JPH0244261A - Current detection method and power supply device - Google Patents

Abstract

PURPOSE:To insulate a detection circuit and a circuit to be detected by providing a magnetoelectric transducer having magnetoresistance and allowing a current to be measured to flow to winding to detect magnetically generated output voltage. CONSTITUTION:A magnetoelectric transducer has magnetoresistance effect having anisotropy and is formed by applying winding 3 to a magnetic core 2. Two current passages are formed from the ferromagnetic membranes arranged so as to cross each other at a right angle on the same plane. Herein, when a current to be measured is allowed to flow to the winding 3, a magnetic field is generated in the magnetic core 2 to form a magnetic circuit. One of the above mentioned two current passages is always arranged so as to be right- angled to the magnetic field of the magnetic circuit and the other current passage is made parallel and the intensity of the magnetic field is changed to detect the voltage change at an output terminal 9. When the output voltage of the transducer 4 is detected by this method, the value corresponding to the current to be measured is obtained and a current can be simply detected. Further, since the magnetic field is interposed, a detection circuit and a circuit to be detected can be insulated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a current detection method for detecting current using a magnetoelectric conversion element.

2. Description of the Related Art Conventionally, this type of current detection method has a configuration as shown in FIG. 7, and a power supply device using the current detection method has a configuration as shown in FIG. In FIG. 7, 1-1' indicates a current to be detected at the current terminal to be measured through a winding 3 provided on a magnetic core 2, a gap is provided in the magnetic core 2, and an input terminal 6-6' is inserted into the gap. Hall element 41L connected to
Insert. Reference numeral 5 is constructed by rectifying and smoothing a battery or alternating current voltage with a DC power supply, and supplies current to the Hall element 41L via the input terminal 6-6'.

The Hall element 4a is arranged so that a magnetic field generated in the gap of the magnetic core 2 is applied thereto, and a temperature compensation circuit 21 is provided on a surface perpendicular to the surface to which the magnetic field is applied and the surface to which the DC power source 6 is connected. The output terminal 9 is connected via the error amplifier 7.

In FIG. 8, numeral 10 is constructed by rectifying and smoothing a battery or alternating current voltage using a DC power supply as described above, and supplies voltage to input terminals 12-12' to the electrical work to be measured. A positive voltage is connected to the input terminal 12, and a negative voltage is connected through the input terminal 12' and through the current detection resistor 19 to the negative output terminal 13'. 11 is a control unit, one end of which is connected to the input terminal 12, the other end of which is connected to the positive output terminal 13, and an output voltage V between the output terminals 13-13'. Either control the UT to a constant level, or perform an operation to cut off input and output. 8 is a reference voltage whose positive electrode is connected to the negative output terminal 13', and one negative electrode is connected to one end of the input terminal of the error amplifier 7. 7 is an error amplifier, one of the two input terminals 12-12' is connected to the negative electrode of the reference voltage 8 as described above, and the other input terminal is connected to the negative input voltage side of the current detection resistor 19. are respectively connected to the current detection resistors 19
detects the potential drop and transmits it to the control section 11.

The operation of the conventional example will be explained below.

In FIG. 7, the current to be measured is applied to the winding a3 of the magnetic core 2 from the current to be measured terminal. When flowing, a magnetic field is generated in the gap. The magnetic path length of magnetic core 2 is 4° cross-sectional area S, magnetic permeability μ,
The length of the gap is l / , the cross-sectional area S. , the magnetic permeability of air is μ. When the number of turns in one winding 3 is N, the generated magnetic flux density B is. On the other hand, a voltage v0 is applied to the Hall element 4a from the DC power supply 5 to flow a current through the Hall element 4a, and a magnetic field B is generated in a direction perpendicular to this current. When VH is added, a potential difference vH is generated in a direction perpendicular to both the current and the magnetic field, and the relationship is expressed by the following equation.

V=4, v-B...
...(2) II Ho.

However, is called the product sensitivity and is a constant determined by the characteristics of the semiconductor material used.

Therefore, formulas (1) and (2) are obtained, and the current to be measured is It is possible to obtain a potential difference VH corresponding to VH, this potential difference VY is detected by an error amplifier 7, and an output signal is obtained from an output terminal 9. When the magnetic core 2 is cylindrical, the magnetic permeability μ of the magnetic core 2 is the magnetic permeability μ of air.

Since it can be considered that le-e' is much larger than 1 and = 1, equation (3) is v11=KM-v.・Toe・μo/l・・・・・・(4
)It can be expressed as.

Regarding the power supply device using current detection shown in FIG. 8, the current to be measured is connected to the current detection resistor 19. flows, the potential difference vRI9
is generated, and this vRI9 and the reference voltage V.

The error amplifier 7 detects the difference between Dvb''=vi+p−vF, and transmits the output signal of the error amplifier 7 to the control unit 11, which controls the output voltage to be constant or to control the voltage drop. This provides a protection function in the event of overcurrent.

