CHARGING DEVICE, ELECTRONIC EQUIPMENT INCLUDING SAME, AND CONTROL METHOD OF CHARGING DEVICE

• US 20110018500A1
• Filed: 07/20/2010
• Published: 01/27/2011
• Est. Priority Date: 07/21/2009
• Status: Active Grant

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: TAKAHASHI, Keisuke
• Granted Patent: US 8,754,613 B2
• Time in Patent Office: Days
• US Class Current: 320/148
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• 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: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A charging device to charge a secondary battery that includes a DC/DC circuit to generate a charging current supplied to the secondary battery, an impedance measurement circuit to measure an impedance of the secondary battery, a first control circuit to output a duty-cycle decrease signal in accordance with the measured impedance, a charging-current monitor circuit to detect the charging current outputted from the DC/DC circuit when the duty cycle of the pulses generated by the DC/DC circuit is decreased by the duty-cycle decrease signal, and, a second control circuit to compare the charging current detected by the charging-current monitor circuit and a charging-current threshold and to output to the DC/DC circuit a frequency change signal that increases a switching operation frequency in the DC/DC circuit.

Claims

1. A charging device to charge a secondary battery, the charging device comprising:

a DC/DC circuit to generate a charging current supplied to the secondary battery;

an impedance measurement circuit to measure an impedance of the secondary battery;

a first control circuit to output a duty-cycle decrease signal in accordance with the measured impedance;

a charging-current monitor circuit to detect the charging current outputted from the DC/DC circuit when the duty cycle of the pulses generated by the DC/DC circuit is decreased by the duty-cycle decrease signal; and

a second control circuit to compare the charging current detected by the charging-current monitor circuit and a charging-current threshold and to output to the DC/DC circuit a frequency change signal that increases a switching operation frequency in the DC/DC circuit.

2. The charging device according to claim 1, wherein the first control circuit compares the impedance measured by the impedance measurement circuit to a predetermined impedance threshold and outputs the duty-cycle decrease signal to the DC/DC circuit to decrease the duty cycle of pulses generated in the DC/DC circuit when the measured impedance is greater than the threshold.

3. The charging device according to claim 1, wherein the first control circuit classifies the impedance measured by the impedance measurement circuit into levels and outputs the duty-cycle decrease signal to the DC/DC circuit to reduce the duty cycle of pulses generated in the DC/DC circuit in accordance with the level of impedance.

4. The charging device according to claim 1, further comprising:

a battery-voltage detection circuit to detect a secondary battery voltage charge in the secondary battery,

wherein the charging device performs pre-charging with a predetermined first constant current when the secondary battery voltage detected by the battery-voltage detection circuit is lower than a first predetermined voltage, performs constant-current charging with a predetermined second constant current higher than the predetermined first constant current when the detected secondary battery voltage is higher than the first predetermined voltage, and performs constant-voltage charging when the detected secondary battery voltage reaches a second predetermined voltage greater than the first predetermined voltage.

5. The charging device according to claim 4, wherein the charging device stops the charging when the charging current detected by the charging-current monitor circuit becomes equal to or lower than a predetermined completion current value.

6. The charging device according to claim 5, further comprising

a third control circuit to output a pre-charging current change signal, a pre-charging a current at constant-current changing signal, and a charging completion current control signal to the DC/DC circuit.

9. An electronic device that employs the charging device according to claim 1.

7. The charging device according to claim 7, further comprising:

a fourth control circuit to output a charging stop signal during pre-charging, during constant-current charging, and a constant voltage charging, to the DC/DC circuit.

8. The charging device according to claim 7, wherein the charging device stops charging when the pre-charging time exceeds the pre-charging stop time, when the constant-current charging time exceeds the constant-current stop time, and when the constant-voltage charging time exceeds the constant-voltage charging stop time before the charging current detected by the charging-current monitor circuit becomes equal to or lower than a predetermined completion current value.

10. A method for controlling a charging device to charge a secondary battery, the method comprising:

generating a charging current supplied to the secondary battery with a DC/DC circuit;

measuring impedance of the secondary battery;

adjusting a duty cycle of pulses generated in the DC/DC circuit in accordance with the measured impedance;

detecting a charging current supplied to the secondary battery;

comparing the detected charging current and a first charging-current threshold when the duty cycle of the pulses generated in the DC/DC circuit is adjusted; and

increasing a clock frequency to switch the DC/DC circuit.

11. The method for controlling the charging device according to claim 10, further comprising:

comparing the measured impedance to a predetermined impedance threshold; and

decreasing the duty cycle of pulses generated in the DC/DC circuit when the measured impedance is greater than the threshold.

12. The method for controlling the charging device according to claim 10, further comprising:

classifying the measured impedance into levels; and

decreasing the duty cycle of pulses generated in the DC/DC circuit in accordance with the classified leveled of impedance.

13. The method for controlling the charging device according to claim 10, further comprising:

detecting a secondary battery voltage charged in the secondary battery;

performing pre-charging with a predetermined first constant current when the detected secondary battery voltage is lower than a first predetermined voltage;

charging the secondary battery with a predetermined second constant current higher than the first constant current when the detected secondary battery voltage is higher than the first predetermined voltage; and

charging the secondary battery with a constant voltage when the battery voltage of the detected secondary battery reaches a second predetermined voltage higher than the first predetermined voltage.

14. The method for controlling the charging device according to claim 13;

further comprising;

stopping the charging when the charging current detected by the charging-current monitor circuit becomes equal to or lower than a predetermined completion current value.

15. The method for controlling the charging device according to claim 14, further comprising:

changing a charging current at the pre-charging;

changing a charging current at the constant-current charging;

changing a charging current at the constant-current charging; and

setting and changing a charging completion current value.

16. The method for controlling the charging device according to claim 13, further comprising:

setting and changing a stop time of the pre-charging current;

setting and changing a stop time of the constant current charging; and

setting and changing a stop time of the constant-voltage charging.

17. The method for controlling the charging device according to claim 16, further comprising:

stopping charging when the pre-charging time is over the pre-charging stop time, when the constant-current charging time is over the constant- when the constant-voltage charging time is over the constant-voltage charging stop time current charging stop time before the charging current detected by the charging-current monitor circuit becomes equal to or lower than a predetermined completion current value.