JPH0898582A - Rotor position detector circuit for direct current brushless motor - Google Patents

Abstract

PURPOSE: To estimate the positions of the magnetic poles of a magnet rotor correctly by making only the terminal voltages of the stator windings effective when a chopper is off, only spike noises generated at the time of commutation, and extracting only induced voltages induced by the rotation of the magnet rotor from the terminal voltages. CONSTITUTION: The terminal voltage Va of a stator winding 11 has the superposed waveform of a spike noise generated at the time of commutation and a power voltage applied to the stator winding 11. This terminal voltage Va is divided by a voltage divider circuit 31a, and only an induced voltage is extracted from the terminal voltage Va, by switching an induced voltage extracting circuit 32a at the same timing as the switching elements T1-T3 of an inverter circuit 2 by a chopper signal obtained by a chopper signal synthesizing circuit 36. The induced voltage waveform extracted in this way is a signal without a spike noise generated at the time of commutation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor rotor position detection circuit for detecting the magnetic pole position of a DC brushless motor rotor from an induced voltage induced in a stator winding.

[0002]

2. Description of the Related Art As a conventional rotor position detection circuit for a sensorless brushless motor, a band pass filter (BPF) is used to compare a phase delay waveform of the filter with an average value of three-phase components of a filter output voltage. Has proposed a control method of an inverter circuit that creates commutation timing of a brushless motor and performs commutation based on this timing (see, for example, Japanese Patent Publication No. 58-25038).

[0003]

In the above-mentioned prior art,
The phase delay waveform of the induced voltage of the brushless motor is created by using a filter, but if the rotor pulsation occurs due to load fluctuations, the phase delay of the filter becomes inaccurate or the motor load is large. When the motor return current flows under the conditions, the time during which the terminal voltage of the stator winding becomes equal to the DC voltage of the inverter increases, and waveform distortion occurs in the filter output voltage after filtering the induced voltage of the motor. There is an inconvenience, and when the load of the motor is fluctuating or when the motor is overloaded, the position of the rotor cannot be detected correctly, and the motor may be out of step.

An object of the present invention is to accurately estimate the magnetic pole position of the rotor when the load of the motor is fluctuating and when the return current flows for a long time due to an increase in the load, and the rotor magnetic pole position is rotated at an appropriate timing. Another object of the present invention is to provide a rotor position detection circuit that can perform flow.

[0005]

According to the present invention, a plurality of switching elements are connected in a bridge shape through a magnet rotor, a star-shaped stator winding, and a DC power source to fix the output end thereof. In a DC brushless motor having a chopper control type inverter circuit connected to each phase of the child winding, spikes generated during commutation by enabling only the terminal voltage of the stator winding when the chopper is off The noise is removed, and only the induced voltage induced by the rotation of the magnet rotor is extracted from the terminal voltage.

In this case, the means for extracting the induced voltage is such that the terminal voltage of the stator winding is divided by the voltage dividing circuit and then connected to the ground via the switching element, and the switching element is turned on when the chopper is on. Is turned on to remove the power supply voltage applied as a terminal voltage to the stator winding.

Further, in this case, the frequency of the chopper is adjusted so that the resolution of the induced voltage becomes constant regardless of the rotation speed of the motor, and when the rotation speed of the motor is high, the frequency of the chopper is increased to increase the rotation speed of the motor. Adjust to lower the chopper frequency when is low.

Further, in this case, the chopper for extracting the induced voltage uses a single drive signal for driving the switching element on the current supply side among the plurality of switching elements. Further, in this case, an amplification circuit for amplifying the extracted induced voltage is provided, and the amplification circuit can switch the amplification factor in several steps so that the induced voltage whose size changes in accordance with the rotation speed of the motor becomes a constant size. adjust.

Further, in this case, an amplification circuit for amplifying the extracted induced voltage is provided, and this amplification circuit is set to a large amplification factor so that the output is always saturated even with a small induced voltage at low rotation. In this case, the extracted induced voltage is passed through an integrator circuit so that the induced voltage does not drop to the ground level during the induced voltage generation period, and the output signal of the integrator circuit is compared with a threshold slightly higher than the ground level. By doing so, the position signal of the rotor is obtained.

Further, in this case, the chopper signal used in the inverter circuit is always turned on when the drive signal is switched so that the chopper signal is turned on whenever spike noise is generated during commutation. Control so that the chopper signal starts at the timing of turning on.

[0011]

In the configuration of the present invention, only the terminal voltage when the chopper is off is taken out, so spike noise generated during commutation is removed, and the time during which the motor return current flows under a large motor load becomes longer. However, it will not be affected by it. Further, since the position signal is created by extracting only the induced voltage induced by the rotation of the magnet rotor from the terminal voltage, even if the rotor pulsation occurs due to load fluctuation, etc., the induced voltage is generated by this rotation pulsation. Also changes, so an accurate position signal can always be obtained,
Commutation can be performed at an appropriate timing.

