JP2001136778A - Method and apparatus for detecting rotor position in sensorless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect a rotor position in a sensorless motor. SOLUTION: Edge-detection permission signals PA1 to PC2 are supplied to rising edge detection circuits 23A to 23C and falling edge detection circuits 24A to 24C from an edge-detection permission signal generation circuit 25. The rise-edge detection circuits 23A to 23C and the falling edge detection circuits 24A to 24C detect rise edges or fall edges of comparison signals CA to CC, only while the edge-detection permission signals PA1 to PC2 are input. The rising edge detection circuits 23A to 23C and the falling edge detection circuits 24A to 24C generate detection pulses DA1 to DC2, when the rise edges or the fall edges of the comparison signals CA to CC are supplied to an OR circuit 26, and the output of the OR circuit 26 is used as counter zero-crossing detection pulses X.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a brushless DC
The present invention relates to a method and an apparatus for detecting a rotor position of a sensorless motor such as a motor or an HB type step motor. In particular, a back electromotive force generated in an open phase of a stator winding when a motor is driven is set to a reference voltage such as a midpoint voltage. In a method and an apparatus for detecting a rotor position based on a coincident time, a time when a back electromotive voltage coincides with a reference voltage can be detected more reliably.

[0002]

2. Description of the Related Art As a technique for detecting a rotor position of a motor using a permanent magnet as a rotor, such as a brushless DC motor or an HB type step motor, conventionally, an open phase of a stator winding (non-energized phase) has been used. ) Which utilizes the back electromotive voltage generated.

That is, FIG. 7A is a waveform diagram of a voltage generated in one phase of the stator winding, and shows a portion including a period in which the phase is an open phase. While the stator winding is in the open phase, the back electromotive voltage a that increases or decreases according to the rotor position is generated even if no drive current is supplied from the inverter. By comparing the voltage b with the counter electromotive zero-cross point c where the two coincide with each other, the rotor position can be detected, and the commutation mode can be accurately switched. Note that the reference voltage b includes, for example, a midpoint voltage (1/3 of the drive power
2) can be applied.

However, a square wave spike voltage d is generated in the open phase immediately after commutation, and this spike voltage d also has a zero cross point e which coincides with the midpoint voltage at the time of its fall. There is a possibility that the commutation mode switching timing may be erroneously recognized as a back electromotive zero cross point c.

[0005] As a conventional technique for solving such a problem, as shown in FIG. 7 (b), it rises in synchronization with the switching of the commutation mode and corresponds to a time slightly longer than the width of the spike voltage d. A mask signal that falls after a predetermined time elapses is generated, and a period during which the mask signal is generated is defined as a detection inhibition period. During the detection inhibition period, a zero crossing where the voltage generated in the open phase matches the reference voltage is generated. There is a method in which the detection is prohibited so that the zero-cross point e is not erroneously detected (for example, see Japanese Patent Laid-Open No.
JP-A-122388, JP-A-6-98587, JP-A-10-28395, JP-A-10-13668
No. 3, JP-A-10-146089, etc.).

[0006]

Certainly, in the conventional technique using the mask signal as described above, if the detection inhibition period, which is the width of the mask signal, can be set to an appropriate length, A certain effect can be exhibited.

However, actually, the spike voltage d
Varies depending on the motor load, etc.,
If the detection prohibition period is too short, the possibility of erroneously detecting the zero-cross point e increases, and conversely, the detection prohibition period is increased to some extent in consideration of the maximum width of the spike voltage d. If this happens, the back electromotive zero-cross point c may be hidden by the mask signal, making it impossible to detect it.

The present invention has been made in view of the problems to be solved in the conventional technique, and erroneously causes the zero-cross point e to be counteracted without using a mask signal as described above. Provided is a method and a device for detecting a rotor position of a sensorless motor, which can reduce the possibility of detection as a zero-cross point c and can more reliably detect when the back electromotive voltage matches the reference voltage, that is, the rotor position. It is intended to be.

[0009]

In order to achieve the above object, an invention according to claim 1 is to provide a sensorless motor in which a rotor position is generated in an open phase of a stator winding when the sensorless motor is driven. In the method for detecting based on the time when the electromotive voltage matches the reference voltage, a pattern of the direction of change of the back electromotive voltage before and after the back electromotive voltage matches the reference voltage is created in advance, and the sensorless motor is used. The time when the back electromotive voltage coincides with the reference voltage is detected based on the voltage actually generated in the open phase and the pattern at the time of driving.

In order to achieve the above object, the invention according to claim 2 relates to a method in which a rotor position of a sensorless motor is set such that a back electromotive voltage generated in an open phase of a stator winding when the sensorless motor is driven is set to a reference voltage. In the detection method based on the coincidence time, counting of the number of times that the voltage generated in the open phase coincides with the reference voltage is started each time the commutation mode is switched, and based on the count value, the reverse is performed. A point in time when the electromotive voltage matches the reference voltage is detected.

According to a third aspect of the present invention, in the method for detecting a rotor position of a sensorless motor according to the second aspect of the present invention, when the count value becomes two, the back electromotive voltage becomes equal to the reference voltage. It was determined that a point of time that coincided was detected.

