Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – Having variable number of cells or batteries in series
Reexamination Certificate
2001-10-18
2003-07-01
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
Having variable number of cells or batteries in series
Reexamination Certificate
active
06586910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique capable of equalizing voltages across both terminals of the respective series-connected storage elements in such a manner that energy is transferred among a plurality of series-connected storage elements which are mounted on an electric automobile, an energy-hybrid type vehicle, and various sorts of systems capable of using storages of electric energy.
2. Description of the Related Art
Japanese Laid-open Patent Application No. Hei-8-214454 and U.S. Pat. No. 5,594,320 discloses voltage equalizer circuits.
Generally speaking, a voltage equalizer circuit disclosed in these publications is referred to as a “flyback type voltage equalizer circuit.” As indicated in
FIG. 8
, the flyback type voltage equalizer circuit is equipped with a transformer having a plurality of secondary windings n
2
to n
4
; a switch SW
1
connected to a primary winding n
1
of this transformer T
1
; a plurality of rectifying circuits CR
1
, CR
2
, CR
3
connected to the respective secondary windings n
2
, n
3
, n
4
of the transformer T
1
; and charging circuits for connecting outputs of the respective rectifying circuits in each of unit cells. In this flyback type voltage equalizer circuit, constant electric power outputs of the respective secondary windings are rectified which are obtained by switching the primary winding of the transformer by the switch SW
1
, and then, each of the unit cells of capacitor batteries C
1
, C
2
, C
3
which are constituted to be series-connected to each other is charged by the constant electric power outputs. As a result, when a battery voltage of a unit cell is low, a charge current becomes large, whereas when a battery voltage of a unit cell is high, a charge current becomes small, so that a plurality of series-connected battery voltages can be automatically and equally charged to the capacitor batteries.
In such a flyback type voltage equalizer circuit, while such a cycling operation between the charging operation and the discharging operation is repeatedly carried out by the switch, since the electric power is supplied from the power supply side every time switching operation is performed, the battery voltage is increased. Even when the battery voltage is reached to a predetermined voltage value, since the switching operation is continued, the resulting battery voltage is more and more increased, and finally, the battery may be brought into the overcharge condition. Such a flyback type voltage equalizer circuit necessarily requires the circuit capable of preventing the overcharge condition, and therefore, owns such a problem that the entire circuit thereof becomes complex and is manufactured in high cost.
Also, generally speaking, the voltage equalizer circuit described in the above-described U.S. Pat. No. 5,594,320 is referred to as a forward type voltage equalizer circuit. As shown in
FIG. 9
, in this forward type voltage equalizer circuit, a plurality of closed circuits are arranged in such a manner that each of batteries constituted by series-connecting a plurality of cells
11
,
12
,
60
,
61
, each of plural windings
67
to
70
, and each of plural first switching elements
72
to
75
are series-connected to each other. Since all of these switching elements
72
to
75
are turned ON/OFF in the synchronous manner, a charging operation is carried out from a battery having a high cell voltage into a battery having a low cell voltage. As a result, voltages among the terminals of the respective cells may be equalized.
Such a forward type voltage equalizer circuit may have a function capable of equalizing the respective terminal voltages of these plural battery cells. However, the equalized voltages become the averaged voltage (correctly speaking, voltage equivalent to such a condition that battery energy is averaged) of the respective battery voltages, so that the battery voltage cannot be converged to the target voltage. Also, since the equalizer itself does not own the charging function, when the equalizing operation is continued, the discharge operation of the battery is carried out by the energy loss consumed by this equalizer. As a result, there is a risk that the battery may be brought into the over discharge condition.
SUMMARY OF THE INVENTION
The present invention has been made to solve the drawbacks of the above-explained flyback type voltage equalizer circuit and forward type voltage equalizer circuit, and therefore, has an object to provide a voltage equalizer apparatus for storage elements, capable of converging voltages among terminals of a plurality of series-connected storage elements to a final target value, while equalizing operation is carried out without occurrences of overcharging operation and of overdischarging operation.
To solve the above-described problem, according to an aspect of the present invention, in such a voltage equalizer apparatus in which each of plural windings electromagnetically coupled to each other, each of plural storage elements series-connected to each other, and each of plural first switching elements are connected to each other in a series connecting manner so as to constitute a plurality of closed circuits, a reference voltage winding electromagnetically coupled to the plurality of windings is provided; both a DC power supply and a second switching element are series-connected to the reference voltage winding; and all of the plural first switching elements and the second switching element are turned ON/OFF in a synchronous manner. As a consequence, the terminal-to-terminal voltages of the plural storage elements which are series-connected to each other can be converged to a final target value without risks of overcharging operation and overdischarging operation with respect to the storage elements, while performing the voltage equalizing operation.
Also, while the plural series-connected storage elements are series-connected to the DC power supply so as to constitute the voltage equalizer apparatus, the overall DC output may be connected to both an external power supply and an external load.
Also, since the output voltage of the DC power supply is variable, the terminal-to-terminal voltages of the plural series-connected storage elements may be converged to an arbitrary voltage.
Also, the DC power supply owns a bidirectional characteristic and is provided with an apparatus capable of supplying electric power to the plurality of series-connected storage elements, and also, capable of absorbing electric power supplied from the plurality of series-connected storage elements. As a result, the terminal-to-terminal voltages of the plural series-connected storage elements may be made lower than the present voltages.
Also, the voltage equalizer circuit comprises a voltage detecting section for detecting voltages among terminals of the plurality of series-connected storage elements; and the voltage of the DC power supply is set in response to an averaged terminal-to-terminal voltage of the storage elements, which is calculated from the voltage detecting section. As a result, since the terminal-to-terminal voltages of the storage elements can be gradually increased, the terminal-to-terminal voltages of the plural series-connected storage elements can be converged to the final target value without increasing the current capacities of the switching elements and also the capacity of the DC power supply.
It should be noted that when the storage elements are constituted by electric double layer capacitors, the allowable minimum voltage thereof is equal to a zero volt.
Also, the output voltage of the DC power supply is set between an allowable maximum voltage and an allowable minimum voltage, which are determined based upon a material of the storage element. As a result, the terminal-to-terminal voltages can be converged to the final target value, while neither a specifically-designed abnormal voltage detecting circuit, nor a protection circuit is provided with respect to the plural series-connected storage elements.
Also, accordin
Anzawa Seiichi
Ishii Mitsunori
Matsui Fujio
Nishizawa Hiroshi
Fuji Jukogyo Kabushiki Kaisha
Rosenthal & Osha L.L.P.
Tibbits Pia
Tso Edward H.
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