JPH0243439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless DC motor in which transistors sequentially switch power supply to coils of multiple phases according to the position of a movable part of the motor.

Brushless DC motors have low torque ripple, no brush noise, and long life, so they are used in a variety of audio and video equipment. For example, recently they have been used as reel motors in tape recorders by being directly connected to reel drive shafts. In the case of a reel motor, high-speed rotation with a short startup time is required during early winding, and the current supplied to the motor is set to be large. In this case, the back electromotive voltage increases as the rotation of the motor increases, causing the drive transistor to become excessively oversaturated, resulting in unstable circuit operation and an increase in current ripple. Current ripples have become a major problem because they cause ripples in the generated torque, causing vibration and noise in the motor.

In addition, in a speed-controlled motor, the drive transistor becomes oversaturated at the time of start-up acceleration, causing vibrations and noise, as well as deteriorating control pull-in characteristics, posing a problem.

In addition, Japanese Patent Publication No. 55-6938 states that in such a brushless DC motor, current is passed in both directions to the star-connected three-phase coil (full-wave drive).
It is disclosed that the utilization efficiency of the coil is improved by doing so. According to this, a constant current is supplied to the multiphase coils by a first drive transistor group, and a potential at a common connection point of the multiphase coils is brought to a predetermined value by a second drive transistor group. The coil supplies current in both directions. In a brushless DC motor with such a configuration, when the drive transistor reaches a saturated state, a considerably large current flows directly from the second drive transistor to the first drive transistor, resulting in current breakdown and ASO breakdown of the drive transistor, as well as shortened lifespan. There was a fear and it was a problem.

The present invention aims to improve such problems by detecting the operating voltage of the drive transistor when it is energized, and changing (correcting) the current supplied to the coil based on the detection signal. This is to prevent excessive saturation.

The present invention will be explained below based on the illustrated embodiments. FIG. 1 is an electrical circuit diagram representing an embodiment of the present invention. In Figure 1, 1 is a DC power supply, 3,
4 and 5 are first driving transistors; 6, 7, and 8 are three-phase coils; 9 is a field magnet; and a portion 11 surrounded by a broken line is a Hall element 41, 42, 43 that senses the magnetic flux of the magnet 9. ,44,45,46
12 is a position detector 1 for detecting the rotational position of the magnet 9 (motor movable part).
1, the first drive transistor 3,
a first distribution controller that distributes and controls energization of 4 and 5;
13, 14, and 15 are connected in series to the current path formed by the coils 6, 7, and 8 and the first drive transistors 3, 4, and 5 (each input terminal is connected to the power supply side, and each output terminal is connected to the first drive transistor). A second drive transistor (16) (connected to each output terminal of the drive transistors 3, 4, 5) responds to the output of the position detector 11 to
18 is an operation detector that detects the operating voltage when the second drive transistors 13, 14, 15 are energized. Also, 21,2
2 is a DC voltage source, 23 is a command signal, 24 is a current converter that outputs a current i ₁ corresponding to the command signal 23,
Reference numeral 19 denotes a similar current generator that generates currents i ₂ , i ₃ , i ₄ in response to the output current i ₁ of the current converter 24 .

Next, its operation will be explained. Command signal 2
3 is obtained by a speed detection means consisting of a frequency generator and a period/voltage converter, for example, and changes depending on the rotational speed of the motor movable part (rotor). The current converter 24 is composed of, for example, a differential amplifier and a voltage-current converter, and receives the command signal 23 and the voltage source 2.
Compare the voltage values of 2 and calculate the current according to the difference between the two.
i Output (suction) ₁ . The output i ₁ of this current converter 24 is input to a similar current generator 19 . Similar current generator 19 includes transistors 25, 26, 27,
28, 29, resistors 30, 31, 32, 33, and a second current mirror consisting of diode 34, transistor 35, and resistors 36, 37.
A current i ₂ similar (proportional or nearly proportional) to the output i ₁ of
Outputs i ₃ and i ₄ . The current i ₂ is the first distribution controller 1
The current _i3 is converted into a voltage signal _V2 by the resistor 61 and diodes 62, ₆₃ of the second distribution controller 16.
The current i ₄ flows through the diodes 81 and 8 of the motion detector 18.
2. It is converted into a voltage signal V ₃ by the resistor 83. These voltages V ₁ , V ₂ , and V ₃ change in response to the command signal 23 (change in conjunction with each other).

