TWI722128B - Magnetic sensor and magnetic sensor device - Google Patents

Abstract

The present invention provides a magnetic sensor and a magnetic sensor device, which can accurately determine abnormalities such as disconnection or short circuit of the wiring of the magnetic sensor device. The output control circuit of the magnetic sensor includes a voltage divider circuit connected to the output terminal and an amplifier. The amplifier controls the gate voltage of the MOS transistor connected to the output terminal of the magnetic sensor so that the divided voltage The voltage of the circuit becomes equal to the reference voltage, so the output voltage of the magnetic sensor is determined by the voltage division ratio of the reference voltage and the voltage divider circuit.

Description

Magnetic sensor and magnetic sensor device

The present invention relates to a magnetic sensor, and in more detail, it relates to a magnetic sensor and a magnetic sensor device with a structure in which an output terminal is externally pulled up.

The magnetic sensor device is equipped with a magnetic detection element that converts the magnetic flux density into an electrical signal, and detects the magnetic flux density that changes according to the change in the relative distance from the detected member provided with a magnetic body, and a preset magnetic flux density threshold. The magnitude of the electrical property is determined, and the detection signal of the two-level voltage is output. In the switching system (switching system) using a magnetic sensor, especially in the automotive field, in order to provide safety to car users, it is required to construct the system from the viewpoint of functional safety (ISO26262). For example, it is required to eliminate the doubt that erroneous switching operations are performed due to the failure of the magnetic sensor element itself or the failure of the signal transmission path in the system.

Figure 4 is a conventional magnetic sensor device. The magnetic sensor 50 includes a signal processing circuit 51 including a magnetic sensor, a transistor 52, a constant current circuit 53 and a resistor 54. The discrimination circuit 59 and the magnetic sensor 50 are connected to GND in common, and the terminal IN is connected to the terminal OUT of the magnetic sensor 50. Furthermore, the terminal IN of the magnetic sensor 50 is pulled up to the voltage VDD by the pull-up resistor 58.

The magnetic sensor 50 outputs two values of a high level value lower than the voltage VDD by a predetermined value and a low level value higher than the voltage GND by a predetermined value to the terminal OUT. The discrimination circuit 59 has an abnormality detection function, that is, it is determined to be abnormal when the input voltage level is a voltage outside the vicinity of these two values.

In this manner, by determining that the predetermined voltage level that is not equivalent to the voltage VDD or the voltage GND is normal, it is possible to easily detect an abnormality such as a disconnection of the input terminal. For example, when the wiring between the terminal OUT of the magnetic sensor 50 and the terminal IN of the discrimination circuit 59 is disconnected and becomes an open circuit (open), the input level of the discrimination circuit 59 becomes the voltage VDD, and therefore it is determined as abnormal. Furthermore, when the wiring between the terminal OUT of the magnetic sensor 50 and the terminal IN of the discrimination circuit 59 is short-circuited to the voltage GND, the input level of the discrimination circuit 59 becomes the voltage GND, and therefore it is determined to be abnormal. [Prior Art Document] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2001-165944 [Problems to be Solved by Invention]

In the case of the circuit structure, the input voltage level of the discrimination circuit 59 in the normal state is determined by the resistor 54, the constant current circuit 53, the transistor 52, and the pull-up resistor 58. Therefore, there is a problem in that the resistance value of the pull-up resistor 58 may vary due to manufacturing variations, and therefore the input voltage level may vary, which may lead to a misjudgment by the discrimination circuit 59.

[Means for Solving the Problem] In order to solve this problem, the output control circuit of the magnetic sensor of the present invention includes a voltage divider circuit connected to the output terminal and an amplifier, and the amplifier pair is connected to the output terminal of the magnetic sensor. The gate voltage of the MOS (Metal Oxide Semiconductor) transistor is controlled so that the voltage of the voltage divider circuit becomes equal to the reference voltage. [Effects of the invention]

According to the magnetic sensor of the present invention, the output voltage of the magnetic sensor is determined by the voltage division ratio of the reference voltage and the voltage divider circuit, so it has the effect of not being affected by the resistance deviation of the pull-up resistor. Therefore, the discrimination circuit can accurately determine abnormalities such as disconnection or short-circuit of the wiring of the magnetic sensor device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a circuit diagram showing the first embodiment of the magnetic sensor of the present invention. The magnetic sensor device includes a magnetic sensor 1, a pull-up resistor 18 and a discrimination circuit 19.

