JPH1175396A - Position sensorless motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent step-out and stably drive by performing commutation always at the optimum timing, by determining a quantity of delay in an electrical angle required for delaying a commutation pulse up to an optimum commutation point depending upon the peak value in a detected current. SOLUTION: In order to cancel a lead phase deviations generated in rotor position signals X, Y, Z due to a distortion occurring in a terminal voltage integration waveform of a motor 1, a current flowing to a stator winding accompanied with the rotation of a rotor or a current flowing out from the stator winding is detected as a current value equivalent to the detected value. The detected current is converted into digital values by A/D converter 6 and the peak value (peak-to-peak) of a current waveform is retained by a peak hold circuit 7. From the detected current value of the peak of current waveform, the quantity of delay d of electrical angle corresponding to the current waveform is determined from a leading angle adjusting circuit 8, and the quantity of delay d in electrical angle reflecting to the commutation timing is actually determined and output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates an optimal excitation timing for preventing step-out in a wide rotation range and driving stably when a stepping motor or a DC brushless motor is driven without a position sensor. The present invention relates to a motor drive device.

[0002]

2. Description of the Related Art In recent years, brushless DC motors used in various devices because of their high efficiency and good controllability have been driven without using a position detector such as a Hall element because of the need for miniaturization. Research and development of position sensorless drive technology that performs On the other hand, even in a stepping motor that can perform accurate positioning control in an open loop,
In order to avoid step-out, closed-loop control is required in which the position of the rotor is detected using a sensor such as an encoder, and the stator windings are excited at an optimal timing according to the rotational situation. In addition, taking advantage of the low cost of the stepping motor, the stepping motor may be positively used in applications where a brushless DC motor has been used conventionally. In such a case, closed-loop control using the above-described sensor is required. Again, the use of an external sensor for closed-loop control hinders downsizing of the device, and the increased cost of the additional sensor makes it impossible to take advantage of the low cost of the stepping motor. Would. Therefore, in applications where small size and low cost are required as described above, the position sensorless drive is also used in recent years for the closed loop control of the stepping motor.

Conventionally, in order to perform position sensorless driving, a configuration has been adopted in which the position of the rotor is detected from terminal voltages of the respective phases of the motor, commutated to the stator windings, and driven. Hereinafter, an example of the conventional position sensorless driving device will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a case where the conventional position sensorless motor drive device is applied to a position sensorless drive of a three-phase stepping motor. The conventional position sensorless motor drive device includes an inverter 2, a rotor position detection circuit. 3, a commutation signal generation circuit 9 and a drive signal generation circuit 10. 1 is a three-phase stepping motor in which three-phase stator windings are connected in a Y-shape, L
a, Lb, and Lc are A-phase, B-phase, and C-phase stator windings of the three-phase stepping motor, and inverter 2 is a stator winding of the three-phase stepping motor 1 via output terminals Da, Db, and Dc. The current is commutated to the lines La, Lb, and Lc, and the rotor is rotationally driven. Output terminal voltages Da and D of inverter 2
From b, Dc, that is, the motor terminal voltage, the rotor position detection circuit 3 generates rotor position signals X ', Y', Z 'representing the positional relationship of the rotor with respect to each of the phases A, B, C. Then, based on the rotor position signals X ', Y', Z ', the commutation signals AP to C
N is generated, and the inverter 2 is controlled via the drive signal generation circuit 10.

FIG. 2 is a circuit diagram of one phase of the rotor position detecting circuit 3. As shown in FIG. The rotor position detection circuit is composed of the filter 21,
It comprises an integrator 22, a comparator 23, and a photocoupler 24. FIG. 3 shows the terminal voltage waveforms 35, 36, and 37 of the phases A, B, and C of the three-phase stepping motor 1 of FIG. 1, and the waveforms 38, 3 obtained by integrating the terminal voltages 35, 36, and 37, respectively.
9 and 40 and the relationship between the waveforms of the rotor position signals X ', Y' and Z '. FIG. 4 shows the generation of the rotor position signals X', Y 'and Z' from the motor terminal voltage. FIG. 5 is a diagram for explaining the mechanism, and FIG. 5 shows the rotor position signal waveforms X ', Y',
It is a figure showing relation between Z 'and commutation signal waveforms AP-CN. The rotor position detection and commutation mechanism of the above-described conventional position sensorless motor driving device will be described below with reference to FIGS. 2, 3, 4, and 5, taking the A phase as an example.