First, a normal rotation drive operation will be explained (output current i ₅ of the motion detector 18 = 0). The second distribution controller 12 connects the current path to the coils 6, 7, 8 (second
A current detection resistor 47 that is inserted in series in the current-carrying current paths of the drive transistors 3, 4, and 5 to detect the supplied current, a current correction resistor 54, and a voltage drop across the resistors 47 and ₅₄ and a current controller 48 which receives a voltage signal V ₁ responsive to the command signal 23 and obtains an output current responsive to both, and a second selector 5 comprising transistors 50, 51, and 52.
3.

The current controller 48 is composed of, for example, a differential voltage amplifier and a voltage-current converter, and outputs a current according to the difference between voltages V ₁ and V ₄ and supplies it as a common emitter current of the first selector 53. .

Transistors 50, 51 of the first selector 53,
The emitters 52 are commonly connected, and the output voltages of the Hall elements 41, 42, and 43 of the position detector 11 are applied to the base side, respectively. Hall element 4
1, 42, 43 sense the magnetic flux of magnet 9,
An analog voltage signal is generated according to the rotational position. The transistors 50, 51, and 52 distribute the common emitter current to each collector current according to the difference in their base voltages, and the transistor with the lowest base voltage has the largest collector current, and the collector currents of the other transistors are zero. Become. The collector currents of the transistors 50, 51, 52 become the base currents of the first drive transistors 3, 4, 5, are amplified and supplied to the coils 6, 7, 8.

The current Ia supplied to the commands 6, 7, and 8 (current flowing through the drive transistors 3, 4, and 5) is detected as a voltage drop across the resistor 47, and is input to the current controller 48 via the resistor 54. As a result, the current controller 4
8. A first feedback loop (current feedback loop) is configured by the first selector 53, the first drive transistors 3, 4, 5 and the resistors 47, 54, and supplies the coils 6, 7, 8. Ensure current voltage signal V ₁
(Therefore, the current value corresponds to the command signal 23) (Actually, V ₁ and V ₄ are set to be equal.) As a result, the h The influence of _FE becomes significantly smaller.
Also, as the magnet 9 rotates, the Hall element 4
The energization of the first drive transistors 3, 4, and 5 is controlled and switched so that the output voltages of the transistors 1, 42, and 43 change, and current is supplied to the corresponding coil.

Note that the capacitor 49 is provided for phase compensation of the above-mentioned feedback loop. In addition, the coil 6,
Capacitors 94, 95, 98 connected to 7, 8
The series circuit of resistors 95, 97, and 99 reduces the spike voltage caused by switching of the energizing path.

The second distribution controller 16 controls the operating voltage (collector
Detection to detect the absolute value of the emitter voltage V _CE
It is composed of a comparator 71 and a second selector 76 made up of transistors 73, 74, and 75. The output i ₃ of the similar current generator 19 is input to the detection/comparator 71, and is connected to the resistor 61 and the diodes 62, 6.
3, a reference voltage signal V ₂ of a predetermined voltage value is generated from the common connection terminal (emitter side) of the first transistors 3, 4, and 5. Voltage signal V ₂ is voltage signal V ₁
(V ₁ and V ₂ both change according to the command signal 23
supply current to the commands 6, 7, 8 (i.e., the first drive transistor 3,
The signal V ₂ is made large when the supplied current (4, 5) is large, and is made _small when the supplied current is small.

One end (emitter side) of the detection transistors 64, 65, and 66 serves as a reference terminal and is connected to a reference potential point (signal
V ₂ point) in a direct current manner (directly or via a resistor, diode, etc.), and one end (base side) serves as a detection terminal for the first drive transistors 3, 4,
It is connected to each output terminal (collector side) of 5. As a result, the first drive transistors 3, 4,
The operating voltage of the transistor in the energized state of No. 5 and the reference voltage signal V ₂ are compared, and the operating voltage value is higher than the signal V ₂ by the emitter-base forward voltage V _D
When the current becomes smaller, the corresponding detection transistor becomes conductive and outputs a current to the collector side.

