Research And Design Of A LED Driver With High Precison Constant Current

With the threat of the global warming and energy conservation, energy-saving technology has become a hot topic and got more attention. The traditional lighting technology cannot meet the environmental protection requirements. Nowadays, the LED technology becomes more and more popular, and it all depends on its high efficiency and low power consumption. The research on the more stable LED lighting never stopped.The paper introduces the design of a high-precision constant current LED driver IC, which is mainly used in the daily low-power lighting. Different with the common open-loop constant current chip, the chip use a new closed-loop mode to get higher precision. Via this mode, the chip can obtain more accurate feedback signal and dynamically regulate the MOSFET’s off-time. In order to achieve the goal of low power consumption and high efficiency, the chip includes a source-driver circuit, which can reduce the quiescent current. The module circuit must fulfill the request, at the same time, the circuit best to reduce the number of devices to get smaller size and lower cost.The chip uses BUCK structure. The input voltage range from 167 VAC to 265 VAC, and the output voltage is 10V~98V. According to the daily lighting requirement, the peak current is 90 mA and the average current is 60 mA. Based on the closed-loop, the chip can gain a ±3% current constant precision.Firstly, the paper briefly introduces some characteristics of the LED, such as the light-emitting principle and the luminous efficiency. Then, it focus on the basic knowledge of LED drive, describes some switching power supply topologies and the modulation mode. The next chapter is the whole chip’s framework and the principle introduction of the closed-loop constant current. Through the sub-module design and simulation, the internal circuit has been described. Finally, the paper designs the external device parameters and the whole chip simulation has been done.