JPH0694772A - Binary signal detection circuit having abnormality detecting function - Google Patents

Abstract

PURPOSE:To detect trouble such as disconnection or earthing without delay. CONSTITUTION:The first resistor R11 connected to a transistor T-1 in parallel, the second resistors R22, R23 connected across an input terminal IN and earth, a first comparator CMP1 inputting the input potential Vin proportional to the potential of the input temtinal IN and first reference potential Vref1, a second comparator CMP2 inputting the input potential Vin and third reference potential Vref2 and a third comparator CMP3 inputting the input potential Vin and third reference potential Vref3 are provided. By setting the first, second and third reference potentials Vref1, Vref2, Vref3 to predetermined relation, the output level of the first comparator is changed corresponding to ON/OFF of the transistor and, in the case of earthing trouble and disconnection trouble, the outputs of the second and third comparators can be reversed and abnormality can be detected on the basis of this reversal without delay.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit having a function of detecting an abnormality of a binary signal detecting circuit provided with a sensor section and a receiving circuit separated from each other. For example, it can be applied to various detection circuits such as a steering angle detection circuit and a vehicle speed detection circuit that detect each physical quantity in a vehicle by a binary signal.

[0002]

2. Description of the Related Art Conventionally, in a four-wheel steering system, a steering angle is detected and the rear wheels are steered according to the steering angle. In this case, the sensor part is attached to the steering shaft part, the receiving circuit is arranged in the body of the vehicle in which various control devices are arranged, and the sensor part and the receiving circuit are connected by relatively long wiring. There is. The sensor unit is composed of a Hall IC, a photocoupler, and the like, and a pulse train of a binary signal is output as the steering shaft rotates, and the rotation angle is detected by counting this pulse train. In the four-wheel steering system configured as described above, it is necessary to detect the steering angle without error, and in the event of a short circuit to the power source of the wiring, grounding, disconnection, etc., immediately stop the steering of the rear wheels. Will be required.

[0003]

As described above, when the output of the steering angle sensor is abnormal, Japanese Patent Laid-Open No. 11497/1991 is available.
As described in Japanese Patent No. 3, the abnormality detection is performed when the state where the output signal level of the steering angle sensor does not continuously change for a predetermined time or longer is detected. Therefore,
There is a problem that the abnormality detection is delayed by the above-mentioned predetermined time with respect to the occurrence of the abnormality, and the fail safe is delayed.

The present invention has been made to solve the above problems, and an object thereof is to disconnect a wire or ground in a binary signal detection circuit in which a sensor section and a receiving circuit are connected by a wire. For a failure such as a short circuit to the power supply, it is to detect an abnormality without delay.

[0005]

The constitution of the present invention is as follows:
A sensor section for outputting a binary signal in response to ON / OFF of an output stage transistor having an emitter or source grounded, open collector or open drain structure, and wiring arranged between the collector or drain of the transistor and the receiving circuit. , Connect the input terminal on the receiving circuit side of the wiring to the reference power source via the load resistance, and set the potential proportional to the potential of the input terminal to 2
It is a detection circuit which has a receiving circuit which makes it a received signal of a value signal. Then, in this detection circuit, a first resistor connected between both terminals of the transistor, a second resistor connected between the input terminal and ground, an input potential proportional to the potential of the input terminal, and a first reference potential are provided. A first comparator for inputting, a second comparator for inputting an input potential and a second reference potential, and a third comparator for inputting an input potential and a third reference potential are provided. Further, the first reference potential is a potential between the input potential when the transistor is in the off state and the input potential when the transistor is in the on state, and the second reference potential is the potential when the transistor is in the on state. The third reference potential is set to a potential between the input potential and the ground potential, and the third reference potential is set to a potential between the input potential when the transistor is off and the input potential when the wiring is disconnected. Has been done. Then, the output of the first comparator is used as a normal detection signal of a binary signal, and abnormality detection is performed according to the outputs of the second and third comparators.

