JP2003047279A - Motor driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driver which can make phase compensation of middle point control using a capacitor of a capacitance value suitable for the phase compensation and can further take out accurate position signals to control the position of a motor and stabilize the operation of the motor. SOLUTION: In the motor driver, an output voltage for driving a motor 22 is generated at an output circuit 23. A reference voltage circuit 27 for position detection generates a reference potential for detecting the position of the motor based on the output voltage from the output circuit 23. A position detection comparator circuit 26 detects the position of the rotor based on the output voltage from the output circuit 23 and the reference potential from the reference voltage circuit 27 for position detection. A reference voltage circuit 24 for middle point control generates a reference voltage for effecting middle point control. A middle point control circuit 25 compares the reference voltage generated at the reference voltage circuit for middle point control with a specified comparison potential, and performs feedback control so that the reference voltage is matched with the comparison potential. The reference voltage circuit 27 for position detection and the reference voltage circuit 24 for middle point control are formed independently of each other.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a motor driver for driving a brushless motor. In particular, the present invention relates to a sensorless motor driver that drives a brushless motor used for rotating a spindle or the like.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a sensorless motor driver for driving a brushless motor, which has a function of midpoint control and position (rotor rotation angle) detection. FIG. 1 shows a part of a motor driver, which comprises a position detecting comparator circuit 1, a position detecting reference voltage circuit and a midpoint control reference voltage circuit 2, and a midpoint control circuit 3.

The position detecting comparator circuit 1 is composed of three comparators 4A, 4B and 4C. An output voltage for driving a motor, that is, a U-phase output, is provided to the inverting input terminals of the comparators 4A, 4B and 4C. , V phase output, W
The phase outputs are distributed and input.

The position detecting reference voltage circuit / middle point controlling reference voltage circuit 2 is formed by star-connecting three resistors 5A, 5B and 5C, and the position detecting comparator circuit 1 is provided.
The U-phase output, the V-phase output, and the W-phase output that are input to are distributed and input to the ends of the resistors 5A, 5B, and 5C. Also,
Each comparator 4A uses the midpoint potential of the position detection reference voltage circuit and the midpoint control reference voltage circuit 2 extracted from the node (middle point) of the star-connected resistors 5A, 5B, and 5C as a common reference potential Vref. Connect to the non-inverting input terminals of 4B and 4C.

The midpoint control circuit 3 applies a predetermined comparison potential Vo to the non-inverting input terminal of the operational amplifier 6, and the operational amplifier 6
The negative feedback resistor 7 is inserted between the output terminal and the inverting input terminal and the capacitor 8 for phase compensation is connected between the inverting input terminal and the ground. The output of the reference voltage circuit for position detection and the reference voltage circuit 2 for midpoint control is connected.

FIG. 2 shows the function of position detection extracted from the portion of the motor driver shown in FIG. The position detection reference voltage circuit (position detection reference voltage circuit / midpoint control reference voltage circuit 2) is based on the U phase output, V phase output, and W phase output input to the position detection comparator circuit 1. And outputs the midpoint potential (potential of the nodes of the resistors 5A, 5B, and 5C), and the midpoint potential is used as the common reference potential Vre.
It is input to each comparator 4A, 4B, 4C as f. From each of the comparators 4A, 4B, and 4C, a signal corresponding to the magnitude relation between the common reference potential Vref and the U-phase output, the V-phase output, and the W-phase output is output, and the sensorless motor driver uses the position detection comparator circuit 1 The position of the motor (rotational angle of the rotor) is determined based on the output signal of 1 to control the timing of the U-phase output, the V-phase output, and the W-phase output applied to the motor.

Since the sensorless motor driver does not input the position signal of the motor, the motor driving is realized by taking the output waveform itself for driving the motor as its own input signal as described above. When taking in, the reference potential and the output waveform are compared to generate a logic signal that is easy to process. The frequency of the U-phase output, the V-phase output, and the W-phase output is controlled based on this logic signal to smoothly rotate the motor.

