KR20050017942A - Geomagnetic sensor driver and electronic compass using the same - Google Patents

Abstract

PURPOSE: A geomagnetic sensor driver and an electronic compass using the same are provided to stably achieve a detection signal by applying an optimum driving current to geomagnetic sensors having different impedances. CONSTITUTION: A geomagnetic sensor driver includes a static voltage generating unit(42A) for generating a static voltage according to a driving current control signal of a controlling unit. A static current generating unit(42B) is provided to generate static current according to the static voltage of the static voltage generating unit(42A). A driving pulse generating unit(42C) generates a driving pulse according to an operation controlling signal of the controlling unit. A sensor driving unit(42D) is operated by the static current generated from the static current generating unit(42B).

Description

Geomagnetic Sensor Driver and Electronic Compass Device Using Them {GEOMAGNETIC SENSOR DRIVER AND ELECTRONIC COMPASS USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic compass device that can be applied to a GPS system, a game machine, etc., and in particular, adopts a constant current driving method to provide a constant driving current regardless of a change in operating voltage or temperature change, and a different impedance through feedback control The present invention also relates to a geomagnetic sensor driver and an electronic compass device using the same, by providing and driving an optimum drive current for the geomagnetic sensor having a stable detection signal, thereby improving the performance of an applied product.

In general, the azimuth angle is very important in identifying and operating the ship's route and position, and has been measuring the azimuth angle using the magnetism of the magnet for hundreds of years. The representative devices are magnetic compass and gyro. Compass (Gyrocompass). In other words, magnetic compass is an azimuth measuring device using the properties of geomagnetism, but its principle is simple, but its precision is inferior due to distortion of geomagnetism distribution. As modernization and high technology are being developed, not only are they insufficient in function, but they also have problems in that they cannot use the bow angle information from their compasses in other electronic devices.

In addition, there is a gyro compass as another orientation measuring device, which is excellent in accuracy compared to magnetic compasses, but it is very expensive and has a long maneuver preparation time, so it is soft and has a long time to enter and leave ports and ports such as small fishing boats and leisure boats. You have a problem that is not appropriate. It has been developed to meet the above problems is an electromagnetic compass (Electro Magnetic Compass), such an electromagnetic compass has been developed and used in the market for a long time in Gumi.

A configuration diagram of such a conventional electromagnetic compass (hereinafter referred to as an electronic compass device) is shown in FIG. 1.

1 is a block diagram of a conventional electronic compass device.

Referring to FIG. 1, the conventional electronic compass device operates according to a sensor driver 11 for generating driving signals DP1 and DP2 and a geomagnetism which detects the orientation of the geomagnetism by operating in accordance with a driving signal from the sensor driver 11. A sensor 12, a signal processor 13 for amplifying the detection signal from the geomagnetic sensor 12 after the filter processing, and an operation of the sensor driver 11 are controlled to detect the signal from the signal processor 13 And a drive controller 14 for calculating an azimuth angle based on the signal. Here, the geomagnetic sensor 12 typically uses a flux valve, which uses an X-Y quadrature coil called a flux gate.

2 is a configuration diagram of a conventional geomagnetic sensor driver and a geomagnetic sensor.

Referring to FIG. 2, the sensor driver 11 includes a pulse generator 11A for generating drive pulses and a plurality of inverters 11B-11D for inverting phases of the drive pulses of the pulse generator 11A. And the driving pulses generated in this way and the inverted driving pulses to the geomagnetic sensor 12, respectively, so that the geomagnetic sensor 12 can be operated.

The geomagnetic sensor 12 is formed by the primary coil WC1 through which the drive current from the sensor driver 11 flows, the drive current flowing through the primary coil WC1, and the azimuth angle at which the sensor is placed. It is modeled as including a secondary coil WC2 that generates an induced voltage. In order to drive the driving current to the primary coil WC1, two driving pulses having inverted phases with each other should be provided. The simplest method of realizing this is to use an inverter.