The motor terminal voltage waveform 35 appearing at the inverter output terminal Da is integrated by the integrator 22 after the DC component is cut through the filter 21. The waveform after integration is as shown by 38 in FIG. 3 or FIG. The comparator 23 compares the integrated waveform 38 with the reference voltage Vref, and outputs a positive voltage if the integrated waveform voltage is larger than the reference voltage Vref, and outputs a negative voltage if the integrated waveform voltage is smaller than the reference voltage Vref. At a certain point, the output voltage switches between positive and negative. The rise from the negative voltage to the positive voltage or the fall from the positive voltage to the negative voltage is very steep, and the output waveform of the comparator 23 is a rectangular wave. The rectangular wave is subjected to voltage level conversion via a photocoupler 24, and a rotor position signal X 'for the A phase is output. Here, assuming that the level of the reference voltage Vref is 0 V, a rising edge or a falling edge of the rotor position signal appears at the zero cross point of the integrated waveform 38. Since the interval between the zero cross points is an electrical angle of 180 degrees, the period of the rotor position signals X ', Y', Z 'has an electrical angle of 36 as shown in FIG.
The rectangular waves are 0 degrees, the duty ratio is 50%, and each phase is shifted by 120 degrees.

In FIG. 4, the commutation point CA of the A-phase is shifted to a position shifted in phase by 60 degrees from the falling edge of the rotor position signal X 'with respect to the position CP of the zero cross point of the integrated waveform 38, that is, the A-phase. Exists. As described above, the rotor position signals X ', Y', and Z 'for each phase are rectangular waves having a duty ratio of 50% and a pulse width of 180 electrical degrees, each phase being shifted by 120 degrees. As shown in
The X ', Y', and Z 'pulse edges are out of phase by 60 degrees each. Therefore, the commutation points CA and B of the A phase
The phase of the rising edge of the rotor position signal Y 'with respect to the phase will match. Therefore, if the rising edge of the Y 'is detected and commutation is performed on the A-phase + side, commutation can be performed at the correct timing. Similarly, the falling edge of X 'coincides with the commutation point of the other phase (here, the C-phase-side) except the A-phase, as shown in FIG. Similarly, when considering the B and C phases, the pulse edge of the rotor position signal of a certain phase coincides with the commutation point of another phase excluding that phase. Therefore, as shown in FIG. 5, the rotor can be rotationally driven by commutation as it is at the rising and falling edges of the rotor position signals X ', Y', Z 'for each phase.

As described above, in the above-described conventional sensorless motor driving device, the rotor position detection circuit 3 integrates the rotor position signal X ', which is obtained by integrating the motor terminal voltage.
The pulse edges of Y 'and Z' are detected, and the rotor is rotationally driven by commutation as it is. According to this method, since a special phase shift circuit or the like is not required, the circuit configuration is simplified, and the sensorless motor driving device can be provided at low cost.

[0008]

In the above-mentioned conventional method, commutation is performed by utilizing the fact that the zero-cross point of the waveform obtained by integrating the motor terminal voltage coincides with the commutation timing. However, actually, a spike voltage as shown in FIG. 7 or FIG. 8 is generated at the motor terminal. The spike voltage distorts the integrated waveform of the motor terminal voltage, and as shown in FIG. 8, the phase is advanced from the integrated waveform when no spike voltage is generated. As a result, the zero cross point of the integrated waveform also advances. Therefore, when commutation occurs at the zero-cross point of the integrated waveform by the above-described conventional method,
All commutation timings will also advance. In particular, when the load torque increases, that is, when the value of the current flowing through the motor increases, the width of the spike voltage increases, so that the leading phase amount of the zero cross point of the integral waveform also increases. Therefore, there is a problem that the shift of the commutation timing becomes large, the rotation becomes unstable, and in the worst case, a step-out occurs. Conventionally, when detecting the current value to determine the amount of delay, a transformer or a current detecting element using the Hall effect is used, but the detector itself is relatively expensive, so the entire device is required. However, there is a problem that the cost of the device becomes high and miniaturization of the device is restricted.

