JPH0690143A - Semiconductor type sensor circuit device - Google Patents

Abstract

PURPOSE:To provide the semiconductor type sensor circuit device which is sufficiently miniaturized, enables integration and stablizes the output of a comparator. CONSTITUTION:Outputs V- and V+ from a sensor mechanism 11 composed of the bridge circuit of magneto resistance elements R11-R14 are inputted to a comparator 12 and with the output of this comparator 12, transistors Q11 and Q12 are oppositely controlled. An output from a constant current circuit composed of a resistor R10 and a transistor Q10 is selected by the transistors Q11 and Q12 and respectively fed back through forward diodes D1 and D2 to inputs V-and V+ of the comparator. In an area where hysteresis is most effectively operated by the P/n joining capacity of this diode, a spike waveform is generated for further improving the hysteresis effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRE (magnetoresistive element) type vehicle speed sensor, which is integrated, for example, and in particular, a comparator to which an output signal from a bridge-connected sensor circuit is supplied. The present invention relates to a semiconductor type sensor circuit device that stabilizes the operation of the device.

[0002]

2. Description of the Related Art For example, in a vehicle speed sensor, a rotating body having magnetic poles magnetized at equal intervals is provided on an outer peripheral portion, and a magnetic sensor is installed near the peripheral portion of the rotating body. The magnetic field of each magnetic pole of the rotating body that rotates with the wheel passes close to the magnetic sensor, and a sinusoidal detection signal is detected and output corresponding to each magnetic pole. I have to. Then, the output signal from such a magnetic sensor is supplied to a comparator so that a detection signal which changes to a high level or a low level in which a cycle is set corresponding to a wheel speed is output.

FIG. 3A shows an example of a sensor circuit to which an output signal from such a magnetic sensor is supplied.
Bridge circuit composed of MR elements (magnetic sensor)
Are supplied to the negative input terminal and the positive input terminal of the comparator 31, respectively, so that the comparator 31 can obtain a pulsed output signal that changes into two levels of high level and low level. I have to.

In the sensor circuit thus constructed,
A hysteresis circuit 32 is provided to prevent malfunction of the comparator 31, and the operation of the comparator 31 is stabilized by the hysteresis circuit 32.

The hysteresis circuit 32 is provided, for example, with a power source V
Resistors R1 and R2 connected to B and a comparator
Transistor Q whose conduction is controlled according to the output from 31
It is composed of 1, and when the output of the comparator 31 is high level, the transistor Q1 is made conductive,
The hysteresis voltage set by the resistors R1 and R2 is fed back to the negative side input of the comparator 31.

In this case, the resistors R1 and R2 are:
In particular, high precision and high resistance are required, and for this reason, hybrid type resistance elements using thick film resistors are being adopted. A capacitor C1 is connected to the positive and negative input parts of the comparator 31 as a measure against disturbance noise.

FIG. 3B shows a sensor circuit in the case of integration, in which the hysteresis voltage V10 is generated by the constant current measured by the transistors Q2, Q3 and the resistors R4, R5. The voltage V10 is supplied to the negative input V- of the comparator 31. in this case,
When the transistor Q4 becomes non-conductive, the hysteresis operation may be delayed, and it may be difficult to stabilize the operation of the comparator 31, which may cause a malfunction. Therefore, a capacitor C2 is added to the output terminal portion to prevent this malfunction. Therefore, in such a sensor circuit device as shown in FIG. 3, it is difficult to sufficiently reduce the size, which further increases the cost.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and particularly pays attention to the operating speed of a hysteresis circuit, and effectively feeds back a system having a high operating speed. A semiconductor-type sensor circuit device capable of effectively maintaining operational stability in a comparator section, easily integrated, and capable of eliminating the use of a capacitor. It is the one we are trying to provide.

[0009]

A semiconductor type sensor circuit device according to the present invention comprises a comparator to which an output signal from a sensor mechanism is supplied and a constant current power source for generating a hysteresis voltage. And a first transistor and a second transistor which are connected to each other and whose conduction is controlled in response to the two-level output signals from the comparator, respectively, and correspond to respective conduction states of the first and second transistors. The generated first and second hysteresis voltages are fed back to the two inputs of the comparator via the first and second diodes, respectively, and the high level output of the comparator is used to output the first hysteresis voltage. The hysteresis voltage is fed back to the negative input of this comparator, and the low level output of the comparator is output. In the second hysteresis voltage is to be fed back to the positive input of the comparator.

[0010]

In the semiconductor type sensor circuit device thus constructed, the first and second transistors form a two-system hysteresis circuit. When the output of the comparator is high level and low level, respectively. The second or first transistor is turned on, and the constant current hysteresis voltage is fed back to the input side of the comparator via the diode. As a result, the hysteresis voltage is operated earlier than the output of the comparator, and malfunction of the comparator can be reliably prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows its circuit configuration. This circuit is used, for example, as a vehicle speed sensor, and the magnetoresistive element R11 is used.
The sensor mechanism 11 includes a bridge circuit constituted by R14. For example, the power source VB is connected to one of the bridge circuits constituting the sensor mechanism 11 and the other end is grounded. The output V- is connected to the negative side input of the comparator 12 and the output V + is positive side. Connected to input.

A hysteresis circuit 13 is connected to the comparator 12, and is provided with a constant current circuit composed of a resistor R10 connected to a power source VB and a transistor Q10, for example. First and second transistors Q11 and Q12 are provided so that the constant currents from the constant current circuit are connected to the collectors, respectively. The output Vo of the comparator 12 is provided at the base of the transistor Q11 by an inverter In or the like. Inverted and supplied, transistor Q12
The output Vo of the comparator 12 is directly supplied to the base of the.

