Boost Converter with Current-Limited Pluse Frequency Modulation for White Light LEDs Driving

• Main Authors: Yun-Chih Chen, 陳昀至
• Other Authors: Chun-Yao Lee
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/24992781168641885751

碩士 === 中原大學 === 電機工程研究所 === 100 === 　　With rapid growth of portable consumer electronics, white light-emitting diodes (LEDs) driving circuits which develop the advantages of small size, high efficiency, and low cost will help to improve competition of such products. Thus, to upgrade protection functions and conversion efficiency of driving circuits has become a crucial subject for power integrated circuit designers. 　　This research aims to improve white light LEDs driving circuits and include three sections. Firstly, about the issue of full loading, the current limited pulse frequency modulation employed in this paper achieves better conversion efficiency than the conventional pulse width modulation, and reduces the control circuit size with fewer components. Consequently, this method can effectively prolong portable electronic products’ battery life and eliminate space of devices. 　　Second, this research proposes current sense FET circuits which can implement integrated design and reduce power loss to improve protection functions of white light LEDs driving circuits. Furthermore, to cope with broken circuits of LEDs and rush currents of driving circuits while power is on, this paper uses over voltage protection and soft start circuits to prevent driving circuits from damage because of over-voltage and rush currents. 　　Finally, different from the conventional power integrated circuits using pulse signals to drive directly, this research presents a study on pre-driver circuits to control power switchs that can improve the capability of pulse signals, reduce the conduction loss and switching loss, and raise the conversion efficiency.