A Buck Mode Charge Pump Operating under Large Current Output

Today, portable electrical devices are more and more popular, and so the relating applying technologies are also fast-growing. The general standard specifications for mobile devices has become Li-ion batteries as the energy storage unit and charging by USB. For the IC designer, overcoming the power dissipation problem and raising the power efficiency has become an important research topic. This thesis presents a buck mode converter designed for portable devices. The charge pump is assembled with a multiple voltage conversion gains switch array, a control circuit and a feedback network, and the designed circuit is employed to transfer voltage down and provides a regulated voltage for load. Since the presented charge pump contains five types of fractional conversion gains to transfer voltage, when the power source changes its voltage level, the charge pump can switch to different conversion gains automatically to optimize the power efficiency. Moreover, a clock boosting technique is utilized to alleviate the charge loss during the duration of switches turning on. Furthermore, the clock block technique can maintain a regular voltage and reduce loss at the same time. Combined with the aforementioned solutions, the charge pump reported in this thesis contains superior power efficiency when compared to a conventional product. With the charge pump, as compared to conventional products under same battery capacity conditions, the operation time of electrical devices will be extended efficiently. The overall circuits included in the charge pump are simulated and processed by TSMC 2P4M 0.35μm 5V CMOS process, with a functional range between 5.5 to 3.3V, and a loading current of up to 250mA at 1.2 volts. The measurement result shows that the designed circuit is partial work. In the first version, the maximum power efficiency is 56% and the minimum power efficiency is 49.6% under the 50mA loading and 4V input voltage.