Method and Apparatus for Controlling Selection of Batteries

1. Field of the Invention

The present invention relates to a method for controlling selection of batteries and an apparatus for realizing the same.

2. Description of the Related Art

Due to their compactness, light weight and portability, battery-driven electronic devices, such as laptop computers, are becoming popular recently. Since such devices are normally equipped with a single battery, their operation time is short. In addition, when the devices cannot operate on AC power, their operation is interrupted for battery replacement. Further, if power failure occurs during operation, data processed in the devices would be erased or it would take time to restart the operation after power recovery.

With the above in mind, there is a demand for a device which ensures battery replacement without interrupting operation of electronic devices, such as laptop computers.

Accordingly, it is an object of this invention to provide a method for controlling selection of batteries and an apparatus for realizing the same.

According to one aspect of the present invention, there is provided a method for controlling selection of a plurality of batteries for supplying power to computer system. The method includes detecting voltages of the batteries; selecting one of the batteries in accordance with the detected voltages; supplying power of the selected battery to the computer system; and alarming a power condition of the batteries in accordance with the detected voltages.

According to another aspect of this invention, there is provided an apparatus for controlling selection of a plurality of batteries for-supplying power to a computer system. The apparatus includes a plurality of batteries; switching means for switching a power supply of the batteries; detecting means for detecting voltages of the batteries; controlling means for controlling the switching means in accordance with the voltages detected by the detecting means; and alarm means for alarming a power condition of the batteries in accordance with the voltages detected by the detecting means.

FIG. 1 is a diagram of a battery switching apparatus according to the first embodiment of this invention;

FIG. 2 is a diagram of a detecting circuit of the battery switching apparatus shown in FIG. 1;

FIG. 3 is a diagram of a switch used in the battery switching apparatus shown in FIG. 1;

FIG. 4 is a timing chart of battery selection;

FIG. 5 is an operation flowchart for the battery switching apparatus shown in FIG. 1;

FIG. 6 is a diagram of a battery switching apparatus according to the second embodiment of this invention;

FIG. 7 is a diagram of a detecting circuit of the battery switching apparatus shown in FIG. 6;

FIG. 8 is an operation flowchart for the battery switching apparatus shown in FIG. 6; and

FIG. 9 is a diagram showing a remaining energy.

An embodiment of this invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the battery switching apparatus includes batteries 17 and 18 serving as power sources to operate computer system 1, selecting circuit 19 for selecting either battery 17 or 18, LEDs (Light Emitting Diodes) 3 and 4 serving to indicate consumption of energies of batteries 17 and 18, speaker 2, and drive controller 20 for controlling speaker 2 and LEDs 3 and 4.

Selecting circuit 19 has detecting circuits 11 and 12 for detecting the terminal voltages of batteries 17 and 18, switches 14 and 15 for switching the supply of power from batteries 17 and 18 to computer system 1, flip-flop circuit 13 for selecting either switch 14 or 15 in accordance with the terminal voltages detected by detecting circuits 11 and 12, DC-DC converter 16 for converting the power from batteries 17 and 18 into predetermined power. Flip-flop circuit 13 has NAND circuits 13a and 13b. Drive controller 20 has switches 9 and 10 for switching between LEDs 3 and 4 for their lighting, AND circuits 5 and 6, switch 7 for switching on or off speaker 2 for generation of an alarm such as a voice signal, and OR circuit 8 for rendering switch 7 on when one of batteries 17 and 18 is in a low battery condition. The "low battery condition" comes before the condition in which the computer system can no longer maintain the normal operation.

FIG. 2 illustrates the diagram of the detecting circuit 11. The output signal of operational amplifier 21 is determined by signals I+ and I- respectively supplied to its + and - input terminals. If the signal I+ received at the + input terminal and signal I- received at the - input terminal hold the relation of I+.gtoreq.I-, the output signal is at a high level. If I+<I-, the output signal is at a low level. A reference value for detecting the low battery voltage of battery 17 is determined by the ratio of the resistances of resistors 22 and 23 and the rated value of Zener diode 24. Transistor 25 is switched on/off by the output signal of operational amplifier 21. Resistors 26 and 27 are provided to protect detecting circuit 11. Resistor 28 is provided to maintain the output signal of detecting circuit 11 at a high level when transistor 25 is off.

