JPH02170061A - Electric power detecting device - Google Patents

Abstract

PURPOSE:To miniaturize the electric power detecting device by using a magneto resistance element as a magnetoelectric converting element. CONSTITUTION:A load 15 is connected to a power source 14. Electric power supplied to the load 15 is detected. The source voltage of the power source 14 is insulated electrically by a transformer 25 for insulation and then applied to terminals 22a and 22b of the magneto-resistance element 22. Further, the element 22 is applied with a magnetic field 32 produced by the magnetic field producing element 31 of the load 15 with a current I flowing through the load 15. Then the current path in the element 22 is deflected according to the intensity of the magnetic field 32 to cause variation in the resistance value. The output of the element 22 is proportion to both the magnetic field 32 and the voltage of the power source 14, so the element 22 functions as a multiplier and the output of the element 22 is obtained through a processing circuit 33 to obtain a detection output 39 which is proportional to the electric power. Thus, the magneto resistance element is used as the magnetoelectric converting element to increase the sensitivity by >=10 times as compared with a case wherein a conventional Hall element is used. Therefore, a cut core need not be used, so the device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Applications Prior Art (Figures 9 to 12) Problems to be Solved by the Invention Examples of Means and Actions for Solving the Problems First Embodiment of the Invention (1 to 12) Figure 6) Second aspect of the present invention
Embodiment (Fig. 7) Third embodiment of the present invention (Fig. 8) Effects of the invention [Summary] Regarding the power detection device, the device can be configured without using an analog multiplier or a cut core, and is small and compact. The purpose of the present invention is to provide an inexpensive power detection device, which includes a magnetoelectric transducer that is driven by a voltage proportional to the voltage supplied to a predetermined load and to which a magnetic field generated by a current flowing through the load is directly applied, and a magnetoelectric transducer that is Bias application means for applying a predetermined bias magnetic field to the conversion element; magnetic blocking means provided around the magnetoelectric conversion element for blocking non-detection magnetic fields; and processing the output of the magnetoelectric conversion element to detect electric power. A processing circuit is provided, and the magnetoelectric conversion element is configured to detect power supplied to the load by multiplying the voltage and current and outputting the result to the processing circuit.

[Industrial application field]

The present invention relates to a power detection device, and more particularly to an electronic power detection device using a magnetoelectric conversion element as a multiplier.

In recent years, with the rapid development of microcomputer technology,
There is an increasing demand for miniaturization and electronicization of sensor devices as input devices. Regarding wattmeters, in anticipation of the future development of the home electronics field, there will be a need for small and inexpensive electronic wattmeters.

[Conventional technology]

Conventionally, as this type of electronic wattmeter, for example, the 9th to 12th
There is something like the one shown in the figure. Fig. 9 is a principle diagram showing the general principle of a power detector, Fig. 10 is an operating waveform diagram of the power detector, Fig. 11 is a configuration diagram showing a power detector using an analog multiplier, and Fig. 121F is a diagram showing the power detector using an analog multiplier. FIG. 2 is a configuration diagram showing a power detector using a pole element.

In FIG. 9, 1 is a power detector, and power detector 1
is composed of a current/voltage conversion circuit 2, a multiplier 3, and a processing circuit 4. The load current input to the current/voltage conversion circuit 2 is converted into a voltage by the current/voltage conversion circuit 2 and output to the multiplier 3, and the multiplier 3 multiplies the converted voltage and the load voltage to obtain the multiplication result. is output to the processing circuit 4. The processing circuit 4 processes the input multiplication result into an appropriate signal output and outputs it to the outside as a power output. FIG. 10 is an operating waveform diagram of the power detector 1, and the figure shows the power output when voltage (2) and current I shown in the following equation (2) are input to the power detector 1 as the load voltage and current. Figure (a) is ■,
If there is no phase shift in ■ (φ-〇), the same figure (b) is φ
The case of −90° is shown.

However, ■o: Amplitude ■o: Amplitude φ: Phase Power measurement is basically to detect the voltage and current applied to the load as described above, and to obtain the power output by multiplying the load voltage and load current. From a technical point of view, how to perform multiplication is an important point.