[0012]

FIG. 1 is a block diagram showing an embodiment of a rotor position detecting circuit for a DC brushless motor according to the present invention.
It is shown together with the motor body and the inverter circuit. It is assumed that the terminals denoted by circled numbers in the figure are connected to each other.

In the figure, the motor body 1 is composed of a stator winding 11 and a rotor 12 which are three-phase star-connected. Further, the inverter circuit 2 has a DC power source DC,
It is composed of switching elements T1 to T6 having a three-phase bridge configuration of A, B, and C phases, and free wheeling diodes D1 to D6 connected in parallel to the switching elements T1 to T6.

The rotor position detection circuit 3 includes a stator winding 11
Voltage dividing circuit 31 for dividing each terminal voltage Va, Vb, Vc of
a, 31b, 31c and induced voltage extraction circuits 32a, 32 for validating only the terminal voltage when the chopper is off.
b, 32c, amplification circuits 33a, 33b, 33c for amplifying the induced voltage when the rotational speed is low and the induced voltage is small, and an integral for preventing the voltage from dropping to the ground level while the induced voltage is generated. Circuits 34a, 34b, 34c
And the output waveforms of the integration circuits 34a to 34c are compared with a threshold value slightly higher than the ground level to detect the position signals D1 to D1.
Three drive signals J1, J2, J3 for driving the switching elements T1 to T3 on the current supply side to supply the chopper signals to the comparison circuits 35a, 35b and 35c which output D3 and the induced voltage extraction circuits 32a to 32c. It is composed of a chopper signal synthesizing circuit 36 which is put together.

In this configuration, in order to start the motor body 1, the switching elements T1 to T6 of the chopper control type inverter circuit 2 are turned off in a predetermined order to sequentially energize each phase of the stator winding 11. The control operation for forcibly rotating the rotor 12 is performed to increase the rotation speed to a predetermined rotation speed (for example, 500 rpm).

The chopper signal used in the inverter circuit 2 is controlled so that it always starts from the timing when the chopper is turned on when switching the drive signal, and the chopper signal is turned on whenever spike noise occurs during commutation. So that After that, the normal operation is performed in which the switching elements T1 to T6 of the inverter circuit 2 are turned on and off at any time by the position signals D1 to D3 of the rotor position detection circuit 3. This will be described with reference to the waveform chart shown in FIG.

FIG. 2 shows the position detection circuit 3 in normal operation.
Waveform of each part of the stator winding 11 for one phase (for example, A
Phase), and FIG. 3A shows 3 which drives the switching elements T1 to T3 on the current supply side of the inverter circuit 2.
This is a chopper signal in which the two drive signals J1 to J3 are combined into one by the chopper signal synthesis circuit 36.

When the rotor 12 rotates due to the interruption of the conduction of the inverter circuit 2, an induced voltage is induced in the stator winding 11. The terminal voltage Va generated in the stator winding 11 is shown in FIG.
As shown in (3), the induced voltage has a waveform in which the power supply voltage applied to the stator winding 11 when the chopper is on and the spike noise generated during commutation are superimposed.

The terminal voltage Va is divided by the voltage dividing circuit 31a, and the induced voltage extracting circuit 32a is generated at the same timing as the switching elements T1 to T3 of the inverter circuit 2 by the chopper signal (FIG. A) obtained by the chopper signal synthesizing circuit 36. As shown in FIG. 7C, only the induced voltage is extracted from the terminal voltage Va by switching. Since the resolution of the induced voltage extracted at this time is determined by the frequency of the chopper, by changing the frequency of the chopper according to the rotation speed, the resolution of the induced voltage should be adjusted to be constant regardless of the rotation speed. May be.

The induced voltage waveform thus extracted (Fig. C)
Is a signal from which spike noise generated during commutation has been removed. By the way, since the induced voltage also decreases when the rotation speed of the motor body 1 is small, it is amplified to a sufficient size by the amplification circuit 33a and then passed through the integration circuit 34a,
As shown in FIG. D, the voltage is prevented from dropping to the ground level while the induced voltage is generated.

At this time, the configuration of the amplifier circuit 33a is shown in FIG.
As shown in FIG. 5, if the switch SW is used to switch the connection with the resistors R1 to R4 so that the amplification factor is switched stepwise, the amplification factor is switched according to the rotation speed of the motor body 1, and the induced voltage is kept constant. The signal processing may be performed after adjusting the size of the signal. At this time, even if the amplification factor of the amplification circuit 33a is made large so that the output of the amplification circuit 33a is saturated even with a small induced voltage at low rotation, signal processing may be performed using the saturated output signal. Good.

Then, the output waveform of the integrator circuit 34a (Fig. D) is compared with a threshold value slightly higher than the ground level by the comparator circuit 35a to obtain the rotor position signal D1 as shown in Fig. E. In the normal operation, the timing at which the switching element of the inverter circuit 2 is turned off is determined by the position signal.

