JP2010127636A - Magnetic proportion system current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost magnetic proportion system current sensor in which gain adjustment is simplified by eliminating the change in offset voltage resulting from the gain adjustment because it is not necessary to change the drive current of a magnetic detection element such as a hall element when the gain adjustment is performed. <P>SOLUTION: When adjusting the magnetic proportion system current sensor, first, a drive current I<SB>C</SB>of a hall element 16 is fixed, then, influence of an offset voltage is adjusted by adjusting a resistance of a resistor R<SB>2</SB>of an intermediate voltage generating circuit 26, and thereafter the gain of a differential amplifier 22 is adjusted by adjusting a resistance of a resistor R<SB>T</SB>(gain adjustment is performed). Because the drive current I<SB>C</SB>of the hall element 16 does not change owing to the adjustment of the gain of the differential amplifier 22, it is not necessary to consider the change in the offset voltage resulting from the change in the drive current I<SB>C</SB>. Namely, no repeated offset adjustment or complex calculation in consideration of the same is required, and thus a gain adjustment process is simplified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic proportional current sensor that measures a battery current of a hybrid car or an electric vehicle, a motor driving current, and a current flowing through a motor of a machine tool using a magnetic detection element such as a Hall element.

  2. Description of the Related Art Conventionally, magnetic proportional sensors shown below have been known as current sensors that detect a current flowing through a bus bar (current to be measured) in a non-contact state using a magnetic detection element such as a Hall element.

As illustrated in FIG. 7, the magnetic proportional current sensor includes a ring-shaped magnetic core 20 having a gap G (such as a silicon steel plate or a permalloy core with high permeability and low residual magnetism), and a hole disposed in the gap G. And an element 16 (an example of a magnetic detection element). The magnetic core 20 is an arrangement in which the bus bar 10 of the flow of the current I _in the measurement through. Therefore, a magnetic field is generated in the gap G due to the current I _{in to} be measured, and this is applied to the magnetic sensitive surface of the Hall element 16. Since the intensity of the magnetic field is proportional to the measured current I _in, the measured current I _in is determined from the output voltage of the Hall element 16. The circuit configuration of the magnetic proportional current sensor is as shown in FIG. 8, for example. In this circuit, the output voltage of the Hall element 16 driven at a constant current is amplified by a differential amplifier circuit to obtain a sensor output.

Further, in recent years, a magnetic proportional current sensor having a coreless structure that does not use a ring-shaped magnetic core as shown in FIGS. FIG. 10 is a characteristic diagram illustrating the relationship between the measured current I _in flowing through the bus bar 10 and the magnetic field (magnetic flux density B) applied to the magnetic sensitive surface of the Hall element 16 in the case of FIG. The magnetic field (magnetic flux density B) applied to the magnetosensitive surface of the Hall element 16 varies linearly (proportional) in the range of −50 mT to +50 mT with respect to the range of the current to be measured I _in from −1000 A to +1000 A. Therefore, even in the case of the coreless structure, the magnetic field generated by the measured current I _in is applied to the magnetic sensitive surface of the Hall element 16, and the measured current I _in is obtained from the output voltage of the Hall element 16.

By the way, the sensitivity of the Hall element differs from element to element, and since the gap length of the magnetic core cannot be made constant, the sensor output for the current to be measured is set to a desired value (for example, sensor output V _out = 2.5 V ± 2 V [ In order to make the current to be measured full scale ± 400 A]), it is necessary to adjust the gain of the current sensor.

Regarding the gain adjustment, in the current sensor device disclosed in Patent Document 1 below, “the first trimming resistor 3 for adjusting the driving constant current of the Hall element 1 is provided”, and “the first trimming resistor 3 is a current "Function as gain adjusting means of sensor device" (paragraph [0017]). Patent Document 1 inputs “a gain adjustment target value obtained by correcting an amount of change in offset voltage caused by gain adjustment” to “first trimming resistor 3” (same paragraph), and sets the offset voltage after gain adjustment. By adjusting, “Providing a method for adjusting the current sensor device for the purpose of low cost, which eliminates the need to discard or re-trim the board and requires only a small adjustment process” ([Summary] [Problem]) Yes.
JP 2008-241552 A

  If the drive current of the Hall element is changed for gain adjustment, there is a drawback that the offset voltage (the output voltage of the Hall element when the current to be measured is 0 A) changes with the change of the drive current. In Patent Document 1, in order to overcome the above drawbacks, “a gain adjustment target value obtained by correcting a change amount of an offset voltage caused by gain adjustment” is input to “first trimming resistor 3”, and the offset voltage is adjusted after gain adjustment. Although adjustment is required, since complicated calculations as described in the paragraphs [0020] to [0024] of the same document are required, it takes time and effort to design the current sensor, which tends to increase costs. There is a problem.

