Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With individual charging of plural batteries or cells
Reexamination Certificate
2002-10-28
2004-09-21
Tibbits, Pia (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With individual charging of plural batteries or cells
Reexamination Certificate
active
06794851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to charging circuits charging predetermined first and second batteries and a battery charger incorporating such a charging circuit.
2. Description of the Related Art
Recently, mobile communication using mobile phones has been rapidly expanding. The reason is the convenience that users can enjoy mobile communication using mobile phones irrespective of the time and place. In order to ensure such convenience, it is required that a battery charger charging a battery used for a mobile phone can charge a spare battery as well as the battery in the mobile phone body.
FIG. 1
shows a conventional charging system
100
relating to a battery charger that charges a spare battery as well as a battery in a mobile phone body. The charging system
100
includes a spare battery
101
having a low priority in charging, a portable set
102
such as a mobile phone, a main battery
103
having a high priority in the charging provided in the portable set
102
, a transistor
104
, a charging circuit
105
in the portable set
102
, a current detector
106
, a microcomputer and control circuit
107
(hereinafter referred to as a “control circuit
107
”), a charge control circuit
108
that controls switching of the transistor
104
, a transistor
109
, a charge control circuit
110
that controls switching of the transistor
109
, and a resistor
111
as a thermistor element for controlling the temperature of the spare battery
101
.
The charging system
100
charges both spare battery
101
and main battery
103
. In addition, it is assumed that, in an initial state, the transistor
104
is in an ON-state and the transistor
109
is in an OFF-state.
An AC adapter
150
converts an alternating current supplied from an alternator (not shown) to a direct current and supplies the direct current to the spare battery
101
and the main battery
103
as a charging current. The current detector
106
detects the charging current supplied to the main battery
103
and sends the detection result to the control circuit
107
.
In a case where the current detector
106
is detecting the charging current, in other words, where the charging circuit
105
is charging the main battery
103
, the control circuit
107
does not instruct the charge control circuits
108
and
110
to perform the switching of the transistors
104
and
109
, respectively. For this reason, the ON-state of the transistor
104
and the OFF-state of the transistor
109
are maintained. Thus, charging of only the main battery
103
is continued.
On the other hand, in a case where the current detector
106
detects no charging current, in other words, where the main battery
103
is fully charged, the control circuit
107
instructs the charge control circuits
108
and
110
to control the transistors
104
and
109
, respectively. According to the instruction, the charge control circuit
108
decreases the base voltage of the transistor
104
. Additionally, according to the instruction, the charge control circuit
110
increases the base voltage of the transistor
109
. For this reason, the main battery
103
is supplied with only a small charging current. That is, so-called trickle charging is performed. On the other hand, the charging of the spare battery
101
is started such that a large charging current is supplied to the spare battery
101
.
It should be noted that in a case where the main battery
103
is removed from the charging system
100
, the current detector
106
does not detect a charging current. In this case, the control circuit
107
instructs the charge control circuits
108
and
110
to control the transistors
104
and
109
, respectively. That is, according to the instruction, the charge control circuit
108
controls the transistor
104
to assume the OFF-state. On the other hand, the charge control circuit
110
controls the transistor
109
to assume the ON-state according to the instruction. Thus, the charging of the spare battery
101
is started such that a large charging current is supplied only to the spare battery
101
.
FIG. 2
is a graph showing the variation of the charging current with time. Here, the charging current is supplied to the spare battery
101
and the main battery
103
. First, as shown in
FIG. 2
, the charging current is supplied to the main battery
103
. Then, as the main battery
103
is fully charged, the charging current supplied to the main battery
103
is decreased, and the charging current is almost zero when the charging is completed. Thereafter, trickle charging is performed on the main battery
103
. Then, the charging current is supplied to the spare battery
101
.
As an example of the prior art relating to the battery charger that charges not only the battery (main battery) in the mobile phone body but also the spare battery in the above-described manner, there is a “multiple battery, multiple rate battery charger” disclosed in Japanese Patent Publication No. 8-8747 (corresponding to U.S. Pat. No. 5028859).
However, in the above-described conventional charging procedure, though the charging current that is supplied to the main battery
103
from the AC adapter
150
is decreased, the spare battery
101
is not charged at that time. Thus, effective charging is not performed. Additionally, there is also a problem in that the manufacturing cost increases by using the control circuit
107
.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide an improved and useful charging circuit and battery charger in which the above-mentioned problems are eliminated.
It is another and more specific object of the present invention to provide a charging circuit and a battery charger that can charge batteries effectively at low cost.
In order to achieve the above-described objects, according to one aspect of the present invention, there is provided a charging circuit charging predetermined first and second batteries including: a circuit configuration by which a second charging current charging the second battery is obtained by subtracting a first charging current charging the first battery from a current supplied by a power source; and a current setting part that sets the second charging current smaller than the first charging current at least at the beginning of charging.
Also, according to another aspect of the present invention, there is provided a battery charger incorporating the above-described charging circuit.
According to the above-mentioned aspects of the present invention, the second charging current is obtained by subtracting the first charging current used for charging the first battery from the current supplied by the power source. In addition, the amount of the second charging current is set smaller than that of the first charging current at least in the beginning of charging so that the first battery is charged earlier than the second battery. Hence, it is possible to perform effective charging while continuously varying the first and second charging currents and effectively using the charging current supplied by the power source.
REFERENCES:
patent: 5028859 (1991-07-01), Johnson et al.
patent: 6081096 (2000-06-01), Barkat et al.
patent: 6194867 (2001-02-01), Cummings et al.
patent: 8-8747 (1996-01-01), None
Hamai Hidetoshi
Murakami Kouji
Ladas & Parry
Mitsumi Electric Co. Ltd.
Tibbits Pia
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