Apparatus having plural electric double layer capacitors and...

Electricity: battery or capacitor charging or discharging – Capacitor charging or discharging

Reexamination Certificate

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Reexamination Certificate

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06316917

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 11-62445, filed Mar. 9, 1999, entitled “Electric Double Layer Capacitor Apparatus.” The contents of that application are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric double layer capacitor apparatus including a plurality of electric double layer capacitors and a method for adjusting voltages of the plurality of electric double layer capacitors.
2. Description of the Background
Power supplies which include a plurality of electric double layer capacitors are disclosed in U.S. Pat. No. 5,783,928 (hereinafter referred to as the “'928 patent”), entitled “Storage Capacitor Power Supply”; U.S. Pat. No. 5,982,050 (hereinafter referred to as the “'050 patent”), entitled “Power Supply Unit For Automotive Vehicle”; U.S. Pat. No. 5,932,932 (hereinafter referred to as the “'932 patent”), entitled “Storage battery voltage control apparatus”; and Japanese Unexamined Patent Publication (Kokai) 10-201091 (hereinafter referred to as the “'091 publication”), entitled “Power Supply Unit For Automotive Vehicle Utilizing Electric Double Layer Capacitors.” The contents of these applications are incorporated herein by reference in their entirety.
In an electric double layer capacitor apparatus disclosed in the '928 patent, referring to
FIG. 13
, an electric double layer capacitor apparatus includes a plurality of electric double layer capacitors
1
(hereinafter referred to as “a cell” or “cells”). Each cell
1
has a current bypass circuit
16
which is connected to each cell
1
in parallel. An operation voltage of the shunt regulator
7
is set at a maximum charge voltage (V
u
) of the cell
1
by adjusting a ratio of resistance of the resistors (
13
and
15
). When the voltage between a positive and negative pole terminals (
3
A and
3
B) of the cell
1
is equal to the maximum charge voltage (V
u
), the shunt regulator
7
turns on and therefore current flows to the resistor
5
. Accordingly, a PNP transistor
9
turns on and prevents all capacitors from being applied with voltages exceeding maximum charge voltage. When the voltage between the positive and negative pole terminals (
3
A and
3
B) is equal to the maximum charge voltage (V
u
).
In
FIG. 13
, it is supposed that capacitance (C
1
) of the cell (
1
a
) is 1000 (F), capacitance (C
2
) of the cell (
1
b
) is 1150 (F) and charge current is constant at 10 (A). Further, initial voltages of the cells (
1
a
and
1
b
) are equal to zero (V) and the maximum charge voltage (V
u
) is set at 2.5 (V) and equal to a uniform voltage.
Referring to
FIG. 14
, the voltage of the cell (
1
a
) which has smaller capacitance becomes the maximum charge voltage (V
H
) at (t
1
) before the voltage of the cell (
1
b
) becomes the maximum charge voltage (V
H
). Then, the voltage of the cell (
1
b
) becomes the maximum charge voltage (V
H
) at (t
2
) which is after (t
1
) by (&Dgr;t). (&Dgr;t) is approximately calculated as follows:
&Dgr;t=
(
C
2

C
1
)*
V
H
/I=
37.5 seconds.
Heat of about 25 (W) generates in the bypass circuit (
16
) when bypass current flows for the period of &Dgr;t.
The '050 patent discloses a power supply unit which includes a plurality of electric double layer capacitors and a plurality of current bypass circuits which are connected to each cell in parallel, respectively. Each circuit has a Zener diode. The voltage of each cell is substantially adjusted to be Zener voltage.
The '091 reference discloses a power source which includes a plurality of electric double layer capacitors and a plurality of discharge circuits in order to adjust the voltage of each cell. Each discharge circuit is connected to each cell in parallel via a switch. When an accessary switch of a car is turned on, each switch connects each discharge circuit to each cell. Accordingly, the voltage of each cell is adjusted. Each switch may be manually turned on to discharge each cell after an engine stops.
The '932 reference discloses a storage battery voltage control apparatus which includes a plurality of electric double layer capacitors and a voltage-correcting storage battery over switches and a current-limiting resistor. In order to adjust the voltage of each cell, the voltages of each of the storage battery cells high in voltage can be equalized by transferring the charge to a storage battery cell low in voltage.
SUMMARY OF THE INVENTION
According to one aspect of the invention, an electric double layer capacitor apparatus includes a plurality of electric double layer capacitors connected in series, at least one set of a voltage detection device and a discharge device, and a controller. The at least one set is provided to at least one of the plurality of electric double layer capacitors. The voltage detection device is configured to detect a terminal voltage of the at least one of the plurality of electric double layer capacitors. The controller is configured to stop current for charging the plurality of electric double layer capacitors when the terminal voltage detected by the voltage detection device reaches a maximum charge voltage. The discharge device is configured to discharge the at least one of the plurality of electric double layer capacitors such that said terminal voltage drops toward a predetermined target voltage which is lower than the maximum charge voltage when the terminal voltage is higher than the predetermined target voltage, and the discharge device is configured not to discharge the at least one of the plurality of electric double layer capacitors when the terminal voltage is equal to or lower than the predetermined target voltage.
According to another aspect of the invention, a method for adjusting voltages of a plurality of electric double layer capacitors, includes charging the plurality of electric double layer capacitors which are connected in series; detecting a terminal voltage of at least one of the plurality of electric double layer capacitors; stopping charging the plurality of electric double layer capacitors when it is determined that the terminal voltage is equal to or higher than a maximum charge voltage; discharging the at least one of the plurality of electric double layer capacitors such that the terminal voltage drops toward a predetermined target voltage which is lower than the maximum charge voltage when the terminal voltage is higher than the predetermined target voltage; and preventing discharging the at least one of the plurality of electric double layer capacitors such that the terminal voltage is maintained when the terminal voltage is equal to or lower than the predetermined target voltage.
According to yet another aspect of the invention, a voltage control circuit for an electric double layer capacitor apparatus which comprises a plurality of electric double layer capacitors connected in series, includes at least one voltage detection circuit, a controlling circuit, at least one electric discharging circuit. The least one voltage detection circuit is configured to detect a terminal voltage of at least one of the plurality of electric double layer capacitors. The controlling circuit is configured to stop charging the plurality of electric double layer capacitors when it is determined that voltage of at least one of the plurality of electric double layer capacitors is equal to or higher than a maximum charge voltage based on the detected terminal voltage. The at least one electric discharging circuit is provided corresponding to the at least one voltage detection circuit. The at least one electric discharging circuit is configured to discharge electricity charged in adjustment capacitors among the plurality of electric double layer capacitors such that voltage of each of the adjustment capacitors drops toward a predetermined target voltage which is lower than the maximum charge voltage when said terminal voltage is higher t

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