Therefore, the present invention employs an integration method for detecting the position of the rotor, and delays the commutation timing in accordance with the zero cross point of the integrated waveform due to the spike voltage, that is, the magnitude of the leading phase shift of the detected rotor position. By doing so, the purpose is to always perform commutation at the optimal timing, prevent loss of synchronism, and drive stably. Furthermore, by adopting a configuration that allows the delay characteristics to be easily changed from the outside,
The purpose is to flexibly cope with driving of motors having different characteristics. In addition, a differential amplifier is used to amplify a potential difference generated at both ends of a shunt resistor inserted in series at a point to be detected, without using a special detector as described above in a current detection circuit for determining a delay amount. By taking a simple configuration of detecting the current value,
It aims at realizing low cost and space saving.

[0010]

A position sensorless motor driving apparatus according to the first aspect of the present invention includes an inverter circuit for driving a motor to rotate, detects a rotor position by using a motor terminal voltage, and externally detects the rotor position. A sensorless motor drive device that drives by commutating to a stator winding without using a position detector provided with an integral circuit for integrating the motor terminal voltage, and a square indicating the position of the rotor from the output of the integral circuit A rotor position detection circuit including a comparator for generating a wave; a unit electric angle measurement circuit for calculating a time corresponding to an electric angle of 1 degree from the rotor position signal; and a current detection for detecting a current flowing through the motor Circuit, an A / D converter for A / D converting a current value detected by the current detection circuit, and a peak hold for holding a peak value of the A / D converted current waveform And road, a commutation pulse to the optimum commutation point determines the electrical angle delay amount necessary to delay in response to the detected current peak value, and a configuration in which a lead angle adjusting circuit for outputting.

According to a second aspect of the present invention, there is provided a position sensorless motor driving apparatus, wherein the advance angle adjusting circuit includes a multiplier for calculating a delay amount from a detected current value based on a multiplication constant given from the outside; A read-only storage device in which the relationship of the delay amount corresponding to the detected current value is described in advance; and a selector for selecting one of the delay amounts output from the multiplier and the read-only storage device, wherein the multiplication constant is Alternatively, the delay characteristics can be easily changed by changing the contents of the read-only storage device.

According to a third aspect of the present invention, there is provided a position sensorless motor driving device, wherein the current detecting circuit comprises a shunt resistor inserted in series between an inverter and a motor, and a potential difference between both ends of the shunt resistor. And a simple circuit configuration for detecting the current flowing through the motor based on the output voltage of the differential amplifier.

[0013]

[Function] In order to drive a motor without a position sensor, the terminal voltage of each phase of the motor is integrated by a rotor position detection circuit.
A comparison process is performed to generate a square wave indicating the position of the rotor with respect to each of the phases. The unit electrical angle measuring circuit measures the pulse width of the square wave and calculates the time per degree of electrical angle. Here, a spike voltage appears at the motor terminal due to the back electromotive force generated in the stator winding with the rotation of the rotor. The spike voltage causes a distortion in a motor terminal voltage integration waveform in the rotor position detection circuit, and as a result, a phase shift occurs in the rotor position signal.

In order to cancel the advance phase shift,
In the current detection circuit, a current flowing into or out of the stator winding as the rotor rotates is detected as a voltage value equivalent to a current value. After the detected current value is converted into a digital value by the A / D converter, the peak value (peak value) of the current waveform is held by the peak hold circuit. The electrical angle delay amount corresponding to the current value is determined by the advance angle adjustment circuit from the detected current value of the current waveform peak described above, and is reflected in the commutation timing to actually cancel the advance phase shift from the unit electrical angle. The amount of electrical angle delay to be performed is determined and output.

