JP2010181168A - Battery module voltage detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the difference in frequency response between battery modules whose voltage is measured. <P>SOLUTION: A battery module voltage detector includes (m+1) resistors Rm connecting an input terminal connected to a voltage detecting terminal extracted from a connection point between modules and an output terminal connected to a voltage detector; and m capacitors connecting between terminals of each of the resistors. With this structure, the battery module voltage detector has a low-pass filter characteristic. The resistors have a substantially same resistance value, except a (1+m/2)-th resistor. The capacitors are disposed to connect an output terminal of the (1+m/2)-th resistor and an output terminal of an n-th resistor, and all of the capacitors have a substantially same capacitance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery module voltage detection device that individually detects the voltage of a battery module of an assembled battery.

A vehicle such as an electric vehicle or a hybrid vehicle is configured such that electric power is supplied to the motor by an assembled battery in which a large number of battery modules are connected in series. During this power supply, the voltage of the battery module, which is a series circuit of a plurality of cells, is constantly monitored.
As a method of detecting the voltage of the battery module of the assembled battery, the output voltage is charged to the same capacitor while sequentially switching the battery modules to be measured using a switch, and the voltage across the capacitor is measured using a differential amplifier. The method is known.

  By the way, it is known that when an analog output signal of a differential amplifier is converted into a digital signal by an A / D converter, an aliasing error occurs due to a noise component having a frequency equal to or higher than half the sampling frequency. In order to eliminate the aliasing error, it is desirable to apply an anti-aliasing filter between the measurement site and the switch.

  Patent Document 1 discloses an example of a voltage detection circuit in which an anti-aliasing filter including a low-pass filter including a resistor and a capacitor is provided for each battery module.

JP-A-2005-003618

  However, since the technique described in Patent Document 1 has a common resistor connected between the battery modules, the filter characteristics for each battery module are different, resulting in a difference in frequency response between the battery modules. Become. That is, if two resistors are used for each module, the frequency response becomes uniform, but if the resistors are shared between the modules and the number of components is reduced, the frequency response between the modules will be different. In that case, even if there is no difference in the voltage waveform of each battery module, the voltage waveform after passing through the filter is observed differently for each part. End up. In particular, Patent Document 1 corrects differences between modules based on circuit component constants. However, the constants must be accurately grasped, and errors caused by constant errors and constant fluctuations are large. Further, when the switch is configured with a switch having a predetermined delay time, for example, a photo MOS relay, the delay time is long, so that the sampling frequency of the switch cannot be increased. For this reason, a voltage detection device using a photo MOS relay has a problem that it is affected by noise of a relatively low frequency.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a battery module voltage detection device that can reduce a difference in frequency response between battery modules that detect voltage. .

  In order to solve the above-described problems, the present invention relates to voltages of the battery modules of the assembled battery [150] in which m (m is an even number) battery modules [Em] including at least one or more cells are connected in series. A voltage detection device [100] for a battery module that detects independently, the sum being drawn from (m−1) connection points between modules from the positive electrode of the highest module and the negative electrode of the lowest module. m + 1) voltage detection terminals, a filter circuit [Fi] having (m + 1) input terminals connected to each voltage detection terminal, and a voltage detected by being connected to (m + 1) output terminals of the filter circuit And (m + 1) resistors [Rm] for connecting between the input end and the output end, and connecting between the terminals of the resistors. Yo And m capacitors [Cm] are arranged in the low-pass filter circuit, and the resistance value of the resistor is substantially the same except for the (1 + m / 2) th resistor, and the capacitor Is the output terminal of the (1 + m / 2) th resistor and the output terminal of the nth (n is an integer from 1 to (m + 1)) except for (1 + m / 2). The capacitors are arranged to be connected, and all the capacitors have substantially the same capacitance. The numbers and symbols in square brackets [] are examples.

  ADVANTAGE OF THE INVENTION According to this invention, the difference of the frequency response between the battery modules which detect a voltage can be reduced.

