Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-04-14
2001-03-06
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S136000
Reexamination Certificate
active
06198255
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the protection of a secondary battery in the case where a charging current from a charger to a secondary battery is abnormally large (in case of an abnormal charging current).
2. Description of the Related Art
FIG. 2
shows a conventional protective IC and protective device against charge and discharge of a secondary battery. The conventional protective device includes a convention IC
21
, a discharging current control switching element
16
, a charging current control switching element
17
and a current fuse
22
. The conventional protective IC
21
includes an overcharge detecting circuit
7
, an overdischarge detecting circuit
8
, an overcurrent detecting circuit
9
, a level converting circuit
10
, a NOR circuit
14
and so on. The protective IC
21
has a function of preventing a secondary battery
15
from being charged up to an excessive voltage by controlling the on/off operation of the discharging current control switching element
16
and the charging current control switching element
17
(an overcharge protective function), a function of preventing the secondary batter
15
from being discharged down to a too small voltage (an overdischarge protection function), and a function of preventing the secondary battery
15
from discharging an excessive current (an overcurrent protection function).
In order to realize a function of preventing an excessive charging current from flowing into the secondary battery
15
from the charger (an abnormal charging current protection function), the conventional protective device is designed such that a current fuse
22
is disposed between a secondary battery positive electrode connection terminal
2
and a charger positive electrode connection terminal
19
and the current fuse
22
is cut when a large charging current (abnormal charging current) flows.
In the case of using the conventional current fuse
22
, there arises such a problem that the secondary battery including the protective device is never again used if the abnormal charging current is detected once. Also, there arises such a problem that the efficiency is deteriorated by heat of the resistance component of the current fuse. Further, there arises such a problem that the addition of the current fuse causes the number of parts to increase and the mounted area increases, resulting in the prevention of lowering the costs, decreasing the size and weight thereof.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above problem, and therefore has an object to provide a charge/discharge controlling semiconductor device which detects an abnormal charging current using the resistance value of the on-state of a switching element without using a current fuse.
In order to achieve the above object, according to the present invention, there is provided a device for controlling a charging current flowing from a charger to a secondary battery and a discharging current flowing from the secondary battery to a load by the on/off operation of a switching element, in which an abnormal charging current is detected by using the resistance value of the on-state of the switching element, and the abnormal charging current detection state is held until the charger is separated after the detection of the abnormal charging current.
REFERENCES:
patent: 5783322 (1998-07-01), Nagai et al.
patent: 5909103 (1999-06-01), Williams
patent: 5909104 (1999-06-01), Scott
Adams & Wilks
Seiko Instruments Inc.
Tso Edward H.
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