JPH05122995A - Control circuit for stepping motor - Google Patents

Abstract

PURPOSE:To provide a control circuit for a stepping motor in which noise generated from the motor can be reduced. CONSTITUTION:Pulses formed by constant-current integrators 11, 12, 21, 22 and inverters 13, 14, 23, 24 are combined by switching operations of switches 15, 16, 25, 26. The waveform of the combined pulses, has for example, smooth rise and fall characteristic like a trapezoidal wave. Since the pulses are output from drivers 17, 18, 27, 28, the rotation of a stepping motor becomes very smooth. Thus, as a result, noise generated upon rotation of the motor is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to audio equipment such as cassette tape recorders, video cameras and VTs.
The present invention relates to a control circuit of a stepping motor used for video equipment such as R.

[0002]

2. Description of the Related Art Stepping motors are used in various audio equipment and video equipment because they can perform accurate control without performing complicated control. The stepping motor is driven based on a pulsed drive signal. As an example of the drive signal, there is a signal as shown in FIG. The pulse waveforms indicated by D ₁ and D ₂ in the figure are drive signals input to the stator coil of the stepping motor. The stepping motor is rotated by applying such drive signals to the respective stator coils in different phases. The rotation speed of the stepping motor can be changed by changing the pulse frequency of the drive signal and the phase difference thereof.

[0003]

However, in such a conventional stepping motor control circuit,
Since the stepping motor is rotated by the drive signal having such a steep rise and fall characteristic, a counter electromotive force is generated in the stator coil at the rise and fall of the drive signal, and the stepping motor is driven. The motor is apparently the same as being driven by a drive pulse including a back electromotive force as shown by Φ ₁ and Φ ₂ in FIG. Note that Φ in the figure
Waveform described under ₁ and [Phi ₂ is a drawing [Phi ₁ and [Phi ₂ of inverted waveform. Microscopically, the back electromotive force causes uneven rotation of the stepping motor, which causes noise in the audible region. The generation of such noise is a particular problem for video cameras. This noise is recorded as voice noise together with the image through the microphone.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide a control circuit for a stepping motor capable of reducing noise generated from the stepping motor.

[0005]

In order to achieve the above object, the present invention provides a pulse generating means for generating a pulse having a slow rising / falling characteristic based on a rotation command signal output from the outside, and Output means for outputting the pulse generated from the pulse generation means to the stepping motor.

[0006]

According to the stepping motor control circuit of the present invention constructed as described above, a pulse having a slow rising / falling characteristic is generated from the pulse generating means, and this pulse is outputted from the output means. In addition, the stepping motor is driven by, for example, a trapezoidal drive pulse having no protruding rising and falling portions, and the rotation thereof becomes very smooth.
Therefore, as a result, the noise generated with the rotation of the stepping motor is reduced.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control circuit of a stepping motor according to the present invention, and FIG. 2 is a timing chart of pulses output from each part of the circuit shown in FIG. The control terminals 10 and 20 shown in FIG. 1 are terminals connected to a pulse generation circuit configured by using an externally provided microcomputer or the like. These terminals 10, 20
A rotation command signal is input to. This rotation command signal is a rectangular wave as shown in FIG. 2A with a phase difference of 90 degrees or -90 degrees. The constant current integrator circuits 11, 12, 21, 22 are configured to charge the capacitor from the constant current source when the input signal is in the “H” state, and output the charging result. Circuit. Inversion circuits 13, 14, 23, 24
Is a circuit that inverts an input signal and outputs it. The switches 15, 16, 25 and 26 have control terminals 10 and 20.
It is a switch that switches the connection contact based on the "H"-"LOW" change of the rotation command signal input from. The drive circuits 17, 18, 27, and 28 amplify the input signal and stator coil 30 of the stepping motor 30.
It outputs to A and 30B, and functions as an output means. The constant current integrator circuits 11, 12, 2
1, 22 and the inverting circuits 13, 14, 23 and 24 and the switches 15, 16, 25 and 26 respectively form pulse generating means.

The control circuit having the above-mentioned structure functions as follows. In describing this function, the circuits that output pulses to the stator coils 30A and 30B have exactly the same functions, so only the function that outputs pulses to the stator coil 30A will be described. To First, when a rectangular pulse as shown in A of FIG. 2 is input from the control terminal 10,
This rectangular pulse is input to the constant current integrator circuit 11, and at the same time, the rectangular pulse as shown by B in FIG. .. At this time, since the "H" signal is input to the control terminal 10, the switches 15 and 16 set their connection contacts as shown in the figure. In this state, since the "H" signal is input to the constant current integrator circuit 11, a signal having an integrated waveform as shown in C of FIG. This signal will be output to the switches 15 and 16. On the other hand, since the “LOW” signal is input to the constant current integrator circuit 12, the input pulse is output as it is, and from here on, the waveform as shown in D of FIG. Signal of the inversion circuit 14
Is output to. The constant current integrating circuits 11 and 12
, Which integrates the input signal when it rises from "LOW" to "H", they generate pulses with the waveforms shown in C and D of FIG. Will be output. The inverting circuit 14 outputs a signal having a waveform shown in E in the figure, which is obtained by inverting the waveform shown in D in the figure, toward the switches 15 and 16. When the pulse input from the control terminal 10 becomes “LOW”, the switches 15 and 16
Sets its connection contacts opposite to the state shown. By the switching of the switches 15 and 16, the drive circuit 17 outputs a trapezoidal wave as shown by F in the figure, while the drive circuit 18 outputs a trapezoidal wave as shown by G in the figure. .. These trapezoidal waves are generated by the stator coil 30 of the stepping motor 30.
It will be output to A.

As a result, the stepping motor 30 is driven by the trapezoidal wave pulse, and even if the counter electromotive force of the stator coil 30A is taken into consideration, the portion protruding at the rising and falling portions as shown in FIG. A pulse that does not exist causes its rotation to occur. If the rising and falling times of this trapezoidal wave are made appropriate, the stepping motor 30 can be driven with an ideal pulse waveform. As a result, microscopically, the stepping motor 30 starts to rotate slowly when the pulse rises, and stops rotating slowly when the pulse rises. Therefore, the unevenness of rotation becomes extremely small, and the noise level becomes extremely small. In the above embodiments, the trapezoidal wave is generated by way of example, but the invention is not limited to this. For example, the rising and falling edges may be curved. .. In short, any waveform can be applied as long as it allows the stepping motor 30 to start to rotate slowly at the time of its rise and to stop its rotation at the time of its fall.

[0010]

As is apparent from the above description, according to the present invention, it is possible to reduce the noise generated by the rotation of the stepping motor.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of a stepping motor according to the present invention.

FIG. 2 is a timing chart of pulses output from each unit of the circuit shown in FIG.

FIG. 3 is a timing chart of pulses output from each unit of a conventional stepping motor control circuit.

[Explanation of symbols]

11, 12, 21, 22 Constant current integrating circuit (pulse generating means) 13, 14, 23, 24 Inversion circuit (pulse generating means) 15, 16, 25, 26 Switch (pulse generating means) 17, 18, 27, 28 Drive circuit (output means)

Claims (1)

[Claims] 1. A pulse generating means for generating a pulse having a slow rising / falling characteristic based on a rotation command signal output from the outside, and an output means for outputting the pulse generated by the pulse generating means to a stepping motor. And a control circuit for a stepping motor.