BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram showing a battery charger which has previously been applied by the assignee of the present invention;
FIG. 2 is a perspective view of the battery charger in accordance with an embodiment of the present invention;
FIG. 3 is a partial, cross sectional, perspective view of the battery charger as shown in FIG. 2;
FIG. 4 is a perspective view of the battery charger in accordance with an alternative embodiment of the present invention;
FIG. 5 is a partial, cross sectional, perspective view of the battery charger shown in FIG. 4;
FIG. 6 is a bottom perspective view of the battery charger shown in FIG. 4;
FIG. 7 is a partial, cross sectional, perspective view of the battery charger shown in FIG. 6;
FIG. 8 is a block diagram showing the battery charger in accordance with an embodiment of the present invention;
FIG. 9 is a block diagram showing the battery charger in accordance with an alternative embodiment of the present invention;
FIG. 10 is a block diagram showing the battery charger in accordance with another embodiment of the present invention;
FIG. 11 is a view showing a first operative state of the battery charger shown in FIG. 8;
FIG. 12 is a view showing a second operative state of the battery charger shown in FIG. 8;
FIG. 13 is a view showing a third operative state of the battery charger shown in FIG. 8;
FIG. 14 is a view showing a fourth operative state of the battery charger shown in FIG. 8; and
FIG. 15 is a view showing a fifth operative state of the battery charger shown in FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
A battery charger shown in FIG. 2 through FIG. 7 has a casing 21, 31 provided with an electronic device incorporated with an external battery, or with a mounting portion 22, 32 to which an external battery 1 is detachably mounted. The casing 21, 31 is incorporated with an internal secondary battery 3 for charging the external battery 1. The illustrated internal secondary battery 3 is a lithium-ion secondary battery. It should be noted, however, the inventive battery charger is not limited to a lithium-ion secondary battery as an internal secondary battery. The internal secondary battery may be any other rechargeable kind of batteries such as a nickel-hydrogen battery and nickel-cadmium battery. The illustrated battery charger is also provided with a power plug 23, 33 which is connected to a plug socket from a commercial power supply for charging the external battery 1 and the internal secondary battery 3.
In the battery charger shown in FIGS. 2 and 3, a mounting portion 22 for detachably mounting a mobile electronic device (not shown) such as a mobile phone is provided on the upper face of the casing 21. In a state where the mobile electronic device is mounted to the mounting portion 22, the battery charger serves to charge either an external battery which is a secondary battery built in a mobile electronic device, or an external battery which is a secondary battery incorporated in a battery pack which is detachably mounted to the mobile electronic device. In the battery charger shown in FIG. 4 through FIG. 7 as well, a mounting portion 32 for detachably mounting an AA size secondary battery is provided on the top surface. The battery charger charges the external battery 1 which is a secondary battery mounted to the mounting portion 32. Further, although not shown, the battery charger can also mount a battery pack, detachably mounted to the mounting portion, on a device such as a mobile electronic device, so that the external battery can also be charged which is a secondary battery built in the battery pack.
In these battery chargers, the external battery 1 directly or indirectly mounted to the mounting portion 22, 32 is charged by means of input power from a commercial power supply as well as by means of the internal secondary battery 3 which is built in the casing 21, 31. In particular, when the commercial power supply is not input, namely, when input power is not in an inputted state, the external battery 1 is charged by means of the internal secondary battery 3. The external battery 1 which is mounted to the mounting portion 22, 32 to be charged is a lithium-ion secondary battery. However, the external battery may also be a rechargeable secondary battery such a nickel-hydrogen battery and a nickel-cadmium battery.
Shown in FIG. 8 is a block diagram of the battery charger shown in these drawings. The battery charger shown in the block diagram includes a first charging circuit 2 for charging the detachably mounted external battery 1; an internal secondary battery 3 which is charged by the input power; a charge/discharge control circuit 4 for charging the internal secondary battery 3 by means of the input power as well as for controlling the charge of the internal secondary battery 3; and a control circuit 5 for controlling the operative state of the first charging circuit 2 and the charge/discharge control circuit 4. Further, the battery charger includes a main power source circuit 6 for outputting a DC voltage for charging the external battery 1. In the illustrated battery charger, since the input power is from the commercial power supply 10, the main power source circuit 6 is set to be a circuit for converting the AC 100 V from the commercial power supply 10 to the DC voltage. However, the inventive battery charger does not necessarily have to utilize a commercial power supply input power. As will be described later in detail, it is also possible to provide a main power source circuit for supplying DC input power. The illustrated battery charger is also provided with a DC-DC converter 7 for converting the output voltage from the internal secondary battery 3. Further, the first charging circuit 2 is provided with a sub DC-DC converter 8 for converting the output voltage from the external battery 1 to the charging voltage from the internal secondary battery 3, as well as with a sub charging circuit 9 for controlling the state where the external battery 1 charges the internal secondary battery 3.