  The present invention has been made in view of such a situation, and its purpose is to eliminate the need to change the drive current of a magnetic detection element such as a Hall element in gain adjustment, and to eliminate the change in offset voltage accompanying gain adjustment. Thus, an object of the present invention is to provide a low-cost magnetic proportional current sensor with simplified gain adjustment.

One embodiment of the present invention is a magnetic proportional current sensor. This magnetic proportional current sensor
A magnetic sensing element to which a magnetic field generated by a current to be measured is applied;
A drive circuit for driving the magnetic detection element at a constant voltage or a constant current;
A differential amplifier that amplifies the output voltage of the magnetic detection element;
The differential amplifier includes an operational amplifier, first to sixth resistors, and a trimmable resistor or a variable resistor.
The first resistor is provided in a path connecting one output terminal of the magnetic detection element and the inverting input terminal of the operational amplifier, and connects the other output terminal of the magnetic detection element and the non-inverting input terminal of the operational amplifier. The second resistor is provided in a path to be connected, the third and fourth resistors are connected in series to a path connecting the output terminal of the operational amplifier and the inverting input terminal, and the non-inverting input terminal and the reference voltage terminal are connected to each other. The fifth and sixth resistors are connected in series to the path connecting the three, and the trimmable resistance is connected to the path connecting the connection point of the third and fourth resistors and the connection point of the fifth and sixth resistors. Alternatively, the variable resistor is provided, the first and second resistors have the same resistance value, and the third to sixth resistors have the same resistance value.

  In one aspect of the magnetic proportional current sensor, the first to sixth resistors may be fixed resistors.

In an aspect of the magnetic proportional current sensor,
A ring-shaped magnetic core having a gap portion surrounding the path of the current to be measured;
The magnetic detection element may be located in the gap portion.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, the gain of the magnetic proportional current sensor can be adjusted by adjusting the gain of the differential amplifier by adjusting the resistance value of the trimmable resistor or variable resistor. There is no need to change the drive current of the magnetic detection element. Therefore, it is possible to eliminate the change in the offset voltage accompanying the gain adjustment, and to realize a low-cost magnetic proportional current sensor that simplifies the gain adjustment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a circuit diagram of a magnetic proportional current sensor 100 according to an embodiment of the present invention. The magnetic proportional current sensor 100 includes a power supply terminal 12 as a high voltage terminal, a ground terminal 14 as a low voltage terminal, a sensor output terminal 15, a Hall element 16 as a magnetic detection element, and a constant current as a drive circuit. A circuit 18, a differential amplifier 22, a voltage dividing circuit 24, and an intermediate voltage generation circuit 26 are provided.

The power supply terminal 12 and the ground terminal 14 are connected to a DC voltage source (here, the power supply voltage V _CC = 5 V as an example), the power supply terminal 12 is on the high voltage side, and the ground terminal 14 is grounded on the low voltage side. Hall element 16 is, for example, InAs system, are fixedly arranged to the illustrated manner the magnetic core 20 in the gap portion G in FIG. 7 (ie, the position where the magnetic field generated by the current to be measured I _in is applied).

FIG. 2A is a schematic explanatory diagram of the magnetic field (magnetic flux density B in the gap) applied to the Hall element 16, and FIG. 2B is an exemplary magnetic flux density B _in the gap with respect to the measured current Iin. FIG. The magnetic flux density B in the gap varies linearly in the range of −50 mT to +50 mT (in proportion to the range of the current to be measured I _in of −400 A to +400 A (rated by the magnetic proportional current sensor 100)). )

In FIG. 1, the Hall element 16 is equivalently represented by a bridge connection of four resistors. By keeping flowing a constant driving current I _C between the current supply terminals a, b of the Hall element 16, is proportional to the magnetic field applied to the Hall element 16 (proportional to in other words the measurement current I _in) Voltage V _H is obtained between the output terminals c and d.

