JP3428205B2 - Hall element drive circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in a sensor for detecting the throttle opening of a vehicle-mounted internal combustion engine in a non-contact manner based on the Hall effect, while suitably compensating the temperature characteristics of a Hall element and a magnet. The present invention relates to a hall element drive circuit that supplies a drive signal to the hall element.

[0002]

2. Description of the Related Art For example, as a throttle opening sensor for a vehicle-mounted internal combustion engine, a sensor is known which detects the throttle opening in a non-contact manner based on the Hall effect. FIG. 4 shows an outline of an example of a throttle opening sensor using the Hall effect.

That is, the throttle opening sensor has a concentric cylindrical shape magnetized in a direction orthogonal to the rotational axis of a rotor 11 that rotates in conjunction with the rotational axis of a throttle valve (not shown). A permanent magnet 12 is provided, and a hall element 10 for detecting a magnetic field direction of the permanent magnet 12 is provided in a hollow portion of the permanent magnet 12 in parallel with a plane along the rotation axis of the rotor 11 and symmetrically about the rotation axis. Is provided.

As the throttle valve rotates, the permanent magnet 12 rotates around the Hall element 10 in the manner shown in FIG. 4, whereby the direction of the magnetic field with respect to the magnetically sensitive surface of the Hall element 10 changes. The electrical signal corresponding to the angle θ, that is, the Hall voltage VH is output from the Hall element 10 in the form of VH = KH · B · Rd · I · sin θ = VA · sin θ (1).

Here, the value VA is the value “KH · B · Rd ·
5 is a constant corresponding to “I”, and as shown in FIG. 5, the rotor 11 moves from “−90 (= θ)” to “+90 (=
θ) ”degrees, the Hall voltage VH is
It continuously changes on the sine wave from "-VA" to "+ VA". In the equation (1), KH is the Hall element 1
0 is the sensitivity, B is the magnetic flux density of the magnet 12, and Rd
Is the internal resistance of the Hall element 10 and I is the Hall element 1
The drive current is zero.

In the throttle opening sensor, the Hall voltage VH output from the Hall element 10 in this manner is processed as necessary, and an electric signal corresponding to the opening of the throttle valve is output.

On the other hand, as a drive circuit for a Hall element used in this type of sensor, a conventional circuit is disclosed in, for example, Japanese Unexamined Patent Publication No. 5-157.
The circuit described in Japanese Patent No. 506 is known. The drive circuit basically has the configuration shown in FIG.

That is, in the drive circuit, the resistor R21 and the temperature-sensitive resistor (thermistor) R22 having a positive temperature characteristic constitute a first voltage dividing circuit, and the resistor R23 and the resistor R24 form a second voltage dividing circuit. Make up. Then, the divided voltages are further divided by the resistors R25 and R26 to generate the reference voltage Vd for driving. The terminal T
1 is a power supply voltage (Vcc) application terminal, which is a terminal T2
Is a ground (GND) terminal.

In the driving circuit, the operational amplifier A and the resistor R27 are circuits for driving the Hall element 10 with a constant current. In this circuit, based on the above-mentioned reference voltage Vd, between the terminals a and b of the Hall element 10, (Vd / R27
The driving current I such as the resistance value of (1) is supplied to drive this.

By driving the hall element 10 in this way, for example, in the above-mentioned throttle opening sensor, when the permanent magnet 12 rotates around the hall element 10 by the angle θ with the rotation of the throttle valve, That angle θ
The Hall voltage VH corresponding to (1) is output from between the terminals cd of the Hall element 10 in the mode represented by the above formula (1).

The signal processing circuit 20 is a circuit that processes the Hall voltage VH thus output as necessary and outputs an electric signal Vo corresponding to the opening of the throttle valve from its output terminal T3.

By the way, the Hall element 10 and the magnet 1
Since No. 2 has a negative temperature characteristic, its driving condition normally changes depending on the ambient temperature, and the output Hall voltage VH also varies according to those temperature characteristics. When such a variation occurs in the Hall voltage VH, the reliability of the processed signal Vo becomes naturally low.

Therefore, in the drive circuit illustrated in FIG. 6, the thermistor R22 having a positive temperature characteristic opposite to those of the Hall element 10 and the magnet 12 is arranged in the first voltage dividing circuit, The temperature characteristics of the Hall element 10 and the magnet 12 are compensated by making the reference voltage Vd, and thus the driving current I, have a positive temperature characteristic through the temperature sensitive resistance characteristic of the thermistor R22.

