connected load. A constant voltage (CV) driver regulates a specified output voltage and supplies a fixed voltage output to the electronic circuit. CV drivers are ideal when a steady voltage level is required, as they allow the current to vary based on the load’s requirements. This is particularly beneficial in applications where the total quantities of LEDs are unknown or where additional control is needed.
Whereas a constant current (CC) driver will regulate a specified output current and are more suited to applications where the load requires a fixed current. They use a variable voltage to maintain a constant electrical current output. This works by the driver ensuring that the current flowing through the load remains steady, even if the load's resistance changes. In this way, CC LED drivers typically offer better control and a more efficient circuit than CV drivers. LED circuits using CC drivers easily connect the driver’s output directly to LEDs without added regulation. This is possible because the LEDs respond directly to the current driven through them.
Learn more about the differences here.
How to know which driver to choose.
Choosing a suitable driver for your application can be tricky. There are many variables to consider, but typically the best driver for any given design will depend on the load and the application. The application will indicate which features are required and ultimately which driver will be best suited. Other factors to consider include, IP rating, dimming functionality, wireless, output current, CV or CC, output power, output voltage, dimensions, and lifetime.
Learn all you need to know to select a driver here.
What is a constant power driver?
Compared to standard constant current drivers, constant power drivers allow for more flexibility of design. While constant current drivers de-rate as the output current decreases, in a constant power driver the output current can be altered. As output current setting are reduced, the LED driver can produce a higher output voltage, enabling the circuit to take full power from the LED driver in a range of different output current settings.
What are PF and PFC and why they matter in LED drivers?
PF is the abbreviation for power factor and is expressed as a number between 1 and 0. It represents the ratio between actual power and apparent power in an AC (alternating current) power system. Apparent power is the product of the load voltage and load current. If the current and voltage are out of phase, then this could be notably larger than real power.
To maintain a high-power factor, LED drivers must implement power factor correction (PFC). This will reduce the amount of current drawn by an electrical system. This is achieved by locally producing reactive power (KVAr). In turn, this lowers the current drawn from mains. This is vital to consider when selecting LED drivers, because LEDs typically have a low PF which mean that they draw more current than high PF loads, for the equivalent amount of real power transferred. Ultimately, meaning that less power is used, making it more cost-effective and producing a lower carbon footprint.
Numerous standards are currently in place to regulate power factor correction in switch mode power supplies and LED drivers.
What is the difference between lifetime and MTBF?
MTBF stands for mean time between failure, and it refers to the statistical average of time that a LED driver should successfully operate for, before a repairable failure is likely. It does not represent the full expected lifetime of a LED driver. MTBF is useful to convey the reliability of a product. The higher this metric, the longer between technical failures and thus the more reliable the system will be. The MTBF is only relevant during the operating life of a LED driver.
Whereas a product’s lifetime represents the length of time between initial use of a LED driver and the beginning of the wear-out phase. Essentially the entire time period that the product is predicted to last when operating under normal conditions. The lifetime of a product will be determined by the weakest component inside the unit with the shortest life expectancy. For LED drivers, electrolytic capacitors typically have the shortest life expectancy. While LED drivers typically have long life expectancies compared to traditional lighting components, it's essential to consider factors such as quality, operating conditions, usage patterns, and maintenance practices to maximize the lifespan and reliability of the LED driver in your application.
What is potting (encapsulating) and why is it important?
Potting refers to the process of encapsulating electronic components in a protective material to protect them from environmental hazards, mechanical stress, thermal issues, electrical faults, and corrosion. Typically, the material used is an epoxy resin or silicone. The protective coating acts as a crucial barrier to safeguard components from damage caused by things such as moisture, dust, vibration, and temperature fluctuations. Overall, this works to ensure reliable and long-term operation of a system to its full lifetime. Potting LED drivers can increase their durability, making them suitable for a variety of applications, including indoor and outdoor environments.
What is the difference between DALI and DALI-2?
DALI, or Digital Addressable Lighting Interface, first originated in the 90s in relation to ballasts, and in 2002 was promoted to an international standard for lighting communication protocols and interoperability. This certification and promotion were driven by DALI AG under the ZVEI, German Electrical and Electronic Manufacturers Association. It is now governed by the DALI Alliance, formerly known as the Digital Illumination Interface Alliance (DiiA).
Since then, DALI has continued to develop in line with today’s technologies and the standard has grown as the lighting industry has matured and developed. In 2020 DALI-2 was introduced as the new standard (defined by IEC62386), constructed to fill gaps within the original standard. The creation of this new generation of DALI provides greater interoperability, more stringent test protocols and extended commands when compared to the first generation of DALI. DALI-2 includes standardisation of control devices, including light sensors, push buttons and occupancy sensors. DALI-2 is now widely available and utilised in many power control products on the market today. Any devices compliant with the DALI-2 standard will carry the DALI-2 logo.
About Inventronics: In May 2023, OSRAM sold its LED Drivers, Lighting Controls, LED Flex and LED Modules business to Inventronics. These products continue to be branded OSRAM but are now owned, designed, manufactured, and developed by Inventronics. ILS is a gold standard sales partner of OSRAM DS and Inventronics.
