JP2002267698A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect the load current of a battery even in a very small current rage without providing a special change-over switch. SOLUTION: In the current detector, the battery 1 is connected to a load circuit 17 by way of a contact of a main relay, and in parallel to the main relay contact 2, and also a pre-charge circuit 3 connecting in series a pre-charge relay contact 4 and a pre-charge resistor 5 is connected so that the load current flowing in the battery 1 is detected with the first current detection circuit 7. The current detector comprises a control circuit 9 controlling on/off of the pre-charge relay contact 4 and the main relay contact 2 and a second current detector circuit 8 detecting the load current from the voltage of the pre-charge resistor 5. The current detector detects the load current with the first current detector circuit 7 in the state of turning the main relay contact 2 'on', and detects the load current with the second current detector circuit 8 in the state of turning the main relay contact 2 'off' and the pre-charge relay contact 4 'off'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a load current flowing in a battery of a motor-driven electric device such as an electric vehicle.

[0002]

2. Description of the Related Art It is important to accurately calculate the remaining capacity of a battery for running an automobile. If an error occurs in the detection of the remaining capacity, the error is accumulated as the traveling time becomes longer. The accumulated error makes the actual remaining capacity of the battery and the calculated remaining capacity different from the remaining capacity, making it difficult to use the battery in an optimum remaining capacity range, causing overcharging and overdischarging. A battery can be used for a long life by charging and discharging within a preferable remaining capacity range. However, overcharging and overdischarging significantly reduce electrical performance and shorten the life. Because automotive batteries are extremely expensive,
It is important to be able to use it for as long as possible.

[0003] The remaining capacity of a battery is calculated by integrating the current flowing through the battery. The remaining capacity is calculated by subtracting the integrated value of the discharging current from the integrated value of the charging current while considering the charging efficiency and the discharging efficiency. In order to accurately calculate the remaining capacity, it is necessary to accurately detect the battery current. By the way, the load current flowing through the battery is detected by a current sensor. Current sensors are designed to accurately detect large currents. This is because, when the detection error of the large current is large, the calculation error of the remaining capacity becomes large.

[0004]

A current sensor which can accurately detect a large current has difficulty in accurately detecting a small current. Ideally, it is possible to accurately detect a small current to a full scale, but it is extremely difficult to detect a load current with high accuracy in all measurement ranges. The measurement error of the minute current also has an adverse effect on the calculation of the remaining capacity. This is because the error is accumulated with time because the time used with a small load current is extremely long.

In order to solve this drawback, an apparatus has been developed which detects a current by switching between a small current and a large current (JP-A-10-307563). As shown in FIG. 1, this device includes a large current sensor 20 and a small current sensor 2.
1 are connected in parallel and switched by the load current. In this device, it is necessary to provide a dedicated switch 22 for switching between the large current sensor and the minute sensor. The changeover switch 22 requires a very large current of several hundred amperes and requires extremely high reliability, so that it is very expensive. In particular, since switching is frequently performed depending on the magnitude of the current, it is necessary to design a very long life while switching a large current. Further, when this switch fails, there is a disadvantage that the electric vehicle cannot run. Further, since the switching is performed according to the magnitude of the current, there is a disadvantage that the load current is momentarily interrupted when the switching is performed, and the smooth rotation of the motor is hindered. This makes smooth running with the motor difficult, and causes a deterioration in running feeling.

[0006] The present invention has been developed with a view to solving such a drawback. An important object of the present invention is to provide a current detection device capable of accurately detecting a load current of a battery even in a minute current range without providing a dedicated changeover switch.

[0007]

According to the current detecting device of the present invention, a battery 1 is connected to a load circuit 17 including a driving motor via a contact of a main relay, and a pre-charger is connected in parallel with the main relay contact 2. The first current detection circuit 7 detects a load current flowing through the battery 1 of the motor drive electric device connected to the precharge circuit 3 in which the charge relay contact 4 and the precharge resistor 5 are connected in series. A control circuit 9 for turning on and off the precharge relay contact 4 and the main relay contact 4;
A second current detecting circuit for detecting a load current by detecting a voltage between both ends of the precharge resistor; In the current detection device, when the main relay contact 2 is turned on, the first current detection circuit 7 detects a load current, and when the main relay contact 2 is turned off and the precharge relay contact 4 is turned on, The second current detection circuit 8 detects a load current.