[0014]

As described above, if the temperature characteristics of the Hall element and the magnet are compensated through the reference voltage or the driving current for driving the Hall element and the magnet, the reliability of the Hall voltage VH output is also improved. It will naturally increase.
If the reliability of the hall voltage VH is improved in this way,
Even when this is applied to the sensor as described above, the sensor output (output voltage Vo) can always be maintained with high accuracy.

However, the thermistor used for compensating the temperature characteristic in the conventional Hall element driving circuit has a large variation in the temperature characteristic itself, and there is a disadvantage that the temperature compensation accuracy cannot be so high.

Further, since this thermistor cannot be formed in a semiconductor chip like other circuit elements such as transistors, diodes, resistors, etc., it is difficult to reduce the size of the drive circuit and the number of parts. It is also becoming.

Not only the above-mentioned throttle opening sensor but also a device for obtaining an electric signal corresponding to the strength of the magnetic field by utilizing the Hall effect by the Hall element, the above-mentioned circuit for driving the Hall element is used. The facts are generally the same.

The present invention has been made in view of the above circumstances, and it is possible to maintain a high temperature compensation accuracy in any usage environment, and to reduce the number of parts by facilitating the formation of a semiconductor chip. In addition, it is an object of the present invention to provide a Hall element drive circuit that can favorably reduce the size.

[0019]

In order to achieve such an object, in the invention according to claim 1, in the hall element drive circuit, a feedback amplifier circuit for feedback amplifying a reference voltage,
A feedback current control circuit that includes a voltage drop element whose drop voltage changes according to temperature and is connected to the feedback path of the feedback amplification circuit to control the current flowing through the feedback path, and the feedback that also includes a voltage drop element. An output voltage control circuit arranged in the feedback path of the amplifier circuit for controlling the output voltage of the feedback amplifier circuit, wherein the output voltage is controlled by the feedback current control circuit and the output voltage control circuit. A drive signal is supplied to the Hall element based on the output.

According to a second aspect of the present invention, in the configuration of the first aspect of the invention, the feedback current control circuit includes a series circuit of a first diode and a first resistor, The output voltage control circuit is configured to include a series circuit of a second diode and a second resistance, and a resistance value of the first resistance of the first resistance and the second resistance> second resistance The output of the feedback amplifier circuit is set to a positive temperature characteristic based on the relationship of the resistance value of.

According to a third aspect of the invention, in the configuration of the second aspect of the invention, the feedback current control circuit is controlled so that the current flowing through the feedback path of the feedback amplification circuit is controlled to 10 μm to 1 mAmps. The resistance value of the first resistor is set.

According to a fourth aspect of the present invention, in the configuration of the first to third aspects of the invention, a resistor connected in series with the Hall element, a voltage drop across the resistor, and an output of the feedback amplifier circuit. And an operational amplifier that controls the voltage applied to the Hall element so that the voltage drop of the same resistance becomes constant, and a constant current control circuit that supplies the drive signal to the Hall element. And

[0023]

[Function] The Hall element or a magnet disposed around the Hall element as a magnetic field generation source for the Hall element has a negative temperature characteristic, and the temperature characteristic of the Hall element or the magnet is compensated through the driving current of the Hall element. If so, the reliability of the output Hall voltage will naturally increase, and the like, as described above.

Further, although the temperature characteristics of the Hall element and the magnet are compensated to some extent by generating the drive current and the like by using a thermistor having a positive temperature characteristic, the temperature characteristics of the thermistor itself are different. It has been described above that the driving force is large and is a factor that hinders the miniaturization of the drive circuit.

Therefore, in the invention according to the above-mentioned claim 1, (a) a feedback amplifier circuit for feedback-amplifying the reference voltage. (B) A feedback current control circuit that includes a voltage drop element whose drop voltage changes according to temperature and is connected to the feedback path of the feedback amplifier circuit to control the current flowing through the feedback path. (C) An output voltage control circuit that includes a voltage drop element and is arranged in the feedback path of the feedback amplification circuit to control the output voltage of the feedback amplification circuit. A hall element drive circuit is configured to include the above, and a drive signal is supplied to the hall element based on the output of the feedback amplifier circuit whose output voltage is controlled by the feedback current control circuit and the output voltage control circuit.

