LED driver power supplies must be constant current sources mainly because of the nature of LEDs.

　　As we know, LEDs have a relatively narrow operating current range within which they can function optimally. If the current is too low, the LED will not emit sufficient light, and its efficiency will be reduced. On the other hand, if the current is too high, the LED can overheat, leading to a shorter lifespan, color shift, or even complete failure. A constant current source can precisely control the current flowing through the LED, ensuring that it operates within the recommended current range at all times.

　　Furthermore, in multi LED configurations, such as in LED strips or high power LED arrays, a constant current source is essential for uniform light output. Each LED in a string may have slightly different forward voltage drops. If a constant voltage source is used, the LEDs with lower forward voltage drops will draw more current, while those with higher forward voltage drops will draw less current. This results in uneven brightness and color distribution among the LEDs. A constant current source, however, ensures that each LED in the array receives the same amount of current, regardless of their individual forward voltage differences, thus providing consistent brightness and color across the entire LED assembly.

　　In terms of energy efficiency, a constant current drive can also contribute to better overall performance. By maintaining a stable current, the LED operates at its most efficient point, reducing power wastage in the form of heat dissipation due to over current or under current conditions. This not only extends the lifespan of the LED but also helps in reducing the overall energy consumption of the lighting system.