Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2001-11-02
2003-10-28
Chapman, John E. (Department: 2858)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
Reexamination Certificate
active
06639408
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery voltage measurement device for measuring a voltage of stacked rechargeable batteries (a battery pack) which is mounted in an apparatus driven by the rechargeable batteries, such as an electric vehicle or the like.
2. Description of the Related Art
As a low-pollution vehicle designed for the purpose of solving environmental problems and energy problems, an electric vehicle such as an HEV (hybrid electric vehicle) and a PEV (pure electric vehicle) has received a great deal of attention up to the present. The electric vehicle has rechargeable batteries mounted therein, and the electric power of the rechargeable batteries drives an electric motor so as to run the electric vehicle. The electric vehicle has a high-voltage circuit for driving the electric motor and a low-voltage circuit for driving various electronic devices such as acoustic equipment, lighting devices, and an electronic controller (e.g., ECU; electronic control unit). The high-voltage circuit includes an inverter for driving an electric motor, and the inverter controls and drives the electric motor.
In a battery control section of such an electric vehicle, in order to obtain an output state of the rechargeable batteries which stably supplies electric power to the electric motor, it is necessary to use a battery voltage measurement device to accurately measure a battery voltage of each battery block of the battery pack.
FIG. 5
is a circuit diagram illustrating an exemplary structure of a conventional battery voltage measurement device
100
. In
FIG. 5
, the battery voltage measurement device
100
includes: a plurality of switches
120
in which each pair of adjacent switches
120
sequentially selects two corresponding output terminals
111
a
of a battery block
111
included in a battery pack
110
; a capacitor
130
for storing (copying) a designated battery voltage; switches
140
for selectively applying the battery voltage stored in the capacitor
130
to a differential amplifier
150
; the differential amplifier
150
for differentially amplifying the stored battery voltage which is input thereto via the switches
140
; and an A/D converter
160
for performing an A/D conversion of the voltage output from the differential amplifier
150
.
The battery pack
110
includes a plurality of serially-connected battery blocks
111
. A value of a voltage output from one battery block
111
(battery module) is, for example, about DC 20 V. The maximum value of a voltage output from all of the serially-stacked battery blocks
111
is about DC 400 V.
Each pair of adjacent switches
120
is connected to the two corresponding output terminals
111
a
of each of the plurality of battery blocks
111
.
The capacitor
130
has electrodes connected to a pair of conductor lines
141
a
and
141
b
laid between the switches
120
and the switches
140
. The capacitor
130
temporarily stores a battery voltage of each of the battery blocks
111
, which is transferred via two designated switches
120
to the capacitor
130
.
Each of the switches
140
is connected to one of the two input terminals of the differential amplifier
150
and serves to connect the differential amplifier
150
to the capacitor
130
or disconnect the differential amplifier
150
from the capacitor
130
. On/Off control of the plurality of switches
120
and the switches
140
is performed by a switching controller (not shown), e.g., a microcomputer.
With the above-described structure, at first, in order to store (copy) a battery voltage of a first battery block
111
in (into) the capacitor
130
, each of the switches
120
connected to one of the two output terminals
111
a
of the first battery block
111
is turned on. At this time, the switches
140
are turned off to disconnect the capacitor
130
from both of the two input terminals of the differential amplifier
150
.
Next, all the switches
120
are turned off to disconnect the capacitor
130
from all of the battery blocks
111
, and then the switches
140
are turned on so as to input the battery voltage of the first battery block
111
, which is stored in the capacitor
130
, to the differential amplifier
150
for a gain adjustment. The battery voltage, e.g., DC 20 V, is differentially amplified by the differential amplifier
150
so as to be DC 5 V, which is in an input voltage range (dynamic range) of the A/D converter
160
. The A/D converter
160
performs an A/D conversion of battery voltage data corresponding to the differentially-amplified battery voltage. The A/D-converted battery voltage data can be read by, for example, a microcomputer (not shown) in a subsequent stage.
In a similar manner, a battery voltage of the second battery block
111
is stored in (copied into) the capacitor
130
. The battery voltage stored in the capacitor
130
which is derived from the second battery block
111
has an inverted polarity to that derived from the first battery block. The battery voltage of the second battery block
111
, which is stored in the capacitor
130
, is differentially amplified by the differential amplifier
150
, and then the A/D converter
160
performs an A/D conversion of the differentially-amplified battery voltage.
Referring to
FIGS. 6A
,
6
B,
7
A,
7
B,
8
A, and
8
B, the differential amplifier
150
and the A/D converter
160
are described in more detail below.
In general, when an analog input voltage is arithmetically processed in a CPU (central processing unit), a voltage value conversion circuit and an A/D converter are used.
The voltage value conversion circuit includes an analog circuit for performing division when an input voltage is high and performing multiplication when the input voltage is low (the analog circuit also performs addition and subtraction in addition to division and multiplication). The analog circuit is realized by a voltage divider circuit including a resistance, a circuit using an operational amplifier, and the like. A conversion result produced by the voltage value conversion circuit corresponds to an input voltage range of an A/D converter. The input voltage range of the A/D converter is, for example, between GND (0 V) and DC 5 V.
The A/D converter is a component for comparing an input voltage (e.g., a battery voltage output from the voltage value conversion circuit) with a reference voltage to convert the input voltage into digital data which can be read by a microcomputer. The performance of an A/D converter is generally determined according to the fineness of comparison in view of resolution rather than conversion accuracy although it is important for comparing voltages. The fineness of comparison represents the resolution.
In a brief description of the resolution, as illustrated in
FIG. 6A
, for example, in the case of a 10-bit A/D converter, an input voltage range from 0 V to 5 V is resolved into 1024 (the tenth power of two) levels of a reference voltage, and an input voltage is compared to the reference voltage to determine at which voltage level the input voltage is. In the case where the number of bits becomes greater, as illustrated in a 12-bit A/D converter of
FIG. 6B
, the input voltage range from 0 V to 5 V is resolved into 4096 (the twelfth power of two) levels of the reference voltage, and an input voltage is compared to the reference voltage to determine at which voltage level the input voltage is. That is, as the number of bits becomes greater, more detailed measurement of the input voltage can be carried out.
In general, in the case of detecting a potential difference in an input voltage, a differential amplifier includes an operational amplifier as a voltage value conversion circuit. The operational amplifier is used when a reference point of an input voltage A is not determined, for example, in the case of a battery voltage.
For example, when the polarity of an input voltage A
1
is noninverting (i.e., always positive or negative), as illustrated in
FIG. 7A
, a gain (i.e., R
2
/R
1
) of a differential amplifier
151
a
is
Maki Ichiro
Morimoto Naohisa
Yudahira Hirofumi
Chapman John E.
Kerveros James
Matsushita Electric - Industrial Co., Ltd.
Snell & Wilmer LLP
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