JP3011560B2 - Multiplication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a multiplication device for obtaining a product of a current and a voltage by using a Hall element.

[0002]

2. Description of the Related Art Generally, this type of multiplication device is widely used as a power multiplication circuit of a wattmeter or a watt-hour meter because of its simple structure and miniaturization. Hereinafter, such a multiplication device will be described with reference to FIG. Input terminals P ₁ , P ₂
The power supply voltage V _L to be measured input to the
Voltage-current converting means 10
5 is input. Voltage - current conversion unit 105 outputs a current proportional to the input voltage V _L to the control current terminal T ₁ of the Hall element 106. On the other hand, the current I _L to be measured is input to the current coil 103 wound around the magnetic core 104, the magnetic field proportional to the input current I _L is generated in the gap of the magnetic core 104, the magnetic field in the gap and the hole Element 106
(1) between the voltage output terminals T ₃ and T _{4 of the} Hall element 106 placed so as to be orthogonal to the flow direction of the control current
Hall electromotive force E _y given by equation occurs. _{E y = R h B z J} x (1)

Here, R _h is the Hall coefficient, B _z magnetic field strength, and J _x is the current density. The differential amplifier 107 removes the in-phase component of the Hall electromotive force between the voltage output terminals T ₃ and T ₄ and outputs a voltage proportional to the power of the product of the current and the voltage to be measured.

[0004]

The above-described conventional multiplier has the following problem regarding the linearity of the output voltage characteristic of the Hall element.

In general, the conventional multiplier assumes that the Hall coefficient R _{h in} equation (1) is constant.
Relationship between the output voltage and the magnetic flux density (or magnetic field strength in the gap) of the Hall element as shown in FIG. 2, Hall coefficient from the region of I shown magnetic flux density is small is non-linear R _h
Is not constant. Therefore, when the current value to be measured is small, the magnetic field in the gap of the magnetic core 104 becomes small, and the accuracy of the multiplication output at the time of low current is limited in the conventional multiplication device.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a multiplication device capable of outputting an accurate product of current and voltage even when measuring a low current. I do.

[0007]

SUMMARY OF THE INVENTION In a multiplier for calculating a product of a current and a voltage by using a Hall element, a voltage-current conversion means for converting a voltage to be measured into a current, and a first means for flowing the current to be measured. A magnetic core having a current coil in addition to a second current coil through which a current output from the voltage-current conversion means flows, a sample and hold means for holding a sampling value of an output voltage of the Hall element, and a Hall element And a subtraction means for subtracting the voltage held by the sample-and-hold means from the output voltage.

[0008]

According to the present invention, by taking such measures,
The magnetic core generates a magnetic field strength that is the sum of a magnetic field strength proportional to the current to be measured flowing through the first current coil and a magnetic field strength proportional to the voltage to be measured flowing through the second current coil. The magnetic flux density in the element is increased, and an accurate multiplied output multiplied in the linear region is obtained. Then, the current to be measured and the voltage to be measured are obtained by subtracting the multiplied output when the current input to the first current coil held in the sample and hold means is zero by the subtracting means from the previous multiplied output. Can be output.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the multiplication device according to the present invention. In the figure, P ₁ and P ₂ are power supply voltage input terminals for inputting a power supply voltage _VL to be measured, 1 and 2
Is a resistor for dividing the power supply voltage _VL input to P ₁ and P _2, and can be configured using a voltage dividing resistor or a transformer. 3 magnetic core for applying a magnetic field to the Hall element 8, the first current coil for generating a magnetic field proportional to the current I _L to be measured into the gap of the magnetic core 3 is 4, 5 resistors 1 , 2 outputs a current proportional to the power supply voltage divided by
The current conversion means 6 is a second current coil for flowing the current output from the first voltage-current conversion means 5 and generating a magnetic field proportional to the voltage to be measured in the gap of the magnetic core 3. . 7 The second voltage for supplying the control current proportional to be measured voltage to the control current input terminal T ₁ of the Hall element 8 - current converting means, 8 is a current input terminal T _1,
A Hall element having a voltage output terminal T _3, T ₄ for outputting a voltage obtained by T ₂ and Hall effect, the control current input terminals T _1, T ₂ and the voltage output terminal T _3, T ₄ and make plane Are held between the gaps of the magnetic core 3 so as to be orthogonal to the magnetic field generated in the gap.
Reference numeral 9 denotes a differential amplifier that outputs a difference between voltages output between the voltage output terminals T ₃ and T ₄ of the Hall element 8. Reference numeral 10 denotes a sample and hold means, which is a sampling switch 1
While the switch 2 is closed, the output of the differential amplifier 9 is input and held. Numeral 11 denotes a subtraction means, which subtracts the output of the sample and hold means 10 from the output of the differential amplifier 9 and outputs the result.

