JPH05297026A - Ammeter - Google Patents

Abstract

PURPOSE:To provide an ammeter which can be mounted on a device with only a single power supply by giving a flux in both forward and backward directions to a core with the single power supply and canceling the flux which is generated at the core by charge/discharge current of a bus. CONSTITUTION:A core 3 where a charge line 3 is inserted is provided with a Hall element 2 in a gap. Then, a balanced circuit 6 switches conduction of first and second coils 4 and 5 according to the output of the Hall element and then gives a balanced current according to the output of the hole element 2, thus giving a flux in both forward and backward directions to the core 3 with a battery of a single power supply and then cancels out flux which is generated at the core 3 by charge/discharge current of the charge line 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a current value flowing in a bus bar.

[0002]

2. Description of the Related Art As a conventional technique, a current measuring device shown in FIG. 7 is known. In this current measuring device, a Hall element 103 of a magnetic sensor is arranged in a gap of a C-shaped core 102 through which a bus bar 101 is inserted, and a current obtained by amplifying the output voltage of the Hall element 103 is passed through a coil 104 wound around the core 102. The magnetic flux in the opposite direction to the magnetic flux generated in the core 102 by the measurement current
This is a device that constantly supplies the core 102 and the Hall element 103 to a magnetic equilibrium state with zero magnetic field, and measures the measured current value with high accuracy by the equilibrium current flowing in the coil 104.

[0003]

The conventional current measuring device requires both positive and negative power supplies in order to apply magnetic flux to the core 102 in both forward and reverse directions. For this reason, in a vehicle having only a single power source, such as an automobile, it is necessary to mount both positive and negative power sources for current measurement, which increases the cost of the current measuring device.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic flux in both forward and reverse directions to a core with a single power source, which can be inexpensively mounted on a single power source. It is to provide a current measuring device.

[0005]

The current measuring device of the present invention employs the following technical means. The current measuring device includes a magnetic sensor that converts a magnetic signal into an electric signal, a magnetic flux that is generated by a current flowing through a bus to be measured, and a core that forms a closed magnetic path through the magnetic sensor, and is wound around the core. And a balancing circuit that gives a balancing current to the coil that cancels the magnetic flux generated in the core according to the output of the magnetic sensor, and measures the current value flowing in the bus by the balancing current output from the balancing circuit. To do.
The balance circuit detects the direction of the current flowing through the bus by the output of the magnetic sensor, and switches the balanced current according to the output of the magnetic sensor created from a single power supply according to the direction of the current flowing through the bus. To apply to the coil to cancel the magnetic flux generated in the core.

[0006]

When the current flow of the bus bar flows to one side,
A balanced current generated by a single power supply and corresponding to the output of the magnetic sensor is applied to the coil so as to cancel the magnetic flux generated in the core by the current flowing through the bus bar. On the contrary, when the current flow of the busbar flows to the other side, a balanced current corresponding to the output of the magnetic sensor created by the single power supply is given to the coil so as to cancel the magnetic flux generated in the core by the current flowing in the busbar.

[0007]

The current measuring device of the present invention can apply magnetic flux in both forward and reverse directions to the core with a single power source. Therefore, the current measuring device can be mounted at low cost because the current measuring device can be mounted even if it has only a single power source.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a current measuring device of the present invention will be described based on an embodiment shown in the drawings. [Structure of Embodiment] FIGS. 1 to 4 show a first embodiment of the present invention. FIG. 1 is an electric circuit diagram of a current measuring device.
FIG. 3 is a configuration diagram of an automobile power supply system using this current measuring device. The current measuring device 1 is roughly classified into a C-shaped core 3 having a Hall element 2 interposed between the gap and a core 3.
It is composed of first and second coils 4 and 5 wound around, and a balancing circuit 6 which applies a balancing current to the first and second coils 4 and 5 according to the output of the hall element 2.

The Hall element 2 is a magnetic sensor for converting a magnetic signal into an electric signal and generates an output voltage according to the magnetic flux generated in the core 3. The hall element 2 is a key switch 7
Is set to the ignition terminal 7a to receive a constant current through the constant current circuit 8. The core 3 is a C-shaped iron core in which thin plate-shaped permalloy is insulated and laminated, and the Hall element 2 is provided in the gap to form a closed magnetic circuit. Inside the core 3, a charging line (bus bar) 9 of the vehicle-mounted battery 10 whose current is to be measured is inserted, and a magnetic flux corresponding to the amount of current flowing in the charging line 9 and the flowing direction of the current flows in the closed magnetic circuit of the core 3. Occur. The first coil 4 and the second coil 5 are formed by winding an enameled wire around the core 3 at different positions, directly or through a bobbin.
The coil 5 has the same diameter and the same number of turns, but is wound so as to generate mutually opposite magnetic fluxes when a current is applied. The balance circuit 6 detects the direction of the current flowing through the charging line 9 based on the output voltage of the hall element 2 and outputs the balanced current created by the power supplied from the vehicle-mounted battery (single power source) 10 to the first coil 4 or the first coil 4. This is a circuit for switching to the two coils 5 and applying it to cancel the magnetic flux generated in the core 3.

