Secondary battery charging circuit

• US 5,483,145 A
• Filed: 08/08/1994
• Issued: 01/09/1996
• Est. Priority Date: 07/25/1991
• Status: Expired due to Term

• Current Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Original Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Inventors: Enomoto, Sadakazu, Shiojima, Nobuo
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US08/287,308
• Time in Patent Office: 519 Days
• Field of Search: 320/21, 320/22, 320/23, 320/24, 320/35
• US Class Current: 320/150
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A secondary battery charging circuit of this invention includes a charging source for supplying a charging current to a secondary battery, a temperature detection unit for generating an output which changes almost linearly with respect to a change in temperature of the secondary battery during a charging operation, a differential unit for obtaining a differential value of an output from the temperature detection unit, a comparator unit for comparing the differential value during the charging operation with a setting value, and for, when the relationship between the two values is reversed, generating an inverted output, a timer circuit unit, started simultaneously with start of the charging operation of the secondary battery, for generating a timer output after an elapse of a predetermined period of time, and a charge control unit for controlling the charging operation of the secondary battery in response to one, generated earlier, of the inverted output from the comparator unit, and the timer output from the timer circuit unit.

Claims

1. A secondary charging circuit comprising:

a charging source for supplying a charging current to a secondary battery;

temperature detection means for detecting a temperature of said secondary battery, and outputting an electrical signal corresponding to the detected temperature;

analog-to-digital conversion means for converting an output signal from said temperature detection means into a digital value, and outputting the digital value as temperature data;

storage means for sequentially storing a plurality of temperature data at a predetermined time interval output from said analog-to-digital conversion means while updating old temperature data; and

control means for, when the number of temperature data corresponding to differences between one of latest temperature data and oldest temperature data and the remaining temperature data of the plurality of temperature data stored in said storage means, which differences exceed a predetermined value, reaches a predetermined number, decreasing the charging current from said charging source.

2. A circuit according to claim 1, wherein said storage means has a plurality of memory areas, and includes means for fetching new temperature data output from said analog-to-digital conversion means at the predetermined time interval, and erasing the oldest temperature data.