FIG. 2 shows the current path when drive transistors 13 and 4 are activated. The current path is as follows: positive terminal of DC power supply 1 -> second drive transistor 13 -> coils 6 and 7 -> first drive transistor 4 -> resistor 47 -> negative terminal, and the operation of the first drive transistor 4 in the energized state. The voltage V _CE is the other drive transistor 3,
The voltage V _CE of 5 is smaller than that of V CE. Then, the detection transistors 64, 65, 66 compare the voltage V _CE of the first drive transistors 3, 4, 5 with the reference voltage signal V ₂ and output a collector current according to the difference. In FIG. 2, when the operating voltage of the first drive transistor 4 becomes smaller than the voltage signal V ₂ by the base-emitter forward direction V _D , the detection transistor 65 becomes active and outputs a collector current. The output currents of the respective detection transistors 64, 65, and 66 are combined (collector sides are commonly connected), and the first
Diode 67 transistor 69, resistor 6 in the diagram
The signal is inverted and amplified by a current mirror consisting of 8 and 70, and is supplied to a second selector 76. Therefore, an output current corresponding to the operating voltage of the first drive transistor when energized is obtained.

second selective 76 transistors 73, 74;
The emitters 75 are commonly connected, and the outputs of the Hall elements 44, 45, 46 of the position detector 11 are applied to each base terminal, and the common emitter current is distributed to the collector side according to the base voltage. The collector currents of the transistors 73, 74, and 75 become the base currents of the second drive transistors 13, 14, and 15, and switch and control the energization of the coils 6, 7, and 8.

Therefore, the detector/comparator 71, the second selective 7
6. A second feedback loop is constituted by the second drive transistors 13, 14, 15 and the coils 6, 7, 8, and the first drive transistors 3, 4, 5
The operating voltage V _CE of the transistor in the energized state matches a predetermined small voltage value in the active region, and a current equal to the energizing current of the first drive transistor (corresponding to the command signal 23) is applied to the second drive transistor. The current also flows through the drive transistors of the coils 6, 7, and 8, and a bidirectional current (a current whose direction changes as the magnet 9 rotates) is stably supplied to the coils 6, 7, and 8.

To explain this, when the current flowing through the second drive transistor becomes transiently smaller than the current flowing through the first drive transistor, the operating voltage of the first drive transistor decreases due to the load effect of the coil. This reduction in the operating voltage is detected by the detector and comparator 71 and increases the base current, and thus the collector current, of the second drive transistor via the second selector 76, so that the first drive transistor A current equal to the current flowing current (collector current) is output from the second drive transistor. Further, the operating voltage of the first drive transistor is stably controlled to a small value (approximately equal to V ₂ −V _D ) within the active region corresponding to the reference voltage V ₂ . Here, the capacitor 77 is provided for phase compensation (to prevent oscillation) of the second feedback loop.

In this way, the first feedback loop and the second feedback loop stably supply the current corresponding to the command signal 23 to the coil corresponding to the output of the position detector 11, and as the magnet 9 rotates, the current is stably supplied to the coil corresponding to the output of the position detector 11. coil 6,
The current paths to 7 and 8 are switched sequentially, and current is supplied in both directions.

Next, the operation detection 18 and current correction operation will be explained. The output _i4 of the similar current generator 19 is input to the motion detector 18, and the diodes 81, 82,
The resistor 83 connects the second drive transistor 1
A reference voltage signal V ₃ of a predetermined detected value is generated from the common connection terminal (emitter side) of 3, 14, and 15. The voltage signal V ₃ changes in conjunction with the voltage signal V ₁ (V ₁ ,
V ₃ both change in response to the command signal 23), when the current supplied to the coils 6, 7, 8 (i.e., the current flowing through the first and second drive transistors) is large, the signal V ₃ is increased; When the supply current is small, the signal _V3 is made small. One end (base side) of the detection transistors 87, 88, 89 is connected as a reference terminal to the reference potential point (signal _V3 point) in a direct current manner, and one end (emitter side) is connected as a detection terminal to the resistor 84, 85, 86, respectively. It is connected to each output terminal (collector terminal) of the second drive transistors 13, 14, and 15 via DC. As a result, the operating voltage (absolute value of collector-emitter voltage drop) of the second drive transistors 13, 14, and 15 in the energized state is compared with the reference voltage signal _V3 , and the operating voltage value is determined by the signal V3. When the emitter-base forward voltage V _D becomes smaller than V ₃ , the corresponding detection transistors 87, 88,
89 becomes conductive and outputs current to the collector side.

