JPH0241277B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC motor, and particularly to a DC motor that efficiently utilizes electric power supplied from a power source.

Conventional configurations and their problems Conventionally, when speed control is applied to a DC motor, for example, a DC power source with a constant output voltage is depressurized and controlled using transistors, etc., and a drive voltage corresponding to the speed of the motor is adjusted. It was supplying the coil.
In such a configuration, the power supplied by the DC power supply is the sum of the effective power consumption in the coil and the collector loss of the transistor. In a normal DC motor, the ratio of effective power consumption to power supplied by the power source (power efficiency) is small, about 10 to 30%. In particular, DC motors with a wide variable speed range and multi-speed switching, and DC motors for take-up with a wide variable range of driving force, have significantly poor efficiency during low speed or low driving force operations.

In order to eliminate such drawbacks, the present applicant proposed a power-efficient electronic commutator using a switching type voltage converter capable of extracting a variable output DC voltage in Japanese Patent Application Laid-Open No. 57-34564. We are proposing a type (brushless type) DC motor.
Incidentally, in a DC motor having such a configuration, current is supplied to the coil through a switching transistor of a voltage converter. Now, if we consider the case of speed control, during the startup and acceleration stages of the motor, the output voltage of the voltage converter increases, and it is necessary to supply a large current to the coil, and the switching transistor of the voltage converter also increases. In order to supply current, the base current during on-state must be increased. On the other hand, in a state where the speed is controlled at a predetermined speed (constant speed rotation control state), the output voltage of the voltage converter becomes a predetermined value in response to the load torque and the back electromotive force (proportional to the rotational speed of the motor). The current supplied to the
At 2A, it will be about 250mA during constant speed control). Therefore,
The base current (when on) required for constant speed control is significantly smaller than the base current (when on) of the switching transistor that is required at the time of large current at startup. As a result, if the switching transistor is given a base current that enables large current conduction at startup (required to increase the starting torque), then when small current conduction occurs during constant speed rotation, This is undesirable as it causes a large amount of power loss.

Purpose of the Invention The present invention takes such points into consideration and increases or decreases the base current when the switching transistor of the voltage converter is turned on in response to the current supplied to the coil (the switching transistor is turned on). The object of the present invention is to provide an electronic commutator type DC motor that reduces base current loss in the steady state (such as when rotating at a constant speed) and in the steady state (such as during constant speed rotation).

Configuration of the Invention In order to achieve the above object, the present invention includes a field means having a plurality of magnetic poles, a plurality of coils,
Voltage converting means that is inserted between the coil and the DC power supply and obtains an output voltage that is proportional or approximately proportional to the duty of a switching transistor that operates on and off; and a current path from the output terminal of the voltage converting means to the coil. a drive transistor group consisting of a plurality of transistors for switching, a position detection means for detecting the position of the motor movable part, and a selection means for selecting the drive transistor to be activated in response to an output signal of the position detection means; Current detecting means for detecting the current supplied to the coil from the voltage converting means; command signal generating means for obtaining a command signal; comparing an output signal of the current detecting means with the command signal; and supplying the current to the coil. current control means for controlling the current flowing through the drive transistor so that the current reaches a value corresponding to the command signal; and operation detection according to the difference between the operating voltage of the drive transistor in the energized state and a predetermined reference voltage. A DC motor comprising operation detection control means for obtaining a signal and changing an on-time ratio of the switching transistor in response to the operation detection signal, wherein the voltage conversion means responds to the operation detection signal. A pulse signal generation means for obtaining a pulse signal of a predetermined frequency with a varying duty, and an input current that changes in response to the current supplied to the coil detected by the current detection means, which is proportional to or approximately proportional to the input current. current mirror means for outputting a proportional current; and pulsing means for turning the output current of the current mirror means into a pulse current by turning on and off the input side of the current mirror means according to a pulse signal from the pulse signal generating means. and supply means for supplying the pulse current to the base terminal of the switching transistor, and smoothing means for smoothing the pulse voltage caused by the on/off operation of the switching transistor using an inductance element, a capacitor, and a diode. It is composed of

DESCRIPTION OF EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 is an electrical circuit representing one embodiment of the present invention. In Figure 1, 1 is a DC power supply, 2
is a field magnet (field means) having a plurality of magnetic poles; 3, 4, and 5 are three-phase coils interlinked with the magnetic flux of magnet 2; 6, 7, and 8 are coils 3, 4,
9 is a position detector that detects the position of the movable part of the motor; 10 is a drive transistor that switches the current path to 5;
a selector 11 for selecting the drive transistors 6, 7, 8 to be activated in response to the output of the position detector 9;
12 is a current detector that detects the supply current Ia to the coils 3, 4, and 5, and 12 is a command signal V ₁ and a current detector 11.
13 is a switching type voltage converter that obtains a variable output DC voltage V _M from the DC power source 1; 14 is a drive transistor 6 _, 7; .
16 is a base current corrector that changes the base current I _B when the switching transistor 32 is turned on according to the output V ₂ of the current detector 11; 16 is a magnet 2;
This is a speed detector (command signal generating means) that obtains a command signal _V1 corresponding to the rotational speed of the motor.