Further, FIG. 3 shows the function of the midpoint control extracted from the portion of the motor driver shown in FIG. The midpoint control reference voltage circuit (position detection reference voltage circuit and midpoint control reference voltage circuit 2) is a U-phase output, a V-phase output, which is input to the position detection comparator circuit 1.
The midpoint potential (Vref) is output based on the W-phase output. The midpoint control circuit 3 performs feedback control so that the midpoint potential becomes the same potential as the predetermined potential Vo, whereby the noise during motor rotation can be reduced.

[0009]

In a motor driver, when the midpoint control and the motor position detection are performed at the same time, generally, the center connection of the motor for the position detection and the star connection by the resistance for the midpoint control are performed. Since the middle point is different, even if the middle point control and the position detection are performed at the same time, the motor operates stably and the noise of the motor can be reduced. However, in the case of the motor driver that attempts to artificially generate the midpoint potential of the motor by star-connecting the resistors as described above, there are the following problems.

Since the midpoint control circuit is a feedback control, the capacitor 8 for phase compensation is required to operate the midpoint control stably without causing oscillation.
Therefore, actually, as shown in FIG. 2, the capacitor 8 is added to the output of the position detection reference voltage circuit (position detection reference voltage circuit / midpoint control reference voltage circuit 2). If the reference potential Vref for position detection is stable, the position detection of the motor also operates stably, and therefore the capacitor 8 added for midpoint control is considered to operate effectively also for position detection.

However, in reality, since the midpoint control is feedback control, the phase compensating capacitor 8 becomes unstable if the capacitance value is too large or too small, and the capacitance value suitable for each motor is not appropriate. Will be needed.

Further, for position detection, the capacitor added to the midpoint potential is preferably as stable as possible, so that the larger the capacitance value, the more stable the operation. However, even if no capacitor is added, stable operation is achieved at a singular point.

FIG. 4 is a table summarizing the magnitude of the capacitance value of the capacitor 8 used in the motor driver and the suitability (O indicates good, X indicates defective) in applications for midpoint control and position detection. Is. For position detection, the capacitor has a large capacity or is not added at all (minimum)
Except the case, the fluctuation of the comparison potential Vo for position detection causes a phase delay due to the capacitor, and the U-phase output, the V-phase output, and the W-phase output cannot detect the phase at accurate timing.
There is a problem that the operation of the motor driver becomes unstable.

Further, when the current flowing through the motor is small, the capacitance value of the capacitor for stabilizing the reference potential for position detection and the capacitance value of the capacitor for phase compensation required for midpoint control are equal. Can be set to. However, the value of the current that flows in the motor may differ depending on the type of motor and the voltage applied to the motor, and if the current that flows in the motor is large, a large value may be necessary to stabilize the reference point for position detection. A capacitor having a capacitance value is required, and it is very difficult to achieve both a capacitor suitable for midpoint control and a capacitor suitable for position detection.

As a result, as can be seen from the table of FIG. 4, it is very difficult to select a capacitor having a capacitance value that makes both functions compatible, and in the table of FIG. It did not exist.

[0016]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the problems of the above-described conventional example, and an object of the present invention is to perform phase compensation for midpoint control by using a capacitor having a capacitance value suitable for phase compensation. Another object of the present invention is to provide a motor driver that can perform a stable position operation of a motor by taking out an accurate position signal and controlling the position of the motor.

A motor driver according to the present invention includes an output circuit for generating an output voltage for driving a motor, and a position detection for generating a reference potential for detecting a motor position based on the output voltage from the output circuit. Reference voltage circuit, a position detection circuit that detects the rotor position based on the output voltage from the output circuit and the reference potential of the position detection reference voltage circuit, and a reference voltage for performing midpoint control The midpoint control reference voltage circuit is compared with the reference voltage generated by the midpoint control reference voltage circuit and a predetermined comparison potential, and feedback control is performed so that the reference voltage becomes equal to the comparison potential. In a motor driver including a midpoint control circuit, the position detection reference voltage circuit and the midpoint control reference voltage circuit are formed separately from each other. .