The first current detection circuit 7 can detect a current by providing a current sensor 10 for detecting a load current via a magnetic flux. Further, the current detection device corrects the detection value of the first current detection circuit 7 with the detection value detected by the second current detection circuit 8 in a state where the main relay contact 2 is turned off and the precharge relay contact 4 is turned on. be able to.

Further, the current detecting device according to claim 4 of the present invention includes a closed loop current detecting circuit 12 for correcting a current value detected by the first current detecting circuit 7. The closed loop current detection circuit 12 is connected in series with the current detection resistor 13, a detection circuit 14 for detecting a voltage across the current detection resistor 13 to detect a current flowing through the current detection resistor 13, and a current detection resistor 13. And a switching element 15. The current detection resistor 13 and the switching element 15
And a closed loop circuit including the current sensor 10 and the switching element 15, and are connected so that a minute current flows while the switching element 15 is turned on. This current detection device uses the current value detected by the closed loop current detection circuit 12 when the switching element 15 is on,
The detection value of the current detection circuit 7 is corrected.

The first current detecting circuit 7 can detect a current by providing a current sensor 10 for detecting a load current via a magnetic flux. In the battery 1, a plurality of battery modules 1A are connected in series, and the closed loop current detection circuit 12 can be connected to some of the battery modules 1A. The closed loop current detection circuit 12 is a voltage detection circuit 1 that detects the voltage of the battery module 1A connected to the closed loop current detection circuit 12.
6 can be provided.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. However, the following embodiments illustrate a current detection device for embodying the technical idea of the present invention, and the present invention does not specify the current detection device as follows.

Further, in this specification, in order to make it easier to understand the claims, the numbers corresponding to the members shown in the embodiments will be referred to as "claims" and "claims". In the column of “means”.
However, the members described in the claims are not limited to the members of the embodiments.

FIG. 2 is a circuit diagram of a current detecting device for a vehicle. In the vehicle shown in this circuit diagram, a battery 1 for driving a motor by driving a motor is connected to a vehicle via a contact of a main relay. Load circuit 1 including drive motor
7 is connected. A precharge circuit 3 is connected in parallel with the main relay contact 2. The precharge circuit 3
This circuit connects the precharge relay contact 4 and the precharge resistor 5 in series, and is a circuit for charging the large-capacity capacitor 6 connected in parallel to the load circuit 17.

The large-capacity capacitor 6 is a capacitor having an extremely large capacitance of, for example, several thousand μF to several full μF, and is always charged. When a large amount of electric power is supplied to the motor in a short time, for example, when the vehicle is rapidly accelerated, the electric discharge is performed to make up for the momentary output. Therefore, by connecting the large-capacity capacitor 6, the instantaneous maximum output can be increased, and the instantaneous maximum current of the battery 1 in this state can be limited to a small value to protect the battery 1. For this reason, a large-capacity capacitor 6 is connected to the electric vehicle almost without exception.

In an automobile equipped with a large-capacity capacitor 6, an extremely large charging current flows at the moment when the main relay contact 2 is turned on. This is because when a completely discharged capacitor is directly connected to the battery 1, a current almost short-circuit flows at the moment of connection. In order to limit the peak of the charging current, a precharge circuit 3 is connected in parallel with the main relay contact 2. Further, the large-capacity capacitor 6 is designed to be discharged by a discharge resistor when the ignition switch of the vehicle is turned off. This is to prevent an electric shock even if a user or an operator makes an accidental contact. Therefore, every time the ignition switch is turned on, the large-capacity capacitor 6 needs to be charged with a large charging current. The precharge circuit 3 is connected to charge the large-capacity capacitor 6 with a limited current.

Further, the apparatus shown in the figure is a control circuit for detecting a load current flowing through the battery 1 of the electric vehicle by the first current detection circuit 7 and for controlling the precharge relay contact 4 and the main relay contact 2 to be on / off. 9 and a second current detection circuit 8 for detecting a voltage across both ends of the precharge resistor 5 to detect a load current.