The output from the collector of the transistor Q11 is fed to the input V- of the comparator 12 via the diode D1.
The output from the collector of the transistor Q12 is supplied to the input V + of the comparator 12 via the diode D2.
To be supplied to. And the comparator 12
Q11 and Q12 controlled by the output of
The two-system hysteresis circuit is configured by.

The operation principle of hysteresis generation in the circuit constructed as described above is such that the hysteresis current I1 is determined by, for example, the power supply voltage VB and the resistor R10, and the path through which the hysteresis current I1 flows is the transistor Q11.
And Q12.

The operation of the transistors Q11 and Q12 is governed by the output of the comparator 12,
When the output Vo of the comparator 12 is at a high level (in the state shown by A in FIG. 2A), the transistor Q12 is turned on and the transistor Q11 is set to the off state. As a result, the hysteresis current I1 flows to the ground. Further, when the output of the comparator 12 is at a low level (in the state shown by B in FIG. 2A), the transistor Q11 is turned on and the transistor Q12 is turned off. The hysteresis current I1 passes through the turned-on transistor Q11. Flows to the ground.

Looking further at the transient operation, for example, when the output of the comparator 12 is at a high level, the transistor Q12
Is on and the transistor Q11 is off, so a hysteresis voltage is generated at the input V-.

Here, when the input to the comparator 12 changes with time and the output of the comparator 12 changes to a low level, the transistor Q12 changes from on to off and the transistor Q11 changes from off to on, and the input V -Hysteresis voltage from ON to OFF, and input V
Attempts to change the hysteresis voltage of + from off to on.

Focusing on the operating speeds when the hysteresis voltage is turned on and off, and first when the hysteresis voltage is turned off, the hysteresis voltage is turned off when the transistor Q11 or Q12 is turned from the off state to the on state. It is time to become. The operating speed t1 when this transistor is turned on is "t1 = C"
It is represented by R ″, where C is the junction capacitance between the collector and emitter of the transistor, and R is the on-resistance between the collector and emitter of the transistor, which is a very small resistance value. It can be understood that the operation speed t1 at which the ON operation is performed is very fast.

Considering when the hysteresis voltage turns on, the hysteresis voltage turns on when the transistor changes from the on state to the off state.
This operating speed t2 is represented by "t2 = C.V / I1". Here, V is (the voltage of the inputs V- and V +) + (the forward voltage of the diodes D1 and D2), and since I1 is a hysteresis current, which is a relatively small current, the transistor is turned off. The operating speed t2 is inevitably slower than t1.

Therefore, in order to operate the hysteresis circuit earlier than the output of the comparator 12, the state in which the hysteresis circuit operates at a high speed, that is, the characteristic that the hysteresis voltage changes from ON to OFF is utilized. Also, by the output from the comparator 12 to select this,
The operation of the transistors Q11 and Q12 is selected.

In order to integrate and configure such a circuit device in one chip, it is necessary to set the hysteresis voltage to a constant voltage. At this time, diodes D1 and D2 are provided to prevent the reverse flow of the hysteresis current. When the hysteresis voltage changes from on to off by the diodes D1 and D2, that is, the hysteresis current is grounded. When flowing, the potential on the anode side of the diode (the voltage of the inputs V- and V +) + (the forward voltage of the diodes D1 and D2) instantly becomes the ground potential.

Therefore, at the cathode side of the diodes D1 and D2, that is, at the input of the comparator 12, the diode D
AC coupling is performed by the P / n junction capacitance of 1 and D2, and during several nanoseconds, a spike waveform larger than the hysteresis voltage is generated as shown in FIG. 2B, further enhancing the hysteresis effect. .

[0023]

As described above, according to the semiconductor type sensor circuit device of the present invention, two constant current type hysteresis circuits are provided, and the middle point of the bridge circuit constituting the sensor mechanism, that is, the input of the comparator. Feedback is provided, and two types of hysteresis circuits are selected by the comparator output. Also,
Each of the feedback circuits of the two systems of hysteresis circuits is provided with a diode for preventing backflow, and the P / n junction capacitance of the diodes causes spike waveforms to further enhance the hysteresis effect in the region where the hysteresis works most effectively. Is generated, the sensor circuit device can be integrated and easily configured, and the operation of the comparator is sufficiently stabilized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram illustrating a semiconductor sensor circuit device according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams for explaining an input voltage corresponding to an operation of a comparator for explaining the above-described embodiment. FIGS.

3A and 3B are diagrams showing examples of conventional sensor circuits.

[Explanation of symbols]

11 ... Sensor mechanism, 12 ... Comparator, 13 ... Hysteresis circuit, R11-R14 ... Magnetoresistive element, R10 ... Resistor, Q10-
Q12 ... Transistors, D1, D2 ... Diodes.

Claims (1)

[Claims] 1. A comparator to which an output signal from a sensor mechanism is supplied, a constant current power source for generating a hysteresis voltage, and a constant current power source connected to the constant current power source.
First and second transistors whose conduction is controlled corresponding to the level output signal, and first and second hysteresis voltages generated corresponding to the conduction states of the first and second transistors, respectively. Is fed back to the two inputs of the comparator, and the first hysteresis voltage is fed back to the negative side input of the comparator at the high level output of the comparator, A semiconductor type sensor circuit characterized in that the second hysteresis voltage is fed back to a positive side input of the comparator by a level output.