If the power from battery 17 is sufficient for the system to operate, the signals received at the + and - input terminals of operational amplifier 21 hold the relation of I+.gtoreq.I-, so that the output signal of operational amplifier 21 becomes a high level. At this time, since transistor 25 is on, the output signal of detecting circuit 11 has a low level. When the power of battery 17 decreases and the relation between signals input to the + and - input terminals of operational amplifier 21 is I+<I-, the output signal of operational amplifier 21 becomes a low level. Transistor 25 is off and thus the output signal of detecting circuit 11 becomes a high level.

Detecting circuit 12 has the same configuration as detecting circuit 11, and therefore operates similarly.

FIG. 3 illustrates the diagram of switch 14 which has transistors 30 and 34 and resistors 31 to 33. Transistor 34 is turned on/off by the output signal of NAND circuit 13a of flip-flop circuit 13. Transistor 30 is turned on or off in accordance with the switching of transistor 34. If transistor 34 is off, transistor 30 is on, thus the power is supplied to computer system 1 from battery 17 through DC-DC converter 16. Switches 7, 9, 10 and 15 have the same configuration as switch 14 and thus operate similarly.

If battery 17 keeps supplying power to computer system 1 (switch 14 is on and switch 15 is off) as shown in FIG. 4, detecting circuit 11 keeps detecting the terminal voltage of battery 17. When the terminal voltage of battery 17 falls below a preset low battery voltage L1, switch 15 is on and power from battery 18 is supplied to computer system 1. When the terminal voltage of battery 18 detected by detecting circuit 12 is greater than the low battery voltage L1, switch 14 is off and the supply of the power from battery 17 is stopped (see the solid lines for the behavior of the switching voltages of switches 14 and 15 in FIG. 4). When the terminal voltage of battery 18 falls below the low battery voltage L1, switch 14 keeps switching on and switch 15 is off (see the broken lines in the same diagram). In order to inform an operator of the low battery condition, LEDs 3 and 4 blink. Therefore, it is possible to perform battery replacement before the operating voltage of the system reaches the voltage L2. The voltage L2 indicates the limit under which computer system 1 can no longer keep the proper operation.

With regard to the indication of the power condition by the LEDs, if LED 3 is not blinking, it indicates battery 17 is not used. That is, it is indicated that computer system 1 is operating on power from battery 18 or power from an external power source (not shown). When battery 17 becomes a low battery condition, LED 3 blinks, and an alarm is generated through speaker 2, indicating the low battery condition. When battery 18 becomes a low battery condition, LED 4 blinks, and an alarm is generated.

However, it is possible to generate the alarm when batteries 17 and 18 become a low power condition, by replacing OR circuit 8 for AND circuit.

Referring now to the flowchart shown in FIG. 5, the operation of the battery switching apparatus according to this invention will be described below.

In step S1, switches 14 and 15 are switched on. After the voltage V2 of battery 18 is detected in step S2, the detected voltage V2 is compared with a preset low battery voltage L1 in step S3.

If V2>L1 in step S3, switches 7 and 10 are switched off (step S5) and the process of step S6 is then executed. If V2.gtoreq.L1 in step S3, switches 7 and 10 are switched on (step S4) before the process of step S6 is executed.

The voltage V1 of battery 17 is detected in step S6. The detected voltage V1 is compared with the preset low battery voltage L1 in step 7.

If V1>L1 in step S7, switch 14 is switched on (step S8) and switch 15 is then switched off (step S9). Thereafter, the above-described operation sequence starting from step S2 is repeated. In other words, battery 17 keeps supplying its power to computer system 1 until the voltage V1 of battery 17 becomes less than or equal to the low battery voltage L1.

If V1.ltoreq.L1 in step S7, switches 7 and 9 are switched on (step S10). In the subsequent step S11, the voltage V2 of battery 18 is detected, and the detected voltage V2 is compared with the low battery voltage L1 in step 12.

If V2.ltoreq.L1 in step S12, step S4 (turning on switches 7 and 10) is executed and the operation starting from step S6 is then executed.

