JPH02184283A - Dc motor driving circuit - Google Patents

Abstract

PURPOSE:To reduce the affection of the number of rotation and increase reliability by a method wherein an overcurrent reference signal is changed in accordance with the number of rotation to slow down the rise-up of a driving current by an affection due to the counter electromotive force of a coil. CONSTITUTION:When the rotation of a DC motor is started, a reference voltage generating circuit 13 outputs an overcurrent reference signal 14 in accordance with the number of the rotation. The reference voltage generating circuit 13 outputs the overcurrent reference signal 14, showing the maximum current of a power source, when the number of rotation is low or the affection of a counter electromotive force generated by the coil of the DC motor is little and the rise-up of a current detecting signal 10 is quick. However, the average current of the power source is reduced and the supplying capacity of the power source becomes capable of being satisfied when the number of rotation is increased and the rise-up of the current detecting signal 10 is slowed down by the affection of the counter electromotive force generated by the coil of the DC motor.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a DC motor drive circuit that controls a DC motor to a desired rotation speed, and in particular to a DC motor drive circuit that controls a DC motor to a desired rotation speed. is connected to a DC motor drive circuit that outputs.

[Prior Art] FIG. 2 is a block diagram of a conventional DC motor drive circuit. Note that the DC motor in the figure is used to rotate the disc-shaped recording medium.

In the figure, 1 is a recording medium, 2 is a DC motor for rotating the recording medium 1, and this DC motor 2 is equipped with a Hall element that changes the output level depending on the rotational position. Further, reference numeral 3 denotes a rotation speed detection circuit, which outputs a rotation speed detection signal 5 by measuring the pulse width of the Hall element output signal 4 outputted by the Hall element of the DC motor 2.

On the other hand, 6 is a reference clock generation circuit, which outputs a reference rotation speed signal 7 corresponding to an arbitrary rotation speed.

This reference rotational speed signal 7 is added to the rotational speed detection signal 5, and a rotational speed error signal 8 indicating the difference in rotational speed is input to a power amplifier (power amplification circuit) 9.

Then, the power amplifier 9 outputs a current detection signal 10 proportional to the rotational speed error signal 8, and the DC motor 2 rotates at a predetermined rotational speed.

However, when the DC motor 2 starts rotating, the current detection signal 10 becomes larger than when the DC motor 2 rotates normally, so if this continues, the power source will exceed its average supply capacity. Therefore, in order to satisfy the current capacity of the power supply, a power amplifier inoperation signal generation circuit 11 is used to control the power amplifier 9. That is, the current detection signal 10 is inputted to the power amplifier inoperation signal generating circuit 11, and the power amplifier inoperation signal 12 is outputted.

Now, FIG. 3 is a block diagram of the conventional power amplifier non-operation signal generation circuit shown in FIG. 2, and FIG. 4 is a waveform diagram showing the operating waveforms at the time of start-up of the power amplifier non-operation signal generation circuit. .

In FIG. 3, reference numeral 13 denotes a reference voltage generation circuit, which outputs an overcurrent reference signal 14 that serves as a criterion for determining whether or not an overcurrent state exists. That is, the overcurrent reference signal 14 is set to be the maximum current at the instant of power supply. Next, 15 is a comparator which inputs the current detection signal 10 and the overcurrent reference signal 14, and outputs the overcurrent detection signal 16 when the current detection signal 10 is larger. A one-shot circuit 17 outputs a power amplifier disable signal 12 for disabling the power amplifier 9 when the overcurrent detection signal 16 is input.

That is, the power amplifier inoperation signal 12 is used to control the average current of the current detection signal 10 to be the average current supplied by the power supply. For this reason, the overcurrent reference signal 14 and the power amplifier inoperation signal 12 are preset to constant values according to the power supply capacity.

However, the rise of the current detection signal 10 is delayed due to the counter electromotive force of the coil generated by the rotation of the DC motor 2.

Figure 5 shows the third example when the rise of the current detection signal is slow.
FIG. 3 is a waveform diagram showing operating waveforms of the power amplifier inoperation signal generation circuit shown in the figure.

As shown in FIG. 5, in such a state, the average current of the power supply was larger than that at the start of startup, and the power supply exceeded its average supply capacity.

[Problems to be solved] In the conventional DC motor drive circuit described above, the overcurrent reference signal is fixed at a constant value in advance, so if the rise of the current detection signal is delayed, the average current of the power supply becomes larger than at the start of startup. Therefore, there is a problem in that the power source cannot supply a DC motor drive current exceeding its average supply capacity.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly reliable DC motor drive circuit that is not affected by the number of rotations.

