In addition to the LED driver circuit to meet the safety requirements, the other basic functions should be two aspects:
One is as far as possible to maintain a constant current characteristic, especially the + 15% changes had taken place in the power supply voltage, still should be able to keep the output current in the range of + 10% changes. Main reason is: 1, to avoid driving current exceeds the maximum ratings, affecting its reliability. 2. To obtain the desired brightness requirements, and ensure the consistency of each LED brightness and color.
Two is the drive circuit should maintain a low power consumption, so as to make the LED system efficiency is maintained at a higher level.