FIG. 3 is a characteristic diagram illustrating the relationship between the drive current I _C of the Hall element 16 and the output voltage V _H in the magnetic proportional current sensor 100. Conditions 25 ° C. ambient temperature T _a, is set to 50mT the gap magnetic flux density B. As shown in the figure, the Hall element 16 has an output voltage V _H that increases as the drive current I _C increases. Therefore, it can be said that the drive current I _C of the Hall element 16 is more desirable as it is designed to be close to the maximum rating (for example, 10 mA). Therefore, in this embodiment, as an example, the drive current I _C is set (fixed) to 9 mA. As described later, the point is that the drive current I _C does not change by the gain adjustment of the magnetic proportional current sensor 100.

FIG. 4 is a characteristic diagram illustrating the relationship between the drive current I _C of the Hall element 16 and the offset voltage V _ofs in the magnetic proportional current sensor 100. Conditions 25 ° C. ambient temperature T _a, is set to 0mT the gap magnetic flux density B. As shown in this figure, the Hall element 16 has a larger offset voltage V _ofs as the drive current I _C increases. That is, the offset voltage V _ofs varies depending on the magnitude of the drive current I _C. For this reason, as described in Patent Document 1, when the drive current I _C is changed for gain adjustment, there arises a problem that the offset voltage V _ofs changes. Therefore, in the present embodiment has a configuration that does not change the driving current I _C when the gain adjustment as described below.

In FIG. 1, a constant current circuit 18 drives the Hall element 16 with a constant current. The voltage dividing circuit 24 divides the power supply voltage V _CC at a predetermined ratio. This _divided voltage V _dv becomes a drive voltage for the constant current circuit 18. The differential amplifier 22 amplifies the output voltage V _H of the Hall element 16 and outputs it from the sensor output terminal 15 (sensor output voltage V _out ). The intermediate voltage generation circuit 26 divides the power supply voltage at a predetermined ratio and outputs it. The output voltage V _md of the intermediate voltage generation circuit 26 becomes a reference voltage for the differential amplifier 22.

  Hereinafter, the circuit configuration of the magnetic proportional current sensor 100 will be described more specifically.

  The Hall element 16 and the constant current circuit 18 are connected in series between the power supply terminal 12 and the ground terminal 14 so that the Hall element 16 is on the power supply terminal 12 side. That is, the current supply terminal a of the Hall element 16 is connected to the power supply terminal 12, and the constant current circuit 18 is provided between the current supply terminal b of the Hall element 16 and the ground terminal 14.

The voltage dividing circuit 24 includes resistors R ₃ and R ₄ connected in series between the power supply terminal 12 and the ground terminal 14, and a voltage at the connection point of the resistors R ₃ and R ₄ ( _divided voltage V _dv ). Is output to the constant current circuit 18. The _divided voltage V _dv is
_{V dv = (R 4 / (} R 3 + R 4)) × V CC ... formula (1)
It is expressed. The voltage dividing ratio by the resistors R ₃ and R ₄ is, for example, 4: 1. In this case, the _divided voltage V _dv is 1V.

The constant current circuit 18 includes an NPN bipolar transistor Q as an N channel transistor, a current setting resistor R _5, and an operational amplifier 32 (operational amplifier). The NPN bipolar transistor Q and the current setting resistor R ₅ are connected in series between the current supply terminal b of the Hall element 16 and the ground terminal 14 so that the NPN bipolar transistor Q is on the current supply terminal b side. The That is, the collector of the NPN bipolar transistor Q is connected to the current supply terminal b of the Hall element 16, and the current setting resistor R ₅ is provided between the emitter of the NPN bipolar transistor Q and the ground terminal 14. Operational amplifier 32, the divided voltage V _dv from the voltage dividing circuit 24 is input to the non-inverting input terminal, an inverting input terminal connected to a connection point between NPN bipolar transistor Q and the current setting resistor R _5, an output terminal Is connected to the control terminal (base terminal) of the NPN bipolar transistor Q.

With this connection, the voltage between the non-inverting input terminal and the inverting input terminal of the operational amplifier 32 is always zero due to negative feedback (imaginary short is established). That is, the voltage at the inverting input terminal of the operational amplifier 32 (the voltage at the emitter of the NPN bipolar transistor Q) is equal to the voltage at the non-inverting input terminal of the operational amplifier 32 (the divided voltage V _dv from the voltage dividing circuit 24). Therefore, the current flowing through the current setting resistor R ₅ , that is, the Hall element drive current I _C is
I _C = V _dv / R ₅ [A] (2)
Therefore, it is constant regardless of the internal resistance of the Hall element 16. The Hall element drive current I _C is set to 9 mA, for example.