The magnetic sensor 1 of the first embodiment includes a magnetic sensor element 3, a magnetic determination circuit 4, and an output control circuit 10. The output control circuit 10 includes a MOS switch 5, an output drive element 6, an amplifier 7, a reference voltage circuit 8, and a resistor R1, a resistor R2, and a resistor R3 as a voltage divider circuit.

The output terminal OUT of the magnetic sensor 1 is connected to the input terminal of the discrimination circuit 19 and is connected to the external power supply terminal VPU via the pull-up resistor 18. The input terminal of the magnetic sensor element 3 is connected to the power supply terminals VDD and GND, and the output terminal is connected to the input terminal of the magnetic determination circuit 4. The output driving element 6 includes, for example, an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), the drain is connected to the output terminal OUT, and the source is connected to the ground terminal. GND. One end of the resistor R1 is connected to the output terminal OUT, and the other end (node N1) is connected to one end of the resistor R2. The other end of the resistor R2 (node N2) is connected to one end of the resistor R3. The other end of the resistor R3 is connected to the ground terminal GND. The output terminal of the amplifier 7 is connected to the gate of the output driving element 6, the inverting input terminal is connected to the output terminal of the reference voltage circuit 8, and the non-inverting input terminal is connected to the node N1. The MOS switch 5 includes, for example, an N-channel MOSFET, the gate is connected to the output terminal of the magnetic determination circuit 4, the drain is connected to the node N2, and the source is connected to the ground terminal GND.

In addition to the function of distinguishing the high-level value and the low-level value corresponding to the magnetic flux density output by the magnetic sensor 1, the discrimination circuit 19 also has an abnormality detection function. The abnormality detection function is to determine that the magnetic sensor device is normal when the input voltage is in the vicinity of the high level value and the low level value. When the input voltage is outside the voltage range, the magnetic sensor device is determined to be If it is abnormal, the magnetic sensor element 3 uses the voltage VDD as a power source, and outputs an electrical signal corresponding to the magnetic flux density input to the magnetic sensor element. For the magnetic sensor element 3, for example, a Hall element can be used. The magnetic determination circuit 4 compares the electrical signal output by the magnetic sensor element 3 with a preset threshold signal, and outputs the magnetic determination result to the output control circuit 10 as a binary voltage of the voltage VDD and the voltage GND.

When the output of the magnetic determination circuit 4 is the voltage GND, the MOS switch 5 is in an OFF state, and the node N2 is connected to the ground terminal GND through the resistor R3. On the other hand, when the output of the magnetic determination circuit 4 is the voltage VDD, the MOS switch 5 is in an ON state, and the node N2 is connected to the ground terminal GND.

Between the output terminal OUT and the ground terminal GND, an output driving element 6 is electrically connected in parallel with the voltage divider circuit. The output driving element 6 is an N-channel MOSFET, and by controlling the gate voltage, the drain current can flow between the output terminal OUT and the ground terminal GND. Moreover, the non-inverting input terminal of the amplifier 7 is connected to the node N1, the inverting input terminal is connected to the reference voltage circuit 8, and the output terminal is connected to the gate terminal of the output driving element 6, so the output driving element 6 is controlled so that the node The voltage of N1 is equal to the reference voltage of the reference voltage circuit 8.

If the output voltage of the output terminal OUT of the magnetic sensor 1 is VOUT and the reference voltage of the reference voltage circuit 8 is VREF, the output voltage VOUT is expressed in two formulas according to the situation of the magnetic determination result. VOUT=(1+R1/R2)×VREF…(1) VOUT={1+R1/(R2+R3)}×VREF…(2) Equation 1 represents the output voltage when the output of the magnetic determination circuit 4 is the voltage VDD VOUT. Equation 2 represents the output voltage VOUT when the output of the magnetic determination circuit 4 is the voltage GND.

