JP3958434B2 - Rotation position detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotational position detection device that detects a rotational position of a rotor of a motor, for example, a brushless motor.
[0002]
[Prior art]
The brushless motor includes a stator having a plurality of phase windings and a rotor having a permanent magnet, and the rotor rotates by the interaction between the magnetic field generated in each phase winding and the magnetic field created by the permanent magnet of the rotor.
[0003]
In driving the brushless motor, an inverter for supplying a driving voltage is prepared. Then, the rotational position of the rotor of the brushless motor is detected, and the switching of the inverter is controlled according to the detected position, whereby the supply of the driving voltage to each phase winding is controlled.
[0004]
The rotational position of the rotor is detected, for example, by providing a magnetic sensor (for example, a Hall element) around the stator of the brushless motor and taking out the output of the magnetic sensor as a rotational position detection signal.
[0005]
On the other hand, using a rotational position detection signal (referred to as rotational position detection signal A) based on the output of the magnetic sensor, a rotational position detection signal (referred to as rotational position detection signal B) with higher resolution than that rotational position detection signal A is obtained. The method is disclosed in Japanese Patent Laid-Open No. 4-304191.
[0006]
Further, in the case of detecting the rotational position by extracting the voltage induced in the non-energized phase of each phase winding of the brushless motor without using the magnetic sensor, the induced voltage signal is expressed as shown in, for example, Japanese Patent No. 2642357. As a rotational position detection signal (referred to as rotational position detection signal A), there is a signal that obtains a signal having a frequency twice that frequency (referred to as rotational position detection signal B).
[0007]
[Problems to be solved by the invention]
When the rotational position detection signal B is obtained as in the above example, the period of the rotational position detection signal A is quantized by the counter.
During this quantization, there is a problem that a bit error in the range of “+1” (truncated) occurs in the count value of the counter, and this bit error appears as an error of the rotational position detection signal B.
[0008]
That is, the rotational position detection signal B determines the voltage applied to each phase winding of the brushless motor. Under the situation where an error occurs as described above, the operation efficiency of the motor deteriorates and the phase is increased accordingly. Increase in winding temperature increases.
[0009]
The present invention takes the above-mentioned circumstances into consideration, and an object of the present invention is to obtain a high-resolution rotational position detection signal with little error, thereby improving motor operating efficiency and winding the motor. An object of the present invention is to provide a rotational position detection device capable of suppressing an increase in linear temperature.
[0010]
Another object of the present invention is to provide a rotational position detection device that can be integrated into an integrated circuit together with an inverter for driving a motor and its drive control circuit.
A further object of the present invention is to provide a rotational position detecting device that can be integrated with a stator of a motor.
[0012]
[Means for solving the problems]
Rotational position detecting device of the first invention (Claim 1), in which outputs a rotation position detection signal corresponding to the rotational position of the motor, the first clock signal is counted in synchronization with the rotational position detection signal A first counter to be reset, holding means for holding the count value Ca of the first counter in synchronization with the rotational position detection signal, a second clock signal having a frequency higher than the first clock signal, A second counter that is reset in synchronization with the rotational position detection signal, the holding value Ca of the holding means and the count value Cb of the second counter are compared, and the first signal is output under the condition Ca <Cb; Comparing means for outputting a second signal under the condition of Ca = Cb; selecting the first signal of the comparing means when the first clock signal is at a high level; comparing means when the first clock signal is at a low level Selection means for selecting the second signal, and resetting the second counter by the signal selected by the selection means, and outputting the selected signal as a high resolution rotational position detection signal. A rotational position detection device characterized.
[0014]
Rotational position detecting device of the second aspect of the present invention (Claim 2), in which outputs a rotation position detection signal corresponding to the rotational position of the motor, the first clock signal is counted in synchronization with the rotational position detection signal The first counter to be reset, the holding means for holding the count value of the first counter in synchronization with the rotational position detection signal, and the resetting means that is reset in synchronization with the rotational position detection signal, and the holding means for each reset. A second counter that outputs a borrow signal that counts down with a second clock signal having a frequency higher than that of the first clock signal and that is high when the count value is zero and low when the count value is zero ; When the first clock signal is at a high level, the second counter is synchronized with the falling edge of the borrow signal, and when the first clock signal is at a low level, the second counter is borrowed. Selecting means for selectively outputting a signal synchronized with the rise of the signal, resetting the second counter by the output signal of the selection means, and outputting the output signal as a high resolution rotational position detection signal. A rotational position detection device characterized.