According to a fourth aspect of the present invention, in the method for detecting a rotor position of a sensorless motor according to any one of the first to third aspects of the present invention, the sensorless motor includes upper and lower arms of an inverter constituting a drive circuit thereof. At the same time.

In order to achieve the above object, the invention according to claim 5 relates to a method in which a rotor position of a sensorless motor is set such that a back electromotive voltage generated in an open phase of a stator winding when the sensorless motor is driven is set to a reference voltage. In a device for detecting based on the coincidence time, a voltage detecting means for detecting a voltage generated in an open phase of the sensorless motor, a voltage detected by the voltage detecting means is compared with the reference voltage, and the result is compared with a comparison signal. Comparison means, and a pattern storage means storing a pattern of the direction of change of the back electromotive voltage before and after the back electromotive voltage coincides with the reference voltage, the rising and falling time of the comparison signal, Coincidence point detection means for detecting a point in time of the change that matches the pattern as a point in time when the back electromotive voltage coincides with the reference voltage.

According to a sixth aspect of the present invention, a rotor position of a sensorless motor is determined by setting a back electromotive voltage generated in an open phase of a stator winding when the sensorless motor is driven to a reference voltage. In a device for detecting based on the coincidence time, a voltage detecting means for detecting a voltage generated in an open phase of the sensorless motor, a voltage detected by the voltage detecting means is compared with the reference voltage, and the result is compared with a comparison signal. A counting means for counting the number of rises and falls of the comparison signal from the time when the commutation mode is switched; and a countermeasure when the count value of the counting means reaches a predetermined value. Coincidence point detection means for detecting a point in time when the voltage coincides with the reference voltage.

According to a seventh aspect of the present invention, in the apparatus for detecting a rotor position of a sensorless motor according to the sixth aspect, the predetermined value is set to two.

According to an eighth aspect of the present invention, in the apparatus for detecting a rotor position of a sensorless motor according to any one of the fifth to seventh aspects, the sensorless motor comprises upper and lower arms of an inverter constituting a drive circuit thereof. At the same time.

Here, the direction of change of the back electromotive voltage a generated in the open phase of the stator winding of the sensorless motor before and after the back electromotive zero cross point c is, as shown in FIG. As shown in FIG. 7 (a), the back electromotive force approaches the reference voltage b from the high voltage side and forms a back electromotive zero-cross point c which is closer to the lower voltage side and further increases beyond the reference voltage b. A zero-cross point c is formed, and a reference voltage b
There are two types, the direction of decrease below. The pattern of the direction of the change can be predicted in advance.

The direction of the change in the spike voltage d generated in the open phase immediately after the commutation at the zero-crossing point e is as shown in FIG.
In both cases, the direction of the crossing with the reference voltage b is opposite to the direction of the crossing of the back electromotive voltage a and the reference voltage b appearing in the same open phase period. The direction is reversed.

That is, the back electromotive zero cross point c and the zero cross point e appearing within the same open phase period are the same in that they coincide with the reference voltage b, but the crossing directions with the reference voltage b are opposite to each other. There is a difference in that

Therefore, if the pattern of the direction of change of the back electromotive voltage before and after the back electromotive voltage coincides with the reference voltage is previously created as in the invention according to claim 1, when the sensorless motor is driven, The back electromotive zero cross point c is detected based on the pattern and the voltage actually generated in the open phase when the motor is driven. That is, if the direction of change when the voltage actually generated in the open phase at the time of driving the motor crosses the reference voltage b matches the direction of change of the back electromotive voltage stored in the pattern, the back electromotive zero crossing point It can be determined that c has been detected, and if they do not match, it can be determined that the zero cross point e between the spike voltage d and the reference voltage b has been detected. Note that the pattern of the direction of change in the back electromotive voltage may be created in correspondence with the commutation mode.

On the other hand, the order of appearance of the back electromotive zero-cross point c and the zero-cross point e in the same open phase period is such that the zero-cross point e appears as long as the sensorless motor is used within the allowable load range. Next, the back electromotive zero cross point c appears.

Therefore, as in the second aspect of the invention, the number of times that the voltage generated in the open phase matches the reference voltage b is counted, and based on the counted value, for example, a total as in the third aspect of the invention is calculated. When the numerical value becomes 2, the back electromotive zero cross point c
Can be determined.

Further, in the case of a sensorless motor of a type in which both upper and lower arms of an inverter constituting a drive circuit are driven by simultaneously chopping, a change in the voltage generated in the open phase is prevented. Since the waveform of the back electromotive voltage a as shown in FIG. 7A is obtained without the chopping waveform being superimposed, the effects of the first to third aspects of the present invention can be easily obtained.

On the other hand, in the invention according to claim 5, the voltage generated in the open phase of the sensorless motor is detected by the voltage detecting means, and the comparison signal is a result of comparing the detected voltage with the reference voltage. Is generated by the comparing means. For example, assuming that the comparison signal takes a logical value "1" when the detected voltage is equal to or higher than the reference voltage, and a logical value "0" when the detected voltage is lower than the reference voltage. Rises from 0 to 1 when the voltage generated in the open phase approaches and crosses the reference voltage from the low voltage side, and when the comparison signal falls from 1 to 0, the voltage generated in the open phase , And crosses from the high voltage side to approach the reference voltage.