First, the normal rotation drive operation will be explained.
Speed detector 1 responds to the rotational speed of magnet 2.
6 changes and is applied to the normal rotation input terminal of the current controller 12 as a command signal _V1 . The output voltage V ₂ of the current detector 11 is input to the inverting input terminal of the current controller 12, and a current corresponding to the difference between V ₁ and V ₂ is output from the current controller 12, and the differential transistor 4
1, 42, and 43 as a common emitter current of the selector 10. The current controller 12 is composed of, for example, a differential voltage amplifier and a voltage/current converter. transistor 41 of selector 10,
The output voltages of the Hall elements 38, 39, 40 of the position detector 9 are applied to the base terminals 42, 43, respectively. Hall elements 38, 39, and 40 sense the magnetic flux of magnet 2 and generate analog voltage signals corresponding to its rotational position. The transistors 41, 42, and 43 distribute a common emitter current according to the difference in their base voltages to each collector current, and the collector current of the transistor with the lowest base voltage becomes the largest, and the collector current of the other transistors becomes zero. . Transistors 41, 42, 43
The respective collector currents of drive transistors 6, 7, 8
The base current is amplified and supplied to the coils 3, 4, and 5. The current Ia supplied to the coils 3, 4, and ₅ is detected as a voltage drop V2 across the resistor 45 of the current detector 11, and is input to the current controller 12.

As a result, the current controller 12, the selector 10, the drive transistors 6, 7, 8, and the current detector 11
A first feedback loop is constituted by this, and the current supplied to the coils 3, 4, and 5 is ensured to have a current value corresponding to the command signal _V1 . As a result, the influence of h _FE variations in transistors 6, 7, and 8 is significantly reduced. Furthermore, as the magnet 2 rotates, the output voltages of the Hall elements 38, 39, and 40 change, and the energization of the drive transistors 6, 7, and 8 is controlled and switched so that current is supplied to the corresponding coil. .

Note that the capacitor 44 is provided for phase compensation (prevention of oscillation) of the feedback loop described above. Also,
Resistor 4 connected in parallel to coils 3, 4, 5
5, 47, 49 and capacitors 46, 48, 50 reduce the spike voltage caused by switching of the current path.

Next, the operations of the voltage converter 13 and the operation detection controller 14 will be explained. The voltage converter 13 connects the positive terminal (Vs=20V) of the DC power supply 1 to the coil 3,
A switching transistor 32 is inserted in the power supply circuit leading to the common connection terminals 4 and 5 with the emitter-collector path connected in series. The output voltage V _M changes in relation to the on-time ratio of the switching transistor 32 (the ratio of the on-time to one cycle of on-off). When this switching transistor 32 is on, the voltage becomes ViVs, and the DC power supply 1 supplies current to the load side through the inductance element 34. When the switching transistor 32 is off, the flywheel diode 33 is on, supplying the energy stored in the inductance element 34 to the load side. As a result, the output voltage V _M of the voltage converter 13 has a value corresponding to the duty of the on time of the switching transistor 32. The output voltage V _M of the voltage converter 13 is supplied to the three-phase coils 3, 4, 5 and drive transistors 6, 7, 8, and the magnet 2
The drive transistors that become active are sequentially switched as the motor rotates.

The operation detection controller 14 detects the operating voltage (collector-emitter voltage in this case) of the drive transistor in the energized state, and this will be further explained. A current I ₁ from the constant current source 64 is supplied to a resistor 65 and diodes 66, 67, and a reference voltage signal V ₃ r of a predetermined voltage value is supplied from the common connection terminal (emitter terminal in this embodiment) of the drive transistors 6, 7, 8. =1.4+R ₆₅・I ₁ ......(1) is generated. Here, 1.4V is diode 66,
67 voltage drop, and R ₆₅ is the value of resistor 65. Each emitter side of the detection transistors 61, 62, and 63 is connected to a reference potential point (signal V _{3 )} as a reference terminal.
point)), and each base terminal is connected in a direct current manner to each output terminal (collector terminal) of the drive transistors 6, 7, and 8 as a detection terminal. As a result, when the operating voltages of the drive transistors 6, 7, and 8 become lower than the above-mentioned reference voltage V _{3 r} by more than 0.7V,
The corresponding detection transistor conducts and shunts a portion of the current I ₁ to the collector side.

