CHARGER AND METHOD OF CHARGING

• US 20080094038A1
• Filed: 10/17/2007
• Published: 04/24/2008
• Est. Priority Date: 10/23/2006
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Okada, Masami
• Granted Patent: US 7,843,173 B2
• Time in Patent Office: Days
• US Class Current: 320/163
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A charger includes input terminals whereto positive and negative voltages from a power source unit are applied, output terminals generating an output charging a secondary battery, upon being applied with the voltage from the input terminals via positive and negative power source lines, a first field effect type transistor and a second field effect type transistor having a region between a drain and a source inserted in at least one of the positive and negative power source lines, and having a first parasitic diode with a polarity reverse against charge current, and a second parasitic diode with a polarity forward direction with charge current respectively, a first detection circuit and a second detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, the first circuit is between the input terminals and the first transistor, and the second circuit is between the first transistor and the second transistor, and a charge control unit supplied with the first and second detection voltages, and generates ON/OFF control signals for the gates of the first and second transistors.

Claims

1. A charger comprising:

input terminals whereto positive and negative voltages from a power source unit are applied;

output terminals generating an output for charging a secondary battery, upon being applied with the voltage from the input terminals via positive and negative power source lines;

a first field effect type transistor having a region between a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a first parasitic diode with the reverse polarity with respect to a charge current;

a second field effect type transistor having a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a second parasitic diode with a forward polarity with respect to the charge current;

a first detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the input terminals and the first field effect type transistor, and allowing extraction of a first detection voltage from a divisional point of the resistors;

a second detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the first field effect type transistor and the second field effect type transistor, and allowing extraction of a second detection voltage from a divisional point of the resistors; and

a charge control unit which is supplied with the first and second detection voltages, and generates ON/OFF control signals for gates of the first and second field effect transistors;

wherein the charge control unit calculates a first difference voltage between the first and second detection voltages, while turning the first field effect type transistor OFF and turning the second field effect type transistor ON, and judges whether the first difference voltage has a value not turning the second parasitic diode ON;

if the first difference voltage is judged as having a value turning the second parasitic diode ON, the first and second field effect type transistors are turned ON to perform a charging operation;

whereas, if the first difference voltage is judged as having a value not turning the second parasitic diode ON, the first field effect type transistor is turned ON and the second field effect type transistor is switched OFF to calculate a second difference voltage while applying a same voltage to the first and second detection circuits; and

the end-of-charge state is detected by comparing a third difference voltage with a reference voltage, the third voltage being corrected by the second difference voltage.

2. The charger according to claim 1, wherein:

the third difference voltage is obtained by correcting the difference voltage between the first and second detection voltages with the second difference voltage, while turning the first field effect type transistor OFF and turning the second field effect type transistor ON.

3. A charger comprising:

input terminals whereto positive and negative voltages from a power source unit are applied;

output terminals generating an output charging a secondary battery, upon being applied with the voltage from the input terminals with positive and negative power source lines in between;

a first field effect type transistor having a region between a drain and a source inserted in at least one of the positive and negative power source lines, and having a first parasitic diode having the reverse polarity with respect to charge current;

a second field effect type transistor having a region between a drain and a source inserted in at least one of the positive and negative power source lines, and having a second parasitic diode having a forward polarity with respect to charge current;

a first detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the input terminal and the first field effect transistor, allowing extraction of a first detection voltage from a divisional point of the resistors;

a second detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the first field effect type transistor and the second field effect type transistor, allowing extraction of a second detection voltage from a divisional point of the resistors; and

a charge control unit which is supplied with the first and second detection voltages, and generates ON/OFF control signals for the gates of the first and second field effect type transistors;

wherein the charge control unit calculates a first difference voltage between the first and second detection voltages, while turning the first field effect type transistor OFF and turning the second field effect type transistor ON, and judges whether the first difference voltage has a value not turning the second parasitic diode ON;

if the first difference voltage is judged as having a value turning the second parasitic diode ON, the first and second field effect transistors are turned ON to perform a charging operation;

whereas, if the first difference voltage is judged as having a value not turning the second parasitic diode ON, calculation is performed on a corrected reference value in which error in the reference value for judging whether the end-of-charge state is achieved or not is corrected; and

the end-of-charge state is detected by comparing the difference voltage between the first and second detection voltages with the corrected reference voltage.

