JPS63157688A - Constant voltage driving circuit for brushless motor - Google Patents

Abstract

PURPOSE:To perform high constant speed rotation with sufficient torque, by comparing the induced voltage of respective coils composing a plurality of phases, with set voltage which is previously set by a detecting circuit, and by controlling the conductivity of switching transistors with the voltage. CONSTITUTION:The driving circuit of a brushless motor is provided with first-third switching transistors 4-6 with first-third coils 1-3 connected in series to be phases U-W, first-third current mirror circuits 7-9 connected to the bases of the transistors, fourth-sixth switching transistors 19-21, fourth-sixth current mirror circuits 22, 38, 44, and first-third detecting circuits 26-28. The fluctuation of voltage applied to the coils 1-3 is always detected by the detecting circuits 26-28, and according to the detection, a control transistor 25 is controlled, and the applied voltage of the coils 1-3 is set to be constant regardless of rotational frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a constant voltage drive circuit for a brushless motor suitable for a reel motor of a tape recorder.

(B) Prior Art Recently, brushless motors have been widely used in tape recorders, video tape recorders, etc. because they do not generate noise and have a long life. Such a brushless motor rotates a rotor by sequentially passing current through the coils of each phase, as described in, for example, Japanese Utility Model Application Publication No. 59-53696.

(C) Problems to be Solved by the Invention By the way, the reel motor of the tape recorder, etc., uses different rotational speeds and torques depending on whether it is in the early spring removal or early return state and in the playback or recording state, so it may become impossible to rotate or reverse rotation. This will cause more current to flow than necessary and increase the consumption of batteries, etc.
It is necessary to increase or decrease the voltage applied to the motor during high-speed rotation, such as in the early spring removal state, and during low-speed rotation, such as in the regeneration state.

Furthermore, even in the same state during high-speed rotation or low-speed rotation, the number of revolutions differs greatly between the start of tape winding and the end of tape winding, so it is necessary to keep the voltage applied to the motor constant.

The present invention provides a constant voltage drive circuit for a brushless motor that meets these requirements.

(d) Means for Solving the Problems The constant voltage drive circuit for a brushless motor of the present invention includes a detection circuit that compares the detected voltage by comparing the induced voltage of the coils constituting a plurality of phases with a set voltage, and a detection circuit that compares the detected voltage. It consists of a control transistor controlled by a detection voltage, and is further configured to be able to change the set voltage of the detection circuit according to the number of rotations used.

(E) Function Since the constant voltage drive circuit of the brushless motor of the present invention has the above-described configuration, the fluctuation in the applied voltage applied to the coil is always detected by the detection circuit, and the control transistor is controlled by the detected voltage. The voltage applied to the coil is made constant regardless of the rotation speed. Furthermore, if the set voltage of the detection circuit is increased or decreased depending on the number of rotations used, the detected voltage changes and the constant voltage applied to the coil can be increased or decreased.

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

(1), (2), and (3) are the first and second
and a third coil, the first, second and third coils (I
First, second and third switching transistors (4), (5) and (6) are connected in series to O2) (3),
The first, second and third switching transistors (4
The base of the transistor (X5X6) is connected to the emitter-collector path of one of the transistors (10X11X12) constituting the first, second and third current mirror circuits (7), (8) and (9). Different transistors (13) of the first, second and third current mirror circuits (708) (9)
) (14) and (15) include fourth, fifth, and sixth switches that are turned on by pulse signals that are generated sequentially in response to one revolution of the rotor and are applied from terminals (16), (17), and (18); Ching transistor (19) (20) (21)
The emitters of the fourth, fifth and sixth switching transistors (19), (20) and (21) are commonly coupled and connected through one transistor (23) of the fourth current mirror circuit (22). It is grounded.

(25) are control transistors 9, (26) (27) connected in parallel to a transistor (24) different from the transistor (23) of the fourth current mirror circuit (22).
) (28) is the first, second and third coil (1)
(2) A detection circuit for detecting the voltage induced in (3), consisting of a diode (29x30) (31) and first, second and third detection transistors (32), (33) and (34). The first, second and third detection transistors (32
) (33) The emitter of C34) is a resistor (35) (
36) One transistor (39) of the fifth current mirror circuit (38) is connected to the power supply via (37).
) (40X41), and its collector is connected to the base of the control transistor (25). The other transistor (43) of the fifth current mirror circuit (38) is connected to the sixth current mirror circuit (44).
) is connected to a power supply through one transistor (45) of the sixth current mirror circuit (44), and a control transistor (47) is connected to the other transistor (46) of the sixth current mirror circuit (44). Two types of control signals are applied to the base of (47) according to a mode changeover switch (not shown).

