Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-04-20
2001-06-05
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S127000
Reexamination Certificate
active
06242890
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a charge/discharge control the circuit which can control charge/discharge of a secondary cell and further relates to a chargeable electric power source apparatus using the charge/discharge control circuit.
A conventional electric power source apparatus provided with a secondary cell or battery is shown in a block diagram of FIG.
2
. For example, such a type of apparatus is disclosed in Japanese Patent Application Laid-Open No. Hei 4-75430 entitled “Chargeable Type Electric Power Source Apparatus”. More specifically, a secondary cell
101
is connected to an external terminal −V
0
or +V
0
through a switching circuit
103
. Further, A charge/discharge control circuit
102
is connected in parallel to the secondary cell
101
. The charge/discharge control circuit
102
has a function detecting a voltage of the secondary cell
101
. In either an overcharged condition (where the voltage is kept higher than a predetermined value) of the secondary cell
101
or an overdischarged condition (where the voltage is kept lower than a predetermined voltage value), a signal for turning off the switching circuit
103
is fed from the charge/discharge control circuit
102
. Accordingly, in the overcharged condition, the switching circuit
103
is turned off, so that a charge is interrupted to the secondary cell
101
from a primary electric power source which is connected to the external terminals −V
0
and +V
0
. In case of the overdischarged condition, the switching circuit
103
is turned off, so that a supply of the energy to a load (for example, a portable telephone using the secondary cell) is interrupted. Namely, the charge/discharge control circuit
102
controls the switching circuit
103
between the secondary cell
101
and the external terminals, thereby preventing a charge larger than necessary from the external terminals to the secondary cell
101
and at the same time preventing an excessive chargeability degradation of the secondary cell caused by an energy supply from the secondary cell
101
to the load connected to the external terminals.
Also, a chargeable electric power source apparatus as shown in a block diagram of
FIG. 30
is known as another conventional example. In
FIG. 30
, a secondary cell
101
is connected to an external terminal −V
0
or +V
0
through a switching circuit
103
and a current sensing resistor
104
. Further, A charge/discharge control circuit
102
is connected in parallel to the secondary cell
101
and an overcurrent detecting circuit
105
. The charge/discharge control circuit
102
has a function of detecting a voltage of the secondary cell
101
. In either an overcharged condition of the secondary cell
101
or an overdischarged condition, a signal for turning off the switching circuit
103
is output from the charge/discharge control circuit
102
. Also, in the case where an accident occurs in the load to cause the overcurrent condition, a comparator
21
monitors the voltage of the current sensing resistor
104
and compares it with a voltage of a reference voltage circuit
106
.
It is assumed that V
REF
[V] is the voltage value of the reference voltage circuit
106
, R[&OHgr;] is the resistance value of the current sensing resistor
104
(in this case, the ON-resistance of the switching circuit
103
is assumed to be much smaller than R), and I [A] is the current flowing in this case, the current is represented as following equation (1).
I=V
REF
/R [A]
(1)
In this case, the output of the comparator
21
is changed from “H” to “L”, a transistor
107
is turned off, a capacitor
109
is charged by a constant current source
108
, and after a certain time lag, the output of a comparator
302
is changed from “H” to “L”, and the switching circuit
103
is turned off. Namely, the constant current source
108
, the capacitor
109
and the transistor
107
constitute a time delay circuit for delaying the output of the comparator
302
. The delayed signal is input into the comparator
302
together with the signal of the reference voltage circuit
106
. These signals are compared with each other in the comparator
302
. The output turns off the switching circuit
103
.
Another conventional electric power source apparatus provided with a secondary cell and a charge/discharge control circuit is shown in a block diagram of FIG.
37
. For example, such a type of apparatus is disclosed in Japanese Patent Application Laid-Open No. Hei 4-75430 entitled “Chargeable Type Electric Power Source Apparatus”. More specifically, a secondary cell
24
and a charge/discharge controlling IC
374
are connected to an external terminals +V and −V through switching transistors
372
and
373
, respectively.
For instance, in the case where the voltage of the secondary cell
24
exceeds an overcharged voltage when a charging electric source is connected to the external terminals +V and −V, the switching transistor
372
is switched over from the “ON” condition to “OFF” condition to thereby stop the charge from the external terminals to the secondary cell
24
. Conversely, in the case where a portable equipment such as a video camera or the like is connected to the external terminals and electric charge is supplied from the secondary cell
24
to the portable equipment, if the voltage of the secondary cell drops below the overdischarged voltage, the switching transistor
373
is switched over from the “ON” condition to “OFF” condition to thereby stop the discharge. One of the transistors
372
and
373
functions as a “transistor” and the other functions as a “diode”. The functions as the transistor and the diode are alternatively used in accordance with the charging or discharging condition. A substrate of each transistor is connected to an associated source so as to be capable of functioning as the diode.
The conventional charge/discharge control circuit as shown in
FIG. 2
, has a drawback of a large power consumption to shorten the service life of the secondary cell of the energy supply source. As a result, the period of time of use of the equipment to be driven by the secondary cell would be shortened. Further, under the overdischarged condition were the chargeability capacity of the secondary cell is degraded, even though the energy supply from the secondary cell to the external equipment by the switching circuit is interrupted, the power consumption of the charge/discharge control circuit per se provided within the power source apparatus causes the charge to be further discharged to accelerate the degradation of the cell and the service life thereof.
In order to overcome the above-noted short-comings inherent in the prior art system, an object of the present invention is to provide a chargeable power source apparatus with a long service life secondary cell by reducing the power consumption of the charge/discharge control circuit.
The conventional charge/discharge control circuit shown in
FIG. 30
suffers from the following defects. Namely, under the condition that a charger is connected with the terminals −V
0
and +V
0
from the outside and the secondary cell
101
is charged, when the secondary cell is fully charged, the switching circuit
103
is turned off. By this “OFF” operation, the potential between both ends of the secondary cell
101
is reduced, and the system is again kept under the charged condition, i.e., the switching circuit
103
is turned on. At the voltage after the completion of the charging operation, the detection of the full charge would be oscillated unstably.
As described in the description of the conventional system, when the overcharged condition appears during the charging operation to the secondary cell, the charge/discharge control circuit operates to turn off the switching circuit for controlling the charge to the secondary cell. However, since the charge/discharge control circuit is connected in parallel with the secondary cell, the current to
Kojima Yoshikazu
Mukainakano Hiroshi
Shimoda Sadashi
Sudo Minoru
Takashina Takayuki
Adams & Wilks
Luk Lawrence
Seiko Instruments Inc.
Wong Peter S.
LandOfFree
Charge/discharge control circuit and chargeable electric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Charge/discharge control circuit and chargeable electric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Charge/discharge control circuit and chargeable electric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443430