The first current detection circuit 7 detects a load current flowing through the battery 1 with the main relay contact 2 turned on. The first current detection circuit 7 converts a load current into a voltage and outputs the voltage. For example, the first current detection circuit 7 incorporates a Hall element for detecting a magnetic flux generated around a lead wire due to the flow of the load current as the current sensor 10. Further, an operational amplifier for amplifying the signal of the current sensor 10 is built in. An amplifier for amplifying the signal of the current sensor 10 can be provided externally.

Further, the first current detection circuit 7 shown in FIG.
Connects the output of the current sensor 10 to the detection circuit 7A. The detection circuit 7A has a built-in amplifier for amplifying the voltage output from the current sensor 10, or a built-in A / D converter for converting an analog signal, which is the output voltage of the current sensor 10, into a digital signal without a built-in amplifier. The load current is converted into a digital voltage signal and output to the microcomputer 11. The first current detection circuit 7 is adjusted so that the load current can be accurately detected in a region where a large current flows.

The second current detecting circuit 8 detects a voltage generated at both ends of the precharge resistor 5 to detect a load current. The second current detection circuit 8 detects a load current in a state where the main relay contact 2 is turned off and the precharge relay contact 4 is turned on. In this state, a voltage proportional to the load current is generated at both ends of the precharge resistor 5. Voltage (E) generated at both ends of the precharge resistor 5
Is the product of the load current (I) and the precharge resistance (R), that is, voltage (E) = load current (I) × precharge resistance (R). Since the precharge resistor 5 has a constant resistance value, the precharge resistor 5
, The load current can be detected. The second current detection circuit 8 converts a voltage proportional to the detected load current into a digital value and inputs the digital value to the microcomputer 11.

The control circuit 9 is controlled by the microcomputer 11 to turn on and off the main relay and the precharge relay. When the ignition switch is turned on, the control circuit 9 turns on the precharge relay contact 4 while keeping the main relay contact 2 in the off state. In this state, the battery 1 charges the large-capacity capacitor 6 via the precharge relay contact 4. afterwards,
The control circuit 9 controls on / off of the main relay and the precharge relay according to the magnitude of the load current. When the load current is large, the main relay contact 2 is turned on, and power is directly supplied from the battery 1 to the load circuit 17. When turning on the main relay contact 2, the control circuit 9 turns the precharge relay contact 4 on or off. At this time,
The precharge relay contact 4 may be either on or off.
This is because both ends of the precharge circuit 3 are short-circuited via the main relay contact 2. However, preferably, the precharge relay contact 4 is turned on while the main relay contact 2 is turned on. This is because when the load current becomes small and the main relay contact 2 is switched off, the precharge relay contact 4 in the on state does not need to be switched. Also, even if both the main relay contact 2 and the precharge relay contact 4 are turned on, the load current does not flow through the precharge relay contact 4 but flows only through the main relay contact 2 and the power loss due to the precharge resistor 5 Does not occur.

When the load current is small (for example, when the load current is 1 A or less), the control circuit 9
Is turned on, the main relay contact 2 is turned off. The control circuit 9 outputs the load current to the first current detection circuit 7
To switch the main relay contact 2. However, it is also possible to switch off the main relay contact 2 by detecting that the load current is near 0 using the signal input from the engine controller 18, that is, the accelerator signal. This is because, when the accelerator is not depressed, it is not necessary to supply power to the load current, so that the load current becomes small. Therefore, the control circuit 9 can switch the main relay and the precharge relay on and off based on the load current detected by the first current detection circuit 7 or the accelerator signal supplied from the engine controller 18.

When the main relay contact 2 is turned off, the load current passes through the precharge circuit 3 without passing through the main relay contact 2 and is supplied to the load circuit 17. Therefore, a voltage proportional to the load current is generated at both ends of the precharge resistor 5. This voltage is detected by the second current detection circuit 8, and the load current is detected. Second current detection circuit 8
Since it is not necessary to detect a large current, a small current can be accurately detected.

