JP2001141757A - Sensor device using hall element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Hall amplifier type current sensor device dispensing with the change of a thermistor used for temperature correction of the characteristic of a Hall element even in the change of the Hall element to be used. SOLUTION: This device comprises a Hall element voltage and current supplying part 25 for supplying control voltage and current to the Hall element 21, a differential amplifier part 26 for differentially amplifying the output signals at both ends of the Hall element 21, and a V-I converting circuit part 27 for correcting the current I obtained by impedance-converting the output Vo from the differential amplifier part 26 with a thermistor TH. In this device, the output voltage Vo is not corrected, but the current I corresponding to the output voltage Vo is corrected in a V-I converting circuit part 27 in the latter stage according to temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor device using a Hall element, and more particularly, to a sensor device using a Hall element for correcting a variation error of a Hall element or the like due to a temperature change with one thermistor.

[0002]

2. Description of the Related Art In a current sensor of a hall amplifier type using a Hall element, a temperature characteristic of the Hall element becomes a problem.

For example, GaAs without a temperature compensation circuit
As shown in FIG. 5, the input-output characteristics of a Hall-amplifier type current sensor using a Hall element show that the output increases as the input current increases when the temperature is low, and the input current increases when the temperature is high. As the output decreases, the output decreases. That is, an error occurs in the output due to the temperature change.

For this reason, a temperature compensation circuit is generally used for a current sensor of the Hall amplifier type. An example of a Hall amplifier type current sensor using a temperature compensation circuit will be described below.

FIG. 6 is a temperature compensation circuit diagram of a current sensor disclosed in Japanese Patent Application Laid-Open No. 6-74975. This temperature compensation circuit 1
A sensitivity adjustment circuit 3 which receives a detection signal detected by the Hall element 2 and adjusts a voltage gradient of the detection signal to a proper gradient at a predetermined temperature detected by the thermistor 3a;
An offset adjuster 4 for correcting the characteristics of the Hall element 2 and two resistors 6a and 6b having the same resistance values 6a and 6b and having different temperature coefficients are connected in series between a power supply and a ground. , The temperature gradient setting unit 4 connected to the connection point of the two resistors 6a and 6b and one of the operational amplifiers 5 to change the temperature coefficient of the Hall element and the offset change caused by the ambient temperature change. Has been adjusted.

FIG. 7 shows a Japanese Patent Application Laid-Open No. 63-61961.
In the current detector disclosed in Japanese Patent Application Laid-Open No. H10-209, a control current is supplied in advance to the Hall element 11 by the drive circuit 10, and when a detected current flows through the electric wire, a magnetic field corresponding to the detected current is generated in the core.
An output signal proportional to this magnetic field is input to the differential amplifier 12 via the resistors R1 and R3.

This differential amplifier 12 uses a temperature compensating circuit 13 in which a thermistor TH and a resistor R5 are connected in parallel as a feedback resistor section, thereby adjusting a change in sensitivity due to temperature.

In such a Hall-amplifier type current sensor device, for example, as shown in FIG. 8, the Hall element (1), the Hall element (2), and the Hall element (3) vary depending on the variation of the Hall element and the circuit system. When the output current-input current characteristics are illustrated, it can be seen that there are variations.

As shown in FIG. 9, the Hall voltage VH
Is proportional to the magnetic flux density B of the Hall element.

Taking the Hall amplifier type sensor of FIG. 6 as an example, the output voltage Vo is expressed by the following equation (1).

[0011]

(Equation 1) That is, as shown in Equation 1, in order to make the output voltage Vo have a slope that follows the temperature change even if the temperature changes, the characteristics of the Hall element using the resistors R2, R4, R5 and the thermistor TH are changed. Had been changed accordingly.

[0012]

However, the above-mentioned conventional Japanese Patent Application Laid-Open No. 6-74975 and Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 3-61961 has a problem that it takes time and cost because the characteristics of the Hall element to be used must be examined and a thermistor according to the characteristics must be selected.

In Japanese Patent Application Laid-Open No. H6-74975, the offset adjustment section and the sensitivity adjustment section must be provided with thermistors, respectively, so that the work is doubled.

Further, the Hall element may be changed for some reason. In such a case, the characteristics of the Hall element must be checked again and a thermistor that matches the characteristics of the Hall element must be selected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is not necessary to change the thermistor used for temperature-correcting the characteristics of the above-mentioned Hall element even if the Hall element to be used is changed. An object of the present invention is to obtain an amplifier type current sensor device.

