Study And Design Of LED Driver With Buck

With the rapid development of LED lighting technology in recent ten years, it became a new fourth-generated semiconductor solid light source after the filament lamp, fluorescent lamp and gas discharge lamp, and it was featured by high light efficiency, high reliability, no pollution, and long life,etc. Along with the improvement of people's life, new demand and high degree are put forward to the quality of light source, also to the automatic and intelligent development of modern appliances. However, the realization of automatic and intelligent control of LED is greatly limited by the various characteristics owned by LED itself. How to design the corresponding control circuit according to the requirements of different LED driving power supply and whether the the intelligent level can be improved, which are the key factors to determine whether the LED lamp can enter the smart furniture industry or not.The performance of LED lamp is greatly influenced by driver. Based on the BUCK topology structure, this thesis aims to introduce a LED driver, which can not only make the LED driver stable work, but also provide a variety of protection ways such as open circuit protection, short circuit protection, over-temperature protection, dynamic over-temperature protection and so on. Then, the author makes the research from the circuit structure, component parameter calculation and selection, circuit function simulation and analysis. The simulation result also verifies the practicability, stability, and feasibility of this driver.This paper first systematically introduces the features of LED lamp and driver system; then, this paper describes the current situation of LED, especially the type driven by constant current, based on which the paper reasonably looks ahead the prospect of LED. Next, this thesis expatiates the related procedures of designing LED driving circuit from the aspects of the LED electrical characteristics, LED driver topology, especially the BUCK topology, and control methods. Finally, combined with the basic knowledge of the above chapters, the author designs a constant current driving control chip specially for LED lighting, which is applied into non-isolated BUCK LED system. This chip is characterised by small peripheral devices, excellent constant current, high efficiency, low cost, and with no auxiliary winding.The chip realizes the high precision of constant current control via direct sampling output current. The adoption of middle inductive current in critical continuous model can not only avoid the reverse recovery of main diode, but also reduce the losses of switch so as to guarantee the high efficiency of this system. Among them, the HV starting technology is adopted in the chip. When the input voltage is in the range of 90V~260V, the starting time can be less than 0.1S, which means that the LED lamp lights as soon as one opens it. The design of module in this chip is mainly devided into two parts: functional module and protection module. As for the functional module, it includes reference voltage module provided by band-gap reference, internal power supply module, zero-crossing detecting module, peak current sampling module, driving circuit module and logic circuit module with oscillator. As for the protection module, it contains over-temperature protection circuit, dynamic over-temperature protection circuit, UVLO circuit, open inner circuit, short circuit protection. Meanwhile, the author makes the analysis and research to the functions and performance parameters of each sub-module based on the simulation results.The design is finished based on the Shang Hua 0.8 ?m BCD 700 V process and Cadence Design System software. Also the relevant layout design is finished via Virtuoso layout design software. After completion of the tape-out, the test results of the chip include load adjustment rate, linear adjustment rate, efficiency, PFC, open / short circuit protection test, start test, temperature rise test, high temperature test and performance parameter test. Through the analysis of simulation data and curve, the practicability of LED driver is shown.