JPH0632798Y2 - Brushless motor starting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a starting circuit of a brushless motor used in a tape recorder, a video tape recorder or the like.

(B) Prior Art In recent years, in tape recorders, video tape recorders, and the like, brushless motors are often used because they do not generate noise or have a long life. The brushless motor detects the position of the rotor by a position detector in order to sequentially apply current to the coils of each phase, as described in Japanese Utility Model Laid-Open No. 59-53696, thereby sequentially switching the switching elements. Need to turn on and off.

(C) Problems to be solved by the invention As described above, the conventional brushless motor requires a position detector such as a hall element to sequentially turn on / off the switching elements, but the brushless motor has recently been downsized. As a result, the size and thickness have been reduced, so that there is no space available for mounting the position detector. Therefore, as described in JP-A-58-172994, it is detected that the induced voltages respectively induced in the coils of a plurality of phases have a predetermined relationship during rotation, and the detection obtained by this detection is performed. Switching transistors are sequentially turned on and off by a signal, and current can be sequentially applied to the coils of each phase to continue rotating the rotor, but in the stopped state, no induced voltage is generated in the coils of each phase.
The rotor is not started when the coil is energized. Therefore, the present invention is designed so that the rotor can be easily rotated from the stopped state, and in particular, the brushless motor can be started even when the coil is stopped without being energized. A starting circuit is provided.

(D) Means for Solving the Problems The starting circuit of the brushless motor of the present invention is provided with a plurality of coils forming each phase, and is provided corresponding to each of the phases, and is induced in each of the phases at one input terminal. A comparator that applies a voltage at a constant ratio and compares it with a reference voltage that is applied to another input terminal; a plurality of switching transistors that are turned on by the output of the comparator to supply current to the coil; A plurality of switch circuits for forcibly setting the voltage applied to one input terminal of each comparator to a high or low level; and a first auxiliary for turning on in synchronization with each of the switching transistors and forcibly deactivating the switch circuits. A switching transistor group and a second auxiliary switching transistor group in which a base and an emitter are commonly connected to the first auxiliary switching transistor group and a collector is coupled. And Njisuta group constituted by the control transistor which all of the auxiliary switching transistors of the second auxiliary switching transistor group is controlled by turned off.

(E) Operation Since the starting circuit of the brushless motor of the present invention has the above-mentioned configuration, when the starting circuit is stopped when no coil of each phase is energized, the second auxiliary switching transistor is used. All the auxiliary switching transistors in the group were turned off, which controlled the control transistor and made sure that the negative input terminal of the comparison circuit was set to the low level from the positive input terminal, so that one of the switch circuits could not operate for the start pulse. The motor can be started.

(F) Embodiment An embodiment of the starting circuit of the brushless motor of the present invention will be described with reference to the drawings.

Fig. 2 shows the brushless motor drive circuit of the present invention.
(2) (3) is the first, second and third coils for U, V and W phases, one end of which is commonly connected and connected to the power supply and the other end of which is the first, second and third switching respectively. Transistor (4) (5)
Grounded via (6). (7), (8) and (9) are the first, second and third comparators, and the first input terminal which is the positive side input terminal is connected through the resistors (10), (11) and (12) to It is connected to one end of the first, second and third coils (1), (2) and (3), and the resistance (13) (1
4) (15) and diodes (16) to (21) are also connected to one end of the first, second and third coils (1), (2) and (3) different from the above, and the first coil The second input terminal, which is the negative input terminal of the second and third comparators (7) (8) (9), is connected to the first, second and third coils (1) (2) (3). It is connected to the commonly connected neutral point.
Furthermore, the output sides of the first, second and third comparators (7) (8) (9) are sequentially coupled by diodes (22) (23) (24) connected in one direction, The current flowing in the diode (22) is added to the first switching transistor (4), and the current flowing in the diode (23) is the second switching transistor.
The currents flowing in (5) and the diode (24) are applied to the third switching transistor (6), respectively. The resistance value of the resistors (10) (11) (12) is the same as that of the resistors (13) (14) (15).
It is set to be 1/2 times.