The intermediate voltage generation circuit 26 includes resistors R ₁ and R ₂ connected in series between the power supply terminal 12 and the ground terminal 14, and a voltage at the connection point of the resistors R ₁ and R ₂ (intermediate voltage V _md ). Is output to the differential amplifier 22. The intermediate voltage V _md is
V _md = (R ₂ / (R ₁ + R ₂ )) × V _CC Formula (3)
It is expressed. The voltage dividing ratio by the resistors R ₁ and R ₂ is, for example, 1: 1, and in this case, the intermediate voltage V _md is 2.5V. In order to adjust the influence of the offset voltage of the Hall element 16, _one of the resistors R ₁ and R ₂ (the resistor R _{2 in} FIG. 1) is a variable resistor, and the differential when the measured current I _in is 0 A. The intermediate voltage V _md can be finely adjusted so that the output voltage V _out of the amplifier 22 becomes 2.5V.

Differential amplifier 22 includes an operational amplifier 38, a resistor R ₆ to R ₁₁ as the first to sixth resistor, and R _T resistor as trimmable resistor. Preferably, the resistors R _{6 to} R ₁₁ are high-precision fixed resistors, not low-precision semi-fixed resistors or laser trimming resistors. For example, a laser trimming resistor is used as the resistor _RT .

A resistor R ₆ is provided in a path connecting the output terminal d of the Hall element 16 and the inverting input terminal of the operational amplifier 38, and a resistor R ₆ is connected in a path connecting the output terminal c of the Hall element 16 and the non-inverting input terminal of the operational amplifier 38. ₇ is provided, the resistor R ₈ and R ₉ an output terminal and a path connecting the inverting input terminal of the operational amplifier 38 are connected in series, the output of the non-inverting input terminal and the reference voltage terminal (the intermediate voltage generating circuit 26 Resistors R ₁₀ and R ₁₁ are connected in series to the path connecting the terminals), and a resistor _RT is provided on the path connecting the connection points of the resistors R ₈ and R _{9 and} the connection points of the resistors R ₁₀ and R _11. It is done. The resistors R ₆ and R ₇ have the same resistance value, and the resistors R _{8 to} R ₁₁ have the same resistance value (R ₆ = R ₇ , R ₈ = R ₉ = R ₁₀ = R ₁₁ ). The resistance value of the resistor _RT is K × R ₁₂ (K is an arbitrary positive real number) (where R ₈ = R ₉ = R ₁₀ = R ₁₁ = R ₁₂ ).

The output voltage V _out (sensor output voltage) of the differential amplifier 22 is
V _out = V _md +2 (1 + 1 / K) × (R ₁₂ / R ₆ ) × V _H [V] (4)
Indicated by Therefore, the amplification degree of the differential amplifier 22 can be adjusted by adjusting the resistance value of the resistor _RT (= K × R ₁₂ ) (the resistors R _{6 to} R ₁₁ do not require adjustment of the resistance value).

When adjusting the magnetic proportional current sensor 100, first, the drive current I _C of the Hall element 16 is set (fixed) to, for example, 9 mA, and then the resistance value of the resistor R ₂ (variable resistor) of the intermediate voltage generating circuit 26 is set. And the intermediate voltage V _md is adjusted so that the output voltage V _out of the differential amplifier 22 when the measured current I _in is 0 A is 2.5 V, and then the resistance value of the resistor _RT (= K XR ₁₂ ) is adjusted to adjust the amplification degree of the differential amplifier 22 (that is, the gain of the magnetic proportional current sensor 100 is adjusted). The differential amplifier 22 amplifies the output voltage V _H (for example, several tens of mV) of the Hall element 16 by several tens of times to obtain, for example, V _out = 2.5 V ± 2 V (full scale of the measured current I _in ± 400 A). Output. Since the drive current I _C of the Hall element 16 does not change by adjusting the amplification factor of the differential amplifier 22, it is not necessary to consider the change in the offset voltage due to the change in the drive current I _C. That is, it is not necessary to perform the offset adjustment again and complicated calculation considering it, and the gain adjustment process can be simplified.

  According to the present embodiment, the following effects can be achieved.

(1) Since the gain of the magnetic proportional current sensor 100 can be adjusted by adjusting the gain of the differential amplifier 22 by adjusting the resistance value of the resistor _RT as a resistor that can be trimmed, the Hall element 16 is used for gain adjustment. it is not necessary to change the drive current I _C of. Therefore, unlike the case where the Hall element drive current is changed for gain adjustment as described in Patent Document 1, it is possible to eliminate the change of the offset voltage accompanying the gain adjustment, and the gain adjustment is simplified with good workability. A cost-proportional magnetic current sensor can be realized.

