Highly Efficient DC-DC Converters for System-on-chip Applications

• Main Authors: Hong-Wei Huang, 黃宏瑋
• Other Authors: Sy-Yen Kuo
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/00557230771971435835

博士 === 國立臺灣大學 === 電子工程學研究所 === 96 === This paper proposes temperature-independent load sensor (LS), optimum width controller (OWC), optimum dead-time controller (ODC), and tri-mode operation to achieve high efficiency over an ultra-wide-load range. Higher power efficiency and wider loading current range require rethinking the control method for DC-DC converters. Therefore, a highly efficient tri-mode DC-DC converter is invented in this paper for system-on-chip (Soc) applications, which is switched to sleeping mode at very light load condition or to high speed mode at heavy load condition. The efficiency improvement is upgraded by inserting new proposed dithering skip modulation (DSM) between conventional pulse-width modulation (PWM) and pulse-frequency modulation (PFM). In other words, an efficiency-improving DSM operation raises the efficiency drop because of transition from PWM to PFM. Importantly, DSM mode can dynamically skip the number of gate driving pulses, which is inverse proportional to load current. Simplistically and qualitatively stated, the novel load sensor automatically selects optimum modulation method and power MOSFET width to achieve high efficiency over a wide load range. Moreover, optimum power MOSFET turn-on and turn-off delays in synchronous rectifiers and reduced ground bounce can save much switching loss by current-mode dead-time controller. Experimental results show the tri-mode operation can have high efficiency about 90% over a wide load current range from 3mA to 500mA. Owing to the effective mitigation of the switching loss contributed by optimum power MOSFET width and reduction of conduction loss contributed by optimum dead times, the novel width and dead-time controllers achieve high efficiency about 95% at heavy load condition and maintain the highly efficient performance to very light load current about 0.1mA.