JP2000132226A - Disconnection detection circuit for sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect disconnection of a sensor before a motor is rotated by converting an output waveform of a sensor into a DC voltage in accordance with the output waveform and comparing the DC voltage with a reference voltage. SOLUTION: An input A to a disconnection detection circuit 5 is inputted to a non-reversal input terminal of a comparator 8 by way of a resistor 6 and also comparison reference voltage Vcc3 from a comparison reference voltage generator 7 is inputted to a reversal input terminal of the comparator 8. The comparison reference voltage Vcc3 and the input A are compared with each other and an output C of the comparator 8 is inputted to a filter circuit 10 as a conversion circuit. Moreover, the output of the filter circuit 10 is inputted to an input terminal of a reset IC 11 as a comparison circuit and a voltage of this input terminal and the reference voltage which had inside the reset IC 11 are compared with each other. As a result, the output of the reset IC 11 becomes a resolver disconnection detection signal E and disconnection of the rotation sensor can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit for detecting disconnection of a sensor for detecting rotation of a motor or the like.

[0002]

2. Description of the Related Art Hitherto, it has been practiced to acquire rotation speed data of a motor by a sensor and to control a drive circuit of the motor based on the rotation speed data. Such control is
Since the rotation speed data is established only when the rotation speed data is correctly supplied, the rotation speed data may not be properly set, such as when the internal circuit of the sensor that detects rotation or the wiring between the sensor and the signal processing circuit of this sensor is broken. If not supplied, the motor could run away. In order to prevent this runaway, usually, an overspeed detecting means is provided separately from the sensor,
In general, when a runaway is detected by this detecting means, the motor is stopped.

[0003]

However, this conventional technique has a problem that it is not possible to detect a sensor abnormality before rotating the motor.

The present invention has been made in order to solve the above-mentioned problem, and has as its object to provide a circuit capable of detecting disconnection of a sensor before rotating a motor.

[0005]

According to a first aspect of the present invention, there is provided a conversion circuit for converting an output waveform of a sensor into a DC voltage corresponding to the output waveform, and a comparison circuit for comparing the DC voltage with a reference voltage. And a disconnection detection circuit for the sensor.

According to a second aspect of the present invention, there is provided the sensor disconnection detection circuit according to the first aspect, wherein the output of the sensor is a voltage at one end of a coil of a resolver.

According to a third aspect of the present invention, in the sensor according to the second aspect, a waveform shaping circuit for shaping an output waveform of the sensor is provided between the sensor and the conversion circuit. This is a disconnection detection circuit.

According to a fourth aspect of the present invention, there is provided the disconnection detecting circuit according to the first aspect, wherein the output of the sensor is an output of a differential output encoder.

According to a fifth aspect of the present invention, the sensor has outputs of a plurality of phases, a plurality of conversion circuits and comparison circuits corresponding to these outputs are provided, and a logic of outputs of the plurality of comparison circuits is provided. 5. The sensor disconnection detection circuit according to claim 1, wherein the sum is used as an output of the sensor disconnection detection circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a first embodiment of the present invention will be described with reference to FIG. Reference numeral 1 in the figure denotes a resolver for detecting the rotation speed or rotation angle of a motor (not shown). The resolver 1 is a kind of rotary transformer, and has a winding 1a provided therein. The resolver 1 receives A_COM, B_COM, A_COM bar, and B_COM bar, which are excitation signals of the resolver, and outputs A, B, A, and B bars that are output signals. However, only A and A_COM are shown in the figure, and B and B_CO
The M, A bar, A_COM bar, B bar, and B_COM bar have the same configuration as the A, A_COM, and thus are not shown in the drawings, and description thereof is also omitted.
The winding 1a is provided between A and A_COM.

Reference numeral 2 denotes a detection device for detecting the output signal of the resolver 1. The detection device 2 outputs the excitation signals A_COM, B_CO
The M, A_COM bar, and B_COM bar are output to the resolver 1, and the A, B, A bar, and B bar are input from the resolver 1. However, in the figure, only A and A_COM are described for the above-mentioned reasons, and the description will be made only for these.