3 is an inverter configuration diagram of a conventional sensor driver.

Referring to FIG. 3, each of the inverters 11B-11D of the sensor driver is connected in parallel with a PMOS transistor and an NMOS transistor. The inverters 11B-11D are operated by the operating voltage VDD. According to the phase of the input driving pulse DP, the PMOS transistor and the NMOS transistor alternately operate with each other so that the first driving pulse DP1 and the driving pulse DP inverting the phase of the driving pulse DP are placed. The second driving pulse DP2 inverted once is outputted to the geomagnetic sensor 12, respectively. Here, the inverter performs phase inversion of the driving pulse and buffering of the signal.

By the way, in the conventional sensor driver, when the operating voltage VDD is unstable due to the change of the power supply unit, the level of the driving pulse output from the inverter is also unstable depending on the operating voltage. The PMOS and NMOS transistors included in the PMOS and NMOS transistors have a problem in that the phase of the driving pulse output from the inverter changes according to the temperature change due to the characteristic of changing the threshold voltage according to the ambient temperature.

In addition, the geomagnetic sensor has its own impedance, and each geomagnetic sensor has a slightly different impedance, and due to the difference in impedance, the geomagnetic sensor appears in the secondary coil WC2 even though the driving current flowing through the primary coil WC1 is the same. The magnitude of the induced voltage is different from each other.

As described above, the azimuth output changes due to a change in the operating voltage of the inverter, a change in the threshold voltage of each MOS transistor, and a difference in its own impedance of each sensor. Will reduce the reliability of the applied product.

The present invention has been proposed to solve the above problems, the object of which is to adopt a constant current driving method to provide a constant drive current regardless of operating voltage fluctuations or temperature changes, geomagnetic having different impedances through feedback control The present invention provides a geomagnetic sensor driver and an electronic compass device using the same, by providing an optimum driving current and driving the sensor, thereby making the detection signal stable and thus improving the performance of an applied product.

In order to achieve the above object of the present invention, the geomagnetic sensor driver of the present invention

In the geomagnetic sensor driver which is controlled by a control unit for providing an operation control signal (SOC) and a predetermined drive current control signal (SDI), to drive a geomagnetic sensor for detecting an induced voltage corresponding to the geomagnetic azimuth angle,

A constant voltage generator configured to generate a constant voltage set according to a driving current control signal SDI of the controller;

A constant current generator for generating a constant current set according to the constant voltage of the constant voltage generator;

A driving pulse generator for generating a driving pulse according to an operation control signal SOC of the controller; And

A sensor driver which is operated by the constant current of the constant current generator and outputs two drive pulses DP1 and DP2 having phase inversion relations from the drive pulse generator to the geomagnetic sensor.

Characterized in that it comprises a.

In addition, the electronic compass device of the present invention

A geomagnetic sensor that outputs an induced voltage corresponding to the geomagnetic azimuth;

The operation of the geomagnetic sensor is controlled by a control signal SOC, an optimal reference signal for the geomagnetic sensor is set, and an optimum driving current is generated according to the deviation between the reference signal and the detection signal. A control unit for controlling the geomagnetic azimuth angle based on the detected detection signal;

Two driving pulses DP1, which operate according to the operation control signal SOC of the controller, generate a constant current according to the generation control signal SDI of the controller, and are driven by the constant current and are in inverted relation with each other. A sensor driver for generating DP2) and outputting it to the geomagnetic sensor; And

A signal processor for detecting an induced voltage from the geomagnetic sensor, amplifying and converting the detected voltage, and outputting the detected voltage to the controller.

Characterized in having a.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of an electronic compass device according to the present invention.

