Charging device having protective switching element

• US 8,013,575 B2
• Filed: 01/28/2008
• Issued: 09/06/2011
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Aradachi, Takao, Watanabe, Shinji, Funabashi, Kazuhiko
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): HERNANDEZ, MANUEL J
• Application Number:
  US12/020,968
• Publication Number:
  US 20080180065A1
• Time in Patent Office: 1,317 Days
• Field of Search: 320/152, 320/163, 320/128
• US Class Current: 320/128
• CPC Class Codes: H02J 2207/10 Control circuit supply, e.g. means for supplying power to the control circuit
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

To prevent a battery pack from being over-discharged even under a state that the battery pack (a secondary battery) is connected to a discharging device that is not connected to an ac input power source for a long time. A charging device has a pair of output lines and an anode terminal and a cathode terminal of a secondary battery electrically connected between the output lines to carry out a charging operation. In the charging device including a component circuit part electrically connected by traversing a part between the pair of output lines, a switching element is inserted between the component circuit part and one of the pair of output lines. When the charging device is not connected to an input power source, the switching element is allowed to be non-conductive to interrupt a discharging path so that the component circuit part does not form the discharging path.

Claims

1. A charging device having a protective switching element, the charging device comprising:

a pair of input power terminals to be connected to an AC power source;

a charging power circuit for producing a charging voltage to be applied to a battery;

a pair of output lines for supplying the charging voltage to the battery;

a component circuit part of the charging device connected by traversing a part between the pair of output lines;

a first switching element having a first terminal connected to one of the output lines and a second terminal connected to the component circuit part, the component circuit part being connected between the second terminal of the first switching element and the other of the output lines;

a second switching element connected across the battery to control on-off state of the first switching element;

a DC voltage power circuit for producing a DC voltage when the AC power source is connected to the pair of input power terminals, the DC voltage being applied to the second switching element to control on-off state of the first switching element, wherein;

both the first and second switching elements are turned ON when the AC power source is connected and are turned OFF when the AC power source is disconnected, and

the first switching element is turned ON and OFF regardless of a magnitude of a battery voltage.

2. A charging device according to claim 1, wherein the first switching element is connected in series to the component circuit part so that the first switching element is changed from a conductive state to a non-conductive state when the input power terminals are not connected to the AC power source.

3. A charging device according to claim 2, wherein the component circuit part of the charging device is a discharging resistance circuit including a resistance element and the first switching element is connected in series to the discharging resistance circuit.

4. A charging device according to claim 2, wherein the component circuit part of the charging device is composed of a plurality of series resistance circuits connected in series and the first switching element is connected in series to the series resistance circuits.

5. A charging device according to claim 1, wherein the charging power circuit including a smoothing circuit having a capacitor and resistor, the resistor being connected between the second terminal of the first switching element and the other of the output lines.

6. A charging device according to claim 5, wherein the component circuit part of the charging device is a discharging resistance circuit including a resistance element and the first switching element is connected in series to the discharging resistance circuit.

7. A charging device according to claim 5, wherein the component circuit part of the charging device is composed of a plurality of series resistance circuits connected in series and the first switching element is connected in series to the series resistance circuits.

8. A charging device according to claim 1, wherein the charging voltage control circuit includes a shunt regulator for controlling the charging voltage, the shunt regulator being connected between the second terminal of the first switching element and the other of the output lines.

9. A charging device according to claim 8, wherein the component circuit part of the charging device is composed of a plurality of series resistance circuits connected in series and the first switching element is connected in series to the series resistance circuits.

10. A charging device according to claim 1, wherein the first switching element is formed with a semiconductor switching element.

11. A charging device according to claim 1, further comprising:

a rectifying and smoothing circuit for rectifying and smoothing the AC voltage of the AC power source; and

a switching circuit for switching an output voltage of the rectifying and smoothing circuit to produce a high frequency AC voltage, wherein the high frequency AC voltage is rectified and smoothed to produce a DC voltage which is supplied to the battery.

12. A charging device according to claim 1, further comprising:

a primary side rectifying and smoothing circuit;

a switching circuit having a high frequency transformer; and

a secondary side rectifying and smoothing circuit.

13. A charging device according to claim 12, wherein the primary side rectifying and smoothing circuit includes a full-wave rectifying circuit and a smoothing capacitor and is electrically connected to an AC power source through a pair of input power terminals to full-wave rectify the AC power source.

14. A charging device according to claim 13, wherein the switching circuit, having the high frequency transformer, further includes a MOSFET connected in series to a primary winding of the transformer and a PWMIC for modulating a pulse width of a driving pulse signal applied to a gate electrode of the MOSFET.

15. A charging device according to claim 1, wherein the battery to be charged comprises:

a heat sensitive element for detecting a temperature of the battery and outputting a signal based on the detection, and

a protecting circuit for monitoring a voltage of each battery cell and outputting a signal when an over-charge or an over-discharge condition exists in the battery,

wherein the charging device further comprises;

a battery voltage detecting circuit for detecting a voltage of the battery and outputting a signal based on the detection.

16. A charging device according to claim 15, further comprising:

a control circuit device which determines the temperature of the battery based on the signal output by the heat sensitive element, determines the voltage of the battery based on the signal output by the battery voltage detecting circuit and outputs a control signal to the charging device based on the determinations.

17. A charging device comprising:

a pair of input power terminals to be connected to an AC power source;

a charging power circuit for producing a charging voltage to be applied to a battery;

a pair of output lines for supplying the charging voltage to the battery;

a charging voltage control circuit including a charging voltage setting circuit having a first resistor and a second resistor connected in series to set the charging voltage;

a battery voltage detecting circuit including a third resistor and a fourth resistor connected in series to detect the battery voltage;

a discharge preventing circuit including a first switching element having a first terminal connected to one of the output lines and a second terminal, and a second switching element connected across the battery to control on-off state of the first switching element, wherein a first series circuit including the first and the second resistors and a second series circuit including the third and the fourth resistors are connected in parallel between the second terminal of the first switching element and the other of the output lines; and

a DC voltage power circuit for producing a DC voltage when the AC power source is connected to the pair of input power terminals, the DC voltage being applied to the second switching element to control on-off state of the first switching element, wherein;

both the first and second switching elements are turned ON when the AC power source is connected and are turned OFF when the AC power source is disconnected, and

the first switching element is turned ON and OFF regardless of a magnitude of a battery voltage.

18. A charging device according to claim 17, wherein the charging power circuit including a smoothing circuit having a capacitor and a fifth resistor, the fifth resistor being connected between the second terminal of the first switching element and the other of the output lines.

19. A charging device according to claim 17, wherein the charging voltage control circuit includes a shunt regulator for controlling the charging voltage, the shunt regulator being connected between the second terminal of the first switching element and the other of the output lines.

20. A charging device according to claim 17, wherein the first switching element is formed with a semiconductor switching element.

21. A charging device according to claim 17, further comprising:

a rectifying and smoothing circuit for rectifying and smoothing the AC voltage of the AC power source; and

a switching circuit for switching an output voltage of the rectifying and smoothing circuit to produce a high frequency AC voltage, wherein the high frequency AC voltage is rectified and smoothed to produce a DC voltage which is supplied to the battery.