[0006]

When the transistor is in a normal state, the input potential is a potential (hereinafter referred to as "L level") corresponding to the voltage between the emitter or the source, the collector or the drain when the transistor is in the ON state (hereinafter referred to as "L level"), and A potential (input potential) proportional to the input terminal when in the off state,
That is, the reference power supply voltage takes a binary value of a potential (hereinafter, referred to as “H level”) proportional to a potential obtained by dividing the reference power supply voltage by the load resistance and the resistance in which the first resistance and the second resistance are connected in parallel. Since the first reference potential is set between the L level and the H level, the output level of the first comparator changes according to the on / off state of the transistor, and a normal binary signal is detected. On the other hand, since the second reference potential is set to a potential between the ground level and the L level, the output level of the second comparator does not change even if the input potential changes between the L level and the H level. Further, the third reference potential is H level and a potential proportional to the potential of the input terminal when the wiring is broken, that is, a potential proportional to the potential obtained by dividing the reference power supply voltage by the load resistor and the second resistor (hereinafter , "SH level". Since there is no shunt of the current to the first resistor, it is set to a potential between | SH level | ≧ | H level |). Therefore, the input potential is L level. And H level, the output level of the third comparator does not change. Second
And when the output of the third comparator is at the above level,
Detection of a binary signal can be considered normal.

On the other hand, when the wiring is connected to the ground,
The input potential is the ground potential. Therefore, the input potential and the second
Since the magnitude relationship of the reference potential is inverted, the output level of the second comparator is inverted. As a result, the occurrence of a failure in which the wiring is connected to the ground is immediately detected.

When the wiring is broken, the input potential becomes SH level. Therefore, the magnitude relationship between the input potential and the third reference potential is inverted, so that the output level of the third comparator is inverted. As a result, it is immediately detected that the wiring has been broken.

Furthermore, when the wiring is connected to the power supply, the input potential exceeds the SH level. Therefore, the output level of the third comparator is inverted similarly to the disconnection failure, so that the connection failure of the wiring to the power supply can be immediately
Can be detected.

[0010]

According to the present invention, a transistor having an open collector or open drain structure, a first resistor connected in parallel with the transistor, a load resistor connected between a reference power source and ground, and a second resistor are connected in series to form a load. Resistance and second
The input potential, which is proportional to the potential of the input terminal, which is the connection point with the resistor, is different from the level of the binary signal in the normal state and the potential in the case of failure such as grounding, disconnection, or short circuit to the power supply. Become. Therefore, the abnormality detection can be immediately performed by the change in the output level of the second comparator and the third comparator.

[0011]

EXAMPLES The present invention will be described below based on a specific example. FIG. 2 shows the configuration of the four-wheel steering system. In this steering device, the steering angle sensor 12 and the wheel speed sensor 1 are used.
3, output signals from the vehicle speed sensor 14 and the rear wheel steering angle sensor 15 are input to the control unit (ECU) 10. Based on these signals, the ECU 10 calculates a rear wheel steering angle command value, and the command value is output to the motor driver 11. Then, the brushless motor 16 is driven by the motor driver 11, and the rear wheels are steered according to the command value.
The four-wheel steering system is configured as described above, and each of the sensors 12, 13, 14, and 15 described above serves as the sensor unit of the binary signal detection circuit according to the present invention. The receiving circuit is present in the control device 10.

Next, the detailed structure of the binary signal detection circuit will be described with reference to FIG. The sensor unit 20 includes a Hall IC 21 that detects rotation of the shaft and an output stage transistor Tr1.
And a first resistor R11 connected in parallel with the transistor Tr,
It is composed of an output protection resistor R1. Also, the receiving circuit 3
0 is a reference power source V1 (5V), a load resistor R21, a protection diode D1, a resistor R22 and a resistor R23 which form a second resistor,
It is composed of a first comparator CMP1, a second comparator CMP2, and a third comparator CMP3. Resistance R4, R5
Is a pull-up resistor of the output of the comparator. In this embodiment, the second resistor is composed of a resistor R22 and a resistor R23 connected in series. The input terminal IN is a terminal of the wiring 40 on the receiving circuit 30 side. The potential at the connection point between the resistor R22 and the resistor R23 is an input voltage V _in, input potential V _in is in course, proportional to the potential of the input terminal IN. The resistor R22, the output protection resistor R1, and the protection diode D1 are not always necessary.
If no resistance R22 provided, the second resistor is constituted by only the resistance R23, the input potential V _in is equal to the potential of the input terminal IN.