Thereafter, a commutation signal is generated in the commutation signal generation circuit by delaying the phase of the rotor position signal of each phase by the electrical angle delay amount. Then, a drive signal is generated based on the phase-shifted commutation timing of each phase, and the stator is excited by the inverter to rotate the rotor. As a result, the stator windings can be always excited at an optimal timing according to the motor driving condition, and the motor can be driven stably.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a circuit block diagram in which the position sensorless motor driving device according to the present embodiment is applied to position sensorless driving of a three-phase stepping motor. First, FIG.
The outline of the operation of the position sensorless motor driving device in the present embodiment will be described based on FIG. 1 is a three-phase stepping motor in which three-phase stator windings are connected in a Y-shape, La and L
b and Lc respectively represent A of the three-phase stepping motor.
Phase, B phase, C phase stator windings, 2 are stator windings La, L
An inverter for rotating the three-phase stepping motor 1 by commutation to b and Lc. Inverter 2
The stator windings La, Lb, Lc of the three-phase stepping motor 1 are energized via output terminals Da, Db, Dc, respectively, and the rotor is driven to rotate.

In this embodiment, the three-phase stepping motor 1 performs closed loop control without using a separate position sensor such as an encoder. That is, it is driven without a position sensor. The position of the rotor of the three-phase stepping motor 1 can be detected by processing the voltage of the output terminal of the inverter 2 by the rotor position detection circuit 3. From the rotor position detection circuit 3, rotor position signals X, Y, and Z, which are rectangular wave signals representing the positional relationship of the rotor with respect to each of the phases A, B, and C of the three-phase stepping motor 1, are output. You. Based on the rotor position signals X, Y and Z, a timing of commutation to the stator windings La, Lb and Lc is generated.

By the way, as described above, the stator winding L of the three-phase stepping motor 1 is
Back electromotive force is generated in a, Lb, and Lc. This back electromotive force causes the motor terminal or the inverter output terminal D
A sharp spike voltage appears in the voltage waveforms of a, Db, and Dc. Due to this spike voltage, the phase of the rotor position signals X, Y, and Z is shifted in the direction in which the rotor position signal advances when no spike voltage correctly representing the position of the rotor is generated. Occurs. Therefore, if commutation is directly performed from the rotor position signals X, Y, and Z by the above-described conventional method, commutation timing also advances, and commutation at an optimal timing cannot be performed. Therefore, in the present invention, as shown in FIG. 6, a unit electric angle measurement circuit 4, a current detection circuit 5, an A / D converter 6, a peak hold circuit 7 are added to the conventional position sensorless motor driving device shown in FIG. And a lead angle adjusting circuit 8 is added.
The advance phase shift is canceled by means described below.

The magnitude of the leading phase shift is proportional to the current flowing through the stator windings La, Lb, Lc. Therefore,
Stator windings La, L of the three-phase stepping motor 1
b, Lc and the inverter output terminals Da, Db, Dc, respectively, shunt resistors Rs are inserted in series, respectively, and when a current flows through the shunt resistor Rs, a voltage generated at both ends of the shunt resistor Rs is used. , The current value flowing through the stator windings La, Lb, Lc with the rotation of the rotor is detected as a voltage value equivalent thereto. After the detected current value is converted into a digital value by the A / D converter 6, the peak value (peak value) of the current waveform is held by the peak hold circuit 7. The unit electrical angle measuring circuit 4 measures the pulse width of the rotor position signals X, Y, and Z, and measures the time per electrical angle. Based on the detected current value of the current waveform peak and the time of 1 electrical angle output from the unit electrical angle measurement circuit 4, the electrical angle delay amount d for which the advance phase shift should be canceled by the advance angle adjustment circuit 8 is calculated. Generate. In the commutation signal generation circuit 9, the rotor position signals X,
Commutation signals AP to CN whose phases are delayed by the electrical angle delay amount d with respect to Y and Z are generated. Then, the drive signal generation circuit 1 is operated by the commutation signals AP to CN that have been phase-shifted.
0 to generate drive signals A + to C- and control the inverter 2 so that the stator windings La, Lb,
Lc is excited and the rotor rotates.