[0015]
The third rotation position detecting device of the invention (claim 3), in either the first or second aspect of the invention, the motor is a brushless motor, an inverter and a drive control circuit for driving the brushless motor An integrated circuit is formed with the device.
[0016]
Fourth rotational position detecting device of the present invention (Claim 4), in any one of the first or second aspect of the invention, the motor is a brushless motor, an inverter and a drive control circuit for driving the brushless motor It is integrated with the stator of the brushless motor together with the device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
[1] A first embodiment of the present invention will be described below with reference to the drawings.
First, a brushless motor and its drive control circuit according to the present invention will be described with reference to FIG.
[0018]
In FIG. 1, a transistor inverter 2 is connected to a main power source 1 that generates a DC voltage. The transistor inverter 2 has a series circuit of a pair of switching transistors for each phase of the motor M, and drives each transistor on and off according to a driving signal for three phases supplied from a switching unit 14 described later. As a result, a driving voltage (three-phase line voltage) for the three phase windings mounted on the stator of the motor M is output.
[0019]
A rotor position detector 3 is provided in the motor M. The rotor position detector 3 has three magnetic sensors (U-phase PS, V-phase PS, and W-phase PS) arranged at intervals of 120 electrical degrees, and outputs a signal whose level changes according to the rotational position of the rotor. Emanating from a magnetic sensor. The output signals of these magnetic sensors are logically synthesized by the logic synthesis unit 3a to become one rotational position detection signal A.
[0020]
The rotational position detection signal A is supplied to the rotational position detector 4 which is the rotational position detector of the present invention.
Based on the rotational position detection signal A, the rotational position detection unit 4 creates and outputs a rotational position detection signal B with higher resolution than the rotational position detection signal A. The rotational position detection signal B is supplied to the waveform reading unit 5.
[0021]
The waveform reading unit 5 obtains an address for the waveform pattern data by a predetermined counting operation based on the rotational position detection signal B. This value is supplied to the waveform storage unit 6 as an address designation command.
[0022]
The waveform storage unit 6 stores a waveform pattern of a modulation signal, which will be described later, as digital data in advance, and sequentially reads and reads the digital data according to the value of the waveform reading unit 5. The read digital data is converted into an analog signal by a D / A (digital / analog) converter 7 and supplied to a modulation amplifier 8. The modulation amplification unit 8 generates a modulation signal having a predetermined waveform by processing the analog signal from the D / A conversion unit 7 in accordance with a speed control signal from an operational amplifier 17 described later, and amplifies and outputs the modulation signal. To do.
[0023]
The modulation signal thus obtained is input to a non-inverting input terminal (+) of an analog comparator (drive signal generating means) 9. The inverting input terminal (−) of the comparator 9 receives a triangular wave signal (a carrier signal having a frequency of 16 kHz or higher) emitted from the triangular wave signal generator 10.
[0024]
The comparator 9 outputs a drive signal for the inverter 2 by comparing the voltage of the modulation signal and the triangular wave signal. This drive signal is supplied to the switching unit 14 via the overcurrent protection unit 12 and the dead time setting unit 13.
[0025]
The overcurrent protection unit 12 responds to the detection result of the overcurrent detection unit 11 inserted into the energization line between the main power source 1 and the inverter 2, and from the comparator 9 to the dead time setting unit 13 when overcurrent is detected. The dead time setting unit 13 that cuts off the supply of the drive signal to the inverter 2 is alternately turned on and off by a pair of switching transistors (a pair of transistors located on the upstream side and downstream side of the current) for each phase in the inverter 2 In this case, a certain time difference, so-called dead time, is secured between the ON / OFF switching point of one transistor and the ON / OFF switching point of the other transistor, and both transistors simultaneously have an ON period (both This is to avoid a situation where a short circuit is formed through a transistor.
