Series White Led Driver Ic Design

The subject of the dissertation originates from a cooperative project funded by an oversea company. The dissertation aims to design a white LEDs driving IC which is highly demanded by the international market. The driving IC can drive up to six white LEDs in series with a constant current to provide display backlighting for two (main and sub-) displays in cell phones and other portable devices.With the increasing popularity of color liquid crystal displays (LCD) in cell phones, PDAs, digital cameras, and other portable devices, white LEDs are becoming popular backlighting sources and white LEDs driving ICs become the highlight in the design field of power managing ICs. Many famous analog IC companies offer a great number of white LEDs driving ICs. According to the working principle, the driving ICs can be classified into two types: in parallel and in series. The driving IC designed in the dissertation not only meets the demands of the markets, but is a reference to the design of more powerful driving ICs. Therefore, the dissertation is both practically and academically important for the research of white LEDs driving ICs.The research can be summarized as follows:Firstly, on the basis of analyzing of the working principles and designing requirements of white LEDs driving ICs, the author designs the whole circuit architecture. The architecture adopts a current-mode, step-up DC-DC converter to drive white LEDs in series with constant current. Secondly, primary sub-block circuits are designed and simulated, through the following modules: CTRL_GM, ENABLE, OSC_SLOPE, PWM_COMP, and DRIVER_IS. Finally, the simulation of the whole circuit is conducted.The innovation of the dissertation is indicated as follows: In the discussion of the CTRL_GM sub-block, the transconductance stability of operational transconductance amplifier is deeply studied. Three parameters, the fractional temperature coefficient, the sensitivity of transconductance to voltage supply and improvement factor, are introduced. The analysis of the three parameters indicates that the OTA designed and improved in the dissertation is better than classical bipolar OTAs in terms of...