Secondary battery charging circuit

• US 5,477,126 A
• Filed: 08/08/1994
• Issued: 12/19/1995
• Est. Priority Date: 10/15/1990
• Status: Expired due to Term

• Current Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Original Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Inventors: Shiojima, Nobuo
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US08/286,923
• Time in Patent Office: 498 Days
• Field of Search: 320/21, 320/22, 320/23, 320/24, 320/35
• US Class Current: 320/138
• 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 battery charging circuit comprising:

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

a secondary charging source for supplying a charging current smaller than the charging current supplied from said first charging source to said secondary battery;

switching means for connecting said first charging source to said secondary battery during a first charging period, and connecting said second charging source to said secondary battery during a second charging period;

first temperature detection means for detecting that a temperature of said secondary battery has reached a first setting temperature, and generating a detection output;

second temperature detection means for detecting that a temperature of said secondary battery has reached a second setting temperature, and generating a detection output;

temperature change rate detection means for detecting a rate of change in temperature of said secondary battery with respect to time;

comparator means for comparing an output value from said temperature change rate detection means during a charging operation to said secondary battery with a setting value, and for, when the output value reaches the setting value, generating an inverted output; and

control means for controlling a change of charging methods, and stop of the charging operation,

said control means including at least one of;

means for, when the inverted output from said comparator means is generated during the first charging period, ending the first charging period so as not to substantially start the second charging period, and for, when the detection output from said first temperature detection means is generated during the first charging period, starting the second charging period, and ending the second charging period in response to one, generated earlier, of the detection output from said second temperature detection means and the inverted output from said comparator means during the second charging period;

means for starting the second charging period in response to one, generated earlier, of the detection output from said first temperature detection means and the inverted output from said comparator means during the first charging period, and ending the second charging period in response to one, generated earlier, of the detection output from said second temperature detection means and the inverted output from said comparator means during the second charging period; and

means for starting the second charging period in response to one, generated earlier, of the detection output from said first temperature detection means and the inverted output from said comparator means during the first charging period, and ending the second charging period in response to the detection output from said second temperature detection means.