FIG. 4 shows the terminal voltages Va to Vc and the position signal D.
1 to D3 and drive signals J1 to J6 are shown in timing charts. Here, the drive signals J1 to J3 of the switching elements T1 to T3 on the current supply side of the inverter circuit 2 are switched by the rising edges of the position signals D1 to D3, and the switching elements on the current drawing side are switched by the falling edges of the position signals D1 to D3. Drive signal J4 from T4 to T6
~ J6 is switched.

Further, the timing of the falling edges of the position signals D1 to D3 coincides with the switching timing of the drive signal of the switching element, but the timing of the rising edge of the position signal is more than the switching timing of the drive signal of the switching element. Since the electrical angle is about 60 ° ahead, the drive signal is switched after delaying that time. Since the position signal has a time width of 240 ° in electrical angle, the delay time can be easily obtained from this time width.

[0025]

According to the present invention, since only the terminal voltage when the chopper is off can be taken out, spike noise generated at the time of commutation is removed, so that the motor recirculation occurs under a large motor load. Even if the current flows for a long time, it will not be affected by it.

Further, since only the induced voltage induced by the rotation of the magnet rotor is extracted from the terminal voltage to generate the position signal, even when the rotor pulsation is generated due to load fluctuation or the like, this rotational pulsation is generated. Since the induced voltage also changes due to this, an accurate position signal can always be obtained, and commutation can be performed at an appropriate timing.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a rotor position detection circuit for a DC brushless motor according to the present invention, together with a motor body and an inverter circuit.

2A to 2E are waveform charts showing waveforms of respective portions of a rotor position detection circuit.

FIG. 3 is another embodiment of an amplifier circuit in which the amplification factor can be switched to a plurality of stages.

FIG. 4 is a timing diagram of terminal voltages, position signals, and drive signals.

[Explanation of symbols]

 1 Motor Main Body 2 Inverter Circuit 3 Rotor Position Detection Circuit 31a to 31c Voltage Dividing Circuit 32a to 32c Induced Voltage Extraction Circuit 33a to 33c Amplifying Circuit 34a to 34c Integrating Circuit 35a to 35c Comparison Circuit 36 Chopper Signal Combining Circuit

Claims (8)

[Claims] 1. A magnet rotor, a stator winding connected in a star shape, and a plurality of switching elements are connected in a bridge shape via a DC power source, and an output end thereof is connected to each phase of the stator winding. In a DC brushless motor having an inverter circuit of a chopper control system connected to each, while removing the spike noise generated during commutation by validating only the terminal voltage of the stator winding when the chopper is off, A rotor position detection circuit for a DC brushless motor, wherein only the induced voltage induced by the rotation of the magnet rotor is extracted from the terminal voltage. 2. The means for extracting the induced voltage divides the terminal voltage of the stator winding by a voltage divider circuit, and then connects it to the ground via a switching element. When the chopper is on, 2. The rotor position detecting circuit for a DC brushless motor according to claim 1, wherein the power source voltage applied to the stator winding as the terminal voltage is removed by turning on a switching element. 3. The frequency of the chopper is adjusted so that the resolution of the induced voltage becomes constant regardless of the rotation speed of the motor, and the frequency of the chopper is increased when the rotation speed of the motor is high, 2. The rotor position detection circuit for a DC brushless motor according to claim 1, wherein the frequency of the chopper is adjusted to be low when the rotational speed of the rotor is low. 4. The chopper for extracting the induced voltage uses a combination of drive signals for driving a switching element on a current supply side among the plurality of switching elements. A rotor position detection circuit for a DC brushless motor according to 1 or 2. 5. An amplifying circuit for amplifying the extracted induced voltage is provided, and the amplifying circuit is capable of switching the amplification factor in several stages so that the induced voltage whose magnitude changes according to the rotation speed of the motor is constant. The rotor position detection circuit for a DC brushless motor according to claim 1, wherein the rotor position detection circuit is adjusted to a size. 6. An amplification circuit for amplifying the extracted induced voltage is provided, and the amplification circuit is set to have a large amplification factor so that the output is always saturated even with a small induced voltage at low rotation. A rotor position detection circuit for a DC brushless motor according to claim 1. 7. The extracted induced voltage is passed through an integrating circuit so that the induced voltage does not drop to the ground level during the generation period of the induced voltage, and the output signal of the integrating circuit is set to be slightly lower than the ground level. The rotor position detection circuit for a DC brushless motor according to claim 1, wherein the position signal of the rotor is obtained by comparing with a high threshold value. 8. The chopper signal used in the inverter circuit is always the chopper signal when switching the drive signal so that the chopper signal is always turned on when spike noise occurs during commutation. 2. The rotor position detection circuit for the DC brushless motor according to claim 1, wherein the control is performed so that the timing of turning on is started.