GB2292051A

GB2292051A - Controlling battery charging in a mobile telephone in dependence on communication mode

Info

Publication number: GB2292051A
Application number: GB9515456A
Authority: GB
Inventors: Hideton Ikeda
Original assignee: Oki Electric Industry Co Ltd
Current assignee: Oki Electric Industry Co Ltd
Priority date: 1994-07-28
Filing date: 1995-07-27
Publication date: 1996-02-07
Also published as: ITMI951614A0; ITMI951614A1; IT1277341B1; GB9515456D0; JPH0846562A; CA2154857A1

Abstract

A battery 14 in a cordless handset 11 of a mobile telephone in a vehicle can be charged from the vehicle battery when the handset is placed in a cradle 30, but charging, or at least rapid charging, is inhibited in response to the handset switching from a stand-by mode to an active communication mode so that telephone operation is not then adversely influenced by noise or heat from the charger 7. On switching to the active mode, a CPU 12 in the handset may output a signal which results in turn-off of a transistor 3 at the power supply input of the charger 7. The transistor 3 may alternatively be at the charging output of the charger. In another alternative (Fig. 3), the signal from the handset CPU 12 is sent to a CPU (23) in the charger to control a transistor disposed within the charger between its power input and charging output. The charger CPU (23) may also control charging in response to battery voltage or temperature, time, charging current falling below a certain level, and/or any abnormality in the telephone. If the charger can deliver rapid charging and trickle charging current levels, only rapid charging may be inhibited in the active communication mode, or both rapid and trickle charging may be inhibited. <IMAGE>

Description

MOBILE TELEPHONE BACKGROUND OF THE INVENTION The present invention relates to a mobile telephone (telephone for use in an automobile), and in particular to a battery charging circuit which is accessory to the telephone.

The battery charging circuit of this type has a function of stopping charging, either by detection of the full charge on the basis of the voltage on the battery, or by setting a timer and detecting elapse of time, or by detection of the temperature of the battery, or by monitoring the charging current and detecting that the current is reduced below a certain value.

The above-mentioned function is to stop charging when the battery is fully charged, or to stop charging for the purpose of protection to prevent fault, when for some reason the battery is abnormal during charging, and there has not been any measure to prevent thermal influence from the battery charging circuit during charging, or influence due to noise from the battery charging circuit on the telephone handset during charging.

Such thermal influence or noise from the battery charging circuit is problematical when the battery is rapidly charged.

SUMMARY OF THE INVENTION An object of the invention is to eliminate thermal influence from the battery charging circuit during charging, or influence due to noise from the battery charging circuit on the telephone handset during charging.

According to one aspect of the invention, there is provided a mobile telephone comprising: a telephone handset (11) having a battery (14) provided therein, said telephone handset activating a communication signal (Sc) when it is operating for communication; a power supply terminal (6); a battery charging circuit (7) connected between the power supply terminal (6) and said battery (14) for performing charging of said battery (14); and a charging prohibiting means (2) for prohibiting the charging by said battery charging circuit (7) when the communication signal (Sc) is active.

With the above arrangement, when the communication signal is activated, the charging control means interrupts the charging current flowing from the power supply terminal to the battery through the battery charging circuit, to thereby stop charging of the battery. Accordingly, the thermal noises from the battery charging circuit during communication can be prevented. An attendant effect is that the requirements on the battery charging circuit and the adapter unit can be relaxed, so that the cost of the telephone can be lowered.

When the telephone handset is returned to the stand-by state, and the communication signal is turned inactive, then the connection between the power supply terminal and the battery via the battery charging circuit is restored, and charging of the battery is resumed.

Accordingly, the telephone handset can be used without problems even if stand-by and communication are alternately repeated.

According to another aspect of the invention, there is provided a mobile telephone comprising: a telephone handset (11) having a battery (14) provided therein, said telephone handset activating a communication signal (Sc) when it is operating for communication; a power supply terminal (6); and a battery charging circuit (17) connected between the power supply terminal (6) and said battery (14) for performing charging of said battery (14); wherein said battery charging means comprises a switching element (18) connected between said power supply terminal (6) and said battery (14), and charging control means (22) for turning off said switching element (18) to disable said charging when said communication signal (Sc) is activated.

