Low Voltage Start-up High-efficiency Boost Led Driver Chip Design

As one of the most promising light sources, white LED has many advantages, such as high luminous efficiency, high luminous intensity, long life period etc.When driving a white LED, constant current is a necessity. Utilizing boost structure to drive white LED is widely used in portable lighting market. This paper mainly focuses on the chip design of white LED driver for battery power.In the main part of this paper, firstly, Simplis is used for architecture simulation and block definition. Using TSMC 0.6um process, sub-blocks are built:Ultra-low start-up circuit supports 0.58V start-up voltage;The novel internal current-sense circuit adapts a simpler structure than the previous art with more accurate and faster response;Loading-adjustment circuit is proposed especially for battery-powered LED driver. It not only provides accurate LED current, but also greatly prolongs the battery life time. An over-temperature protection circuit is also proposed for N-sub process, which lacks PNP transistors.Finally, the whole chip measurement results are given:start-up voltage 0.58V, maximum ripple voltage 244mV; efficiency reaches 87% when heavy loading and over 77% over all loading range; over-voltage protection, over-temperature protection, low-voltage protection and over-current protection are also provided in this chip.