Here, there are various diodes and transistors as the voltage drop elements constituting the feedback current control circuit and the output voltage control circuit, but all of them have a negative temperature characteristic like the Hall element and the magnet. To have.

Therefore, in the feedback amplifier circuit in which the output voltage control circuit is arranged in the feedback path, the reference voltage as its output is stabilized at a required level through the voltage control by the output voltage control circuit. Although the converted signal is generated, the generated signal usually has a negative temperature characteristic.

However, if the feedback current control circuit is further connected to the feedback path of the feedback amplifier circuit as in the above-described structure of the invention according to claim 1, the feedback current control circuit and the output voltage control circuit are provided. It becomes possible to change the temperature characteristics of the signal generated as the output of the feedback amplifier circuit, including the positive and negative polarities, by the amount of current and voltage control by the.

Therefore, at the output of the feedback amplifier circuit, the current by the feedback current control circuit and the output voltage control circuit,
By providing a positive temperature characteristic according to the voltage control amount, the drive signal under constant current control also naturally has a positive temperature characteristic, and the temperature characteristics of the Hall element and magnet are well compensated. Will be done.

Further, according to the above configuration of the invention as defined in claim 1, the degree of temperature compensation is arbitrarily determined according to the current and voltage control amount by the feedback current control circuit and the output voltage control circuit. Therefore, even if there are variations in the temperature characteristics of the Hall element and the magnet, it becomes possible to easily deal with those variations.

On the other hand, not only the feedback amplifier circuit but also the diodes and transistors forming the feedback current control circuit and the output voltage control circuit are integrated into a semiconductor chip as, for example, one monolithic IC including these circuits. It is possible and easy.

Therefore, according to the first aspect of the present invention, it is possible to favorably promote the miniaturization of the Hall element drive circuit while maintaining the high temperature compensation performance while reducing the number of parts. Also becomes.

According to the invention of claim 2,
The feedback current control circuit is configured to have a series circuit of a first diode and a first resistance, and the output voltage control circuit is configured to have a series circuit of a second diode and a second resistance. Based on the relationship of the resistance value of the first resistor between the first resistor and the second resistor> the resistance value of the second resistor, the output of the feedback amplifier circuit is set to a positive temperature. It can be set to a characteristic.

That is, since the voltage drop of the first diode in the feedback current control circuit and the voltage drop of the second diode in the output voltage control circuit have opposite polarities, the first resistor and the second resistor are connected. Due to the above relationship with the resistance, the polarity of the temperature characteristic of the output of the feedback amplifier circuit whose feedback current is controlled based on the voltage drop of those diodes having the negative temperature characteristic is inverted.

Further, according to the above-mentioned structure according to the second aspect of the present invention, the temperature characteristics of the Hall element and the magnet are highly accurately compensated with the extremely simple circuit structure as the feedback current control circuit and the output voltage control circuit. You will be able to. Incidentally, in this case, as long as the above-mentioned relation between the first resistance and the second resistance is satisfied, the variation in the temperature characteristics of the Hall element and the magnet is absorbed according to the ratio of the resistance values.

According to the invention of claim 3,
In the feedback current control circuit, the resistance value of the first resistor is set so that the current flowing through the feedback path of the feedback amplification circuit is controlled to 10 μm to 1 mAmps. With such a configuration, the influence of the offset current of the feedback amplification circuit, which normally flows in the order of several tens (nano) to several hundreds of n amps, can be neglected, and the output capacitance of the feedback amplification circuit is practically used as an IC. It will be possible to set the desired capacity.

That is, the current of 10 μAmps is
The current is sufficient to prevent the temperature compensation accuracy from deteriorating due to variations in the offset current of the feedback amplifier circuit. In addition, the current of 1 mampere is the first and second
It is an appropriate current that does not require a large-capacity element in the diode or the output portion of the feedback amplifier circuit, that is, without unnecessarily increasing the size of the IC chip.

According to the invention of claim 4, (d1) a resistor connected in series to the hall element. (D2) An operational amplifier that compares the voltage drop of the resistor and the output of the feedback amplifier circuit and controls the voltage applied to the Hall element so that the voltage drop of the resistor becomes constant. If the drive signal is supplied to the Hall element through the constant current control circuit having the above, the constant current control function of the drive signal can be fulfilled with a very simple circuit.

