Battery protection device

• US 6,222,346 B1
• Filed: 08/09/2000
• Issued: 04/24/2001
• Est. Priority Date: 08/18/1999
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Mori, Iichiro
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/635,054
• Time in Patent Office: 258 Days
• Field of Search: 320/134, 320/162, 320/163, 320/164, 324/430
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

A control circuit detects the battery voltage E1 of the rechargeable battery, and the terminal voltage E2 across the input/output terminals that are connected to the rechargeable battery through a charge/discharge circuit. When the battery voltage E1 is lower than a charge-prohibiting voltage and higher than a discharge-prohibiting voltage, the control circuit turns on the first and second FETS, which are connected in series to the charge/discharge circuit. When the battery voltage E1 is higher than the charge-prohibiting voltage, the first FET is turned off, and when the battery voltage is higher than the terminal voltage, the first FET is turned on. When the battery voltage E1 is lower than the discharge-prohibiting voltage, the second FET is turned off, and when the battery voltage E1 is higher than the terminal voltage E2, the second FET is turned on.

Claims

1. A battery protection device incorporated in a rechargeable battery, comprising:

a first switching means and a second switching means connected in series in a charge/discharge circuit for connecting a positive electrode of the rechargeable battery to a positive input/output terminal and a negative electrode of the rechargeable battery to a negative input/output terminal; and

a control means for

detecting (i) a battery voltage between the positive electrode and the negative electrode of the rechargeable battery and (ii) a terminal voltage between the positive input/output terminal and the negative input/output terminal;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage above which charging of the rechargeable battery must be prohibited, and turning on the second switching means when the battery voltage is above a discharge-prohibiting voltage below which discharging of the rechargeable battery must be prohibited;

turning off the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is higher than the battery voltage, and turning on the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is lower than the battery voltage; and

turning off the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the terminal voltage is lower than the battery voltage, and turning on the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the terminal voltage is higher than the battery voltage.

2. A battery protection device incorporated in a rechargeable battery, comprising:

a first switching means and a second switching means connected in series in a charge/discharge circuit connecting a positive electrode of the rechargeable battery to a positive input/output terminal and a negative electrode of the rechargeable battery to a negative input/output terminal; and

a control means for

detecting (i) a battery voltage between the positive electrode and the negative electrode of the rechargeable battery and (ii) a current direction in the charge/discharge circuit;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage above which charging of the rechargeable battery must be prohibited, and turning on the second switching means when the battery voltage is above a discharge-prohibiting voltage below which discharging of the rechargeable battery must be prohibited;

turning off the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the current detection is that of a charge current, and turning on the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the current direction is that of a discharge current; and

turning off the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the current direction is that of a discharge current, and turning on the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the current direction is that of a charge current.

3. The battery protection device according to claim 2, wherein the current direction is detected from the voltage across one or both of the first switching means and the second switching means.

4. The battery protection device according to claim 2, wherein the current direction is detected from the voltage across a resistor connected in series to the charge/discharge circuit.

5. A battery protection device incorporated in a rechargeable battery, comprising:

a first switching means and a second switching means connected in series in a charge/discharge circuit connecting a positive electrode of the rechargeable battery to a positive input/output terminal and a negative electrode of the rechargeable battery to a negative input/output terminal; and

a control means for

detecting (i) a battery voltage between the positive electrode and the negative electrode of the rechargeable battery and (ii) a terminal voltage between the positive input/output terminal and the negative input/output terminal;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage above which charging of the rechargeable battery must be prohibited, and turning on the second switching means when the battery voltage is above a discharge-prohibiting voltage below which discharging of the rechargeable battery must be prohibited;

turning off the first switching means and the second switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is higher than the battery voltage, and turning on the first switching means and the second switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is lower than the battery voltage; and

turning off the first switching means and the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the terminal voltage is lower than the battery voltage, and turning on the first switching means and the second switching means when the battery voltage is lower than the discharge-prohibiting voltage and the terminal voltage is higher than the battery voltage.

6. A battery protection device incorporated in a rechargeable battery comprising a plurality of cells connected in series, comprising:

a first switching means and a second switching means connected in series in a charge/discharge circuit for connecting a positive electrode of the rechargeable battery to a positive input/output terminal and a negative electrode of the rechargeable battery to a negative input/output terminal; and

a control means for

detecting (i) a battery voltage between the positive electrode and the negative electrode of the rechargeable battery, (ii) module voltages of battery modules into which the plurality of cells constituting the rechargeable battery are divided in equal numbers, and (iii) a terminal voltage between the positive input/output terminal and the negative input/output terminal;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage above which charging of the rechargeable battery must be prohibited, and turning on the second switching means when the difference between the module voltages is below a certain voltage difference;

turning off the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is higher than the battery voltage, and turning on the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is lower than the battery voltage; and

turning off the second switching means when the terminal voltage is lower than the battery voltage and the difference between the module voltages is above a certain voltage difference, and turning on the second switching means when the terminal voltage is higher than the battery voltage and the difference between the module voltages is above a certain voltage difference.

7. A battery protection device incorporated in a rechargeable battery comprising a plurality of cells connected in series, comprising:

a first switching means and a second switching means connected in series in a charge/discharge circuit for connecting a positive electrode of the rechargeable battery to a positive input/output terminal and a negative electrode of the rechargeable battery to a negative input/output terminal;

a temperature detection means for detecting the temperature of the rechargeable battery; and

a control means for

detecting (i) a battery voltage between the positive electrode and the negative electrode of the rechargeable battery, (ii) module voltages of battery modules into which the plurality of cells constituting the rechargeable battery are divided in equal numbers, and (iii) a terminal voltage between the positive input/output terminal and the negative input/output terminal;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage above which charging of the rechargeable battery must be prohibited and the terminal voltage is higher than the battery voltage, turning off the first switching means when the battery voltage is higher than the charge-prohibiting voltage and the terminal voltage is higher than the battery voltage, and turning on the first switching means when the terminal voltage is lower than the battery voltage;

turning on the second switching means when a difference between the module voltages is below a discharge-prohibiting voltage difference above which discharging of the rechargeable battery must be prohibited and the terminal voltage is lower than the battery voltage, turning off the second switching means when the difference between the module voltages is higher than said discharge-prohibiting voltage difference and the terminal voltage is lower than the battery voltage, and turning on the second switching means when the terminal voltage is higher than the battery voltage; and

turning off the first and the second switching means when the battery temperature is outside a predetermined temperature region;

wherein the charge-prohibiting voltage and the discharge-prohibiting voltage difference are controlled depending on a function representative of the battery temperature.