JPH08186994A - Motor driving apparatus - Google Patents

Abstract

PURPOSE: To provide a motor driving apparatus for motors requiring no strict control on their rotational speed, that is simply constituted and yet maintains stable rotation to some extent, and that enables system operation even at the time of voltage drop. CONSTITUTION: A motor driving apparatus is provided as such with a means for detecting supply voltage, and means 3, 4, 5, 6 for adjusting power applied to the motor according to the value of supply voltage detected by the detecting means. Thus almost constant speed of motor rotation is maintained regardless of any variation in supply voltage. The adjusting means are so designed that if the value of supply voltage detected by the detecting means falls below a specified value, they will reduce power applied to the motor and thus give priority in applying supply voltage to the other sections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive device suitable for a motor, such as a loading motor of a tape recorder, whose rotation speed does not need to be strictly controlled.

[0002]

2. Description of the Related Art For example, in a device using a battery as a power source, there is a circumstance that it is desired to use the voltage of the battery as it is as a power source for driving a motor, mainly in view of efficiency. Especially when it is a motor for loading in a portable tape recorder or the like and the rotation speed control is not strictly required, it is desired to use the battery voltage as it is. However, the terminal voltage of the battery changes from 1.7V to 0.9V in the case of a 1.5V battery, for example. In many cases, a device using a battery can be connected to an AC adapter so that a commercial AC power source can be used, but when the AC adapter is used, the voltage may be 2 V or higher, for example.

Due to these power supply voltage fluctuations, if the battery voltage or the voltage from the AC adapter is used as it is as the motor drive power supply, the motor rotation speed will fluctuate considerably, so that there is no need for strict rotation speed management. Even with the motor, it is necessary to stabilize the rotation speed by some means. For this reason, conventionally, even for a motor that does not require strict rotation speed control, a stabilized power supply circuit is arranged in the power supply system to execute motor drive with constant power, or a motor constant speed rotation servo system is constructed. I was doing.

[0004]

However, the provision of the stabilized power supply circuit or the servo circuit system complicates the circuit, and a rotation detection mechanism or the like is required when the servo circuit is provided. Therefore, the circuit scale becomes large. Will end up.
In particular, battery driving is often adopted in small and portable devices, and the complication and size increase of circuits poses a serious problem.

Further, when the motor current is increased in order to keep the motor at a constant rotation speed when the voltage is reduced (when the battery is exhausted), the terminal voltage of the battery is lowered, and sufficient power supply voltage cannot be supplied to other circuit parts. The system may go down. For this reason, the system may not start up even if a battery with a sufficient capacity is used in a steady state. For example, when sufficient current is not supplied to other circuit parts such as the system control microcomputer by increasing the current to maintain the rotation speed for the motor that needs to operate at startup, such as a loading motor. Occurs. This phenomenon occurs when the motor current is controlled by the servo circuit or when stable power supply is performed by the stabilized power supply circuit.

[0006]

SUMMARY OF THE INVENTION In view of these problems, the present invention provides a motor drive device for a motor that does not need to be precisely controlled in rotation speed, and has a simple structure to maintain a certain degree of stable rotation. It is an object of the present invention to provide a motor drive device capable of operating the system even when the voltage is reduced.

For this reason, the motor driving device is provided with a detecting means for detecting the power supply voltage and an adjusting means for adjusting the electric power applied to the motor according to the power supply voltage value detected by the detecting means. As a result, the motor rotation speed is kept substantially constant regardless of fluctuations in the power supply voltage.

In the adjusting means, when the power supply voltage value detected by the detecting means becomes smaller than a predetermined value,
By lowering the power applied to the motor, the power supply voltage to other parts is prioritized.

[0009]

[Operation] By adjusting the applied power according to the power supply voltage,
The motor rotation speed can be controlled substantially constant with a simple configuration. Further, by giving priority to the power supply to other circuit parts when the voltage of the battery is reduced, the system operation is not disturbed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor drive device according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Prior to that, a recording / reproducing device will be described as an example of a device equipped with the motor drive device according to the embodiment of FIG. This will be explained briefly.
FIG. 4 shows a circuit block of an apparatus which is a data streamer for recording and reproducing data for a computer by a helical scan method using a magnetic tape as a recording medium.