If V2>L1 in step S12, switches 7 and 10 are switched off (step S13) and the voltage V1 of battery 17 is detected in step S14. In the subsequent step S15, the voltage V1 of battery 17 is compared with the low battery voltage L1.

If V1>L1 in step S15, switches 7 and 9 are switched off (step S17) and step S18 is executed. If V1.ltoreq.L1 in step S15, switches 7 and 9 are turned on (step S16) before step S18 is executed.

After switch 15 is switched on (step S18), switch 14 is switched off (step S19), and the flow returns to step S11 for execution of the operational sequence following it. In other words, the supply of the power from battery 18 to computer system 1 is maintained until the voltage V2 of battery 18 becomes less than or equal to the low battery voltage L1.

Another embodiment of this invention will be described below referring to FIG. 6. In FIG. 6, the energies remaining in batteries 61 and 62 are computed by microcomputer 66, for example, TMP47C660, manufactured by TOSHIBA in Japan. Microcomputer 66 has A/D converter 66a, timer 66b and RAM 66c. Either battery 61 or 62 is selected by its associated switch 63 or 64 that is controlled by a control signal from microcomputer 66. The power from the selected battery is supplied through regulator 70 to system 65. Switches 63 and 64 are switched by supplying the control signal from microcomputer 66 to the base side of transistor 34 in the circuit shown in FIG. 3. The outputs of detecting circuits 67 and 68 which detect the consumption energy of the batteries are supplied to A/D converter 66a of microcomputer 66. Based on the outputs of detecting circuits 67 and 68, microcomputer 66 computes the remaining energies of the batteries. The computation results are displayed in display 69. Detecting circuits 67 and 68 may be realized by the circuit shown in FIG. 7 in which a terminal voltage of resistor 71 having a known resistance is input to A/D converter 66a of microcomputer 66.

Referring now to the flowchart of FIG. 8, the operation of the embodiment shown in FIG. 6 will be described. First, data representing the energies of the batteries used so far, which are stored in RAM 66c of microcomputer 66, are respectively set as C1 and C2 (step S21). Then, the status of switch 63 is checked (step S22). The following description will be given on the premise that the power of battery 61 is supplied to system 65 (i.e., switch 63 is ON). Based on the output of detecting circuit 67, microcomputer 66 computes the consumption energy from the discharge current il and the time t2, which is measured by timer 66b of microcomputer 66. The total consumption energy is acquired from the computed consumption energy (i1.times.t1) and the energy consumed so far, C1, and the resultant value is set as a new C1 (step S23). Then, the ratio of the remaining energy to the total energy, A1, is computed from the initial battery energy Q1 of the battery 61 and the total consumption energy C1 (step S24). When A1 is smaller than a predetermined value L1 (step 25), the present status is indicated as Low-Battery (step S26); this display may be done by LED's 3 and 4 or speaker 2 as shown in FIG. 1. The ratio A1 is then displayed on display 69 (step 27), for example, in terms of the remaining energy 93 or 94 with respect to the initial battery energy 91 to 92, as shown in FIG. 9.

When the power of battery 62 is supplied to system 65 (i.e., switch 63 is ON) in step 28, the processes in steps 29 to 33 are executed in the same manner as those in steps 23-27. That is, the consumption energy is computed from the discharge current i2 of the battery 62 and time t2, the total consumption energy is computed from the computed consumption energy and the energy consumed so far, C2, and is set as a new C2, and the ratio of the remaining energy to the total energy, A2, is computed from the initial battery energy Q2 and the total consumption energy C2. When A2 is smaller than a predetermined value L2, this status is indicated as Low-Battery and A2 is then displayed.

Since the battery in use can be detected by the statuses of switches 63 and 64, this battery can be indicated by, for example, blinking the area 91 and 92. The display section may be modified in such a way as to permit his battery indication only upon request from system 65.

Through the above operation, the operator can be informed of the timing for battery replacement. Therefore, the battery is replaced with a new one. Further, the batteries can be automatically switched from one to the other. Interruption of the operation of the computer system is not occurred at the time of battery replacement and thus ensures continuous operation of the system.

Although this invention has been described with the above particular embodiment, it is not restricted to this case but can be modified in various manners within the scope and spirit of the invention.

Further, although a battery-driven type computer system has been described above, this invention can also apply to other electronic devices which are driven by a battery.