JP3298075B2 - Motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

【table of contents】

 BACKGROUND OF THE INVENTION Problems to be Solved by the Invention Means for Solving the Problems (FIGS. 1 and 5) Operation (FIG. 1) Example (1) First Example (FIGS. 1 to 4) (2) Second embodiment (FIGS. 5 and 6) (3) Other embodiments Effects of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit,
For example, the present invention is suitably applied to a motor driving circuit for driving a motor for driving a reel of a tape recorder, particularly a motor requiring a wide dynamic range from low speed to high speed.

[0003]

2. Description of the Related Art Conventionally, in this type of motor drive circuit, an energizing timing is obtained from a back electromotive force generated in each phase coil of a motor, and a predetermined drive current is applied to each phase coil at the timing. Thus, the motor is driven to rotate.

[0004]

In general, the starting torque is large as a characteristic of a motor, and a high speed rotation is often required after the motor starts to move. However, in the conventional motor drive circuit, the motor is driven with a fixed torque constant.If a wide dynamic range is required, the motor must be driven with high torque and high rotation characteristics. No.

[0005] Therefore, in the case of driving with such high torque and high rotation characteristics, there is a problem that the driving voltage becomes high, which generates unnecessary torque and increases power consumption.

Further, in a conventional motor drive circuit, when trying to servo-control the rotation speed of the motor at a constant value, the voltage applied to the motor is changed in accordance with the load applied to the motor. However, there is a problem that the power consumption at the time of doing so increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a motor characteristic of high-torque low-speed rotation and low-torque high-speed rotation with low power consumption, and performs motor speed servo with further lower power consumption. It is intended to propose a motor drive circuit capable of performing the above.

[0008]

According to a first aspect of the present invention, there is provided a motor drive circuit for supplying a drive current to each phase coil of a motor based on timing obtained according to rotation of the motor. Providing an energization time variable means for changing the energization time of the drive current, changing the torque constant of the motor by changing the energization time,
Control is performed so that the torque is low during high-speed rotation and high during low-speed rotation.

In the present invention, the energization time varying means 17, 18, 19 changes the energization start time to each phase coil of the motor.

In the present invention, the energization time varying means 17, 18, 19 changes the energization end time to each phase coil of the motor.

Further, in the present invention, in a motor drive circuit 30 for supplying a drive current to each phase coil of the motor based on a timing obtained according to the rotation of the motor, a drive time variable means for changing the drive time of the drive current. 17,
18, 19 and detection means FG for detecting the number of rotations of the motor
And reference signal generating means 34 for outputting a signal serving as a reference for controlling the number of rotations of the motor to a predetermined number of rotations. The detection signal S _FG and the reference signal S _STD output from the detection means FG match. Change the energization time to
By changing the torque constant, the rotation speed of the motor is servo-controlled to a predetermined rotation speed.

[0012]

The coil utilization factor can be changed by changing the drive time of the drive current applied to each phase coil of the motor, thereby changing the torque constant of the motor. Therefore, the characteristics of the motor can be changed by changing the energization time.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

(1) First Embodiment In FIG. 1, reference numeral 10 denotes a motor drive circuit of a sensorless three-phase brushless motor as a whole, and each phase (U)
Phase, V-phase, and W-phase) are input to the back-EMF voltage detection circuit unit 11.

The back electromotive voltage detection circuit 11 includes a comparison circuit 14,
15 and 16, the comparison circuit 1
Back electromotive voltage VU input to 4, 15 and 16, respectively;
VV and VW are compared with a reference voltage value COM input from a common connection terminal of each phase coil, thereby obtaining back electromotive force signals SU, SV and SW of each phase as shown in FIG. The signal is sent to the timing control circuit 12.

The timing control circuit section 12 includes a back electromotive voltage signal SU, output from the back electromotive voltage detection circuit section 11,
The SV and SW are input to the waveform shaping circuit 17 and also to the clock generating circuit 18. Clock creation circuit 18
Means that the back electromotive force signals SU, SV and SW have the reference voltage value CO
FIG. 2 based on the timing of the zero-cross point crossing M
A clock signal SCK as shown in (B) is created and sent to the subsequent phase shift circuit 19.

The phase shift circuit 19 receives a torque constant control signal SKT input from the outside, and shifts the phase of the clock signal SCK in accordance with the torque constant control signal SKT, as shown in FIGS. ), A switching end signal SEND and a switching start signal SST are obtained.