The pulse signal applied to the terminals (16), (17), and (18) is generated by providing a Hall element as described in the above-mentioned Japanese Utility Model Application No. 59-53696, and generating a magnetic field that changes as the rotor rotates. The pulse signal may be generated from the Hall element by
), the voltage induced in the coils constituting multiple phases is added to a comparator provided for each phase and compared with a reference voltage, and the outputs of these comparators are connected to each other by diodes. Additionally, when the comparator output energizes the negative diode, it is better to apply a pulse signal to the terminal connected to the coil of the phase corresponding to this diode, turn on the switching transistor, and energize the coil.

Next, the operation of the constant voltage drive circuit for a brushless motor according to the present invention will be explained.

When the playback button or the record button is operated for the first time to perform playback or recording, a control voltage V is supplied to the base of the control transistor (47), the control transistor (47) is turned on, and a current IC flows. However, this current IC is R6......Resistance value v1 of resistor (48).・
....The voltage between the base and emitter of the control transistor (47) is the voltage between the base and emitter of the control transistor (47), and since the transistors (45) and (46) constitute the sixth current mirror circuit (44), the fifth current mirror circuit (38) The current I also flows through the transistor (43). flows. Therefore, the fifth current mirror circuit (3
8) the other transistor (39) (40) (41
) also flows through the resistors (35), (36), and (37). Therefore, the first, second and third detection circuits (2
6) (27) (28) resistance (35) (36)
The voltage drop v8 in (37) is determined by the resistance R1 (
The resistance value is 35) (36) (37). As mentioned above, pulse signals are sequentially applied to the terminals (16), (17), and (18) as the rotor rotates.

Now, when a pulse signal is applied to the terminal (16), the fourth switching transistor (19) turns on, which turns on the first switching transistor (4) and turns on the first coil (1).
A current is applied to the first coil (1) to excite the first coil (1).

Next, when a pulse signal is applied to the terminal (17), the fifth switching transistor (20) is turned on, thereby turning on the second
Turn on the switching transistor (5) and turn on the second coil (
2) A current is applied to the magnet to excite it.

In this way, each time a pulse signal is sequentially applied to the terminals (16), (17), and (18), the first, second, and third switching transistors (4), (5, and 6) are turned on in sequence, and the first, Since the second and third coils (1), (2), and (3) are excited one after another, electromagnetic action occurs between them and the permanent magnets included in the rotor (not shown), causing the rotor to rotate.

By the way, the first, second and third coils (1) (2) (3)
The voltage VA induced in the resistors (35) and (36
X37) drop voltage V. and the first, second, and third detection transistors (32), (33), and (34). For example, at the beginning of tape winding, the voltage VA induced in the first, second, and third coils (1), (2), and (3) when the tape rotates quickly is the voltage drop V across the resistors (35), (36, and 37). . If the detection voltage is sufficiently large compared to the control transistor (25), the detection voltage applied to the control transistor (25) via the first, second and third detection transistors (32) (33) (34) will also be large. is sufficiently conductive and the current flowing through the transistor (23) of the fourth current mirror circuit (22) decreases, so the current flowing through the first, second and third current mirror circuits (7), (8) and (9) also decreases. The first, second and third switching transistors (4) (
5) The drive current to (6) decreases, and the voltage applied to the first, second and third coils (1), (2) and (3) decreases.

Conversely, as the rotational speed of the motor decreases, the voltage VA induced in the first, second, and third coils (1), (2), and (3) decreases, resulting in a drop in voltage V across the resistors (35), (36, and 37). . When which difference becomes smaller than the above, the detection voltage detected by the first, second and third detection circuits (26) C27') (28) and supplied to the control transistor (25) decreases, and the control Since the impedance between the collector and emitter of the transistor (25) increases, the fourth current mirror circuit (
The current flowing through the first, second and third current mirror circuits (7) (8) (9) also increases, and the current flowing through the first, second and third current mirror circuits (7) increases.
(8) The drive current supplied to the first, second and third soching transistors (4) (5) and (6) via (9) also increases, and (1) (
2) The voltage applied to (3) increases. Even if the rotation speed changes like this, the first, second and third coils (1) (2)
The voltage applied to (3) is kept constant, and the torque increases or decreases as necessary depending on the rotational speed.