In the motor driver according to the present invention, the reference voltage circuit for position detection and the reference voltage circuit for midpoint control are formed separately from each other, and therefore are used in the reference voltage circuit for position detection. Since the capacitance value of the position detection capacitor and the capacitance value of the phase compensation capacitor used in the midpoint control reference voltage circuit can be determined independently of each other, it is used in the position detection reference voltage circuit. The capacitance value of the capacitor for position detection is set to a value suitable for motor position detection, and the capacitance value of the capacitor for phase compensation used in the reference voltage circuit for midpoint control is suitable for midpoint control. Can be set to a value. Alternatively, when the position detection reference voltage circuit does not use a capacitor, the position detection reference voltage circuit is not affected by the capacitor used in the midpoint control reference voltage circuit. Therefore, according to the motor driver of the present invention, it is possible to stabilize the rotation of the motor by the function of the position detection reference voltage circuit while simultaneously achieving the noise reduction of the motor by the function of the midpoint control reference voltage circuit.

As a method of forming the position detection reference voltage circuit and the midpoint control reference voltage circuit separately from each other, for example, the position detection reference voltage circuit and the midpoint control reference voltage circuit may be formed separately from each other. It suffices that each component is configured as an individual component without having common components. When the position detection reference voltage circuit has a plurality of resistors connected in a star and the midpoint control reference voltage circuit has a plurality of resistors connected in a star and a capacitor, the reference voltage circuit for position detection is The midpoint control reference voltage circuit should not share at least the star-connected resistor and capacitor (including the case where the position detection reference voltage circuit does not have a capacitor).

The constituent elements of the present invention described above can be combined as much as possible.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 5 is a block diagram showing the configuration of a motor driver 21 according to an embodiment of the present invention. The motor driver 21 is a sensorless motor driver that does not have a sensor such as a Hall element for detecting the position of the rotor (which means an angle. The same applies hereinafter). The output circuit 23 and the reference voltage for midpoint control Circuit 24, midpoint control circuit 25, position detecting comparator circuit 26, position detecting reference voltage circuit 27, tilt circuit 28,
The V / I conversion circuit 29, the waveform synthesis circuit 30, and the mask signal generation circuit 31 are included in the midpoint control circuit 25.
Has a capacitor 32 for phase compensation. Further, FIG. 6 shows waveforms at various parts of the motor driver shown in FIG.

The motor 22 shown in FIG. 5 is a three-phase AC brushless motor, and has three coils connected in star connection inside. The output circuit 23 is shown in FIG.
U-phase output, V-phase output, and W-phase output voltages having waveforms as shown in (g) are applied to the coils of the motor 22, respectively, and the rotor is rotationally driven by the electromagnetic force generated in the coils.

Output circuit 23 applied to motor 22
The U-phase output, V-phase output, and W-phase output are fed back and input to the midpoint control reference voltage circuit 24, the position detection comparator circuit 26, and the position detection reference voltage circuit 27.

The midpoint control reference voltage circuit 24 is a circuit for generating and outputting midpoint potentials of U-phase output, V-phase output and W-phase output. As the midpoint control reference voltage circuit 24, specifically, three resistors having the same resistance value are star-connected, and a U-phase output, a V-phase output, and a W-phase output are applied to the ends of each resistor, and three resistors are connected. The output is taken from the midpoint (node) of the resistor (see the midpoint control reference voltage circuit in FIG. 3).