[0026]
The switching unit 14 switches and outputs either the drive signal that has passed through the dead time setting unit 13 or the drive signal from the 120 ° matrix unit 15 described later based on an instruction from the rotational position detection unit 4. Specifically, in the low speed range from the start of the motor M to a predetermined speed, a drive signal from the 120 ° matrix section 15 is output, and after exceeding the predetermined speed, a drive signal that has passed through the dead time setting section 13 is output. .
[0027]
The 120 ° matrix section 15 outputs a drive signal for starting the motor.
Further, the rotational position detection signal A is supplied to the speed detection unit 16. The speed detector 16 detects the speed of the motor M from the rotational position detection signal A, and outputs a voltage level signal corresponding to the detected speed. This output is input to the inverting input terminal (−) of the differential amplifier 17. The output of the speed command unit 18 is input to the non-inverting input terminal (+) of the differential amplifier 17. The speed command unit 18 outputs a voltage level signal corresponding to the set speed.
[0028]
The differential amplifier 17 amplifies and outputs the difference between both input voltages. This output is supplied to the modulation amplifier 8 as a speed control signal.
Hereinafter, the configuration of the rotational position detector 4 will be described with reference to FIG.
[0029]
A clock signal CK 2 having a frequency F 2 is generated from the clock signal generation circuit 21 and supplied to the prescaler 22. The prescaler 22 divides the clock signal CK2 to generate a clock signal CK1 having a frequency F1 that is 1/64 of the frequency F2 (F1 <F2), and is reset in synchronization with the rotational position detection signal A.
[0030]
A clock signal CK 1 generated from the prescaler 22 is supplied to an up counter (first counter) 23. The counter 23 counts up the clock signal CK1, and is reset in synchronization with the rotational position detection signal A.
[0031]
The count value Ca of the counter 23 is supplied to a latch circuit (holding means) 25. The latch circuit 25 sequentially updates and holds the count value Ca in synchronization with the rotational position detection signal A.
[0032]
Further, the clock signal CK 2 generated from the clock signal generation circuit 21 is supplied to the up counter (second counter) 24. The counter 24 counts up the clock signal CK2, and is reset in synchronization with the rotational position detection signal A and reset in synchronization with a rotational position detection signal B described later.
[0033]
Then, the hold value Ca of the latch circuit 25 and the count value Cb of the counter 24 are supplied to a magnitude comparator (comparison means) 26. The magnitude comparator 26 compares the held value Ca and the count value Cb, outputs a first signal under the condition Ca <Cb (hereinafter referred to as Ca <Cb signal), and outputs the second signal under the condition Ca = Cb. (Hereinafter referred to as Ca = Cb). Both signals are supplied to the signal selection circuit 27.
[0034]
The signal selection circuit 27 takes in the clock signal CK1 generated from the prescaler 22, selects the Ca <Cb signal when the clock signal CK1 is at a high level, and selects Ca = Cb when the clock signal CK1 is at a low level.
[0035]
The signal selected by the signal selection circuit 27 is supplied to the counter 24 as a reset signal, and is finally output as a rotational position detection signal B with higher resolution than the rotational position detection signal A.
[0036]
A specific configuration of the rotational position detector 4 is shown in FIG.
Next, the operation of the rotational position detector 4 will be described.
First, as the rotor of the motor M rotates, signals are output from the three magnetic sensors (U-phase PS, V-phase PS, and W-phase PS) of the rotor position detector 3, and the signals are logically synthesized to produce a rotational position detection signal. FIG. 4 shows how A is obtained, how the rotational position detection signal A is up-counted by the counter 23, and how high-resolution rotational position detection signal B is obtained.
[0037]
FIG. 5 shows the correlation between the rotational position detection signal A, the clock signal CK1, and the count value Ca of the counter 23 in time series, and after the rotational position detection signal A changes in level (position detection timing). In FIG. 5, the correlation between the clock signal CK2, the count value Cb of the counter 24, the Ca <Cb signal, and Ca = Cb is shown on an enlarged time axis.
[0038]
That is, when the level of the rotational position detection signal A changes, the counter 23 starts to be supplied with the 16th pulse (high level period) of the clock signal CK1, but at that time the count value Ca of the counter 23 is still “15”. (The originally desired count value is “15.5” or more and less than “16.0”, but this is not possible), and the count value Ca = “15” is held in the latch circuit 25.
