JP5349191B2 - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To change switching speed to three levels or more without installing an external component, and to make the switching speed variable, according an external voltage in a middle speed zone. <P>SOLUTION: A drive signal generating section generates a drive signal to a MOS-FET by using an input signal and an output signal of an RS flip flop. A motor drive section allows a current to flow to a motor winding via the MOS-FET and drives a motor. A current detecting section detects a current flowing in the motor drive section and drives the motor at a constant current, by triggering the RS-flip-flop by this current detection. An oscillator oscillates a timing signal and resets the RS-flip-flop by using the signal. A frequency switching section changes an oscillation frequency of the oscillator at three levels or more according to an external voltage value and makes the switching speed variable, according to the external voltage in the middle speed zone. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a motor drive device suitable for use in driving a stepping motor.

  Conventionally, as shown in FIG. 9, a motor driving device that drives a stepping motor with a constant current includes a driving signal generation unit 101 that generates a driving signal and MOS-FETs (Metal Oxide Field Effect Transistors) M <b> 101 to M <b> 104. A current is passed through the winding L101 to drive the motor, a motor driving unit 102 for detecting the current of the motor winding L101, an oscillator unit 104 for oscillating a timing signal, and a detection output of the current detecting unit 103. And an RS flip-flop 105 which is reset by a timing signal. In such a motor drive device, the current detection unit 103 detects the current of the motor winding L101, triggers the RS flip-flop 105 by this detection output, and resets the RS flip-flop 105 by the timing signal from the oscillator unit 104. The output of the RS flip-flop 105 is supplied to the drive signal generation unit 101 to drive the motor with a constant current.

  For example, as shown in Patent Document 1, when a non-rectifying motor causes electromagnetic induction accompanying rotation of the motor due to the rotation of the motor and a generated voltage is induced, the induced voltage and the timing signal are synchronized. By doing so, the thing which suppressed the electromagnetic noise and commutation noise from a motor is disclosed.

JP-A-5-328783

  In the stepping motor driving apparatus described above, when the switching speed of the stepping motor is low, the winding ripple current becomes large, the average current is lowered, and the rotation efficiency is lowered. In particular, when the winding current is small, the winding ripple becomes occupied. Therefore, it is desired to increase the switching speed from the aspect of reducing the winding ripple current.

  On the other hand, when the switching speed of the stepping motor is increased, the switching loss increases due to the high-speed switching, and the generated noise needs to be processed. Further, when the switching speed is high, efficiency is deteriorated unless elements having good switching characteristics are used for the output transistor and the flywheel diode. Further, when the switching speed is high, when a motor with a small winding current and a small inductance value is driven, a current rising phenomenon occurs.

  Therefore, if a large winding ripple current is a problem, increase the switching speed to reduce the winding ripple current. If an increase in switching loss is a problem, decrease the switching speed. Thus, it is desirable to reduce the switching loss.

  However, it is difficult to easily change the switching speed in the above-described conventional stepping motor driving apparatus. That is, in the conventional motor driving apparatus shown in FIG. 9, the external connection terminal 107 is derived, and the oscillation frequency of the oscillator unit 104 is set by the time constant of the capacitor C101 and the resistor R101 connected to the external connection terminal 107. It is the composition to do. In such a configuration, in order to change the switching speed, it is necessary to mount external components such as the capacitor C101 and the resistor R101, the number of parts increases, and the switching speed cannot be easily changed.

  Moreover, in what is shown by patent document 1, since it is necessary to synchronize an induced voltage and a timing signal, the frequency of a timing signal cannot be changed easily.

  Therefore, the present invention has been made in view of the above-described problems, and changes the switching speed to three or more stages without mounting external parts, and in the medium speed range, according to the external input voltage. An object of the present invention is to provide a motor drive device capable of varying the switching speed.

  The present invention proposes the following items in order to solve the above-described problems.