In this way, the output voltage VOUT of the magnetic sensor 1 does not depend on the resistance value of the pull-up resistor 18, and therefore will not be affected by the deviation of the pull-up resistor 18. Therefore, the value of the pull-up resistor can be flexibly set, and as a further effect, by increasing the value of the pull-up resistor, the power saving of the magnetic sensor system can also be realized.

The following shows an example of realizing the specific resistance value of the magnetic sensor 1 of the first embodiment. When the external power supply VPU is 5.0 V and the reference voltage VREF is 0.3 V, the circuit constants such that the output voltage VOUT of Equation 1 is 4.5 V and the output voltage VOUT of Equation 2 is 0.5 V are obtained. From Formula 1 and Formula 2, it can be seen that the ratio of R1:R2:R3 can be set to 7:0.5:10.

More specifically, since the resistance value of the pull-up resistor 18 is not limited, the larger the resistance value of the resistors R1 to R3, the more ideal it is. If RPU is set as the resistance value of the pull-up resistor 18, its allowable value is calculated according to Equation 3. RPU＞(VPU-VOUT(1))/{VOUT(1)/(R1+R2+R3)}...(3) For example, if R1=700 kΩ, R2=50 kΩ, R3=1 MΩ, then As long as the resistance value RPU of the pull-up resistor 18 is less than 194 kΩ, the magnetic sensor 1 can operate. More realistically, considering the allowable range of the drain current of the output drive element 6, the resistance value of the pull-up resistor 18 is desirably several tens of Ω or more.

As described above, according to the magnetic sensor 1 of the first embodiment, the input voltage of the discrimination circuit 19 is determined by the voltage division ratio of the reference voltage and the voltage divider circuit, so the resistance value of the pull-up resistor 18 is not affected. Because of the influence of deviation, it is possible to accurately determine abnormalities such as wire breakage or short circuit. In addition, it is also possible to adopt a configuration in which the resistance of the voltage divider circuit can be trimmed so that the output voltage VOUT can be adjusted based on the input voltage obtained by the discrimination circuit 19.

Fig. 2 is a circuit diagram showing a second embodiment of the magnetic sensor of the present invention. The magnetic sensor 100 includes a magnetic sensor element 3, a magnetic determination circuit 4 and an output control circuit 20. The output control circuit 20 includes an output driving element 6, an amplifier 7, resistors R1 and R2 as a voltage dividing circuit, a reference voltage circuit 81, a reference voltage circuit 82, and a MOS switch 90.

The magnetic sensor 100, the discrimination circuit 19, and the pull-up resistor 18 are connected in the same manner as in the first embodiment, and perform the same operation. Furthermore, since the magnetic sensor element 3, the magnetic determination circuit 4, the output drive element 6, and the amplifier 7 are connected in the same manner as in the first embodiment and perform the same operations, the description is omitted.

The MOS switch 90 includes, for example, a CMOS transistor, and selectively selects the reference voltage circuit 81 or the reference voltage circuit 82 and is connected to the inverting input terminal of the amplifier 7. The MOS switch 90 includes a control terminal, and the binary voltage output from the magnetic determination circuit 4 is input to the control terminal.

When the output of the magnetic determination circuit 4 is the voltage GND, the MOS switch 90 selects the reference voltage circuit 81 and connects the output terminal of the reference voltage circuit 81 to the inverting input terminal of the amplifier 7. On the other hand, when the output of the magnetic determination circuit 4 is the voltage VDD, the MOS switch 90 selects the reference voltage circuit 82 and connects the output terminal of the reference voltage circuit 82 to the inverting input terminal of the amplifier 7.

It is assumed that the reference voltage generated by the reference voltage circuit 81 is VREF1, and the reference voltage generated by the reference voltage circuit 82 is VREF2. The reference voltage VREF1 and the reference voltage VREF2 are reference voltages with different values.

Assuming that the output voltage of the output terminal OUT of the magnetic sensor 100 is VOUT, the output voltage VOUT is expressed in two formulas according to the situation of the magnetic determination result. VOUT=(1+R1/R2)×VREF1...(4) VOUT=(1+R1/R2)×VREF2...(5) Equation 4 represents the output voltage VOUT when the output of the magnetic determination circuit 4 is the voltage GND. Equation 5 represents the output voltage VOUT when the output of the magnetic determination circuit 4 is the voltage VDD.