Therefore, the coincidence point detection means matches the pattern of the direction of change of the back electromotive voltage stored in the pattern storage means, of the rise time and the fall time of the comparison signal within the same open phase period. If the time point is confirmed, the confirmed rising time point or falling time point is detected as the back electromotive zero cross point c.

Further, in the invention according to claim 6, the voltage generated in the open phase of the sensorless motor is detected by the voltage detecting means, and the comparison signal is a result of comparing the detected voltage with the reference voltage. Is generated by the comparing means. Then, the counting means counts the number of rises and falls of the comparison signal from the time when the commutation mode is switched (that is, from the time when the energized phase changes to the non-energized phase (open phase)). The comparison signal takes logical values “1” and “0”, for example, as in the case of the above example.

Since the rise and fall of the comparison signal indicate when the voltage generated in the open phase coincides with the reference voltage, the rise or fall of the comparison signal first confirmed after the commutation mode is switched. The falling is due to the zero cross point e due to the spike voltage d, and the rising or falling of the comparison signal subsequently confirmed is due to the back electromotive zero cross point c. Therefore, when the coincidence point detecting means confirms that the count value of the counting means has reached a predetermined value (for example, 2 as in the invention according to claim 7), the confirmed time point is determined as the back electromotive zero cross point c. Can be detected as

Further, in the case of a sensorless motor of a type in which both upper and lower arms of an inverter constituting a drive circuit are driven by simultaneously chopping, a change in the voltage generated in the open phase is obtained. Since the waveform of the smooth back electromotive voltage a as shown in FIG. 7A is obtained without the chopping waveform being superimposed, the effects of the inventions according to claims 5 to 7 can be easily obtained.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 shows a drive circuit 10 of a brushless motor 1 to which a rotor position detecting method and apparatus according to the present invention are applied. FIG.

First, the configuration will be described. The brushless motor 1 as a sensorless motor is a three-phase brushless motor in which three stator windings of A phase, B phase and C phase are star-connected. The drive circuit 10 has an inverter 11, and each output terminal of the inverter 11 is connected to each of the A-phase to C-phase terminals of the brushless motor 1. The inverter 11 has a known configuration in which three sets each of which connects the power supply side transistor and the ground side transistor corresponding to the A phase to the C phase are provided, and a total of six transistors included in the inverter 11 are turned on and off. Are controlled by a commutation signal supplied from the commutation signal generation circuit 12. In the present embodiment, the commutation signal generation circuit 12 drives the brushless motor 1 by simultaneously chopping the upper and lower arms of the inverter 11.

The drive circuit 10 has a commutation timing generation circuit 13 and a rotor position detection circuit 20 in addition to the inverter 11 and the commutation signal generation circuit 12.

Of these, the rotor position detecting circuit 20
Is have three comparators 21A, 21B and 21C, to the inverting input terminal of the comparators 21A~21C is input a reference voltage V ₀ from the power source 22, the brushless motor 1 to the non-inverting input terminal of the comparator 21A is the a-phase terminal voltage V _a input, to a non-inverting input terminal of the comparator 21B is input terminal voltage V _B of the B-phase of the brushless motor 1, C of the brushless motor 1 to the non-inverting input terminal of the comparator 21C The phase terminal voltage V _C is input. The reference voltage V ₀ generated by the power supply 22 is supplied from the inverter 11 to the brushless motor 1.
Of the drive power supply voltage supplied to the power supply.

The outputs of the comparators 21A to 21C are comparison signals C _A , C _B , and C _C , respectively. The comparison signal C _A is input to a rising edge detection circuit 23A and a falling edge detection circuit 24A. Signal C _B
Is input to the rising edge detection circuit 23B and the falling edge detection circuit 24B, and the comparison signal C _C is input to the rising edge detection circuit 23C and the falling edge detection circuit 24C.

The rotor position detection circuit 20 has an edge detection permission signal generation circuit 25. The edge detection permission signal generation circuit 25 outputs a rising edge detection circuit 2
3A to 23C and falling edge detection circuit 24A to 2
4C, the edge detection permission signals PA ₁ , PA
_{2, PB 1, PB 2,} PC 1, PC 2 is, have to be supplied at a predetermined timing, the rising edge detection circuit 23A~23C and falling edge detection circuit 24A~24C are logic itself Edge detection permission signals PA ₁ , PA ₂ , PB ₁ , PB ₂ , PC ₁ , P
Only while the C ₂ is input, the comparison signal C _A being fed, C _B, and detects the rising edge or falling edge of the C _C.

Then, each rising edge detection circuit 23
A to 23C and falling edge detection circuits 24A to 24
When detecting the rising edge or the falling edge of the supplied comparison signals C _A , C _B , C _C , the detection pulse DA ₁ , DA ₂ , DB ₁ ,
Generate DB ₂ , DC ₁ , DC ₂ ,
The detection pulses DA _{1 to} DC ₂ are supplied to the commutation signal generation circuit 12.