Next, the operation of the apparatus configured as described above will be described. The power supply voltage V _L to be measured, which is input to the power supply voltage input terminals P ₁ and P ₂ , is converted into an appropriate voltage by the resistors 1 and 2, and the first voltage-current conversion means 5 and the second voltage-current It is input to the conversion means 7. The current converted to a current proportional to the input voltage by the second voltage-current conversion means 7 is applied to the control current input terminal T of the Hall element 8.
_{From 1} flows into the Hall element 8. The current I _L to be measured flows through the first current coil 4 of the magnetic core 3, while the voltage V _M to be measured output from the first voltage-current conversion means 5 flows through the second current coil 6. since current proportional to _L flows, and the magnetic field strength B _z which is proportional to the current I _L to be measured in the gap of the magnetic core 3 (I _L), the magnetic field strength B _z in proportion to the voltage V _L to be measured (V _L ) and the magnetic field intensity B _z (I _L ) + B _z (V _L ) are generated. Accordingly, a Hall electromotive force E _y1 given by the equation (2) is generated at the voltage output terminals T ₃ and T ₄ of the Hall element 8.

[0011]

E _y1 = R _h (B _z (I _L ) + B _z (V _L )) J _x (V _L ) (2)

Here, J _x (V _L ) is the output current density of the second voltage-current conversion means 7. Magnetic field strength B
_{By z} (V _L) is added, because in this way the magnetic field strength is increased, it can be regarded as the Hall coefficient R _h constant. Further, without supplying the current I _L to be measured to the first current coil 4, when a current flows in proportion to the voltage to be measured only in the second current coil 6, Hall electromotive force given by expression (3) E _y2 occurs.

[0013]

E _y2 = R _h B _z (V _L ) J _x (V _L ) (3)

Then, the sampling switch 12 is closed to hold the Hall electromotive force E _y2 of the equation (3) in the sample and hold means 10, and the Hall electromotive force E _y1 is subtracted by the subtraction means 11.
When the Hall electromotive force E _y2 is subtracted from

[0015]

Equation 3] as given by _{E y1 -E y2 = R h B} z (I L) J x (V L) (4), the product of the voltage to be measured to be measured current.

Therefore, according to the configuration of the embodiment described above, the region II can be used while avoiding the region I shown in FIG. 2, so that the nonlinear characteristic of the Hall element 8 at a low magnetic field strength can be used. An accurate multiplication result excluding the error caused by the above can be obtained.

[0017]

As described above, according to the present invention, since the Hall electromotive force characteristic when the magnetic field strength is small is used while avoiding a non-linear portion, accurate measurement can be performed without being affected by the magnitude of the current to be measured. The product of the current and the voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is an output voltage characteristic diagram of a Hall element.

FIG. 3 is a block diagram of a conventional multiplication device.

[Explanation of symbols]

 1, resistor 3 magnetic core 4 first current coil 5 first voltage-current conversion means 6 second current coil 7 second voltage-current conversion means 8 Hall element 9 differential amplifier 10 sample hold Means 11 Subtraction means

Claims (1)

(57) [Claims] 1. A multiplication device for calculating a product of a current and a voltage by using a Hall element, wherein a voltage-current conversion means for converting a voltage to be measured into a current, and a first current coil for flowing the current to be measured. In addition, a magnetic core having a second current coil through which a current output from the voltage-current conversion means flows, a sample-and-hold means for holding a sampling value of an output voltage of the Hall element, and an output voltage of the Hall element A subtracting means for reducing a voltage held by the sample and hold means.