The first charging circuit 2 controls the charge of the external battery 1, and stops the charging operation when the external battery 1 becomes fully charged. The first charging circuit 2 charges the external battery 1 by controlling both the input power which is inputted from the main power source circuit 6 and the electric power outputted from the internal secondary battery. In a state where the electric power is inputted from the commercial power supply 10, the first charging circuit 2 charges the external battery 1 by means of the output power from the main electric power source circuit 6. At this state, when the internal secondary battery 3 has still a residual capacity for charging the external battery 1, the control circuit 5 charges the external battery 1 by the electric power both from the main electric power source circuit 6 and the internal secondary battery 3. Further when the power plug is unplugged from a plug socket, or when the commercial power supply 10 fails, for not supplying the electric power, the control circuit 5 starts to charge the external battery 1 by using the internal secondary battery 3. However, when the residual capacity of the internal secondary battery 3 reaches a capacity that is unable to charge the external battery 1, in other words, when the internal secondary battery 3 is in a completely discharged state, the control circuit 5 does not charge the external battery 1 from the internal secondary battery 3. In this state, the external battery 1 is charged only by means of the output power from the main electric power source circuit 6.
The lithium-ion secondary battery as the internal secondary battery 3, being built in a casing of the battery charger, is charged either by the input power or by the external battery 1. The lithium-ion secondary battery charged by the input power is fully charged by the charge/discharge control circuit 4. The lithium-ion secondary battery is charged at a constant current to reach a set voltage, and subsequently is charged at a constant voltage to become fully charged. When charged at a constant voltage, the charging current decreases while reaching a full charge. Therefore, when the charging current becomes smaller than a set current, it is judged that the lithium-ion secondary battery has reached a full charge and the charge is stopped. Since the lithium-ion secondary battery is fully charged by charging at a constant voltage, a longer time is needed for a full charge when compared with a battery that is fully charged at a constant current like in a nickel-hydrogen battery or nickel-cadmium battery. However, the lithium-ion secondary battery built in the battery charger cannot be disadvantageous in that the charging time is longer. This is because the lithium-ion secondary battery is charged in a state where the battery charger is connected to the commercial power supply 10. Further, the lithium-ion secondary battery is smaller in its self discharge when compared with the nickel-hydrogen battery and nickel-cadmium battery. For this reason, after the lithium-ion secondary battery has been fully charged by means of the input power, the lithium-ion secondary battery is maintained at a fully charged state for a longer period of time, even when the commercial power supply 10 is not inputted. The lithium-ion secondary battery at its full charge can increase the charging capacity of the external battery 1.
The charge/discharge control circuit 4 controls the charge of the lithium-ion secondary battery which is an internal secondary battery 3, and stops the charging operation when over-charged. Further, the charge/discharge control circuit 4 continues to charge the lithium-ion secondary battery at a constant current until the battery voltage reaches a set voltage, and subsequently, fully charges at a constant voltage. When the lithium-ion secondary battery is fully charged, the charging operation stops. Further, the charge/discharge control circuit 4 controls the state of charging the lithium-ion secondary battery which is the internal secondary battery 3, in other words, controls the state where the lithium-ion secondary battery charges the external battery 1. This is for the purpose of preventing the lithium-ion secondary battery from being over-discharged. The charge/discharge control circuit 4 continues to charge the external battery 1 by discharging the residual capacity of the lithium-ion secondary battery until its capacity reaches zero. When the lithium-ion secondary battery has no residual capacity, the charging operation is stopped to prevent the lithium-ion secondary battery from being over-discharged.
In the above-described battery charger, the input power is from the commercial power supply 10, the power supplied from which is converted by the main power source circuit 6 to the DC voltage for charging the external battery 1 so as to be supplied to the charge/discharge control circuit 4. However, as shown in FIG. 9, the inventive battery charger can also be provided with the AC adaptor 40 to serve as a main electric power source circuit for outputting a DC voltage for charging the external battery 1. The battery charger supplies to the charge/discharge control circuit 4 the DC power which is supplied from the AC adaptor 40. Since the battery charger does not have to be provided with a circuit for converting the commercial power supply to the DC voltage for charging the external battery 1, the circuit structure can be advantageously simplified, with a smaller size of battery charger.
