Voltage monitoring circuit

Abstract

Determine whether or not there is an abnormality in the voltage divider circuit. [Solution] The voltage monitoring circuit 20 comprises a voltage divider circuit 30 and a processor 70. The voltage divider circuit 30 comprises a first overvoltage detection voltage divider resistor 31, a second overvoltage detection voltage divider resistor 32, a first voltage measurement voltage divider resistor 34, and a second voltage measurement voltage divider resistor 35. The connection point between the first overvoltage detection voltage divider resistor 31 and the second overvoltage detection voltage divider resistor 32 is defined as the first connection point 33. The connection point between the first voltage measurement voltage divider resistor 34 and the second voltage measurement voltage divider resistor 35 is defined as the second connection point 36. The processor 70 determines that there is an abnormality in the voltage divider circuit 30 if the difference between the input voltage measured based on the voltage input from the first connection point 33 and the input voltage measured based on the voltage input from the second connection point 36 is greater than or equal to a threshold.

Description

Technical Field

[0001] This disclosure relates to a voltage monitoring circuit.

Background Art

[0002] The voltage monitoring circuit disclosed in Patent Document 1 monitors the output voltage of a DC / DC converter. A voltage divided by a voltage dividing circuit is input to the voltage monitoring circuit. The voltage monitoring circuit monitors the output voltage by determining whether the input voltage exceeds a threshold value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an abnormality occurs in the voltage dividing circuit, the voltage monitoring circuit cannot monitor the output voltage.

Means for Solving the Problems

[0005] A voltage monitoring circuit that solves the above problems comprises a voltage divider circuit connected to a power supply, an overvoltage determination unit that determines whether the input voltage input from the power supply is an overvoltage, a first filter provided between the voltage divider circuit and the overvoltage determination unit, a voltage measurement unit that measures the input voltage input from the power supply, and a second filter provided between the voltage divider circuit and the voltage measurement unit, wherein the voltage divider circuit comprises a first overvoltage detection voltage divider resistor connected to the power supply, a second overvoltage detection voltage divider resistor connected in series with the first overvoltage detection voltage divider resistor, a first voltage measurement voltage divider resistor connected to the power supply, and a second voltage measurement voltage divider resistor connected in series with the first voltage measurement voltage divider resistor, and the overvoltage determination unit measures the first overvoltage detection voltage via the first filter The voltage measurement unit determines whether the input voltage from the power supply is an overvoltage by comparing the voltage input from the first connection point, which is the connection point between the voltage resistor and the second overvoltage detection voltage divider resistor, with a reference value. The voltage measurement unit measures the input voltage from the power supply based on the voltage input from the first connection point via the first filter, and measures the input voltage from the power supply based on the voltage input from the second connection point, which is the connection point between the first voltage measuring voltage divider resistor and the second voltage measuring voltage divider resistor, via the second filter. If the difference between the input voltage measured based on the voltage input from the first connection point and the input voltage measured based on the voltage input from the second connection point is greater than or equal to a threshold value, the voltage measurement unit determines that there is an abnormality in the voltage divider circuit.

[0006] If a malfunction occurs in the voltage divider circuit, a difference will arise between the input voltage measured based on the voltage input from the first connection point and the input voltage measured based on the voltage input from the second connection point. Therefore, if the difference between the input voltage measured based on the voltage input from the first connection point and the input voltage measured based on the voltage input from the second connection point is greater than or equal to a threshold, it can be determined that a malfunction has occurred in the voltage divider circuit.

[0007] In the above-described voltage monitoring circuit, wiring extending from the first filter and the overvoltage determination unit may be connected to the voltage measurement unit so that the voltage from which noise has been removed by the first filter is input.

[0008] With respect to the above-mentioned voltage monitoring circuit, the voltage measurement unit may notify the higher-level control unit if it determines that an abnormality has occurred in the voltage divider circuit. [Effects of the Invention]

[0009] According to the present invention, it is possible to determine whether or not an abnormality has occurred in the voltage divider circuit. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a circuit diagram of a voltage monitoring circuit. [Modes for carrying out the invention]

[0011] One embodiment of a voltage monitoring circuit will be described. As shown in Figure 1, the vehicle 10 includes a power supply 11, a power converter 12, a higher-level control device 13, and a voltage monitoring circuit 20.

