LED lighting is conditional. The forward voltage is applied  both ends of the PN junction, so that the PN junction itself forms an energy level (actually a series of energy levels), and electrons jump at this energy level and generate phons  emit light. Therefore, the voltage applied across the PN junction is required  drive the LED  emit light. In addition, because LEDs are characteristic-sensitive semiconducr devices with negative temperature characteristics, it is necessary  stabilize and protect the working state of the LEDs during the application process, thus giving rise  the concept of LED "driving".

　　The forward volt-ampere characteristic curve of the LED is very steep (the forward dynamic resistance is very small), and it is more difficult  supply power  the LED. It cannot be directly powered by a voltage source like an ordinary incandescent lamp, otherwise the voltage fluctuation will increase slightly, and the current will increase. Large enough  burn the LED. In order  stabilize the working current of the LED and ensure the normal and reliable operation of the LED, various LED drive circuits have emerged.

　　Some of the LED drive circuits are simple (only 1~2 ballast components are used), and some are complex (constituted with several electronic components); some are suitable for low-power LED arrays, and some are suitable for high-power LED arrays; Some use DC power supply, and some use AC power supply; some have good performance and long service life; some have poor performance and high failure rate, so it will reflect the life of the LED.