In the foregoing, the operation when playing back or recording a tape has been explained. Next, the operation when rewinding or removing a tape in early spring will be explained. When resetting the tape in early spring, it is necessary to rotate the motor at high speed, so the first
It is necessary to increase the voltage applied to the second and third coils (1), (2), and (3).

Then, when the early spring return button or the early spring take button is operated, a control voltage V2 larger than the control voltage V1 is applied to the base of the control transistor (47). Then, the current IC flowing through the sixth current mirror circuit (44) increases and becomes V2-V□ ■o=R4・・・・・・・・・・・・・・・・・・・・・
...(3), and the first, second and third detection circuits (
7) (8) (9) resistance (35) (36) (37
) voltage drop V. is V, =R,I. -5 (V2-V,,
)...(4), which is higher than the voltage Vs in equation (2) above.

In the same manner as described above, the motor rotates and a voltage VA is induced in the first, second and third coils (1') (2) (3), and is compared with the voltage V in the above equation (4). Since V is higher than the voltage V8, the first, second and third coils (1)
(2) Even if the voltage VA induced in (3) is sufficiently high compared to the reproduction state etc., the detection voltage detected by the first, second and third detection transistors (32) (33) (34) Since is small, the current flowing through the control transistor (25) is also small, and a larger current flows through the fourth current mirror circuit (22) compared to the above, and the first, second, and third switching transistors (4) (5) Since the drive current applied to (6) increases, the first, second and third coils (
1) The applied voltage applied to (2) and (3) also increases.

Even at this time, if the rotation speed increases further, the detection voltage detected by the first, second, and third detection circuits (26) (27X28) increases, and the impedance between the collector and emitter of the control transistor (25) decreases. However, since the current flowing to the fourth current mirror circuit (22) is reduced, the first, second and third switching transistors (4) (
5) The drive current to (6) is reduced, and the voltage applied to the first, second and third coils (1), (2) and (3) is reduced. The first, second and third coils (1) (2) (3) are thus set by a control voltage V, applied to the base of said control transistor (47).
A constant voltage higher than that during reproduction is applied to the unit, and the unit is rotated at a high constant speed with sufficient torque.

(G) Effects of the Invention As described above, the constant voltage drive circuit for a brushless motor of the present invention compares the induced voltage of each coil constituting a plurality of phases with a preset voltage set in a detection circuit to detect a detected voltage. Since the control transistor is controlled by the detected voltage and the conductivity of the switching transistor is controlled according to the rotation speed, the voltage applied to the coil can be kept constant regardless of the rotation speed.

Furthermore, if the set voltage of the detection circuit is changed in accordance with the rotational speed used, the ratio to the fluctuation of the induced voltage of each coil detected by the detection circuit is changed, and the control transistor is controlled accordingly. The magnitude of the constant voltage applied can be set according to the number of rotations used, and a torque corresponding to the number of rotations used can be obtained.

[Brief explanation of the drawing]

The figure is a constant voltage drive circuit diagram of the brushless motor of the present invention. (1)(2)(3)...Coil, (4)(5)(
6)...First, second and third switching transistors, (7)(8)(9)...First, second and third current mirror circuits, (19)(20)(21) ...Fourth, fifth and sixth switching transistors, (2
2)...Mirror circuit to the 4th Karen 1, (25)
...Control transistor, (26X27028)...First, second and third detection circuit, (32X33X34)...
・Detection transistor.

Claims (2)

[Claims] (1) Switching transistors are connected to coils constituting multiple phases, and the switching transistors are sequentially turned on using pulse signals generated in response to rotation, and voltages are sequentially applied to the coils to rotate the rotor. In a motor, a detected voltage is detected by comparing the induced voltage of each coil with a set voltage set by a detection circuit, a control transistor is controlled by the detected voltage, and the voltage applied to each coil is adjusted to change the rotation speed. A constant voltage drive circuit for a brushless motor, characterized in that the voltage is constant regardless of the voltage. (2) The set voltage of the detection circuit is changed according to the rotational speed used, the ratio of the detection voltage to the fluctuation of the induced voltage of each coil detected by the detection circuit is changed, and the control transistor is controlled accordingly. A constant voltage drive circuit for a brushless motor according to claim 1, wherein the magnitude of the constant voltage applied to the coil can be set according to the number of rotations used.