(2) there is no need to change the drive current I _C of the Hall element 16 when the gain adjustment of the magnetic proportional current sensor 100, to change the drive current of the Hall element for gain adjustment as described in Patent Document 1 Compared to the case, the drive current I _C of the Hall element 16 can be set close to the maximum rating (for example, 10 mA) (for example, 9 mA) to increase the sensitivity of the Hall element 16, and the current detection accuracy can be increased.

(3) Since the resistance values of the resistors R _{6 to} R ₁₁ do not need to be adjusted when adjusting the amplification degree of the differential amplifier 22, the CMR (Common Mode Rejection) of the differential amplifier 22 is lowered to adjust the amplification degree. It is possible to prevent the inconvenience. This will be described below.

Since the differential amplifier 22 is considered as an amplifier in which both an inverting amplifier and a non-inverting amplifier are overlapped, the relationship between the resistance values of the resistors R _{6 to} R ₁₁ (R ₆ = R ₇ , R ₈ = R ₉ = R _{When 10} = R ₁₁ ) is broken, the CMR when the in-phase component enters the differential amplifier 22 at the inverting input terminal and the non-inverting input terminal is lowered, and the differential amplifier 22 is separated from the ideal differential amplifier. Is likely to occur. In the case of an ideal differential amplifier, for example, even if in-phase noise enters, the output becomes zero (only the differential voltage is amplified accurately).

Here, when adjusting the gain by adjusting the resistance values of the resistors R _{8 to} R ₁₁ (or resistors R ₆ and R ₇ ) as semi-fixed resistors or laser trimming resistors, the adjusted resistors It is extremely difficult to make the values equal (to satisfy R ₈ = R ₉ = R ₁₀ = R ₁₁ (or R ₆ = R ₇ )). Will fall away from the ideal differential amplifier.

On the other hand, according to the present embodiment, the amplification degree of the differential amplifier 22 can be adjusted by adjusting the resistance value of the resistor _RT as a resistor that can be trimmed as described above, and the resistance values of the resistors R _{6 to} R ₁₁ are Since adjustment is not necessary, high-precision fixed resistors can be used as the resistors R _{6 to} R ₁₁ . Therefore, the relationship between the resistance values of the resistors R _{6 to} R ₁₁ (R ₆ = R ₇ , R ₈ = R ₉ =) for adjusting the amplification degree of the differential amplifier 22 (ie, adjusting the gain of the magnetic proportional current sensor 100). R ₁₀ = R ₁₁ ) does not collapse, and a state close to an ideal differential amplifier can be maintained.

  The present invention has been described above by taking the embodiment as an example. However, it will be understood by those skilled in the art that various modifications can be made to each component of the embodiment within the scope of the claims. Hereinafter, modifications will be described.

In the embodiment, consideration for the temperature characteristics of the Hall element 16 is not particularly mentioned. However, in the modified example, the resistance R ₄ of the constant current circuit 18 is used as a temperature compensation resistor, for example, a positive temperature coefficient resistor (thermistor), which accompanies temperature change. The accuracy of the magnetic proportional current sensor 100 may be compensated. That is, the Hall element 16 is constant gap magnetic flux density B as illustrated in FIG. 5 (e.g., 50 mT) and the driving current I _C ambient temperature if constant (e.g. 10 mA) is T _a is higher than the output voltage V _H is where tend to be small, if the resistance R ₄ of the constant current circuit 18 and the positive temperature coefficient resistor, a Hall element 16 increases divided voltage V _dv from the voltage dividing circuit 24 the higher the ambient temperature T _a Drive current I _C becomes larger (see the above equation (2)), the sensitivity of the Hall element 16 is increased and the influence of temperature characteristics is compensated. Instead of the resistor R ₄ , the resistor R ₃ may be a temperature compensation resistor (negative temperature coefficient resistor (thermistor)).

  In the embodiment, the case where the transistor used in the constant current circuit is an NPN bipolar transistor has been described. However, in a modified example, a PNP bipolar transistor or a field effect transistor may be used. The configuration of the constant current circuit in this case is shown in FIGS.

