BATTERY PACK

• US 20090051323A1
• Filed: 10/23/2008
• Published: 02/26/2009
• Est. Priority Date: 10/27/2003
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Bunya Sato, Masahiko Hayakawa
• Inventors: Hayakawa, Masahiko, Sato, Bunya
• Granted Patent: US 7,649,340 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• 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 protecting circuit monitors a voltage of a secondary battery and supplies the signal to permit a discharge to a gate terminal of a discharge control FET when the voltage is equal to or more than a lower limit value in a rated voltage range. When the discharge control FET receives this signal, it is connected and passes a discharge current. In the other cases, it shuts off the discharge current. Further, when the voltage is equal to or more than a predetermined value, a signal of a voltage of a battery voltage or more is supplied from a voltage converter to the gate terminal. When the voltage is equal to or less than an upper limit value in the rated voltage range, the protecting circuit supplies the signal to permit a charge to a gate terminal of a charge control FET. Further, when the voltage is equal to or more than a predetermined value, the voltage output from the voltage converter is supplied to the gate terminal. A battery pack in which by applying the voltage of the battery voltage or more to the gate terminal, the discharge control FET and the charge control FET are controlled and an energy loss is suppressed to the minimum is provided.

Claims

1. A battery pack having a secondary battery therein, comprising:

one or more voltage converters;

a discharge control FET to permit or shut off a discharge of said secondary battery in accordance with a first signal which is supplied to a gate terminal of said discharge control FET;

a charge control FET to permit or shutoff a charge of said secondary battery in accordance with a second signal which is supplied to a gate terminal of said charge control FET;

a protecting circuit to permit output of the first signal that permits the discharge to said gate terminal of said discharge control FET when a battery voltage of said secondary battery is equal to or more than a lower limit value in a rated voltage range of said secondary battery or to permit output of the second signal that permits the discharge to said gate terminal of said charge control FET when the voltage of said secondary battery is equal to or less than an upper limit value in the rated voltage range of said secondary battery; and

an output terminal of said voltage converter connected to at least either the gate terminal of said discharge control FET or the gate terminal of said charge control FET.

2. The battery pack according to claim 1, wherein if the gate terminal of said discharge control FET is connected to the output terminal of said voltage converter in a predetermined range that is equal to or more than said lower limit value, then an output voltage which is supplied to said output terminal is higher than the battery voltage of said secondary battery.

3. The battery pack according to claim 1, wherein if the gate terminal of said charge control FET is connected to the output terminal of said voltage converter in a predetermined range that is equal to or less than said upper limit value, then the output voltage which is supplied to said output terminal is higher than the battery voltage of said secondary battery.

4. The battery pack according to claim 1, further comprising:

a first switch for the discharge control FET connected between the output terminal of said voltage converter and the gate terminal of said discharge control FET;

a second switch for the charge control FET connected between the output terminal of said voltage converter and the gate terminal of said charge control FET;

a first resistor connected between an output terminal of said protecting circuit from which the signal to permit said discharge is outputted and the gate terminal of said discharge control FET;

a first diode anode connected to the output terminal of said voltage converter;

a first diode cathode connected to one terminal of said first switch for the discharge control FET;

a second resistor connected between the output terminal of said protecting circuit from which the signal to permit said charge is outputted and the gate terminal of said charge control FET;

a second diode anode connected to the output terminal of said voltage converter; and

a second diode cathode connected to one terminal of said second switch for the charge control FET.

5. The battery pack according to claim 4, wherein:

said first switch for the discharge control FET includes a first n-channel type FET, a first p-channel type FET, and a third resistor,

said second switch for the charge control FET includes a second n-channel type FET, a second p-channel type FET, and a fourth resistor,

the cathode of said first diode is connected to a source terminal of said first p-channel type FET of said first switch for the discharge control FET,

the gate terminal of said discharge control FET is connected to a drain terminal of said first p-channel type FET of said first switch for the discharge control FET,

both end terminals of said third resistor are respectively connected to the source terminal and a gate terminal of said first p-channel type FET of said first switch for the discharge control FET,

the gate terminal of said first p-channel type FET of said switch for the discharge control FET is connected to a drain terminal of said first n-channel type FET of said first switch for the discharge control FET,

