Integrated Switching-Based Charger with Active Balancing Modules

• Main Authors: Yu-Chi, Hsu, 徐彧淇
• Other Authors: 劉邦榮
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/b822va

碩士 === 國立臺北科技大學 === 電機工程系 === 106 === Using fossil fuels as a source of energy for cars could cause air pollution and greenhouse gas increment, leading to a flourishing electric car market. The power source of electric vehicle is from lithium battery; however, the maximum voltage of a lithium battery is 4.2V and its low capability is hard to drive for a long distance. To solve the issues, lithium batteries are used in series and parallel. But, the series and parallel batteries suffer the problem of voltage imbalance. This thesis proposes an integrated switching-based charger with active balancing modules. This charger has current and voltage control loops. The current control loop adjusts the current command according to the battery voltage, so that the charger has charging characteristics of trickle current and constant current. When the battery voltage approaches to the rate voltage, the control circuit switches to the voltage control loop, leading to the charger operating in constant voltage charging mode. A resistor divider, comparators, and transistors are used to charge or discharge the batteries to achieve voltage balance. The proposed charger is implemented with TSMC 0.35 μm 2P4M CMOS process technology. The chip area containing PADs is 1.491x1.499mm2. The specifications of the charger are the input voltage of 10~12-V, output voltage of 8.4V, and switching frequency of 1 MHz. The trickle current and constant current are set as 50 and 500 mA, respectively. According to the simulation results, the charger proposed in this paper has a trickle-constant current-constant voltage characteristic in charging the capacitor, and the voltage balance of the two capacitors can be carried out in the charging regardless of the voltage imbalance of the capacitor at the initial stage of charging. And after the completion of the charge after the two capacitor voltage difference can be in the expected range.