Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
1999-05-13
2001-12-11
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S136000
Reexamination Certificate
active
06329795
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a charging and discharging control circuit for controlling charging and discharging of secondary batteries and to a charging type power supply device having secondary batteries with the charging and discharging control circuit built therein.
As a conventional charging type power supply device comprising a secondary battery, a power supply device shown in a circuit block diagram of
FIG. 2
is known. Such a structure is disclosed in, for example, Japanese published unexamined patent application number H4-75430(1992) entitled “CHARGING TYPE POWER SUPPLY DEVICE.” More specifically, a secondary battery
101
is connected to an external terminal −V
0
or +V
0
through a switch circuit
103
. Further, a charging and discharging control circuit
110
is connected in parallel to the secondary battery
101
. The charging and discharging control circuit
110
has a function of detecting the voltage of the secondary battery
101
. In the case that the secondary battery
101
is in either in an over-charged state (a state where the battery voltage is above a predetermined value —hereinafter referred to as an over-charge protection state) or in an over-discharge state (a state where the battery voltage is below a predetermined value —hereinafter referred to as an over-discharge protection state), a signal is output from the charging and discharging control circuit
110
to turn off the switch circuit
103
. Further, it is possible to restrict the current through the switch circuit
103
by making, when the external terminal +V
0
reaches a certain voltage, the switch circuit
103
turn off to stop the discharging. In other words, the discharging can be stopped when the current is excessive (over-current control). This state is hereinafter referred to as an over-current protection state. It is the role of the charging and discharging control circuit to protect the battery against these states.
Also, in the case that a plurality of secondary batteries are serially connected, a power supply device having a charging and discharging control circuit for detecting over-charge and over-discharge of the respective batteries can be similarly realized.
SUMMARY OF THE INVENTION
However, a charging and discharging control circuit structured in this way has a drawback in that, its own current consumption shortens the operating time per charge of an apparatus using the secondary battery.
FIG. 3
shows an example of an internal circuit of the charging and discharging control circuit
110
in the case where two secondary batteries are serially connected. In this circuit example, only a circuit for over-charge detection is shown, but the circuit used for over-discharge detection is similar to this. Description is made using the example of an internal circuit shown in FIG.
3
.
The internal circuit example shown in
FIG. 3
illustrates a case where comparators are used as means for detecting over-charge, but other detection means may also be used which are similar to this. The charging and discharging control circuit
110
comprises: over-charge detection comparators
113
and
114
; reference voltage circuits
115
and
116
for supplying a predetermined reference voltage Vr to input terminals of the over-charge detection comparators
113
and
114
; a voltage division circuit
111
including resistors R
0
-R
1
, for dividing the terminal voltage of the secondary batteries
101
and
102
; a voltage division circuit
112
including resistors R
2
-R
3
; and an internal control circuit
120
. In the example shown in the figure, only the case of two secondary batteries is illustrated, but cases where two or more secondary batteries are connected are similar to this. The over-charge detection comparators
113
and
114
have a function of comparing with the reference voltage Vr of the reference voltage circuits
115
and
116
the divided output which is the terminal voltage of the secondary batteries
101
and
102
divided by the voltage division circuits
111
and
112
, respectively, to detect an over-charge state.
The output of the over-charge detection comparators
113
and
114
becomes high when the level of the divided output voltage inputted to their positive phase input terminals becomes higher than the reference voltage Vr.
The internal control circuit
120
outputs a signal for controlling the switch circuit
103
with the output of the over-charge detection comparators as an input signal.
FIG. 4
is a block diagram of the comparators used in
FIGS. 1 and 3
. The comparator is provided with a positive phase input terminal
130
, an inverted input terminal
131
, an output terminal
132
of which the voltage level of the output varies depending on the voltage input to the positive phase input terminal
130
and to the inverted input terminal
131
, and a positive power supply terminal
133
and a negative power supply terminal
134
for supplying power for operating the comparator.
The comparator consumes current flowing from the positive power supply terminal to the negative power supply terminal.
The power supply of the over-charge detection comparators
113
and
114
is the positive electrode of the upper serially-connected secondary battery
101
and the negative electrode of the lower serially-connected secondary battery
102
.
Accordingly, assuming that i1 and i2 represent the current consumption of the over-charge detection comparators
113
and
114
, respectively, and the current consumption I of the over-charge detection comparators of the charging and discharging control circuit
110
is i1+i2, which is equivalent to the current consumed by the two comparators for over-charge detection.
With regard to over-discharge, similarly, the current consumption of the over-discharge comparators of the charging and discharging control circuit, in the case that a plurality of secondary batteries are serially connected, is equal to that of the plurality of over-discharge detection comparators.
An object of the present invention is therefore, in order to solve these conventional problems, by serially connecting positive power supply terminals and negative power supply terminals of means for detecting over-charge or means for detecting over-discharge, to decrease a current consumption of the charging and discharging control circuit, and to extend the operating time per charge of secondary batteries.
REFERENCES:
patent: 5206578 (1993-04-01), Nor
patent: 5519563 (1996-05-01), Higashijima et al.
patent: 5547775 (1996-08-01), Eguchi et al.
patent: 5652501 (1997-07-01), McClure et al.
patent: 5742148 (1998-04-01), Sudo et al.
Adams & Wilks
Seiko Instruments Inc.
Tso Edward H.
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