JPH0824201B2 - Magnetic semiconductor element temperature compensation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a temperature compensation circuit for a magnetic semiconductor element.

(Prior Art) Conventionally, for example, a Hall element is often used as a sensor that converts a magnetic field into an electric signal and detects the electric signal.

The Hall element uses a so-called Hall effect, in which a current is input into a rod-shaped or plate-shaped conductor or a semiconductor and a magnetic field is applied in a direction perpendicular to the current to generate a potential difference in the direction perpendicular to the current and the magnetic field.

Here, when the voltage due to the potential difference caused by the Hall effect is the output voltage (Hall voltage E), the current is the drive current, and the magnetic field is the measured magnetic field, the output voltage E is expressed by the following equation.

E = sensitivity coefficient × driving current × magnetic field to be measured However, in the above equation, the sensitivity coefficient means a so-called Hall coefficient, which is a proportional constant specific to the material of the Hall element, which is a proportional constant.

Therefore, if the Hohl element is used, the magnetic field to be measured can be easily detected by measuring the output voltage when a constant drive current is input.

(Problems to be Solved by the Invention) However, the sensitivity coefficient has temperature dependency, and normally, the sensitivity coefficient decreases as the operating environment temperature rises.
As a result, even with the same magnetic field, the output voltage E was different when the temperature was different, and the magnetic measurement could not be performed accurately. This also applies to other magnetic semiconductor elements.

Therefore, it is conceivable to adjust the circuit according to the temperature change, but there are problems that the adjustment work must be performed every time the temperature changes, and that the circuit becomes complicated and the number of parts increases.

An object of the present invention is to provide a temperature compensating circuit for a magnetic semiconductor element capable of always performing accurate magnetic measurement by automatically compensating the temperature even if the environmental temperature changes with a simple circuit configuration in order to solve the above problems. To provide.

Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention provides a magnetic semiconductor element whose output voltage is determined by three factors of a sensitivity coefficient, a drive current, and a magnetic field to be measured, to prevent a change in temperature. A temperature compensating circuit for a magnetic semiconductor element, comprising a temperature compensating circuit for compensating a change in output voltage due to a temperature change by varying a drive current according to a change in a sensitivity coefficient accompanying the change, and a drive circuit is connected to the magnetic semiconductor element. However, the drive circuit itself is configured to flow a constant drive current to the magnetic semiconductor element regardless of temperature changes, and the drive circuit is configured so that a current flows in the forward direction of the diode, the resistor, and the diode thereof. The drive unit is configured only with a power supply that supplies a predetermined voltage, and the drive current is increased based on a decrease in the forward voltage of the diode due to a temperature rise. Acts on the road, which are connected to the temperature compensation circuit which acts on the drive circuit so that the drive current is reduced based on the increase in the forward voltage of the diode due to temperature drop.

(Operation) By the above means, when the temperature rises and the sensitivity coefficient of the magnetic semiconductor element decreases, the forward voltage of the diode provided in the temperature compensating circuit also decreases and the drive current increases. On the other hand, when the temperature decreases and the sensitivity coefficient of the magnetic semiconductor element increases, the forward voltage of the diode provided in the temperature compensating circuit also increases and the driving current is varied so as to decrease. As a result, the product of the sensitivity coefficient and the drive current is kept constant, and an output voltage corresponding to the magnetic field to be measured can be obtained from the magnetic semiconductor element regardless of the temperature.

Here, in the present invention, since the drive circuit is connected to the magnetic semiconductor element, the setting of the change amount of the drive current due to the temperature change of the temperature compensation circuit including the diode eliminates the influence of the change of the drive current due to the temperature change. Therefore, it is possible to perform it based only on the relationship between the sensitivity coefficient of the magnetic semiconductor element and the temperature, and the setting work of the temperature compensation circuit for keeping the product of the sensitivity coefficient and the drive current constant regardless of the temperature change. It can be done very easily. Moreover, the temperature compensating circuit has an extremely simple circuit configuration including only the diode and the resistor, and is therefore advantageous in terms of cost.

(Embodiment) An embodiment in which the temperature compensating circuit for a magnetic semiconductor element of the present invention is embodied in a magnetic detecting device using a Hall element will be described below with reference to the drawings.

FIG. 1 shows an electric circuit of a magnetic detector using a hall element, which is composed of a hall element drive circuit C1 as a drive circuit and a compensation circuit C2. Then, in the drive circuit C1, the variable resistor 1 divides the operating voltage Vcc and divides the divided voltage V1.
Is output to the + input terminal of the operational amplifier 2. The output terminal and the-input terminal of the operational amplifier 2 are connected between the input electrodes of the Hall element 3 as a magnetic semiconductor element, and are closed loop, that is, feedback is performed and the voltage V1 and-that are always input to the + terminal are
The voltage V2 input to the input terminal is always the same.

The Hall element 3 has a driving current Id flowing between the output terminal of the operational amplifier 2 and the input electrode of the element 3, a sensitivity coefficient that varies depending on the temperature of the element 3 and an output electrode that is determined by the strength of the magnetic field to be measured. The hall voltage E is output. The sensitivity coefficient depends on the semiconductor material of the Hall element, and its value decreases as the temperature rises.

