JP2002291167A - Flying capacitor battery pack voltage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flying capacitor battery pack voltage detector capable of suppressing increase in a battery voltage measuring error caused by signal voltage attenuation. SOLUTION: The voltage of battery module voltages VB1 to VB8 are sequentially loaded into a flying capacitor 5 through current limiter resistors R1 to R9 and outputted to a differential voltage detection circuit 11 through sampling switches 6, 7 on the output side. A data processing circuit 4 loads measuring data consisting of a potential difference in the flying capacitor 5 in which prescribed battery module voltage is loaded several times in different timings to compute voltage attenuation characteristics. Based on the voltage attenuation characteristics, the circuit 4 estimates the potential difference in the flying capacitor 5 immediately after the voltage of the battery module is loaded into the flying capacitor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flying capacitor type assembled battery voltage detecting device, and more particularly to a flying capacitor type assembled battery voltage detecting device used for a vehicle assembled battery.

[0002]

2. Description of the Related Art For example, in a hybrid vehicle, an electric vehicle, a fuel cell vehicle, and the like, an assembled battery including a secondary battery and a fuel cell is constituted by a large number of battery modules connected in series with each other. It is configured by connecting in series.

Since the potential of each battery module is high and different from each other, the voltage measurement of each battery module is performed by a flying capacitor type assembled battery voltage detection that can insulate each battery module from the reference potential of a differential voltage detection circuit on the output side. The device is preferred. However, equipping each battery module with a voltage detection circuit increases the size of the device and causes problems of offset errors and voltage amplification factors between the differential voltage detection circuits. A flying capacitor type assembled battery voltage detector with a multiplexer that reduces the required number of flying capacitors and differential voltage detection circuits by sampling the voltage of each battery module in time sequence and reading the voltage into a common flying capacitor is suitable.

[0004]

However, in the above-described conventional flying capacitor type voltage detecting circuit, there is a possibility that the leakage current of the flying capacitor or the sampling switch may increase due to aging. When the leakage current increases, the storage voltage read from the battery module by the flying capacitor attenuates before the voltage detection circuit measures it, and an accurate battery module voltage cannot be obtained, and the battery state is erroneously determined. Resulting in.

[0005] This problem is particularly caused when the output voltage of the differential voltage detection circuit is sampled and held by, for example, an A / D converter, and the output side sampling switch is turned on to read charges from the flying capacitor to the differential voltage detection circuit. It becomes even more serious because it is delayed for a certain period of time from when it started.

More specifically, when the output-side sampling switch is turned on, the signal voltage between the input terminals of the differential voltage detection circuit starts to increase, but peaks after a certain time delay due to the electrical resistance of the output-side sampling switch. Reaches the value. When a discharge resistor or the like is connected to the input terminal of the differential voltage detection circuit, the voltage decreases from the above-mentioned peak value over time due to discharge. In any case, when a discharge resistor or the like is connected to the input terminal of the differential voltage detection circuit, the decay of the stored charge of the flying capacitor through the discharge resistor cannot be avoided, and the A / D converter sample Since the hold is delayed, the influence of the voltage loss due to the discharge resistance cannot be avoided, and the resistance value change of the discharge resistance (temporal or temporal)
The fluctuation of the voltage decay rate caused by the measurement results in a measurement error.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a flying capacitor type battery pack voltage detecting device capable of suppressing an increase in battery voltage measurement error due to signal voltage attenuation.

[0008]

According to a first aspect of the present invention, there is provided a flying capacitor type battery pack voltage detecting device for detecting a potential difference between a pair of input terminals, a flying capacitor, and a storage voltage of the flying capacitor. And an output-side sampling switch for applying a voltage between the pair of input terminals of the differential voltage detection circuit, and each electrode terminal of an assembled battery composed of a number of battery modules connected in series to each other, sequentially connected to both ends of the flying capacitor. And a data processing circuit for processing an output voltage of the differential voltage detection circuit, wherein the data processing circuit comprises a multiplexer for sequentially applying the voltage of each battery module to the flying capacitor, and a data processing circuit for processing an output voltage of the differential voltage detection circuit. Said flying which reads the voltage of said predetermined battery module It is characterized in that measurement data consisting of the potential difference of the capacitor is read a plurality of times at different timings, and the potential difference of the flying capacitor immediately after the voltage of the battery module is read into the flying capacitor is estimated based on the measurement data. .