[0039]

1 shows an embodiment of a Hall element drive circuit according to the present invention. The drive circuit of this embodiment is applied to, for example, the above-described throttle opening sensor (FIGS. 4 and 5) and is applied to a hall element that outputs an electric signal corresponding to the strength of a magnetic field that changes according to the throttle opening. The circuit is configured to supply a drive signal and to accurately compensate for the temperature characteristics of the Hall element and the magnet.

For the sake of convenience, FIG. 1 also shows a specific example of a signal processing circuit for processing the Hall voltage, which is the output of the Hall element, as required to generate a sensing output as the same sensor.

First, the configuration of the Hall element drive circuit and the signal processing circuit thereof of the embodiment will be described.
First, in the drive circuit, the voltage dividing circuit 1 including a series circuit of the resistors R1 and R2 is a circuit that divides the power supply voltage Vcc supplied between the terminals T1 and T2 as needed to generate the reference voltage V1. The generated reference voltage V1 is applied to the non-inverting input terminal (+ terminal) of the operational amplifier A1.

The operational amplifier A1 supplied with the reference voltage V1 constitutes a feedback amplifier circuit 2 for outputting the reference voltage V2 for generating the drive signal of the Hall element 10 in the same drive circuit.

In the feedback amplifier circuit 2, a feedback current control circuit 3 consisting of a series circuit of a resistor 3 and a diode D1 is connected to the feedback path connecting the output terminal and the inverting input terminal (-terminal) as shown in the figure. In addition, in the feedback path, an output voltage control circuit 4 including a series circuit of a diode D2 and a resistor R4 is provided.

As will be described later in detail, the current I2 flowing in the feedback path of the feedback amplifier circuit 2 is the feedback current control circuit 3 described above.
The flow rate is controlled through. Further, the operational amplifier A2, to which the reference voltage V2 output from the feedback amplifier circuit 2 is applied to the non-inverting input terminal, together with the resistor R5 connected in series with the hall element 10, supplies the drive signal to be supplied to the hall element 10. A constant current control circuit 5 that performs constant current control is configured.

In the constant current control circuit 5, the resistance R5 is compared with the reference voltage V2 by comparing the voltage drop of the resistance R5 with the resistance R5.
The voltage applied to the Hall element 10 is controlled so that the voltage drop of 5 becomes constant. As a result, the Hall element 10
As the drive current I, a constant current of I = (V2 / R5) (2) is supplied.

On the other hand, the signal processing circuit 6 for processing the Hall voltage VH output from the Hall element 10 in the manner expressed by the above equation (1) is constructed, for example, as follows. That is, in the signal processing circuit 6, the Hall voltage V
Operational amplifier A in which H is input to each non-inverting input terminal
3 and A4 and the resistors R6 to R8 form a buffer circuit 61 that receives the Hall voltage VH at a high input impedance and stabilizes it. The output of the buffer circuit 61 is input to a differential amplifier circuit 63 including resistors R11 and R12, an operational amplifier A6, and its feedback resistor R13 and an input resistor R14, and differentially amplified. The differential amplified output is used as the sensor output Vo at the terminal T.
3 will be output.

In the signal processing circuit 6, the resistor R
The voltage dividing circuit composed of 9 and R10 and the operational amplifier A5 which receives the divided voltage at its non-inverting input terminal constitute a reference voltage generating circuit 62 which generates the reference voltage of the differential amplifier circuit 63. In the differential amplifier circuit 63, the output (Hall voltage VH) of the buffer circuit 61 is differentially amplified according to the generated reference voltage.

The capacitors C1 and C2 are connected to the terminal T1.
And a capacitor for removing noise, surge, etc. generated at T3. Next, the operation of the Hall element drive circuit of the above embodiment and the temperature characteristic compensation function of the drive circuit will be described in more detail.

When the forward voltages (terminal voltages) of the diodes D1 and D2 respectively arranged in the feedback current control circuit 3 and the output voltage control circuit 4 are VF1 and VF2, respectively, and the power supply voltage is Vcc, these feedbacks are performed. Currents I1 and I2 flowing through the current control circuit 3 and the output voltage control circuit 4
Respectively become I1 = (Vcc-V1-VF1) / R3 ... (3) I2 = I1 + IA ... (4).