Further, the current value detected by the second current detection circuit 8 does not always match the current value detected by the first current detection circuit 7. The microcomputer 11 assumes that the detection value detected by the second current detection circuit 8 is more accurate in a small current region where the second current detection circuit 8 detects a load current. Therefore, in the small current region where the second current detection circuit 8 detects the load current, the microcomputer 11
Calculate the remaining capacity with the detected current. Furthermore, the microcomputer 11
Corrects the detection current value of the first current detection circuit 7 with the detection current value of the second current detection circuit 8. The correction corrects the 0 level of the detection value of the first current detection circuit 7. For example, the second
When the detection current detected by the current detection circuit 8 is 0 A,
Assuming that the detection current of the first current detection circuit 7 is +30 mA, the detection current value of the first current detection circuit 7
Correction is made so as to shift by mA.

When the load current increases and the main relay contact 2 is turned on, the second current detection circuit 8 cannot detect the load current. In this state, the microcomputer 11
Calculates the remaining capacity by calculating the detection current of the first current detection circuit 7.

Further, the current detecting device shown in FIG.
To correct the detection current of the current detection circuit 7, a closed loop current detection circuit 12 is provided. The closed loop current detection circuit 12 is connected in series with the current detection resistor 13, a detection circuit 14 that detects a voltage across the current detection resistor 13 to detect a current flowing through the current detection resistor 13, and a current detection resistor 13. Switching element 15. The current detection resistor 13 and the switching element 15 are connected in series with each other. Further, the closed loop current detection circuit 12 connects a plurality of elements in series to form a closed loop. This closed loop includes the current detection resistor 13, the switching element 15, the battery 1, and the current sensor 10. Further, the closed loop current detection circuit 12 in the figure is connected so that the main relay contact 2 is also included in the closed loop. The closed loop current detection circuit 12 detects the voltage generated at the current detection resistor 13 and can also detect the on / off state of the main relay contact 2. When the main relay contact 2 turns off,
This is because no voltage is generated at both ends of the current detection resistor 13. However, in the current detection device of the present invention, as shown in FIG. 3, it is not always necessary to connect the main relay contact 2 in a closed loop. The main relay contact can also be connected outside the closed loop current detection circuit.

The switching element 15 is an FET,
Semiconductor switching elements such as transistors can also be used. Further, a relay can be used for the switching element 15. The switching element 15 is turned on and off by a control circuit 9 controlled by the microcomputer 11. Control circuit 9
Turns on the switching element 15 only when detecting a small current in a closed loop and when detecting ON / OFF of the main relay contact 2. At other times, the switching element 15 is kept off. The very small current in the closed loop and whether the main relay contact 2 is on can be detected in a very short time. Therefore, the time during which the switching element 15 is turned on is extremely short. Therefore, the discharge capacity of the closed-loop current detection circuit 12 for discharging the specific battery module 1A connected thereto is small and negligible.

When the switching element 15 is turned on,
The magnitude of the minute current flowing through the closed loop is obtained by detecting the voltage across the current detection resistor 13 by the detection circuit 14, and thus can be specified by the resistance value of the current detection resistor 13. The small current in the closed loop increases in proportion to the voltage of the battery module 1A, and decreases in inverse proportion to the resistance value of the current detection resistor 13. Therefore, the current detection resistor 1
By increasing the resistance value of No. 3, the minute current in the closed loop can be reduced. The closed loop current detection circuit 12 corrects an error in the small current region of the first current detection circuit 7. Therefore, the resistance value of the current detection resistor 13 is increased, and the minute current in the closed loop is reduced, for example, 10 mA to 1 A. In other words, the resistance value of the current detection resistor 13 is specified so as to be a minute current in this range. The fact that the resistance value of the current detection resistor 13 can be increased means that a minute current in a closed loop is accurately detected.
This is because the internal resistance of the battery module 1A and the contact resistance of the main relay contact 2 are sufficiently smaller than the resistance value of the current detection resistor 13 and can be ignored.