[0039]
When the count up of one counter 24 advances and the count value Cb reaches “15”, the condition of Ca = Cb is satisfied, and the Ca = Cb signal is emitted from the magnitude comparator 26.
[0040]
When the count value Cb exceeds “15” and becomes “16”, the condition of Ca <Cb is satisfied, and the magnitude comparator 26 issues a Ca <Cb signal.
Here, the signal selection circuit 27 monitors the level of the clock signal CK1, and selects and outputs the Ca <Cb signal because the clock signal CK1 is at a high level (the 16th pulse period).
[0041]
The counter 24 is reset by the Ca <Cb signal. At the same time, the Ca <Cb signal becomes a high resolution rotational position detection signal B.
In short, the count value Ca of the counter 23 is originally desired to be a value not less than “15.5” and less than “16.0”, but this is not possible. Therefore, the value is rounded to “16”. To obtain a rotational position detection signal B.
[0042]
As shown in FIG. 6, when the rotational position detection signal A changes in level, the 16th pulse of the clock signal CK1 has already been supplied to the counter 23 (low level period), and 17 of the clock signal CK1. In a situation where the first pulse supply (high level period) has not yet started, the count value Ca of the counter 23 is “16” (the originally desired count value is larger than “16.0” and “16.5”). Less than that, but it is impossible). The count value Ca = “16” is held in the latch circuit 25.
[0043]
When the count up of one counter 24 proceeds and the count value Cb reaches “16”, the condition of Ca = Cb is satisfied, and the Ca = Cb signal is emitted from the magnitude comparator 26.
[0044]
Here, the signal selection circuit 27 monitors the level of the clock signal CK1, and the clock signal CK1 becomes low level (a period between the 16th pulse and the first pulse that starts newly). Therefore, the Ca = Cb signal is selected and output as it is.
[0045]
The counter 24 is reset by this Ca = Cb signal. At the same time, the Ca = Cb signal becomes a high resolution rotational position detection signal B.
Since the counter 24 is reset by the Ca = Cb signal, the count value Cb becomes “0” after “16”, and the condition of Ca <Cb is not satisfied.
[0046]
In short, the count value Ca of the counter 23 is originally desired to be a value larger than “16” and smaller than “16.5”, but this is impossible. Therefore, the timing is rounded to “16”. In addition, a rotational position detection signal B is obtained.
[0047]
As described above, regardless of the bit error in the range of “+1” (truncated) in the count value Ca of the counter 23, the influence of the bit error can be eliminated as much as possible, and the rotational position detection signal B with less error can be obtained. .
[0048]
Note that the data shown in FIG. 7 confirms how the error of the rotational position detection signal B appears according to the rotational speed of the motor M. In FIG. 7, the conventional example corresponds to the case where there is no function for outputting the Ca <Cb signal to the magnitude comparator 26 and the signal selection circuit 27 is not provided.
[0049]
For example, when the rotational speed is 41,000 revolutions / minute, the count value Cb directly related to the rotational position detection signal B is “68” in the conventional example, “63” in the present example, and the calculated value “64”. The difference is “4” in the conventional example and “1” in the present example, and a better result is obtained in this example.
[0050]
When the rotation speed is 39,678 revolutions / minute, the count value Cb is “66” in the conventional example and “62” in the present example, and the difference from the calculated value “64” is any of the conventional example and the present example. Is also “2”.
[0051]
When the rotational speed is 39,679 revolutions / minute, the count value Cb is “65” in the conventional example and “65” in the present example, and the difference from the calculated value “64” is any of the conventional example and the present example. Is also “1”.
[0052]
That is, although it depends on the rotational speed, it is certain that the error of the rotational position detection signal B is reduced.
By reducing the error of the rotational position detection signal B, the voltage applied to each phase winding of the motor M becomes as appropriate as possible, so that the operating efficiency of the motor M can be improved and the increase in the winding temperature of the motor M is suppressed. Can do.
[0053]
By suppressing an increase in the winding temperature of the motor M, the rotational position detector 4 can be integrated into a one-chip IC (integrated circuit) together with the inverter 2 and other circuits as shown by a two-dot chain line in FIG. It becomes possible. It is also possible to integrate the rotational position detector 4 with the stator of the motor M.