For example, the power detector 5 shown in FIG. 11 is an example in which an analog multiplier 6 based on semiconductor IC technology is used as a multiplier, and the power detector 10 shown in FIG. 12 is an example in which a Hall element is used. In FIGS. 12(a) and 12(b), 10 is a power detector, and the power detector 10 is composed of a Hall element 11, a cut core 12, and a differential amplifier 13. Consider a case where a load 15 is connected to the power source 14 and the power supplied to the load 15 is detected. Figure 12 (b
), the Hall element 11 is arranged in parallel with the power supply 14, and the Hall element 11 is driven by the power supply voltage from the power supply 14, and the magnetic field 1 created by the current I flowing through the load 15 is
6 is received by a Hall element 11 using a cut core 12, and the output of the Hall element 11 is obtained through a differential amplifier 13, thereby obtaining a detection output 17 proportional to the electric power.

[Problem to be solved by the invention]

However, in such conventional power meters, those that use analog multipliers cannot be used as inexpensive power detection devices because the analog multiplier itself is expensive, and those that use Hall elements are There was a problem in that the device inevitably became larger due to the structure using the core.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a small and inexpensive power detection device that can be configured without using analog multipliers or cut cores.

[Means for Solving the Problems] In order to achieve the above object, the power detection device according to the present invention is driven by a voltage proportional to the voltage supplied to a predetermined load, and a magnetic field generated by a current flowing through the load is directly applied. a bias applying means for applying a predetermined bias magnetic field to the magnetoelectric transducer, a magnetic blocking means provided around the magnetoelectric transducer for blocking non-detected magnetic fields, a processing circuit that processes output and detects electric power, and the magnetoelectric conversion element detects electric power supplied to the load by multiplying the voltage and current and outputting the result to the processing circuit. Equipped with a power detection device featuring:

[Effect]

The present invention includes a magnetoelectric transducer to which a magnetic field generated by a voltage supplied to a predetermined load and a current flowing through the load is applied, a bias applying means for applying a predetermined bias magnetic field to the magnetoelectric transducer, and A magnetic blocking means is provided around the conversion element to block an undetected magnetic field, and a processing circuit is provided to process the output of the magnetoelectric conversion element to detect electric power, and the magnetoelectric conversion element detects the voltage and current. is multiplied and output to the processing circuit.

When a magnetoresistive element is used as the magnetoelectric conversion element, the sensitivity is more than 10 times higher than that of a Hall element.
Devices can be configured without using cut cores,
Devices can be made smaller.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

1 to 6 are diagrams showing a first embodiment of the power detection device according to the present invention, FIG. 1 is an overall configuration diagram of a power detector using a magnetoresistive element, and FIG. 2 is a diagram showing a power detector using a magnetoresistive element. The configuration diagram of the bias magnetic field magnet, Figure 3 is the characteristic diagram of the magnetoresistive element when a bias magnetic field is applied, Figure 4 is the magnetic shielding characteristic diagram of the shield case, Figure 5 is the transfer characteristic diagram of the isolation transformer, FIG. 6 is a circuit diagram of a power detector using a magnetoresistive element.

First, the configuration will be explained. Components that are the same as those of the conventional example shown in FIG. 12 are given the same numbers and their explanations will be omitted.

In FIG. 1, 21 is a power detector (power detection device), and the power detector 21 applies a predetermined bias magnetic field to a bridge-connected magnetoresistive element (magnetoelectric conversion element) 22 and the magnetoresistive element 22. A bias magnetic field applying magnet (bias applying means) 23, a circuit board 24 to which a processing circuit for amplifying and processing sensor output, etc. are attached, an insulating transformer 25 for electrically insulating the circuit section, and a power source 1.
4 and the load 15 are connected to the terminals 26 and 27, and a shield case (magnetic shielding means) 28 that shields the inside from external magnetic fields. A magnetoresistive element 22 and a bias magnetic field applying magnet 23 for applying a bias magnetic field in a predetermined direction to the magnetoresistive element 22 are disposed facing each other at the terminal 26 .
27 and the insulating transformer 25 are attached to the circuit board 24, and the magnetoresistive element 22 and the bias magnetic field applying magnet 2 are attached to the circuit board 24.
3. Circuit board 24, insulation transformer 25 and terminal 26
．． A portion of 27 is sealed within a shield case 28 to prevent the influence of external magnetic fields.