[0012] Power source 11 is a DC power source. Power source 11 is, for example, a battery. The power converter 12 converts the power input from the power source 11 and outputs it. The power converter 12 is, for example, an inverter that converts DC power to AC power and outputs it. The power output from the power converter 12 is supplied to, for example, a motor. The motor is, for example, the motor of an electric compressor.

[0013] <Voltage monitoring circuit> The voltage monitoring circuit 20 includes a first input terminal 21 and a second input terminal 22. The first input terminal 21 is connected to the positive terminal of the power supply 11. The second input terminal 22 is connected to the negative terminal of the power supply 11.

[0014] The voltage monitoring circuit 20 includes a voltage divider circuit 30, a first filter 40, a control circuit 50, a second filter 60, a processor 70, and wiring 80. The voltage divider circuit 30 includes two overvoltage detection voltage divider resistors 31 and 32, and two voltage measurement voltage divider resistors 34 and 35. The two overvoltage detection voltage divider resistors 31 and 32 include a first overvoltage detection voltage divider resistor 31 connected to the power supply 11 via a first input terminal 21, and a second overvoltage detection voltage divider resistor 32 connected in series with the first overvoltage detection voltage divider resistor 31. The resistance value R1 of the first overvoltage detection voltage divider resistor 31 and the resistance value R2 of the second overvoltage detection voltage divider resistor 32 may be the same or different.

[0015] The two voltage measuring voltage divider resistors 34 and 35 include a first voltage measuring voltage divider resistor 34 connected to the power supply 11 via a first input terminal 21, and a second voltage measuring voltage divider resistor 35 connected in series with the first voltage measuring voltage divider resistor 34. The resistance value R3 of the first voltage measuring voltage divider resistor 34 and the resistance value R4 of the second voltage measuring voltage divider resistor 35 may be the same or different.

[0016] The first filter 40 is a low-pass filter. The first filter 40 comprises a first resistor 41 and a first capacitor 42. The first resistor 41 is connected to a first connection point 33, which is the connection point between a first overvoltage detection voltage divider resistor 31 and a second overvoltage detection voltage divider resistor 32. The first capacitor 42 is provided between the first resistor 41 and ground.

[0017] The control circuit 50 is, for example, an integrated circuit. The control circuit 50 controls the power converter 12 and detects overvoltage. The control circuit 50 controls the power converter 12 by, for example, outputting a drive signal to the drive circuit that drives the power converter 12.

[0018] A first filter 40 is connected to the control circuit 50. More specifically, a first resistor 41 is connected to the control circuit 50. As a result, a voltage is input from the first connection point 33 to the control circuit 50 via the first filter 40, which is installed between the voltage divider circuit 30 and the control circuit 50. The voltage V1 input from the first connection point 33 is the voltage divided by the first overvoltage detection voltage divider resistor 31 and the second overvoltage detection voltage divider resistor 32. The voltage V1 input from the first connection point 33 can be expressed as resistance value R2 × input voltage Vin / (resistance value R1 + resistance value R2). The input voltage Vin is the input voltage input from the power supply 11.

[0019] The control circuit 50 determines whether the input voltage Vin is overvoltage by comparing voltage V1 with a reference value. Overvoltage is a state in which the input voltage Vin exceeds the allowable value. Voltage V1 is lower than the input voltage Vin due to voltage division. The reference value should be set based on resistance values ​​R1 and R2 so that it is possible to determine from voltage V1 whether the input voltage Vin exceeds the allowable value. If, as a result of comparing voltage V1 with the reference value, voltage V1 is higher than the reference value, the control circuit 50 determines that the input voltage Vin is overvoltage. If, as a result of comparing voltage V1 with the reference value, voltage V1 is less than or equal to the reference value, the control circuit 50 determines that the input voltage Vin is not overvoltage. Thus, the control circuit 50 performs overvoltage detection. When the control circuit 50 determines that the input voltage Vin is overvoltage, it stops the power converter 12. The control circuit 50 also notifies the processor 70 that the input voltage Vin is overvoltage. The control circuit 50 is an example of an overvoltage determination unit.

