JPS6141439Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless motor control circuit, and particularly to a brushless motor control circuit that can quickly stop the motor.

When stopping the rotation of a brushless motor that rotationally drives an object with a large inertial mass, such as a magnetic disk of a magnetic disk recording device, it is not possible to stop the motor quickly by simply stopping the power supply. Therefore, in order to quickly stop such a brushless motor, a friction brake or a so-called dynamic brake is sometimes used. When a friction brake is used, there are problems such as shortened service life due to wear of the brake shoe, generation of frictional heat, and adhesion of oil and dirt. In addition, in the case of a dynamic brake, there is a problem in that the brake torque is inversely proportional to the number of rotations, so that when the number of rotations becomes small, sufficient braking force cannot be obtained.

Therefore, there is also a control circuit that performs quick control by switching the drive current in the opposite direction so as to give a reverse torque to the motor. However, if such a control circuit is configured to be able to select forward and reverse rotation, it is necessary to identify the rotation drive direction and then apply a reverse torque, which requires a rotation direction detection sensor and complicates the circuit. There was a problem.

Therefore, an object of the present invention is to provide a brushless motor control circuit with a simple circuit configuration that can quickly stop the motor.

The brushless motor control circuit according to the present invention operates to apply reverse torque to the motor for a predetermined time after receiving a stop command, and to release the motor drive circuit after the predetermined time has elapsed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, capacitors C ₁ and C ₂ are charged by a power supply voltage V _s through resistors R ₁ and R ₂ respectively, and a switch ST is closed in response to a start command.
and switch SP that closes in response to a stop command.
are respectively discharged by the closing of . A set terminal S and a reset terminal R of the flip-flop circuit 1 are connected to capacitors C ₁ and C ₂ , respectively. Here, the capacitances of capacitors C ₁ and C ₂ are selected such that C ₁ ≪ _{C 2} ,
When the power is turned on, the flip-flop 1 is always reset by a logic "L" signal. The Q terminal of the flip-flop 1 is connected to the trigger input terminal of the monostable multivibrator 2. Monostable multivibrator 2 is a variable resistance
By adjusting VR, the time in which the device is in the quasi-stable state, that is, the pulse width of the pulse output from the Q terminal when triggered, can be adjusted. The Q terminal of the monostable multivibrator 2 is connected to the trigger input terminal T of the bias circuit 3. Bias circuit 3 outputs a resistor from terminal A when a logic “H” signal is supplied to the trigger input terminal.
A bias current is generated toward terminal B via R ₄ , R ₅ , Hall elements H ₁ , H ₂ , and resistor R ₆ . Conversely, when a logic "L" signal is supplied, a bias current flows from terminal B to terminal A. The output terminals of the Hall elements H ₁ and H ₂ are connected to the input terminals of the control circuit 4, and the output terminals of the control circuit 4 are connected to the bases of the transistors Q ₁ to Q ₄ via terminals a, b, c, and d. ing.
The control circuit 4 generates pulses having the same period as the potential change of the output terminals of the Hall elements H ₁ and H ₂ , and these pulses are supplied to the bases of the transistors Q ₁ to _{Q 4} . Drive coils W ₁ -W ₄ arranged near a magnetized rotor (not shown) of the motor are connected between the transistors Q ₁ -Q ₄ and the power supply V _ss . On the other hand, the terminals of the flip-flop circuit 1 and the terminals of the monostable multivibrator 2 are connected to the input terminal of the NAND gate 5, and the output terminal of the NAND gate 5 is connected to the trigger terminal of the power switch 6.

FIG. 2 shows a specific circuit of the bias circuit 3 in FIG. 1. In this circuit, when the logic "H" signal is input to the trigger terminal T, the transistor Q ₅ is turned off, the transistor Q ₆ is turned on, the transistor Q ₇ is turned on, and the transistor Q ₈ is turned off. This causes a current to flow towards B. Conversely, when an “L” signal is supplied, transistors Q ₅ and Q ₈ turn on, and terminal B
A bias current will flow from A to A.

The operation of the brushless motor control circuit according to the present invention described above will be explained below with reference to FIG.