Since the operating voltage of the activated drive transistor is lower than the operating voltage of the other drive transistors, the detection transistors 61, 62, 63
The aforementioned reference voltage V ₃ r and the operating voltage of the drive transistor when energized are compared, and a collector current corresponding to the difference is output. Each detection transistor 6
The output currents of transistors 1, 62, and 63 are combined (collector sides are commonly connected), and inverted and amplified by a current mirror of a diode 68, a transistor 70, and resistors 69 and 71, and a current i ₃ is output.

The output current i ₃ of the motion detection controller 14 is converted into a voltage by the resistor 23 of the voltage converter 13 and the oscillator 21
is compared with a triangular wave signal of a predetermined frequency (approximately 50KHz) by the comparator 22, and the transistor 2
Turn 4 on and off.

When transistor 24 is on, transistors 29 and 30 are off, base current I _B of switching transistor 32 becomes zero, and switching transistor 32 is off. When the transistor 24 is off, the current I ₇ of the constant current source 25 and the output i ₆ of the base current corrector 15 are connected to the diode 26,
27, resistor 28, 31, transistor 29, 30
A current proportional to (i ₆ + I ₇ ) (about 40 times) is supplied to a current mirror consisting of transistors 29 and 3.
0 from the collector side, and supplies the base current I _B of the switching transistor 32 to turn on the switching transistor 32. That is, the on-time ratio of the switching transistor 32 is determined by the output current _i3 of the operation detection controller 14, and the output voltage _VM of the voltage converter 13 changes accordingly.

As a result, a second feedback loop is configured by the operation detection controller 14, the voltage converter 13, and the coils 3, 4, and 5, and detects the operating voltage (when energized) of the aforementioned drive transistor, and detects the operating voltage of the drive transistor. is set to a predetermined value (a value corresponding to the reference voltage V ₃ r) within the active region.

This will be further explained. Now, if we consider the case where the output V ₁ of the speed detector 16 increases slightly in a stepwise manner, the current Ia supplied to the coil increases in response to the operation of the first feedback loop (current detector 11 increase the current Ia so that the output V ₂ of is equal to the command voltage V ₁ ). An increase in the current Ia increases the voltage drop across the coil, and the operating voltage of the drive transistors 6, 7, and 8, which are transiently energized, decreases. A decrease in the operating voltage increases the output current i ₂ of the detection transistors 61, 62, 63, and increases the output current i ₃ of the operation detection controller 14. As i ₃ increases, the voltage drop across the resistor 23 of the voltage converter 13 increases, and the on-time ratio of the transistor 24 decreases. Therefore, the on-time ratio of the switching transistor 32 increases, and the output voltage V _M of the voltage converter 13 also increases. Therefore, the operating voltage when the drive transistors 6, 7, and 8 are energized also increases, and its value is controlled to be at or near a relatively small predetermined value within the active region.

Next, the operation of the base current corrector 15 will be explained. Voltage drop of current detector 11 V ₂ = R ₁・Ia
(Here, R ₁ is the value of the resistor 45) is converted into a current i ₅ by the transistor 81, the emitter follower of the constant current source 82, the transistor 83, and the resistor 84. That is, the forward voltages (approximately 0.7V) between the bases and emitters of transistors 81 and 83 cancel each other out, and the voltage drop across resistor 84 and the voltage drop across resistor 45 become equal. If the value of the resistor 84 is _R2 , then _R2・_i5 = _R1・Ia......(2) _i5 =( _R1 / _R2 )・Ia......(3), and the emitter of the transistor 83 The current i ₅ changes in response to the current Ia supplied to the coil. current i ₅
becomes the collector current of the transistor 83, and the transistors 85 and 86 are inverted by the current mirror and output the current i ₆ (=i ₅ ) to the voltage converter 13 (assuming that the h _FE of the transistor is sufficiently large, the transmission by the base current is (ignoring the reduction in gain). Here, if R ₂ =1000·R ₁ , i ₅ is 1/1000 of Ia, which is sufficiently small (usually, R ₂ is set to 100 times or more of R ₁ ).