The battery 1 of the electric vehicle has a plurality of battery modules 1A connected in series. By the way, the minute current in the closed loop changes according to the voltage supplied to the closed loop current detection circuit 12. In the illustrated device, one battery module 1A is connected in a closed loop. The closed loop current detection circuit 12 can reduce the minute current by lowering the battery voltage. Further, an inexpensive switching element having a low withstand voltage can be used as the switching element 15. However, the device of the present invention can be connected to include a plurality of battery modules in a closed loop, or can be connected to include the entire battery in a closed loop.

Further, the current detecting device shown in the figure has a voltage detecting circuit 16 for detecting the voltage of the battery module 1A included in the closed loop. Since this current detection device can accurately detect the supply voltage of the closed loop current detection circuit 12, it can detect a minute current more accurately. This is because the small current (I) of the closed loop is calculated by the following equation. Weak current (I) = voltage of battery module (E) / resistance value of current detection resistor (R) In this equation, it is assumed that the voltage of battery module 1A is accurately measured and the resistance of current detection resistor 13 is accurate. Also, the calculated minute current becomes accurate.

The closed loop current detection circuit 12 turns on the switching element 15 and applies a small current to the closed loop to detect the value. It is assumed that the minute current detected by the closed loop current detection circuit 12 is more accurate than the current value detected by the first current detection circuit 7. Therefore, the detected current value of the first current detection circuit 7 is corrected by the current value detected by the closed loop current detection circuit 12.

For example, if the small current of the closed loop detected by the closed loop current detection circuit 12 is +50 mA and the current value detected by the first current detection circuit 7 is +30 mA, the correction current value becomes +20 mA of the difference. . The microcomputer 11 calculates a correction current value from a difference between a detection current value of the closed loop current detection circuit 12 and a detection current value of the first current detection circuit 7. The microcomputer 11 calculates the remaining capacity of the battery 1 by correcting the detection current of the first current detection circuit 7 with the calculated correction current value.

[0032]

The current detecting device according to the first aspect of the present invention has a feature that the load current of the battery can be accurately detected even in a minute current range without providing a dedicated large current changeover switch. . This is because a minute current is accurately detected by effectively utilizing a main relay already mounted on a motor-driven electric device and a precharge circuit for charging a large-capacity capacitor. The current detection device of the present invention accurately detects a small current by detecting the voltage of a precharge resistor in a state where a main relay contact is turned off and a precharge relay contact is turned on. The small current is calculated from the resistance value of the precharge resistor and the voltage generated across the precharge resistor. Since the resistance value is accurately specified and the voltage can be detected accurately, a small current can be detected very accurately. Therefore, the current detection device of the present invention can accurately detect a small current using the main relay and the precharge circuit, and can accurately calculate the charging and discharging of the small current to reduce the remaining capacity in a state close to the actual battery. Can calculate.
Since the first current detection circuit is designed to accurately detect a large current, the first current detection circuit can also be used to accurately detect the remaining charge / discharge capacity of a large current. Therefore,
Since the current detection device of the present invention can accurately detect the remaining capacity of a battery, it is particularly suitable for detecting the remaining capacity of a battery mounted on a hybrid electric vehicle used in combination with an internal combustion engine. Since the battery used in the hybrid electric vehicle is charged by the power generator during traveling, the remaining capacity of the battery is less likely to be fully charged or completely discharged, and is used in an area where the remaining capacity is always about 40 to 80%. Often. In such a use state, it is difficult to correct the error by resetting the remaining capacity, and therefore it is necessary to particularly accurately detect the error.

Further, the current detecting device according to claim 4 of the present invention also has a feature that the load current of the battery can be accurately detected even in a minute current range without providing a dedicated large current switch. This is because a closed loop current detection circuit is provided to correct the detection current value of the first current detection circuit. The closed loop current detection circuit includes a current detection resistor, a detection circuit that detects a voltage across the current detection resistor to detect a current flowing through the current detection resistor, and a switching element connected in series with the current detection resistor. Have. A closed loop circuit including a current detection resistor, a switching element, and a battery is formed. When the switching element is turned on, a small current flows in the closed loop circuit. The small current in the closed loop is accurately detected as the voltage of the current detection resistor. The minute current of the closed loop detected correctly corrects the detection current of the first current detection circuit. Therefore, even the minute current can be detected accurately by the first current detection circuit designed to detect the large current accurately. This realizes an extremely important feature for a motor-driven electric device such as a hybrid electric vehicle that accurately detects the remaining capacity of the battery, as in the above-described device of the first aspect.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a conventional current detection device.

