A Design Of Off-line Flyback LED Constant Current Driver Chip

In the background of global energy shortages, LED(Light Emitting Diode) has attracted great attention in the field of lighting as a type of green light source. Compared with traditional light source, LED has the advantages of energy saving, environmental protection, high efficiency, long life, small volume, high reliability, etc.The quality of LED driver power affects the reliability of LED product directly. In the process of design, factors need to be considered are: cost, volume, output power, accuracy, power factor, efficiency, etc. And the dimming, security, life are also need to be considered.The task of this thesis is to design an off-line flyback LED constant current driver IC. In the design process, in order to improve the power factor, an off-line flyback LED constant current driver IC with PFC is realized as the organic combination of traditional flyback controller and PFC theory. The main work of this thesis is listed as follows:1. The operation modes of LED driver IC are analyzed. An off-line flyback constant current driver IC framework is proposed, and the output current equation is deduced.2. The performance of each sub-module of the off-line flyback constant current driver IC is analyzed and reasonable circuit structures are chosen. In order to make each sub-module to achieve the required index, Cadence Spectre is used to simulate. Modules involved in this paper include the reference module, oscillator, multiplier, DCM detection module and error amplifier. The concrete circuits of the modules mentioned above are given and verification is completed.3. After the completion of each sub-module simulation, the overall circuit is simulated. The protection functions are verified, including: open circuit protection, short circuit protection and over temperature protection. The performance of the chip is tested. The precision of the current is ±4.5% and the efficiency is above 90%.4. The layout of the chip is drawn based on the CSMC 0.5μm 80 V BCD process. Reasonable layout and wiring are realized and the effect of matching and interference on the performance of the chip is considered.