The current i ₆ is combined with the current I ₇ of the constant current source 25 and is inverted and amplified by the current mirror (diodes 26, 27, transistors 29, 30, resistors 28, 31) to become the base current I _B of the switching transistor 32. (when transistor 24 is off).
If the values of resistors 28 and 31 are R ₃ and R ₄ respectively, then
The base current I _B of the switching transistor 32 is I _B = (R ₃ / R ₄ ) · (i ₆ + I ₇ ) (4) (voltage drop of the diodes 26 and 27 and the base of the transistors 29 and 30)・The voltage drop between the emitters is canceled out). That is, the base current I _B of the switching transistor 32 changes in response to the output V ₂ =R ₁ ·Ia of the current detector 11, increases when the current Ia supplied to the coil is small, and increases when the current Ia supplied to the coil increases. becomes small when is small. here,
If R ₃ = 40·R ₄ , I _B is 40 times (i ₆ + I ₇ ) (usually R ₃ is set to 10 times or more of R ₄ ).

In the embodiment of the present invention shown in FIG. 1, since the base current I _B of the switching transistor 32 of the voltage converter 13 is changed according to the output V ₂ of the current detector 11, the constant speed control state The base current loss is becoming smaller. This will be further explained. During the start-up/acceleration phase of the motor, the output V ₁ of the speed detector 16 increases, the first feedback loop operates to increase the current Ia supplied to the coil, and the second feedback loop operates to increase the current Ia supplied to the coil. The output voltage V _M of the voltage converter 13 is increased so that the operating voltage of the drive transistor when energized becomes a predetermined value (the first and second feedback loops operate simultaneously,
V _M , Ia increases to its maximum value). In order to increase the current flowing to the coil, it is necessary to increase the current flowing through the switching transistor 32 when it is on (collector current), and therefore, it is necessary to increase its base current. Now, let's assume that the current supplied to the coil is Ia = 2A, and the switching transistor 3
Assuming that the current amplification degree h _FE when the transistor 2 is on is 25, it is necessary to supply a current of 2 A/25 = 80 mA or more as the base current.

Here, assuming that the current supplied to the coil in the constant speed control state is 250 mA (corresponding to the load torque), 250/25 = 10 mA is required as the base current when the switching transistor 32 is turned on. do not have. At this time, if the base current (80 mA or more) required during startup and acceleration is allowed to flow as is, a loss of 80 mA - 10 mA = 70 mA (equivalent to 70 mA x 20 V = 1.4 W) will occur.

In this embodiment, the output V ₂ of the current detector 11 =
Output i ₆ of base current corrector 15 in response to R ₁・Ia
changes, the base current I _B of the switching transistor 32 of the voltage converter 13 changes, and the base current is sufficiently large (80 mA or more) even during startup and acceleration.
At the same time, the base current is made small in the constant speed control state. That is, in the startup/acceleration stage, if Ia = 2A, then i ₆ = i ₅ = 2A/1000 = 2 mA, and if I ₇ = 0.1 mA, then i ₆ + I ₇ = 2.1 mA, and the base current of the switching transistor 32 I _B =40·(i ₆ +I ₇ )=84 mA (switching transistor 32 is sufficiently turned on). Also,
When Ia = 250mA (constant speed rotation state), i ₆ = 0.25
mA, and since i ₆ + I ₇ = 0.35 mA, I _B = 14 m
A (Since the required base current is 10mA,
The switching transistor 32 operates on and off). Therefore, the base current loss of 84 mA - 14 mA = 70 mA (equivalent to 70 mA x 20 V = 1.4 W) is reduced.

Note that when starting and accelerating the motor from a state where the output voltage V _M of the voltage converter 13 is zero and the current Ia supplied to the coil is zero, if the output V ₁ of the speed detector 16 increases in steps, , the initial base current I _B of the switching transistor 32 is a value corresponding to the current I ₇ of the constant current source 25 (I _B = 40・I ₇ = 4
mA), and although the switching transistor 32 is not completely turned on, the output voltage V _M of the voltage converter 13 becomes slightly larger. As V _M increases, the current Ia supplied to the coil is increased. (1st
(Operation of Feedback Loop) Since the operating voltage when the drive transistor is energized is small, the output current _i3 of the operation detection controller 14 is large, and the on-time ratio of the switching transistor 32 is large. As the current Ia supplied to the coil increases, the output _i6 of the base current corrector 15 increases, the base current _IB of the switching transistor 32 increases, and the switching transistor 32 performs a complete on/off operation. It becomes like this. As a result, the on-time ratio of the switching transistor 32 of the voltage converter 13 is controlled so that the current Ia corresponding to the command signal V ₁ is supplied to the coil, and the operating voltage of the drive transistor when energized is set to a predetermined value. Furthermore, the base current I _B of the switching transistor 32 has a current value slightly larger than the necessary value to guarantee on/off operation. That is, transient positive feedback occurs (V _M , Ia → i ₆ → I _B → V _M , Ia), and the output voltage V _M of the voltage converter 13 and the supply current Ia to the coil
becomes larger.

