PROTECTION CIRCUIT FOR SECONDARY BATTERY, BATTERY PACK, AND ELECTRONIC DEVICE

• US 20110059337A1
• Filed: 08/03/2010
• Published: 03/10/2011
• Est. Priority Date: 09/09/2009
• Status: Abandoned Application

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: YOSHIDA, Hideharu
• Application Number:
  US12/849,247
• Publication Number:
  US 20110059337A1
• Time in Patent Office: Days
• US Class Current: 429/7
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A protection circuit for protecting a secondary battery includes a temperature detector unit detecting a secondary battery temperature to output a detected signal indicating the detected temperature, an overcharge alarm determination unit determining whether the temperature is equal to or above an upper limit of a standard-temperature range based on the detected signal, and subsequently selecting a first overcharge alarm voltage when the temperature is below the upper limit thereof, or a second overcharge alarm voltage when the temperature is equal to or above the upper limit thereof to output a signal indicating whether a secondary battery voltage is equal to or above the selected one of the first and second overcharge alarm voltages, and an alarm signal generator unit generating, when the secondary battery voltage is equal to or above the selected one of the first and second overcharge alarm voltages, an alarm signal based on the output signal.

Claims

1. A protection circuit for protecting a secondary battery, comprising:

a temperature detector unit configured to detect a temperature of the secondary battery and to output a detected signal indicating the detected temperature;

an overcharge alarm determination unit configured to determine whether or not the detected temperature is equal to or higher than an upper limit of a standard-temperature range based on the detected signal, and to subsequently select a predetermined first overcharge alarm voltage when the detected temperature is lower than the upper limit of the standard-temperature range, or to subsequently select a predetermined second overcharge alarm voltage that is lower than the predetermined first overcharge alarm voltage when the detected temperature is equal to or higher than the upper limit of the standard-temperature range, so as to output a signal indicating whether or not a voltage of the secondary battery is equal to or higher than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage; and

an alarm signal generator unit configured to generate, when the voltage of the secondary battery is equal to or higher than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage, an alarm signal based on the signal output from the overcharge alarm determination unit.

2. The protection circuit as claimed in claim 1,

wherein the overcharge alarm determination unit is further configured to determine whether the detected temperature is equal to or lower than a lower limit of the standard-temperature range based on the detected signal, and to subsequently select the predetermined first overcharge alarm voltage when the detected temperature is higher than the lower limit of the standard-temperature range, or to subsequently select a predetermined third overcharge alarm voltage that is lower than the predetermined first overcharge alarm voltage when the detected temperature is equal to or lower than the lower limit of the standard-temperature range.

3. The protection circuit as claimed in claim 2,

wherein the alarm signal generator unit is further configured to determine, based on the detected signal, whether or not the detected temperature is equal to or higher than a predetermined upper limit of a charge temperature that is higher than the upper limit of the standard-temperature range or whether or not the detected temperature is equal to or lower than a predetermined lower limit of the charge temperature that is lower than the lower limit of the standard-temperature range, and to subsequently generate, when the detected temperature is equal to or higher than the predetermined upper limit of the charge temperature, or when the detected temperature is equal to or lower than the predetermined lower limit of the charge temperature, the alarm signal regardless of levels of the voltage of the secondary battery.

4. The protection circuit as claimed in claim 1, further comprising:

an overcharge detector unit configured to detect whether or not the voltage of the secondary battery is equal to or higher than a predetermined overcharge detection voltage;

an charge overcurrent detector unit configured to detect whether or not a charge current of the secondary battery is equal to or higher than a predetermined first current value;

a first signal generator unit configured to generate a first control signal for controlling cutting off of a charging path of the secondary battery when at least one of a first condition in which the voltage of the secondary battery is equal to or higher than the predetermined overcharge detection voltage and a second condition in which the charge current of the secondary battery is equal to or higher than the predetermined first current value is satisfied;

an overdischarge detector unit configured to detect whether or not the voltage of the secondary battery is equal to or lower than a predetermined overdischarge detection voltage;

a discharge overcurrent detector unit configured to detect whether or not a discharge current of the secondary battery is equal to or higher than a predetermined second current value; and

a second signal generator unit configured to generate a second control signal for controlling cutting off of a discharging path of the secondary battery when at least one of a third condition in which the voltage of the secondary battery is equal to or lower than the predetermined overdischarge detection voltage and a fourth condition in which the discharge current of the secondary battery is equal to or higher than the predetermined second current value is satisfied.

5. The protection circuit as claimed in claim 3,

wherein the alarm signal generator unit generates a predetermined first level alarm signal when the detected temperature is higher than the predetermined lower limit of the charge temperature and lower than the predetermined upper limit of the charge temperature, and the voltage of the secondary battery is equal to or higher than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage,

wherein the alarm signal generator unit generates a predetermined second level alarm signal when the detected temperature is higher than the predetermined lower limit of the charge temperature and lower than the predetermined upper limit of the charge temperature, and the voltage of the secondary battery is lower than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage, and

wherein the alarm signal generator unit generates a pulsed alarm signal regardless of levels of the voltage of the secondary battery when the detected temperature is equal to or higher than the predetermined upper limit of the charge temperature, or when the detected temperature is equal to or lower than the predetermined lower limit of the charge temperature.

6. The protection circuit as claimed in claim 3,

wherein the alarm signal generator unit generates a predetermined first level alarm signal when the detected temperature is higher than the predetermined lower limit of the charge temperature and lower than the predetermined upper limit of the charge temperature, and the voltage of the secondary battery is equal to or higher than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage,

wherein the alarm signal generator unit generates a predetermined second level alarm signal when the detected temperature is higher than the predetermined lower limit of the charge temperature and lower than the predetermined upper limit of the charge temperature, and the voltage of the secondary battery is lower than the selected one of the first overcharge alarm voltage and the second overcharge alarm voltage, and

wherein the alarm signal generator unit generates a predetermined third level alarm signal regardless of levels of the voltage of the secondary battery when the detected temperature is equal to or higher than the predetermined upper limit of the charge temperature, or when the detected temperature is equal to or lower than the predetermined lower limit of the charge temperature.

7. A battery pack comprising:

a secondary battery; and

the protection circuit as claimed in claim 1.

8. An electronic devices comprising the battery pack as claimed in claim 7.