  (1) The present invention includes an oscillator unit that oscillates a timing signal (for example, equivalent to the oscillator unit 4 in FIG. 1), and a drive signal generation unit that generates a drive signal based on the timing signal from the oscillator unit (for example, 1 and a motor drive unit (for example, equivalent to the motor drive unit 2 in FIG. 1) that drives a motor by the drive signal from the drive signal generation unit. The frequency switching unit (for example, FIG. 5) varies the oscillation frequency of the oscillator unit in three stages or more according to the external input voltage value, and varies the oscillation frequency in the medium speed region corresponding to the external input voltage value. 1 is equivalent to the frequency switching unit 6).

  According to the present invention, the oscillation frequency of the oscillator unit can be changed in three or more stages according to the voltage value from the external input, and the oscillation frequency can be varied corresponding to the external input voltage value in the medium speed range. To do. Therefore, the switching speed can be easily changed by changing the oscillation frequency of the oscillator unit as described above.

  (2) The present invention proposes a motor driving device characterized by driving the motor with a constant current with respect to the motor driving device of (1).

  According to the present invention, the oscillation frequency of the oscillator unit can be easily changed by a voltage value from an external input with a constant current drive motor.

  (3) The present invention proposes a motor driving device according to (1) or (2), wherein the motor is a stepping motor.

  According to the present invention, the oscillation frequency of the oscillator unit can be easily changed by the voltage value from the external input by the stepping motor.

  (4) According to the present invention, in the motor drive device of (1) to (3), the frequency switching unit includes two or more fixed current supply sources (for example, equivalent to the constant current sources Iref1 and Iref2 in FIG. 5) and the above A variable current supply source (for example, corresponding to a current mirror circuit including Q4 and Q5 in FIG. 5) that varies a current value according to an external input voltage value, and the external input voltage value corresponds to the medium speed range. In the case of a voltage value, a motor driving device is proposed in which the oscillation frequency of the oscillator unit is set by switching to the variable current supply source.

  According to this invention, the amount of current supplied to the oscillator unit is varied according to the voltage value from the external input, and the oscillation frequency of the oscillator unit is varied, so by precisely controlling the amount of current, The oscillation frequency of the oscillator unit can be varied. In addition, when a voltage value from an external input corresponding to the medium speed range is detected, the oscillation frequency of the oscillator unit is varied using a variable current supply source. In addition, the oscillation frequency of the oscillator unit can be varied.

  (5) The present invention proposes a motor drive device according to (4), wherein the current value of the variable current supply source varies linearly according to the external input voltage value. doing.

  According to the present invention, the current value of the variable current supply source varies linearly according to the external input voltage value. Therefore, by controlling the external input voltage value, the oscillation frequency of the oscillator unit can be varied more finely.

  According to the present invention, the oscillation frequency of the oscillator unit can be changed in three or more stages according to the voltage value from the external input. Therefore, when the winding ripple current is large, there is an effect that the switching speed can be increased and the winding ripple current can be reduced. Further, when the switching loss increases, there is an effect that the switching loss can be reduced by reducing the switching speed.

  Further, in the medium speed range, the oscillation frequency is varied in accordance with the external input voltage value. Therefore, there is an effect that the oscillation frequency of the oscillator unit can be varied more finely by controlling the external input voltage value. Furthermore, since the oscillation frequency of the oscillator unit can be changed by the voltage value of the external input, there is an effect that external parts are not required and external parts can be reduced.

