JPS58215993A - Control system for dc motor - Google Patents

Abstract

PURPOSE:To prevent a large current due to the energization of a power source by setting the current limiting value of a motor current limiting circuit at the drive starting time to the prescribed limiting value or lower and then resetting it to the prescribed limiting value, thereby limiting the motor current at the drive starting time to the prescribed value or lower. CONSTITUTION:A monostable multivibrator 10 is conducted ON for the prescribed period by the energization of a start switch 12, and a transistor circuit 11 is turned ON during the period. Accordingly, a current limiter 9 limits a motor current to zero in the prescribed period from the energization of a switch 12. When the multivibrator 10 is turned OFF after the prescribed period, the circuit 11 is also turned OFF, and the current limiter 9 returns the limiting value to the prescribed value. Accordingly, stator coils 2a, 2b start energizing through transistors 4a, 4b which become ON or OFF by operation start of a transistor 7 and the outputs of rotation detectors 3a, 3b, but since the set value of the current limiting circuit 9 rises from zero, it is not energized larger than this value. When the set value reaches the prescribed value, the motor current rises to this value, but does not flow more than this.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention relates to a DC motor control system, and in particular to a DC motor control circuit that has a current limiting circuit that limits the motor current, in which the current at the start of driving can be controlled to a constant value. Regarding motor control methods.

Prior Art In order to limit the motor current to a certain value or less in a conventional DC motor drive circuit, the current can be controlled by placing a low resistance in series with the windings and comparing the voltage value across this resistance with a predetermined reference voltage. A method is used in which the current value is detected and if the current value exceeds a predetermined value, the driving is limited. However, with this method, there is a time delay between when the current detection circuit senses that the current has reached a predetermined value and when it starts limiting the drive circuit. During this time, the limit is delayed and the current value does not reach the predetermined value. There was a drawback to exceeding it.

This will be explained in more detail below based on the drawings. 1st
The figure shows an example of a DC motor (hereinafter simply referred to as "motor") control circuit. In FIG. 1, 1 is a permanent magnet rotor (hereinafter simply referred to as "rotor") of the motor, and 3a and 3b are magnetically sensitive rotation detection circuits that generate a pulse every half rotation of the rotor 1. . The rotation detection circuit 3a.

The output of 3b causes switching transistors 4PL,
4b is turned on every half rotation of the motor 1, and the stator coils 2a, 2'' are supplied from the power supply 13 through the start switch 12.
Since the drive current flows through zero, the motor rotates in a fixed direction. Further, the rotation speed of the motor is controlled by the voltage comparison circuit 0 and the transistor 7 by comparing the output signals of the rotation detection circuits 3a and 3b and controlling the drive current.

In addition, the current flowing through the transistor 7 is controlled by the current detection resistor 8.
is detected as a voltage value, and compared by the current limit circuit 9. If this exceeds a predetermined value, the current limit circuit 9 turns on and stops driving the transistor 7, operating to keep the current below a certain value. .

In the conventional motor control circuit configured as described above, when the start switch 12 is turned on and current begins to flow to the motor, the motor current is already at a predetermined value when the current limiting circuit 9 is turned on. , the current flowing through the transistor 7 exceeds a predetermined value during the delay time corresponding to the ON time of the current limiting circuit 9. When the m source is turned on, the motor postal current without limiting the current is much larger than during normal rotation, so the current rises quickly, and within the delay time, the current far exceeds the limit value. This means that the current limiting circuit 9 is essentially not functioning.

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to eliminate the above-mentioned drawbacks of conventional DC motor control systems, and to enable drive start-up regardless of the magnitude of delay in circuit operation. An object of the present invention is to provide a DC motor control method that can limit the motor current to a certain value or less.

The above object of the present invention is to provide a motor control circuit including a drive circuit that drives a motor, and a current limit circuit that monitors the current flowing through the motor and controls the current flowing to a certain value or less. This is achieved by a motor control method characterized in that the current limit value is set to a value lower than a predetermined limit value and then reset to the predetermined limit value.