The balanced circuit 6 of this embodiment is composed of the pre-amplifier section 1
1, a charge cancellation amplifier unit 12, a discharge cancellation amplifier unit 13, and a code signal generation circuit 14. Pre-stage amplifier section 11
Is a circuit that amplifies the positive voltage and the negative voltage generated by the hall element 2. The charge cancellation amplifier unit 12 is
Only when the charging current flows through the charging line 9 and the magnetic flux is generated in the core 3 in the direction of arrow A in FIG. Is a circuit for giving a magnetic flux in the direction of arrow B to the core 3 so that the magnetic flux detected by the Hall element 2 becomes zero. The discharge canceling amplifier unit 13 holds a hole in the second coil 5 only when the discharge current flows through the charging line 9 and magnetic flux is generated in the core 3 in the direction of arrow B in FIG. It is a circuit that gives a balanced current according to the output voltage of the element 2 to give a magnetic flux in the direction of the arrow A to the core 3 so that the magnetic flux detected by the hall element 2 becomes zero. The sign signal generation circuit 14 outputs a sign signal (Hi or Low) indicating the current direction of the charging line 9 to the S output terminal 15 according to the operating states of the charge cancellation amplifier unit 12 and the discharge cancellation amplifier unit 13. The relationship between the sign signal output from the S output terminal 15 and the charging / discharging current is shown in FIG.

Further, the balance circuit 6 is provided with a V output terminal 16 for outputting an output voltage according to the balance current value given to the first coil 4 and the second coil 5. The relationship between the output voltage output from the V output terminal 16 and the charge / discharge current is shown in FIG.
Shown in. The current of the charging line 9 is I1, the number of turns of the charging line 9 is N1, and the balanced current of the first coil 4 (second coil 5) is I1.
2 and the number of turns of the first coil 4 (second coil 5) is N2, the following formula 2 is established.

## EQU00001 ## I1 [A] .times.N1 [number of turns] = I2 [A] .times.N2 [number of turns] Here, if N1 is 1 turn and N2 is 2000 turns, the above equation 1 is Becomes

(2) I2 = I1 / 2000 Therefore, the resistance 16 between the V output terminal 16 and the ground is
When the resistance value of a is R, the output voltage of the V output terminal 16 is obtained by the following mathematical formula 3.

## EQU00003 ## V output voltage (V) = R.times.I1 / 2000 Then, if the resistance value of the resistance between the V output terminal 16 and the ground is 20 .OMEGA. And the maximum current value of the charging line 9 is 300 A, the V output voltage Is 0 to 3V.

The power supply system for an automobile using the above-mentioned current measuring device 1 has a code signal output from the S output terminal 15,
And the charge / discharge state of the battery 10 is calculated from the output voltage corresponding to the balanced current value output from the V output terminal 16,
An electronic control circuit 17 for monitoring the state of charge of the battery 10 is provided. That is, the electronic control circuit 17 controls the S output terminal 15
When the sign signal of is high, the output voltage of the V output terminal 16 is integrated as the charging current value. Conversely, when the sign signal of the S output terminal 15 is low, the output voltage of the V output terminal 16 is changed to the charging current value. And the charge state of the battery 10 is detected from the sum of the integrated values. The battery 10 in the vehicle power supply system is charged by the electric power generated by the alternator 18 driven by the engine. And
The battery 10 discharges the charged electric power to each electric load 19 when the electric power of each electric load 19 (headlight, audio, air conditioner, etc.) cannot be supplied only by the electric power generated by the alternator 18. Reference numeral 20 in FIG. 2 denotes a starter, which is energized to start the engine when the key switch 7 is set to the starter terminal 7b. Also, reference numeral 21
Is an idle speed controller for controlling the idle speed of the engine, and is controlled by the electronic control circuit 17.

[Operation of Embodiment] Next, the operation of the above embodiment will be briefly described. When the power generated by the alternator 18 is higher than the power used by the electric load 19, the battery 10
Is charged. A magnetic flux in the direction of arrow A is generated in the core 3 by the charging current flowing through the charging line 9. Then, the front-stage amplifier unit 11 amplifies the positive voltage generated by the Hall element 2. Then, the discharge canceling amplifier unit does not operate, and the charge canceling amplifier unit gives a balanced current to the first coil 4 to give a magnetic flux in the direction of arrow B to the core 3 to cancel the magnetic flux of the core 3 and detect it by the hall element 2. Make the magnetic flux to be zero. At this time, the S output terminal 15 outputs a Hi signal to the electronic control circuit 17, and the V output terminal 16 outputs a voltage according to the balanced current to the electronic control circuit 17. Then, the electronic control circuit 17
Receives a Hi signal from the S output terminal 15, the output voltage of the V output terminal 16 is integrated as a charging current value.

