GB2262668A

GB2262668A - Battery charging device for a portable telephone

Info

Publication number: GB2262668A
Application number: GB9226222A
Authority: GB
Inventors: Hideo Namiki; Motoyoshi Komoda
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1991-12-16
Filing date: 1992-12-16
Publication date: 1993-06-23
Anticipated expiration: 2012-12-16
Also published as: GB2262668B; AU661876B2; AU3019492A; JPH05168168A; CA2085385A1; GB9226222D0; CN1037305C; CA2085385C; CN1076061A

Abstract

A charging device 20A is capable of charging a portable telephone in the same period of time with no regard to the ON/ OFF state of a power source 10a incorporated in the telephone 10. When the connection of the telephone to the charging device is detected, whether or not a power source incorporated in the telephone is in an ON state is determined. A higher charging current is applied when the source 10a is in the ON state than when it is in the OFF state. <IMAGE>

Description

CHARGING DEVICE FOR A PORTABLE TELEPHONE The present invention relates to a charging device for a portable telephone and, particularly, though not exclusively, to a charging device capable of charging a portable telephone in a given period of time regardless of the state of an ON/OFF switch of a power source incorporated in the telephone.

A portable telephone extensively used today is powered by a battery or similar power source. When the power of the power source is consumed, the telephone is connected to a charging device to be charged thereby. The charging device usually has a telephone detecting section for detecting the telephone connected to the device, a charging current source for feeding a charging current to the telephone power source, and a switch for connecting the charging current source to the telephone power source. When the telephone is connected to the charging device, the device detects the connection with the telephone detecting section and operates the switch to feed the charging current from the charging current source to t h e telephone power source.It is a common practice with the conventional charging device to maintain the charging current constant at all times with no regard to the ON/OFF state of the telephone power source. This, however, gives rise to the following problem. Assume that the telephone power source is fully charged in a period of time T1 when in an OFF state or in a period of time T2 when in an ON state. Then, when the telephone power source is in an ON state, the current actually charging the power source is smaller than the charging current being fed from the charging current source since part of the charging current is consumed as an operating current of the telephone.

As a result, the period of time T2 is longer than the period of time T1, i.e., the charging time in the ON state is far longer than the charging time in the OFF state. This makes it impractical to charge the telephone when the power source thereof is held in an ON state.

A feature of an arrangement to be described is to provide a charging device capable of charging a portable telephone in the same period of time with no regard to the ON/OFF state of a power source accommodated in the telephone.

A charging device for charging a power source incorporated in a portable telephone to be described comprises a body to which the portable telephone is to be connected, a charging current source for feeding a current to the power source of the portable telephone, a telephone detecting section for determining whether or not the portable telephone is connected to the body, an ON/OFF state sensing section for determining an ON/OFF state of the power source of the portable telephone, and a current control section for controlling a charging current from the charging current source on the basis of the ON/OFF state of the power source of the portable telephone sensed by the ON/OFF state sensing section.

A conventional arrangement and an arrangement in accordance with the invention and given by way of example will now be described with reference to the accompanying drawings in which: FIG. 1 is a block diagram schematically showing a conventional charging device for a portable telephone; FIG. 2 plots a relation between the charging current and the charging time particular to the conventional charging device with respect to an ON state and an OFF state; FIG. 3 is a block diagram of a charging device embodying the present invention; FIG. 4 is a graph similar to FIG. 2, showing a relation between the charging current and the charging time achievable with the embodiment; and FIG. 5 is a circuit diagram showing the embodiment more specifically.

To better understand the present invention, a brief reference will be made to a conventional charging device for a portable telephone, shown in FIG. 1. As shown, a portable telephone 10 is loaded with a battery or similar power source 10a and may be removably connected to a charging device 20.

The charging device 20 has a telephone detecting section 22 for detecting the telephone 10 when it is attached to the charging device 20, a switch 24 operated by the resulting output of the detecting section 22, and a charging current source 26 On detecting the telephone 10, the detecting section 22 causes the switch 24 to close with the result that the charging current source 26 is connected to the power source 10a of the telephone 10. The conventional charging device 20 feeds a constant charging current from the current source 26 thereof to the telephone 10 with no regard to the ON/OFF state of the telephone power source 10a.

As shown in FIG. 2, assume that the charging current and the duration of charging are I and T, respectively. When the telephone power source 10a is turned off, i.e., in an OFF state while charging is under way, it is fully charged at a time T1.