Problems to be Solved by the Invention In such a conventional configuration, the method of detecting current using the Hall element 41L has large variations in the element itself.
The number and mobility of carriers change greatly with temperature, and the temperature characteristics are poor, so an external circuit for temperature compensation is required, and the output voltage is small. Although the detection accuracy is good because a resistor is used in the circuit, as the current capacity to be measured increases, the power consumed by the current detection resistor 19 increases, causing problems such as decreased efficiency and heat generation, and furthermore, There was a problem that the detection circuit could not be insulated.

The present invention is intended to solve these problems, and provides a current detection method with a simple configuration, good temperature characteristics, and less variation in elements, and reduces loss in the current detection section in a power supply device. This makes it possible to isolate the circuit to be detected and the detection circuit.

Means for Solving the Problem In order to solve this problem, the present invention includes a magnetoelectric transducer having a magnetoresistive effect and a magnetic core having a winding, and generates a magnetic field by passing a current to be measured through the winding. The output voltage of the magnetoelectric conversion element is detected by the magnetic field of the generated magnetic circuit. Further, a power supply device is configured using the above-described current detection method.

Effect: With this configuration, a magnetic field is generated in the magnetic circuit according to the current to be detected, the output voltage of the magnetoelectric transducer is changed by the generated magnetic field, and the current can be easily detected by detecting the output voltage. can.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, FIGS. 1 to 6.

FIG. 1 is a structural diagram of a current detection method according to an embodiment of the present invention. In FIG. 1, the same parts as in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted. 1-1' is a current terminal to be measured, 2 is a magnetic core, 3 is a winding, 6 is a DC power supply, 6-6' is an input terminal, 7 is an error amplifier, 8 is a reference voltage, and 9 is an output terminal.

4 is a magnetoelectric conversion element, which has a three-terminal configuration having current supply terminals a, c and an output terminal bl;
is connected to the input terminal 6-6', the output terminal is connected to one input terminal of the error amplifier 7, and the other input terminal of the error amplifier 7 is connected to the positive electrode of the reference voltage 8, and the output terminal is connected to the positive electrode of the reference voltage 8. The negative electrode of is connected to the negative input terminal 6', and the output voltage of the magnetoelectric conversion element 4 and the reference voltage 8 are detected by the error amplifier 7, amplified, and a signal is taken out from the output terminal 9.

To briefly explain the operating principle of the magnetoelectric transducer 4, as explained in Japanese Patent Publication No. 57-50θ7, the structure of the element has an anisotropic magnetoresistive effect, and two elements are arranged on the same plane. In two current paths made of ferromagnetic films arranged orthogonally to each other, an output terminal b is provided at the current contact point of the two current paths, and current supply terminals a and c are provided at the other end of each current path. The detection method of applying voltage v0 to
In the publication, the magnetic field strength is kept constant and the angle at which it is applied is changed, each of these resistance values is changed while the sum of the two resistance values is fixed, and the change in the voltage at the output terminal due to this change is calculated. In contrast, in the present invention, one of the two current paths arranged perpendicularly is always placed in the direction of the magnetic field, and the other is placed in the direction parallel to the magnetic field, and the magnetic field strength is varied to detect the output. It detects changes in terminal voltage.

The resistance value due to the magnetic field strength perpendicular to the current path is ρ (H5)
'Resistance value at 0 magnetic field is ρ. , Δρ is the resistance change width when a saturation magnetic field is applied perpendicular to the current path, and the strength of the magnetic field applied perpendicular to the current path is ■52 Material, shape, and shape of the ferromagnetic material
Letting the saturation magnetic field strength determined by the dimensions be H, the relationship between the magnetic field strength and the change in resistance value can be expressed by the following equation.

Note that when a magnetic field is applied parallel to the current path, the resistance value does not change. Therefore, if the current path on the terminal a side is arranged perpendicular to the direction of the magnetic field, the voltage at the output terminal A will increase as the magnetic field strength increases.

If this voltage is vb(1,5), then vb()I3. =(ρ./(ρ(+111 >+ρ.)
)・vo...(4)...The relationship is that they are perpendicular to each other, and an output voltage corresponding to the magnetic field strength can be obtained.

On the other hand, the magnetic field strength H8 generated in the magnetic circuit is as described in (1) above.
Considering the formula and the shape of the magnetic core, we get H, , = N-I. /l ・・・・・・(
6), the current to be measured. This voltage and the reference voltage 8 are detected by the error amplifier 7,
In the present invention, the current paths of two ferromagnetic films are connected in series as in Japanese Patent Publication No. 5-6067. Cancels the temperature change of the element itself,
This is also an effective means for improving the temperature characteristics of the output voltage of the output terminal. In other words, the same result can be obtained even if the current path perpendicular to the magnetic field is made of a ferromagnetic film and the parallel current path is made of a simple resistor.