Referring to FIG. 4, the electronic compass device according to the present invention controls the operation of the geomagnetic sensor 43 and the geomagnetic sensor 43 to output an induced voltage corresponding to the geomagnetic azimuth angle using a control signal SOC. After setting the optimal reference signal for the geomagnetic sensor, the optimum driving current is controlled by the control signal SDI according to the deviation between the reference signal and the detection signal, and the geomagnetic azimuth is detected based on the input detection signal. The controller 41 operates in accordance with the operation control signal SOC of the controller 41, and generates a constant current according to the generation control signal SDI of the drive current of the controller 41. The sensor driver 42 which generates two driving pulses DP1 and DP2 which are driven and inverted mutually and outputs them to the geomagnetic sensor 43 and the induced voltage from the geomagnetic sensor 43 are detected. Voltage amplification and signal conversion And a signal processor 44 output to the controller 41.

5 is an overall operation flowchart of the drive control unit of the present invention.

Referring to FIG. 5, the control unit 41 controls the operation of the geomagnetic sensor with a control signal SOC, and then compares a current detection signal with a previous detection signal while comparing the maximum voltage among the detection signals from the signal processor 44. Set an optimal reference signal corresponding to the control signal, and output a driving current control signal (SDI) to the sensor driver 42 to control the driving current according to a deviation between the magnitude of the input detection signal and the magnitude of the reference signal. Is done.

6 (a) and 6 (b) are characteristic graphs of a sensor for setting an optimum reference voltage according to the present invention. In FIGS. 6 (a) and 6 (b), the horizontal axis is supplied to the primary coil of the geomagnetic sensor. The driving current, and the vertical axis, are induced voltages appearing in the secondary coil of the geomagnetic sensor.

Referring to (a) and (b) of FIG. 6, the geomagnetic sensor has a characteristic in which the secondary induced voltage changes as shown in FIG. 6 (a) with respect to the primary driving current, and FIG. 6 (b). In reference, each sensor shows a different induced voltage for the primary driving current.

Referring to (a) and (b) of FIG. 6, the controller 41 is a current corresponding to the center of the region where the variation of the induced voltage is insensitive to the impedance change of the geomagnetic sensor, that is, the inflexion region showing the maximum induced voltage. The value is set as the optimum drive current value, and the voltage corresponding to the set drive current value is set as the reference voltage.

7 is a flowchart illustrating an optimal reference signal setting using a register according to the present invention.

Referring to FIG. 7, the controller 41 sets a reference signal to a current control register, detects an output signal of the geomagnetic sensor, and compares the magnitude of the current detection signal of the geomagnetic sensor with the magnitude of the recent detection signal. When the current detection signal is large, the reference signal is reset by increasing the size of the reference signal to a unit size, and when the current detection signal is small, the reference signal corresponding to the previous detection signal is set as an optimal reference signal. Is done.

8 is an output waveform diagram of a geomagnetic sensor according to the present invention.

Referring to FIG. 8, the output waveform of the geomagnetic sensor is a sinusoidal wave, which is a sinusoidal wave about two axes (X and Y).

9 is a schematic diagram of a controller 41 according to the present invention.

Referring to FIG. 9, the controller 41 according to the present invention includes a current control register for storing data corresponding to an optimal reference signal set through the process shown in FIG. 7, and a data stored in the current control register for driving current. It includes a decoder to decode the control signal (SDI) and output to the sensor driver 42.

10 is a configuration diagram of a sensor driver according to the present invention.

Referring to FIG. 10, the sensor driver 42 may include a constant voltage generator 42A for generating a constant voltage set according to a drive current control signal SDI of the controller 41, and the constant voltage generator 42A. A constant current generator 42B for generating a constant current set according to the constant voltage, a drive pulse generator 42C for generating drive pulses in accordance with an operation control signal SOC of the controller 41, and the constant current generator ( And a sensor driver 42D which is operated by the constant current of 42B to output two drive pulses DP1 and DP2 which are in phase inversion relationship with the drive pulse DP from the drive pulse generator 42C.

FIG. 11 is a configuration diagram of the constant voltage generator of FIG. 10.