In FIG. 4, reference numeral 12 denotes an interface for connecting to an external device, and the data supplied from the outside to the interface 12 is the data processing circuit 1.
3 is supplied. The data processing circuit 13 is connected to a data processing memory 14, and performs a process of converting externally supplied data into recording data and a process of converting reproduction data into output data. The data supplied from the outside is divided into predetermined blocks, and the data of the block number and the error correction code are added to each block. These data processing circuits 13 are operated under the control of a central control unit (CPU) 21 which is a microcomputer that controls the operation of each part of the streamer.

Then, the recording data processed for recording by the data processing circuit 13 is subjected to recording modulation processing by the modulation circuit 15 to be a recording signal, and the recording signal is generated by the RF amplifier 1.
Supply to 6 and 17. In this case, RF amplifier 16 and RF
The recording data for one track is alternately supplied to the amplifier 17 (the data for one track is composed of a plurality of blocks). The magnetic heads A1 and A2 in a rotary head drum (not shown) are connected to the RF amplifier 16 via a rotary transformer 18, and the recording RF signal amplified by the RF amplifier 16 is sent to the magnetic head A1. Supply and record on magnetic tape. Further, magnetic heads B1 and B2 in the rotary head drum are connected to the RF amplifier 17 via a rotary transformer 18, and the recording RF signal amplified by the RF amplifier 17 is supplied to the magnetic head B1 to supply the magnetic tape. To record.

Further, the reproduction signals of the magnetic heads A1 and A2 are supplied to the RF amplifier through the rotary transformer 18, and the reproduction signal RF signal amplified by the RF amplifier 16 is detected by the detection circuit 19, The reproduced data and its clock component are detected and supplied to the data processing circuit 13. Further, the reproduction signals of the magnetic heads B1 and B2 are supplied to the RF amplifier 17 via the rotary transformer 18, and the reproduction R amplified by the RF amplifier 17 is reproduced.
The F signal is detected by the detection circuit 20, the reproduction data and the clock component thereof are detected and supplied to the data processing circuit 13.

Then, the data processing circuit 13 performs a synthesizing process for restoring the reproduced data into data for each track by using the data memory 14, and detects an error by using the error correction code added to the reproduced data. And error correction processing. Then, when the data of each track becomes complete data by these processes, it is supplied to the interface 12 together with the clock, and the reproduced data is transmitted to the connected external device side.

A RAM 22 in which a control program and the like are recorded is connected to the central control unit 21 of this example. Then, based on the command from the central controller 21, the rotary head drum motor 24 is driven by the drum motor drive circuit 2
It is rotated at a predetermined speed by the control of 3. In this case, the rotation state of the rotary head drum is detected by the frequency generator (FG) 25. Further, the control motor 27 for winding the magnetic tape mounted on the recording / reproducing apparatus around the drum is driven by the control of the control motor drive circuit 26 based on the command from the central control unit 21. In this case, the sensor 28 detects the winding state of the magnetic tape.

Taking such a tape streamer as an example, the motor drive device of the present embodiment is a control motor 2.
7 will be adopted as the control motor drive circuit 26. The control motor 27 is a motor for loading / unloading operations such as winding a magnetic tape around a drum. Therefore, if the motor rotation speed is kept constant to some extent, there is no problem even if it is not strictly controlled. Absent.

FIG. 1 shows the configuration of the motor drive device of this embodiment, that is, the drive power supply system of this embodiment for the control motor 27. Reference numeral 1 is a battery, which is driven by, for example, two AA batteries at 3V.