Next, details of each block constituting the position sensorless motor driving device shown in FIG. 6 will be described with reference to the drawings. FIG. 7 shows the terminal voltage waveforms 41, 42, 43 of each of the phases A, B, C of the three-phase stepping motor 1 of FIG.
And a waveform 4 obtained by integrating the terminal voltages 41, 42, 43
FIG. 8 shows the relationship between the waveforms of 4, 45, 46 and the rotor position signals X, Y, Z. FIG. 8 shows that the phases of the rotor position signals X, Y, Z are advanced by spike voltages generated at motor terminals. FIG. 9 illustrates the relationship between the rotor position signal waveforms X, Y, and Z, the commutation signal waveforms AP to CN, and the current waveform flowing through the motor. FIG. 10 is an example of a circuit configuration of a 120-degree conduction voltage type inverter 2 that rotationally drives the three-phase stepping motor 1. The inverter 2 includes a P-side MOSFET, Fa +, Fb +, and Fc +, and an N-side M
OS FET (hereinafter simply referred to as FET), Fa−, Fb
-, Fc-. P-side FET and N-side F
ET is combined with one set to perform chopper control, and three-phase DC current is selectively passed through two of the stator windings sequentially to form a magnetic field, thereby driving the rotor to rotate. Let it.

The inverter 2 is controlled to detect the position of the rotor in order to commutate to the stator winding at an optimum timing. In the present invention, the position of the rotor is detected by using the rotor position detection circuit (for one phase) shown in FIG. 2 and integrating and comparing the motor terminal voltages as described above. In this embodiment, since the three-phase stepping motor 1 is driven, the rotor position signals X, Y, and Z for each of the A, B, and C phases are obtained.

In a 120-degree conduction type inverter,
Each phase has an open period of 60 ° × 2 times (a period during which no drive signal is applied to the FET) within a period of 360 ° electrical angle. The phase in this open period is called an open phase. As shown in the A-phase terminal voltage waveform 41 of FIG. 7 or FIG. 8 by the back electromotive force generated in the stator winding with the rotation of the rotor,
During the open period, a spike voltage is generated at the same time as the back electromotive voltage is generated. Due to this spike voltage, as shown in FIG. 8, the actual integrated waveform 44 has a distorted shape with the phase advanced by d 'with respect to the terminal voltage integrated waveform 38 when no spike voltage is generated.

However, as described above, since the phase of the zero-cross point of the integrated waveform is actually advanced by d 'due to the spike voltage, the rotor position signal X is not included in the rotor position signal when there is no spike voltage. X 'is shifted from lead X' by the leading phase amount d '. Therefore, the rotor position signal X
Commutation at the rising or falling edge of
Since the commutation timing is advanced, the rotation becomes unstable, or in the worst case, a step-out occurs. Therefore, in order to realize commutation at an optimal timing, a mechanism for correcting the advance phase amount d 'is required. Here, the distortion of the integrated waveform 44, that is, the magnitude of the advance phase amount d 'is not always constant, but varies according to the rotation state of the motor. Therefore, it is necessary to always optimally correct the advance phase amount d 'that changes every moment according to the rotation state of the motor.

The magnitude of the advance phase amount d 'depends on the pulse width of the spike voltage. The present invention focuses on the fact that the spike voltage pulse width is proportional to the magnitude of the rotating load, that is, the current flowing through the motor, and detects the current flowing through the motor.
Based on the detected current value, the advance phase amount d 'is estimated and corrected, so that commutation can be performed at an optimal timing.

FIG. 11 is a circuit diagram of one phase of a current detection circuit constituting a position sensorless motor driving device, and is composed of a shunt resistor Rs, a differential amplifier 25, an output level adjustment amplifier 26, and a clamp circuit 27. . The shunt resistor Rs has a very small resistance value of, for example, about 0.5Ω. As shown in FIG. 6 or FIG. 10, the inverter output terminals Da, Db, Dc and the motor stator windings La, Lb are used. , Lc. When a current flows between the inverter 2 and the motor 1, a potential difference corresponding to the current value is generated between both ends of the shunt resistor Rs. This potential difference is amplified by a differential amplifier 25 shown in FIG. 11 and output as a voltage value equivalent to a current value via an output level adjustment amplifier 26. Since the current flowing through the motor swings to the minus side as shown by the current waveform 47 in FIG. 9, the minus component is cut by the clamp circuit 27 in FIG. 11 and then input to the A / D converter 6. In the present embodiment, since the same current waveform is applied to all three phases, only the detected current value for one phase (A phase in this embodiment) is input to the A / D converter.