It is a block diagram which shows the structure of the motor drive device of this embodiment. It is a wave form diagram of each part in the case of low speed operation of the motor drive device of this embodiment. It is explanatory drawing of the flow of the electric current in each period of the motor drive device of this embodiment. It is a wave form diagram of each part in the case of high-speed operation of the motor drive device of this embodiment. It is a block diagram which shows the structure of the oscillator part and frequency switching part in the motor drive device of this embodiment. It is a wave form diagram used for operation | movement description of the frequency switching part in the motor drive device of this embodiment. It is a figure which shows the external input voltage value of the frequency switching part in the motor drive device of this embodiment, and the operation state of transistor Q1, Q2, Q3. It is a wave form diagram used for operation | movement description of the oscillator part in the motor drive device of this embodiment. It is a block diagram which shows an example of the conventional motor drive device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements and the like, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

<Configuration of motor drive device>
FIG. 1 shows a configuration of a motor driving apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the motor drive device according to the embodiment of the present invention includes a drive signal generation unit 1, a motor drive unit 2, a current detection unit 3, an oscillator unit 4, an RS flip-flop 5, and a frequency. And a switching unit 6. In addition, the circuit of each part which comprises these motor drive devices is integrated circuit.

  The drive signal generation unit 1 receives the input control signal IN and the output signal from the RS flip-flop 5 and generates drive signals for the MOS-FETs M1 to M4. The motor driving unit 2 drives the motor by causing a current to flow through the motor winding L1 by the MOS-FETs M1 to M4.

  The current detection unit 3 detects the current flowing through the motor drive unit 2 by the detection resistor Rs1, compares the detected value with the reference voltage Vref by the comparator CMP1, and triggers the RS flip-flop 5 by the output. The motor is driven at a constant current. The oscillator unit 4 oscillates a timing signal, and resets the RS flip-flop 5 with this timing signal. The frequency switching unit 6 switches the oscillation frequency of the oscillator unit 4 according to the external voltage value input from the external input terminal 7.

  The motor winding L1 is connected between the MOS-FETs M1 to M4. That is, one end is connected to the source of the MOS-FET M1 and the drain of the MOS-FET M2, and the other end is connected to the source of the MOS-FET M3 and the drain of the MOS-FET M4. The drain of the MOS-FET M1 and the drain of the MOS-FET M3 are connected to the power supply Vmm.

  Further, the source of the MOS-FET M2 and the source of the MOS-FET M4 are grounded via the detection resistor Rs1.

<Waveforms of each part of motor drive unit (at low speed)>
FIG. 2 shows the waveform of each part of the motor drive device of this embodiment.

  As shown in FIG. 2A, when the input control signal IN becomes high level at time t0, the FET on period is entered, and the MOS-FETs M1 and M4 are excited by the excitation signal. When the MOS-FETs M1 and M4 are turned on, an excitation current ia flows from the power supply Vmm through the MOS-FET M1, the motor winding L1, and the MOS-FET M4 as shown in FIG. Thereby, as shown in FIGS. 2B and 2E, the current IM1 of the MOS-FET M1 and the current IM4 of the MOS-FET M4 increase.

  The current flowing through the motor drive unit 2 is detected by the detection resistor Rs1 of the current detection unit 3. As shown in FIG. 2 (F), the detection voltage Vs of the detection resistor Rs1 rises due to the excitation current ia flowing from the power source Vmm through the MOS-FET M1, the motor winding L1, and the MOS-FET M4.

  The detection voltage Vs of the detection resistor Rs1 is supplied to one input terminal of the comparator CMP1. The reference voltage Vref is supplied to the other input of the comparator CMP1. When the detection voltage Vs (FIG. 2F) of the detection resistor Rs1 exceeds the reference voltage Vref at time t1, the output of the comparator CMP1 becomes high level.

  As a result, a high level is supplied to the set input S of the RS flip-flop 5 as shown in FIG. When a high level is supplied to the set input S of the RS flip-flop 5, the RS flip-flop 5 is triggered and the output Q of the RS flip-flop 5 becomes a high level as shown in FIG.

  The output of the RS flip-flop 5 is supplied to the drive signal generator 1. When the output Q of the RS flip-flop 5 becomes high level, the constant current control is activated, the FET on period is changed to the flywheel period, the MOS-FET M1 is turned off, and the MOS-FET M2 is turned on after the MOS-FET M1 is turned off. .