Next, the operation of this detection circuit will be described. The input potential V _in of the receiving circuit 30 is (1) a short circuit failure of the wiring 40 to the battery, (2) a grounding failure of the wiring 40, (3) a disconnection failure of the wiring 40, and (4) a transistor Tr in a normal state.
1 OFF state, and (5) Normal transistor
It can take 5 levels depending on the ON state of Tr1. Less than,
The operation state will be described separately for the above five states.

(1) Short-circuit failure of the wiring 40 to the battery When a short-circuit failure of the wiring 40 to the battery occurs, a short-circuit current flows from battery → input terminal IN → resistor R22 → resistor R23 → ground. Therefore, the battery voltage is changed to V _BATT.
Then, the input potential V _in 1 at this time is represented by the following equation.

[ _Equation 1] V _in 1 = V _BATT · R23 / (R22 + R23)

(2) Ground fault of wiring 40 When a ground fault of the wiring 40 occurs, the potential of the input terminal IN becomes zero.
The voltage becomes V, and a current flows from the reference power source V1 → load resistance R21 → protection diode D1 → input terminal IN → wiring 40 → ground, and the input potential V _in 2 at this time becomes the ground potential. Therefore,

[Formula 2] V _in 2 = 0V

(3) Disconnection failure of the wiring 40 In the case of the disconnection failure of the wiring 40, the sensor unit 20 from the input terminal IN
Since the impedance seen is infinite, the current flows through the path of the reference power source V1, the load resistance R21, the protection diode D1, the resistance R22, the resistance R23, and the ground. When the forward voltage of the protection diode D1 is V _F , the input potential V _in 3 at the time of this failure is

## EQU3 ## V _in 3 = (V 1 −V _F ) R23 / (R21 + R22 + R23) This potential becomes the SH level of the input potential V _in .

(4) Off state of transistor Tr1 in normal state When transistor Tr1 is off, the current is the reference power source V
1 → Load resistance R21 → Protection diode D1 and flows from the protection diode D1 into two paths: protection resistance R1 → first resistance R11 → ground path and load resistance R22 → load resistance R23 → ground path. The input potential V _in 4 at this time is

[Formula 4] V _in 4 = (V 1 −V _F ) · R 23 (R 1 + R 11) /
[(R1 + R11) (R22 + R23) + R21 {(R1 + R11)
+ (R22 + R23)}]. This potential is the H level of the input potential V _in .

(5) ON state of transistor Tr1 in normal state When the transistor Tr1 is in the ON state, the current is the reference power source V
1 → load resistance R21 → protection resistance D1 and flows from the protection diode D1 into two paths: protection resistance R1 → transistor Tr1 → ground path and load resistance R22 → load resistance R23 → ground path. Input potential V at this time
_In 5, when the collector-emitter voltage when the transistor Tr1 is on is V _CE ,

[Equation 5] V _in 5 = (V1 −V _F ) · R1 · R23 / R21
(R1 + R22 + R23) + V _CE・ R23 / (R1 + R22 + R2
3) This potential is the L level of the input potential V _in .

Here, each resistance value is determined so that the magnitude relationship of the input potentials V _{in in} the above five equations is V _in 2 <V _in 5 <V _in 4 <V _in 3 <V _in 1. Furthermore, the first, second, and third comparators CMP1 to CMP3 have the first, second, and third comparators CMP1 to CMP3.
The reference potentials V _ref 1 to V _ref 3 are respectively V _in 5 <V
_ref 1 <V _in 4, V _in 2 <V _ref 2 <V _in 5, V _in 4 <
It is defined that V _ref 3 <V _in 3. Then, the reference potential V _ref 1
To the inverting input terminal of the first comparator CMP1, the second reference potential V _ref 2 to the inverting input terminal of the second comparator CMP2, and the third reference potential V _ref 3 to the third comparator CM.
It is applied to the non-inverting input terminal of P3.