It is a block diagram of the assembled battery voltage measurement circuit which is 1st Embodiment of this invention. It is a block diagram of the assembled battery voltage measuring apparatus in the case of m = 6. It is an equivalent circuit diagram of only an alternating voltage component for explaining filter characteristics. It is the equivalent circuit of one stage of RC filter which shows the frequency characteristic between adjacent output side terminals. It is a block diagram of the comparative example of this invention. It is a block diagram of the other comparative example of this invention. FIG. 6 is an AC equivalent circuit diagram of still another comparative example of the present invention.

(First embodiment)
FIG. 1 is a block diagram of an assembled battery voltage measurement circuit (battery module voltage detection device) according to the first embodiment of the present invention.
In FIG. 1, an assembled battery voltage measuring circuit 100 is a measurement object of an assembled battery 150 in which a plurality of battery modules E1 to Em / 2, E (m / 2 + 1) to Em (m is an even number) of the same standard are connected in series. , An anti-aliasing filter F1, a module voltage detection circuit U1, and a control circuit 10. The module voltage detection circuit U1 includes switch groups 20 (Sw0 to Sw (m / 2-1), Sw (m / 2), Sw (m / 2 + 1) to Swm), a capacitor C01, an output switch 30 (Sw _D1 , Sw _D2 ), and a differential amplifier DA1. Photo MOS relays are used for the switches Sw0 to Swm and the switches Sw _D1 and Sw _D2 . Further, the battery module of the assembled battery 150 and the anti-aliasing filter F1 are connected via input terminal terminals Fi0, Fi1,..., Fi6 (FIG. 2).

Here, since the voltage is too high to directly measure the entire voltage of the assembled battery 150 and the purpose is to measure the voltages of the individual battery modules E1, E2 to Em, the control circuit 10 switches the switch Sw0. ˜Swm is sequentially switched to measure the output side potential difference between adjacent resistors.
For example, when the battery module E1 is a measurement target, the pair of switches Sw0 and Sw1 are closed, and the voltage of the battery module E1 is charged to the capacitor C01. Then, the battery pack voltage measuring circuit 100 opens switch Sw0, Sw1 of the pair after a predetermined time has elapsed, closing the switch _Sw D1, _{Sw D2,} not shown voltage charged via the differential amplifier DA1 A Detect with / D converter. And the assembled battery voltage measurement circuit 100 detects the voltage of each battery module E1, E2-Em because the control circuit 10 performs this voltage detection sequentially from the battery module E1 to the battery module Em.

That is, the assembled battery voltage measurement circuit 100 is connected to the outputs of the battery modules E1, E2 to Em, and charges the capacitor C01 by closing the pair of switches Sw0 to Swm with the output-side potential difference between adjacent resistors. Let The assembled battery voltage measurement circuit 100 opens the pair of switches after a predetermined time, closes the switches Sw _D1 and Sw _D2 , and A / D converts the voltage charged in the capacitor C01 via the differential amplifier DA1. The voltage of the battery module is calculated from the detected value. During this time the switch _Sw0～Swm, control of switching the on-off timing of the Sw D1, _{Sw D2} is performed by the control circuit 10.

  The anti-aliasing filter (filter circuit) F1 which is a characteristic configuration of the present embodiment includes (m + 1) resistors having the same resistance value and m capacitors having the same capacitance, and each resistor is a battery module. The voltage detection terminal is connected between the switches Sw <b> 0 to Swm of the switch group 20. In addition, each capacitor C1, C2,..., C (m / 2), C (m / 2 + 1),..., C (m−1), Cm is the (1 + m / 2) th from the resistor R0. The resistor R (m / 2), which is a resistor, is connected between the output end side terminal and the output side terminals from the resistor R0 to the resistor Rm.

FIG. 2 is a configuration diagram of the assembled battery voltage measuring apparatus 100 when m = 6.
That is, the assembled battery voltage measuring apparatus 100 includes an anti-aliasing filter F1 and a module voltage detection circuit U1, and is configured to measure the module voltage of the assembled battery 150.
The assembled battery 150 includes battery modules E1, E2,..., E6 of the same standard connected in series, and the anti-aliasing filter (filter circuit) F1 is assembled through the input end terminals Fi0, Fi1,. , E6 are connected to 150 battery modules E1, E2,..., E6, and connected to inputs VC0, VC1,..., VC6 of the module voltage detection device U1 through output terminal terminals Fo0, Fo1,.