However, when the power source 10a is in an ON state, part of the charging current is consumed as an operating current of the telephone 10, i.e., the power source 10a is charged by a current smaller than the current actually fed from the charging unit 20.

As a result, a period of time T2 (T2 > T1) is needed for the power source 10a to be fully charged. For example, assume that when I1 is 40 milliamperes, T1 is 10 hours, that the telephone 10 consumes a current 1o of 30 milliamperes in a waiting state, and that a charging current in the ON state of the power source 10a is '2. Then, there holds an equation: 12 = I1 - 1o = 40 - 30 = 10 (milliamperes) The charging time T2 is expressed as: T2 = T1 x Il/ I2 = 40 (hours) Such a period of time T2 is four times as long as the period of time T1 and, therefore, not practical.

Referring to FIGS. 3-5, a charging device embodying the present invention and free from the above problem will be described. In FIGS. 3-5, the same or similar constituents to the constituents of FIGS. 1 and 2 are designated by like reference numerals, and redundant description will be avoided for simplicity.

As shown in FIG. 3, the charging device, generally 20A, has an ON/OFF state sensing section 28 and a current control section 30 in addition to the constituents of the conventional charging device 20, FIG. 1. The sensing section 28 determines whether or not the power source 10a of the telephone 10 is in an ON state. The current control section 30 is connected between the ON/OFF sensing section 28 and a charging current source 26. The current control section 30 changes the charging current of the charging current source 26 in response to an output of the ON/OFF sensing section 28.

FIG. 4 shows a product of a charging current I and a charging time T which is a charge necessary for charging.

Assuming I1 40 milliamperes, T1 = 10 hours, and T2 = 40 hours, then I1 (T2- T1) = 1.2 ampere-hour is the charge being consumed in the telephone 10 during charging.

As shown in FIG.- 4, when the telephone power source iOa is in an OFF state, a charging current I1 is fed from the charging device 20A to the telephone 10. In the illustrative embodiment, when the power source 10a is in an ON state, a charging current 12 (12 > I1) is fed to the telephone 10 in order to compensate for the charge II (T2- T1) being consumed during charging. When 12 is selected to be 160 milliamperes to satisfy an equation I1(T2- T1) = (12- I1)T1, the telephone 10 can be fully charged in the same period of time with no regard to the ON/OFF state of the power source 10a, as shown in FIG. 4.

FIG. 5 shows the charging device 20A and telephone power source 10a more specifically. As shown, when a transistor TR6 constituting a telephone detecting section 22 is turned on by a signal BATT, it indicates that a battery Ba implementing the power source 10a is connected to the charging device 20A.

Then, a transistor TR2 constituting a switch 24 is rendered conductive to connect a charging current source 26 to the power source 10a. At the same time, the telephone 10 sends a signal PSON to a transistor TR5 constituting the ON/OFF state sensing section 28, indicating whether or not the power source 10a is in an ON state. As the output of the transistor TR5 is coupled to a transistor TR4 implementing the current control section 30, the control section 30 controls the charging current I to flow through a terminal V such that the charging current in the ON state of the power source 10 is greater than the charging current in the OFF state.

In summary, it will be seen that there has been described a charging device capable of charging a portable telephone in a given period of time with no regard to the ON/OFF state of a power source incorporated in the tele phone.

It will be understood that, although the invention has been described with reference to a particular embodiment, by way of example, variations and modifications thereof, as well as other embodiments, may be made within the scope of the protection sought in the appended claims.

Claims

1. A charging device for charging a power source incorporated in a portable telephone, comprising: a body to which the portable telephone is to be connected; a charging current source for feeding a current to the power source of the portable telephone; telephone detecting means for determining whether or not the portable telephone is connected to said body; ON/OFF state sensing means for determining an ON/OFF state of the power source of the portable telephone; and current control means for controlling a charging current from said charging current source on the basis of the ON/OFF state of the power source of the portable telephone sensed by said ON/OFF state sensing means.

2. A charging device as claimed in claim 1, wherein said current control means controls said charging current source such that the charging current is greater when the power source of the portable telephone is in an ON state than when said power source is in an OFF state.

3. A charging device as claimed in claim 1, further comprising switching means for connecting said charging current source to the power source of the portable telephone when said telephone detecting means detects said portable telephone.

4. A charging device as claimed in claim 1 substantially as described herein with reference to Figs. 3, 4 and 5 of the accompanying drawings.