In order to operate such positive feedback operation stably and to reduce base current loss, it is desirable to set as follows.

Even when the current Ia supplied to the coil is zero, a predetermined small base current is supplied to the switching transistor 32 (base current when turned on).

The conversion gain from the coil current Ia in the current detector 11 to the output _i6 of the base current corrector 15 _{is A1}
(A ₁ = R ₁ /R ₂ in FIG. 1), and the transfer gain from i ₆ in the voltage converter 13 to the base current I _B of the switching transistor 32 is A ₂ (A ₂ = R ₃ /R ₄ ). , the current amplification degree of the switching transistor 32 is
When A ₃ (A ₃ = h _FE ), the total product A ₁・A ₂・A ₃
bring it closer to 1. In reality, since the current amplification degree A ₃ of the switching transistor 32 tends to fluctuate, it is preferable to set 0.8≦A ₁・A ₂・A ₃ ≦10 (5) (A ₁・A ₂ - If A ₃ is too small, the switching transistor 32 will not be turned on sufficiently during large current operation, and the maximum value of the output voltage V _M of the voltage converter 13 will become small.
Furthermore, if A ₁ , A ₂ , and A ₃ are too large, an excessive base current will be supplied to the switching transistor 32, and the efficiency of reducing base current loss will be reduced).

In addition, although the above-mentioned Example showed the example which used the three-phase coil, this invention is not limited to such a case, and can generally configure a DC motor having a plurality of coils. Furthermore, various known configurations can be adopted for the speed detector 16, position detector 9, selector 10, current controller 12, etc. Furthermore, not only a rotary type DC motor but also a linear type DC motor in which the motor movable part moves in a straight line can be configured. In addition, various modifications are possible without changing the gist of the present invention.

Effects of the Invention As is clear from the above explanation, the DC motor of the present invention has a configuration with good power efficiency. Therefore, if a DC motor for audio and video equipment using a dry battery as a power source is constructed based on the present invention,
A device with low power consumption and long battery life can be realized.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram representing an embodiment of the present invention. 1...DC power supply, 2...Magnet, 3, 4,
5...Coil, 6,7,8...Drive transistor, 9...Position detector, 10...Selector, 11...
... Current detector, 12 ... Current controller, 13 ... Voltage converter, 14 ... Operation detection controller, 15 ... Base current modifier, 16 ... Speed detector, 21 ...
Oscillator, 22... comparator, 32... switching transistor.

Claims (1)

[Claims] 1. A field means having a plurality of magnetic poles, a plurality of coils, and a voltage that is inserted between the coil and a DC power source to obtain an output voltage that is proportional or approximately proportional to the duty of a switching transistor that operates on and off. a converting means, a drive transistor group consisting of a plurality of transistors for switching a current path from an output terminal of the voltage converting means to the coil, a position detecting means for detecting the position of a motor movable part, and an output of the position detecting means. selection means for selecting the drive transistor to be activated in response to a signal; current detection means for detecting the current supplied to the coil from the voltage conversion means; command signal generation means for obtaining a command signal; current control means for comparing the output signal of the detection means with the command signal and controlling the energizing current of the drive transistor so that the current supplied to the coil becomes a value corresponding to the command signal; A DC motor comprising operation detection control means for obtaining an operation detection signal according to the difference between the operating voltage of the drive transistor and a predetermined reference voltage, and changing the on-time ratio of the switching transistor in accordance with the operation detection signal. The voltage converting means includes a pulse signal generating means for generating a pulse signal of a predetermined frequency whose duty is changed in response to the operation detection signal, and a pulse signal generating means for generating a pulse signal of a predetermined frequency whose duty is changed in response to the operation detection signal, and a pulse signal generating means for generating a pulse signal of a predetermined frequency whose duty is changed in response to the operation detection signal, and a pulse signal generating means for obtaining a pulse signal of a predetermined frequency whose duty is changed in response to the operation detection signal, and a pulse signal generating means for generating a pulse signal of a predetermined frequency whose duty is changed in response to the operation detection signal, Current mirror means receives an input current that changes in response and outputs a current proportional or substantially proportional to the input current, and the input side of the current mirror means is turned on and off by a pulse signal from the pulse signal generation means. By this, the output current of the current mirror means is provided with a pulsing means for making the output current into a pulse current, a supply means for supplying the pulse current to the base terminal of the switching transistor, and a pulse voltage generated by the on/off operation of the switching transistor. A direct current motor characterized by having a smoothing means for smoothing using an inductance element, a capacitor, and a diode.