[0020] The second filter 60 is a low-pass filter. The second filter 60 comprises a second resistor 61 and a second capacitor 62. The second resistor 61 is connected to a second connection point 36, which is the connection point between the first voltage measuring voltage divider resistor 34 and the second voltage measuring voltage divider resistor 35. The second capacitor 62 is provided between the second resistor 61 and ground. The cutoff frequency of the second filter 60 is lower than the cutoff frequency of the first filter 40. Therefore, the time constant of the first filter 40 is smaller than the time constant of the second filter 60.

[0021] The processor 70 is, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit) or a DSP (Digital Signal Processor). The processor 70 communicates with the upper control device 13, issues commands to the control circuit 50, and measures the input voltage Vin.

[0022] The processor 70 transmits and receives information through communication with the upper control device 13. For example, the processor 70 receives commands from the upper control device 13. The processor 70 transmits the states of the power conversion device 12 and the voltage monitoring circuit 20 to the upper control device 13.

[0023] The processor 70 issues commands to the control circuit 50 according to commands from the upper control device 13. The commands to the control circuit 50 are, for example, drive commands for the power conversion device 12 or stop commands for the power conversion device 12. The control circuit 50 controls the power conversion device 12 according to commands from the processor 70.

[0024] The wiring 80 connects the location between the voltage dividing circuit 30 and the control circuit 50 and the processor 70. Specifically, the wiring 80 connects the connection point between the first resistor 41 and the first capacitor 42 and the processor 70. Thereby, the voltage V1 is input from the first connection point 33 to the processor 70 through the first filter 40 provided between the voltage dividing circuit 30 and the control circuit 50. The first filter 40 also serves as a filter provided between the first connection point 33 and the processor 70. The wiring 80 extending from between the first filter 40 and the control circuit 50 is connected to the processor 70 so that a voltage from which noise has been removed by the first filter 40 is input to the processor 70.

[0025] <Abnormal determination of voltage dividing circuit> The processor 70 measures the input voltage Vin based on the voltage V1. The input voltage Vin can be expressed as voltage V1 × (resistance R1 + resistance R2) / resistance R2. By storing resistance R1 and resistance R2 in a memory unit that the processor 70 can read, the processor 70 can measure the input voltage Vin based on the voltage V1.

[0026] A second filter 60 is connected to the processor 70. More specifically, a second resistor 61 is connected to the processor 70. As a result, a voltage is input to the processor 70 from the second connection point 36 via the second filter 60, which is located between the voltage divider circuit 30 and the processor 70. The voltage V2 input from the second connection point 36 is the voltage divided by the first voltage measuring voltage divider resistor 34 and the second voltage measuring voltage divider resistor 35. The voltage V2 input from the second connection point 36 can be expressed as resistance value R4 × input voltage Vin / (resistance value R3 + resistance value R4).

[0027] The processor 70 measures the input voltage Vin based on the voltage V2. The input voltage Vin can be expressed as voltage V2 × (resistance R3 + resistance R4) / resistance R4. By storing the resistance values ​​R3 and R4 in a memory unit that the processor 70 can read, the processor 70 can measure the input voltage Vin based on the voltage V2.

[0028] The processor 70 determines whether or not there is an abnormality in the voltage divider circuit 30 by comparing the input voltage Vin measured based on the voltage V1 input from the first connection point 33 with the input voltage Vin measured based on the voltage V2 input from the second connection point 36. The input voltage Vin measured based on the voltage V1 input from the first connection point 33 is appropriately designated as the first input voltage. The input voltage Vin measured based on the voltage V2 input from the second connection point 36 is appropriately designated as the second input voltage.

[0029] The processor 70 determines that there is an abnormality in the voltage divider circuit 30 if the difference between the first input voltage and the second input voltage is greater than or equal to a threshold. The processor 70 determines that there is no abnormality in the voltage divider circuit 30 if the difference between the first input voltage and the second input voltage is less than the threshold. The processor 70 may also use the difference between the first input voltage and the second input voltage as the difference between the average value obtained by measuring the first input voltage multiple times and the average value obtained by measuring the second input voltage multiple times.