The switching end signal SEND has a phase delayed by π / 6 with respect to the clock signal SCK, and the switching start signal SST has a phase delayed by (π / 6) + α with respect to the clock signal SCK. It has been done. This switching start signal SST is RS
The switching end signal SEND is input to the reset input terminal (RESET) of the waveform shaping circuit 17 having a flip-flop circuit configuration, and the switching end signal SEND is input to the set input terminal (SET) of the waveform shaping circuit 17.

Therefore, the waveform shaping circuit 17 resets at the timing of the switching start signal SST and resets at the timing of the switching end signal SEND, thereby inputting the back electromotive force signals SU and SV.
And SW are obtained as switching timing signals SU1, SV1, and SW1 indicated by oblique lines in FIGS. 2 (E), 2 (F), and 2 (G). The motor is driven by sending it to the coils of the phases (U phase, V phase and W phase).

Here, in the conventional motor drive circuit,
A switching timing signal is generated based on a signal (SEND) having a phase shifted by π / 6 from the clock signal SCK. The switching timing signal at this time is shown in FIGS. (G) Switching timing signals SU1, SV1, and SW1
Is driven at the timing indicated by the broken line at the tip of the coil, whereby, for example, in the U-phase, a drive current is supplied to the coil from time t1 to time t5.

On the other hand, the motor drive circuit 1 of the present embodiment
At 0, the switching timing signal SU1 rises at time t2 when the phase has elapsed by α from the conventional energization start time t1, whereby the drive current starts to be energized. Therefore, an energization time shorter by α than the conventional energization time can be obtained.

Here, the torque constant of the motor is represented by K _T [N · m /
A], the back electromotive force constant is K _E [V / rps], and the no-load speed is N _O
[rps], the starting torque is T _S [N · m], and the starting current is I _S [A]
The constant K _M, the magnetic flux [Phi [Wb], a conductor resistivity [rho [Omega /
m], the number of windings is Z, the total conductor length per phase is L [m], the number of magnet poles is P, the number of phases is D _r , and the coil utilization is A.

(Equation 1)

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5) Is represented by

Here, the switching timing signals SU1, SV1, and SW1 of FIG. 2 are configured to delay only the rising timing (that is, the energization start timing) by the phase α. In this case, the area S of each of the switching timing signals SU1, SV1, and SW1, that is, the area of the waveform shown by oblique lines in FIG.

This area S is given by

(Equation 6) Is represented by Here, in the above equation (6), α =
In the case of 0 (that is, when the phase is 120 ° energized at the time points t1 to t5 (in the case of U phase) in FIG. 2), the value of the expression (6) is 3 ^1/2. (6)
The value S of the equation is

(Equation 7) Becomes Also, from the above equations (1) and (5), it can be seen that the coil utilization rate A and the torque constant _KT are proportional. Therefore, equation (6) expresses the relationship between the torque constants K _T and α (α
Torque constant K _T and new torque constant K
_T ratio). This relationship is shown in FIG.

That is, in FIG. 4, for example, when α is π / 3, K _T becomes １ ／. At this time, from the expression (2), the no-load rotation speed N ₀ is twice as large as the original, and it can be seen that the motor can be used as a high rotation and low torque motor. Note that α can be any value as long as it is in the range up to 2π / 3, so that optimal driving according to the characteristics required of the motor is possible.
However, in the case of π / 3 ≧ α ≧ 2π / 3, a timing occurs in which no current is supplied to any phase, and the timing becomes a dead point. Therefore, it is necessary to avoid setting α in the range.

As described above, the energizing time of the drive current to each phase coil and the coil utilization rate A are in a proportional relation, and the coil utilization rate A and the torque constant _KT are in a proportional relation, so that the phase coil is supplied to each phase coil. can to varying the energization time varying Yotsute torque constant K _T. Rotational speed of the motor by changing the Supporting connexion the torque constant K _T during rotation of the motor, the characteristic of the torque and current, etc. can be varied during the rotation of the motor.