The anti-aliasing filter F1 includes seven resistors R0, R1,..., R6 having a resistance value r0 and six capacitors C1, C2,. .., R6 are respectively connected between the input end side terminals Fi0, Fi1,..., Fi6 and the output end side terminals Fo0, Fo1,..., Fo6, and one end of each of the capacitors C1, C2,. The resistor R3 is connected to the connection point between the output end side terminal Fo3.
The other ends of the capacitors C1, C2,..., C6 are the resistors R0, R1, R2, R4, R5, R6 and the output end side terminals Fo0, Fo1, Fo2, Fo4, Fo5, Fo6 except for the resistor R3. Are connected to each connection point. That is, the anti-aliasing filter F1 is configured to be symmetrical with respect to the high potential side and the low potential side with the resistor R3 as the center.

FIG. 3 is an equivalent circuit diagram of only the AC voltage component for explaining the filter characteristics of the assembled battery voltage measurement circuit 100 shown in FIG. That is, the battery modules E1, E2,..., E6 in FIG. 2 are replaced with AC voltage components V1, V2,.
The anti-aliasing filter F1 is configured to be symmetrical with respect to the high potential side and the ground side (low potential side) around the resistor R3. Here, if the AC voltage components V1, V2,..., V6 are the same voltage v0, the current i16 due to the AC voltage components V1 + V2 +... + V6 flows through the resistor R0, the capacitors C1, C6, and the resistor R6. A current i25 caused by the voltage component V2 + V3 + V4 + V5 flows through the resistor R1, capacitors C2, C5, and the resistor R5, and a current i34 caused by the AC voltage component V3 + V4 passes through the resistor R2, the capacitors C3, C4, and the resistor R4. Flowing. Therefore, no current flows through the resistor R3, and the resistor 3 can be replaced with a conducting wire (conductor wire).

Here, with Z0 = 1 / jωc0, the respective potentials of the output end terminals Fo0, Fo1, Fo2, Fo3, Fo4, Fo5 and Fo6 are calculated.
Since no current flows through the resistor R3, the potential of the output end side terminal Fo3 is equal to the potential of the input end side terminal Fi3 and is 3 · v0. Therefore, the potential v _Fo0 of the output end side terminal Fo0 is _expressed by the equation (1).
v _Fo0 = 3 / v0 + 3 · v0 · Z0 / (Z0 + r0) (1)
The potential v _Fo1 of the output end side terminal Fo1 is expressed by the equation (2).
v _Fo1 = 3 · v0 + 2 · v0 · Z0 / (Z0 + r0) (2)
The potential v _Fo2 of the output end side terminal Fo2 is expressed by the equation (3),
v _Fo2 = 3 · v0 + v0 · Z0 / (Z0 + r0) (3)
The potential v _Fo3 of the output end side terminal Fo3 is expressed by the equation (4),
v _Fo3 = 3 · v0 (4)
The potential v _Fo of the output end side terminal Fo4 is expressed by the equation (5).
v _Fo4 = 3 · v0−v0 · Z0 / (Z0 + r0) (5)
The potential v _Fo5 of the output end side terminal Fo5 is expressed by the equation (6),
v _Fo5 = 3 · v0-2 · v0 · Z0 / (Z0 + r0) (6)
Potential _{v Fo6} the output end side terminal Fo6 is represented by equation (7).
v _Fo6 = 3 · v0-3 · v0 · Z0 / (Z0 + r0) (7)

Next, when the potential difference between the output end side terminal Fo0 and the output end side terminal Fo1 is obtained, equation (8) is obtained.
v _Fo0 −v _Fo1 = v0 · Z0 / (Z0 + r0) (8)
Further, the potential difference between the output end side terminal Fo1 and the output end side terminal Fo2 is expressed by the following equation (9).
_{v Fo1 -v Fo2 = v0 · Z0} / (Z0 + r0) ··········· (9)
The potential difference between the output end side terminal Fo2 and the output end side terminal Fo3 is expressed by equation (10).
_{v Fo2 -v Fo3 = v0 · Z0} / (Z0 + r0) ·········· (10)
The potential difference between the output end side terminal Fo3 and the output end side terminal Fo4 becomes the equation (11).
v _Fo3 −v _Fo4 = v0 · Z0 / (Z0 + r0) (11)
The potential difference between the output end side terminal Fo4 and the output end side terminal Fo5 is expressed by equation (12).
v _Fo3 −v _Fo5 = v0 · Z0 / (Z0 + r0) (12)
The potential difference between the output end side terminal Fo5 and the output end side terminal Fo6 is expressed by equation (13).
v _Fo5 -v _Fo7 = v0 · Z0 / (Z0 + r0) (13)
That is, all potential differences between adjacent output terminals are the same value.