[Means for Solving the Problem] In order to achieve the above object, the DC motor drive circuit of the present invention includes a rotation speed detection circuit that detects the rotation speed of the DC motor and outputs a rotation speed detection signal, and a rotation speed detection circuit that detects the rotation speed of the DC motor and outputs a rotation speed detection signal. A reference clock generation circuit that outputs a reference signal for controlling the rotation speed to make it arbitrary; and a current that detects a rotation error from the rotation speed detection signal and the reference signal for controlling the rotation speed and outputs a drive current for the DC motor. A DC device comprising an amplifier circuit and a power amplifier circuit inoperation signal output circuit that outputs a fixed difference signal for preventing an overcurrent state to the current amplifier circuit.
In the motor drive circuit, the power amplifier circuit inoperation signal output circuit inputs the rotation speed detection signal, and an overcurrent reference signal generation circuit that outputs an overcurrent reference signal corresponding to the rotation speed; and an overcurrent state detection circuit that determines whether or not there is an overcurrent state based on the rotational speed detection signal and outputs the above-mentioned inoperation signal when it is determined that there is an overcurrent state.

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a block diagram of a power amplifier inoperation signal generation circuit in a DC motor drive circuit according to an embodiment of the present invention. Note that parts common to or corresponding to those of the conventional example are denoted by the same reference numerals.

The difference between the power amplifier inoperation signal generation circuit shown in the same figure and the conventional power amplifier inoperation signal generation circuit shown in FIG. It is located in the voltage generation circuit 13. That is, when the DC motor 2 starts rotating, the reference voltage generation circuit 13 outputs the overcurrent reference signal 14 corresponding to the rotation speed.

A DC configured with such a reference voltage generation circuit 14
The motor drive circuit outputs an overcurrent reference signal 14 indicating the maximum current of the power supply when the rotation speed is low, that is, when the influence of the back electromotive force due to the coil of the DC motor 2 is small and the rise of the current detection signal 10 is fast. .

However, when the rotational speed becomes high and the rise of the current detection signal 10 becomes slow due to the influence of the counter electromotive force generated by the coil, the level of the overcurrent reference signal 18 indicated by the broken line shown in FIG. 5 is lowered. As a result, the average current of the power supply is reduced, and the supply capacity of the power supply can be satisfied.

As described above, the power amplifier inoperation signal output circuit of this embodiment includes an overcurrent reference signal generation circuit that receives a rotational speed detection signal as input and outputs an overcurrent reference signal corresponding to the rotational speed, and a circuit that outputs an overcurrent reference signal corresponding to the rotational speed. The comparator inputs and compares the rotation speed detection signal and outputs an overcurrent detection signal when the rotation speed detection signal is larger. It consists of a one-shot circuit that outputs an operating signal.

Therefore, in this embodiment, an overcurrent state detection circuit is configured by a comparator and a one-shot circuit.

[Effects of the Invention] As explained above, the present invention changes the overcurrent reference signal according to the rotation speed, thereby slowing down the rise of the drive current due to the influence of the back electromotive force of the coil, and preventing the power supply from exceeding its supply capacity. This has the advantage that it is possible to prevent the disadvantage of not being able to supply a DC motor drive current due to the current being lost, and to provide a highly reliable DC motor drive circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a power amplifier inoperation signal generation circuit in a DC motor drive circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional DC motor drive circuit, and FIG. 3 is similar to FIG. 4 is a waveform diagram showing the operating waveforms at the start of activation of the power amplifier inoperative signal generating circuit, and FIG. 5 is a waveform diagram showing the operating waveforms when the current detection signal rises slowly. 4 is a waveform diagram showing operating waveforms of the power amplifier inoperation signal generation circuit shown in FIG. 3. FIG. DC motor rotation speed detection circuit Reference clock generation circuit Power amplifier: Power amplifier inoperable signal generation circuit 13: Reference voltage generation circuit 5: Comparator 17: One-shot circuit

Claims (1)

[Claims] a rotation speed detection circuit that detects the rotation speed of the DC motor and outputs a rotation speed detection signal; a reference clock generation circuit that outputs a reference signal for rotation speed control to set the rotation speed of the DC motor to an arbitrary value; A current amplifier circuit that detects a rotation error from the rotation speed detection signal and a reference signal for rotation speed control and outputs a drive current to the DC motor, and a fixed difference signal for preventing an overcurrent state for this current amplifier circuit. In the DC motor drive circuit, the power amplifier circuit non-operation signal output circuit receives the rotation speed detection signal and outputs an overcurrent reference signal corresponding to the rotation speed. an overcurrent reference signal generation circuit that outputs an overcurrent reference signal, and an overcurrent circuit that determines whether or not there is an overcurrent condition based on the overcurrent reference signal and the rotation speed detection signal, and outputs the above non-operation signal when it is determined that there is an overcurrent condition. A DC motor drive circuit comprising a state detection circuit.