When the power generated by the alternator 18 is lower than the power used by the electric load 19, the battery 10 is discharged. A magnetic flux in the direction of arrow B is generated in the core 3 by the discharge current flowing through the charging line 9. Then, the front-stage amplifier section 11
Amplifies the negative voltage generated by the Hall element 2. Then, the charge canceling amplifier unit does not operate, and the discharge canceling amplifier unit gives a balanced current to the second coil 5 to give a magnetic flux in the direction of arrow A to the core 3 to cancel the magnetic flux of the core 3 and detect it by the hall element 2. Make the magnetic flux to be zero. At this time, the S output terminal 15 outputs a low signal to the electronic control circuit 17, and the V output terminal 16 outputs a voltage according to the equilibrium current to the electronic control circuit 17. Then, the electronic control circuit 17
Since the low signal is received from the S output terminal 15, the output voltage of the V output terminal 16 is integrated as the discharge current value.

[Effects of the Embodiment] In the present embodiment, as shown by the above-described operation, the magnetic flux in both the forward and reverse directions is applied to the core 3 by the battery 10 which is a single power source, and is generated in the core 3 by the charging / discharging current. The magnetic flux can be canceled. Therefore, the current measuring device 1 can be mounted in a vehicle having only the battery 10 which is a single power source, so that the current measuring device 1 can be mounted in the vehicle at low cost and the state of charge of the battery 10 can be accurately detected. You can

[Second Embodiment] FIG. 5 is an electric circuit diagram of a current measuring device 1 showing a second embodiment. In this embodiment, the core 3
The number of coils 22 wound around the coil 22 is set to one, and the output direction reversing circuit 23 in which the semiconductor switch element is assembled to the H-blitch is used to reverse the flow direction of the equilibrium current applied to the coil 22. The magnetic flux in both directions generated in the core 3 is canceled.

[Third Embodiment] FIG. 6 is an electric circuit diagram of a current measuring device 1 showing a third embodiment. In the present embodiment, the output voltage according to the balanced current given to the first coil 4 and the second voltage
An output voltage according to a balanced current given to the coil 5 is separately output to the electronic control circuit (see the first embodiment), and a first output terminal 24 connected to the first coil 4 and a second coil And a second output terminal 25 connected to 5.
The resistors 24a and 25a are provided separately between the first output terminal 24 and the ground and between the second output terminal 25 and the ground in order to convert the balanced current into a voltage. Although the code signal generating circuit (see the first embodiment) and the S output terminal (see the first embodiment) are abolished by this technique, the electronic control circuit (see the first embodiment) has the first output terminal 24. And 2 connected to the second output terminal 25
It is provided to receive one analog signal.

[Modification] In the above embodiment, the Hall element is shown as an example of the magnetic sensor.
Alternatively, another magnetic sensor such as a magnetoresistive element or a resonance type magnetic sensor may be used. Although the example of detecting the charging / discharging of the battery of the automobile has been shown, the present invention can be applied to all current measuring devices 1 that detect the flow direction and the amount of current. The numerical values shown in the examples are used for explaining the examples, and can be variously changed according to the purpose of use and the like.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a current measuring device (first embodiment).

FIG. 2 is a configuration diagram of an automobile power supply system using a current measuring device (first embodiment).

FIG. 3 is a graph showing the relationship between the sign signal of the S output terminal and the charging / discharging current (first embodiment).

FIG. 4 is a graph showing the relationship between the output voltage of the V output terminal and the charging / discharging current (first embodiment).

FIG. 5 is an electric circuit diagram of a current measuring device (second embodiment).

FIG. 6 is an electric circuit diagram of a current measuring device (third embodiment).

FIG. 7 is an electric circuit diagram of a current measuring device (prior art).

[Explanation of symbols]

 1 Current Measuring Device 2 Hall Element (Magnetic Sensor) 3 Core 4 First Coil 5 Second Coil 6 Balance Circuit 9 Charging Line (Bus) 10 Battery (Single Power Supply)

Claims (1)

[Claims] 1. A magnetic sensor for converting a magnetic signal into an electric signal, a magnetic flux generated by a current flowing through a bus to be measured, and a core forming a closed magnetic path via the magnetic sensor, and a core wound around the core. And a balancing circuit that gives a balancing current to the coil that cancels out the magnetic flux generated in the core according to the output of the magnetic sensor, and measures the current value flowing in the busbar by the balancing current output from the balancing circuit. In the current measuring device, the balance circuit detects the direction of the current flowing through the bus by the output of the magnetic sensor, and the balanced current according to the output of the magnetic sensor created from a single power supply, the current direction flowing through the bus. The current measuring device is characterized in that the magnetic flux generated in the core is canceled by switching to the coil according to the above.