That is, in the present invention, the signal voltage stored in the flying capacitor is read out a plurality of times at different timings, thereby estimating the voltage decay rate of an output circuit system such as a flying capacitor. Since the stored voltage of the flying capacitor is estimated immediately after voltage reading from the module to the flying capacitor, accurate battery voltage detection is possible even if the voltage decay rate of the circuit system changes due to deterioration over time or varies. Become.

A flying capacitor type battery pack voltage detecting device according to a second aspect of the present invention includes a differential voltage detecting circuit for detecting a potential difference between a pair of input terminals, a flying capacitor, and a storage voltage of the flying capacitor. An output-side sampling switch to be applied between the pair of input terminals of the circuit, and each electrode terminal of a battery pack composed of a number of battery modules connected in series to each other, sequentially connecting both ends of the flying capacitor to each of the battery modules. In a flying capacitor type battery pack voltage detecting device comprising: a multiplexer for sequentially applying a voltage to the flying capacitor; and a data processing circuit for processing an output voltage of the differential voltage detecting circuit, the data processing circuit includes a predetermined battery. The potential of the flying capacitor reading the voltage of the module The measurement data consisting of is read a plurality of times at different timings, and based on each measurement data, an attenuation rate related value that is data related to the attenuation rate of the potential difference of the flying capacitor is calculated, and the attenuation rate related value is a predetermined value. It is characterized in that a circuit failure is determined when the threshold value is exceeded.

That is, according to the present invention, the signal voltage stored in the flying capacitor is read out a plurality of times at different timings to determine the voltage attenuation rate (related numerical data) of the output circuit system such as the flying capacitor,
If the voltage decay rate exceeds a predetermined threshold, it is determined that the circuit is defective and an alarm is issued.

Thus, it is possible to solve the problem that the battery voltage data having a large error due to the failure of the circuit system is continuously used without knowing it.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the flying capacitor type assembled battery voltage detecting device of the present invention will be described below in detail with reference to the following embodiments. However, the present invention is not limited to the configuration of the following embodiment, and it is obvious that the present invention can be configured using a replaceable known circuit.

[0014]

[Embodiment 1] An embodiment of a battery pack voltage detecting apparatus to which the present invention is applied will be described with reference to a circuit diagram shown in FIG. (Circuit Configuration) The battery pack 1 includes eight battery modules VB1.
To VB8 in series. Each battery module VB1
To VB8 are each formed by connecting an equal number of unit cells in series. R1 to R9 are current limiting resistive elements, 2 is a multiplexer, 3 is an A / D converter, 4 is a microcomputer built-in controller, 5 is a flying capacitor, 6 and 7 are output side sampling switches, 8 to 10 are resistive elements, 11 is This is a differential voltage detection circuit.

The multiplexer 2 includes a current limiting resistor R
1 to R9 and the two ends of the flying capacitor 5 are sequentially connected, so that the voltage of each battery module VB1 to VB8 is
Can be read.

The output side sampling switch 6 connects one end of the flying capacitor 5 to the first input terminal of the differential voltage detecting circuit 3 through the input resistance element 8, and the sampling switch 7 connects the other end of the flying capacitor 5 to the differential terminal. It is connected to the second input terminal of the voltage detection circuit 3.

The resistance element 9 connects both input terminals of the differential voltage detection circuit 9, and the resistance element 10 connects the other input terminal of the differential voltage detection circuit to a reference potential source Vref.