Therefore, an equivalent circuit showing the frequency characteristics between adjacent output side terminals is expressed by a single-stage RC filter shown in FIG. 4 and has a cutoff frequency f0 = 1 / (c0r0).
Specifically, in this equivalent circuit, a series circuit of a resistor having a resistance value r0 and a capacitor having a capacitance c0 is connected to both ends of the AC voltage component V0, and output voltages VC00 and VC01 are taken out from both ends of the capacitor. It has become.

For this reason, according to the configuration of the present embodiment, the voltage component detected between adjacent output side terminals is uniformly reduced and filtered with respect to the input, and an appropriate cutoff frequency is set with respect to the sampling frequency of the A / D converter. By setting, an aliasing error can be reduced. Moreover, since the voltage applied to the capacitors C1 and C6 at both ends is half of the previous voltage (V1 + V2 +... + V6), an inexpensive capacitor with a low withstand voltage can be used.
Further, even if the wiring connecting the assembled battery 150 and the anti-aliasing filter F1 has a resistance value that cannot be ignored, the resistance value r0 of the resistors R0, R1,..., R6 used for the anti-aliasing filter F1. However, if the value is sufficiently small, the influence of the wiring resistance remains slight.

  Next, a case where there is a difference in internal impedance due to deterioration of each battery module E1, E2,. In this case, the alternating current component of the potential difference between the two electrodes of the battery modules E1, E2,..., E6 is not uniform, current flows through the resistor R3, and the input end side terminal Fi3 and the output end side terminal Fo3 A potential difference occurs between them, resulting in measurement errors. However, this error can be reduced by using the resistor R3 as a conductor wire and making the resistance value of the resistor R3 sufficiently small and substantially zero, thereby suppressing the potential difference generated and reducing the measurement error.

(Comparative Example 1)
FIG. 5 is a configuration diagram of Comparative Example 1 in which the ground point of the negative electrode of the battery pack 150, that is, the negative electrode of the battery module E6, and the ground points of all the capacitors C1, C2,.
2, one end of each of the capacitors C1, C2,..., C6 is connected to one end of the resistor R3. However, the anti-aliasing filter F2 of the comparative example 1 in FIG. A and grounding points B of all capacitors C1, C2,..., C6 are connected by a conductor wire having a resistance value r.
In this case, the sum (i1 + i2 +... + I6) of the alternating current components i1, i2,..., I6 of the current flowing through the capacitors C1, C2,. The potential of the output end side terminal Fo6 fluctuates, resulting in a measurement error.

(Comparative Example 2)
Comparative Example 2 will be described with reference to FIG. This comparative example 2 is an example in which one point is grounded to the point A of the negative electrode of the assembled battery 150 in order to avoid the potential fluctuation generated in the conductor wire having the resistance value r of the comparative example 1.
That is, one end of the capacitor C1 is connected to the resistance component r1 of the conductor wire and the point A via the connector CN6, and similarly, one end of the capacitors C2, C3, C4, C5, C6 is connected to the resistance components r2, r3, r4. It is connected to point A via r5, r6 and connectors CN7, CN8, CN9, CN10, CN11. Also, the conductor wire is connected from the point A to the output end side terminal Fo6 via the connector CN12 and the resistance component r7.

  As a result, currents i1, i2, i3, i4, i5, and i6 flowing in the capacitors C1, C2, C3, C4, C5, and C6 flow in the resistance components r1, r2, r3, r4, r5, and r6, respectively. It does not flow to r7. For this reason, the output end side terminal Fo6 is not subjected to potential fluctuation. However, there is a problem that the connectors CN7, CN8, CN9, CN10, CN11 increase.