  In the flywheel period from time t1 to time t2, the MOS-FET M2 and the MOS-FET M4 are on, and as shown in FIG. 3B, the flywheel current ib is the motor winding L1, the MOS-FET M4. , Flows through the path of the MOS-FET M2 and returns to the motor winding L1. As a result, the current IM2 of the MOS-FET M2 and the current IM4 of the MOS-FET M4 decrease as shown in FIGS. 2C and 2E.

  The oscillator unit 4 generates a timing signal having a predetermined frequency. This timing signal is supplied to the reset input R of the RS flip-flop 5 as shown in FIG. When the timing signal from the oscillator unit 4 becomes high level at time t2, as shown in FIG. 2 (K), the output Q of the RS flip-flop 5 becomes low level and changes from the flywheel period to the FET on period.

  In the FET ON period from time t2 to t3, the MOS-FET M1 and the MOS-FET M4 are ON as described above, and excitation is performed from the power source Vmm via the MOS-FET M1, the motor winding L1, and the MOS-FET M4. A current flows, and the current IM1 of the MOS-FET M1 and the current IM4 of the MOS-FET M4 increase. When the detection voltage Vs of the detection resistor Rs1 exceeds the reference voltage Vref at time t3, the output of the comparator CMP1 becomes high level, and the RS flip-flop 5 is triggered. And it becomes a flywheel period again from time t3 to time t4.

  Thereafter, the FET on period and the flywheel period are repeated in the same manner.

  When the input control signal IN (FIG. 2A) changes from the high level to the low level at time tn-1, the flyback period starts, the MOSFET M1 and the MOS-FET M4 are turned off, and the MOSFET M2 and the MOS-FET M3 are turned on. Thereby, at time tn-1 to time tn, as shown in FIG. 3C, the regenerative current ic flows through the path of the MOS-FET M2, the motor winding L1, and the MOS-FET M3, and is regenerated to the power source Vmm. Further, through the FET ON period, the flywheel period, and the flyback period, as shown in FIG. 2H, a current having an upper limit v3 and a lower limit v4 flows through the capacitor C of the oscillator unit 4.

  As described above, in the motor drive device of the present embodiment, the winding current is detected from the detection output of the detection resistor Rs1, the RS flip-flop 5 is set with this detection output, and the RS signal is output from the timing signal from the oscillator unit 4. By resetting the flip-flop 5, the stepping motor is driven with a constant current by repeating the FET ON period and the flywheel period.

  In a stepping motor, when the switching time is low, the winding ripple current increases, which may decrease the average current and decrease the rotation efficiency. In particular, when the winding current is small, the winding ripple becomes dominant.

  On the other hand, when the switching time is high, the switching loss increases because of the high-speed switching operation. In this case, it is necessary to process generated noise. Furthermore, unless elements having good switching characteristics are used for the output transistor and the flywheel diode, the efficiency is deteriorated. When a motor having a small winding current and a small inductance is driven, a current rising phenomenon occurs.

  Therefore, in the motor drive device according to the embodiment of the present invention, as shown in FIG. 1, the frequency switching unit 6 is provided, and the oscillation frequency of the timing signal from the oscillator unit 4 can be switched by setting from the external input terminal 7. I can do it.

<Waveforms of each part of motor drive unit (at high speed)>
FIG. 4 shows the waveform of each part when the oscillation frequency of the oscillator part 4 is increased to operate at high speed.
In FIG. 4, it is assumed that the frequency of the timing signal from the oscillator unit 4 is higher than the frequency of the timing signal in the case of the low speed operation shown in FIG. As can be seen from a comparison between FIG. 4 and the waveform shown in FIG. 2, the ripple component (FIG. 4G) of the winding current Iout in the high speed operation is the winding current Iout in the low speed operation. Is smaller than the ripple component (FIG. 2G). Further, as shown in FIG. 4 (H), a current having an upper limit v3 and a lower limit v4 flows through the capacitor C1 of the oscillator unit 4 through the FET on period, the flywheel period, and the flyback period. Although the crest value is the same as that at low speed, the current waveform has a higher frequency than that at low speed.