In the above configuration, as shown in FIG. 3, the static characteristics of the reference motor are set to (T _S -N _O , I _S -O), and the starting torque T _S satisfies the specifications, but the no-load rotation speed N _O Assumes that only half of the specifications are available. In this case, if the coil utilization rate A of the motor is halved, the torque constant K
_{Since T} also becomes １ ／, the static characteristic when the coil utilization rate A of the reference motor is １ ／ is shown in FIG.
_S ⁰ -N _O ⁰ , I _S ⁰ -O). Accordance connexion static characteristics of the reference motor in startup requiring a large torque (FIG. _{3 (T S -N O, I} S -O)) sets a torque constant K _T such that, requires a large torque Figure static characteristics of the motor by decreasing the torque constant K _T to shorten the energizing time to the respective phase coils of the motor after start requiring high rotational speed without the 3 (T _S ⁰ -N _O
^0, the characteristic shown in I _S ⁰ -O), thereby capable of generating a high number of revolutions after start with can generate a large torque at the time of startup.

Here, in the conventional case, considering a motor in which the power supply voltage V is doubled for the purpose of setting the no-load rotation speed high, the static characteristic is (T _S '-N _O ', I _S
'-O), which satisfies the specification. In this case, torque is generated more than necessary, so that power consumption increases and the power supply voltage itself increases. Also, considering a motor in which the number of turns Z of the coil is reduced to half, its static characteristic is (T
_{S''-N O'', I} S''-O) next, T _S and N
_It can be seen that although _O is as specified, the current consumption is as high as when the power supply voltage V of the reference motor is doubled.

[0029] Thus by making the Yotsute torque constant K _T to the configuration shown in FIG. 1 is changed while the motor drive, the characteristics of the motor capable of generating high rotational speed, start up as well as generating a large torque at the time of startup low It can be realized with low voltage and low power consumption.

According to the above configuration, by changing the torque constant K _T to shorten the energizing time to the respective phase coils, one characteristic of the characteristics and low torque and high speed rotation of the high torque and low speed rotation motor Thus, the motor can be driven with low voltage and low power consumption.

(2) Second Embodiment FIG. 5 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals as in FIG. 5 shows a second embodiment of the motor drive circuit according to the present invention. A speed servo circuit section 31 for generating a torque constant control signal SKT ′ to be input to the block 19 is provided.

That is, the FG provided in a part of the motor
(Frequency generator), a frequency signal _SFG corresponding to the number of rotations of the motor is transmitted through the amplifier circuit 32 to FV (frequency-
The voltage is input to the conversion circuit 33. FV conversion circuit 33
Compares the frequency of the frequency signal S _FG with the frequency of the reference frequency signal S _STD output from the reference oscillation circuit 34, generates a torque constant control signal SKT ′ having a voltage value corresponding to the frequency difference from the comparison result, and amplifies the torque constant control signal SKT ′. The signal is output to the phase shift circuit 19 via the circuit 35.

Here, a limiter is provided at the output stage of the amplifying circuit 35 by a zener diode 36, and fixes the torque constant control signal SKT 'to a predetermined value when the rotation speed of the motor is out of the servo range. It has been made like that.

The phase shift circuit 19 shifts the phase of the clock signal SCK on the basis of the torque constant control signal SKT 'in the same manner as in the first embodiment, thereby switching the switching start signal SST and the switching end signal S.
END is generated and output to the waveform shaping circuit 17.
Therefore, the waveform shaping circuit 17 can control the energizing time of the driving current applied to each phase coil according to the torque constant control signal SKT '.

Thus, the motor drive circuit 30 changes the energizing time to each phase coil to thereby obtain the torque constant K _T
Can be varied, which allows the motor speed,
Characteristics such as torque and current can be changed during rotation of the motor. Therefore, it is possible to apply a speed servo such that the frequency signal SFG from the _FG is synchronized with the frequency set in the reference oscillation circuit 34.

[0036] In the above configuration, the torque constant K _T of Yotsute motor to vary the duration of energization of the motor as shown in FIG. 6 changes. For example, by increasing the torque constant K _T , the motor characteristics composed of (T _S −N _O , I _S −O) sequentially become (T _S ′ −N _O ′, I _S ′ −O).
(T _{S ″} -N _{O ″} , I _{S ″} -O). It is possible to perform velocity servo that changes the torque constant K _T according to the rotation speed of the sub connexion motor.

