Secondary batteries having a protective circuit

• US 20030064257A1
• Filed: 10/01/2002
• Published: 04/03/2003
• Est. Priority Date: 10/02/2001
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Iwasaki, Norikazu, Furuta, Kazutaka, Kawazu, Masami, Tamura, Hisaya
• Granted Patent: US 7,163,757 B2
• Time in Patent Office: Days
• US Class Current: 429/7
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A secondary battery with high safety is provided. A heater and a diode are connected in series, and a thermistor is connected in parallel with thus formed series circuit. A fuse is connected in series with thus formed parallel circuit to form a protective circuit, which is attached to an accumulator to complete a secondary battery. In the case of overcharging, the accumulator generates heat so that the thermistor heats up to increase the resistance value. As a result, the current pass through the heater, which generates heat to break the fuse. In the case of short circuit, the diode is reverse-biased and no current passes through the heater so that the fuse does not break.

Claims

1. A secondary battery comprising:

a rechargeable/redischargeable accumulator; and

a protective circuit connected to the accumulator wherein charging/discharging current of the accumulator flows through the protective circuit,

the protective circuit comprising;

a heater;

a diode connected in series with the heater the diode being forward-biased when a charging current is supplied from an external DC voltage source to the accumulator;

a thermistor connected in parallel with a series circuit, the series circuit comprising the heater and the diode, the thermistor having a resistance value increasing with temperature rise; and

a fuse connected in series with a parallel circuit comprising the series circuit and the thermistor.

2. The secondary battery of claim 1 wherein the protective circuit is attached to the accumulator, and the thermistor is heated up by the accumulator heating.

3. The secondary battery of claim 1 wherein the fuse is adapted to break based on a selected amount of heat generated by the heater.

4. The secondary battery of claim 2 wherein the fuse is adapted to break based on a selected amount of heat generated by the heater.