4. The charger according to claim 3, wherein:

whether the end-of-charge state is achieved or not is judged by comparing the difference voltage between the first and second detection voltages with the corrected reference voltage, while the first field effect type transistor is switched OFF, and the second field effect type transistor is turned ON.

5. A method of charging comprising:

detecting first detection voltage by applying a no-load voltage from a power source unit to a first detection circuit while turning a first field effect type transistor OFF to cut off charge current, and detecting a second detection voltage by applying an open voltage of a secondary battery on a second detection circuit while turning a second field effect type transistor ON,

calculating a first difference voltage between the first and second detection voltages, and judging whether the first difference voltage has a value not turning a second parasitic diode of the second field effect type transistor ON or not;

turning the first and second field effect type transistors ON to perform a charging operation, if the first difference voltage is judged as having a value turning the second parasitic diode ON;

turning the first field effect type transistor ON and turning the second field effect type transistor OFF while applying a same voltage to the first and second detection circuits to calculate a second difference voltage, if the first difference voltage is judged as having a value not turning the second parasitic diode ON; and

comparing a third difference voltage corrected by thus-detected second difference voltage with a reference voltage, to detect the end-of-charge state.

6. The method according to claim 5, wherein:

the third difference voltage is obtained by correcting the difference voltage between the first and second detection voltages using the second difference voltage, while turning the first field effect type transistor OFF and turning the second field effect type transistor ON.

7. A method of charging comprising:

detecting first detection voltage by applying a no-load voltage from a power source unit to a first detection circuit to cut off charge current while turning a first field effect type transistor OFF, and detecting a second detection voltage by applying an open voltage of a secondary battery on a second detection circuit while turning a second field effect type transistor ON,

calculating a first difference voltage between the first and second detection voltages, and judging whether the first difference voltage has a value not turning the second parasitic diode ON;

turning the first and second field effect type transistors ON and performing a charging operation, if the first difference voltage is judged as having a value turning the second parasitic diode ON;

performing calculation on a corrected reference value in which error in the reference value for judging whether the end-of-charge state is achieved or not is corrected, if the first difference voltage is judged as having a value not turning the second parasitic diode ON; and

comparing the difference voltage between the first and second detection voltages with the corrected reference voltage, to detect the end-of-charge state.

8. The method of charging according to claim 7, wherein:

whether the end-of-charge state is achieved or not is judged, by comparing the difference voltage between the first and second detection voltages with the corrected reference voltage, while the first field effect type transistor is switched OFF, and the second field effect type transistor is turned ON.

9. A charger comprising:

input terminals whereto positive and negative voltages from a power source unit are applied;

output terminals generating an output for charging a secondary battery, upon being applied with the voltage from the input terminals via positive and negative power source lines;

a first field effect type transistor having a region between a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a first parasitic diode with a reverse polarity with respect to a charge current;

a second field effect type transistor having a region between a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a second parasitic diode with a forward polarity with respect to the charge current;

a first detection circuit including a plurality of series-connected resistors inserted between the positive and negative power source lines, between the input terminals and the first field effect type transistor, and allowing extraction of a first detection voltage from a divisional point of the resistors;

a second detection circuit including a plurality of series-connected resistors inserted between the positive and negative power source lines, between the first field effect type transistor and the second field effect type transistor, and allowing extraction of a second detection voltage from a divisional point of the resistors; and

a charge control unit which is supplied with the first and second detection voltages, and generates an ON/OFF control signal for gates of the first and second field effect transistors;

wherein the charge control unit judges whether the charge current flows or not, while turning the first field effect type transistor ON and turning the second field effect type transistor OFF, and if the charge current is judge as flowing, charge operation is performed by turning ON both the first and second field effect type transistor;

if the charge current is judged as not flowing, a second difference voltage is calculated while a voltage is applied to the first and second detection circuits via the ON state first field effect type transistor; and

the end-of-charge state is detected by comparing a third difference voltage, the third difference voltage being corrected by a detected second difference voltage with a reference voltage.