Further, the rotor position detection circuit 20
Have a circuit 26, the detection pulse DA ₁ to DC ₂ are supplied to the OR circuit 26. The output of the OR circuit 26 is a back electromotive zero cross detection pulse X, and the back electromotive zero cross detection pulse X is
It is supplied to the commutation timing generation circuit 13 and the edge detection permission signal generation circuit 25.

The commutation timing generation circuit 13 determines the next commutation timing based on the back electromotive zero-crossing detection pulse X, and sends the timing signal to the commutation signal generation circuit 12 when the determined commutation timing is reached. Supply T. The commutation signal generation circuit 12 receiving the timing signal T changes the commutation signal to the inverter 11 so as to switch the commutation mode in synchronization with the timing signal T. In the case of the present embodiment, since the three-phase brushless motor 1 is used, there are six commutation modes. If the driving of the brushless motor 1 is normally performed, the commutation modes are sequentially changed. Should be switched to

The commutation signal generation circuit 12 turns on / off each transistor in the inverter 11 according to the determined commutation mode, while the edge detection permission signal generation circuit 25 sends the determined commutation to the edge detection permission signal generation circuit 25. A commutation mode signal M indicating the mode is supplied.

Therefore, the edge detection permission signal generation circuit 25
Are supplied with a commutation mode signal M and a back electromotive zero-cross detection pulse X. The edge detection permission signal generation circuit 25 determines the rising edge detection circuits 23A to 23A to 23C based on those signals. 23C and one of the falling edge detection circuits 24A to 24C which permits edge detection is determined, and edge detection permission signals PA _{1 to} PC ₂ having a logical value “1” are supplied to the determined circuit. , Other rising edge detection circuits 23A to 23A
The C and falling edge detection circuits 24A to 24C are supplied with edge detection permission signals PA _{1 to} PC ₂ having a logical value “0”.

More specifically, the edge detection permission signal generation circuit 25 determines which of the phases A to C is the open phase in accordance with the commutation mode, and determines whether the open phase corresponds to the open phase. It stores a pattern of the direction in which the appearing back electromotive voltage crosses the reference voltage V _{0 from} which direction, and every time the commutation mode represented by the commutation mode signal M is switched, the pattern is switched. The pattern is searched according to the changed commutation mode, the phase and the direction of change are recognized, and the recognized phase and change of the recognized one of the rising edge detection circuits 23A to 23C and the falling edge detection circuits 24A to 24C are detected. A circuit corresponding to the direction is determined, and an edge detection permission signal PA _{1 having a} logical value “1” is determined for the determined circuit.
Outputs to PC _2, when the new counter electromotive zero cross detection pulse X is input after the output edge detection permission signal PA ₁ to PC ₂ the logic value which has been output by the logical value "1""0".

Next, the operation of the present embodiment will be described with reference to FIG. 2, which is a waveform diagram of voltages and signals at various parts in the circuit shown in FIG.

FIGS. 2A to 2C respectively show the voltage V
_A, a waveform diagram of V _B and V _C, since the brushless motor 1 is a three-phase, as is known, 6 (= 3 × 2) state of the street be switched by an electrical angle of every 60 degrees It has become. Each voltage V _A ~V _C, as described with FIG. 7, a period in which an open phase (e.g., if the voltage V _A, 60 to 120 degrees, 240 to 300 degrees, 420-48
(0 degree, 600 to 660 degree period), the back electromotive voltage is generated, the voltage increases or decreases obliquely, and a spike voltage appears immediately after the open phase.

Then, as shown in FIGS. 2A to 2C, the reference voltage V _{0 which} is の of the drive power supply voltage is substantially at the center of the fluctuation range of each of the voltages V _{A to} V _C. , the reference voltage V ₀ will intersect each voltage V _a ~V _C and three times during the opening phase period. That is, the first crossing is a crossing when the spike voltage rises, the second crossing is a crossing when the spike voltage falls, and the third crossing has the back electromotive voltage obliquely increasing or It is an intersection by decreasing.

At the time when these intersections occur, the voltages V _A to V _A
Since the magnitude relationship between V _C and the reference voltage V ₀ is switched, the comparators 21A to 21F are synchronized with the magnitude relationship being switched as shown in FIGS.
The comparison signals C _A , C _B , and C _C , which are the outputs of 1C, change from the logical value “0” to “1” or from “1” to “0”.

On the other hand, since there are six commutation modes of the three-phase brushless motor 1, if the six commutation modes are numbered from 0 to 5, each commutation mode is shown in FIG.
As shown in (g), 0 → 1 → 2 → 3 every 60 electrical degrees.
→ 4 → 5 → 0... Then, the open phase and the direction of the change of the back electromotive voltage are determined for each of the six commutation modes, and the symbols are as shown in FIG. 2 (h). That is, the symbols A to C shown in FIG. 2H represent open phases, and the arrow on the right side thereof indicates the direction of change of the back electromotive voltage. For example, a symbol “A ↑” is drawn in a period of 60 to 120 electrical degrees, which indicates that the phase A is open and the back electromotive force changes in the increasing direction. ing.

