JPH0746877A - Brushless motor drive circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a drive circuit of a brushless motor that can significantly reduce power consumption and can increase the rotational speed of the brushless motor. A voltage waveform (U phase, V phase) based on signals WA, WB, WC obtained from position detection sensors 31, 32, 33 for detecting the position of a rotor 10 of a brushless motor.
Phase, W phase) is formed, the driving voltage waveform D1 is synthesized by utilizing the slope portion Q of this voltage waveform, and the voltage at the position where the adjacent voltage waveforms (U phase, V phase, W phase) cross each other. The output voltage of the drive voltage waveform D1 is amplified by the output transistor 50 such that the difference A between the voltage VC and the midpoint voltage VM of the amplitude of the voltage waveform becomes a constant ratio with respect to the voltage of the amplitude B of the voltage waveform. A drive circuit for driving a brushless motor, wherein the amplitude B of the drive voltage waveform D1 is increased until the output transistor 50 is saturated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a brushless motor drive circuit.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional drive circuit for a brushless motor. A conventional brushless motor includes a stator having a coil and a rotor rotating with respect to the stator.

In order to detect the rotational position of the rotor with respect to the stator, Hall elements 1, 2, ...
3 is used as a sensor for detecting the rotor position.

The drive circuit of the conventional brushless motor shown in FIG. 6 is as follows. The three signals having different phases obtained from the Hall elements 1, 2 and 3 are respectively amplified by the output transistor 4 which is the first stage amplifier, and are further combined by the waveform combining section 5. Then, in order to form the drive voltage waveform D as shown in FIG. 7 by the amplitude controller 6, it is necessary to provide the circuit 8 for producing the remaining voltage so that the transistor 7 in the output stage operates in the active region.

That is, in the drive voltage waveform D of FIG. 7, the sloped portions Q in each voltage waveform of the adjacent U-phase signal, V-phase signal, and W-phase signal are used, and three sloped portions Q are crossed so as to intersect each other. The phase voltage waveforms are combined. The reason why the three-phase voltage waveforms are combined in this way is to reduce the torque ripple of the brushless motor. The amplitude B of the drive voltage waveform D in this case can be expressed by Equation 1.

[0006]

[Equation 1]

Further, the amount of overlap (%) of the U-phase, V-phase, and W-phase voltage waveforms can be expressed by Equation 2.

[0008]

[Equation 2]

In FIG. 7, adjacent U-phase signal, V-phase signal, W
The amplitude control unit 6 controls the U-phase signal and the V-phase so that the difference A between the voltage VC at which the phase signals intersect and the midpoint voltage VM of the amplitude of the drive voltage waveform D becomes a constant ratio with respect to the amplitude B. Signal, W
The combined drive voltage waveform D including the phase signal is amplified to control the upper and lower slices.

That is, in this conventional method, the synthesized U
The target overlap amount is obtained by amplifying the amplitudes of the voltage waveforms of the V-phase, V-phase, and W-phase so as to have the amplitude B as shown in Formula 1, and performing the upper and lower slice control. It should be noted that VXH in Expression 1 represents the upper residual voltage, and VXL represents the lower residual voltage.

[0011]

However, in the drive circuit of this type of brushless motor, since the drive voltage waveform D as shown in FIG. 7 is output, the upper residual voltage VXH and the lower residual voltage VXH are reduced by the circuit 8 for generating the residual voltage. The side residual voltage VXL must be provided. That is, by applying this residual voltage, the transistor 7 in the output stage of FIG. 6 is operated only in its active region, and the desired drive voltage waveform D is obtained.

Therefore, by dropping the remaining voltages VXH and VXL in the drive circuit, power is consumed in the lowered portion, that is, the power consumption of the transistor 7 in the output stage is increased. There was a problem. Moreover, since the voltage drop inside the drive circuit is large in this way, the voltage applied to the motor becomes small, and the rotation speed and torque of the motor cannot be increased.

The present invention has been made in order to solve the above problems, and can significantly reduce the power consumption,
Moreover, it is an object of the present invention to provide a brushless motor drive circuit capable of increasing the rotational speed of the brushless motor.