A load 15 is connected to the power source 14 via terminals 26 and 27 and is supplied with power. A load current {circle around (2)} flows from the power supply 14 to the load 15 through terminals 26 and 27, and the magnetic resistance element 22 receives the magnetic field created by the load current I flowing through the terminal 26. In this embodiment, a magnetoresistive element 22 made of, for example, a Ni--Fe alloy thin film is used as the magnetoelectric conversion element. Further, as shown in FIG. 2, the configuration of the bias magnetic field applying magnet 23 is as follows:
The bias magnetic field applying magnet 23 is arranged so that the bias magnetic field direction of the bias magnetic field applying magnet 23 is as shown in the figure with respect to the magnetic field detection direction. FIG. 3 shows the output characteristics of the magnetoresistive element 22 when a bias magnetic field is applied with the configuration shown in FIG. 2. Apply a bias magnetic field Hex as shown in Figure 3 (Hex = 0, 40.80, 120
It can be seen that the linearity and saturation characteristics are improved according to Cθe) (however, the sensitivity is maximum when Hex=0). Therefore, depending on the application, the bias magnetic field He
By switching x, the sensitivity or dynamic range of the magnetoresistive element 22 can be selected. The shield case 28 has the shape shown in FIG. 4(a), and is made of PC (JIS) material. Its magnetic shielding characteristics are shown in FIG. 4(b).

In addition, the insulating transformer 25 is provided between the power supply 14 and the internal circuit section as shown in FIG. Outputs a proportional voltage Vout. Note that 29.30 is a resistor. The transfer characteristics of this isolation transformer 25 are shown in FIG. 4(b), and it can be seen that the characteristics become saturated and become approximately flat when the frequency exceeds 5011z.

FIG. 6 shows an example of the circuit configuration of the power detector 21 using the magnetoresistive element 22, and is a circuit for amplifying and processing the output of the magnetoresistive element 22. Components that are the same as those shown in FIG. 1.5) are given the same numbers.

In FIG. 6, the magnetoresistive element 22 is configured by a bridge connection, and a voltage proportional to the power supply voltage is applied to the terminal 22a of the bridge via an insulating transformer 25.
The other terminal 22b of the bridge is grounded. Furthermore,
A magnetic field 32 generated by a magnetic field generating element 31 of the load 15 is applied to the magnetoresistive element 22 by a current I flowing through the load 15, and output terminals 22c and 22d of the bridge are connected to a processing circuit 33, respectively. Processing circuit 33
is composed of a differential amplifier 34 and resistors 35 to 38,
The output of the magnetoresistive element 22 is amplified and processed to provide a detection output 39.
Output as .

Next, the effect will be explained.

As shown in FIG. 6, a load 15 is connected to the power source 14, and if the power supplied to the load 15 is to be detected, the power supply voltage of the power source 14 is electrically isolated by an insulating transformer 25. After that, the terminals 22a, 2 of the magnetoresistive element 22
2b, while a load 15 is applied to the magnetoresistive element 22.
A magnetic field 32 generated by the magnetic field generating element 31 of the load 15 is applied to the current I flowing through the load 15, and the current path inside the magnetoresistive element 22 is deflected depending on the strength of the current I (that is, the strength of the magnetic field 32). The resistance value changes rapidly. Since the output of the magnetoresistive element 22 is proportional to both the magnetic field 32 and the voltage of the power supply 14, the magnetoresistive element 22 has a function as a multiplier, and the output of the magnetoresistive element 2
By obtaining the output of 2 through the processing circuit 33, a detection output 39 proportional to the electric power can be obtained.

As described above, in this embodiment, the magnetoresistive element 22 is used as a multiplier, and is further provided with a bias applying magnet 23, a shield case 28, a processing circuit 33, and an insulating transformer 25. Since the magnetoresistive element 22 has a sensitivity more than 10 times higher than that of the Hall element, the sensitivity shown in FIG. 12 (
The device can be constructed without using the cut core 12 as shown in a), and the device can be made compact. Furthermore, since no expensive analog multiplier is used, the device can be made inexpensive, and can be widely applied to fields such as Bohm electronics.

