Battery charger and charge control method

• US 20050017674A1
• Filed: 06/29/2004
• Published: 01/27/2005
• Est. Priority Date: 07/14/2003
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sato, Kazumi
• Granted Patent: US 7,714,532 B2
• Time in Patent Office: Days
• US Class Current: 320/106
• CPC Class Codes: H02J 7/00041 in response to measured battery parameters, e.g. voltage, current or temperature profile
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Safety against error setting of a primary battery in a dedicated battery charger for secondary batteries can be assured even when the battery charger is of a timer type advantageous for cost reduction. A switching circuit (2) is connected between terminals (13, 15), and terminal (14, 16) are connected. Terminals (15, 17) are connected, and terminals (16, 18) are connected. The positive pole of a battery (3) set n position is connected to the terminal (17), and the negative pole is connected to the terminal (18). A battery discriminating circuit (4) connects to the positive pole and the negative pole of the battery (3) set in position, and judges whether the battery (3) is a primary battery or a secondary battery. Depending upon the result of the discrimination, the battery discriminating circuit (4) to the switching circuit (5) to turn it on or off. A capacitor (6) and a resistor 7 are connected in parallel between a timer circuit (9) and a ground potential. The switching circuit (5) and a resistor (8) are connected in series between the timer circuit (9) and the ground potential. Once the switching circuit (2) turns on, a constant voltage source circuit 1 supplies a charging direct current to the secondary battery.

Claims

1. A battery charger for controlling the length of time for charging a secondary battery with a timer circuit, comprising:

discriminating means for discriminating whether a battery set in charging position is a primary battery or a secondary battery;

a time constant means for setting the length of charging time by means of a time constant; and

a time constant switching means for switching the time constant,

wherein the time constant switching means switches the time constant to shorten the length of charging time when the battery is judged a primary battery.

2. The battery charger according to claim 1 wherein the discriminating means compares the terminal voltage of the battery with a reference voltage to acknowledge that the battery is a secondary battery when the terminal voltage is lower than the reference voltage and to acknowledge that the battery is a primary battery when the terminal voltage is equal to or higher than the reference voltage.

3. A charge control method for controlling the length of time for charging a secondary battery with a timer circuit, comprising:

discriminating whether a battery set in charging position is a primary battery or a secondary battery;

setting the length of charging time by means of a time constant; and

switching the time constant to shorten the length of charging time when the battery is judged a primary battery.

4. The charge control method according to claim 3 wherein the discrimination of the battery is accomplished by comparing the terminal voltage of the battery with a reference voltage to acknowledge that the battery is a secondary battery when the terminal voltage is lower than the reference voltage and to acknowledge that the battery is a primary battery when the terminal voltage is equal to or higher than the reference voltage.