The information shown by the symbols in FIG.
Edge detection permission signal generation circuit 2
5, the edge detection permission signal generation time
Edge detection permission signal PA output from path 25₁ ~ PC
_Two Are as shown in FIGS. 2 (i) to 2 (m). For example,
In the period of the electrical angle of 60 degrees to 120 degrees, it is shown in FIG.
The commutation mode is “4” as shown in FIG.
Open phase is A phase and back electromotive voltage changes in the increasing direction
The back electromotive force changes in the increasing direction.
Is the voltage V_A And reference voltage V₀ And the magnitude relationship with "V_A <
V₀ "To" V _A > V₀ Want to detect when it changes to
Since this is a back electromotive zero crossing point, the comparison signal C_A Is a logical value
At the point when “0” changes to “1”, that is, the comparison signal C_A 
Is to be detected.

Therefore, the edge detection permission signal generation circuit 25
Is the rising edge detection time at the electrical angle of 60 degrees.
An edge detection permission signal P having a logical value "1"
A₁Is output. Therefore, the rising edge detection
The output circuit 23A outputs the comparison signal C _A Rising edge only
And the detection pulse DA₁ Is output. The electrical angle
Even at 60 degrees due to the rise of spike voltage
Comparison signal C_A There is a rising edge of
The rising edge is generated in synchronization with the commutation mode switching time.
The edge detection permission signal PA
₁ Stands after it is confirmed that the commutation mode has switched.
Since it is a rising signal, the circuit of FIG.
Signal C caused by the rise of the clock voltage_A The rise of
Detection edge DA₁ Output
There is no such thing.

[0049] When the detection pulse DA ₁ is output, as shown in FIG. 2 (u), the back electromotive zero cross detection pulse X is also one generated, the counter electromotive zero cross detection pulse X edge detection permission signal since also supplied to the generator 25, in synchronism with the counter electromotive zero cross detection pulse X output of the edge detection permission signal PA ₁ is stopped.

In the above description, the commutation mode is “4”.
Although was performed taking the case of the example, because there is a similar effect in other commutation mode, as shown in FIG. 2 (u), each time the counter electromotive voltage generated in the opening phase crosses the reference voltage V ₀ , The back electromotive zero-cross detection pulses X are generated one by one.

The back electromotive zero cross detection pulse X is
Since it is also supplied to the commutation timing generation circuit 13, the commutation timing generation circuit 13 outputs a timing signal T in synchronization with the commutation timing.
The commutation signal generation circuit 12 that has received the signal outputs a commutation signal to the inverter 11 in synchronization with the timing signal T, and supplies a commutation mode signal M to the edge detection permission signal generation circuit 25.

As a result, the transistors in the inverter 11 are switched at an appropriate timing, so that the brushless motor 1 is driven normally and the edge detection permission signal generation circuit 25 supports the commutation mode after the switching. Then, new edge detection permission signals PA _{1 to} PC ₂ are output.

As described above, in the present embodiment, a pattern in the direction of the intersection between the back electromotive voltage generated in the open phase and the reference voltage is created in advance, and the reverse direction is determined based on the pattern in the direction of the change. Since the circuit configuration detects the back electromotive zero crossing point where the electromotive voltage and the reference voltage cross, the possibility of erroneously detecting the point where the spike voltage crosses the reference voltage as the back electromotive zero crossing point can be reduced, and the brushless motor can be reduced. 1 can be driven normally.

Unlike the prior art in which the detection prohibition period is set to cope with the above problem, the point where the load of the brushless motor 1 becomes large and the spike voltage and the reference voltage cross each other is a back electromotive zero crossing point. , The backlash zero-cross point can be reliably detected, so that the operating range of the brushless motor 1 can be expanded, and the stability can be improved even with a sudden load change. There is.

In this embodiment, each of the A to C phase terminals of the brushless motor 1 and the comparator 21A
21C correspond to the voltage detecting means, the comparators 21A to 21C correspond to the comparing means, the edge detection permission signal generating circuit 25 corresponds to the pattern storing means, and the rising edge corresponds to the rising edge. Detection circuit 23A
To 23C, the falling edge detection circuits 24A to 24C and the OR circuit 26 constitute a coincidence point detection means.

FIGS. 3 and 4 are views showing a second embodiment of the present invention. Of these, FIG. 3 is a circuit diagram showing a partial configuration example of the edge detection permission signal generation circuit 25 is a circuit diagram of a portion for generating an edge detection permission signal PA ₁ with respect to the rising edge detection circuit 23A. Since the overall configuration of the brushless motor 1 and the drive circuit 10 is the same as that of the first embodiment, its illustration and description are omitted, and the other edge detection permission signal PA
_Since the configuration of the portion for generating ₂ to PC ₂ is the same as the configuration shown in FIG. 3, its illustration and description are omitted.