Further, the battery charger shown in FIG. 10 is provided with a solar battery 50 which serves as a main power source circuit for outputting a DC voltage for charging the external battery 1. The solar battery 50, although not shown, is disposed in the casing of the battery charger and supplies the DC power to the charge/discharge control circuit 4. However, when the residual capacity of the external battery is less than the set capacity, and when the power capacity by the solar battery is larger than the set capacity, the external battery can also be charged directly by the input power from the solar battery.
As described above, the battery charger to which the electric power is supplied from the solar battery 50 preferably incorporates the lithium-ion secondary battery as an internal secondary battery 3. The battery charger carries the following advantages when compared with the structure of incorporating the nickel-hydrogen battery or nickel-cadmium battery as an internal secondary battery. When the nickel-hydrogen battery or nickel-cadmium battery is used as an internal second battery, the charging efficiency decreases in a case of the charging current value being less than 1/20 C. The lithium-ion secondary battery, on the other hand, does not undergo such a decrease in charging efficiency. Therefore, in the case of a solar battery being used as a power supply source, even when a less sufficient current is available due to a cloudy weather, the lithium-ion secondary battery can be charged efficiently without any decrease in the charging efficiency.
In the case of a battery charger where the output power from the solar battery 50 is used input power and also where the lithium-ion secondary battery is used as an internal secondary battery, during the period of using the external battery 1 (for example, for three to seven days), the lithium-ion secondary battery as an internal secondary battery 3 is electrically charged to store electric power, and during the period of the external battery 1 being charged by the charged internal secondary battery 3, the charging operation can be performed within a shortest period (for about five hours). In the case of nickel-hydrogen battery, on the other hand, the charging efficiency is decreased at a low rate (less than 1/20 C) and a charging operation is impossible when the electromotive force is not sufficient. Further, when the nickel-hydrogen battery is directly charged by a solar battery, the charging current is found to be less uniform and discontinuous, so that it becomes problematic that a full charge cannot be detected. This is because the nickel-hydrogen battery is charged at a lower current and the charging operation is stopped by detecting a variation of voltage (detection of −ΔV (a voltage drop)) to detect the full charge. Instead, the lithium-ion secondary battery is charged at a lower voltage, without having to detect a full charge, so that the charging operation can be securely made even from a solar battery with an unstable current value. Further, it is also possible to add another function such as charging a mobile phone by using the lithium-ion secondary battery. As described above, in the case of a battery charger where a solar battery with unstable output power is used input power, the structure of using the lithium-ion secondary battery as an internal secondary battery is found extremely effective and advantageous in that the charging efficiency is not decreased, ensuring an efficient charging operation.
In the battery charger as embodied above, the control circuit 5 controls the operative state of the first charging circuit 2 and the charge/discharge control circuit 4. FIG. 11 through FIG. 15 show the state how the control circuit 5 controls the first charging circuit 2 and the charge/discharge control circuit 4. However, the operative state depicted below shows the state of controlling the battery charger shown in FIG. 8. Here, in each drawing, the dotted line depicts the electrical connection line which is not in use.
First Operative State
FIG. 11 shows the state where the commercial power supply 10 is inputted, which is the state where the first charging circuit 2 is charging the external battery 1 by means of the output power from the main electric power source circuit 6. This state shows the state the external battery 1 is charged when the residual capacity is small in the lithium-ion secondary battery as the internal secondary battery 3. The control circuit 5 detects the residual capacity of the internal secondary battery 3, and when the residual capacity of the internal secondary battery 3 is smaller than the set capacity, the first charging circuit 2 alone is made operative, instead of the charge/discharge control circuit 4 being made operative. The inoperative charge/discharge control circuit 4 does not charge the external battery 1 by means of the internal secondary battery 3, while the operative first charging circuit 2 charges the external battery 1 by means of the electric power supplied from the main electric power source circuit 6.
Second Operative State
In FIG. 12, the internal secondary battery 3 is charged by means of the commercial power supply 10. That is, the lithium-ion secondary battery as the internal secondary battery 3 is charged by means of the electric power from the main electric power source circuit 6. This state is the state where the battery charger is connected to the commercial power supply 10 and the external battery 1 is not mounted to the battery charger, or the state the external battery 1 is fully charged. The control circuit 5 detects the residual capacity of the internal secondary battery 3, and when the internal secondary battery 3 is not fully charged, the external battery 1 is detected not to have been charged, so that the charge/discharge control circuit 4 is made operative to charge the internal secondary battery by means of the electric power from the main electric power source circuit 6. When the internal secondary battery 3 is fully charged, the charge/discharge control circuit 4 stops the charging operation of the internal secondary battery 3. In such a state, the internal secondary battery 3 is fully charged.
