Charge/discharge protection circuit utilizing a charger connection recovery circuit that cycles a discharge control transistor on and off while a battery is over-discharged during charging

• US 7,772,805 B2
• Filed: 05/15/2007
• Issued: 08/10/2010
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: Nisshinbo Micro Devices Incorporated (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: Yamamoto, Norifumi, Fujiwara, Akihiko
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): HERNANDEZ, MANUEL J
• Application Number:
  US11/996,937
• Publication Number:
  US 20090251104A1
• Time in Patent Office: 1,183 Days
• Field of Search: 320/132, 320/134
• US Class Current: 320/134
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 50/202 Casings or frames around the primary casing of a single cell or a single battery
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A charge/discharge protection circuit that protects a secondary battery from overcharge, over-discharge, charge over-current, and discharge over-current is disclosed. The charge/discharge protection circuit includes an overcharge detection circuit, an over-discharge detection circuit, a charge over-current detection circuit, a discharge over-current detection circuit, a charge control FET that is turned off when overcharge is detected and when charge over-current is detected, a discharge control FET that is turned off when over-discharge is detected and when discharge over-current is detected, and a charger connection recovery circuit that controls on/off operations of the discharge control FET. When connection with a charger is established at a time over-discharge is detected and the discharge control FET is turned off, the discharge control FET is forcefully turned on after a first predetermined time elapses.

Claims

1. A charge/discharge protection circuit that protects a secondary battery from overcharge, over-discharge, charge over-current, and discharge over-current, said charge/discharge protection circuit comprising:

an overcharge detection circuit;

an over-discharge detection circuit;

a charge over-current detection circuit;

a discharge over-current detection circuit;

a charge control FET that is turned off when overcharge is detected by the overcharge detection circuit and when charge over-current is detected by the charge over-current detection circuit;

a discharge control FET that is turned off when over-discharge is detected by the over-discharge detection circuit and when discharge over-current is detected by the discharge over-current detection circuit; and

a charger connection recovery circuit that controls on/off operations of the discharge control FET such that when connection with a charger is established at a time over-discharge is detected and the discharge control FET is turned off, the discharge control FET is forcefully turned on after an over-discharge recovery delay time elapses,

wherein the discharge control FET is turned off after an over-discharge detection delay time elapses from the time the discharge control FET is forcefully turned on.

2. The charge/discharge protection circuit as claimed in claim 1, wherein

when a battery cell voltage is less than or equal to an over-discharge detection voltage, operations of turning on the discharge control FET after the elapse of the over-discharge recovery delay time and turning off the discharge control FET after the elapse of the over-discharge detection delay time are repeated.

3. The charge/discharge protection circuit as claimed in claim 1, wherein

the over-discharge recovery delay time and the over-discharge detection delay time are determined according to variations in internal circuit temperature characteristics, charger temperature characteristics, over-discharge recovery delay time temperature characteristics, and over-discharge detection delay time temperature characteristics.

4. A battery pack comprising the charge/discharge protection circuit as claimed in any one of claims 1, 2 or 3.

5. An electronic apparatus comprising a battery pack, said battery pack including a charge/discharge protection circuit that protects a secondary battery from overcharge, over-discharge, charge over-current, and discharge over-current, said charge/discharge protection circuit comprising:

an overcharge detection circuit;

an over-discharge detection circuit;

a charge over-current detection circuit;

a discharge over-current detection circuit;

a charge control FET that is turned off when overcharge is detected by the overcharge detection circuit and when charge over-current is detected by the charge over-current detection circuit;

a discharge control FET that is turned off when over-discharge is detected by the over-discharge detection circuit and when discharge over-current is detected by the discharge over-current detection circuit; and

a charger connection recovery circuit that controls on/off operations of the discharge control FET such that when connection with a charger is established at a time over-discharge is detected and the discharge control FET is turned off, the discharge control FET is forcefully turned on after an over-discharge recovery delay time elapses,

wherein the discharge control FET is turned off after an over-discharge detection delay time elapses from the time the discharge control FET is forcefully turned on.

6. A mobile phone comprising a battery pack, said battery pack comprising:

a charge/discharge protection circuit that protects a secondary battery from overcharge, over-discharge, charge over-current, and discharge over-current, said charge/discharge protection, circuit comprising;

an overcharge detection circuit;

an over-discharge detection circuit;

a charge over-current detection circuit;

a discharge over-current detection circuit;

a charge control FET that is turned off when overcharge is detected by the overcharge detection circuit and when charge over-current is detected by the charge over-current detection circuit;

a discharge control FET that is turned off when over-discharge is detected by the over-discharge detection circuit and when discharge over-current is detected by the discharge over-current detection circuit; and

a charger connection recovery circuit that controls on/off operations of the discharge control FET such that when connection with a charger is established at a time over-discharge is detected and the discharge control FET is turned off, the discharge control FET is forcefully turned on after an over-discharge recovery delay time elapses,

wherein the discharge control FET is turned off after an over-discharge detection delay time elapses from the time the discharge control FET is forcefully turned on.