Referring to FIG. 11, the constant voltage generator 42A includes a reference voltage generator 81 generating a preset reference voltage, a reference voltage Vref and a resistor R of the reference voltage generator 81. Variable resistance unit 83 is connected to the constant current source 82 for generating a constant current and the resistance (R) of the constant current source 82 in series to change the resistance according to the drive current control of the controller 41 It includes.

The variable resistor unit 83 is implemented as an element or a circuit capable of varying a resistance value according to a control signal SDI. In a simple circuit example, a switch is connected to each of a plurality of resistors connected in series. By turning on / off as a control signal, the total resistance value can be varied.

12 is a configuration diagram of the constant current generator of FIG. 10.

Referring to FIG. 12, the constant current generator 42B includes a constant current source 91 that generates a constant current according to the constant voltage Vds and the resistance R of the constant voltage generator 42A, and the constant current source 91. And a current source mirror 92 connected by an overcurrent mirror.

FIG. 13 is a configuration diagram illustrating a sensor driver of FIG. 10.

Referring to FIG. 13, the sensor driver 42C is driven by the constant current from the constant current generator 42B, and inverts the phase of the drive pulse of the drive pulse generator 42C to the geomagnetic sensor 43. The first inverter 101 to be outputted to the output, the second inverter 102 to invert the phase of the drive pulse of the drive pulse generator 42C, and the output signal of the second inverter 102 by inverting the geomagnetic And a third inverter 103 output to the sensor 43.

Here, each of the plurality of inverters is formed by connecting a PMOS transistor and an NMOS transistor in parallel. The inverters 11B-11D are operated by a constant current source, and the PMOS is in accordance with the phase of an input driving pulse DP. The first driving pulse DP1 inverting the phase of the driving pulse DP and the second driving pulse DP2 inverting the driving pulse DP twice are alternately operated by the transistor and the NMOS transistor alternately operating. Output to the geomagnetic sensor 12.

14 is a control signal-detection signal correlation graph according to the present invention.

In FIG. 14, the vertical axis represents a driving current of the geomagnetic sensor, and the horizontal axis represents a control signal for controlling the driving current of the geomagnetic sensor.

Hereinafter, the operation and effects of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 4, when the controller 41 of the electronic compass device of the present invention controls the operation of the sensor by the sensor driver 42 with the control signal SOC, the sensor driver 42 may be connected to the controller 41. It operates in accordance with the operation control signal SOC. In addition, the controller 41 controls the driving current to the control signal SDI according to the magnitude of the input detection signal, and accordingly, the sensor driver 42 controls the driving current control signal SDI of the controller 41. A constant current is generated, and two driving pulses DP1 and DP2 which are operated by this constant current are in mutual phase inversion relationship.

In addition, the geomagnetic sensor 43 operates by a drive current generated by a driving pulse from the sensor driver 11 to output an induced voltage corresponding to the geomagnetic azimuth angle at which the sensor is placed, to the signal processor 44. 44 detects the induced voltage from the geomagnetic sensor 12, amplifies and converts the detected signal, and outputs the detected signal to the controller 41. The controller 41 detects the geomagnetic azimuth angle based on the detection signal from the signal processor 44.

Referring to FIG. 5, the controller 41 controls the operation of the geomagnetic sensor 43 with a control signal SOC, and compares a current detection signal with a previous detection signal, and compares the detection signal from the signal processor 44. An optimum reference signal corresponding to the maximum voltage is set (S51), a detection signal is input from the signal processor 44, and a deviation between the magnitude of the detection signal and a preset reference signal is calculated (S52, S53) and outputs a drive current control signal SDI to the sensor driver 42 according to this deviation (S54, S55).

The optimal reference signal setting procedure will be described with reference to FIGS. 6A, 6B, 7 and 8.

First, as shown in (a) of FIG. 6, the characteristic of the sensor is that the secondary induced voltage gradually increases with the increase of the primary driving current, but at some point ③ despite the increase of the primary driving current. The secondary induced voltage gradually decreases. In the region “①” centered on the point (inflection point) indicated by “③” in FIG. 6A, the change of the induced voltage is not large even when the drive current is changed, where the current at the point indicated by “③” is optimally driven. Corresponds to the current.