10. The charger according to claim 9, wherein:

the third difference voltage is obtained by correcting a difference voltage between the first and the second detection voltage with the second difference voltage, while the first field effect type transistor is turned OFF and the second field effect type transistor is turned ON.

11. A charger comprising:

input terminals whereto positive and negative voltages from a power source unit are applied;

output terminals generating an output for charging a secondary battery, upon being applied with the voltage from the input terminals via positive and negative power source lines;

a first field effect type transistor having a region between a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a first parasitic diode with the reverse polarity with respect to a charge current;

a second field effect type transistor having a region between a drain and a source inserted and connected in at least one of the positive and negative power source lines, and having a second parasitic diode with a forward polarity with respect to the charge current;

a first detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the input terminals and the first field effect type transistor, and allowing extraction of a first detection voltage from a divisional point of the resistors;

a second detection circuit having series connections of a plurality of resistors inserted between the positive and negative power source lines, between the first field effect type transistor and the second field effect type transistor, and allowing extraction of a second detection voltage from a divisional point of the resistors; and

a charge control unit which is supplied with the first and second detection voltages, and generates ON/OFF control signals for gates of the first and second field effect transistors;

wherein the charge control unit judges whether the charge current flows or not, while turning the first field effect type transistor ON and turning the second field effect type transistor OFF, and performs charge operation by turning ON both the first and second field effect type transistor, if the charge current is judged as flowing;

if the charge current is judged as not flowing, a corrected reference value, which is a corrected error value of a reference value for judging whether end of charge state or not is calculated; and

the end-of-charge state is detected by comparing a difference voltage between the first and the second detection voltage with a corrected reference voltage.

12. The charger according to claim 11, wherein:

whether the end of charge state or not is judged by comparing the difference voltage between the first and the second detection voltage with the corrected reference voltage while turning OFF the first field effect type transistor and turning ON the second field effect type transistor.

13. A method of charging a charger in which:

a secondary battery is charged via a first and a second field effect type transistor connected in series, a voltage at input side of the first field effect type transistor is detected by a first detection circuit including a plurality of resistors, and a voltage at connection point between the first field effect type transistor and the second field effect type transistor is detected by a second detection circuit including a plurality of resistors;

the method of charging comprising;

judging whether a charge current flows to a secondary battery via a parasitic diode of the second field effect type transistor while turning the first field effect type transistor ON and turning the second field effect type transistor OFF,

performing charging operation to the secondary battery by turning ON both of the first and the second field effect type transistors, when the charge current is judged as flowing;

calculating a difference voltage while a voltage equal to that of the first and the second detection circuits is applied, via the ON state first field effect type transistor when the charge current is judged as not flowing; and

detecting end of the charge state by comparing a difference voltage corrected by the above difference voltage with a reference voltage.

14. The method of charging according to claim 13 wherein:

the corrected difference voltage is obtained by correcting a difference voltage between the first and the second detection voltage by the difference voltage, while the first field effect type transistor is turned OFF and the second field effect type transistor is turned ON.

15. A method of charging a charger in which:

a secondary battery is charged via a first and a second field effect type transistor connected in series, a voltage at input side of the first field effect type transistor is detected by a first detection circuit including a plurality of resistors, and a voltage at connection point between the first field effect type transistor and the second field effect type transistor is detected by a second detection circuit including a plurality of resistors;

the method of charging comprising;

judging whether a charge current flows to the secondary battery via a parasitic diode of the second field effect type transistor while turning the first field effect type transistor ON and turning the second field effect type transistor OFF,

performing charging operation to the secondary battery by turning ON both of the first and the second field effect type transistors, when the charge current is judged as flowing;

calculating a corrected reference value, which is a corrected error value of the reference value for judging end of the charge state, when the charge current is judged as not flowing; and

detecting end of the charge state by comparing a difference voltage between the first and the second detection circuits with the corrected reference voltage.

16. The method of charging according to claim 15 wherein:

whether the end of the charge state or not is judged by comparing the difference voltage between the first and the second detection voltage with the corrected reference voltage, while the first field effect type transistor is turned OFF and the second field effect type transistor is turned ON.