Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Reexamination Certificate
2001-03-16
2002-04-16
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
C320S116000
Reexamination Certificate
active
06373223
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 plurality of 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 plurality of battery devices, a switching transistor
2
connected to a primary coil Np in series is switched 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 plurality of 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 switched ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil Ns. Since the plurality of secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the plurality of battery devices, whereby the plurality of battery devices are equalized in voltage.
In this former circuit, in addition to that the switching transistor is simply switched 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 plurality of battery devices, a switching transistor
34
connected to a primary coil
16
in series is switched 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 plurality of battery devices and wound on a common transformer core with 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 switched ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil. Since the plurality of secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the plurality of battery devices, whereby the plurality of 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 means (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 plurality of battery devices thereby to equalize the output voltages of the plurality of 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.
SUMMARY OF THE INVENTION
An object of the present invention is to resolve the above-mentioned disadvantages (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.
In order to resolve the above-mentioned problems, in a voltage equalizing apparatus for battery devices, wherein each of a plurality of closed circuits is constituted of each of a plurality of battery devices (
1
-
1
to
1
-n) interconnected in series on a secondary side, each of a plurality of secondary windings (
4
-
1
to
4
-n) magnetically coupled with each other in a transformer (
3
), and each of a plurality of switching devices (
2
-
1
to
2
-n) on the secondary side, wherein a closed circuit is constituted of a battery device (
1
-m) on a primary side, a primary winding (
4
-m) magnetically coupled with the secondary windings in common, and a switching device (
2
-m) on the primary side, and wherein the plurality of switching devices on the secondary side and the switching device on the primary side are alternately switched ON and OFF, thereby equalizing the output voltages of the plurality of battery devices (
1
-
1
to
1
-n) interconnected in series on the secondary side; the ON operation of the plurality of switching devices (
2
-
1
to
2
-n) on the secondary side is continued until after the completion of release of exciting energy stored in the transformer by an ON operation of the switching device (
2
-m) on the primary side, into the plurality of battery devices on the secondary side through the plurality of switching devices (
2
-
1
to
2
-n) on the secondary side, whereby the above-mentioned object is achieved.
Further, means for detecting the variation in the output voltages of the plurality of battery devices (
1
-
1
to
1
-n) interconnected in series on the secondary side is provided, whereby in case of a large variation, the ON duration of the switching device (
2
-m) on the primary side and/or the plurality of switching devices (
2
-
1
to
2
-n) on the secondary side is extended.
In case of a small variation in the output voltages of the plurality of battery devices interconnected in series on the secondary side, the ON/OFF operation of the switching devices on the first and primary sides is stopped, and/or the ON duration of the switching devices on the first and primary sides 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 case that the variation in the output voltages of the plurality of battery devices interconnected in series on the secondary side becomes smaller than a predetermined value, the ON duration of the switching device on the first and/or of the switching devices on the primary sides is shortened for reducing a equalizing current
Anzawa Seiichi
Matsui Fujio
Nishizawa Hiroshi
Luk Lawrence
Nagano Japan Radio Co. Ltd.
Rosenthal & Osha L.L.P.
Wong Peter S.
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