Third Operative State
FIG. 13 shows the state where the external battery 1 is charged by the commercial power supply 10 as well as by the internal secondary battery 3. The state is the state where the battery charger is connected to the commercial power supply 10 for the electric power to be inputted from the commercial power supply 10, and the internal secondary battery 3 is charged up to the capacity that can be charged to the external battery 1. The control circuit 5 detects that the commercial power supply 10 is inputted and also detects that the residual capacity of the internal secondary battery 3 is larger than the capacity (the set capacity as described above) which can be charged to the external battery 1, so that the first charging circuit 2 and the charge/discharge control circuit 4 are made operative. The first charging circuit 2 in its operative state charges the external battery 1 by means of the output power from the main electric power source circuit 6. Further, the charge/discharge control circuit 4 in its operative state charges the internal secondary battery 3, and supplies the discharge energy of the internal secondary battery 3 to the external battery 1 to charge the external battery 1. AT this state, the control circuit 5 also makes the DC-DC converter 7 operative, which is connected to the output side of the internal secondary battery 3, and thus the DC-DC converter 7 converts the output voltage from the internal secondary battery 3 to a voltage for charging the external battery 1, so that the external battery 1 is charged. This operative state can also be controlled by using the charge switch 11 provided to the charge/discharge control circuit 4. The charge/discharge control circuit 4 detects that the charge switch 11 is pushed so as to discharge the internal secondary battery 3 and to charge the external battery 1. The charge switch 11, for example, as a turbo-charge switch, charges the external battery 1 in a quicker time by means of the output power from the internal secondary battery 3 in addition to the main electric power source circuit 6. The charge/discharge control circuit without being provided with a charge switch detects that the internal secondary battery has a residual capacity that can charge the external battery, so that the external battery is charged.
Fourth Operative State
FIG. 14 shows the state when the battery charger is not connected to the commercial power supply 10, the internal secondary battery 3 charges the external battery 1. In the control circuit 5, when the commercial power supply 10 is not detected not to be inputted, and when the residual capacity of the internal secondary battery 3 is larger than the capacity that the external battery 1 can be charged, the first charging circuit 2 and the charge/discharge control circuit 4 are made operative instead of making the main electric power source circuit 6 operative, and thus the external battery 1 is charged by the internal secondary battery 3. At this state, the control circuit 5 also makes the DC-DC converter 7 operative and used the DC-DC converter 7 to convert the output voltage from the internal second battery 3 to the charging voltage of the external battery 1, so that the external battery 1 is charged. In this state, when the external battery 1 is fully charged, the control circuit 5 stops the charging operation of the external battery 1. In the state as shown in FIG. 14, for example, when the battery charger is connected to the commercial power supply 10, and the external battery 1 is being charged by the commercial power supply 10 as well as by the internal secondary battery 3, there occurs that the battery charger is unplugged from the commercial power supply 10. Even if unplugged from the commercial power supply 10, the battery charger, which allows the internal secondary battery 3 to continue to charge the external battery 1, is able to continue to charge the external battery 1; even when the battery charger to which the external battery 1 is mounted, without being fully charged, is carried away from the commercial power supply 10, the external battery 1 can continue to be charged Such a state is conveniently utilized when there is not much time for charging the external battery 1 and the battery charger has to be carried away.
Fifth Operative State
FIG. 15 shows the state where the internal secondary battery 3 is charged by the external battery 1. The control circuit 5 detects that the external battery 1 has a residual capacity of charging the lithium-ion secondary battery which is the internal secondary battery 3 and also detects that the internal secondary battery 3 is not fully charged, and thus the internal secondary battery 3 is charged by the external battery 1. In the case of the battery charger which charges the internal secondary battery 3 by the external battery 1, the first charging circuit 2 is provided with a sub charging circuit 9 for charging the lithium-ion secondary battery which is the internal secondary battery 3. Further, a sub DC-DC converter 8 is also provided for converting the output voltage from the external battery 1 to the output voltage from the lithium-ion secondary battery which is the internal secondary battery 3. Since the battery charger is to be used for charging the external battery 1, the sub charging circuit 9 is provided with a discharge switch 12 which permits the external battery 1 to be charged, and when the discharge switch 12 is detected to have been operated, the internal secondary battery 3 is charged by the external battery 1. A user of the battery charger operates the discharge switch 12 when the external battery 1 need not be used, and thus the internal battery 3 is charged by the external battery 1.
It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the spirit and scope of the invention as defined in the appended claims.
The present application is based on Application No. 2006-219015 filed in Japan on Aug. 10, 2006, the content of which is incorporated herein by reference.
Patent Application
20080036417