FIG. 6A shows the case where a PNP bipolar transistor is used. In this case, the current setting resistor R ₉ and the PNP bipolar transistor Q are connected in series such that the current setting resistor R ₉ is on the power supply terminal 12 side between the power supply terminal 12 and the current supply terminal a of the Hall element 16. Connected to. That is, a current setting resistor R ₉ is provided between the power supply terminal 12 and the emitter of the PNP bipolar transistor Q, and the collector of the PNP bipolar transistor Q is connected to the current supply terminal a of the Hall element 16. Operational amplifier 32, the divided voltage V _dv from the voltage dividing circuit 24 is input to the non-inverting input terminal, an inverting input terminal connected to a junction of a PNP bipolar transistor Q and the current setting resistor R _9, output The terminal is connected to the control terminal (base terminal) of the PNP bipolar transistor Q.

  In FIG. 6B, an N channel MOS type field effect transistor (MOS: Metal-Oxide Semiconductor) is used, which is a modification of the constant current circuit 18 of FIG. In FIG. 6C, a P-channel MOS field effect transistor is used, which is a modification of the constant current circuit 18 of FIG. The drive circuit of the Hall element 16 is not limited to a constant current circuit, and the current supply terminals a and c of the Hall element 16 are connected to the power supply terminal 12 and the ground terminal 14 through resistors (fixed resistors) as necessary. Thus, constant voltage driving may be used.

  In the embodiment, the case where the Hall element 16 is disposed in the gap portion G of the magnetic core 20 has been described. However, in a modification, a coreless configuration illustrated in FIG. 9 may be adopted.

In the embodiment, the case where the magnetic proportional current sensor is driven by a single power supply has been described. In this case, since the ground potential can be used as the intermediate voltage V _md , the intermediate voltage generation circuit 26 is not necessary.

In the embodiment, the resistor _RT is a resistor that can be trimmed (for example, a laser trimming resistor), but in a modified example, the resistor _RT may be a variable resistor.

1 is a circuit diagram of a magnetic proportional current sensor according to an embodiment of the present invention. (A) is typical explanatory drawing of the magnetic field (magnetic flux density in a gap) applied to the Hall element of the magnetic proportional type current sensor. (B) is an exemplary characteristic diagram of the magnetic flux density in the gap with respect to the current to be measured. The characteristic view which illustrates the relationship between the drive current and output voltage of the Hall element. The characteristic view which illustrates the relationship between the drive current of the Hall element, and an offset voltage. The characteristic view with respect to the ambient temperature of the output voltage of the Hall element. The circuit diagram which shows the modification of a constant current circuit. The basic block diagram of a magnetic proportional type current sensor. A basic circuit diagram of a magnetic proportional current sensor. The structure of the magnetic proportional type current sensor of the coreless structure which does not use a ring-shaped magnetic core is shown, (A) is a top view, (B) is sectional drawing. FIG. 10 is a characteristic diagram illustrating the relationship between the current to be measured and the magnetic field (magnetic flux density) applied to the magnetic sensitive surface of the Hall element in the case of FIG. 9.

Explanation of symbols

12 power supply terminal 14 ground terminal 15 sensor output terminal 16 hall element 18 constant current circuit 22 differential amplifier 24 voltage dividing circuit 26 intermediate voltage generating circuit 100 magnetic proportional current sensor

Claims (3)

A magnetic sensing element to which a magnetic field generated by a current to be measured is applied;
A drive circuit for driving the magnetic detection element at a constant voltage or a constant current;
A differential amplifier that amplifies the output voltage of the magnetic detection element;
The differential amplifier includes an operational amplifier, first to sixth resistors, and a trimmable resistor or a variable resistor.
The first resistor is provided in a path connecting one output terminal of the magnetic detection element and the inverting input terminal of the operational amplifier, and connects the other output terminal of the magnetic detection element and the non-inverting input terminal of the operational amplifier. The second resistor is provided in a path to be connected, the third and fourth resistors are connected in series to a path connecting the output terminal of the operational amplifier and the inverting input terminal, and the non-inverting input terminal and the reference voltage terminal are connected to each other. The fifth and sixth resistors are connected in series to the path connecting the three, and the trimmable resistance is connected to the path connecting the connection point of the third and fourth resistors and the connection point of the fifth and sixth resistors. Alternatively, a magnetic proportional current sensor provided with the variable resistor, wherein the first and second resistors have the same resistance value, and the third to sixth resistors have the same resistance value.   2. The magnetic proportional current sensor according to claim 1, wherein the first to sixth resistors are fixed resistors. The magnetic proportional current sensor according to claim 1 or 2,
A ring-shaped magnetic core having a gap portion surrounding the path of the current to be measured;
A magnetic proportional current sensor, wherein the magnetic detection element is located in the gap portion.

Images