A Pseudo Constant Switching Frequency Constant-on-time Control for DC-DC Buck Converter in 28nm CMOS Technology

• Main Authors: Chen, Hsin-Chieh, 陳信杰
• Other Authors: Chen, Ke-Horng
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/t7cpub

碩士 === 國立交通大學 === 電機工程學系 === 103 === Conventional constant on-time (COT) control in buck controller needs suitable phase compensation techniques to solve phase delay problem between output ripple and inductor current ripple if low equivalent series resistance (ESR) is used. Switching frequency variation is also affected by external parasitic components and on-resistance of power transistors if process, voltage, and temperature (PVT) variations happen. This thesis proposed calibrated anti-equivalent series inductance (CA-ESL) technique and calibrated gain and BW (CGB) technique to alleviate ESL and ESR effects, respectively, in case of PVT variations. Furthermore, this paper proposed optimum on-time generator (OOG) with transient enhancement (TE) to solve switching frequency variation caused by different output load current change. Pseudo constant switching frequency over a wide load range can be ensured without the need of extra clock control circuits and current sensing circuits. The proposed COT converter fabricated in 28nm CMOS process achieves output ripple of 20mV and power conversion efficiency (PCE) higher than 93% even when ESR is smaller than 10mΩ. The CA-ESL technique can tolerate ESL voltage variation from 0 to 50mV and operation temperature variation from -40 to 120℃. The OOG demonstrates only 0.2% switching frequency variation when 1.4A load current changes.