Here, IA in the equation (4) is an offset current of the feedback amplifier circuit 2 (operational amplifier A1), and the same current is usually a current of several tens n (nano) to several hundreds n ampere. Become. Therefore, if the current I1 can be set to 10 μA or more, the value of the current I2 can be considered to be substantially I2 = I1 (4) ′. That is, the temperature characteristic compensation accuracy described below will not be deteriorated due to variations in the offset current IA.

On the other hand, when the value of the current I1 becomes larger than necessary, a large capacity element is required at the output part of the operational amplifier A1 including the diodes D1 and D2. That is, when the drive circuit including the signal processing circuit 6 is to be formed into a monolithic IC as described later, the IC chip unnecessarily increases in size or cannot be integrated into one chip. Therefore, the same current I1 is 10 μ to
The resistance value of the resistor R3 is selected so that the current I1 is set to such an optimum value.

Further, according to the above configuration of the drive circuit, the reference voltage V2 which is the output of the feedback amplifier circuit 2 is: V2 = V1 (1 + R4 / R3) -Vcc (R4 / R3) + VF1 (R4 / R3) -VF2 (5)

Here, the reference voltage V1 output from the voltage dividing circuit 1 is V1 = (R2 / (R1 + R2)) Vcc (6) and the forward voltage V of the diodes D1 and D2.
F1 and VF2 are respectively VF1 = VF1 (25) {1-K1 (T-25)} (7) VF2 = VF2 (25) {1-K2 (T-25)} (8) However, VF1 ( 25), VF2 (25): Forward voltage at a temperature of 25 ° C. K1, K2: Temperature coefficient T: It has a negative temperature characteristic expressed as temperature.

Therefore, by substituting these equations (6) to (8) into the equation (5) and rearranging, V2 = Vcc {(R2 / (R1 + R2)) * (1 + R4 / R3) -R4 / R3} + VF1 (25) {1-K1 (T-25)} (R4 / R3) -VF2 (25) {1-K2 (T-25)} (9).

Further, here, the diodes D1 and D2 are
Are provided close to each other in the same circuit (IC), the forward voltages VF1 (25) and VF2 (25) are VF (25), and the temperature coefficients K1 and K2 are K. It becomes possible to express by the value. Therefore, in the above equation (9), V2 = Vcc {(R2 / (R1 + R2)) × (1 + R4 / R3)-(R4 / R3)} + VF (25) {1-K (T-25)} (R4 / R3-1) (10) The reference voltage V2 is applied to the constant current control circuit 6, and the drive current I (= V2 / R5) shown in the above equation (2) is supplied to the hall element 10 through the control circuit 6. Is as described above.

By the way, the Hall element 10 and the magnet 12
As described above, (see FIG. 4) has a negative temperature characteristic. That is, the Hall element 10 shown in the above equation (1)
The sensitivity KH, the internal resistance Rd, and the magnetic flux density B of the magnet 12 show lower values as the temperature rises.

The Hall voltage VH, which is the output of the Hall element 10, is proportional to the drive current I as shown in the equation (1). Therefore, in order to compensate the negative temperature characteristic of the Hall element 10 and the magnet 12, the drive current I, that is, the reference voltage V2 is required to have a positive temperature characteristic opposite thereto.

Therefore, in the circuit of this embodiment, although the diodes D1 and D2 forming the feedback current control circuit 3 and the output voltage control circuit 4 have negative temperature characteristics, the equation (5) is used. As described above, the resistors R3 and R4 are set to have a relationship such as R3> R4 ... (11), paying attention to the fact that the voltage drops (third term and fourth term on the right side) due to the diodes have opposite polarities. To do.

That is, as is apparent from the above equation (10), by setting the resistors R3 and R4 in such a relationship, the term VF (25) {1-K (T-25) in the equation (10) is set. } The part of “(R4 / R3-1)” related to the above becomes a negative value, and the temperature coefficient −K of the same term takes a positive value. That is, through such setting of the resistors R3 and R4, the reference voltage V2 can be given a positive temperature characteristic.