FIG. 1 is a starting circuit diagram of the present invention, in which (31) (32) (33) are
In the 1st, 2nd and 3rd switch circuits, the resistor (34) (3
5) Via the (36), the first, second and third comparators (7) of FIG.
(8) Transistors (37) (38) (39) to which the voltages at points A, B, and C of the first input terminal of (9) are applied, and the transistors (37) (38) (3)
9) and transistors (40), (44) and (47) each having a base and an emitter connected in common and composed of multi-collector type transistors.
Transistors (51) (52) (53) are used for the emitters of (40) (44) (47).
Are connected to each other. (54a) (55a) (56a) and (54b) (55
b) and (56b) are auxiliary switching transistors that are turned on and off in synchronization with the first, second and third switching transistors (4), (5) and (6), and include a first auxiliary switching transistor group and a second auxiliary switching transistor. Make up a group. The auxiliary switching transistors (54a) (55a) (56a) of the first auxiliary switching transistor group include transistors (57) (58) (59) connected to the bases of the transistors (53) (52) (51). Each is connected to control. Further, the auxiliary switching transistors (54b), (55b) and (56b) of the second auxiliary switching transistor group have their collectors coupled to each other and are connected to the base of the first control transistor (80) to control the operation thereof. There is. Reference numeral (81) is a second control transistor connected to be controlled by the first control transistor (80) so as to be connected in series with the transistor (37) constituting the first switch circuit (31). Connected to control the operation of the open transistor (74). Reference numerals (82), (83) and (84) denote first, second and third compensation transistors whose operations are controlled by the second control transistor (81), and collectors of the third compensation transistor (84). The emitter is the second of the first, second and third comparators (7) (8) (9) which are commonly connected.
It is connected between the input terminal S and the ground.

(60) and (61) are transistors connected to be controlled by the transistors (44) and (40), and a transistor (53) provided to control the operation of the transistor (53). It is connected to control the operation of 66). Further, (62) and (63) are the transistor
A transistor connected to control the operation of (47) and (40) and connected to control the operation of the transistor (67) provided to control the operation of the transistor (52). ing. Similarly (64) and (65)
Is a transistor connected to control the operation of the transistors (47) and (44), and controls the operation of the transistor (68) provided to control the operation of the transistor (51). Are connected as.

Next, the operation of the starting circuit will be described. It is assumed that when the power switch is turned on, the first coil (1), which is the U phase, is still energized and stopped. Since the positive terminal of the first comparator (7), that is, the point A is a negative voltage because the first coil (1) is energized, the collector of the transistor (37) of the first switch circuit (31) is neutral. It is a negative voltage with respect to the point, and the remaining voltage at points B and C is a positive voltage, and the diode from the second comparator (8)
A current flows through (22) toward the first comparator (7). Therefore, the auxiliary switching transistors (54a) (54b) are turned on in synchronization with the first switching transistor (4). When the auxiliary switching transistor 54a is turned on, the transistor 57 is turned on and the transistor 53 is turned off, so the third switch circuit 33 is forcibly turned off. In such a state, when a starting circuit (not shown) is operated and a starting pulse is applied to the terminal (70), the first and second switch circuits (31) and (32) operate in response to the starting pulse. With the current mirror operation, the transistor (40) (4
4) (37) (38) (74) (75) are turned on. When the transistors (37), (38), (74) and (75) are turned on, the potentials at points A and B are lowered, but the transistor (39) forming the third switch circuit (33) is turned off. Therefore, the potential at the point C does not decrease. As a result, in FIG.
The output of the comparator (9) becomes high and the first and second comparators
Since the outputs of (7) and (8) are low, a bias current flows through the diode (23), and the second switching transistor (5)
Is turned on, the current is supplied to the second coil (2) this time. At this time, the first switching transistor
(4) is turned off, but since the transistors (44) and (40) are turned on, the transistors (60) and (61) are turned on, and the transistor (66) is turned on.
The switch circuit (33) is not operated even if the switch is turned off and a start pulse is applied.

When the starting pulse is applied as described above, the first coil (1)
Is switched to the second coil (2). Also the second
When the switching transistor (5) is turned on, the transistor (58) is also turned on and the transistor (52) is turned off.
Transistor (75) is already turned on, so transistor (38) is turned on while the start pulse is applied.
Leave the points at low level. However, when the activation pulse becomes low level, the transistors (37) (38) (39) ... Are turned off. At this time, the transistor (58) turns on and the transistor
(52) is turned off and the second switch circuit (32) is forcibly deactivated.

Therefore, when a start pulse is applied to the terminal (70) again, the transistors (38) and (39) are turned on, and the potentials at points B and C are lowered, but the potential at point A is lowered. There is nothing to do. As a result, in FIG. 2, the first comparator
As the output of (7) increases, the second and third comparators (8) and
Since the output of (9) becomes low, a bias current flows through the diode (24) and turns on the third switching transistor (6), so that the current is supplied to the third coil (3) this time. Thus, every time the starting pulse is applied, the starting current is applied in the order of the first, second and third coils (1), (2) and (3), and the rotor starts to rotate.