The detection device 2 has an excitation signal generator 3, a resolver detection circuit 4, and a disconnection detection circuit 5. The excitation signal generator 3 and the resolver detection circuit 4 are conventional resolver excitation and output signal detection circuits. The excitation signal generator 3 outputs an excitation signal A_COM, and this output is input to the resolver 1. Output A of resolver 1
Are input to the resolver detection circuit 4 and the disconnection detection circuit 5.

The disconnection detecting circuit 5 is a circuit according to the present invention.
This is a circuit for detecting disconnection of the resolver. The disconnection detection circuit 5 includes a resistor 6, a comparison reference voltage generator 7, a comparator 8, a pull-up resistor 9, a filter circuit 10, a reset IC 11, and a pull-up resistor 12. The input A to the disconnection detection circuit 5 is input to the non-inverting input terminal of the comparator 8 via the resistor 6.

The comparison reference voltage generator 7 outputs the comparison reference voltage Vcc3 of the comparator 8. This comparison reference voltage Vcc3 is a voltage slightly higher than 0V. The voltage Vcc3 is input to the inverting input terminal of the comparator 8, and the voltage Vcc3 is compared with the input A. The output of the comparator 8 is an open collector output, and this output is open when the input to the non-inverting input terminal is larger than Vcc3 which is the input to the inverting input terminal. Conversely, when the input to the non-inverting input terminal is smaller, it is at the GND level. Since the output of the comparator 8 is pulled up to the power supply voltage Vcc2 via the pull-up resistor 9, when the input to the non-inverting input terminal is larger, the output potential becomes Vcc2. The output of the comparator 8 is input to the filter circuit 10.

The filter circuit 10 is a low-pass filter. The output of the filter circuit 10 is input to the input terminal of the reset IC 11. The reset IC 11 compares the voltage of the input terminal with Vcc2 / 2, which is a reference voltage inside the reset IC 11. The output of the reset IC 11 is an open collector output. As a result of the comparison, if the voltage of the input terminal is higher, the output is open. Conversely, if the voltage at the input terminal is lower, the output goes low. Since the output of the reset IC 11 is pulled up to the power supply voltage Vcc2 via the pull-up resistor 12, if the voltage of the input terminal is higher, the output voltage becomes Vcc2. The output of the reset IC 11 is a resolver disconnection detection signal E.

Although not shown, similar circuits are connected to B and B_COM, A and A_COM bars, and to B and B_COM bars. Resolver disconnection detection signals of each phase, which are outputs of these circuits, are wired OR at connection point 13.
Are combined.

Next, the operation of this embodiment will be described with reference to the waveform diagram of FIG. When the power of the detection device 2 is turned on,
A waveform shown by A_COM in FIG. 2 is output from the excitation signal generator 3 built in the detection device 2. This waveform is 0V
Is a square wave with an amplitude Vcc1 centered at. At this time, if there is no disconnection in the resolver 1 and the wiring connecting the resolver 1, the output A of the resolver 1 has a waveform centered on 0V as shown in A of FIG. This waveform is input to the non-inverting input terminal of the comparator 8 via the resistor 6.

On the other hand, the constant voltage Vcc3 output from the comparison reference voltage generator 7 is input to the non-inverting input terminal of the comparator 8. This Vcc3 is a voltage slightly higher than 0 V as described above. Accordingly, the comparator 8 outputs the waveform shown in FIG. This waveform C is GN
A square wave swinging from D to Vcc2.

The waveform C is input to the filter circuit 10, and the filter circuit 10 outputs the waveform shown in FIG.
This waveform D gradually rises when the input C of the filter circuit 10 is Vcc2, and gradually falls when the input C is GND.
Keep almost Vcc2. This waveform D is input to the reset IC 11, and the reset IC 11 outputs a resolver detection signal E. The waveform of the resolver detection signal E is shown in FIG. That is, if there is no disconnection in the resolver 1, the resolver detection signal E is constant at Vcc2.