The midpoint control circuit 25 receives the midpoint potential generated by the midpoint control reference voltage circuit 24, compares the midpoint potential with a predetermined comparison potential, and midpoint control reference voltage circuit 24. Feedback control is performed so that the midpoint potential output from the control circuit becomes equal to the comparison potential, so that the midpoint potential of the U-phase output, V-phase output, and W-phase output does not fluctuate and is always maintained at a stable potential. It was done. As the midpoint control circuit 25, specifically, a predetermined comparison potential Vo is applied to the non-inverting input terminal of the operational amplifier, a negative feedback resistor is inserted between the output terminal and the inverting input terminal of the operational amplifier, and the inverting input is performed. A phase compensation capacitor is connected between the terminal and the ground, and the output of the midpoint control reference voltage circuit 24 is connected to the inverting input terminal of the operational amplifier (see the midpoint control circuit of FIG. 3). reference).

The position detecting comparator circuit 26 is composed of three comparators, and the U-phase output, the V-phase output and the W-phase output are input to one terminal of each comparator,
The common reference potential generated by the position detection reference voltage circuit 27 is input to the other terminal (see the position detection comparator circuit of FIG. 2).

The position detecting reference voltage circuit 27 is a circuit for generating a common reference potential required by the position detecting comparator circuit 26. Specifically, it is configured by connecting three resistors in a star connection, and the position detecting comparator circuit 2
The U-phase output, the V-phase output, and the W-phase output that are input to 6 are distributed and input to the ends of each resistor, and the output drawn from the node (middle point) of these resistors is used as the common reference potential Vref. It is input to the position detecting comparator circuit 26 (see the position detecting reference voltage circuit in FIG. 2). A capacitor may be connected between the output of the position detection reference voltage circuit 27 and the ground, if necessary.

In the position detecting comparator circuit 26,
Although not shown, the FG signal generator is provided,
The signal generation unit generates an FG signal. The FG signal indicates the rotation speed of the brushless motor 22 and has a waveform as shown in FIG.
It is used by a servo mechanism (not shown) or the like provided to keep the rotation speed of the drive stable.

The midpoint control reference voltage circuit 24 and the position detection reference voltage circuit 27 are configured separately, and in particular, the three resistors star-connected in the position detection reference voltage circuit 27 and the midpoint. In the control reference voltage circuit 24, the resistors are not shared with the three resistors that are star-connected, but are configured by completely different components.

The inclination circuit 28 is a circuit for generating triangular waves SL1 and SL2 as shown in FIG. 6E based on the output from the position detecting comparator circuit 26. The triangular wave generated by the gradient circuit 28 is converted into a voltage signal by the I / V conversion circuit 29. Based on this signal, the waveform synthesis circuit 3
From 0, waveforms of U-phase output, V-phase output, and W-phase output as shown in FIGS. 6A to 6C are output to the output circuit 23, and the output circuit 23 outputs to the motor 22 based on these waveforms. Voltages of U-phase output, V-phase output, and W-phase output are applied.

Further, the mask signal generation circuit 31 generates a mask signal as shown in FIG. 6 (f) by comparing the triangular wave with the FG signal. The mask signal becomes L level at the same timing as the noise generated in each signal waveform of U phase output, V phase output, W phase output, and when the mask signal becomes L level, the U phase output and V phase input to the output circuit 23. The output circuit 23 masks the output and W-phase output signal waveforms.
The noise is prevented from being transmitted from the motor 22 to the motor 22.

Therefore, according to such a motor driver, the position signal of the rotor is obtained based on the U-phase output, the V-phase output and the W-phase output applied to the motor 22 without using a sensor such as a Hall element. Can be generated.

Further, in this motor driver, the position detection reference voltage circuit 27 and the midpoint control reference voltage circuit 24 and the midpoint control circuit 25 are formed separately, so that the phase compensation of the midpoint control circuit 25 is performed. You can freely choose the capacitor you need. Further, the common reference voltage Vref of the position detection reference voltage circuit 27 can stably detect the position of the rotor without adding a capacitor, and the motor 22 can be stably rotated.

