Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With individual charging of plural batteries or cells
Reexamination Certificate
2001-11-20
2003-11-04
Luk, Lawrence (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With individual charging of plural batteries or cells
C320S118000
Reexamination Certificate
active
06642693
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for performing energy transfer among a plurality of battery devices interconnected in series and carried on an electric car or a hybrid car and thereby equalizing each voltage across each of the battery devices interconnected in series.
2. Description of the Related Art
The related art in this field is disclosed, for example, in Japanese Laid-Open Patent Publication No. Hei 11-176483 and U.S. Pat. No. 5,003,244. In the configuration of the former patent as shown in
FIG. 7
, the output voltages E
1
to En of a plurality of battery devices
1
-
1
to
1
-
n
are interconnected in series. For the purpose of the balance correction of the output voltages of the battery devices, a switching transistor
2
connected to a primary coil Np in series is turned ON and OFF in response to the output voltages. A converter is composed of a plurality of secondary coils Ns each corresponding to each of the battery devices and wound on a common transformer core with the primary coil. The connection thereof is configured such that the secondary output of the converter charges each battery device. When the switching transistor
2
is periodically turned ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil Ns. Since the secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the battery devices, whereby the battery devices are equalized in voltage.
In this former circuit, in addition to that the switching transistor is simply turned ON and OFF, the current Ip flowing in the primary coil Np is controlled depending on the load current Io.
Further, in the configuration of the latter patent as shown in
FIG. 8
, the output voltages of a plurality of battery devices
25
,
26
,
27
,
28
are connected in series. For the purpose of the balance correction of the output voltages of the battery devices, a switching transistor
34
connected to a primary coil
16
in series is turned ON and OFF in response to the input from a power supply
30
. A converter
14
is composed of a plurality of secondary coils
21
,
22
,
23
,
24
each corresponding to each of the battery devices and wound on a transformer core
18
common to the primary coil
16
. The connection thereof is configured such that the secondary output of the converter
14
charges each battery device. When the switching transistor
34
is periodically turned ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil. Since the secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the battery devices, whereby the battery devices are equalized in voltage.
There has been the following problems in such above-mentioned related art apparatuses for equalizing the voltages across each of a plurality of energy storage device (battery devices) interconnected in series by means of the switching of a converter.
(a) In each above-mentioned related art apparatus, the magnetizing force is one directional in the transformer core for the ON and OFF duration of the switching device (transistor) Accordingly, the range of the change in magnetic flux density of the core is small, and hence the utilization of the core is less efficient. The lower efficiency in core utilization implies the necessity of a larger cross section in the core for a specific output power, thereby causing the problems of a larger apparatus and a higher cost.
Further, the switching ON and OFF of the switching device for the voltage equalizing causes a problem that electric charge stored in the capacitance existing between the terminals of the switching device for the OFF duration of the switching device is discharged by the next ON operation thereby to cause a power loss and a noise due to the short-circuit current.
(b) In each above-mentioned related art apparatus, energy stored in the transformer for the ON duration of the switching device is discharged for the next OFF duration of the switching device, thereby charging a battery device having the lowest voltage among the battery devices thereby to equalize the output voltages of the battery devices. Accordingly, the amount of equalizing energy is only the amount of energy stored for the ON duration of the switching device. Therefore, in order to increase the equalizing action, a larger switching device is necessary for increasing the equalizing current. However, this larger switching device causes a larger apparatus and hence a higher cost, as is the above-mentioned case (a). Further, since each battery device has an internal resistance, the higher current from the switching device causes a larger voltage drop across the internal resistance, thereby increasing apparent output voltage of the battery device in charging. This causes a problem of reducing the precision of output voltage equalizing.
In addition to resolving the above-mentioned problems, earnestly desired are short-time equalization of the output voltages of the battery devices, reduction of energy loss after the equalization operation, and setting of the voltage at an arbitrary value after the equalization.
SUMMARY OF THE INVENTION
An object of the present invention is to resolve the above-mentioned problems (a) and (b) thereby to provide a voltage equalizing apparatus having a high efficiency and a high precision of equalizing and being of a small size. Further, an object of the present invention is to provide a voltage equalizing apparatus capable of equalizing to a desired voltage in a short time, reducing the energy loss after the completion of equalization, and setting the voltage after the equalization to be an arbitrary value.
An aspect of the invention for resolving the above-mentioned problems is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices (
1
-
1
to
1
-
n
) interconnected in series, one of a plurality of secondary windings (
4
-
1
to
4
-
n
) magnetically connected with each other through the core (
3
), and one of a plurality of first switching devices (
2
-
1
to
2
-
n
); and
a second closed circuit composed of a second battery device (
1
-
m
), a primary winding (
4
-
m
) magnetically connected with the secondary windings through the core, and a second switching device (
2
-
m
);
wherein the first switching devices and the second switching device are alternately turned ON and OFF to equalize the output voltages of the first battery devices;
when the second switching device is turned ON, exciting energy stored in the core is transported to the first battery devices through the first switching devices; and
the first switching devices continue to be turned ON after the transportation of the exciting energy is completed.
According to the present invention,
when the second switching device is turned ON, exciting energy stored in the core is transported to the first battery devices through the first switching devices, and
the first switching devices continue to be turned ON after the transportation of the exciting energy is completed.
In another configuration, a detector for detecting the variation in the output voltages of the first battery devices (
1
-
1
to
1
-
n
) is provided, whereby in case of a large variation, the ON duration of the second switching device (
2
-
m
) and/or the first switching devices (
2
-
1
to
2
-
n
) is extended.
In another configuration, in case of a small variation in the output voltages of the first battery devices, the ON/OFF operation of the first switching devices and the second switching device is stopped, and/or the ON duration of the first switching devices and the second switching device is extremely shortened. This avoids power loss and noise due to unnecessary voltage equalizing operation in case of the small variation in the output voltages.
In another configurat
Anzawa Seiichi
Matsui Fujio
Nishizawa Hiroshi
Luk Lawrence
Nagano Japan Radio Co. Ltd.
Rosenthal & Osha L.L.P.
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