The starting operation when stopped while the U-phase first coil (1) is energized is performed as described above, but stopped when the V-phase second coil (2) is energized. The starting operation in the case where the current is being applied and the starting operation in the case where the third coil (3), which is the W phase, is stopped while being energized, can be similarly performed.

However, depending on the conditions of the input signals of the first, second and third comparators (7), (8) and (9), all the phases are turned on or off, that is, the first, second and third comparators (7 ) (8) (9) all output signals are high (high level) or the first, second and third comparators (7) (8) (9) all output signals are low (low level) )
It may stop in the state of. In such a state, since the first, second and third switching transistors (4), (5) and (6) are all in the off state, the first,
No current is supplied to the second and third coils (1), (2) and (3). Therefore, in this case, the first, second and third
It is necessary to energize any one phase of the coils (1), (2) and (3).

First, all phases are on, that is, the first, second and third comparators.
The operation when all the output signals (7), (8) and (9) are in the high level will be described. In such a state, as described above, the first, second and third switching transistors (4), (5) and (6) are all in the off state, so that the second auxiliary switching transistor group The auxiliary switching transistors (54b) (55b) (56b) are all in the off state. Therefore, the auxiliary switching transistor (54b)
The first and second control transistors (80) and (81) whose operations are controlled by (55b) and (56b) are both turned on, and the transistors whose operations are controlled by the second control transistor (81) ( 74) is reverse biased and is in the off state.
The transistor (74) is a transistor for holding the first switch circuit (31) in an operating state when a start pulse is applied. As described above, when the transistor (74) is off, the first switch circuit (31) is turned off. (31) is not turned on even when a starting pulse is applied, and only the second and third switch circuits (32) and (33) operate to reduce the voltage at points B and C. Therefore the second
And the outputs of the third comparators (8) and (9) become low level,
Since the output of the comparator (7) goes high, the diode (2
4) is turned on and an exciting current is passed through the third coil (3) to start rotating the rotor. After that, the energized phase is changed and activated each time the activation pulse is applied as described above.

Next, when no current is flowing through all of the first, second and third coils (1) (2) (3) at startup, the first, second and third comparators
When the outputs of (7), (8) and (9) are all at the low level, but when the outputs of the first, second and third comparators (7), (8) and (9) are at the low level, , First, second and third comparators (7) (8) (9)
The positive input terminal of is lower than the negative input terminal. In such a case, it is not possible to start the system by switching the conduction phase by setting the positive input terminals of the first, second or third comparators (7), (8) and (9) to the low level by the starting pulse as described above.

Next, the operation when all the above-mentioned phases are in the OFF state, that is, when all the output signals of the first, second and third comparators (7), (8) and (9) are in the low level state will be described. In such a state, as described above, the first, second and third switching transistors (4), (5) and (6) are all in the off state, so that the second auxiliary switching transistor group The auxiliary switching transistors (54b) (55b) (56b) are all in the off state. Therefore, the first and second control transistors (80) and (81) whose operations are controlled by the auxiliary switching transistors (54b), (55b) and (56b) are both turned on, and the operation is performed by the transistors (81). The controlled first compensation transistor 82 is turned off. Therefore, the second and third compensation transistors (83) and (84) whose operation is controlled by the first compensation transistor (82) are turned on. When the third compensation transistor (84) is turned on, the potentials of the negative input terminals of the first, second and third comparators (7), (8) and (9) decrease, so the negative input terminal is more positive than the positive input terminal. The output of the first, second, and third comparators (7), (8), and (9) is all set to the high level because of the low level. Therefore, the transistor (74) is turned off by the second control transistor (81) as described above.
The motor can be started by disabling the switch circuit (31) in response to the start pulse.

Since the rotor has a magnet magnetized into a sine wave, when the rotor is rotated as described above, FIG.
As shown in (a), the U-phase first coil (1), the V-phase second coil (2), and the W-phase third coil (3) are 120 degrees in order of induced voltage u of different sine waves. , v, w are generated. Considering the energization timing of each phase, for example, the W-phase third coil (3)
Is energized during the period of t ₀ -t ₁ shown in FIG. That is, during the period of t ₀ -t _1, the resistance (1
Voltage generated in 2) -E _0/2 (where E ₀ is the maximum voltage) or less induced in each coil is further induced in the first coil (1) or the second coil (2) to the resistor (15) The resulting voltage is E ₀
Since it does not become larger, the voltage applied to the positive terminal of the third comparator (9) is always more negative than the neutral point potential V _N applied to the negative terminal (Fig. 3D). The output of (9) becomes negative.