[0030] An abnormality in the voltage divider circuit 30 is a short circuit or open circuit in at least one of the two overvoltage detection voltage divider resistors 31 and 32, and the two voltage measurement voltage divider resistors 34 and 35. When a short circuit or open circuit occurs in at least one of the two overvoltage detection voltage divider resistors 31 and 32, and the two voltage measurement voltage divider resistors 34 and 35, a difference occurs between the first input voltage and the second input voltage. Therefore, by comparing the first input voltage and the second input voltage, the processor 70 can detect an abnormality in the voltage divider circuit 30. The threshold value should be greater than the difference between the first input voltage and the second input voltage that may occur when there is no abnormality in the voltage divider circuit 30.

[0031] If the processor 70 determines that an abnormality has occurred in the voltage divider circuit 30, it sends a stop command to the control circuit 50, thereby stopping the operation of the power converter 12. The processor 70 notifies the higher-level control unit 13 that an abnormality has occurred. The higher-level control unit 13 may also notify the user of the vehicle 10 that an abnormality has occurred. The processor 70 is an example of a voltage measurement unit.

[0032] [Operation of this embodiment] The control circuit 50 controls the power converter 12. The power converter 12 converts the power input from the power supply 11 and outputs it. The control circuit 50 detects overvoltage by comparing the voltage V1 input from the first connection point 33 with a reference value, and notifies the processor 70 if an overvoltage is detected. The processor 70 measures the input voltage Vin from the voltage V2 input from the second connection point 36.

[0033] If a short circuit or open circuit occurs in the overvoltage detection voltage divider resistors 31 and 32, the input voltage Vin will not be divided by the two overvoltage detection voltage divider resistors 31 and 32, making it impossible to correctly determine whether or not an overvoltage is present. If a short circuit or open circuit occurs in the voltage measurement voltage divider resistors 34 and 35, the input voltage Vin will not be divided by the two voltage measurement voltage divider resistors 34 and 35, making it impossible to correctly measure the input voltage Vin.

[0034] If an abnormality occurs in the voltage divider circuit 30, a difference will occur between the input voltage Vin measured based on the voltage V1 input from the first connection point 33 and the input voltage Vin measured based on the voltage V2 input from the second connection point 36. Therefore, if the difference between the input voltage Vin measured based on the voltage V1 input from the first connection point 33 and the input voltage Vin measured based on the voltage V2 input from the second connection point 36 is greater than or equal to a threshold, it can be determined that an abnormality has occurred in the voltage divider circuit 30.

[0035] [Effects of this embodiment] (1) By providing a wiring 80 that inputs the voltage at the first connection point 33 to the processor 70, the processor 70 can measure the input voltage Vin from the voltage V1 input from the first connection point 33 and the voltage V2 input from the second connection point 36. If there is no abnormality in the voltage divider circuit 30, the difference between the first input voltage and the second input voltage will be less than the threshold. If there is an abnormality in the voltage divider circuit 30, one of the first input voltage and the second input voltage will not be able to be measured correctly, and the difference between the first input voltage and the second input voltage will be greater than or equal to the threshold. Therefore, the processor 70 can determine that there is an abnormality in the voltage divider circuit 30.

[0036] (2) The outputs of the overvoltage detection voltage divider resistors 31 and 32, which were used to detect overvoltage, are branched by the wiring 80. This allows the processor 70 to measure the input voltage Vin using the overvoltage detection voltage divider resistors 31 and 32. In other words, the overvoltage detection voltage divider resistors 31 and 32 can be used as voltage divider resistors for measuring the input voltage Vin. This reduces the size of the voltage monitoring circuit 20 compared to the case where a new voltage divider resistor is provided to measure the input voltage Vin in order to detect an abnormality in the voltage divider circuit 30.