That is, the part of the edge detection permission signal generation circuit 25 that generates the edge detection permission signal PA ₁ is composed of four flip-flops 31, 32, 33 and 34.
, An AND circuit 35, and a reset / set-type flip-flop 36. The commutation mode signal M is "4" at the input D of the first-stage flip-flop 31.
During this period, the signal S1 that is set to the logical value “1” is input, the output Q of the first-stage flip-flop 31 is connected to the input D of the second-stage flip-flop 32, The output Q of the second-stage flip-flop 32 is connected to the input D of the third-stage flip-flop 33, and the output Q of the third-stage flip-flop 33 is connected to the input D of the fourth-stage flip-flop 34. Connected to the fourth
The output Q # on the inversion side of the flip-flop 34 at the stage is one input of the AND circuit 35. The signal output from the output Q of the first-stage flip-flop 31 is referred to as an output Q1, and the signal output from the output Q of the second-stage flip-flop 32 is referred to as an output Q2. Also, the signal S1
Is an internal signal generated in the edge detection permission signal generation circuit 25 in accordance with the commutation mode signal M.
For circuit portion for generating an edge detection permission signal PA ₂ of the edge detection permission signal generation circuit 25, the signal S2 commutation mode signal M is set to a logic value "1" only during "1" Is to be supplied.

Then, the second-stage flip-flop 32
Is the other input of the AND circuit 35,
The set pulse SET output from the AND circuit 35 is supplied to the set input S of the flip-flop 36. Reset input R of flip-flop 36
, A back electromotive zero cross detection pulse X is input.

On the other hand, the edge detection permission signal generation circuit 2
5, two types of clock signals CLK1 and CLK2
Is used, and one clock signal C
LK1 is a relatively high-frequency clock signal as shown in FIG. 4C, which is supplied to the clock input terminals of the third-stage flip-flop 33 and the fourth-stage flip-flop. ing. On the other hand, the clock signal CLK2 is a basic clock for generating a PWM signal used for controlling the rotation speed of the brushless motor 1 as shown in FIG. 31 and the second stage flip-flop 3
2 clock input terminals.

FIGS. 4A to 4J are waveform diagrams of respective signals, and FIG. 4A is a waveform diagram in which the period of the open phase of the voltage _VA is enlarged. An initial zero cross point c, a spike voltage d and a zero cross point e are recognized. In this case, the comparison signal C _A becomes as shown in FIG. 4B, and a falling edge corresponding to the zero cross point e and a rising edge corresponding to the back electromotive zero cross point c are recognized.

As shown in FIG. 4E, the signal S1 has a logical value "1" during the open phase period and a logical value "0" during the other periods, so that the signal S1 is input. As shown in FIG. 4F, the output Q1 from the flip-flop 31 rises in synchronization with the first rise of the clock signal CLK2 after the rise of the signal S1, and the output Q2 from the flip-flop 32 As shown in (g), it rises further from the output Q1 by one cycle of the clock signal CLK2.

Then, the set pulse SET output from the AND circuit 35 is output from the output Q2 as shown in FIG.
It rises in synchronization with the rise of. However, the output Q # on the inverting side of the flip-flop 34 has the logical value "1" when the output Q2 rises, but falls after two cycles of the clock signal CLK1 from the rise of the output Q2. The logical value returns to “0” in synchronization with the fall.

Therefore, as shown in FIG. 4H, the set pulse SET rises at a point in time that is delayed from the rising point of the signal S1 by one or more cycles and less than two cycles from the rising point of the signal S1, and from the rising point of time. The pulse falls when two clock periods of the clock signal CLK1 elapse.

When such a set pulse SET is generated, the edge detection permission signal PA ₁ output from the flip-flop 36 rises in synchronization with the set pulse SET as shown in FIG. The signal falls in synchronization with the rising edge of the zero-crossing detection pulse X.

Therefore, if the configuration of the present embodiment is adopted, the edge detection permission signal PA ₁ is delayed by about 1 to 2 cycles of the clock signal CLK 2 from the switching point of the commutation mode at the rising point of the signal S _1. , The timing at which the edge detection by the rising edge detection circuit 23A is permitted is slightly delayed from the commutation mode switching time.

Therefore, the spike voltage d and the reference voltage V ₀
4 (point f in FIG. 4A) can be greatly reduced in the possibility of being erroneously recognized as the back electromotive zero cross point c. Such advantage is that if a filter or the like for removing high-frequency noise is interposed wirings for supplying to the comparator 21A~21C detects the voltage V _A ~V _B, is particularly beneficial. That is, when such a filter is interposed, an effect that high-frequency noise can be removed is obtained, but the voltage V applied to the comparators 21A to 21C is obtained.
_{Since A} ~V _B input is delayed, depending on the delay amount, the first crossing of after rises edge detection permission signal PA ₁ to the rising edge detection circuit 23A or the like, a spike voltage d and the reference voltage V ₀ ( In FIG. 4A, a point f) appears, and the intersection may be erroneously recognized as the back electromotive zero cross point c.