FIG. 2 shows a specific circuit diagram of the structural diagram of FIG. 1, and since it is the same as FIG. 1, the explanation will be omitted.

FIG. 3 shows an embodiment in which two magnetoelectric transducers 4 shown in FIG. 1 are used. With respect to the applied voltage, the current paths arranged in the direction perpendicular to the magnetic field are reversed, and the change in the magnetic field causes the output voltage vb of one output terminal to rise and the output voltage vb' of the other to increase.7)
: By decreasing the voltage change width (7
) can be doubled, improving detection accuracy.

FIG. 4 is FIG. 1 showing an embodiment of a power supply device using the current detection method according to the present invention.

Components that are the same as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 4, reference numeral 20 denotes the current detection section in FIG. and the negative pole of the reference voltage 8 is connected to the negative output terminal 13', and the negative pole of the reference voltage 8 is connected to the output terminal 9.
is the negative input terminal 12' of the control unit 11, and the negative output terminal 13
′ respectively.

The operation of the current detection section 20 is the same as that shown in FIG. 1, and the operation of the control section 11 is the same as that shown in FIG. 8, so a description thereof will be omitted.

FIG. 5 shows the output voltage V according to the detected current in another embodiment of the present invention. A complete block diagram for controlling tlT to droop is shown. When the output voltage is controlled to drop as shown in FIG. 4, the voltage applied to the magnetoelectric transducer 4 also drops, and the output signal obtained from the output terminal 9 becomes the measured current voltage. It fluctuates without any hesitation. Therefore, the positive input terminal 12 and the current supply terminal are connected so that the voltage applied to the magnetoelectric conversion element 4 is always constant, so that the output signal is equal to the current to be measured in any state. This is to ensure that it does not fluctuate due to influences other than changes in .

FIG. 6 is a block diagram showing a case where a control section is provided on the primary side in a primary-side to secondary-side isolated type power supply device according to still another embodiment of the present invention. In FIG. 6, the same parts as in FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. 17 is a transformer υ, one end of the primary winding 171L is connected to the input terminal 12, and the other end is connected to the input terminal 12 via the switching element 16.
The AC voltage generated in the secondary winding 17b is converted into a DC voltage by the rectifying and smoothing section 18, and connected to the output terminal 13-13' via the current detecting section 20. Reference numeral 14 denotes an insulating signal transmission means, which transmits the output signal from the current detection section 20 to the oscillation control section 16 while insulating between the primary and secondary, and transmits the output signal from the current detection section 20 to the oscillation control section 16Fi, the current to be measured. The oscillation of the switching element 16 is controlled according to the output voltage V. . ? control. 10' is a DC power supply for the magnetoelectric conversion element 4, which is connected to keep the voltage applied to the element constant.

4, FIG. 6, and FIG. 6, it is clear that the detection accuracy of the current to be measured is improved by providing the current detection section 20 with the configuration shown in FIG. 3.

Effects of the Invention As described above, according to the present invention, a current detection method with a simple configuration, good temperature characteristics, and less variation in elements can be realized, and loss in the current detection section in a power supply device can be significantly reduced. Great effects such as making it possible to isolate the circuit to be detected and the detection circuit can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing a current detection method according to an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the structural diagram of FIG. 1 of the present invention, and FIG. 3 is a structural diagram of another embodiment of the present invention. The circuit diagram, FIG. 4 is a block diagram showing a power supply device using the current detection method according to one embodiment of the present invention, FIG. 6 is a block diagram of another embodiment of the present invention, and FIG. A structural diagram of a conventional current detection method, FIG. 8 is a block diagram of a power supply device using the conventional current detection method. 1-1'... Current terminal to be measured, 2... Magnetic core, 3... Winding wire, 4... Magnetoelectric conversion element,
41 River...Pole element, 6,1o...DC power supply, 6-6', 12-12'...Input terminal, 7.
...Error amplifier, 8...Reference voltage, 9
, 13-13'... Output terminal, 11...
Control unit, 14, insulation signal transmission means, 15...
・Oscillation control circuit, 16... switching element,
17...Transformer, 18... Rectifying and smoothing block, 20... Current detection section. Name of agent: Patent attorney Shigetaka Awano, 1 person, 1 person,
t゛ - Yokodo Sho 1i Uara Akiko 2 - && A: 3- Hassho 4゛ - Hoden 1 Akiwoko 5 - a FILt Minamototsu, 6'-Hitot + Shimako 7-! ll heather 1 chant dairy direct 1 power supply Wl county

Claims (2)

[Claims] (1) The output voltage of the magnetoelectric transducer is detected by the magnetic field of the magnetic circuit, which has a magnetoelectric transducer with a magnetoresistive effect and a magnetic core with a winding, and generates a magnetic field by passing the current to be measured through the winding. Current detection method. (2) A power supply device using the current detection method according to claim 1.