[0016]

SUMMARY OF THE INVENTION The present invention provides a differential amplifying section which obtains an output voltage obtained by differentially amplifying both ends of a Hall element without using a temperature-sensitive resistor, and a stage after the differential amplifying section. The present invention further comprises a voltage-current conversion circuit for converting an output voltage from the differential amplifier into a current and correcting the current with a temperature-sensitive resistor.

The voltage-current conversion circuit section includes a transistor, a thermistor connected in series to the emitter of the transistor via a resistor, and an output voltage from the differential amplifier section input to a positive input terminal, and a negative input terminal. The gist of the invention consists of an amplifier whose end is connected to the emitter of the transistor.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of a hall amplifier type current sensor device according to the present embodiment. FIG. 2 is a configuration diagram in which the Hall amplifier type current sensor device 20 of the present embodiment is connected to a non-contact sensor 23 including a Hall element 21 and a magnetic core 22.

This Hall amp type current sensor device 20
Is a Hall element voltage / current supply unit 25 that supplies a control voltage and a current to the Hall element 21 as shown in FIGS.
A differential amplifying unit 26 for differentially amplifying an output signal at both ends of the Hall element 21; and a VI conversion circuit unit for correcting a current I obtained by impedance-converting the output Vo from the differential amplifying unit 26 with a thermistor TH. 27. That is,
The current I corresponding to the output voltage Vo is corrected according to the temperature change without correcting the output voltage Vo.

(Structure of Each Unit) The Hall element voltage / current supply unit 25 includes a reference voltage generating circuit 30 including an electric field capacitor C1, a resistor R1, a transistor TR1, a Zener diode D1, a capacitor C2, and the like. The reference voltage generation circuit 30 is configured to connect an input power supply to an
, And a Hall element control voltage which is set to a predetermined voltage by the Zener diode D1, the resistor R1, and the transistor TR1 is applied to the Hall element 21.

The Hall element voltage / current supply unit 25
A constant current circuit 31 is provided. This constant current circuit 31
It comprises resistors R2, R3, an amplifier AMP1, a resistor R4, a transistor TR2, a resistor R5, and the like.

The resistors R2 and R3 are connected in series, and this voltage dividing point is input to the plus input terminal of the amplifier AMP1.
The output of the amplifier AMP1 is connected to the base of the transistor TR2 via the resistor R4. This transistor T
R2 has a collector connected to the Hall element 21 and an emitter connected to the ground via a resistor R5.

The differential amplifier 26 includes a resistor R6, a resistor R7,
It is composed of a resistor R8, a resistor R9, a resistor R10, a resistor R11, and an amplifier AMP2. Resistance R8 and resistance R9
Are connected in series, and this voltage dividing point becomes a reference power supply of the amplifier AMP2 and is input via the resistor R10.

The differential amplifier 26 receives the Hall element voltage VH from the Hall element 21 via the resistors R6 and R7, and obtains an output voltage Vo obtained by amplifying the difference signal based on the feedback resistor R11.

The VI conversion circuit 27 includes a differential amplifier 26
Output voltage Vo from the amplifier AMP via the resistor R12.
3 is input to the plus input terminal. And this amp AM
P3 has its output connected to the base of transistor TR3 via resistor R13.

The emitter of the transistor TR3 is connected to a series-parallel circuit including resistors R14, R15 and thermistors TH, R16.

(Explanation of Operation) In the Hall-amplifier type current sensor device 20 configured as described above, when the non-contact sensor 23 receives a current from the battery through the power supply line, a magnetic flux corresponding to the amount of the current flows into the core 22. The Hall element 21 provided in the gap between the cores 22 sends out a Hall element voltage VH proportional to the magnetic flux generated in the core 22 to the differential amplifier 26.

The differential amplifying section 26 receives the Hall element voltage V
H is differentially amplified by a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, and an amplifier AMP2, and transmitted to the VI conversion circuit unit 27 via a resistor R12.

That is, the output voltage Vo in the differential amplifier 26 is obtained as shown in the following equation (2).

[0030]

(Equation 2) As shown in Expression 2, the output voltage Vo is equal to the resistance R11,
Since it is indicated only by R6 and the Hall element voltage VH, even if there is a variation in the Hall element, it can be corrected by adjusting the resistance r10 and the resistance R11.