In this state, the output of the first comparator CMP1 becomes L level when the transistor Tr1 is in the ON state, and becomes H level when the transistor Tr1 is in the OFF state.
Therefore, the pull-up resistor R4 connected to the output terminal of the first comparator CMP1 inputs the voltages 0V and 5V to the ECU 10 according to the on / off state of the transistor Tr1. The output of the second comparator CMP2 becomes L level when the wiring 40 has a ground fault, and becomes H level in other cases. Also, the third comparator C
The output level of MP3 becomes L level when the wire 40 has a disconnection failure and a battery short-circuit failure, and otherwise becomes H level. Since the outputs of the second comparator CMP2 and the third comparator CMP3 are connected to the same pull-up resistor R5, respectively, the output voltage of 0V is output when the wiring 40 has an abnormality such as a ground fault, a disconnection fault, or a battery short-circuit fault. The output voltage of 5 V is input to the ECU 10, and when normal, the output voltage of 5 V is input to the ECU 10.

Therefore, the ECU 10 reads the output of the first comparator CMP1 as a sensor output signal (binary signal), reads the outputs of the second and third comparators CMP2, CMP3 as a sensor abnormality detection signal, and outputs the sensor abnormality detection signal. When the voltage is 0 V, it can be considered that an abnormality has occurred in the detection circuit, and the steering of the rear wheels can be prevented from being executed depending on the sensor output signal. As described above, since the output levels of the second and third comparators CMP2 and CMP3 are inverted from 5V to 0V at the same time when the failure occurs, the abnormality detection is instantaneously performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a binary signal detection circuit having an abnormality detection function according to a specific embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a four-wheel steering system using the above detection circuit.

[Explanation of symbols]

10 ... ECU 11 ... Motor driver 12 ... Steering angle sensor 13 ... Wheel speed sensor 14 ... Vehicle speed sensor 15 ... Rear wheel steering angle sensor 20 ... Sensor unit 30 ... Reception circuit 40 ... Wiring Tr1 ... Transistor (transistor of open collector structure) R1 ... output protection resistor R11 ... first resistor R21 ... load resistor R22, R23 ... second resistor iN ... input terminal V _in ... input potential CMP1 ... first comparator CMP2 ... second comparator CMP3 ... third comparator V _ref 1 ... first Reference potential V _ref 2 ... Second reference potential V _ref 3 ... Third reference potential D1 ... Protection diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Nakamura 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor Takashi Inaba 1-1-cho, Showa-cho, Kariya city, Aichi prefecture Within the corporation

Claims (1)

[Claims] 1. A sensor unit for outputting a binary signal according to ON / OFF of an output stage transistor having an emitter or source grounded, open collector or open drain structure, and disposed between a collector or drain of the transistor and a receiving circuit. And a receiving circuit that connects an input terminal on the receiving circuit side of the wiring to a reference power source via a load resistor and uses a potential proportional to the potential of the input terminal as a reception signal of the binary signal. In the detection circuit, a first resistor connected between both terminals of the transistor, a second resistor disposed between the input terminal and ground, an input potential proportional to the potential of the input terminal, and a first reference potential. A first comparator that inputs the input potential, a second comparator that inputs the input potential and a second reference potential, and a third comparator that inputs the input potential and a third reference potential. The first reference potential is a potential between the input potential when the transistor is in the off state and the input potential when the transistor is in the on state, and the second reference potential is Is a potential between the input potential and the ground potential when the transistor is in the on state, and the third reference potential is a state in which the wiring is disconnected from the input potential when the transistor is in the off state. The potential of the first comparator is set to a potential between the input potential and the output of the first comparator as a normal detection signal of the binary signal, depending on the outputs of the second and third comparators. And a binary signal detection circuit for detecting abnormality.