FIG. 7 is a diagram showing a second embodiment of the power detection device according to the present invention, and is an example in which the power detector 21 is provided with a temperature compensation circuit. Components that are the same as those in FIG. 6 shown in the first embodiment are given the same numbers and will not be described again. In Figure 7,
41 is a temperature-sensitive resistor, 42 is a variable resistor for adjustment, and the temperature-sensitive resistor 41 and the variable resistor for adjustment 42 are the magnetoresistive element 2.
2 output terminals 22C122d, respectively.

Even when the magnetic field 32 is not applied, if the resistances of the magnetoresistive elements 22 match perfectly, the voltages across the bridge should be equal. However, in reality, they may not always match, and the may not become zero and an offset voltage may remain.

Since this offset voltage has temperature characteristics, errors occur in detection, so it is necessary to compensate for these temperature characteristics. Here, the temperature drift can be known in advance through experiments or the like. Therefore, for example, if the voltage of the magnetoresistive element 22 has a characteristic of decreasing as the temperature rises, if a temperature-sensitive resistor 41 having a positive temperature characteristic is used, the overall voltage will be flat. . In this case, an adjustment variable resistor 42 is used for adjustment so as not to upset the balance of the bridge.

Therefore, by compensating for drift due to temperature, the effects of the first embodiment can be further enhanced.

FIG. 8 is a diagram showing a third embodiment of the power detection device according to the present invention, and the same components as in FIG. 1 of the first embodiment are given the same numbers. In this embodiment, only the portion of the terminal 26 where the magnetoresistive element 22 is provided is covered with the shield case 43. Therefore, further miniaturization of the device can be achieved.

[Effects of the Invention] According to the present invention, a device can be configured without using an analog multiplier or a cut core, and a small and inexpensive power detection device can be realized.

[Brief explanation of the drawing]

1 to 6 are diagrams showing a first embodiment of the power detection device according to the present invention, FIG. 1 is an overall configuration diagram of the power detector, and FIG. 2 is a diagram showing the magnetoresistive element and bias magnetic field magnet. Fig. 3 is a characteristic diagram of the magnetoresistive element when the bias magnetic field is applied, Fig. 4 is a magnetic shielding characteristic diagram of its shield case, Fig. 5 is a transfer characteristic diagram of its isolation transformer, and Fig. 6 is a circuit configuration diagram of the power detector, FIG. 7 is a circuit diagram of the power detector showing a second embodiment of the power detection device according to the present invention, and FIG. 8 is a circuit diagram of the power detection device according to the present invention. An overall configuration diagram showing the third embodiment, Figures 9 to 12 are diagrams showing a conventional power detection device, Figure 9 is a principle diagram showing the general principle of the power detector, and Figure 10 is a diagram showing the general principle of the power detector. FIG. 11 is a block diagram showing the power detector using the analog multiplier; FIG. 12 is a block diagram showing the power detector using the Hall element. 14...Power source, 15...Load, 21...Power detector (power detection device), 22...
... Magnetoresistive element (magnetoelectric conversion element), 22a, 2
2b...terminal, 22c, 22d...output terminal, 23...
- Magnet for applying bias magnetic field (bias applying means), 24... Circuit board, 25... Insulating transformer, 26.27... Terminal, 28.43... ...Shield case (magnetic blocking means), 29.30.35-38...Resistor, 31
...Magnetic field generating element, 32...Magnetic field, 33...Processing circuit, 34...Differential amplifier, 39...Detection output, 41... Angry temperature resistor, 42... Adjustable variable resistor. Circuit configuration diagram of the power detector of the second embodiment Overall configuration diagram of the third embodiment Figure 8

Claims (1)

[Scope of Claims] A magnetoelectric transducer that is driven by a voltage proportional to a voltage supplied to a predetermined load and to which a magnetic field generated by a current flowing through the load is directly applied, and a predetermined bias magnetic field to the magnetoelectric transducer. a bias applying means for applying a voltage, a magnetic blocking means provided around the magnetoelectric transducer to block an undetected magnetic field, and a processing circuit for processing the output of the magnetoelectric transducer to detect electric power. . A power detection device, wherein the magnetoelectric conversion element detects the power supplied to the load by multiplying the voltage and current and outputting the result to the processing circuit.