However, when noise is large when driving the motor, or when the power supply environment is bad, stable operation may not occur unless a capacitor is added to the output of the reference voltage circuit 27 for position detection. In such a case, stable operation can be achieved by adding a capacitor to the output of the position detection reference voltage circuit 27 and increasing the value sufficiently.

The motor driver is an IC, and the reference potential for midpoint control and the common reference potential for position detection are held inside the IC and have individual values. However, the capacitor 32 for phase compensation is externally attached to the IC. According to this motor driver, a common reference potential for position detection can be created using a resistor connected in a star inside the IC without using the midpoint potential inside the motor, and the harness drawn from the motor can be reduced, The driver can be miniaturized. Further, the number of IC terminals and the number of package terminals can be reduced, so that the motor driver can be downsized and the cost can be reduced. Further, since the chip size of the motor driver can be reduced, it is possible to reduce the size and cost of the bare chip mounting.

[0036]

According to the motor driver of the present invention, the position detection reference voltage circuit and the midpoint control reference voltage circuit are formed separately from each other, so that they are used in the position detection reference voltage circuit. Since the capacitance value of the position detection capacitor and the capacitance value of the phase compensation capacitor used in the midpoint control reference voltage circuit can be determined independently of each other, it is used in the position detection reference voltage circuit. The capacitance value of the capacitor for position detection is set to a value suitable for motor position detection, and the capacitance value of the capacitor for phase compensation used in the reference voltage circuit for midpoint control is suitable for midpoint control. Can be set to a value. Alternatively, if the position detection reference voltage circuit does not use a capacitor,
The reference voltage circuit for position detection is not affected by the capacitor used in the reference voltage circuit for midpoint control. Therefore, according to the motor driver of the present invention, it is possible to stabilize the rotation of the motor by the function of the position detection reference voltage circuit while simultaneously achieving the noise reduction of the motor by the function of the midpoint control reference voltage circuit.

[0037]

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a part of a conventional motor driver.

FIG. 2 is a diagram showing the function of position detection extracted from the portion of the motor driver shown in FIG.

FIG. 3 is a diagram in which the function of midpoint control is extracted from the portion of the motor driver shown in FIG.

FIG. 4 is a table showing the magnitude of the capacitance value of each capacitor used in the motor driver, and the suitability for use in midpoint control and position detection.

FIG. 5 is a block diagram showing a configuration of a motor driver according to an embodiment of the present invention.

6 is a diagram showing waveforms at various parts of the motor driver shown in FIG.

[Explanation of symbols]

22 motor 23 Output circuit 24 Midpoint control reference voltage circuit 25 Midpoint control circuit 26 Position detecting comparator circuit 27 Reference voltage circuit for position detection 32 capacitors

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H560 BB04 BB12 DA13 DA19 DB20                       DC13 JJ13 JJ15 SS01 TT07                       TT10 XA14

Claims (3)

[Claims] 1. An output circuit for generating an output voltage for driving a motor; a position detection reference voltage circuit for generating a reference potential for detecting a motor position based on an output voltage from the output circuit; A position detection circuit that detects the position of the rotor based on the output voltage from the output circuit and the reference potential of the position detection reference voltage circuit, and a midpoint control reference that generates a reference voltage for performing midpoint control. A voltage circuit, a midpoint control circuit that compares a reference voltage generated by the midpoint control reference voltage circuit and a predetermined comparison potential, and performs feedback control so that the reference voltage and the comparison potential become equal to each other; A motor driver comprising: the position detection reference voltage circuit and the midpoint control reference voltage circuit formed separately from each other. 2. The motor driver according to claim 1, wherein the position detection reference voltage circuit and the midpoint control reference voltage circuit do not have common components. 3. The position detection reference voltage circuit has a plurality of resistors connected in a star connection, and the midpoint control reference voltage circuit has a plurality of resistors connected in a star connection and a capacitor, The motor driver according to claim 1, wherein the reference voltage circuit and the midpoint control reference voltage circuit do not share a star-connected resistor and a capacitor.