FIG. 2 shows such a temperature characteristic compensation mode by the drive circuit of the embodiment. As shown in FIG.
The sensitivity KH and the internal resistance Rd of the Hall element 10 are the characteristic line L.
1 shows a negative temperature characteristic, and the magnetic flux density B of the magnet 12 is
Suppose that the same shows a negative temperature characteristic like the characteristic line L2, the Hall element 10 and the magnet 12 show a temperature characteristic like the characteristic line L3 as a characteristic obtained by combining them.

With respect to such a negative temperature characteristic of the Hall element 10 and the magnet 12, in the circuit of the embodiment, the resistors R3 and R4 are set in the relationship of the above equation (11), and the ratio of the resistors R3 and R4 is set. Through the size of (10)
Through the relationship such as (R2 / (R1 + R2)) included in the equation, the reference voltage V2 (driving current I) is given a positive temperature characteristic as shown by the characteristic line L4 in FIG.

As a result, the Hall voltage VH output from the Hall element 10 has a temperature characteristic shown by the characteristic line L5 in FIG.
The correction is performed in the manner indicated by, and a proper value is always shown regardless of any change in the ambient temperature.

As described above, according to the Hall element drive circuit of this embodiment, the positive temperature characteristic of the drive current I of the Hall element is positive through the feedback current control circuit 3 and the output voltage control circuit 4 each having the diode D1 or D2. Therefore, the temperature characteristics of the Hall element and the magnet can be suitably compensated.

Further, according to the above-mentioned configuration of the drive circuit, the compensation amount of the temperature characteristic (gradient of the characteristic line L4 in FIG. 2) is used as the current and voltage control amount by the feedback current control circuit 3 and the output voltage control circuit 4. It can be arbitrarily set according to (resistance ratio R4 / R3) or according to the voltage division ratio (R2 / (R1 + R2)) of the voltage dividing circuit 1. Therefore, even if there are variations in the temperature characteristics of the Hall element and the magnet, it becomes possible to easily deal with those variations.

By the way, according to the above-mentioned configuration of the drive circuit of the present embodiment, it is easy to realize this including the signal processing circuit 6 as one monolithic IC.
FIG. 3 shows an example of mounting on a substrate when the drive circuit and the signal processing circuit of the embodiment are realized as a monolithic IC.

That is, in FIG. 3, the substrate 100 is an alumina substrate on which the resistors R1 to R10 are printed. On the substrate 100, the diodes D1 and D2, the operational amplifiers A1 to A6 and the resistors R11 to R11 are formed. A monolithic IC 101 in which R14 is formed integrally and capacitors C1 and C2 are mounted.

Further, in FIG. 3, the terminal electrodes 10a-1
Reference numeral 0d denotes an electrode to which the input / output terminals a to d of the hall element 10 are connected, and similarly terminal electrodes 102 to 104 are electrodes provided corresponding to the power supply terminals T1 and T2 and the output terminal T3 of the same circuit. Is.

According to such a mode of realization as the drive circuit of the embodiment, the signal processing circuit 6 and the like can be greatly downsized, and the cost can be reduced by reducing the number of parts. Become.

Moreover, according to the mounting mode shown in FIG. 3, even after being mounted on the substrate 100 in this way, it is possible to finely adjust the resistance value of at least the resistors R1 to R4 by, for example, laser trimming. It is possible to more easily deal with the variation in the temperature characteristics of the Hall element and the magnet.

In addition, the drive circuit of the same embodiment is used as an IC
The diode D1 and D2 are
It will be naturally provided in the vicinity of C, and the above (1
0), that is, the forward voltage VF1 (25) and VF2 (25) are set to VF (25). -K is the temperature coefficient K1 and K2. Being the same as will be meaningful.

The diodes D1 and D2 are
Not only the characteristics are the same, but also the physical properties are controlled with high precision through the manufacturing process as a semiconductor device, so that the variation between products is extremely small. That is, if the Hall element or the magnet itself to be driven has a constant negative temperature characteristic, the temperature characteristic compensation function described above can be maintained with extremely high accuracy regardless of the product.

In the above embodiment, the forward voltage of the diodes D1 and D2 is used to compensate the temperature characteristics of the Hall element and the magnet. However, the temperature characteristics of the Hall element and the magnet may be compensated. The element that can be formed is not limited to a diode.

