Given recent LED technology improvements and the drive toward greater energy efficiency, the LED lighting industry—including general illumination from commercial refrigeration to outdoor area lighting—is experiencing explosive growth. As manufacturers expand their offerings or enter the market, it is important they choose reliable, long-life LED power supplies to achieve optimal lighting performance.
In many ways the factors influencing the choice of an LED power supply (LED driver) are similar to those for most other applications. However, some application-specific factors require careful consideration.
Purchasing professionals should first review available choices and how they might fit in various lighting applications. Next, buyers should consider reliability and life, as it is critical to understand the design capabilities of potential suppliers along with their ability to provide support over the product’s long life. To help with this process, let’s look at six factors to consider when selecting an LED power supply.
Factor 1: Mode Of Operation
LED drivers deliver a reliable, predictable, and regulated supply of current to the power supply or power system. A single-module solution, often called a constant-current (CC) driver, provides an output whose current is regulated to directly drive the LEDs.
At higher power levels, the CC function may be implemented separately, and a constant-voltage (CV) power supply feeds the CC driver (Fig. 1). Some drivers/supplies can support both CC and CV modes, providing a single solution that can be reused across multiple lighting platforms (Fig. 2).
Factor 2: Application Power Requirements
Over the past 10 years, the power-handling capabilities of white, single-chip LEDs have increased from tens of milliwatts to watts. Also, their light output efficiency, usually measured in lumens per watt, has grown tenfold from around 10 lm/W to more than 100 lm/W.
Power levels associated with modern LED lighting can vary from less than 1 W for flashlights to several hundred watts for warehouse lights or streetlights. Across this power range, package size and shape will vary significantly, as will features and functions.
For example, a driver to power a recessed “can” light might be approximately 25 W and require TRIAC-compatible dimming, whereas a parking lot light might be 60 to 100 W and require only a simple two-level dimming circuit.
Efficiency improvements in LEDs, optics, and power supplies will result in a downward trend in power consumption for a given light level.
Factor 3: Lighting Environment
Another important consideration is the environment in which the power supply will be used. The supply will be required to operate over a defined temperature range, as low as –20°C or –40°C and as high as 60°C or 80°C. These extreme ranges even can apply to indoor applications at the high end, because of enclosed spaces that trap heat, and at the low end in refrigeration applications.
For indoor lighting fixtures, the power supply may only require minimal protection and require a rating of IP20 or similar. Alternatively, it may need to be dust-tight and protected against vertically dripping water, demanding a rating of IP62 or higher. But for industrial applications, environmental conditions have a greater influence on the choice of LED power supply.
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