With the above arrangement, when the communication signal is activated, the charging control means turns off the switching element to stop charging of the battery. When the communication signal is turned inactive, the switching element is turned on and the charging of the battery is resumed. These operations can be achieved without altering the hardware configuration. As a result, the cost of the telephone can be further lowered.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing interconnection of the telephone and its accessories.

FIG. 2 is a circuit diagram showing a first embodiment of the invention.

FIG. 3 is a circuit diagram showing a second embodiment of the invention.

FIG. 4 is a flow chart for explaining the operation of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a perspective view showing how a mobile telephone and its accessories are connected. The telephone set comprises a handset 11, and a cradle 30 on which the handset 11 is mounted, and an adapter unit 1 usually fixed to the automobile. The adapter unit 1 is connectable through connectors in the cradle 30 with a vehicle battery or power supply section of the automobile 32. The illustrated example of the handset 11 is of a portable or cordless type, and has contact pads, including pads 9a and 13a. The cradle 30 has corresponding contact pads, including pads 9b and 13b. When the handset 11 is mounted on the cradle 30, the pads 9a, 13a and the like are in contact with the respectively corresponding pads 9b, 13b and the like.

The pads 9a and 9b are for conducting a charging current.

The pads 13a and 13b are for transmitting a communication signal Sc used for control over the charging. Other pads are used for other purposes, not directly related to the feature of the invention.

The cradle 30 is provided with a microphone, not specifically illustrated, for hands-free communication, and is connected to a booster amplifier 34, and an antenna 36.

FIG. 2 is a diagram showing a pertinent part of the telephone relating to the feature of a first embodiment of the invention. The circuit internal to the telephone handset 11, and the adapter unit 1. The cradle 30 is shown schematically as comprising the pads 9b and 13b and conductors connecting the pads to the adapter unit 1. The adapter unit 1 comprises a battery charging circuit 7, and a charging prohibiting circuit 2.

An output terminal 7b of the battery charging circuit 7 is connected via charging contact pads 9a and 9b to the battery 14 in the telephone handset 11.

The charging prohibiting circuit 2 comprises switching transistors 3 and 4, and an inverter 5. The transistor 3 is a PNP transistor, for example, and its emitter is connected to a power supply terminal 6, its collector is connected to an input terminal 7a of the battery charging circuit 7 and its base is connected to the collector of the transistor 4.

The transistor 4 is an NPN transistor, for example, and its base is connected to the output terminal of the inverter 5, and its emitter is connected to the ground. The input of the inverter 5 is connected to the output port 13 of the CPU 12 provided in the telephone handset 11. The power supply terminal 6 is connected to the vehicle battery 32 through the connectors in the cradle 30.

The telephone handset 11 comprises a CPU 12 controlling various circuits in the handset, the battery 14, and the like. When the telephone 11 operates for communication, the CPU 12 activates a communication signal Sc indicating that the telephone is communicating, via the pad 13a. For instance, one of the communication confirmation signal, radio transmitter operation confirmation signal, and radio transmitter power driver signal is output. As an alternative, the radio transmitter driver power supply, which is turned on when the communication is started, may be used as the communication signal Sc. The communication signal is supplied via the pads 13a and 13b to the inverter 5.

The operation will next be described with reference to the drawing. It is assumed that the handset 11 is kept mounted on the cradle, so that the pads 9a, 13a, and the like on the handset 11 are in contact with the pads 9b, 13b and the like on the cradle 30, and the communication is made in a hands-free way. When the telephone handset 11 is in a stand-by state, the CPU 12 does not activate the communication signal Sc, so that the output of the inverter 5 is active or high, and the transistor 4 is on, and the transistor 3 is therefore on. As a result, the battery charging circuit 7 receives the voltage applied to the power supply terminal 6 via the transistor 3, and is in the state in which it can charge the battery 14.The battery charging circuit 7 makes judgment on whether to conduct charging on the basis of results of detection of, for instance, the voltage on the battery, the charging current, the length of time elapsed after the start of charging, or the temperature of the battery, and/or any abnormality present in the telephone, or in other words of the detection of whether the battery is fully charged or not.