The current value converted into 8-bit binary data by the A / D converter 6 shown in FIG. 6 is searched for and held by the peak hold circuit 7 for the peak value (peak value) of the current waveform. The retention period of the peak is 360 electrical degrees, and the peak value is refreshed each time, so that real-time current detection is possible.

Based on the detected current value, the delay amount for canceling the advance phase amount d 'from the pulse edges of the d' advance phase rotor position signals X, Y and Z shown in FIGS. By delaying the commutation by d, the phase can be returned to the normal commutation point and commutation can be performed at an optimal timing.
Here, the delay amount d depends on both the current value and the motor speed. That is, even if the current value is the same, the delay amount d is different if the motor rotation speed is different. Therefore, when determining the delay amount, two parameters of the current value and the motor rotation speed must be considered. In the present invention, the advance angle adjustment circuit is configured so that the parameter of the motor rotation speed is apparently eliminated by giving the delay amount in electrical angle, and only the delay amount with respect to the current value needs to be considered. Furthermore, by configuring the correspondence between the current value and the delay amount so that it can be set and changed from outside, it is possible to apply the optimum delay to each motor with different characteristics.

In the unit electrical angle measuring circuit 4 of FIG. 6, based on the electrical angle of 1 degree measured from the rotor position signals X, Y, Z having a pulse width of 180 electrical degrees, that is, the time of the unit electrical angle, , The lead angle adjustment circuit 8 determines and outputs the electrical angle delay amount d corresponding to the detected current value output from the peak hold circuit 7. To determine the delay amount d, a multiplication method for calculating the delay amount from an externally applied multiplication constant and a detected current value, and the contents of a read-only storage device in which the relationship between the delay amounts corresponding to the respective detected current values is described in advance. Can be selected. FIG. 12 is a circuit diagram of the advance angle adjusting circuit 8. As shown in FIG. In the case of the multiplication method,
A multiplication constant of 8-bit binary data (a value that delays the product of the detected current value) is set in a multiplication constant setting unit 28 composed of, for example, a DIP SW from the outside.
, The product of the detected current value and the multiplication constant, that is, the electrical angle delay amount d is calculated and output. Note that the multiplication constant can be set by generating and inputting a multiplication constant of 8-bit binary data from a microcomputer or the like instead of the multiplication constant setting unit 28. In the case of the ROM system, an electric angle delay amount d with respect to the current value is stored in the read-only storage device 30 using the current value in 8-bit binary notation as an address.
Is described in advance, and when the detected current value is input to the read-only storage device 30 as an address, the electrical angle delay d corresponding thereto is output from the read-only storage device 30. Switching between the multiplication method and the ROM method is performed by the selector 31.
Done by The output of the delay amount to the commutation signal generation circuit is
This is performed in accordance with the refresh timing of the peak hold circuit 7.

As an example, the operation of the lead angle adjusting circuit 8 when the multiplication method is used will be described below. It is assumed that the relationship between the current value and the electrical angle delay amount is a straight line as shown in FIG. Now, if the current value from 0 to 2 A is represented by 8 bits, the value from 0 to 2 A is represented by 256 levels. When the current value is 2 A, the signal input to the input terminal B of the multiplier 29 is 256 in decimal notation, and when the delay characteristic of FIG. 13 is applied, the electrical angle delay amount at this time is 160 degrees. Therefore, here, if the input current value is multiplied by 160/256, the electric angle delay amount to be obtained can be obtained, and 160/256 becomes the multiplication constant here. 160/2
56 = 0.625, which is 0.101 in binary notation, and a value up to eight digits after the decimal point, that is, 10100000 is set as a multiplication constant by the multiplication constant setting unit 28.

