High Efficiency Adaptive Charge Pump Research

Low power loss becomes a very important electronic characteristic for power management chip, especially in the application of portable products based on battery power supply.Principle of high-efficiency auto-adjustable charge pump DC/DC converter is analyzed in details and how to improve the efficiency is also presented in this thesis. An auto-adjustable charge pump embodied in a White LED driver has been taped-out successfully using a 0.5μm CMOS process. It can provide more than 80mA output current in the wide input voltage range from 2.7V to 5.5V. The most important point is that it can change work mode between 1X and 1.5X at fixed input voltage value to improve LED efficiency in the application of LED driver.Based on fundamental principle and basic topology of charge pump DC/DC converters, whole framework and sub-blocks are worked out. Some sub-blocks are analyzed in details, such as 1X/1.5X pump, Oscillator, mode selector, etc.After finishing the charge pump principle analysis and circuit design, we simulated all the sub-blocks and whole chip by applying EDA tools named HSPICE, The simulation results show that the chip has achieved the expectation and proved what was analyzed above.In the application of driving white LED, an auto-adjustable charge pump which adjust work mode according to the forward voltage of load LED and input voltage is presented. The conventional charge pump changes work mode at fixed input voltage value. With forward voltage of white LED lower and lower, the efficiency of traditional charge pump driver is lower and lower, too. The new auto-adjustable charge pump can keep the charge pump working in high efficient 1X mode as long as possible.After circuit simulation, Layout and Post-layout simulation, the chip is taped-out successfully in a famous abroad foundry. Test results show an excellent performance of the chip. And now, the chip has come into market.