[0037] (3) Wiring 80 is connected between the first filter 40 and the control circuit 50 so that the voltage V1 after noise has been removed by the first filter 40 is input to the processor 70. Therefore, the size of the voltage monitoring circuit 20 can be kept down compared to the case in which a new filter is provided to remove noise from the voltage V1 input to the processor 70 from the first connection point 33.

[0038] (4) The time constant of the first filter 40 is smaller than that of the second filter 60. Therefore, using the first filter 40 allows for faster detection of overvoltage. On the other hand, the noise contained in the voltage V1 input to the processor 70 from the first connection point 33 may be greater than the noise contained in the voltage V2 input to the processor 70 from the second connection point 36. In this case, the processor 70 can reduce the effect of noise by using the difference between the average value of the first input voltage and the average value of the second input voltage as the difference between the first input voltage and the second input voltage.

[0039] (5) If an abnormality occurs in the voltage divider circuit 30, the processor 70 notifies the higher-level control unit 13. This allows the higher-level control unit 13 to take control of the abnormality in the voltage divider circuit 30, such as notifying the user.

[0040] [Example of changes] The embodiment can be implemented with the following modifications. The embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0041] ○The wiring 80 may also connect the point between the first connection point 33 and the first filter 40 to the processor 70. In this case, a dedicated filter should be provided to remove noise from the voltage V1 input from the first connection point 33 to the processor 70.

[0042] ○If an abnormality occurs in the voltage divider circuit 30, the processor 70 does not need to notify the higher-level control unit 13. ○The time constant of the first filter 40 and the time constant of the second filter 60 may be the same.

[0043] ○The voltage monitoring circuit 20 only needs to be able to monitor the input voltage Vin from the power supply 11, and can be installed in any device. [Explanation of symbols]

[0044] 11...Power supply, 13...Higher-level control unit, 20...Voltage monitoring circuit, 30...Voltage divider circuit, 31...Voltage divider resistor for first overvoltage detection, 32...Voltage divider resistor for second overvoltage detection, 33...First connection point, 34...Voltage divider resistor for first voltage measurement, 35...Voltage divider resistor for second voltage measurement, 36...Second connection point, 40...First filter, 50...Control circuit which is an example of an overvoltage determination unit, 60...Second filter, 70...Processor.

Claims

1. A voltage divider circuit connected to the power supply, An overvoltage determination unit that determines whether the input voltage received from the power supply is an overvoltage, A first filter is provided between the voltage divider circuit and the overvoltage detection unit, A voltage measuring unit that measures the input voltage received from the power supply, The system includes a second filter provided between the voltage divider circuit and the voltage measuring unit, The aforementioned voltage divider circuit is A first overvoltage detection voltage divider resistor connected to the power supply, A second overvoltage detection voltage divider resistor connected in series with the first overvoltage detection voltage divider resistor, A first voltage measuring voltage divider resistor connected to the aforementioned power supply, The device comprises a second voltage measuring voltage dividing resistor connected in series with the first voltage measuring voltage dividing resistor, The overvoltage determination unit determines whether the input voltage input from the power supply is an overvoltage by comparing the voltage input from the first connection point, which is the connection point between the first overvoltage detection voltage divider resistor and the second overvoltage detection voltage divider resistor via the first filter, with a reference value. The voltage measuring unit is Based on the voltage input from the first connection point via the first filter, the input voltage input from the power supply is measured. The input voltage from the power supply is measured based on the voltage input from the second connection point, which is the connection point between the first voltage measuring voltage divider resistor and the second voltage measuring voltage divider resistor, via the second filter. A voltage monitoring circuit that determines that an abnormality has occurred in the voltage divider circuit if the difference between the input voltage measured based on the voltage input from the first connection point and the input voltage measured based on the voltage input from the second connection point is greater than or equal to a threshold.

2. The voltage monitoring circuit according to claim 1, wherein wiring extending from between the first filter and the overvoltage determination unit is connected to the voltage measurement unit so that a voltage from which noise has been removed by the first filter is input.

3. The voltage monitoring circuit according to claim 1, wherein the voltage measuring unit notifies a higher-level control device when it determines that an abnormality has occurred in the voltage divider circuit.

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