JPH06194394A - Multiplier - Google Patents

Abstract

PURPOSE:To provide a multiplier which can produce a correct product of current and voltage even in case of low current measurement. CONSTITUTION:The multiplier comprises a voltage-current converting means 5, a magnetic core 4 having a second current coil 6 for passing output current from the voltage-current converting means 5 in addition to a first current coil 3, means 10 for sampling and holding output voltage from a Hall element 8, and means 11 for subtracting the voltage held in the sample & hold means 10 from the output voltage of the Hall element 8. This constitution allows correct determination of the product of current and voltage regardless of the magnitude of current to be measured.

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 current and 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 for a power meter 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 and P ₂
The power supply voltage V _L to be measured inputted to the voltage dividing resistor 10
The voltage-current converting means 10 is divided by 1, 102.
Input to 5. The voltage-current conversion means 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, and a magnetic field proportional to the input current I _L is generated in the gap of the magnetic core 104. 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 of
The Hall electromotive force E _y given by the formula is generated. E _y = R _h B _z J _x (1)

However, R _h is Hall coefficient, B _z magnetic field strength, and J _x is 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 that is the product of the current and the voltage to be measured.

[0004]

The conventional multiplication device described above has the following problems regarding the linearity of the output voltage characteristic of the Hall element.

Generally, in the conventional multiplication device, it is premised that the Hall coefficient R _{h in the} equation (1) is constant.
As shown in FIG. 2, the relationship between the output voltage of the Hall element and the magnetic flux density (or the magnetic field strength of the gap) is non-linear in the region I where the magnetic flux density is small, so the Hall coefficient 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, so that the conventional multiplication device has a limit in the accuracy of the multiplication output at a low current.

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

[0007]

In a multiplication device for calculating a product of current and voltage using a Hall element, a voltage-current conversion means for converting a voltage to be measured into a current, and a current to be measured to flow. Magnetic core having a second current coil for passing the current output from the voltage-current conversion means, sample hold means for holding the sampling value of the output voltage of the hall element, and the hall element And a subtracting means for subtracting the voltage held by the sample and hold means from the output voltage of 1.

[0008]

The present invention, by taking such means,
The magnetic core generates a magnetic field strength that is the sum of the magnetic field strength proportional to the current to be measured flowing through the first current coil and the magnetic field strength proportional to the voltage to be measured flowing through the second current coil. The magnetic flux density in the device is increased to obtain an accurate multiplication output multiplied in the linear region. Then, by subtracting the multiplication output when the current input to the first current coil held in the sample hold means is made zero by the subtraction means, the current to be measured and the voltage to be measured. It is possible to output the multiplication result which is the product of

[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 of the present invention. In the figure, P ₁ and P ₂ are power supply voltage input terminals 1 and 2 for inputting the power supply voltage V _L to be measured.
Is a resistor for dividing the power supply voltage V _L input to P ₁ and P _2, and can be configured using a voltage dividing resistor or a transformer or the like. 3 is a magnetic core for giving a magnetic field to the Hall element 8, 4 is a first current coil for producing a magnetic field proportional to the current I _L to be measured in the gap of the magnetic core 3, and 5 is a resistor 1. , A first voltage that outputs a current proportional to the power supply voltage divided by 2 −
The current converting means 6 is a second current coil for causing a current output from the first voltage-current converting means 5 to flow and for generating a magnetic field proportional to the voltage to be measured in the gap of the magnetic core 3. . Reference numeral 7 is a second voltage-current conversion means for supplying a control current proportional to the voltage to be measured to the control current input terminal T ₁ of the Hall element 8, and 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 Is held in the gap of the magnetic core 3 so as to be orthogonal to the magnetic field generated in the gap.
Reference numeral 9 is a differential amplifier that outputs the difference between the voltages output between the voltage output terminals T ₃ and T ₄ of the Hall element 8. Reference numeral 10 is a sample hold means, which is a sampling switch 1
While 2 is closed, the output of the differential amplifier 9 is input and held. Reference numeral 11 is a subtraction means, which subtracts the output of the sample hold means 10 from the output of the differential amplification section 9 and outputs it.

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 are converted. It is input to the conversion means 7. The current converted into a current proportional to the input voltage in the second voltage-current converting means 7 is the control current input terminal T of the hall element 8.
_It flows from ₁ to the inside of the Hall element 8. A current I _L to be measured flows through the first current coil 4 of the magnetic core 3, while a voltage V 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 magnetic field strength B _z (I _L) of the sum of the _{(V L) + B z (} V L) is generated. Therefore, the 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)

However, J _x (V _L ) is the output current density of the second voltage-current converting 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. If a current proportional to the voltage to be measured is applied only to the second current coil 6 without applying the current I _L to be measured to the first current coil 4, the Hall electromotive force given by the formula (3) is given. E _y2 occurs.

[0013]

[ _Equation 2] E _y2 = R _h B _z (V _L ) J _x (V _L ) (3)

Therefore, the sampling switch 12 is closed to hold the Hall electromotive force E _y2 of the formula (3) in the sample hold means 10, and the subtracting means 11 holds the Hall electromotive force E _y1.
When the Hall electromotive force E _y2 is subtracted from, the output of the subtraction means 11 is

[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 above embodiment, the region II can be used while avoiding the region I shown in FIG. 2, so that the non-linear characteristic of the Hall element 8 at a low magnetic field strength is used. It is possible to obtain an accurate multiplication result excluding the error caused by.

[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 the non-linear portion, it is accurate without being affected by the magnitude of the current to be measured. It is possible to obtain the product of various currents and voltages.

[Brief description of drawings]

FIG. 1 is a block diagram of 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, 2 resistor 3 magnetic core 4 1st current coil 5 1st voltage-current conversion means 6 2nd current coil 7 2nd voltage-current conversion means 8 Hall element 9 differential amplification section 10 sample hold Means 11 Subtraction means

Claims (1)

[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 a current to be measured. In addition, a magnetic core having a second current coil for flowing the current output from the voltage-current conversion means, sample hold means for holding a sampling value of the output voltage of the Hall element, and the output voltage of the Hall element And a subtraction unit for reducing the voltage held by the sample and hold unit.