Hereinafter, a specific numerical example for realizing the magnetic sensor 100 of the second embodiment is shown. Determine the circuit constants assuming that the external power supply VPU is 5.0 V, the output voltage VOUT of Equation 4 is 4.5 V, and the output voltage VOUT of Equation 5 is 0.5 V. When the reference voltage circuit 81 is set so that the reference voltage VREF1 becomes 3.0 V, it can be seen from Equation 4 that the ratio of R1:R2 only needs to be set to 0.5:1. Furthermore, from Equations 4 and 5, it can be seen that the reference voltage VREF2 only needs to be set to 0.33 V.

Fig. 3 is a circuit diagram showing a third embodiment of the magnetic sensor of the present invention. The magnetic sensor 200 includes a magnetic sensor element 3, a magnetic determination circuit 4 and an output control circuit 30. The reference voltage circuit is different from the second embodiment in that it includes a resistor 91, a resistor 92, and a resistor 93. Furthermore, the magnetic sensor 200 includes a VDD2 terminal connected to an external power supply VPU, and the VDD2 terminal is connected to one end of the resistor 93 and the inverting input terminal of the amplifier 7. The resistor 93 is connected to any one of the resistor 91 and the resistor 92 through the MOS switch 90. In addition, these resistors obtain the reference voltage by dividing the voltage VPU by resistors.

When the output of the magnetic determination circuit 4 is the voltage VDD, the MOS switch 90 selects the resistor 91 to be connected in series with the resistor 93. When the output of the magnetic determination circuit 4 is the voltage GND, the MOS switch 90 selects the resistor 92 to be connected in series with the resistor 93.

Assume that the reference voltage generated by the external power source VPU, the resistor 93 and the resistor 91 is VREF1, and the reference voltage generated by the external power source VPU, the resistor 93 and the resistor 92 is VREF2. The reference voltage VREF1 and the reference voltage VREF2 are reference voltages with different values. Assuming that the output voltage of the output terminal OUT of the magnetic sensor 200 is VOUT, the output voltage VOUT is expressed by Equations 4 and 5 in the same way as the magnetic sensor 100 of the second embodiment.

The following shows a specific numerical example for realizing the magnetic sensor 200 of the third embodiment. Determine the circuit constants assuming that the external power supply VPU is 5.0 V, the output voltage VOUT of Equation 4 is 4.5 V, and the output voltage VOUT of Equation 5 is 0.5 V. The ratio of the output voltage VOUT of Equation 4 to the output voltage VOUT of Equation 5 is 9:1, so the ratio of the reference voltage VREF1 to the reference voltage VREF2 is also set to 9:1. If the reference voltage VREF1 is set to 3.0 V and the reference voltage VREF2 is set to 0.33 V, it can be seen from Equation 4 that the ratio of R1:R2 only needs to be set to 0.5:1. Furthermore, with regard to the resistance 91, the resistance 92, and the resistance 93, the third embodiment can be realized by setting the resistance 91 to 300 kΩ, the resistance 92 to 14 kΩ, and the resistance 93 to 200 kΩ.

As explained above, according to the magnetic sensor of the present invention, the input voltage of the discrimination circuit 19 is determined by the voltage division ratio of the reference voltage and the voltage divider circuit, so it will not be affected by the resistance deviation of the pull-up resistor 18 , And can accurately determine abnormalities such as wiring disconnection or short circuit.