The output voltage of the differential voltage detection circuit 11 is A / D
The signal is converted into a digital signal by the converter 12 and output to the controller 13. Sampling switches 3, 4,
The sampling switches 6 and 7 and the multiplexer 2 are opened and closed at the timing determined by the controller 13.

(Operation) Next, a normal voltage detection operation of the battery modules VB1 to VB8 by this circuit will be described below.

First, the multiplexer 2 is controlled to read the voltage of the battery module VB 1 into the flying capacitor 5.

Next, the sampling switch of the multiplexer 2 is turned off, the sampling switches 6 and 7 are turned on for a predetermined period, and the potential difference of the flying capacitor C1 is read into the differential voltage detection circuit 3.

As a result, the stored voltage of the flying capacitor 5 is divided by the resistance elements 8 and 9 and input to the differential voltage detection circuit 11. The differential voltage detection circuit 11 impedance-converts and amplifies the input voltage with reference to a reference potential Vref (here, +2.5 V),
Output to The A / D converter 3 converts the input voltage into a digital signal at a timing controlled by the controller 4 and transmits the digital signal to the controller 4.

The input voltage sample / hold timing of the A / D converter 3 will be described below with reference to the timing chart of FIG.

First, the sampling switch of the multiplexer 2 is turned on, and one of the battery module voltages is read into the flying capacitor 5. After a predetermined time from the start of reading (which is set to be longer than the CR time constant determined by the electric resistance of the current limiting resistor and the capacitance of the flying capacitor 5), the storage voltage Vc of the flying capacitor 5 substantially reaches the battery module voltage Vm. At time t0, the output side sampling switches 6, 7 are turned on.

Since the output-side sampling switches 6 and 7 are photo MOS transistors, it takes time for the on-resistance to reach the minimum value, and there is charging such as parasitic capacitance. Vs reaches the peak value at a time point t1 about 1 ms later. Therefore, at this time point t1, the A / D converter 3 samples and holds the output voltage of the differential voltage detection circuit 11.

It is to be noted that Vm shown in FIG. 2 indicates that the channel resistance of the output side sampling switches 6 and 7 is R,
Is R8, the resistance value of the resistance element 9 is R9, and the storage voltage of the flying capacitor 5 is Vmo.
mo.R9 / (R + R8 + R9), that is, the storage voltage V
mo is the theoretical partial pressure. Even during the period from the time point t0 to the time point t1, the stored energy is further consumed by the leakage current of the flying capacitor 5 and the sampling switch as the heating of the resistance elements 8 and 9, and the stored voltage of the flying capacitor 5 is reduced accordingly. Further, as time elapses after the time point t1, heat generation of the resistance elements 8 and 9 causes
Furthermore, since the flying capacitor 5 consumes stored energy due to the leakage current of the flying capacitor 5 and the sampling switch, the stored voltage of the flying capacitor 5 decreases with time (see FIG. 2).

(Estimation of Storage Voltage at Time t0) In the sample hold of the A / D converter 3 at the time t1 described above, at the time t0 (in this embodiment, the time at which the sampling switch of the multiplexer 2 is turned off and the output side sampling switch 6). , 7 (onset start time) cannot be detected.

Therefore, in this embodiment, the A / D converter 3 performs a sample and hold operation at time points t2, t3, and t4 after time point t1 and transmits measurement data to the controller 4. The controller 4 estimates the voltage decay characteristic straight line S shown in FIG. 2 from the total of four measurement data obtained for one battery module voltage Vm, extends the straight line S, and accumulates the storage voltage Vs of the flying capacitor 5 at time t0. Is estimated.

This makes it possible to correct the loss of stored energy during the period from the time when the multiplexer 2 is turned off or the time when the output-side sampling switches 6 and 7 are turned on to the time when the A / D converter 3 is sampled and held.

Next, the output side sampling switches 6 and 7
Is turned off, and the next battery module voltage is read into the flying capacitor 5 under the control of the multiplexer 2.