For example, a motor set in advance so that the no-load rotation speed is N _O ^O and the starting torque is T _S ^O (= T _S × N _O / N _O ^O ) is set by the motor drive circuit 30 shown in FIG. If you connexion speed servo control, the number of rotation from start-up T _S is N
Until the point P where _O ^O is reached, the torque constant K _T is kept constant by the Zener diode 36, and the rotation starts linearly. After that, when the rotation speed rises to N _O ^O , the FG signal S
_The torque constant _KT changes so that the frequency of _FG matches the frequency of the reference oscillation circuit 34. Accordingly, the rotational speed becomes N _O according to the change in the rotational speed (that is, the load on the motor).
^The torque constant K _T is controlled so as to be constant at ^O.

[0038] accordance connexion output torque in the servo interval from T _p to O are controlled so that the load is accordance connexion torque constant K _T in lighter increases, the rotational speed in this way the section becomes N _O ^O constant Servo control.

In this servo section (section where the number of revolutions is constant at N _O ^O ), the current consumption is (I _{p to} I _{P1 ′ to} O).
Becomes Here, in the conventional case, the reference motor (FIG. 6)
_{(T S -N O, I S} -O) If you voltage control servo so that the rotational speed N _O ^O constant), the current consumption of the reference motor becomes (I _p -I _P1 -O). Therefore, in the servo control by the motor drive circuit 30 (FIG. 5) of the second embodiment, the current consumption can be further reduced.

According to the above configuration, the current consumption can be further reduced by changing the torque constant K _T to perform the speed servo of the motor.

(3) Other Embodiments In the above-described embodiment, the case where the energization start time is changed has been described as a method of changing the energization time to each phase coil of the motor. Not limited,
The same effect as in the above case can be obtained by changing the power supply end time or changing both the power supply start time and the power supply end time.

In the above-described embodiment, the case where the present invention is applied to the motor driving circuit of the reel driving motor of the tape recorder has been described. However, the present invention is not limited to this, and may be used in various other applications. It is suitable for application to a motor drive circuit of a motor.

[0043]

As described above, according to the present invention, the time constant of the drive current to the coil is changed to change the torque constant, so that the motor characteristics with a wide dynamic range can be reduced with low current consumption. In addition to this, the rotation speed servo control can be realized with much lower power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a motor drive circuit according to the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the motor drive circuit according to the present invention.

FIG. 3 is a characteristic curve diagram showing characteristics of the motor according to the first embodiment.

FIG. 4 is a characteristic curve diagram showing a relationship between a torque constant ratio and a phase.

FIG. 5 is a block diagram showing a second embodiment of the motor drive circuit according to the present invention.

FIG. 6 is a characteristic curve diagram showing characteristics of the motor according to the second embodiment.

[Explanation of symbols]

10, 30... Motor drive circuit, 11... Back electromotive voltage detection circuit section, 12... Timing control circuit section, 13
... A drive circuit section, 17 a waveform shaping circuit, 19 a phase shift circuit, 31 a speed servo circuit section, 34 a reference oscillation circuit, and an FG frequency generator.

Continuation of the front page (56) References JP-A-60-51490 (JP, A) JP-A-2-193350 (JP, A) JP-A-1-122387 (JP, A) JP-A-63-161892 (JP) , A) JP-A-2-60490 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/06

Claims (4)

(57) [Claims] 1. A motor drive circuit for supplying a drive current to each phase coil of the motor based on a timing obtained according to rotation of the motor, comprising: a drive time varying means for changing a drive time of the drive current. changing the by connexion torque constant of the motor to changing the energizing time, during high-speed rotation is low torque, low-speed rotation
A motor drive circuit characterized by controlling the torque to be high at times . 2. The motor drive circuit according to claim 1, wherein said energization time varying means changes an energization start time to said phase coils of said motor. 3. The motor drive circuit according to claim 1, wherein said energization time varying means changes an energization end time of each of said phase coils of said motor. 4. A motor drive circuit for supplying a drive current to each phase coil of the motor based on a timing obtained according to the rotation of the motor, wherein a drive time varying means for changing a drive time of the drive current; Detecting means for detecting the number of revolutions of the motor; reference signal generating means for outputting a signal serving as a reference for controlling the number of revolutions of the motor to a predetermined number of revolutions; a detection signal output from the detecting means And changing the energization time so that the reference signal matches , and
The Rukoto varied, a motor driving circuit being characterized in that so as to servo-control the rotational speed of the motor to a predetermined rotational speed.