[0054]
[2] Next, a second embodiment of the present invention will be described.
As shown in FIG. 8, a down counter 28 is provided instead of the up counter 24 and the magnitude comparator 26 of the first embodiment, and an edge selection circuit 29 is provided instead of the signal selection circuit 27.
[0055]
The down counter 28 is reset in synchronization with the rotational position detection signal A, and each time the reset is performed, the down value 28 is counted down by the clock signal CK2, and the level changes depending on whether the count value Cc is zero or not. A so-called borrow signal is output. Specifically, a borrow signal is output that is at a high level when the count value Cc is zero and at a low level during other periods.
[0056]
The edge selection circuit 29 selects and outputs either a signal synchronized with the rising edge of the output signal (borrow signal) of the counter 28 or a signal synchronized with the falling edge according to the level of the clock signal CK1.
[0057]
The signal selected by the edge selection circuit 29 is supplied to the counter 28 as a reset signal and is finally output as a rotational position detection signal B with higher resolution than the rotational position detection signal A.
[0058]
Other configurations are the same as those of the first embodiment.
The operation will be described.
First, the clock signal CK1 and its counting operation will be described with reference to the example of FIG.
[0059]
When the level of the rotational position detection signal A changes, the counter 23 starts to be supplied with the 16th pulse (high level period) of the clock signal CK1, but the count value Ca of the counter 23 is still “15” at that time. (The originally desired count value is “15.5” or more and less than “16.0” but this is impossible), and the count value Ca = “15” is held in the latch circuit 25.
[0060]
The holding value Ca of the latch circuit 25 is loaded into the counter 28, and the counter 28 starts down-counting.
When the countdown of the counter 28 proceeds and the count value Cc reaches “0”, the borrow signal of the counter 28 rises to a high level. When the holding value Ca is loaded into the counter 28, the borrow signal falls to a low level.
[0061]
Here, the edge selection circuit 29 monitors the level of the clock signal CK1, and since the clock signal CK1 is at a high level (16th pulse period), the signal is synchronized with the fall of the borrow signal. Is output.
[0062]
The counter 24 is reset by the output signal of the edge selection circuit 29. At the same time, the output signal of the edge selection circuit 29 becomes a high resolution rotational position detection signal B.
[0063]
In short, the count value Ca of the counter 23 is originally desired to be a value not less than “15.5” and less than “16.0”, but this is not possible. Therefore, the value is rounded to “16”. To obtain a rotational position detection signal B.
[0064]
Next, an example of FIG. 6 will be described.
When the level of the rotational position detection signal A changes, the 16th pulse supply of the clock signal CK1 has already been completed to the counter 23 (low level period), and the 17th pulse supply of the clock signal CK1 (high level period) ) Has not yet started, the count value Ca of the counter 23 is “16” (the originally desired count value is larger than “16.0” and smaller than “16.5”, but this is not possible). Possible). The count value Ca = “16” is held in the latch circuit 25.
[0065]
The holding value Ca of the latch circuit 25 is loaded into the counter 28, and the counter 28 starts down-counting.
When the countdown of the counter 28 proceeds and the count value Cc reaches “0”, the borrow signal of the counter 28 rises to a high level. When the holding value Ca is loaded into the counter 28, the borrow signal falls to a low level.
[0066]
Here, the edge selection circuit 29 monitors the level of the clock signal CK1, and the clock signal CK1 is at a low level (a period between the 16th pulse and the first pulse that starts newly). Therefore, a signal synchronized with the rise of the borrow signal is output.
[0067]
The counter 24 is reset by the output signal of the edge selection circuit 29. At the same time, the output signal of the edge selection circuit 29 becomes a high resolution rotational position detection signal B.
[0068]
In short, the count value Ca of the counter 23 is originally desired to be a value larger than “16” and smaller than “16.5”, but this is impossible. Therefore, the timing is rounded to “16”. In addition, a rotational position detection signal B is obtained.
[3] The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention.
