Research And Design Of A Low Dropout Linear Current Regulative HB-LED Driver

High Brightness LED as the most promising light source has many advantages, such as high luminous efficiency, high luminous intensity, economical and safety for environment, long life period etc. It is widely used in automotive illumination, display, the flash on cell-phone camera, back lighting of panel and other illuminating applications. The HB LED driver is indispensable, and become the star of power management research. Providing constant current is the major task. For its briefness, low noise and EMI, fast transient response, mini bulk and inexpensive, linear current regulator is well suited for illuminating fields using storage battery as power supply, such as automotive illumination. In this thesis, the research and design of a high voltage, 350 mA, LDO linear current regulative HB LED driver is demonstrated. According to the functions the IC should have, the structure and functional blocks of the system were determined, then the direct schematic design of some subcircuits had also been conducted in reference to other function-like circuits, using the"Bottom-to-up"methodology. Then, the whole chip simulation and verification were conducted to examine the matching between the design and the requirements of specification. The thesis put emphasis on the whole design of the chip and improvement on efficiency of the linear current regulator, especially on the design of some critical blocks, such as reference and voltage regulator block, error amplifier block and thermal protect block.On the basis of above research, a LDO linear current regulative HB LED driver is designed and fabricated in Jazz 0.5μm BCD process. Simulation results show that the chip can achieve±2.86% output current accuracy and 0.5V low-dropout voltage, and it features the functions of over temperature protection, over current limiting, PWM dimming at output current as well as low 204 mV current-sense reference. Besides, optimization design for the LED driver improved the efficiency effectively. The post simulation has proved that the circuit works very well and every electrical characteristic meets the specification of the data sheet which proves a successful design.