Patent ID: 7453239
Filing Date: 2008-11-18
Classification: H02J,H02M

Abstract:
1. A charging device for connection to an external power supply and to charge a rechargeable battery, comprising: a switching element for increasing or decreasing charging power supplied to the rechargeable battery; a PWM controlling circuit that has an output terminal connected to the switching element and outputs pulse signals from the output terminal for intermittently turning the switching element on and off; a current detecting circuit for detecting current flowing through the switching element and outputting voltage corresponding to the current flowing through the switching element; a correcting circuit for correcting output voltage of the current detecting circuit by a correction amount that changes depending on power supply voltage from the external power supply, a setting means for setting a target value of charging current flowing through the rechargeable battery; and a charging current detecting circuit for detecting the charging current flowing through the rechargeable battery, and wherein the PWM controlling circuit also has a limiter terminal into which corrected voltage from the correcting circuit is input and the PWM controlling circuit stops outputting the pulse signals when the corrected voltage input to the limiter terminal is equal to or above a predetermined limiter value, wherein the PWM controlling circuit adjusts a duty ratio of the switching element so that the charging current will be adjusted to the set target value; and the setting means reduces the target value of the charging current when the detected charging current becomes smaller, by a predetermined amount, than the set target value.