For example, when the current value is 0.5 A, the multiplier 2
Data “01000000” in binary notation is input to the terminal B of No. 9. The multiplier 29 takes a logical product for each bit of the data of the terminal B and the data of 10100000 set by the multiplication constant setting unit 28 inputted to the terminal A, and adds them to obtain a data of 00101000. The expressed electrical angle delay amount is output to the A × B terminal. Since the output is 40 in decimal notation, this result matches the delay characteristic of FIG. Here, the multiplier 29
Has the function of outputting the product of the values input to the terminals A and B (however, since the product of 8-bit data is 16-bit data, the lower 8 bits of the data are discarded). In the same manner, in the ROM system, the current value of 010000000 (current value is expressed in binary) in the read-only storage device 30 is stored in the address of 010000000.
(= 0.5 A) electrical angle delay amount data 0010
1000 (= 40 degrees) is stored in advance, and when the current value is input to the terminal AD, the electric angle delay amount is stored in the terminal DA.
Output from TA.

In the above, the relationship between the current value and the electrical angle delay amount has been described as a straight line as shown in FIG. However, in practice, the optimal relationship between the current value and the electrical angle delay amount for stably driving the motor is not always linear, and may be curved depending on the motor. Also,
When the load applied to the motor is small, it may be linear, but may become curved as the load, that is, the current, increases. In the ROM system, the relationship between the current value and the electrical angle delay amount is not limited to a straight line, but can be an arbitrary curve, so that an optimal delay can always be applied in a wide operating region.

In the ROM method, in order to change the delay characteristic once set, it is necessary to replace the read-only storage device itself. On the other hand, in the multiplication method, since the delay characteristic can be changed at any time by the multiplication constant setting device, it is not necessary to change the device itself even if the characteristics of the motor change, and it is possible to respond flexibly. Further, in the advance angle adjustment mechanism using the multiplication method, the motor drive circuit including the advance angle adjustment circuit can be made into a one-chip IC, so that the motor drive circuit can be provided at low cost. Become.

Further, in the present invention, when the delay amount is determined, the multiplication method and the ROM method are switched by the selector, so that the advantages of both the multiplication method and the ROM method can be utilized. For example, it is possible to switch the delay amount determination method according to the detected current value.
That is, the multiplication method is selected when the current value is 0 to 1 A, and
Up to 2A, a form in which a ROM method is selected can be adopted. Therefore, step-out can be suppressed in a wider operation range than before, and it is possible to flexibly cope with various motors having different characteristics and to constantly drive the motor stably.

In this embodiment, in the commutation signal generation circuit, A, B, C
For each phase, a total of six commutation signals for controlling the + side and − side FETs are generated. The commutation signals AP to CN
As shown in FIG. 9, the rising edge and the falling edge of the rotor position signals X, Y, Z are respectively delayed at the timing delayed by the electrical angle delay amount d output from the advance angle adjusting circuit 8. Rising and falling are performed, and the pulse HIGH period becomes a rectangular wave having an electrical angle of 120 degrees. With the above configuration, commutation is performed at an optimal timing.

[0035]

As described above, according to the present invention,
It is a position sensor-less system that does not require expensive encoders or Hall elements to detect the position of the rotor, and has a simple configuration that does not require expensive components in the current detection circuit. The effect is that the cost is reduced.

Further, there is provided an advance angle adjustment circuit for correcting an advance phase shift in accordance with the detected current value, and an electric angle delay amount determining mechanism in the advance angle adjustment circuit uses a multiplication method and a ROM method. By switching, the delay characteristics can be set and changed arbitrarily from the outside, so that step-out is suppressed in a wider operating range than before, and it is possible to flexibly handle various motors with different characteristics. In addition, stable driving was always possible.

[Brief description of the drawings]

FIG. 1 shows a conventional position sensor-less motor drive device of three types.
It is a circuit block diagram applied to the position sensorless drive of a phase stepping motor.

FIG. 2 is a circuit diagram of one phase of a rotor position detection circuit.

FIG. 3 is a diagram illustrating a relationship between a terminal voltage waveform of a three-phase stepping motor, a terminal voltage integrated waveform, and a rotor position signal waveform when no spike voltage is generated.

FIG. 4 is a diagram illustrating a mechanism for generating a rotor position signal from a motor terminal voltage in a conventional position sensorless motor drive device.

FIG. 5 is a diagram showing a relationship between a rotor position signal waveform and a commutation signal waveform in a conventional position sensorless motor drive device.

FIG. 6 is a circuit block diagram in which a position sensorless motor driving device according to an embodiment of the present invention is applied to position sensorless driving of a three-phase stepping motor.