When the resolver 1 is disconnected, the output of the resolver 1 does not have a waveform as shown in FIG.
The constant value of GND as shown in the figure. Then, the comparator 8 having input the fixed value of GND compares this input with Vcc3, and outputs the output of the comparator 8 as GN as shown at C 'in FIG.
D becomes constant. The output of the filter circuit 10 to which C 'has been input also becomes GND constant as shown at D' in FIG. The output of the reset IC 11 to which D 'has been input is GN as shown at E' in FIG.
D becomes constant. That is, if there is a disconnection in the resolver 1,
The resolver detection signal is fixed at GND.

As described above, at the connection point 13, A, B,
Since the outputs from the A-bar and B-bar phases are wired-OR connected, if the GND level is output from any of the four phases, the resolver detection signal becomes the GND level. Therefore, 4
The disconnection of any one of the phases can be detected by the resolver detection signal E.

Next, the configuration of the second embodiment of the present invention is shown in FIG.
This will be described with reference to FIG. In the present embodiment, a differential output encoder 14 is used as a sensor for detecting rotation. The encoder 14 is provided with six-phase outputs of A, B, Z, U, V, and W, but only the A phase is shown in the figure, and the other phases have the same configuration as the A phase. Description is omitted.

The encoder 14 shown in the figure is of a differential output type, and its outputs A and A output different voltage levels. That is, when A is at a high level, A
The bar becomes low level, and when A is low level, A bar becomes high level. The outputs A and A are input to the line receiver 15. A resistor 15a is connected between A and A bar. The line receiver 15 outputs an A-phase signal.

The outputs A and A of the encoder 14 are also input to the photocoupler 16. However, a resistor 16 d is provided between the A terminal of the encoder 14 and the photocoupler 16.
Is provided. Inside the photocoupler 16, two light emitting diodes 16a and 16b are connected in parallel with their directions reversed, and the outputs A and A bar of the encoder 14 are connected to both ends.

The photocoupler 16 further includes a phototransistor 16c for receiving light emitted from the light emitting diodes 16a and 16b. The emitter of the phototransistor 16c is connected to the GND potential, and the collector is the output of the photocoupler 16. This output 23 is connected to the open collector transistor 17. The output 23 is connected to the pull-up resistor 18.
Is pulled up to the power supply voltage Vcc.

The output of the open collector transistor 17 is connected to a connection point 24. Outputs from B, Z, U, V, and W phases (not shown) are also connected to the connection point 24. The connection point 18 is pulled up to the power supply voltage Vcc via a pull-up resistor 19. Further, the connection point 18 is connected to the input of the open collector transistor 20.

The output of the open collector transistor 20 is pulled up to a power supply voltage Vcc via a pull-up resistor 21. This output is output to the filter circuit 22.
Has been entered. The output of the filter circuit 22 is an encoder disconnection detection signal 25,
Connected to the input port of the PU.

Next, the operation of this embodiment will be described. If there is no disconnection or the like in the encoder 14 and it is normal, when power is supplied to the encoder 14, since the encoder is a differential output type, different levels of voltage are respectively supplied from the A and A bar terminals of the encoder 14. Is output.
These A and A bar outputs are input to the line receiver 15. The line receiver 15 outputs an A-phase signal.

The A and A bar outputs of the encoder 14 are
It is also input to the photocoupler 16. Then, one of the two light emitting diodes 16a and 16b built in the photocoupler 16 always emits light. this is,
As described above, A and A bar always have different levels of voltage.

When the light emitting diode 16a or 16b emits light, the light is received by the phototransistor 16c, and the phototransistor 16c is turned on. Then, the collector of the phototransistor 16c, that is, the output 23 of the photocoupler 16 becomes low level. This is inverted by the open collector transistor 17, and the connection point 2 which is the output of the open collector transistor 17
4 goes high.

