JPH0243438B2 - - 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 brush noise, and long life, so they are used in various 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 first transistor group supplies a constant current to the multiphase coil, and a second transistor group causes the potential at a common connection point of the multiphase coil to reach a predetermined value. It's in control.

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 the terminals that supply current to the multiphase coils (no need to wire the 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; a first distribution control means for distributing and controlling energization of the first group of drive transistors in response to the above, and a plurality of transistors inserted in series in a current path formed by the coil and the first group of drive transistors; a second group of drive transistors, and a second distribution control means for distributing and controlling energization of the second drive transistors in response to the output of the position detection means, the second distribution control means comprising: operating voltage detection means for detecting the operating voltage of the transistors in the energized state of the second drive transistor group; The present invention is characterized by comprising a control means for controlling the current flowing through the second drive transistor group.

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, 28 are the first drive transistor group; 46, 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, and 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 current becomes each base current, and the current is amplified and the coil 1
2, 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 current corresponding to this difference is converted.
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 second drive transistor group 46, 4
An operation detector 106 (in this embodiment,
collector-emitter voltage V _CE detected), a predetermined voltage value determined by the resistor 41 and constant current source 40
A comparator 107 that compares V _ref = R ₄₁ · I ₄₀ (usually 0.5V to 1.5V) and the output voltage of the operation detector 106 and sinks a current corresponding to both, and a second differential circuit 10
8.

FIG. 2 shows the current path when drive transistors 46 and 27 are activated. From Figure 2, the current path is: side power supply → transistor 46 → coil and 1
3 → transistor 27 → resistor 21 → side power supply, and the terminal voltage of coil 12 becomes coil 13,
It becomes larger than the terminal voltage of 14. As a result, diode 36 becomes conductive, and other diodes 37, 3
8 is non-conducting, and the output voltage A of the motion detector 106 is the second drive transistor 46 which is in the conducting state.
Forward voltage of diode 36 from operating voltage V _CE
The value becomes larger by V _D (considering it from the side power supply terminal).

The output voltage A of the motion detector 106 is output to the comparator 107.
is applied to the base side of the transistor 39. On the other hand, a predetermined voltage value V _ref is applied to the emitter side of the transistor 39 by a constant current source 40 and a resistor 41 . Therefore, transistor 39 is substantially
V _CE and V _ref are compared (the forward voltage of the diode 36 and the base-emitter forward voltage of the transistor 39 are canceled out), and a current flows according to the difference.
The signal is inverted by a current mirror circuit including transistors 49 and 50 and supplied to the second differential circuit 108 .

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, 45 become the base currents of the second drive transistor group 46, 47, 48, and the currents are amplified and sent to the coils 12, 13, 1.
It switches and controls the energization to 4.

Therefore, the motion detector 106, the comparator 107, the second
differential circuit 108, second drive transistor group 4
6, 47, 48 constitute a second feedback loop, and a second drive transistor group 46, 47, 4
The operating voltage of the transistor in the energized state of 8 V _CE
is operated to match a predetermined voltage value V _ref in the active region. To explain this further,
The decrease in the operating current of the second drive transistor is detected by the operation detector 106 and is detected by the comparator 107.
The base current and hence the collector current of the second drive transistor are reduced, and as a result, the operating voltage of the second drive transistor is increased.

If such a feedback loop is provided, the second differential circuit 108 and the second drive transistor group 4
The operations of 6, 47, and 48 are stabilized, and the position detector 10
The switching of the energizing transistors in response to the output of 1 occurs reliably and smoothly.

In addition, since the comparison current V _ref = R ₄₁ · I ₄₀ can be set sufficiently small compared to V _CC , the coils 12 and 1
Even if the current drop at 3 and 14 is quite large, the 1st
The drive transistor is in the active region and is less likely to saturate.

Note that the capacitor 42 is provided for phase compensation of the above-mentioned feedback loop. 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, but can generally configure 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 are possible without changing the gist of the present invention.

As described above, according to the present invention, the operating voltage of the second drive transistor in the energized state is detected, and when the operating voltage of the second drive transistor increases, the energizing current is increased so that the voltage becomes a predetermined value. ,
Since the current is controlled to be smaller when the operating voltage becomes smaller, stable and reliable full-wave drive can be achieved by wiring only the terminals that supply current to the multiphase coils. is unnecessary, the number of connection terminals to the motor coil can be reduced, and the number of parts and manufacturing man-hours are reduced. In addition, due to the reduction in the number of connections between the drive circuit and the coil,
For example, if the circuit shown in FIG. 1 is constructed from a one-chip integrated circuit, the number of output pins will also be reduced.

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. DESCRIPTION OF SYMBOLS 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
...Movement 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 second drive transistor group, and an operation detection means for detecting the operating voltage of the second 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.