Embodiment νF1 of the invention An embodiment of the invention will be described in detail based on the drawings. FIG. 2 is a configuration diagram of a motor control circuit showing an embodiment of the present invention. In FIG. 2, symbols 1 to 9 and 12
．． 13 indicates the same components as shown in FIG.
1o is a monostable multivibrator, and 11 is a transistor circuit. The monostable multivibrator 10 is configured to operate in conjunction with a starting switch 12, and the transistor circuit 11 is configured to be driven by the monostable multivibrator 10.

In the circuit of this embodiment configured as described above, when the starting switch 12 is turned on, the monostable multivibrator 10 is turned on for a certain period of time, and the transistor circuit 11 is also turned on during this period. The motor drive current is limited to zero within a certain period of time after the power is turned on. When the multivibrator 10 turns off after a certain period of time, the transistor circuit 11 also turns off, and the current limiting circuit 9
returns the limit value to the predetermined current value. At this time, the drive circuit starts to flow current, but since the set value of the current limit circuit 9 increases from zero, the current cannot flow beyond this value, and the set value of the current limit circuit 9 reaches the predetermined value. When the value is reached ζ
The motor drive current also increases to this value and no longer flows. Thereby, the drive current of the motor can be limited to a desired value.

Figure 2 shows an example using a monostable multivibrator for a relatively simple configuration with a start switch, but when the motor control circuit is built into the device and the motor is started and stopped using control signals. It goes without saying that the same functions can be performed using control signals.

Further, in the case of the embodiment shown in FIG. 2, the current is initially set to zero, but it is clear that similar effects can be obtained by setting the current to an arbitrary value lower than the predetermined value.

The motor control circuit of the present invention is particularly effective for small-sized equipment in which the motor current at the time of starting is limited. Examples include audio players, video disks, magnetic disk drives, etc.

Figure 3 shows an embodiment in which the present invention is used in a magnetic disk device. 14 is a monostable multivibrator which is tripped by starting, and 15 is a transistor which is driven by this. 18 is a transistor that drives the motor current, this current is detected by a resistor 19 arranged in series, and the resistor 1
A comparator 17 compares the voltage divided by 6a+16b. Monostable multivibrator 1 by start signal
4. The transistor 15 is turned on, the output of the current limiting comparator 17 becomes L level, and the transistor 18 is turned off. Monostable multivibrator14. If the transistor 15 turns off, the comparator 17 becomes the resistor 161L!
Since the current is limited by the voltage determined by 16b, the motor current rises from zero and is limited to a predetermined value.

Effects of the Invention As described above, according to the present invention, in a motor control circuit that includes a drive circuit that drives a motor and a current limiting circuit that ignores the current flowing through the motor and controls it below a certain value, At the start of drive, the current limit value of the current limit circuit is set to a value lower than a predetermined limit value, and then reset to the predetermined limit value, so that the motor current at the start of drive is kept at a constant value. Not only is it possible to limit the amount of current to below, but also it is possible to eliminate the large current caused by turning on the power, so it is possible to cancel out the radiation noise caused by this influence, and it is also possible to prevent malfunctions of other circuits.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional motor control circuit, Fig. 2 is a block diagram showing one embodiment of the present invention, and Fig. 3 is a diagram showing main parts of another embodiment of the present invention.01: Permanent Magnet rotor, 2 Nicheeta coils, 3: Rotation detection circuit, 4 Niswitching transistor, 5: Resistor, 6: Voltage comparison circuit, 7: Transistor, 8: Current detection resistor, 9: Current limiting circuit, 10
: Monostable multivibrator, 11: Transistor circuit, 12: Start switch, 13: Power supply, 14: Monostable multivibrator, 15: Transistor 16: Resistor, 17
: Comparator, 18; Transistor, 19: Current detection resistor. Figure 1] 2 Figure 2

Claims (1)

[Claims] In a DC motor control circuit comprising a drive circuit that drives a DC motor, and a current limit circuit that monitors the current flowing into the DC motor and controls it below a certain value, the current limit value of the current limit circuit is set at the start of driving. A direct current motor control method characterized in that is set to a value lower than a predetermined limit value, and then reset to a predetermined limit value.