Design Of Multiple Modes WLED Driver Controller

Compared with the traditional lighting source,because of the LEDs' advantages such as small size,high efficiency,long life-span and less pollution,it's no doubt that LEDs will become the mainstream application in lighting market.As the rapid development of high power white LED,the power management ICs for LED are applied more widely.To fulfill these requirements,there are two main research directions in LED driver IC:high performance,wide compatibility driver controller and specific function ICs to meet the special requirments of LED.This thesis analyzed the status of the LED driver circuits,controllers and their development trend.Combined with the practical needs,a multiple modes white LED driver controller which can be used in different topologies of PWM DC/DC converters for LED driving was proposed.Firstly,according to the topologies and control schemes of the PWM converters, the system solution scheme was chosen,which can be applied in Buck,Boost and Buck-Boost topologies.The main characteristics of this IC were:high precision bandgap voltage reference which suited for wide supply voltage range;A adjustable, hybrid structure operational amplifier for different current sense method in different topologies was designed to solve the compatibility issue;A oscillator integrated piecewise slope compensation circuit improved the peak current mode control system's stability.The designed blocks and system were simulated by Cadence Spectre, and the simulation results achieved expectation.Secondly,considering dimming requirements of the LED,a PWM dimming mode was accomplished in Boost Mode,and analog dimming mode in Buck-Boost(Buck) mode.Aiming at the need of high efficiency,based on the existence system architecture,a novel no sense resistor mode with some control circuit blocks was proposed.The floor plan and layout of the controller were under 1.5μmBCD process.The chip was fabricated and tested in different PCB demo boards for different modes.The testing results showed the proposed IC satisfied the different LED driver topologies' requirments,the input voltage range was 3～15V,and the PWM dimming ratio can achieve 3000:1.All the test results met the design specification well...