As shown in Fig. 6B, each sensor has the same characteristics as shown in Fig. 6A, except that the points corresponding to the inflection point are "①", "②" and "③", respectively. Each is different.

As described above, the controller 41 determines an optimum drive current value by setting a current value corresponding to the center of the current range 1 where the change in induced voltage 2 is insensitive to the impedance change of the geomagnetic sensor. Set the voltage corresponding to the current value as the reference signal. This will be described with reference to FIG. 7.

Referring to FIG. 7, first, an arbitrary reference signal is set in the current control register (S71), and after controlling the operation of the geomagnetic sensor of the present invention (S72), if the rotation of the geomagnetic sensor is controlled (S73), The geomagnetic sensor generates a sinusoidal wave output as shown in FIG. 8. At this time, the magnitude of the output signal of the geomagnetic sensor is detected (S74), and the magnitude of the detection signal is compared with the previous signal (S75). When the current detection signal is larger than the previous signal, the current control register value is converted into a unit size ( For example, the current control register is reset by increasing by "1" (S76), and when the current detection signal is smaller than the previous signal, the current control register value is decreased by a unit size (for example, "1") (S77). ), An optimal reference signal is set in the current control register.

That is, if the induced voltage detected by the geomagnetic sensor is set as the reference voltage based on the optimum drive current value, when the optimum drive current is provided to the geomagnetic sensor, there is almost no difference between the detected induced voltage and the reference voltage. However, due to the difference in the sensor's own characteristics such as the impedance of the geomagnetic sensor itself, even if the optimum drive current is supplied, the detected induced voltage will appear slightly different, and the drive current is converted by the difference between the detected voltage and the reference voltage. It is possible to detect the optimal induced voltage.

Referring to FIG. 9, through the above process, the data set in the internal current control register of the controller 41 is decoded by the decoder of the controller 41 and the sensor driver 42 as a driving current control signal SDI. )

Referring to FIG. 10, the constant voltage generator 42A of the sensor driver 42 generates a constant voltage set according to the drive current control signal SDI of the controller 41, and the constant current of the sensor driver 42. The generator 42B generates a constant current set according to the constant voltage of the constant voltage generator 42A, and the driving pulse generator 42C of the sensor driver 42 is an operation control signal SOC of the controller 41. To generate a driving pulse. In addition, the sensor driver 42D of the sensor driver 42 is operated by the constant current of the constant current generator 42B to phase shift the driving pulses DP from the drive pulse generator 42C to each other. Two driving pulses DP1 and DP2 are output.

Referring to FIG. 11, the reference voltage generator 81 of the constant voltage generator 42A generates a preset reference voltage Vref, and the constant current source 82 of the constant voltage generator 42A is the reference. The constant current is generated by the reference voltage Vref of the voltage generator 81 and the resistor R, and the variable resistor 83 of the constant voltage generator 42A is formed of the resistance of the constant current source 82. In series with R), the variable resistor Rv is determined according to the drive current control of the controller 41. In this case, the constant voltage Vds of the constant voltage generator 42A is expressed by Equation 1 below.

Referring to FIG. 12, the constant current source 91 of the constant current generator 42B generates the constant current Ids according to the constant voltage Vds and the resistance R of the constant voltage generator 42A, and generates the constant current. The current source mirror 92 of the part 42B is connected to the constant current source 91 by a current mirror to generate a current generated by the constant current source 91, wherein the current source mirror 92 is formed according to the size of a transistor constituting the current source mirror. A multiplier current may be generated with respect to the current of the current source, wherein the constant current Ids of the constant current generator 42B is expressed by Equation 2 below.

Again, referring to FIGS. 6A and 6B, the secondary coils of the geomagnetic sensors 43 according to the driving current supplied to the primary coils WC1 of the geomagnetic sensors 43 of the present invention. The induced voltage appearing in WC2 is changed, and at this time, the driving current corresponding to the center of the region where the change in the dielectric voltage is least is determined, and this driving current is shown in FIG. 14 by the control signal of the controller 41. As controlled.