For example, as shown in FIG.
When transistors 3 and 4 are activated, the operating voltage of the second drive transistor 13 in the energized state is lower than the voltage of the other drive transistors 14 and 15. The detection transistors 87, 88, 89 compare the operating voltages of the second drive transistors 13, 14, 15 with the reference voltage signal _V3 , and in FIG. ₃ by V _D , the detection transistor 87 becomes active and outputs a collector current. The output currents of the detection transistors 87, 88, and 89 are combined (the collector sides are commonly connected) to become the output current _i5 of the operation detector 18 in FIG.
is input to the current correction means of the distribution controller 12.
That is, the operation detector 18 detects that the operating voltage of the second drive transistors 13, 14, 15 when energized has become smaller than a predetermined value (saturated state or near-saturated state), and the output current i ₅ becomes larger as the operating voltage becomes smaller.

The output current i ₅ of the motion detector 18 is supplied to the low resistors 54 , 47 of the first distribution controller 12 . The voltage position V ₄ increases due to the voltage drop across the current correction resistor 54 due to the current i ₅ , and the coils 6 , 7 , 8 increase due to the operation of the first and second feedback loops described above.
The current supplied to becomes smaller.

To explain this, V ₁ =V ₄ due to the operation of the first and second feedback loops. now,
If the resistance values of the resistors 54 and 47 are R ₅₄ and R ₄₇ , and the combined value of the current supplied to the coil is Ia, then from V ₁ = V ₄ , V ₁ = R ₅₄・i ₅ +R ₄₇・(Ia+i ₅ ) ∴ Ia=1/ _R47・[ _V1− ( _R54 + _R47 )・_i5 ]……(1). That is, the current Ia supplied to the coil is the voltage signal V ₁ responsive to the command signal 23 and the motion detector 1.
8, and when _i5 becomes large (the operating voltage of the drive transistor becomes small), _the current Ia supplied to the coil is corrected to be small. As a result, saturation of the first and second drive transistors is prevented, the operations of the first and second distribution controllers 12 and 16 are stabilized, and smooth start-up acceleration characteristics are obtained.

When the rotational speed of the motor reaches a predetermined value, the command signal 23 increases and the current supplied to the coil is decreased. As a result, the second drive transistor 13,
14 and 15 no longer occur, and the motion detector 1
The output current i ₅ of the coil 8 becomes zero, and the above-mentioned current correction operation no longer occurs (current corresponding to the command signal 23 is supplied to the coils 6, 7, and 8).

Note that the current correction resistor 54 is made sufficiently larger than the current detection resistor 47 (usually R ₅₄ =1K).
Ω, R ₄₇ =1Ω), and the current correction operation is performed at a sufficiently small current i ₅ compared to Ia.

In this example, the reference terminal side is connected to DC (directly or via a resistor, diode, etc.) as a reference voltage signal.
Connect to the potential point of V ₂ or V ₃ and drive the detection terminal side with DC drive transistors 3, 4, 5 or 13,
Detection transistors 64, 65, which are PNP type transistors connected to each output terminal of 14, 15,
66, 87, 88, 89, the elements required to detect the operating voltage of the first drive transistors 3, 4, 5 or the second drive transistors 13, 14, 15 are transistors, It requires only a diode and a resistor, and can be integrated on a single silicon chip.

As a result, when the circuit portion of the electric motor shown in FIG. 1 is constructed from a monolithic integrated circuit, the number of external parts is small and manufacturing is easy. In addition, the detection characteristics have small variations between phases, and the current required for detection can be small. Furthermore, if a PNP transistor with a lateral structure is used as the detection transistor, the base-emitter breakdown voltage and the base-collector breakdown voltage can be increased, improving reliability.

