Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2001-04-10
2003-04-01
Le, N. (Department: 2858)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
C340S661000
Reexamination Certificate
active
06541980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiplex voltage measurement apparatus, and specifically to a multiplex voltage measurement apparatus for measuring a voltage of each of serially connected N voltage sources.
2. Description of the Related Art
A high-power electric source of several hundred voltages for an electric vehicle is formed by a number of secondary battery cells, such as nickel-hydrogen storage cells, which are serially connected to each other. Each of the serially connected battery cells should be monitored for its capacity for the purpose of charge/discharge control. In particular, a battery formed by 240 serially connected cells produces a total voltage of 288 V. In such a battery, it is physically difficult to monitor each cell. In Japanese Laid-Open Publication No. 8-140204, for example, the voltage is measured for each of 24 modules each including 10 cells.
In an electric vehicle, high-voltage systems are electrically insulated from a chassis in order to avoid hazardous conditions. On the other hand, since a processor for charge/discharge control uses a potential of the chassis as a reference potential, the voltage of a battery should be insulatively measured. In the battery disclosed in Japanese Laid-Open Publication No. 8-140204, an insulation circuit unit including an operational amplifier, an AD converter, a photocoupler, a power supply, etc., is provided for each module. The structure of such a battery is enormously complicated.
As means of insulatively measuring the output voltage of a sensor or the like, a flying capacitor is known.
FIG. 3
shows a structure of a multiplex voltage measurement apparatus
400
. In this example, the number of voltage sources (N) is 5.
Serially-connected voltage sources V
1
-V
5
are connected to a capacitor
3
through voltage detection terminals T
1
-T
6
, and through a first multiplexer
1
formed by switches S
1
, S
3
, and S
5
and a second multiplexer
2
formed by switches S
2
, S
4
, and S
6
. The capacitor
3
is connected to a voltage measurement circuit
6
through a first sample switch
4
formed by switches
4
a
and
4
b
and a polarity correction circuit
5
.
FIG. 4
is a timing chart for opening/closure of the respective switches S
1
-S
6
, and
4
a
and
4
b.
An operation of the multiplex voltage measurement apparatus
400
is now described with reference to
FIG. 4
in conjunction with FIG.
3
.
Prior to measuring the voltages of the voltage sources V
1
-V
5
, the switches S
1
-S
6
, and
4
a
and
4
b
are all opened (OFF). During period P
1
, first of all. the switches S
1
and S
2
are closed (ON), whereby the voltage of the voltage source V
1
is applied to the capacitor
3
, and a charge is stored in the capacitor
3
. After being kept closed (ON) for a predetermined time period, the switches S
1
and S
2
are turned off. Then, after a predetermined time has elapsed since the switches S
1
and S
2
were turned off, the first sample switch
4
(switches
4
a
and
4
b
) is turned on, whereby the charged voltage in the capacitor
3
, i.e., the voltage of the voltage source V
1
, is transferred to the polarity correction circuit
5
and the voltage measurement circuit
6
.
As a matter of course, a driving circuit of each switch and a contact point of the switch are kept separated. The first multiplexer
1
is not closed while the first sample switch
4
is closed, and the second multiplexer
2
is not closed while the first sample switch
4
is closed. Therefore, the voltage of the voltage source V
1
is insulatively measured, i.e., when the voltage of the voltage source V
1
is measured, the voltage source V
1
and the capacitor
3
are insulated.
During period P
2
, the switches S
2
and S
3
and the switches
4
a
and
4
b
are similarly turned on and off, and. during period P
3
, the switches S
3
and S
4
and the switches
4
a
and
4
b
are similarly turned on and off. In this way, as shown in
FIG. 4
, the multiplex voltage measurement apparatus
400
operates in a multiplex manner.
It should be noted in
FIG. 3
that the voltage value of an odd-numbered voltage source is inverted by the polarity correction circuit
5
so as to have the same polarity as that of the voltage value of an even-numbered voltage source before it is transmitted to the voltage measurement circuit
6
. An example of the polarity correction circuit
5
is shown in FIG.
5
.
The polarity correction circuit
5
shown in
FIG. 5
is a well-known absolute-value circuit. The polarity correction circuit
5
changes the polarity of a voltage to be input to an AD converter of the voltage measurement circuit
6
such that all of the voltages to be input to the AD converter have the same polarity. The polarity correction circuit
5
is effective for a unipolar voltage source such as a battery. It should be noted that the polarity correction circuit
5
is not limited to such an analog circuit, but may be a digital circuit which is independent of a polarity output bit of a bipolar input-type AD converter.
Referring again to
FIG. 3
, the multiplex voltage measurement apparatus
400
further includes an electric leakage detection circuit
7
. The electric leakage detection circuit
7
includes a second capacitor
10
, amplifiers
11
and
12
, a signal generation circuit
13
, and a level comparison circuit
14
. The electric leakage detection circuit
7
compares output levels of the amplifier
12
and the signal generation circuit
13
, thereby measuring the insulation impedance between the N voltage sources and the chassis.
However, in the conventional multiplex voltage measurement apparatus
400
having the above-described structure, if a line between the voltage detection terminal T
6
and the switch S
6
which is connected to the electric leakage detection circuit
7
is disconnected at position
15
(shown by “x” in FIG.
6
), a loop L (represented by a line with arrows in
FIG. 6
) is formed. As a result, an electric charge is stored in the first capacitor
3
, which should not be generated when the switches S
1
-S
6
are open, and accordingly, a voltage is generated therein. Therefore, breakage of the line connected to the voltage detection terminal T
6
, e.g., disconnection at position.
15
, cannot be detected.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a multiplex voltage measurement apparatus includes a multiplex voltage measurement section for measuring a voltage of each of N serially connected voltage sources and an electric leakage detection circuit for measuring an insulation impedance between the N voltage sources and a chassis, the multiplex voltage measurement section including, (N+1) voltage detection terminals connected to the N voltage sources, a first capacitor having a first terminal and a second terminal, a first multiplexer for selectively connecting any of odd-numbered voltage detection terminals among the (N+1) voltage detection terminals to the first terminal of the first capacitor, a second multiplexer for selectively connecting any of even-numbered voltage detection terminals among the (N+1) voltage detection terminals to the second terminal of the first capacitor, a voltage measurement circuit for measuring the voltage between the first terminal and the second terminal of the first capacitor, a first sample switch for connecting the first terminal and the second terminal of the first capacitor to the voltage measurement circuit, and a polarity correction circuit for changing the polarity of voltages of the N voltage sources such that the voltages of the odd-numbered voltage sources among the N voltage sources and the voltages of the even-numbered voltage sources among the N voltage sources have the same polarity, wherein the multiplex voltage measurement section measures the voltages of the N voltage sources by repeating a process in which the first and second multiplexers select one of the N voltage sources, and the first and second multiplexers are opened while the first sample switch is closed, and t
Le N.
LeRoux Etienne P
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