When the telephone handset 11 is changed from the stand-by state to the communication state, and the CPU 12 activates the communication signal Sc, the output of the inverter 5 is changed from high to low, and the transistor 4 is turned off. The transistor 3 is also turned off, so that the supply of the voltage to the battery charging circuit 7 is stopped.

When the telephone handset 11 is returned from the communication state to the stand-by state, the output of the inverter 5 is changed from low to high, and the transistor 4 is turned on and the transistor 3 is turned on. Then, the battery charging circuit 7 receives the voltage applied to the power supply terminal 6 via the transistor 3, and is again in a state capable of charging the battery 14.

As has been described, according to this embodiment, when the telephone handset 11 operates for communication, the inverter 5 turns off the transistors 3 and 4, and stops the charging to the battery 14. As a result, the influence of noise from the battery charging circuit 7 during communication is eliminated, and the thermal influence from the battery charging circuit 7 is also restrained.

Moreover, the requirements on the automobile adapter unit 1 can be relaxed, so that it is possible to provide a telephone at a lower price.

In the embodiment described, the transistor 3 is interposed between the power supply terminal 6 and the battery charging circuit 7. However, the transistor 3 may alternatively be disposed between the battery charging circuit 7 and the charging terminal 9.

Embodiment 2 FIG. 3 is a circuit diagram showing another embodiment of the invention, and FIG. 4 is a flowchart for explaining the operation of the embodiment. Members or parts identical to those of the first embodiment described with reference to FIG. 2 are designated by identical reference numerals and their description is omitted.

In place of the battery charging circuit 7 in FIG. 2, a battery charging circuit 17 is provided.

As illustrated in FIG. 3, the battery charging circuit 17 comprises switching transistors 18 and 19, and a one-chip microcomputer 22 having a CPU 23 and a memory 24. The transistor 18 is a PNP transistor, for example, and its emitter is connected to the power supply terminal 6, its collector is connected to the charging terminal 9, and its base is connected to the collector of the transistor 19.

The transistor 19 is an NPN transistor, for example, and its base is connected to an output port 26 of the CPU 23, and its emitter is connected to the ground. An input port 25 of the CPU 23 is connected to the output port 13 of the CPU 12 provided in the telephone handset 11. The CPU 23 operates in accordance with computer programs stored in the memory 24.

It is to be noted that the battery charging circuit 7 shown in FIG. 2 is generally similar to the battery charging circuit 17 shown in FIG. 3, except that the battery charging circuit 17 has additional functions as is described below.

That is, the charging prohibiting circuit 2 in FIG. 2 is not used in this embodiment, but instead, a corresponding function is implemented by the one-chip microcomputer 22 which is already provided in the battery charging circuit for the purpose of controlling charging on the detection of full charge of the battery, the detection being made on the basis of the voltage, current, and/or temperature of the battery, and/or the charging time.

Like Embodiment 1, the CPU 12 activates the communication signal Sc when the telephone handset 11 operates for communication.

The operation will next be described with reference to the flow chart of FIG. 4 illustrating the operation of the microcomputer 22 including the CPU 23. At a step S1, judgment is made as to whether a communication signal Sc is active. When the telephone handset 11 is in a stand-by state, the communication signal Sc from the CPU 12 is inactive, so that, at the step S1, a step 2 is selected, and where judgment of whether the charging should be made on the basis of other conditions such as whether the battery is fully charged or not. If the step S2 finds that the charging should be made, the step S4 is selected, where the signal at the output port 26 is made high. The transistor 19 is then turned on and the transistor 18 is also turned on.As a result, the charging current flows from the power supply terminal 6 through the transistor 18 to the battery 14, and the battery 14 is thereby charged.

This sequence of operations is repeated as long as the result of the judgment at the step S1 is negative, and the result of the judgment at the step S2 is affirmative.