a gate terminal of said first n-channel type FET of said first switch for the discharge control FET is connected to the output terminal of said protecting circuit from which the signal to permit said discharge is outputted,

a source terminal of said first n-channel type FET of said first switch for the discharge control FET is connected to a minus terminal of said secondary battery,

the cathode of said second diode is connected to a source terminal of said second p-channel type FET of said second switch for the charge control FET,

the gate terminal of said charge control FET is connected to a drain terminal of said second p-channel type FET of said second switch for the charge control FET,

both end terminals of said fourth resistor are respectively connected to the source terminal and a gate terminal of said second p-channel type FET of said second switch for the charge control FET,

the gate terminal of said second p-channel type FET of said second switch for the charge control FET is connected to a drain terminal of said second n-channel type FET of said switch for the charge control FET,

a gate terminal of said second n-channel type FET of said second switch for the charge control FET is connected to the output terminal of said protecting circuit from which the signal to permit said charge is outputted, and

a source terminal of said second n-channel type FET of said second switch for the charge control FET is connected to the minus terminal of said secondary battery.

6. The battery pack according to claim 4, further comprising:

a cathode of a third diode connected to one terminal of said first resistor;

an anode of said third diode connected to the output terminal of said protecting circuit from which the signal to permit said discharge is outputted;

a cathode of a fourth diode connected to one terminal of said second resistor;

an anode of said fourth diode connected to the output terminal of said protecting circuit from which the signal to permit said charge is outputted;

a third resistor having end terminals respectively connected to the gate terminal and a source terminal of said discharge control FET; and

a fourth resistor having end terminals respectively connected to the gate terminal and a source terminal of said charge control FET.

7. A battery pack having a secondary battery therein, comprising:

one or more voltage converters;

a discharge control FET to permit or shut off a discharge of said secondary battery in accordance with a first signal which is supplied to a gate terminal;

a charge control FET to permit or shut off a charge of said secondary battery in accordance with a second signal which is supplied to a gate terminal;

a voltage comparator to compare an output voltage of said voltage converter with a voltage of said secondary battery and to output a result of the comparison as a voltage comparison signal;

a first switch for the discharge control FET to control the supply of the signal of the voltage of said secondary battery to the gate terminal of said discharge control FET;

a second switch for the discharge control FET to control the supply of the signal of the output voltage of said voltage converter to the gate terminal of said discharge control FET;

a first switch for the charge control FET to control the supply of the signal of the voltage of said secondary battery to the gate terminal of said charge control FET;

a second switch for the charge control FET to control the supply of the signal of the output voltage of said voltage converter to the gate terminal of said charge control FET; and

a protecting circuit to permit output of the first signal that permits the discharge to said gate terminal of said discharge control FET when the voltage of said secondary battery is equal to or more than a lower limit value in a rated voltage range of said secondary battery, or to permit output of the second signal that permits the discharge to said gate terminal of said charge control FET when the voltage of said secondary battery is equal to or less than an upper limit value in the rated voltage range of said secondary battery,

wherein,

said protecting circuit receives the voltage comparison signal from said voltage comparator and controls opening or closure of each of said first switch for the discharge control FET, said second switch for the discharge control FET, said first switch for the charge control FET, and said second switch for the charge control FET so as to output the first signal to permit the discharge or to output the second signal to permit the charge by using the higher one of the output voltage of said voltage converter and the voltage of said secondary battery.

8. The battery pack according to claim 7, further comprising:

a first resistor having end terminals respectively connected to the gate terminal and a source terminal of said discharge control FET;

a first capacitor having end terminals respectively connected to the gate terminal and the source terminal of said discharge control FET;

a second resistor having end terminals respectively connected to the gate terminal and a source terminal of said charge control FET; and

a second capacitor having end terminals respectively connected to the gate terminal and the source terminal of said charge control FET.

9. The battery pack according to claim 7, further comprising:

a first resistor arranged between said second switch for the discharge control FET and an output terminal of said voltage comparator;

a second resistor arranged between said second switch for the charge control FET and the output terminal of said voltage comparator;

a third resistor having end terminals respectively connected to the gate terminal and a source terminal of said discharge control FET; and

a fourth resistor having end terminals respectively connected to the gate terminal and a source terminal of said charge control FET.