[0069]
【The invention's effect】
As described above, according to the present invention, the first clock signal is counted and reset in synchronization with the rotational position detection signal in the output of the rotational position detection signal corresponding to the rotational position of the motor. A counter, holding means for holding the count value Ca of the first counter in synchronization with the rotational position detection signal, a second counter for counting a second clock signal having a higher frequency than the first clock signal, and the holding A comparison means for comparing the holding value Ca of the means with the count value Cb of the second counter, outputting a first signal under the condition of Ca <Cb, and outputting a second signal under the condition of Ca = Cb; Selecting means for selecting one of the first signal and the second signal of the means according to the level of the first clock signal, and the second count by the signal selected by the selecting means. And the selected signal is output as a high-resolution rotational position detection signal, so that a high-resolution rotational position detection signal with few errors can be obtained, thereby improving the driving efficiency of the motor. It is possible to provide a rotational position detection device that can reduce the increase in the winding temperature of the motor.
[0070]
Further, according to the present invention, it is possible to provide a rotational position detecting device that can be integrated into an integrated circuit together with an inverter for driving a motor and its drive control circuit.
Furthermore, according to this invention, the rotational position detection apparatus which can be integrated with the stator of a motor can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a motor drive control circuit according to the present invention.
FIG. 2 is a block diagram showing the configuration of the first embodiment.
FIG. 3 is a block diagram showing a specific configuration of FIG. 2;
FIG. 4 is a time chart for explaining the overall operation of the first embodiment.
FIG. 5 is a time chart for explaining the operation of the main part of the first embodiment.
6 is a time chart for explaining the operation of the main part of the first embodiment under conditions different from those in FIG. 5; FIG.
FIG. 7 is a diagram showing experimental data comparing the effect of the first embodiment with a conventional example.
FIG. 8 is a block diagram showing a configuration of a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Inverter 3 ... Rotor position detection part 4 ... Rotation position detection part 21 ... Clock signal generation circuit 22 ... Prescaler 23 ... Up counter (1st counter)
24 ... Up counter (second counter)
25. Latch circuit (holding means)
26 ... Magnitude comparator (comparison means)
27: Signal selection circuit (selection means)
28 ... Down counter (second counter)
29 ... Edge selection circuit (selection means)

Claims (4)

In what outputs a rotational position detection signal according to the rotational position of the motor,
A first counter that counts a first clock signal and is reset in synchronization with the rotational position detection signal;
Holding means for holding the count value Ca of the first counter in synchronization with the rotational position detection signal;
A second counter that counts a second clock signal having a frequency higher than that of the first clock signal and is reset in synchronization with the rotational position detection signal;
Comparing means for comparing the holding value Ca of the holding means with the count value Cb of the second counter, outputting a first signal under the condition Ca <Cb, and outputting a second signal under the condition Ca = Cb;
Selecting means for selecting a first signal of the comparing means when the first clock signal is at a high level, and selecting a second signal of the comparing means when the first clock signal is at a low level;
A rotation position detection device, wherein the second counter is reset by a signal selected by the selection means, and the selected signal is output as a high resolution rotation position detection signal. In what outputs a rotational position detection signal according to the rotational position of the motor,
A first counter that counts a first clock signal and is reset in synchronization with the rotational position detection signal;
Holding means for holding the count value of the first counter in synchronization with the rotational position detection signal;
It is reset in synchronization with the rotational position detection signal, and at each reset, the holding value of the holding means is down-counted by a second clock signal having a frequency higher than that of the first clock signal, and is high when the count value is zero. A second counter that outputs a borrow signal that is low in other periods ;
Selecting means for selecting and outputting a signal that is synchronized with a fall of the borrow signal of the second counter when the first clock signal is at a high level and that is synchronized with a rise of the borrow signal of the second counter when the first clock signal is at a low level ; ,
A rotation position detecting device, wherein the second counter is reset by an output signal of the selection means, and the output signal is output as a high resolution rotation position detection signal. In the rotational position detection device according to claim 1 or 2 ,
The motor is a brushless motor;
An inverter for driving the brushless motor and a drive control circuit for the inverter are integrated into an integrated circuit together with the device. In the rotational position detection device according to claim 1 or 2 ,
The motor is a brushless motor;
An inverter for driving the brushless motor and a drive control circuit thereof are integrated with a stator of the brushless motor together with the apparatus.

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