CONSTANT CURRENT, CONSTANT VOLTAGE, AND CONSTANT CURRENT CHARGER

摘要

PROBLEM TO BE SOLVED: To fully charge a lithium ion secondary battery in a short time by a simple circuit, without detecting its minute charging finish current. SOLUTION: When a portable telephone is connected to an external charger 11, constant-current charging is performed by a rated charging current Is. When the voltage of its battery 17 becomes a charging completion voltage Voff, the voltage is controlled by a charging voltage control circuit 12, and constant- voltage charging is performed by the completion voltage Voff. If the charging current decreases up to (charging completion current Ioff + error current Ierror), constant-current charging by the charging completion current Ioff is performed with a precise constant-current circuit 19. When the battery voltage becomes the completion voltage Voff, charging is finished. Since charging completion is decided by the charging completion voltage, detection of a minute charging completion current is unnecessary, and it becomes possible to perform full charging by a simple circuit safely certainly in a short time.