Referring to FIG. 13, the sensor driver 42C is driven by the constant current Ids from the constant current generator 42B, and the drive pulse generated by the drive pulse generator 42C is the first inverter 101. Phase inverted), the inverted signal DP1 is output to one end of the primary coil WC11 of the geomagnetic sensor 43, and the second inverter 102 and the third inverter 103 are The driving pulses of the driving pulse generator 42C are sequentially inverted, and the inverted driving pulses DP2 are output to the other end of the primary coil WC1 of the geomagnetic sensor 43.

Each of the plurality of inverters is formed by connecting a PMOS transistor and an NMOS transistor in parallel. The inverters 11B-11D are operated by a constant current source, and the PMOS transistor and the PMOS transistor are in accordance with the phase of an input driving pulse DP. The NMOS transistors alternately operate to output the driving pulses in which the phases of the driving pulses DP are inverted.

Through this process, the driving pulse output to the geomagnetic sensor 43 becomes a stable driving pulse irrespective of changes in ambient temperature, operating voltage, and the like, and by performing feedback control, despite the impedance difference of the geomagnetic sensor itself. Thus, a stable detection signal can be obtained.

According to the present invention as described above, by adopting a constant current driving method to provide a constant drive current regardless of the operating voltage fluctuations or temperature changes, and through the feedback control to the optimum drive current for geomagnetic sensors having different impedances By providing and driving, the detection signal is stabilized, thereby improving the performance of the applied product.

The above description is only a description of specific embodiments of the present invention, and the present invention is not limited to these specific embodiments, and various changes and modifications of the configuration are possible from the above-described specific embodiments of the present invention. It will be apparent to those skilled in the art to which the present invention pertains.

1 is a block diagram of a conventional electronic compass device.

2 is a configuration diagram of a conventional geomagnetic sensor driver and a geomagnetic sensor.

3 is an inverter configuration diagram of a conventional geomagnetic sensor driver.

4 is a block diagram of an electronic compass device according to the present invention.

5 is a flowchart illustrating the overall operation of the controller of the present invention.

6 (a) and 6 (b) are characteristic graphs of a sensor for setting an optimum reference voltage according to the present invention.

7 is an output waveform diagram of a geomagnetic sensor according to the present invention.

8 is a flowchart illustrating an optimal reference signal setting using a register according to the present invention.

9 is a schematic diagram of a controller 41 according to the present invention.

10 is a configuration diagram of a geomagnetic sensor driver according to the present invention.

FIG. 11 is a configuration diagram of the constant voltage generator of FIG. 10.

12 is a configuration diagram of the constant current generator of FIG. 10.

FIG. 13 is a configuration diagram illustrating a sensor driver of FIG. 10.

14 is a control signal-detection signal correlation graph according to the present invention.

Explanation of symbols on the main parts of the drawings

41 control unit 42 sensor driver

42A: constant voltage generator 42B: constant current generator

42C: drive pulse generator 42D: sensor driver

43: geomagnetic sensor 44: signal processor

81: reference voltage generator 82: constant current source

83: variable resistance section 91: constant current source

92: current source mirror

Claims (9)