(Comparative Example 3)
An example of another circuit in which the filter characteristics between adjacent terminals of an even number of battery modules E1, E2, E3, and E4 are equal will be described with reference to FIG.
The anti-aliasing filter F4 includes resistors R0, R1, R2, R3, R4 and capacitors C01, C14, C03, C34. The assembled battery 155 includes battery modules E1, E2, E3, and E4 connected in series, and the battery modules E1, E2, E3, and E4 generate AC voltage components V1, V2, V3, and V4, respectively.
One end of a resistor R0 is connected to the positive electrode of the battery module E1, one end of the resistor R1 is connected to a connection point between the battery module E1 and the battery module E2, and a connection point between the battery module E2 and the battery module E3 is connected. One end of the resistor R2 is connected, one end of the resistor R3 is connected to the connection point between the battery module E3 and the battery module E4, and one end of the resistor R4 is connected to the negative electrode of the battery module E4.
Also, output terminal terminals Fo0, Fo1, Fo2, Fo3, and Fo4 are connected to the other ends of the resistors R0, R1, R2, R3, and R4, respectively.

  A capacitor C01 is connected between the other end of the resistor R0 and the other end of the resistor R1, and a capacitor C14 is connected between the other end of the resistor R1 and the other end of the resistor R4. A capacitor C03 is connected between the other end of the resistor R0 and the other end of the resistor R3, and a capacitor C34 is connected between the other end of the resistor R3 and the other end of the resistor R4.

Here, for example, when only the voltage V1 of the battery module E1 changes, the voltage applied to the capacitors C01 and C03 changes, so that current flows through the capacitors C01 and C03, respectively. For this reason, there is a problem that the potential of the output terminal changes and the voltage observation values vo42, vo43, and vo44 vary.
However, according to the configuration of FIG. 2, when the voltage of the battery module E1 fluctuates, a fluctuating current flows only to the resistor R3 via the capacitor C1, and the other resistors R1, R2, R4, R5, R6 No fluctuating current flows through At this time, if the resistor R3 is formed of a conductor wire, no potential fluctuation occurs in any of the output side terminals.

  Even in the configuration of FIG. 6, potential fluctuation does not occur at terminals other than the output end side terminal Fo0. That is, when the voltage of the battery module E1 fluctuates, only a fluctuating current flows through the resistor R0, the capacitor C1, the resistance component r1 of the conductor wire, and the connector CN6, and the resistance component r2 of the other conductor wire. , R3,..., R7, no fluctuating current flows. Therefore, the output end side terminals Fo1, Fo2,...

10 control circuit 20 switch group 30 output switch 100 assembled battery voltage measuring device (battery module voltage detecting device)
150 battery pack F1 anti-aliasing filter (filter circuit)
U1 Module voltage detection circuit R0, R1 to Rm Resistors C1 to Cm, C01 Capacitor DA1 Differential amplifier E1 to Em Battery modules V1, V2,..., Vn AC voltage components Sw0, Sw1, ..., Swm, Sw _D1 , Sw _D2 Switch r0 resistance c0 capacitance

Claims (2)

A battery module voltage detection device for independently detecting the voltage of each battery module of an assembled battery in which m (m is an even number) battery modules including at least one cell are connected in series,
A total of (m + 1) voltage detection terminals drawn from the positive electrode of the highest module, the negative electrode of the lowest module, and (m−1) connection points between the modules;
A filter circuit in which (m + 1) input terminals are connected to each voltage detection terminal;
A voltage detection circuit for detecting a voltage connected to (m + 1) output terminals of the filter circuit;
The filter circuit is
(M + 1) resistors connecting between the input end and the output end;
M capacitors so as to connect the terminals of the resistors,
Is a low-pass filter circuit arranged,
The resistance values of the resistors are substantially the same except for the (1 + m / 2) th resistor,
The capacitor includes an output terminal of the (1 + m / 2) th resistor,
n (n is an integer from 1 to (m + 1) except for (1 + m / 2)) is arranged to connect to the output terminal of the first resistor.
All the said capacitors have the substantially same capacitance. The battery module voltage detection apparatus characterized by the above-mentioned. The resistance value of the (1 + m / 2) th resistor is smaller than the resistance value of the other resistors, or the (1 + m / 2) th resistor is replaced with a conductive wire. The battery module voltage detection apparatus according to claim 1.

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