The connection point 24 is also connected to outputs of other phases, that is, signals from B, Z, U, V, and W. If all the phases are normal, the potential of the connection point 24 becomes high level. However, if any one of the phases is disconnected and a low level is output, the potential of the connection point 24 becomes a low level.

The potential at the node 24 is input to the open collector transistor 20. This input is inverted and output. Therefore, if there is no abnormality in all phases of the encoder 14, the potential of the connection point 24 is at a high level, and the output of the open collector transistor 20 is at a low level.

This output is input to the filter circuit 22. The role of the filter circuit 22 is that when the encoder detects a disconnection during rotation of the motor, a hazard may occur due to a difference in the signal transmission speed between the A and A-bar outputs of the encoder 14. It is to remove.

Then, the output 25 of the filter circuit 22 is
The signal is a signal from which the hazard has been removed, and becomes a low level when no disconnection is detected, and becomes a high level when a disconnection is detected. This signal is input to an input port (not shown) of the CPU. The CPU detects from this input whether the encoder 14 is normal.

Next, if there is a disconnection or the like in the encoder 14, no current flows in the path between A and A bar. Then
Light-emitting diode 1 built in photocoupler 16 at the subsequent stage
A current for causing 6a or 16b to emit light cannot flow.

Then, the output of the photocoupler 16 goes high, and the output 24 of the open collector transistor 17 goes low in response to this. Further, the output of the open collector transistor 20 at the subsequent stage becomes high level. This output is removed by the filter circuit 22 if there is a hazard, and the encoder disconnection detection signal 25 output from the filter circuit 22 becomes high level.

When this output is input to the input port of the CPU, the CPU detects that the encoder 14 is disconnected, and can issue a warning or inhibit the motor from being energized. If the motor is already running, a command such as an emergency stop of the motor can be issued. In the present embodiment, the photocoupler 16
Instead, a relay may be used.

[0038]

According to the present invention, disconnection of the rotation sensor can be detected at the time when the power is supplied to the rotation sensor before the motor is rotated, and runaway of the motor can be prevented. Further, even if any phase of the rotation sensor having outputs of a plurality of phases is disconnected, the presence or absence of the disconnection can be detected by looking at one signal line, so that the disconnection can be easily detected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment.

FIG. 3 is a schematic diagram of a first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Resolver 1a Winding 2 Detector 3 Excitation signal generator 4 Resolver detection circuit 5 Disconnection detection circuit 6 Resistance 7 Comparison reference voltage generator 8 Comparator 9 Pull-up resistor 10 Filter circuit (Conversion circuit) 11 Reset IC (Comparison circuit) 12 Pull-up resistor 13 Connection point 14 Encoder 15 Line receiver 15a Resistance 16 Photocoupler 16a, 16b Light emitting diode 16c Phototransistor 16d Resistance 17 Open collector transistor 18, 19 Pullup resistor 20 Open collector transistor 21 Pullup resistor 22 Filter circuit 23 Photocoupler Output 24 Connection point 25 Encoder disconnection detection signal

Claims (5)

[Claims] 1. A disconnection detection circuit for a sensor, comprising: a conversion circuit for converting an output waveform of a sensor into a DC voltage corresponding to the output waveform; and a comparison circuit for comparing the DC voltage with a reference voltage. . 2. The sensor disconnection detection circuit according to claim 1, wherein the output of the sensor is a voltage at one end of a coil of a resolver. 3. The sensor disconnection detection circuit according to claim 2, further comprising a waveform shaping circuit that shapes an output waveform of the sensor between the sensor and the conversion circuit. 4. The disconnection detection circuit according to claim 1, wherein the output of the sensor is an output of a differential output encoder. 5. The sensor has outputs of a plurality of phases, a plurality of conversion circuits and comparison circuits corresponding to these outputs are provided, and a logical sum of outputs of the plurality of comparison circuits is detected as a disconnection of the sensor. 5. The sensor disconnection detection circuit according to claim 1, wherein the output is a circuit output.