FIG. 2 is a circuit diagram of a current detection device according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a current detection device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery 1A ... Battery module 2 ... Main relay contact 3 ... Precharge circuit 4 ... Precharge relay contact 5 ... Precharge resistor 6 ... Large capacity capacitor 7 ... 1st current detection circuit 7A ... Detection circuit 8 ... 2nd current detection Circuit 9 Control circuit 10 Current sensor 11 Microcomputer 12 Closed loop current detection circuit 13 Current detection resistor 14 Detection circuit 15 Switching element 16 Voltage detection circuit 17 Load circuit 18 Engine controller 20 Large current sensor 21 ... minute current sensor 22 ... changeover switch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G016 CA03 CB13 CC01 CC02 CC07 CC12 CC16 CC27 CC28 CD06 CD10 CD13 CD14 2G035 AA01 AA04 AA15 AA17 AA21 AB03 AC02 AD03 AD10 AD13 AD26 AD28 AD45 AD47 AD54 AD65 AD66 5H030 AA06 AS08 FF42 5 PG04 PI16 PO06 PU01 PU08 PV09 TO12 TR19 TU01 TU04 TU15

Claims (7)

[Claims] A battery (1) is connected to a load circuit (17) including a drive motor via a contact of a main relay, and a precharge relay contact (4) is connected in parallel with the main relay contact (2). ) And a precharge circuit (3) in which a precharge resistor (5) is connected in series, and a load current flowing through a battery (1) of the motor drive (1) In a current detection device configured to be detected by a current detection circuit (7), a control circuit (9) for turning on and off a precharge relay contact (4) and a main relay contact (2);
(5) a second current detecting circuit (8) for detecting a load current by detecting a voltage between both ends, and when the main relay contact (2) is turned on, the first current detecting circuit (7) A current detecting device for detecting a current, wherein a load current is detected by a second current detecting circuit (8) when the main relay contact (2) is turned off and the precharge relay contact (4) is turned on. 2. The current detection device according to claim 1, wherein the first current detection circuit includes a current sensor for detecting a load current via a magnetic flux. 3. A first current detection circuit (7) using a detection value detected by a second current detection circuit (8) in a state where a main relay contact (2) is turned off and a precharge relay contact (4) is turned on. The current detection device according to claim 1, wherein the detected value is corrected. 4. A motor-driven electric device, wherein a battery (1) is connected to a load circuit (17) including a drive motor via a contact of a main relay, wherein the battery (1) of the motor-driven electric device is connected. A current detection device configured to detect a load current flowing through the first current detection circuit (7), comprising a closed loop current detection circuit (12) for correcting a current value detected by the first current detection circuit (7) The closed loop current detection circuit (12) includes a current detection resistor (13) and the current detection resistor (13).
And a switching element (15) connected in series with the current detection resistor (13) to detect a current flowing through the current detection resistor (13) by detecting a voltage between both ends of the current detection resistor (13). The detection resistor (13) and switching element (15)
(1) constitute a closed loop circuit including a current detection resistor (13) and a switching element (15), and a switching element (15)
When the switching element (15) is on, the first current detection circuit (7) is connected with the current value detected by the closed loop current detection circuit (12) when the switching element (15) is on. A current detection device configured to correct a detection value. 5. The current detection device according to claim 4, wherein the first current detection circuit includes a current sensor for detecting a load current via a magnetic flux. 6. A battery (1) comprising a plurality of battery modules (1).
The current detection device according to claim 4, wherein A) is connected in series, and the closed loop current detection circuit (12) is connected to some of the battery modules (1A). 7. The closed loop current detection circuit (12) according to claim 6, further comprising a voltage detection circuit (16) for detecting a voltage of the battery module (1A) connected to the closed loop current detection circuit (12). Current detector.