[0067] In the present embodiment, since the flip-flop 32 the number of stages of the previous flip-flop for generating an output Q2 is set to 2, the rise time of the edge detection permission signal PA _1, a clock signal from the rising time of the signal S1 This can be delayed by about one or two cycles of CLK2. Therefore, it is desirable to appropriately select the number of stages of the flip-flops before the flip-flop 32 that generates the output Q2 according to the delay time of the high-frequency noise removing filter.

Since the overall operation and effect are the same as those of the first embodiment, the duplicated description will be omitted.

FIGS. 5 and 6 show a third embodiment of the present invention. FIG. 5 shows a drive circuit 10 for the brushless motor 1 as in FIG. 1 in the first embodiment. It is a circuit diagram. The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

That is, in the present embodiment, as in the other embodiments, the back electromotive voltage generated in the open phase of the stator winding matches the reference voltage V ₀ . The rotor position of the brushless motor 1 is detected, and the configuration of the rotor position detection circuit 20 included in the drive circuit 10 has many common features.

However, the rotor position detection circuit 20 according to the present embodiment includes three second edge detection circuits 40A and 40B.
And have a 40C, these two shot th edge detection circuit 40A to 40C, the comparison signal C _A -C _C from comparator 21A~21C are to be supplied.

Then, the second edge detection circuits 40A to 40A-4
0C is supplied with edge detection permission signals PA to PC from the edge detection permission signal generation circuit 25. The edge detection permission signals PA to PC become logic value "1" for the second edge detection circuits 40A to 40C corresponding to the phase determined to be the open phase based on the commutation mode signal M, and become the logic value "1" for the other. Is a signal having a logical value “0”,
2 shot eyes edge detection circuit 40A~40C are starting from the time when the edge detection permission signal PA~PC rises counts the rising edge and falling edge of the comparison signal C _A -C _C, to the count value is 2 At this point, detection pulses DA, DB, and DC having extremely short periods are output. The detection pulses DA to DC are supplied to the commutation signal generation circuit 12 and the OR circuit 26.

Here, as already described with reference to FIG. 7, during the period of the open phase, the zero-cross point e generated at the end of the spike voltage d and the change of the back electromotive voltage a occur. there is a counter electromotive zero crossing point c, which is manifested as a rising or falling edge of the comparison signal C _a -C _C. However, the order of appearance of the zero-cross point e and the counter-emergence zero-cross point c in the same open period is determined, and the zero-cross point e always appears first within a range where the brushless motor 1 is operating normally. Next, the back electromotive zero cross point c appears. Therefore, by providing the second edge detection circuits 40A to 40C as in the present embodiment, it is possible to generate the back electromotive zero cross detection pulse X synchronized with the back electromotive zero cross point c.

FIG. 6 is a flowchart showing the outline of the operation of the present embodiment, and shows the outline of the processing from one commutation timing to the next commutation timing.

That is, when the commutation mode is switched, the process first proceeds to step 101, where the second edge detection circuits 40A to 40C are permitted to detect the edges of the comparison signals C _{A to} C _C. The edge detection permission signal P
The determination is made based on A to PC, and if it is determined that the permission is permitted, the process proceeds to step 102 and the first edge detection is performed. When the first edge is detected in step 102, it is the edge corresponding to the zero-cross point e, so that the detection pulses DA to DC
Is not generated, and the routine goes to step 103.

After proceeding to step 103, this time, 2
The second edge detection is performed. If the first edge is detected in step 103, since it is the edge corresponding to the back electromotive zero cross point c, the process proceeds to step 104, where the detection pulse DA, DB or DC is output. Thus, the back electromotive zero-cross detection pulse X is output.

Next, the routine proceeds to step 105, where the detection of the edges of the comparison signals C _{A to} C _C is prohibited, and step 106 is executed.
And waits until the next commutation timing. When the next commutation timing comes, the process returns to step 101 to repeatedly execute the above processing.

As described above, in the present embodiment, the comparison signals C _A to _C C from the point at which the commutation mode is switched.
Is counted, and the counter electromotive zero-crossing detection pulse X is generated in synchronization with the time when the counted value becomes 2 as a predetermined value.
Similarly to the embodiment, the possibility that the point where the spike voltage and the reference voltage intersect can be erroneously detected as the back electromotive zero-cross point can be reduced, and the brushless motor 1 can be normally driven. Even when the point at which the spike voltage and the reference voltage cross each other due to an increase in the load becomes extremely close to the back electromotive zero cross point, the back electro zero cross point can be reliably detected, so that the operating range of the brushless motor 1 is expanded. Therefore, there is an advantage that stability is improved even with a sudden load change.

In this embodiment, each of the A to C phase terminals of the brushless motor 1 and the comparator 21A
21C correspond to the voltage detecting means, the comparators 21A to 21C correspond to the comparing means, and the processing of steps 102 and 103 of the second edge detecting circuits 40A to 40C. Corresponds to the counting means, and the part of the second edge detection circuits 40A to 40C in which the processing of step 103 becomes "YES" and the processing proceeds to step 104 and the OR circuit 26 constitute the coincidence point detection means. Have been.

Incidentally, even in the third embodiment,
The configuration of the edge detection permission signal generation circuit 25 can be configured as in the second embodiment.