FIG. 7 is a diagram showing a relationship among a terminal voltage waveform, a terminal voltage integrated waveform, and a rotor position signal waveform of the three-phase stepping motor according to one embodiment of the present invention.

FIG. 8 is a diagram illustrating a phenomenon in which the phase of a rotor position signal advances due to a spike voltage generated at a motor terminal.

FIG. 9 is a diagram showing a relationship among a rotor position signal waveform, a commutation signal waveform, and a current waveform flowing through a motor according to an embodiment of the present invention.

FIG. 10 is a circuit configuration example of a three-phase 120 ° conduction voltage type inverter.

FIG. 11 is a circuit diagram of one phase of a current detection circuit.

FIG. 12 is a circuit configuration diagram of a lead angle adjustment circuit.

FIG. 13 is a diagram illustrating an example of a delay characteristic representing a correspondence relationship between a detected current value and an electrical angle delay amount.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 three-phase stepping motor 2 120-degree conducting voltage type inverter 3 rotor position detection circuit 4 unit electric angle measurement circuit 5 current detection circuit 6 A / D converter 7 peak hold circuit 8 advance angle adjustment circuit 9 commutation signal generation circuit 10 drive Signal generation circuit 21 Filter 22 Integrator 23 Comparator 24 Photocoupler 25 Differential amplifier 26 Output level adjustment circuit 27 Clamp circuit 28 Multiplication constant setting device 29 Multiplier 30 Read-only storage device 31 Selector 35 A-phase terminal voltage waveform without spike voltage 36 B-phase terminal voltage waveform without spike voltage 37 C-phase terminal voltage waveform without spike voltage 38 A-phase terminal voltage integral waveform without spike voltage 39 B-phase terminal voltage integral waveform without spike voltage 40 Spike voltage Phase terminal voltage when no noise occurs Separated waveform 41 A-phase terminal voltage waveform 42 B-phase terminal voltage waveform 43 C-phase terminal voltage waveform 44 A-phase terminal voltage integration waveform 45 B-phase terminal voltage integration waveform 46 C-phase terminal voltage integration waveform 47 C-phase current waveform X, Y, Z A, B, C Rotor position signals X ', Y', Z 'A when no spike voltage is generated
Rotor position signal for phase AP A phase + side commutation signal AN A phase-side commutation signal BP B phase + side commutation signal BN B phase-side commutation signal CP C phase + side commutation signal CN C phase- Side commutation signal A + A phase + side drive signal A− A phase− side drive signal B + B phase + side drive signal B− B phase− side drive signal C + C phase + side drive signal C− C phase− side drive signal d ′ Zero-cross point advance phase d Electric angle delay

Claims (3)

[Claims] An inverter circuit for rotating and driving a motor, wherein a rotor position is detected using a motor terminal voltage;
A position sensorless motor drive device that commutates and drives a stator winding without using an external position detector, and an integration circuit that integrates a motor terminal voltage, and a position of a rotor is indicated from an output of the integration circuit. A rotor position detection circuit composed of a comparator for generating a square wave, a unit electric angle measurement circuit for calculating a time corresponding to an electric angle of 1 degree from the rotor position signal, and a current for detecting a current flowing through the motor A detection circuit, an A / D converter for A / D converting the current value detected by the current detection circuit, a peak hold circuit for holding a peak value of the A / D converted current waveform, and a detection current peak value A position sensorless mode characterized by comprising an advancing angle adjustment circuit for determining and outputting an electrical angle delay amount necessary to delay a commutation pulse to an optimum commutation point according to Drive. 2. A read-only memory comprising: a multiplier for calculating a delay amount from a multiplication constant given from outside and a detected current value; and a read-only memory in which a relationship between delay amounts corresponding to each detected current value is described in advance. 2. The position sensorless motor driving device according to claim 1, further comprising a device and a selector for selecting one of the delay amounts output from the multiplier and the read-only storage device. 3. A current detection circuit comprising a shunt resistor inserted in series between an inverter and a motor, and a differential amplifier for amplifying a potential difference between both ends of the shunt resistor. The position sensorless motor drive device according to claim 2.