1, 50, 100, 200‧‧‧Magnetic sensor 3‧‧‧Magnetic sensor component 4‧‧‧Magnetic determination circuit 5,90‧‧‧MOS switch 6‧‧‧Output driving component 7‧‧‧Amplifier 8,81,82‧‧‧Reference voltage circuit 10,20,30‧‧‧Output control circuit 18,58‧‧‧Pull-up resistor 19,59‧‧‧Distinguishing circuit 51‧‧‧Signal processing circuit 52‧‧‧ Transistor 53‧‧‧Constant current circuit 54, 91, 92, 93, R1, R2, R3‧‧‧Resistor GND‧‧‧Voltage, ground terminal IN, VDD2‧‧‧Terminal N1, N2‧‧‧Node OUT‧ ‧‧Output terminal VDD‧‧‧Power supply terminal, voltage VPU‧‧‧External power supply terminal, external power supply

Fig. 1 is a circuit diagram showing the first embodiment of the magnetic sensor of the present invention. Fig. 2 is a circuit diagram showing a second embodiment of the magnetic sensor of the present invention. Fig. 3 is a circuit diagram showing a third embodiment of the magnetic sensor of the present invention. Fig. 4 is a circuit diagram showing a conventional magnetic sensor device.

1‧‧‧Magnetic Sensor

3‧‧‧Magnetic sensor components

4‧‧‧Magnetic determination circuit

5‧‧‧MOS switch

6‧‧‧Output drive components

7‧‧‧Amplifier

8‧‧‧Reference voltage circuit

10‧‧‧Output control circuit

18‧‧‧Pull-up resistor

19‧‧‧Distinguishing circuit

R1, R2, R3‧‧‧Resistor

GND‧‧‧Voltage, ground terminal

N1、N2‧‧‧node

OUT‧‧‧Output terminal

VDD‧‧‧Power terminal, voltage

VPU‧‧‧External power supply terminal, external power supply

Claims (3)

A magnetic sensor, wherein an output terminal connected to an input terminal of a discrimination circuit is connected to an external power supply terminal by a pull-up resistor. The magnetic sensor is characterized in that the magnetic sensor includes a magnetic sensor element A determination circuit for inputting the output voltage of the magnetic sensor element, and an output control circuit for outputting a signal of the determination circuit to the output terminal of the magnetic sensor, the output control circuit including: a first resistor , The second resistor and the third resistor are connected in series between the output terminal and the ground terminal of the magnetic sensor; the first metal oxide semiconductor transistor, the gate of the first metal oxide semiconductor transistor is connected At the output terminal of the determination circuit, the drain of the first metal oxide semiconductor transistor is connected to the contact point of the second resistor and the third resistor, and the first metal oxide semiconductor transistor The source is connected to the ground terminal; the amplifier, the inverting input terminal is connected to the output terminal of the reference voltage circuit, and the non-inverting input terminal is connected to the contact point of the first resistor and the second resistor; and a second metal An oxide semiconductor transistor, the gate of the second metal oxide semiconductor transistor is connected to the output terminal of the amplifier, and the drain of the second metal oxide semiconductor transistor is connected to the magnetic sensor Output terminal, the source of the second metal oxide semiconductor transistor is connected to the ground terminal, wherein the output control circuit uses at least two-valued voltage to connect the determination circuit The signal of is output to the output terminal of the magnetic sensor. A magnetic sensor, wherein an output terminal connected to an input terminal of a discrimination circuit is connected to an external power supply terminal by a pull-up resistor. The magnetic sensor is characterized in that the magnetic sensor includes a magnetic sensor element A determination circuit for inputting the output voltage of the magnetic sensor element, and an output control circuit for outputting a signal of the determination circuit to the output terminal of the magnetic sensor, the output control circuit including: a first resistor And a second resistor, connected in series between the output terminal and the ground terminal of the magnetic sensor; an amplifier, a non-inverting input terminal connected to the contact point of the first resistor and the second resistor; switch, control The terminal is connected to the output terminal of the determination circuit, the first input terminal is connected to the first reference voltage circuit, the second input terminal is connected to the second reference voltage circuit, and the output terminal is connected to the inverting input terminal of the amplifier; and metal An oxide semiconductor transistor, the output terminal of the amplifier is connected to the gate, the drain is connected to the output terminal of the magnetic sensor, and the source is connected to the ground terminal, wherein the output control circuit has at least two values The voltage of the determination circuit is output to the output terminal of the magnetic sensor. A magnetic sensor device, characterized by comprising: the magnetic sensor as described in item 1 or item 2 of the scope of patent application; In the discrimination circuit, the output terminal of the magnetic sensor is connected to the input terminal; and the pull-up resistor is connected between the output terminal of the magnetic sensor and the external power supply terminal.

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