On the other hand, since the voltage applied to the positive input terminal of the first comparator (7) becomes larger than the voltage V _N applied to the negative terminal, the first comparator (7)
The output of is always positive. Therefore, the diode (24) becomes conductive and a forward bias voltage is applied to the third switching transistor (6) to turn on the third switching transistor (6), so that the current is supplied to the third coil (3) from the power supply.

In the period of t ₁ -t ₂ as the rotation of the rotor progresses, the voltage applied to the positive terminal A of the first comparator (7) becomes negative than the neutral point potential V _N (see FIG. 3). C) Second comparator (8)
The voltage applied to the point B, which is the positive terminal of the
_{Since it is} more positive than _N, the output of the second comparator (8) is high and the output of the first comparator (7) is low, so that a bias current flows through the diode (22) and the first switching transistor ( 4) is turned on, so in this case the first
Electric current is supplied to the coil (3).

When the rotor further rotates and becomes a period of t ₂ −t ₀ , the second
The voltage applied to the positive terminal B of the comparator (8) is the voltage V of the neutral point.
_Since it becomes more negative than _N (Fig. 3B), the output of the second comparator (8) becomes negative and the output of the third comparator (9) becomes positive, the diode (23) is turned on and the second switching is performed. Transistor (5)
A forward bias voltage is applied to the second switching transistor (5) to turn it on, and a current is passed through the second coil (2).

Again _t the rotor is rotated from the period _t 2 -t _{0 0} -
In the period of t ₁ , as described above, the third switching transistor (6) is turned on, a current is passed through the third coil (3), and the third coil (3) is excited. When the rotor is rotated in this way,
Since the first, second and third switching transistors (4), (5) and (6) are sequentially turned on and the first, second and third coils (1), (2) and (3) are sequentially excited, the rotor is After being rotated once, it continues to rotate even if the generation of the start pulse is stopped.

(G) Effect of the device The starting circuit of the present invention forms an auxiliary switching transistor group when a signal for starting is supplied when the coils of each phase are stopped without being energized. The control transistors are turned on by turning off all the transistors, and the reference voltages of a plurality of comparators provided to control the current supply operation to the coil by the operation of the control transistors are applied. Since the voltage applied to the two input terminals is forcibly reduced to a voltage lower than the voltage applied to the first input terminal, when the coils of each phase are stopped without being energized, Also, if the plurality of switch circuits are made inoperative with respect to the activation signal by the control transistor, the first input terminal of one of the plurality of comparators is set to the second input terminal. It can be started reliably even in the brushless motor which is configured to supply a current to the coil by a voltage lower than the force terminals.

[Brief description of drawings]

FIG. 1 is a starting circuit diagram of the brushless motor of the present invention, and FIG.
FIG. 3 is a block diagram of the drive unit of the brushless motor used in the present invention, and FIG. 3 is a signal waveform diagram of each unit of the present invention. Description of main drawing numbers (1) (2) (3) …… First, second and third coils, (4) (5) (6) ……
First, second and third switching transistors, (7) (8)
(9) …… first, second and third comparators, (31) (32) (33) …… third
1, second and third switch circuits, (54a) (55a) (56a) ... Auxiliary switching transistors of the first auxiliary switching transistor group, (54b) (55b) (56b) ... of the second auxiliary switching transistor group Auxiliary switching transistor,
(80) (81) ... First and second control transistors, (82) (83)
(84) ... First, second and third compensation transistors.

Claims (1)

[Scope of utility model registration request] 1. A plurality of coils constituting each phase and a plurality of coils provided corresponding to each of the plurality of coils, and a voltage induced in each coil is applied to a first input terminal at a constant ratio. A comparator to which a reference voltage is applied to the second input terminal, and a plurality of switching transistors whose operation is controlled by the output of each comparator and which supplies a current to each of the coils when in the on state. A plurality of switch circuits that are turned on by a start pulse and that make the voltage applied to the first input terminal of each of the comparators above or below a level that forcibly inverts the output of the comparator,
A first auxiliary switching transistor group that turns on in synchronization with each of the switching transistors and forcibly renders one switch circuit in the switch circuit inoperative, and these first auxiliary switching transistor groups are configured. A second auxiliary switching transistor group in which each transistor is commonly connected to the base and emitter, and each collector is coupled to each other;
The operation is controlled by all the transistors forming the second auxiliary switching transistor group, and the voltage applied to the second input terminal of the comparator is applied to the first input terminal when all the transistors are in the off state. Starting circuit of a brushless motor, which consists of a control transistor that forcibly reduces the voltage to a voltage lower than that.