| Summary: | 碩士 === 建國科技大學 === 電機工程系暨研究所 === 101 === Traditional commercially available lead-acid battery chargers are always designed by using high-frequency switching topologies, but the majority, such as flyback, forward, half-bridge topologies etc., are hard switching structures. Hard switching topologies can not make MOSFETs achieve zero voltage and zero current switching, so will cause high switching losses and high MOSFET junction temperature. To improve these shortcomings, this thesis proposes a high efficiency soft switching topology which incorporates LLC resonant converter with synchronous rectification. According to this resonant converter structure, MOSFETs can easily reach zero voltage switching and the current waveforms of the converter are nearly pure sine waves. As a result, the proposed converter has extremely high conversion efficiency, and also can significantly reduce electromagnetic interference (EMI) and radiation interference (RFI). The experimental results confirmed that the proposed resonant chargers with excellent results, the efficiency up to 94.9%, and reached the purpose of saving energy, and can also reduce the heat sink and the overall volume of the charger. In addition, this thesis also utilizes the PIC16F84 single chip to monitor the charging process, and to make the charger with adjustable output voltage function. In practical applications, the battery pack with different voltage can be charged by a single charger with constant current and constant voltage charging functions and automatically reaches equalization effect.
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