Further, in this embodiment, the reference voltage signal to be compared with the operating voltage of the first drive transistors 3, 4, and 5 is
V ₂ or second drive transistor 13, 14,
A reference voltage signal V ₃ to be compared with the operating voltage of coil 15 is changed in response to command signal 23, and coils 6, 7,
When the supply current to 8 (that is, the current flowing through the drive transistor) is large, the voltages V ₂ and V ₃ are increased,
When the supply current is small, the voltages V ₂ and V ₃ are made small. Thereby, the current supplied to the coil is controlled so that the operating voltage of the drive transistor reliably becomes a small voltage value within the active region, regardless of the magnitude of the current flowing therethrough.

Such characteristics are important, especially when considering the saturation voltage characteristics of the drive transistor. This will be explained by taking the motion detector 18 and current correction operation as an example. Generally, the saturation voltage of a transistor increases in proportion to the conducting current (collector current), and conversely, the active region becomes narrower (see FIG. 8).

Now, consider the case where the voltage signal V ₃ is constant (the voltages across the resistor 81 and diodes 82 and 83 are constant). If the second drive transistor is in a saturated state and operates to increase the current flowing through it, the operating voltage (in this case, the saturation voltage) increases as the current flowing therein increases. Therefore, the difference between the reference voltage signal _V3 and the operating voltage becomes smaller, and the output current of the detection transistor becomes smaller. Motion detector 1
8 becomes _smaller , and the voltage drop across the current correction resistor 54 of the first distribution controller 12 becomes smaller. Accordingly, the first feedback loop operates to increase the current Ia supplied to the coil, increasing the voltage drop across the coil, and causing the second drive transistor (and first drive transistor) to become oversaturated. (The current correction operation becomes incomplete due to a detection error of the operating voltage detector 18).

On the other hand, if the voltage signal V ₃ is changed in response to the energizing current as in this embodiment, the increase in the voltage signal V ₃ can be larger than the increase in the saturation voltage of the drive transistor as the energizing current increases. To,
The above-mentioned malfunction does not occur. Furthermore, since the operating voltage detection threshold (reference voltage signal V ₃ ) when the current supplied to the coil is small can be set small, the range in which the current correction operation is performed can be narrowed (the normal operating range can be widened).

The above description is based on the second distribution controller 16 and the second drive transistors 13, 14, 15.
This also applies to the operation of the detection/comparator 71 that detects the operating voltage of the first drive transistors 3, 4, ₅ in the operation of the feedback loop of It is preferable to change it in conjunction with the current flowing through the transistor.

However, the present invention is not limited to such a case, and one or both of the reference operation signals V ₂ and V ₃ may be kept constant. FIG. 4 shows an electrical circuit diagram representing another embodiment of the invention in which signals V ₂ and V ₃ are constant. In this example, the current of the constant current source 201 is supplied to the resistor 61 and the diodes 62 and 63, and V ₂
is constant, and the current of the constant current source 202 is connected to the resistor 8.
3. The reference voltages V 2 and V 3 are supplied to the diodes 81 and 82 to keep V ₃ constant (in such a case, the reference voltages V ₂ and V ₃ are (need to be set large).

Furthermore, in the configuration of the operation detector 18 shown in the embodiment of FIG. ₁ or _FIG . is constant (zero) and does not change. Then, the output current at which the operating voltage becomes less than a predetermined value (V ₃ −V _D ) changes in response to the operating voltage. Figure 5 shows its characteristics. If this characteristic is used, when the operating voltage of the second drive transistor decreases and saturates, a current corresponding to (proportional to) the difference between the operating voltage (saturation voltage) and the reference voltage _V3 will be output. Therefore, the deeper the saturation, the larger the output current becomes, and the detection operation and current correction operation become more stable and reliable. In addition, the response range of the motion detector 18 may be narrow, and the configuration can be simplified.

Similarly, the characteristics of the detection/comparator 71 of the second divider 16 are as shown in FIG. In addition to making the operation of the loop stable and reliable, the response range of the detector/comparator 71 is narrowed to simplify the configuration.

Although the operation detector 18 in the above-mentioned embodiment was designed to detect all the operating voltages when the second drive transistors 13, 14, and 15 are energized, the present invention is not limited to such a case. The operating voltage of the drive transistor may be detected when the drive transistor is energized.