After the power is turned on, each terminal of flip-flop 1 and monostable multivibrator 2 outputs a logic “H” signal, so NAND gate 5
The output is a logic "L" signal, and the power switch 6 is turned off. Therefore, the drive coils W ₁ to _{W 4}
is not energized and the rotor remains stopped. Thereafter, when the start switch ST is closed, a start pulse as shown in FIG. Since a logic "H" signal is also generated at the terminal of the stable multivibrator 2, a logic "H" signal is generated from the NAND gate 5 (Fig. 3e), the power switch 6 is turned on, and the drive coils W ₁ -
W ₄ is sequentially excited by conduction of transistors Q ₁ to _{Q 4} to provide rotational torque to the rotor. Now, since the Q terminal of monostable multivibrator 2 is "L", the bias current flows from B to A, and the motor starts rotating in the positive direction, reaches a predetermined rotation speed, and maintains a steady state ( Figure 3 f).

Stop switch to stop the motor
When SP is closed, a trigger pulse (Fig. 3b) is supplied to the reset terminal R of the flip-flop circuit 1, the flip-flop circuit 1 is reset, and "H" and "L" signals are generated at the Q terminal. . At this time, the monostable multivibrator is triggered and a pulse of "L" and "H" time width t _n is generated at its Q terminal, respectively, so while this pulse is occurring, the Hall elements H ₁ , The bias current of _H2 is reversed, creating a reverse torque and causing the motor to suddenly decelerate. When the pulse disappears, the bias currents of Hall elements H ₁ and H ₂ are reversed again, but at the same time the NAND gate 5
Since the output becomes "L", the power switch 6 is turned off (Fig. 3e), and the excitation current of the drive coils _W1 to _W4 is cut off, so the motor torque becomes zero, and the viscous resistance of the rotating shaft, etc. It decelerates and stops, for example, after a time _ts .

Therefore, when the motor is stopped by the control circuit according to the present invention, the time t _n +t _s required from the stop command to the stop is, for example, less than half of the time t _l required when stopping the motor by simply cutting off the excitation current. (Fig. 3 f). Note that FIG. 3g shows changes in the torque of the motor.

Here, if the maximum torque of the motor is Tm, the inertial mass of the load is Jl, and the rotational speed of the load is _N0 , the above-mentioned time _tn is calculated as follows: _tn ≦2π・_N0・Jl/980×60×Tm Set. In addition, in order to have a degree of freedom in the rotational speed of the load, the pulse width t _n can be changed by changing the resistance VR of the monostable multivibrator 2.

From the above, it is clear that the brushless motor control circuit according to the present invention, despite its simple circuit configuration, can automatically generate a brake torque to achieve a quick stop.

In addition, in the above embodiment, the switches ST and SP
can be constructed by a mechanical switch, but it is clear that an electronic switch can also be used if necessary. The same applies to the power switch 6; for example, a Darlington-connected transistor switch may be used.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing a specific circuit example of the block of Fig. 1, and Fig. 3 is a waveform diagram showing the operation of the circuit of Fig. 1. Explanation of the symbols of the main parts: 1... flip-flop circuit, 2... monostable multivibrator, 3...
...bias circuit, 4...control circuit, 5...NAND
Gate, 6...power switch.

Claims (1)

[Claims for Utility Model Registration] (1) A magnetized rotor, a plurality of drive coils arranged near the rotor, and the electrical characteristics of which change in response to the magnetic field generated by the rotor. A brushless motor control circuit that drives or stops a brushless motor consisting of magnetically sensitive elements arranged as shown in FIG. a second stable circuit that takes a second stable state;
a pulse generating circuit that generates a pulse of a predetermined time width when the stable circuit transitions from a first stable state to a second stable state; and a pulse generating circuit that supplies a positive current bias to the magnetically sensitive element when the pulse is not present; a bias current supply circuit that supplies a current bias in the opposite direction to the magnetically sensitive element when a pulse exists; and when the second stable circuit is in a first stable state or the second stable circuit is in a second stable state; The coil excitation circuit includes a drive signal generation circuit that generates a motor drive signal when the pulse is present, and a coil excitation circuit that supplies an excitation current to the drive coil in response to a change in the electrical characteristics of the magnetically sensitive element only when the motor drive signal is present. A brushless motor control circuit characterized by: (2) The second stabilizing circuit includes an R-S flip-flop circuit, first and second charging circuits that supply a charging voltage to the set terminal and reset terminal of the flip-flop circuit, respectively, and 2. The brushless motor control circuit according to claim 1, comprising: a start switch for discharging the charging circuit; and a stop switch for discharging the second charging circuit in response to the stop command. (3) The brushless motor control circuit according to claim 1, wherein the pulse generating circuit comprises a monostable multivibrator.