The above-mentioned correction can be applied to the measurement data of each battery module voltage by calculating the above-mentioned voltage decay characteristic straight line S. Therefore, the normal battery module voltage measurement is performed only at the time t1, and the above-mentioned correction is performed. The correction of the voltage attenuation characteristic line s may be performed, for example, at the time of starting the vehicle.

(Determining Deterioration of Voltage Detection Circuit System) Next, a process of determining the degree of deterioration of the insulation resistance of a circuit element such as the flying capacitor 5 will be described with reference to FIG.

In FIG. 2, S2 is the current voltage attenuation characteristic straight line obtained by the above method, L2 is the current true voltage attenuation characteristic, and S1 is the voltage attenuation characteristic straight line at the start of operation obtained by the above method. (Initial characteristic line), and L1 is the initial characteristic of the true voltage decay characteristic.

The controller 4 including the microcomputer, when the slope of the current voltage decay characteristic line S2 obtained by the above method exceeds a predetermined threshold value larger than the slope of the initial characteristic straight line S1, determines that the deterioration of the circuit system has occurred. Judge that it is serious and output an alarm.

(Modification) Instead of calculating the voltage decay characteristic line S2 and the slope rate, for example, measurement data at a time t4 at a predetermined capacity of the battery pack 1, for example, is stored in advance at a predetermined time at the predetermined capacity. By comparing with a threshold value, it is also possible to determine the deterioration of the circuit system. That is, by ignoring the fluctuation of the terminal voltage due to the battery deterioration, the insulation deterioration of the circuit system can be determined more easily.

It is apparent that the above-described characteristic calculation and deterioration determination itself can be easily executed by a program stored in a microcomputer, and a detailed description of those programs will be omitted.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a flying capacitor type assembled battery voltage detecting device according to a first embodiment.

FIG. 2 is a timing chart showing a time change of an input voltage (or an output voltage) of the differential voltage detection circuit of FIG. 1;

FIG. 3 is a timing chart showing a time change of an input voltage (or an output voltage) of the differential voltage detection circuit at the start of operation of the circuit of FIG. 1 and at the time of deterioration thereof.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 battery pack 2 multiplexer 3 A / D converter 4 controller (data processing circuit) 5 flying capacitor 6 output sampling switch 7 output sampling switch VB1 to VB8 Battery module 8 to 10 Resistance element

Claims (2)

[Claims] A differential voltage detection circuit for detecting a potential difference between a pair of input terminals; a flying capacitor; and an output for applying a stored voltage of the flying capacitor between the pair of input terminals of the differential voltage detection circuit. A side sampling switch, a multiplexer that sequentially connects each electrode terminal of the battery pack composed of a number of battery modules connected in series to both ends of the flying capacitor, and sequentially applies the voltage of each battery module to the flying capacitor, A data processing circuit for processing the output voltage of the differential voltage detection circuit, wherein the data processing circuit comprises: a potential difference of the flying capacitor which reads a predetermined voltage of the battery module. Measurement data consisting of multiple times at different timings A flying capacitor type assembled battery voltage detecting device, comprising: estimating a potential difference of the flying capacitor immediately after reading a voltage of the battery module into the flying capacitor based on the measurement data. 2. A differential voltage detection circuit for detecting a potential difference between a pair of input terminals, a flying capacitor, and an output for applying a stored voltage of the flying capacitor between the pair of input terminals of the differential voltage detection circuit. A side sampling switch, a multiplexer that sequentially connects each electrode terminal of the battery pack composed of a number of battery modules connected in series to both ends of the flying capacitor, and sequentially applies the voltage of each battery module to the flying capacitor, A data processing circuit for processing the output voltage of the differential voltage detection circuit, wherein the data processing circuit comprises: a potential difference of the flying capacitor which reads a predetermined voltage of the battery module. Measurement data consisting of multiple times at different timings Reading, calculating an attenuation rate related value that is data related to the attenuation rate of the potential difference of the flying capacitor based on the measurement data, and determining that the circuit is defective if the attenuation rate related value exceeds a predetermined threshold value. A flying capacitor type assembled battery voltage detecting device.