Geomagnetic sensor driver which is controlled by the controller 41 which provides the operation control signal SOC and the preset drive current control signal SDI, and drives the geomagnetic sensor 43 which detects an induced voltage corresponding to the geomagnetic azimuth angle. To A constant voltage generator 42A generating a constant voltage set according to the drive current control signal SDI of the controller 41; A constant current generator 42B for generating a constant current set according to the constant voltage of the constant voltage generator 42A; A drive pulse generator 42C for generating a drive pulse according to the operation control signal SOC of the controller 41; And The geomagnetic sensor 43 operates two driving pulses DP1 and DP2 which are operated by the constant current of the constant current generating unit 42B and have a phase inversion relationship between the driving pulses DP from the driving pulse generating unit 42C. Sensor drive unit 42D for outputting Geomagnetic sensor driver comprising a. The method of claim 1, wherein the constant voltage generator 42A A reference voltage generator 81 generating a preset reference voltage; A constant current source 82 generating a constant current according to the reference voltage Vref and the resistor R of the reference voltage generator 81; And The variable resistor unit 83 is connected in series with the resistor R of the constant current source 82 to change a resistance value according to the driving current control signal SDI of the controller 41. Geomagnetic sensor driver comprising a The method of claim 1, wherein the constant current generator 42B A constant current source 91 generating a constant current according to the constant voltage Vds and the resistance R of the constant voltage generator 42A; And A current source mirror 92 connected to the constant current source 91 by a current mirror to provide a driving current to the sensor driver 42D. Geomagnetic sensor driver comprising a A geomagnetic sensor 43 for outputting an induced voltage corresponding to the geomagnetic azimuth; The operation of the geomagnetic sensor 43 is controlled by a control signal SOC, the optimum reference signal for the geomagnetic sensor is set, and the optimum drive current is generated according to the deviation between the reference signal and the detection signal. A control unit 41 controlled by a signal SDI and detecting a geomagnetic azimuth angle based on an input detection signal; It operates according to the operation control signal SOC of the controller 41, generates a constant current according to the generation control signal SDI of the drive current of the controller 41, and is driven by the constant current to be inverted with each other. A sensor driver 42 which generates two driving pulses DP1 and DP2 and outputs them to the geomagnetic sensor 43; And A signal processor 44 for detecting an induced voltage from the geomagnetic sensor 43, amplifying and signal converting the detected voltage, and outputting the detected voltage to the controller 41. Electronic compass device comprising a. The method of claim 4, wherein the control unit 41 After controlling the operation of the geomagnetic sensor with a control signal SOC, comparing the current detection signal with the previous detection signal, an optimum reference signal corresponding to the maximum voltage among the detection signals from the signal processor 44 is set and inputted. And a driving current control signal (SDI) to the sensor driver 42 to control the driving current according to a deviation between the magnitude of the detected signal and the magnitude of the reference signal. The method of claim 5, wherein the control unit 41 The reference signal is set in the current control register, the output signal of the geomagnetic sensor is detected, and the magnitude of the current detection signal of the geomagnetic sensor is compared with the magnitude of the recent detection signal. The reference signal is reset by increasing the size to a unit size, and when the current detection signal is small, the electronic compass device is configured to set the reference signal corresponding to the previous detection signal as an optimum reference signal. 5. The sensor driver according to claim 4, wherein the sensor driver 42 A constant voltage generator 42A generating a constant voltage set according to the drive current control signal SDI of the controller 41; A constant current generator 42B for generating a constant current set according to the constant voltage of the constant voltage generator 42A; A drive pulse generator 42C for generating a drive pulse according to the operation control signal SOC of the controller 41; And The geomagnetic sensor 43 operates two driving pulses DP1 and DP2 which are operated by the constant current of the constant current generating unit 42B and have a phase inversion relationship between the driving pulses DP from the driving pulse generating unit 42C. Sensor drive unit 42D for outputting Electronic compass device comprising a. The method of claim 7, wherein the constant voltage generator 42A A reference voltage generator 81 generating a preset reference voltage; A constant current source 82 generating a constant current according to the reference voltage Vref and the resistor R of the reference voltage generator 81; And The variable resistor unit 83 is connected in series with the resistor R of the constant current source 82 to change the resistance according to the driving current control signal SDI of the controller 41. Electronic compass device comprising a. The method of claim 7, wherein the constant current generator 42B A constant current source 91 generating a constant current according to the constant voltage Vds and the resistance R of the constant voltage generator 42A; And A current source mirror 92 connected to the constant current source 91 by a current mirror to provide a driving current to the sensor driver 42D. Electronic compass device comprising a.