JPH0243437B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless DC motor that electronically switches power supply to multiple phase coils according to the position of a movable part of the motor.

Brushless DC motors have low torque ripple, no noise caused by brushes, and have a long life, so they are used in a variety of audio equipment. Japanese Patent Publication No. 55-6938 discloses that in such a brushless DC motor, current is passed in both directions (full-wave drive) to the star-connected three-phase coil to improve coil utilization efficiency. is disclosed. According to this, a constant current is supplied to the multiphase coils by a first transistor group, and a potential at a common connection point of the multiphase coils is set to a predetermined value by a second transistor group. is controlled.

However, in such a configuration, in addition to the terminal that supplies current to the coil, the common connection terminal (required simply to detect the voltage) must also be drawn out from the motor side and connected to the circuit element. The number of wires increased, making manufacturing complicated.

Taking these points into consideration, the present invention provides a brushless DC motor that achieves stable and reliable full-wave drive by wiring only terminals that supply current to multiphase coils (no wiring for common connection terminals). It is something to do.

The configuration of the brushless DC motor according to the present invention is as follows:
position detection means for detecting the position of the motor movable part;
a plurality of phase coils, a first drive transistor group consisting of a plurality of transistors that supply current to the coils, and an output of the position detection means that corresponds to a command signal that instructs the supply of current to the coils; and a plurality of transistors inserted in series in a current path formed by the coil and the first drive transistor group. a second drive transistor group; and a second distribution control means for distributing and controlling energization of the second drive transistor group in response to the output of the position detection means, the second distribution control means comprising: an operation detection means for detecting the operating voltage of the transistors in the energized state of the first drive transistor group; The present invention is characterized by comprising a control means for controlling the current flowing through the two drive transistor groups.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention. In FIG. 1, 11 is a field magnet attached to the rotor, 12, 13, 1
4 is a star-connected three-phase coil group, 26,2
7 and 28 are the first drive transistor group; 46 and 4;
7 and 48 are a second drive transistor group, and 21 is a resistor for detecting the combined current supplied to the coils 12, 13, and 14. Further, a portion 101 surrounded by a broken line is a position detector constituted by Hall elements 15, 16, 17, 18, 19, and 20 that sense the magnetic flux of the magnet 11, and 102 is a position detector composed of Hall elements 15, 16, 17, 18, 19, 20.
103 is a first distribution controller that distributes and controls energization of the corresponding first drive transistor group 26, 27, 28 in response to the outputs of Hall elements 18, 19, 20; This is a second distribution controller that distributes and controls energization of the corresponding second drive transistor groups 46, 47, and 48.

Next, its operation will be explained. to supply voltage V _CC
When 12V is applied, the voltage drop across the resistor 21 and the command voltage signal 60 are compared in the voltage/current converter 105, and a current corresponding to the difference between the two is output.
The transistor 23 configuring the differential circuit 104,
24 and 25 as a common emitter current. The output voltages of the Hall elements 15, 16, 17 are applied to the base terminals of the transistors 23, 24, 25, respectively, and the common emitter current is distributed to each collector current according to the difference in the base voltages.
The collector current of the transistor with the lowest base voltage is the largest, and the collector currents of the other transistors are zero or almost zero.

The collector currents of the transistors 23, 24, 25 are connected to the first drive transistor group 26, 27, 28.
The base currents are amplified and supplied to the collectors 12, 13, and 14. coil 12,1
The current supplied to the resistors 3 and 14 is detected as a voltage drop across the resistor 21, and is input to the inverting input terminal of the voltage/current converter 105.

As a result, the voltage/current converter 105, the first differential circuit 104, the first drive transistor group 2
6, 27, 28 and the resistor 21 constitute a first feedback loop (current feedback loop), and the current supplied to the coils 12, 13, 14 reliably becomes a constant current value corresponding to the command signal 60. Note that the capacitor 22 interposed between the inverting input terminal and the output terminal of the voltage/current converter 105 is provided for phase compensation of the above-mentioned feedback loop. (This capacitor 22 may be connected between the output of the voltage/current converter 105 and the power supply terminal.) FIG. 3 shows an example of the configuration of the voltage/current converter 105. Here, the voltage of the signal 60 and the voltage of the resistor 21 are compared by the transistor 61 and the resistor 62, and the difference is converted into a current corresponding to the difference.
The current is inverted by 3.64 current mirror circuits and output.

Next, the operation of the second distribution controller and the second drive transistor group will be explained. The second distribution controller 103 controls the first drive transistor group 26, 2
an operation detector 106 that detects the operating voltage of the transistors 7 and 28 in the energized state; and a constant current source 4.
0, a comparator 107 that differentially compares a reference voltage value determined by the diode 39, the resistor 41, and the resistor 21 with the output voltage of the operation detector 106, and draws a current corresponding to both; differential circuit 10
8.

FIG. 2 shows the current path when drive transistors 46 and 27 are activated. From FIG. 2, the current path is as follows: side power supply → transistor 46 → coils 12 and 13 → transistor 27 → resistor 21 → side power supply, and the terminal voltage of coil 13 is the same as that of coil 12,
It becomes smaller than the terminal voltage of 14. As a result, diode 37 becomes conductive, and other diodes 36 and 38
becomes non-conductive, and the output voltage A of the motion detector 106
becomes a value greater than the forward voltage V _D of the diode 37 from the sum of the operating voltage V _CE (collector-emitter voltage) of the first drive transistor 27 in the energized state and the voltage drop across the resistor 21 .