That is, any voltage drop element whose drop voltage changes according to temperature may be used, and an appropriate transistor may be used instead of the diode. For example, NP
In the N-junction transistor, the voltage drop (VBE) between the base and the emitter thereof changes according to the temperature, like the forward voltage VF of the diodes. Therefore, the temperature characteristic of the Hall element or the magnet can be compensated by using the base-emitter voltage of the transistor.

Further, in the same embodiment, for convenience, FIG. 4 and FIG.
An example of the circuit for supplying the drive signal to the hall element applied to the throttle opening sensor outlined in the above is shown, but the hall element itself may be applied in any manner.

That is, according to the Hall element drive circuit according to the present invention including the circuit of the embodiment, the temperature characteristics of the Hall element and the magnet are accurately compensated regardless of which apparatus the Hall element is applied to. It is possible to supply a possible driving signal to the Hall element.

[0076]

As described above, according to the Hall element drive circuit of the present invention, even if the Hall element, the magnet or the like is placed in any temperature environment, various characteristics which change depending on the temperature can be preferably provided. It becomes possible to accurately compensate.

Further, according to the present invention, it is possible to favorably reduce the size of the Hall element driving circuit including the reduction of the number of parts while maintaining the high temperature compensation performance.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a Hall element drive circuit according to the present invention.

FIG. 2 is a graph showing a mode of temperature characteristic compensation by the circuit of the embodiment.

FIG. 3 is a schematic plan view showing how the circuit of the embodiment is mounted on a substrate.

FIG. 4 is a schematic diagram showing a principle of detecting a throttle opening degree by a hall element.

FIG. 5 is a graph showing output characteristics of the Hall element based on the same detection principle.

FIG. 6 is a circuit diagram showing an example of a well-known Hall element drive circuit.

[Explanation of symbols]

1 ... Voltage dividing circuit, 2 ... Feedback amplifier circuit, 3 ... Feedback current control circuit, 4 ... Output voltage control circuit, 5 ... Constant current control circuit, 6,
20 ... Signal processing circuit, 10 ... Hall element, 11 ... Rotor, 12 ... Magnet (permanent magnet), 61 ... Buffer circuit, 6
2 ... Reference voltage generation circuit, 63 ... Operation amplification circuit, 100 ...
Alumina substrate, 101 ... Monolithic IC, 10a to 1
0d, 102 to 104, T1 to T3 ... Terminal, A, A1
A6 ... Operational amplifier, C1, C2 ... Capacitors, R1 to R
14, R21 to 27 ... Resistance.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5/62 G01B ⁷ /00-7/34 G01P 1/00-3/80

Claims (4)

(57) [Claims] 1. A Hall element drive circuit that supplies a drive signal to a Hall element that outputs an electric signal corresponding to the strength of a magnetic field by using the Hall effect, and a feedback amplification circuit that feeds back and amplifies a reference voltage; A feedback current control circuit including a voltage drop element whose drop voltage changes in accordance with the feedback path of the feedback amplification circuit and controlling a current flowing through the feedback path; and the feedback amplification circuit also including the voltage drop element. An output voltage control circuit arranged in the feedback path of the output voltage control circuit for controlling the output voltage of the feedback amplification circuit, wherein the output voltage of the feedback amplification circuit is controlled by the feedback current control circuit and the output voltage control circuit. A hall element drive circuit, which supplies a drive signal to the hall element based on the above. 2. The feedback current control circuit includes a series circuit of a first diode and a first resistor, and the output voltage control circuit includes a second diode and a second resistor. A series circuit is included, and the output of the feedback amplifier circuit is the first resistor and the second resistor.
The positive temperature characteristic is set based on the relationship of the resistance value of the first resistance with the resistance value of the second resistance> the resistance value of the second resistance.
Hall element drive circuit described. 3. The hall according to claim 2, wherein the feedback current control circuit sets the resistance value of the first resistor so that the current flowing through the feedback path of the feedback amplifier circuit is controlled to 10 μm to 1 mAmps. Element drive circuit. 4. The Hall element drive circuit according to claim 1, 2 or 3, wherein the resistance connected in series with the Hall element is compared with the voltage drop of the resistance and the output of the feedback amplification circuit, and the same resistance is obtained. Hall element comprising an operational amplifier for controlling the voltage applied to the Hall element so that the voltage drop of the Hall element becomes constant, and a constant current control circuit for supplying the drive signal to the Hall element. Drive circuit.