The Design of Low-Voltage Flyback Converter and Li-Ion Battery Charger

• Main Authors: Jay-Ann Yo, 游傑安
• Other Authors: Jiann-Jong Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/jjzty9

碩士 === 國立臺北科技大學 === 電腦與通訊研究所 === 99 === The first part which is low-voltage low-noise flyback converter using delta-sigma modulator is presented in this thesis. The synchronous flyback converter is adopted in this system. Comparing with traditional flyback converter, the second-side switch of synchronous flyback converter is more ideal because RON of power transistors is lower than diode. The delta-sigma modulator which makes error signal digitalize and produces one-bit quantity output signal to adjust duty cycle is controller in this system. Besides, this modulator which utilizes noise-shaping and oversampling characteristics to reduce in-band noise is suitable for RF, audio or communication applications. The proposed circuit is implemented with TSMC 0.35um CMOS DPQM process. The second part offerings the low-voltage li-ion battery charger in the latter half of the thesis. For solving energy problem in portable product, utilizing energy harvesting system to catch selected energy into super capacitance which be charged to 1.8V. And then, the proposed chip charges li-ion battery from the energy source super capacitance. When li-ion battery voltage is lower than 4.2V, the charging system which charges battery by constant 100mA or constant voltage is in constant current mode. However, while battery voltage is higher than 4.2V, the charging system supplies constant 4.2V to li-ion battery in constant voltage mode.