Reference numeral 2 is an A / D converter for converting the terminal voltage value of the battery 1 into digital data. For example, 0 to 4.4V is 8
It is converted into data of bits 0 to 255 (00h to FFh). The terminal voltage value data is supplied to the compensation calculation unit 3. The compensation calculation unit 3 calculates P from the terminal voltage value by a predetermined calculation.
A WM control value is generated and supplied to the PWM generator 4. P
The WM generator 4 supplies PWM according to the supplied or PWM control value.
A signal (pulse width modulation signal) is generated and used as a control signal for the driver transistor 5. In the PWM generation unit 4, 0 calculated according to the data value of the terminal voltage of the battery 1
A PWM signal with a duty of 0% to 100% is output corresponding to the PWM control value of ~ 255.

The driver transistor 5 is a switch inserted between the control motor 27 and the battery 1, and while the driver transistor 5 is on, the terminal voltage of the battery 1 remains as it is.
7 is used as driving power. In the case of the present embodiment, the driver transistor 5 is controlled by the PWM signal generated according to the terminal voltage value of the battery 1, so that the voltage applied to the control motor 27 can be fixed even if the voltage of the battery 1 changes. The voltage is applied to make the rotation speed substantially constant.

Reference numeral 6 is a power reduction start detection unit. For example, battery 1
If the voltage after the terminal voltage of 2.0 becomes 2.0V,
At the time of this power reduction, the tape streamer shown in FIG.
When an operation such as recording / fast-forward / fast-reverse is performed and the activation of the control motor 27 is detected, the compensation calculation unit 3 is reduced so as not to hinder operations such as reproduction / recording / fast-forward / fast-reverse. An electric power detection signal is supplied so that the system power supply voltage is given priority over the electric power to the control motor 27. The compensation calculation unit 3 controls the coefficient setting method in the calculation calculation of the PWM control value by the power reduction detection signal so that the voltage applied to the control motor 27 can be lowered when the voltage is reduced. The system power supply voltage is supplied to each unit via the DC-DC converter 7. The DC-DC converter 7 is, for example, 4.4V output.

Actual compensation calculation unit 3 and power reduction start detection unit 6
The operation of can be realized by software. This arithmetic processing operation is shown as a flowchart in FIG. First step
In F101, the data from the A / D converter 2 is taken in as the terminal voltage value V _BT of the battery 1. Next, the terminal voltage value V _BT is 2V
Whether or not the following is detected (F102). That is, it is determined whether or not it is in the reduced voltage state. It should be noted that this process is the process of the power reduction start detection unit 6, and if the compensation calculation unit 3 is considered,
The processing steps to be performed are set according to the presence or absence of the detection signal from the power reduction activation detection unit 6.

In a normal state, that is, when the terminal voltage value V _BT is larger than 2 V, the process proceeds to step F104, and first, the terminal voltage value V _BT.
Is greater than or equal to the upper limit level LIM. The upper limit level is the upper limit that can be correctly calculated as the calculation (division) operation of the compensation calculation unit. For example, in the case of an 8-bit calculation output, if the division result exceeds 255, calculation cannot be performed. LIM is set. When the terminal voltage value V _BT is equal to or higher than the upper limit level LIM, the PWM control value is forcibly set to the maximum value (FFh in the case of 8 bits) (F109).

If the terminal voltage value V _BT is smaller than the upper limit level LIM, then the terminal voltage value V _BT is compared with the threshold value th (F105). The driver transistor 5 is a non-linear element, and its curve is obtained in advance by measurement. And
The PWM duty with respect to the voltage fluctuation of the battery 1 is approximated by two linear expressions as shown in FIG. The voltage value at the change point of these two linear expressions is set as the threshold value th.

If the terminal voltage value V _BT is greater than or equal to the threshold value th, the PWM control value is obtained from the equation in FIG. 3, so Ku ₁ is substituted as the coefficient HL and Ku as the coefficient B in step F107. ₂ is substituted. On the other hand, if the terminal voltage value V _BT is smaller than the threshold value th, the PWM control value is obtained from the equation in FIG. 3, so Kd ₁ is substituted as the coefficient HL and Kd ₂ as the coefficient B in step F106. Substituted.

Then, in step F108, the PWM control value is obtained by the calculation of PWM = (V _BT / HL) + B using the coefficients HL and B. The upper limit of the PWM control value is “FFh” in step F109, that is, P
The WM control value is set between "00h" and "FFh" according to the terminal voltage of the battery 1.