In the third embodiment,
Although a 2 a predetermined value, it is not limited thereto, for example, by detecting the voltage V _A ~V _B Comparator 2
Since a filter for removing high-frequency noise and the like are interposed in the wiring for supplying to 1A to 21C, the comparator 21
If the edge due to the first crossing of the voltage V _A ~V _B input is delayed by the spike voltage with the reference voltage V ₀ which to A~21C also that would be detected as an edge in the opening period, the back electromotive Since the zero-cross point c corresponds to the third edge, the predetermined value may be set to 3.

In each of the above embodiments, the reference voltage V ₀ is set to 駆 動 of the driving power supply voltage. However, any other voltage may be used as long as it is clear that the voltage crosses the back electromotive voltage. I do not care.

In each of the above embodiments, the rotor position detection circuit 20 is shown as a circuit configuration. However, the present invention is not limited to this. It is also possible to realize.

[0084]

As described above, according to the present invention,
The time when the back electromotive voltage matches the reference voltage based on the direction of change of the back electromotive voltage before and after the back electromotive voltage crosses the reference voltage or the order of appearance of edges caused by the crossing of the back electromotive voltage and the reference voltage. Is detected, it is possible to reduce the possibility of erroneously detecting a point where the spike voltage and the reference voltage intersect as a point in time when the back electromotive voltage matches the reference voltage.
Therefore, there is an effect that the rotor position of the sensorless motor can be detected more reliably.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a first embodiment.

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

FIG. 3 is a circuit diagram showing a main part of a second embodiment.

FIG. 4 is a waveform chart for explaining the operation of the second embodiment.

FIG. 5 is a circuit diagram showing a configuration of a third embodiment.

FIG. 6 is a flowchart illustrating the operation of the third embodiment.

FIG. 7 is a waveform diagram illustrating a conventional problem.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Brushless motor (sensorless motor) 10 Rotor position detection circuit 11 Inverter 12 Commutation signal generation circuit 13 Commutation timing generation circuit 21A-21C Comparator (comparison means) 23A-23C Rising edge detection circuit 24A-24C Falling edge detection circuit 25 edge detection permission signal generation circuit (pattern storage means) 26 OR circuit 40A-40C 2nd edge detection circuit

Claims (8)

[Claims] 1. A method for detecting a rotor position of a sensorless motor based on a point in time when a back electromotive voltage generated in an open phase of a stator winding when the sensorless motor is driven matches a reference voltage. A pattern in the direction of the change in the back electromotive voltage before and after the voltage matches the reference voltage is created in advance, and based on the voltage and the pattern actually generated in the open phase when the sensorless motor is driven, A method for detecting a rotor position of a sensorless motor, comprising detecting a point in time when the back electromotive voltage matches the reference voltage. 2. A method for detecting a rotor position of a sensorless motor based on a time when a back electromotive force generated in an open phase of a stator winding when the sensorless motor is driven matches a reference voltage. Counting each time the commutation mode is switched, and detecting when the back electromotive voltage matches the reference voltage based on the count value. A method for detecting a rotor position of a sensorless motor, comprising: 3. The method according to claim 2, wherein when the count value becomes 2, it is determined that a point in time when the back electromotive voltage matches the reference voltage is detected. 4. The sensorless motor rotor according to claim 1, wherein said sensorless motor is driven by simultaneously chopping upper and lower arms of an inverter constituting a drive circuit thereof. Position detection method. 5. An apparatus for detecting a rotor position of a sensorless motor based on a time when a back electromotive voltage generated in an open phase of a stator winding at the time of driving the sensorless motor coincides with a reference voltage. Voltage detecting means for detecting a voltage generated in the open phase of the voltage detecting means, comparing means for comparing the voltage detected by the voltage detecting means with the reference voltage, and using the result as a comparison signal; And a pattern storage means storing a pattern of the direction of change of the back electromotive voltage before and after the match, and the back electromotive voltage determines the time of the change that matches the pattern among the rising time and the falling time of the comparison signal. A rotor position detecting device for a sensorless motor, comprising: a coincidence point detecting means for detecting a point in time coincident with a reference voltage. 6. An apparatus for detecting a rotor position of a sensorless motor based on a point in time when a back electromotive voltage generated in an open phase of a stator winding when the sensorless motor is driven coincides with a reference voltage. Voltage detecting means for detecting a voltage generated in the open phase of the comparator, a comparing means for comparing the voltage detected by the voltage detecting means with the reference voltage and using the result as a comparison signal, and a time when the commutation mode is switched Counting means for counting the number of times of rise and fall of the comparison signal from the counter, and a coincidence point for detecting a point in time when the count value of the counter reaches a predetermined value as a point in time when the back electromotive voltage coincides with the reference voltage. A rotor position detecting device for a sensorless motor, comprising: detecting means. 7. The apparatus according to claim 6, wherein the predetermined value is two. 8. The sensorless motor rotor according to claim 5, wherein said sensorless motor is driven by simultaneously chopping upper and lower arms of an inverter constituting a drive circuit thereof. Position detection device.