The output voltage A of the motion detector 106 is output to the comparator 107.
is applied to the base side of the differential transistor 51. On the other hand, the base side of the differential transistor 52 is connected to the first drive transistor group 26, 27, 28 by a constant current source 40, a diode 39, and a resistor 41.
specified voltage value from the common connection point (emitter side) of
A reference voltage value larger by V _ref = V _D + R ₄₁ ·I ₄₀ is applied. Transistors 51 and 52 therefore reduce the operating voltage of first drive transistor 27.
V _CE and a predetermined voltage value R ₄₁ · I ₄₀ (usually about 0.5V to 1.5V) are substantially compared, and a current corresponding to the difference between the two is drawn into the transistor 52, and the second differential circuit 108 supplied to

Transistors 43, 44, 4 of differential circuit 108
Hall elements 18, 19, 2 are provided on each base terminal of 5.
A zero output is applied to distribute the common emitter current to the collector depending on its base voltage. The collector currents of the transistors 43, 44, and 45 become the base currents of the second drive transistor group 46, 47, and 48, and the current supply to the current amplifying coils 12, 13, and 14 is switched and controlled.

Therefore, a second feedback loop is configured by the motion detector 106, the comparator 107, the second differential circuit 108, and the second drive transistor group 46, 47, 48, and the first drive transistor group 26 ,27,
Transistor operating voltage V _CE in the energized state of 28
is operated to match a predetermined voltage value R ₄₁ ·I ₄₀ in the active region. To further explain this, a decrease in the operating voltage of the first drive transistor is detected by the motion detector 106 and increases the sink current of the comparator 107, increasing the base current of the second drive transistor and thus The operating voltage of the second drive transistor is increased by increasing the collector current.
V _CE is reduced, thereby increasing the operating voltage of the first drive transistor.

If such a feedback loop is implemented, the operation of the second differential circuit 108 and the second drive transistor group 46, 47, 48 will be stabilized, and the position detector 1
The switching of the energizing transistors in response to the output of 01 is performed reliably and smoothly.

Further, since the comparison voltage V _ref can be set to be sufficiently smaller than V _CC , even if the voltage drop across the coils 12, 13, and 14 is considerably large, the second drive transistor is in the active region and is unlikely to be saturated.

Note that the capacitor 42 is provided for phase compensation of the feedback loop described above. Also, coil 1
Capacitor 2 connected to terminals 2, 13, and 14
The series circuit of 9, 31, 33 and resistors 30, 32, 34 reduces the spike voltage caused by switching of the energizing path.

In the above-mentioned embodiment, an example was shown in which three-phase coils were connected in a star shape, but the present invention is not limited to such a case, and can generally be configured in a motor having multi-phase coils. Furthermore, it goes without saying that the drive transistor is not limited to a bipolar transistor, but may also be a field effect transistor. Furthermore, the configurations of the motion detector, comparator, etc. are not limited to the above-described embodiments. In addition, various modifications can be made without changing the spirit of the present invention.

According to the embodiments described above, the operating voltage of the first drive transistor in the energized state is detected, and when the operating voltage of the first drive transistor in the energized state increases, the energization is performed so that the voltage becomes a predetermined value. Control is performed so that the conduction current of the second drive transistor in the conduction state is decreased, and when the operating voltage of the first drive transistor in the conduction state becomes small, the conduction current of the second drive transistor in the conduction state is increased. As a result, stable and reliable full-wave drive can be achieved using wires with only terminals that supply current to multiphase coils.Therefore, there is no need for a common connection terminal for the coils, and the number of connection terminals to the motor coils is small. The number of parts and manufacturing man-hours are often reduced. Also,
Due to the reduction in the number of connections to the drive circuit and the coil, the number of output pins will also be reduced if, for example, the circuit of FIG. 1 is constructed from a one-chip integrated circuit.

Therefore, if a brushless DC motor for audio equipment or video equipment is constructed based on the present invention, equipment with good performance can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit connection diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining its operation, and FIG. 3 is a diagram showing an example of the configuration of a voltage/current converter. 11... Magnet, 12, 13, 14... Coil, 26, 27, 28... First drive transistor group, 46, 47, 48... Second drive transistor group, 101... Position detector, 102 ...first distribution controller, 103...second distribution controller,
104... First differential circuit, 105... Voltage/current converter, 106... Operation detector, 107... Comparator, 108... Second differential circuit.

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. a first distribution control means for distributing and controlling energization of the first drive transistor group in response to a command signal and in response to the output of the position detection means; a second drive transistor group consisting of a plurality of transistors inserted in series in a current path; and second distribution control that distributes and controls energization of the second drive transistor group in response to the output of the position detection means. The second distribution control means includes an operation detection means for detecting the operating voltage of the transistor in the energized state of the first drive transistor group, and an operation detection means for detecting the operating voltage of the first drive transistor group. and control means for controlling the current flowing through the second drive transistor group in response to the output signal of the operation detection means.