Further, in the above-described embodiment, the operating voltage of the first drive transistor when it is energized is detected to control the energization current of the second drive transistor, and the operating voltage of the second drive transistor when it is energized is detected. Current correction is made to prevent saturation of the first drive transistor automatically by preventing saturation of the second drive transistor. However, the present invention is not limited to such cases; for example,
In the configuration as shown in FIG. 8 of Publication No. 55-6938, at least one of the first drive transistor and/or the second drive transistor
The current supplied to the coil may be corrected by detecting the saturation of the transistor from the operating voltage when the coil is energized.

It goes without saying that the present invention is not limited to rotary brushless DC motors that perform rotational motion, but can also be applied to so-called linear brushless DC motors in which the motor movable portion moves linearly relative to each other. Furthermore, it is not limited to stable field means using magnets, but any field means with fixed magnetization may be used. For example, even a magnetic pole structure that is excited by direct current can be used. The number of phases is also not limited to three phases, but is arbitrary.

Further, the position detecting means is not limited to the magneto-electric transducer such as the Hall element shown in the above-mentioned embodiments, and various known methods such as a method using high frequency coupling can be used.

In addition, drive transistors 3, 4, 5, 13, 1
4 and 15 are not limited to bacipolar transistors, but field effect transistors may be used.

Note that if the command signal 23 of the above-described embodiment is set to a constant voltage, it can be used as a reel motor for a tape recorder or the like. In addition, various modifications are possible without changing the gist of the present invention.

As is clear from the above description, the brushless DC motor of the present invention has good coil utilization efficiency and small current ripples during startup and acceleration.
Therefore, if a brushless DC motor for audio and video equipment is constructed based on the present invention, the motor will be highly efficient and generate less vibration and noise.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the circuit operation of FIG. 1, FIG. 3 is a diagram showing the operating area of a transistor, and FIG. FIG. 5, an electric circuit diagram representing another embodiment of the invention, is a diagram representing the detection characteristics of the motion detector 18. DESCRIPTION OF SYMBOLS 1... DC power supply, 3, 4, 5... First drive transistor, 6, 7, 8... Coil, 9... Field magnet, 11... Position detector, 12... First distribution controller, 13, 14, 15... Second drive transistor, 16... Second distribution controller, 18... Operation detector, 19... Similar current generator, 23... Command signal, 2
4...Current converter, 41, 42, 43, 44, 4
5, 46... Hall element, 48... Current controller, 53
...first selector, 64, 65, 66, 87, 8
8, 89...Detection transistor, 71...Detection comparator, 76...Second selector.

Claims (1)

[Claims] 1. A position detection means for detecting the position of a motor movable part, a multi-phase coil, a first drive transistor group consisting of a plurality of transistors that supply current to the coil, and a command for supplying current to the coil. first distribution control means that distributes and controls energization of the first drive transistor group in response to a command signal and a current correction signal that corrects the current supply to the coil, and in response to the output of the position detection means; and,
a second drive transistor group consisting of a plurality of transistors inserted in series in a current path between the coil and the first drive transistor group; and a second drive transistor group in response to the output of the position detection means. a second distribution control means for distributing and controlling energization of the second drive transistor group; and an operation of outputting the current correction signal according to a comparison result between the operating voltage of the transistor in the energized state of the second drive transistor group and the first predetermined value. The second distribution control means includes a detection comparison means for comparing the operating voltage of the transistors in the energized state of the first driving transistor group with a second predetermined value, When the operating voltage of the first drive transistor in the energized state increases, the conducting current of the second drive transistor in the energized state is decreased, and when the operating voltage of the first drive transistor in the energized state decreases, the energized state is reduced. The operation state of the second drive transistor group is controlled in accordance with the output of the detection and comparison means so as to increase the current flowing through the second drive transistor at , and the operation detection means further includes: When the operating voltage of the second drive transistor in the energized state is greater than the first predetermined value, the current correction signal is made zero, and the first distribution control means operates to cause the current correction signal to be applied to the coil. The supply current is controlled to a value corresponding to the command signal, and when the operating voltage of the second drive transistor in the energized state becomes smaller than the first predetermined value, the second drive transistor is controlled to a value corresponding to the command signal. The current correction signal having a value corresponding to the difference between the operating voltage and the first predetermined value is output, so that the current supplied to the coil is made smaller than the value corresponding to the command signal. Brushless DC motor.