[0014]

According to the present invention, a voltage waveform is formed based on a signal obtained from a position detection sensor for detecting the position of a rotor of a brushless motor, and the voltage waveform is formed. The driving voltage waveforms are synthesized by using the inclined portion of the voltage waveform, and the difference between the voltage at the position where the adjacent voltage waveforms intersect and the voltage of the amplitude of the voltage waveform is constant with respect to the voltage of the amplitude of the voltage waveform. Power drive the drive voltage waveform by the output transistor so that
In the drive circuit for driving the brushless motor,
This is achieved by a brushless motor drive circuit configured to increase the amplitude of the drive voltage waveform until the output transistor is saturated.

Further, in the present invention, preferably, the position detection sensor is a Hall element. Further, in the present invention, the signals obtained from the position detection sensor are preferably three signals having different phases.

[0016]

[Function] Not only the active region of the output transistor 50,
The saturation region of the output transistor 50 is also used to operate the output transistor 50 to reduce the power consumption of the output transistor 50.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

The motor of FIG. 1 is, for example, a general VTR.
The brushless motor 1 is used for a magnetic tape, and is used, for example, for conveying a magnetic tape. This motor is a plane-opposed motor in which the rotor portion 10 and the stator portion 20 face each other.

First, the structure of the rotor section 10 will be described. The rotor unit 10 includes a magnet 11 that is a permanent magnet,
It has a disk-shaped rotor yoke 12, a rotor boss 14, and a shaft 15.

A magnet 11 is attached to the inner surface of the rotor yoke 12. In this magnet 11,
The N pole and the S pole are magnetized in multiple poles. This rotor yoke 1
A shaft 15 is attached to 2 via a rotor boss 14.

Next, the stator section 20 will be described.
The stator portion 20 of FIG. 1 has a stator yoke 21. On the stator yoke 21, a plurality of exciting coils 22 arranged to face the main magnet 11 described above are fixed.

In the example of FIG. 1, the exciting coils 22 are arranged in six circular shapes. By sequentially supplying an exciting current to these exciting coils 22, the rotor unit 10 can be rotated. Hall elements 31, 32, 33 for rotor position detection are arranged in the three exciting coils 22 of the six exciting coils 22, respectively.

The stator yoke 21 is provided with a housing 24, and the bearing 23 of the housing 24 has
The shaft 15 of the rotor unit 10 is set to be rotatable.

FIG. 2 shows a drive circuit for driving the brushless motor as described above. The drive circuit 100 for the brushless motor is connected between the Hall elements 31, 32, 33 for detecting the rotor position and the six motor coils 22.

The three hall elements 31, 32, 33 are powered by the hall power source 40.
The Hall elements 31, 32, and 33 are connected to the transistors 42 of the three first-stage amplifiers, respectively. The transistor 42 of the first stage amplifier is connected to the first stage amplifier gain setting resistor 52.

The transistors 42 of the three first-stage amplifiers are
It is connected to the amplitude controller 46 via the waveform synthesizer 44. The signals obtained from the Hall elements 31, 32, and 33 are amplified by the transistors 42, 42, and 42 of the first-stage amplifier, and are converted into signals WA, WB, and WC by the waveform synthesizing unit 44.
It is designed to be input to.

These three signals WA, W having different phases
B and WC are synthesized by the waveform synthesizing unit 44 and further amplified by the amplitude control unit 46, so that the output stage is sliced up and down.

The gain control section 48 is composed of the amplitude control section 46.
Is connected to the control circuit, and serves to control how much the amplitude control section 46 should amplify in order to obtain a desired drive voltage waveform.

The gain controller 48 is connected to the reference voltage VS. The reference voltage VS is connected to each of the three output stage transistors 50. Further, the amplitude control section 46 is connected to each of the three output stage transistors 50. The transistors 50 in these output stages are connected to the power GND.

The transistors 50 in each output stage are connected to the motor coils 22 and 22, respectively. Two motor coils 22, 22 of the six motor coils are shown as one motor coil.

Next, referring to FIGS. 3A to 3F, from signals WA, WB and WC of FIG. 2 to U shown in FIG.
A method of forming the drive voltage waveform D1 including the V phase, the V phase, and the W phase will be described.

In FIG. 2, Hall elements 31, 32, 3
The position signals from 3 are differentially input to the transistors 42, 42, 42, which are the first-stage amplifiers of the drive circuit 100, respectively. The position signal input by this differential is
Amplified signals WA, W amplified by the transistor 42 in the first stage
B and WC. These amplified signals WA, WB, WC
Are combined by the waveform shaping section 44, and the amplitude control section 46
Controls the amplitude.