Then, in step F110, the calculated PW
The M control value is supplied to the PWM generator 4, and a PWM signal as a control signal for the driver transistor 5 is generated. That is, the PWM control value of "00h" to "FFh" is converted into the PWM signal of the duty of 0% to 100% and output. By this operation, even if the terminal voltage of the battery 1 fluctuates, the electric power applied to the control motor 27 is compensated to be substantially constant, and the rotation speed is kept substantially constant. Therefore, a complicated servo circuit and a stabilizing power supply can be eliminated.

By the way, if a positive result is obtained in step F102, that is, when the terminal voltage of the battery 1 is reduced to 2 V or less, the terminal voltage value V _BT is forcibly set to 2 V in the process of step F103. To be done. Then, after step F104, the terminal voltage value V _BT is regarded as 2 V, the PWM control value is calculated, and the driver transistor 5 is driven by the PWM signal corresponding thereto. That is, even if the terminal voltage of the battery 1 is changed to 1.9V, 1.8V, 1.7V ..., It is always regarded as 2V and the driver transistor 5 is driven. The amount of current generated gradually decreases as the terminal voltage decreases. That is, at the time of power reduction, the voltage applied to the control motor 27 is reduced and the current amount is reduced, so that the current amount of the battery 1 is also reduced.
The terminal voltage of will not drop significantly.

Therefore, the DC-DC converter 7 operates normally and can supply power to the central controller 21 and other circuit parts in FIG. 4, and can properly operate as a tape streamer. Of course, the rotation speed of the control motor 27 becomes slower and the loading operation becomes slower, but this does not hinder the function of the tape streamer. In this case, the data backup operation can be performed even when the voltage is reduced, and thus the performance of the device can be significantly improved. In addition, reducing the motor current to reduce the total power at the time of power reduction also extends the battery life.

Although this embodiment has been described by taking an example of application to a tape streamer as a digital data recording / reproducing device, the motor drive device of the present invention can be applied to various devices. For example, it is suitable for a loading motor in a CD player, a mini disc player, etc., and a motor for conveying a recording medium in a changer player.

[0030]

As described above, the motor drive device of the present invention comprises the detecting means for detecting the power supply voltage and the adjusting means for adjusting the electric power applied to the motor according to the power supply voltage value detected by the detecting means. Since the motor rotation speed is kept substantially constant regardless of fluctuations in the power supply voltage, complicated circuit means such as a stabilizing power supply and a servo circuit are unnecessary for controlling the motor rotation speed to be substantially constant. Reduction is realized, and it is suitable for small equipment.

In the adjusting means, when the power supply voltage value detected by the detecting means becomes smaller than a predetermined value,
By lowering the power applied to the motor, the power supply voltage to other parts is prioritized, which gives priority to the operation of other circuit parts when the voltage is reduced and even when the voltage is reduced. It is possible to carry out an important operation.

[Brief description of drawings]

FIG. 1 is a block diagram of a motor drive device according to an embodiment of the present invention.

FIG. 2 is a flowchart of a compensation calculation operation of the motor drive device according to the embodiment.

FIG. 3 is an explanatory diagram of a threshold value of a compensation calculation operation of the motor drive device according to the embodiment.

FIG. 4 is a block diagram of a tape streamer on which the motor drive device according to the embodiment is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 A / D converter 3 Compensation calculation unit 4 PWM generation unit 5 Driver transistor 6 Power reduction start detection unit 7 DC-DC converter 27 Control motor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02P 7/00 V

Claims (2)

[Claims] 1. A detection means for detecting a power supply voltage, and an adjustment means for adjusting an electric power applied to the motor according to a power supply voltage value detected by the detection means, wherein the motor rotation speed is independent of fluctuations in the power supply voltage. A motor drive device characterized in that the motor drive device is kept substantially constant. 2. When the power supply voltage value detected by the detection means becomes smaller than a predetermined value, the power applied to the motor is lowered so that the power supply voltage supply to other parts is prioritized. The motor drive device according to claim 1, wherein the motor drive device is configured.