When the telephone handset 11 is switched from the stand-by state to the communication state, and the CPU 12 activates the communication signal Sc. When this communication signal Sc is activated, then the result of judgment at the step S1 will be affirmative, and the step S3 is selected. As a result, the signal at the output port 26 is changed from high to low. The transistors 19 and 18 are turned off, and the charging is interrupted. The interruption of the battery charging is continued until the communication is terminated and the communication signal Sc is turned inactive. The signal at the output port 26 is also low to interrupt or terminate the charging when the result of judgment at the step 52 is negative, i.e., the CPU 23 finds that the charging should not be made on the basis of the charging conditions.

When the telephone handset 11 is returned from the communication state to the stand-by state, the communication signal Sc is turned inactive, then the CPU 23 selects, at the step S1, the step S2, and provided that the result of judgment at the step S2 is affirmative, the signal at the output port 26 is raised to high again, to turn on the transistors 4 and 3, so that the charging of the battery 14 is resumed.

As has been described, according to this embodiment, the processing similar to Embodiment 1 can be implemented by means of software, using the almost identical hardware configuration (the only exception being the addition of the conductor for input of the communication signal Sc).

Accordingly, it is possible to provide a mobile telephone which is even less costly than the first embodiment.

The "charging" mentioned in the above description of Embodiments 1 and 2 means rapid charging, i.e., the current for the rapid charging is greater than the current for trickle charging. The trickle charging means charging with a current just enough to replace capacity loss due to selfdischarge and normally by continuous connection to maintain the battery in a charged condition. In such condition, two types of current, i.e., the current for rapid charging or the current for trickle charging, are applied to the power supply terminal according to a charging conditions.

The thermal influence or noise from the battery charging circuit has little effect during trickle charging since the charging current is small. It is therefore not necessary to halt the trickle charging during communication.

Nevertheless, the trickle charging may also be halted during communication. The decision whether the trickle charging to be halted or not is performed by the CPU 23 or by another microprocessor (not shown). If the communication signal is active and the trickle charging is to be halted, then neither the current for rapid charging nor the current for trickle charging is applied to the power supply terminal 6. If the communication signal Sc is active and the trickle charging is to be continued, the current for trickle charging is applied to the power terminal.

Claims

WHAT IS CLAIMED IS:

1. A mobile telephone comprising a telephone handset (11) having a battery (14) provided therein, said telephone handset activating a communication signal (Sc) when it is operating for communication; a power supply terminal (6); a battery charging circuit (7) connected between the power supply terminal (6) and said battery (14) for performing charging of said battery (14); a charging prohibiting means (2) for prohibiting the charging by said battery charging circuit (7) when the communication signal (Sc) is active.

2. The telephone according to claim 1, wherein said charging prohibiting means (2) comprises a switching element in series with said battery charging circuit (7) between said power supply terminal (6) and said battery (14), and means (5, 4) for turning off said switching element (3) when said communication signal (Sc) is active, and for turning on said switching element when said communication signal (Sc) is inactive.

3. A mobile telephone comprising: a telephone handset (11) having a battery (14) provided therein, said telephone handset activating a communication signal (Sc) when it is operating for communication; a power supply terminal (6); and a battery charging circuit (17) connected between the power supply terminal (6) and said battery (14) for performing charging of said battery (14); wherein said battery charging means comprises a switching element (18) connected between said power supply terminal (6) and said battery (14), and charging control means (22) for turning off said switching element (18) to disable said charging when said communication signal (Sc) is active.

4. The telephone according to claim 3, wherein said charging control means (22) turns on said switching element when said communication signal (Sc) is inactive, and other charging conditions are also satisfied.

5. The telephone according to claim 3, wherein said charging control means (22) comprises a microcomputer (22) which is also used for control over charging in accordance with conditions of the battery (14).

6. A battery-powered radio tonceiver induding a rechargeable battery and a battery charging circuit, the transceiver having a stand-by operation mode and an active communication operation mode, wherein the battery charging circuit is responsive to the operation mode to disable charging of the battery when the tranceiver is in said active communication operation mode.