On the other hand, the ground side input electrode of the hall element 3 is connected to the resistor 5 of the compensation circuit C2 via the resistor 4. Compensation circuit C2
Is composed of resistors 6 and 7 and a diode 8 in addition to the resistor 5, and the resistor 6 connects the connection point a of the resistors 4 and 5 and the resistor 7
And the connection point b of the diode 8 are connected. In this embodiment, the resistance value R of the resistor 4 is set to be larger than that of the resistor 5. Therefore, assuming that the voltage at the connection point a is Va, the driving current Id is Id = (V2-Va) because the input impedance of the-input terminal of the operational amplifier 2 is high.
/ R.

The resistance values of the resistors 6 and 7 are set so that the current flowing through the diode 8 is several milliamperes. The Vf-If temperature characteristic of the diode 8 is the diode shown in FIG. 2, and all ordinary diodes have this characteristic. Therefore, when the temperature rises, the forward voltage Vf, that is, the voltage Vb at the connection point b decreases. As a result, the voltage Va at the connection point a decreases in proportion to this.

Next, the operation of the magnetic detection device configured as described above will be described.

Now, when the Hall element 3 is detecting a magnetic field having a constant strength, the voltage E of the Hall element 3 has a value determined by the product of the sensitivity coefficient, the drive current Id, and the strength of the magnetic field.

When the environmental temperature rises and the sensitivity coefficient decreases accordingly, the forward voltage of the diode 8, that is, the voltage Vb decreases and the voltage Va also decreases at the same time. On the other hand, since the voltage V2 at the ground-side input terminal of the hall element 3 is always held constant (= V1) by the operational amplifier 2, (V2-Va)
The drive current Id determined by / R increases as the voltage Va decreases.

Therefore, if the ambient temperature rises and the sensitivity coefficient decreases,
The drive current Id increases accordingly. As a result, the sensitivity coefficient,
The Hall voltage E determined by the product of the drive current Id and the strength of the magnetic field always shows a constant value as long as the strength of the magnetic field does not change even if the temperature rises.

On the contrary, when the environmental temperature decreases, the sensitivity coefficient increases and the driving current Id decreases by the change.

As described above, in the present embodiment, even if the sensitivity coefficient of the Hall element 3 changes due to the change of the ambient temperature, the compensation circuit automatically controls the magnitude of the drive current Id accordingly.
It is easy to perform accurate magnetic measurements without being affected by changes in environmental temperature. Further, the compensating circuit C2 has a very simple circuit configuration including the resistors 5 to 7 and the diode 8, which is very advantageous in terms of cost. Further, since the drive circuit C1 is connected to the Hall element 3, the influence of the change of the drive current Id due to the temperature change can be eliminated, so that the change of the drive current Id due to the temperature change of the temperature compensation circuit C2 including the diode 8 can be eliminated. The amount can be set based only on the relationship between the sensitivity coefficient of the Hall element 3 and the temperature, and the temperature compensating circuit C2 for keeping the product of the sensitivity coefficient and the drive current constant regardless of the temperature change. The setting work can be performed extremely easily.

The present invention is not limited to the above embodiment, but may be applied to other magnetic semiconductor elements such as a magnetoresistive element other than the Hall element.

Effects of the Invention As described in detail above, according to the present invention, the temperature dependence of the forward voltage originally possessed by a diode is utilized, and even if the ambient temperature changes with an extremely simple circuit configuration including the diode and the resistor. The temperature can be automatically compensated for accurate magnetic measurement, and the temperature compensating circuit can be set very easily.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a magnetic detection device embodying the present invention, and FIG. 2 is a Vf-If temperature characteristic diagram of a diode. In the figure, 1 is a variable resistor, 2 is an operational amplifier, 3 is a hall element, 4 to 7 are resistors, 8 is a diode, C1 is a hall element drive circuit as a drive circuit, and C2 is a compensation circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Sasaki 2-11-17 Osaki, Shinagawa-ku, Tokyo Stock company Inside the company Meidensha (72) Mineo Ozeki 2-1-117 Osaki, Shinagawa-ku Tokyo Stockholder Shameidensha (56) Reference JP-A-52-58386 (JP, A) JP-A-50-11189 (JP, A) Actual public 53-54220 (JP, Y2) Actual public 52-45179 (JP, A) Y2)

Claims (3)

[Claims] 1. A magnetic semiconductor device, the output voltage of which is determined by three factors: sensitivity coefficient, drive current, and magnetic field to be measured, the drive current is varied according to the change of the sensitivity coefficient with temperature change, and the output with temperature change is output. In the temperature compensation circuit of the magnetic semiconductor element provided with the temperature compensation circuit for compensating for the change in voltage,
A drive circuit is connected to the magnetic semiconductor element, and the drive circuit itself is configured to flow a constant drive current to the magnetic semiconductor element regardless of temperature changes. It is composed only of a power supply that supplies a predetermined voltage so that a current flows in the forward direction of the diode, and acts on the drive circuit so that the drive current increases based on a decrease in the forward voltage of the diode due to a temperature rise. A temperature compensating circuit for a magnetic semiconductor element, which is connected to a temperature compensating circuit that acts on the drive circuit so that the drive current becomes smaller based on an increase in the forward voltage of the diode accompanying a temperature decrease. 2. The temperature compensating circuit for a magnetic semiconductor device according to claim 1, wherein the magnetic semiconductor device is a Hall device, and the output voltage is a Hall voltage. 3. A temperature compensating circuit for a magnetic semiconductor element according to claim 1, wherein the magnetic semiconductor element is a magnetoresistive element.