However, since the temperature is not corrected by providing a thermistor, the characteristics of the output voltage Vo and the output current Io vary depending on the temperature, as shown in FIG.

However, the output voltage Vo of the differential amplifying section 26 is equal to the voltage of the VI conversion circuit section 2 having the thermistor TH.
7 and is subjected to impedance conversion. That is, the current I corresponding to the output voltage Vo flows through the transistor TR3.

This transistor TR3 has a resistor R1
4. Thermistor TH is connected via R15.

That is, even if the temperature changes, the resistance of the thermistor TH changes according to the temperature change.
As shown in FIG. 3B, an output having no variation in output characteristics is obtained. FIG. 3B is based on 20 ° C.

That is, in the subsequent stage of the differential amplifier 26,
When the temperature is low, the current I corresponding to the Hall voltage VH is decreased, and when the temperature is high, the current I is increased.

Therefore, offset adjustment, gain adjustment, etc. are performed in the first stage and only temperature correction is performed in the second stage. Therefore, even if the Hall element is changed, the offset adjustment and gain adjustment in the previous stage are performed by the resistors R10, R11, R6. I just need to go
The thermistor TH can be used as it is.

Although the above embodiment has been described as a current detection type Hall-amplifier type current sensor device, a voltage detection type Hall-amplifier type voltage sensor device may be used as shown in FIG.

In FIG. 4, a series circuit composed of resistors Ra and Rb is connected in parallel to the battery, and the voltage at this voltage dividing point is input to a VI conversion circuit 40 constituted by a voltage follower. The output is wound around the core 22, and the output of the Hall element 21 is input via a differential amplifying section 26 to a VI conversion circuit section 27 having a thermistor.

[0039]

As described above, according to the present invention, after differentially amplifying the output from both ends of the Hall element, the voltage-current conversion circuit section including the temperature-sensitive resistor converts the differentially amplified voltage. The current is converted into a current, and the current is changed according to the temperature.

Therefore, even if the Hall element to be used changes, only the resistance value needs to be changed, so that it is not necessary to change the thermistor used for temperature correction of the characteristics of the Hall element. ing.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a Hall amplifier type current sensor device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram in which a Hall-amplifier-type current sensor device 20 of the present embodiment is connected to a non-contact sensor 23 including a Hall element 21 and a magnetic core 22.

FIG. 3 is an explanatory diagram illustrating an operation effect obtained by using the IV conversion circuit unit of the present embodiment.

FIG. 4 is a schematic configuration diagram of another embodiment.

FIG. 5 is an output characteristic of a hall amplifier type current sensor device having no temperature compensation circuit.

FIG. 6 is a schematic configuration diagram of a conventional hall amplifier sensor device.

FIG. 7 is a schematic configuration diagram of a conventional hall amplifier sensor device.

FIG. 8 is an explanatory diagram illustrating a variation due to a control current of a Hall element.

FIG. 9 is an explanatory diagram illustrating a relationship between a Hall voltage and a magnetic flux density.

[Explanation of symbols]

 Reference Signs List 20 Hall amp type current sensor device 21 Hall element 22 Magnetic core 23 Non-contact sensor 25 Hall element voltage / current supply part 26 Differential amplification part 27 VI conversion circuit part TH thermistor

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 2G017 AA07 AB05 AC04 AC07 AD53 BA05 BA10 2G025 AA08 AA17 AB02 2G035 AA03 AA28 AB01 AC01 AD01 AD02 AD05 AD10 AD11 AD13 AD20 AD54 AD56 AD66

Claims (2)

[Claims] A differential amplifier for obtaining an output voltage obtained by differentially amplifying an output from both ends of a Hall element without using a temperature-sensitive resistor; and a differential amplifier provided at a stage subsequent to the differential amplifier. A sensor device using a Hall element comprising: a voltage-current conversion circuit for converting an output voltage from a current into a current and correcting the current by a temperature-sensitive resistor. 2. The voltage-current conversion circuit section includes: a transistor; a thermistor connected in series via a resistor to an emitter of the transistor; and an output voltage from the differential amplifier section input to a positive input terminal; 2. The sensor device according to claim 1, further comprising an amplifier having a negative input terminal connected to an emitter of the transistor.