Therefore, first, the processing in the waveform synthesizing section 44 will be described. As an example, FIG. 3 shows a voltage waveform for one phase of the drive voltage waveform D1 shown in FIG. 4 based on the amplified signals WA and WB obtained from two Hall elements among these Hall elements 31, 32 and 33. It shows a method of molding the U phase. Therefore, the other voltage waveforms V and W can be similarly shaped.

As an example, the waveform shown in FIG.
Amplified signal (Hall A phase signal) WA from the Hall element 31
Similarly, the waveform shown in FIG. 3B is shown as an amplified signal (Hall B-phase signal) WB from the Hall element 31. .

As shown in FIG. 3C, the waveform synthesizer 44 of FIG. 2 slices the upper and lower waveforms of the Hall element A phase WA at a constant level. Similarly, the waveform synthesizer 4 of FIG.
As shown in FIG. 3D, 4 slices the upper and lower waveforms of the Hall element A phase WA at a constant level. By this slice shaping, an A-phase slice waveform SWA and a B-phase slice waveform SWB are formed. At this time, the B-phase slice waveform S
WB has been inverted.

The A-phase slice waveform SWA and the inverted B-phase slice waveform SWB are added together by the waveform synthesizing section 44 shown in FIG. 2 as shown in FIG.
The waveform thus added is formed into a voltage waveform having an amplitude Y proportional to the reference voltage VS shown in FIG. 1 by the amplitude control section 46 shown in FIG.
(F) is sliced.

The waveform shown in FIG. 3F obtained in this way is the U phase shown in FIG. Similarly, the remaining V phase and W phase shown in FIG. 4 are formed to form the drive voltage voltage waveform D1 shown in FIG. As shown in FIG. 4, adjacent Us
The voltage waveforms MU, MV, and MW of the phase, the V phase, and the W phase are set so as to overlap each other so as to have a desired overlap amount. By this setting, finally, the drive voltage waveform D1 is
Power amplification is performed by the transistor 50 of the output stage shown in (1) and sent to each motor coil 22 to drive the brushless motor.

The drive circuit of the embodiment of the present invention shown in FIGS. 2 and 3 is different from the conventional drive circuit system shown in FIG.

In the conventional drive circuit system shown in FIG. 6, the synthesized output voltage waveform D shown in FIG. 7 is constituted by a voltage range obtained by removing the upper residual voltage and the lower residual voltage from the voltage VS. Based on that assumption, the desired overlap amount can be obtained. However, in this conventional method, since the transistor of the output stage is operated only in the active region, the voltage corresponding to this remaining voltage is dropped inside the transistor of the output stage, resulting in large power consumption.

On the other hand, the drive circuit according to the embodiment of the present invention is characterized in that the amplitude B of the output voltage waveform D1 shown in FIG.
Is the collector-emitter voltage V of the upper and lower transistors.
The point is that it is determined by the point where CE is saturated (saturation voltage is indicated by VCESAT).

At this time, the target overlap amount (A / B ×
Since it is necessary to obtain 100%), the amplification amount in the amplitude control unit 46 is set as follows. That is,
Collector-emitter saturation voltage Vces of the output stage transistor 50 at the operating point (specification of the motor current) at which it is necessary to obtain a desired overlap amount from the value of the drive voltage VS.
For the voltage value obtained by subtracting at, the amplitude control unit 46 is provided so as to obtain a waveform that can secure a desired overlap amount.
The amplification amount at is set.

That is, the amplitude control section 46 makes sure that the voltage of the flat portion above and below the target drive voltage waveform becomes a voltage determined by the saturation of the output stage transistor 50.
That is, the gain of is set.

By the way, in rotating the brushless motor shown in FIG. 1, in order to reduce the torque ripple so that the brushless motor can be smoothly rotated, a certain amount of overlap suitable for the brushless motor used is provided. It is important to drive the brushless motor with the output voltage waveform (driving voltage waveform).

Therefore, in the embodiment of the present invention, assuming that the overlap amount to be set is X% and the amplitude of the drive voltage waveform of FIG. 3E is Y, the combined waveform of FIG. By symmetrically amplifying under the condition shown in Formula 3, a desired output voltage waveform (driving voltage waveform) can be obtained.

[0045]

[Equation 3]

However, in Equation 3, VCESAT
Shows the saturation voltage between the collector and the emitter of the transistor 50 in the output stage of FIG. 2 as described above.

As described above, in the embodiment of the present invention, the voltage waveform is based on the signals WA, WB, WC obtained from the position detection sensors 31, 32, 33 for detecting the position of the rotor 10 of the brushless motor. MU, MV, MW
(Corresponding to U phase, V phase, W phase), and this voltage waveform M
Each voltage waveform MU, using the inclined portion Q of U, MV, MW,
The drive voltage waveform D1 is synthesized by superimposing MV and MW.

The adjacent voltage waveforms MU, MV, MW
Vertical drive so that the difference A between the voltage VC at which (U-phase, V-phase, W-phase) intersects and the midpoint voltage VM of the amplitude of the voltage waveform becomes a constant ratio with respect to the amplitude B of the voltage waveform. The voltage waveform D1 is controlled.

Moreover, the amplitude B of the drive voltage waveform D1 is increased until the output transistor 50 is saturated.
That is, not only the active region of the output transistor 50,
The saturation region of the output transistor 50 is also used to operate the output transistor 50 to control the drive voltage waveform of the brushless motor.

As described above, the embodiment of the present invention does not require the conventional circuit for producing the remaining voltage. Moreover, the drive voltage waveform D1 of FIG.
When the power is amplified by 0, not only the active region of the transistor 50 but also the saturation region is used. Therefore, the drop voltage (drop voltage) of the collector-emitter voltage VCE of the transistor 50 at the output stage of the drive circuit is reduced. You can Therefore, when the same current flows, the smaller the collector-emitter voltage VCE, the more the power consumption of the transistor 50 in the output stage can be significantly reduced.
Therefore, the power consumption of the drive circuit 100 including these output stage transistors 50 can be significantly reduced.

In this way, the voltage drop due to the output-stage transistor can be reduced, and conversely, the voltage applied to the motor is increased, and the rotation speed and torque of the motor can be increased as compared with the conventional case.

The present invention is not limited to the above embodiment. For example, in accordance with the drive voltage VS, the amplitude control unit 4
The amplification amount of 6 can be changed. Further, by providing the resistor 120 from the output stage transistor 50 to the ground as shown in FIG. 5, the amplification amount of the amplitude control unit 46 can be changed according to the output current of the output stage transistor 50. . As a result, good characteristics can be obtained in a wide band.

[0053]

As described above, according to the present invention, the power consumption of the drive circuit can be greatly reduced, and
The rotation speed of the motor can be increased.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an example of a brushless motor driven by a brushless motor drive circuit according to the present invention.

FIG. 2 is a diagram showing a preferred embodiment of a drive circuit for a brushless motor according to the present invention.

FIG. 3 is a diagram showing a U phase which is one of drive voltage waveforms which are combined and amplitude-controlled by the drive circuit of the brushless motor of FIG.

FIG. 4 is a diagram showing drive voltage waveforms obtained by superposing U-phase, V-phase, and W-phase having different phases.

FIG. 5 is a diagram showing another preferred embodiment of the drive circuit of the brushless motor of the present invention.

FIG. 6 is a diagram showing a drive circuit of a conventional brushless motor.

7 is a diagram showing drive voltage waveforms obtained by superposing U-phase, V-phase, and W-phase having different phases in the drive circuit of the conventional brushless motor shown in FIG.

[Explanation of symbols]

 10 rotor 20 stator 22 coil 31, 32, 33 rotor position detecting hall element 42 first stage amplifier transistor 44 waveform synthesizing section 46 amplitude control section 50 output stage transistor 100 brushless motor drive circuit Q voltage waveform ramp section A crossing Difference between the applied voltage and the midpoint voltage B Amplitude MU, MV, MW Voltage waveform VC Crossing voltage VM Midpoint voltage

Claims (3)

[Claims] 1. A voltage waveform is formed on the basis of a signal obtained from a position detection sensor for detecting the position of a rotor of a brushless motor, and a driving voltage waveform is synthesized by utilizing an inclined portion of this voltage waveform. The drive voltage waveform is controlled by the output transistor so that the difference between the voltage at the position where the adjacent voltage waveforms intersect and the midpoint voltage of the amplitude of the voltage waveform becomes a constant ratio with respect to the voltage of the amplitude of the voltage waveform. 2. A drive circuit for driving a brushless motor for power amplification of a brushless motor, wherein the amplitude of the drive voltage waveform is increased until the output transistor is saturated. 2. The drive circuit for a brushless motor according to claim 1, wherein the position detection sensor is a Hall element. 3. The drive circuit for a brushless motor according to claim 1, wherein the signals obtained from the position detection sensor are three signals having different phases.