  In the present embodiment, by switching the oscillation frequency of the oscillator unit 4 according to the voltage value input from the external input terminal 7, when the winding ripple current is large, the switching speed is increased and the winding ripple is increased. The current can be reduced, and when the switching loss increases, the switching speed can be reduced to reduce the switching loss.

  When the switching speed is set to a medium speed, the switching speed changes linearly according to the voltage value input from the external input terminal 7. Therefore, finer switching speed control can be performed as compared with the high speed region and the low speed region, and the switching loss can be reduced while reducing the winding ripple current.

<Configuration of oscillator unit>
Next, the configuration of the oscillator unit 4 that can switch the oscillation frequency according to the voltage value input from the external input terminal 7 will be described.

  FIG. 5 shows the configuration of the oscillator unit 4 and the frequency switching unit 6. As shown in FIG. 5, the oscillator unit 4 includes a comparator CMP5, a switch circuit SW2, a capacitor C1, transfer gates G1 and G2, and inverters INV1 and INV2.

  A capacitor C1 and a switch circuit SW2 are connected between one input of the comparator CMP5 constituting the oscillator unit 4 and the ground. The constant current sources Iref1 and Iref2 are connected to one input of the comparator CMP5 constituting the oscillator unit 4 via the transistors Q2 and Q3 constituting the frequency switching unit 6, and the transistor Q1 is connected to the transistor CMP1. A current mirror circuit consisting of Q4 and Q5 is connected.

<Configuration of frequency switching unit>
The voltage signal input (external input voltage) is connected to the positive terminal of the comparator CMP2 constituting the frequency switching unit 6, the negative terminal of the comparator CMP3, and the positive terminal of the comparator CMP4. The positive terminal of the comparator CMP3 is connected to the power source V1 ( For example, in 1v), the negative terminal of the comparator CMP4 is connected to a power source V2 (for example, 3v), and the negative terminal of the comparator CMP2 is connected to a connection point between the resistors R2 and SW1. The other end of the resistor R2 is connected to the ground potential.

  The output terminal of the comparator CMP2 constituting the frequency switching unit 6 is connected to the gate terminal of SW1, and the other end of SW1 is connected to the transistor Q4. The output terminals of the comparators CMP3 and CMP4 are both connected to the input terminal of the NOR circuit IC1, the output terminal of the comparator CMP3 is connected to the gate terminal of the transistor Q2, and the output terminal of the comparator CMP4 is connected to the gate terminal of the transistor Q3. It is connected. Further, the output terminal of the NOR circuit IC1 is connected to the gate terminal of the transistor Q1.

  The other input of the comparator CMP5 constituting the oscillator unit 4 is connected to the charging upper limit voltage V3 via the transfer gate G1, and is connected to the charging lower limit voltage V4 via the transfer gate G2.

  The output of the comparator CMP5 is output via the inverters INV1 and INV2, and is supplied to the reset input of the RS flip-flop 5. Further, the outputs of the inverters INV1 and INV2 are supplied to the control terminals of the transfer gates G1 and G2 in opposite phases. The transfer gate G1 turns on / off the supply of the charging upper limit voltage V3, and the transfer gate G2 turns on / off the supply of the charging lower limit voltage V4.

<Operation of frequency switching unit>
The operation of the frequency switching unit 6 will be described with reference to the waveform diagram of FIG. 6 and FIG. For example, when the external input voltage value ranges from 0 v to 1 v in the low speed range, 1 v to 3 v range in the medium speed range, and 3 v to Vcc in the high speed range, in the low speed range, as shown in FIG. Va is “high” and Vb and Vc are “low”, so that only the transistor Q2 is turned “ON” as shown in FIG. As a result, the current I2 flows as I4 to the capacitor C1 of the oscillator unit 4.

  In the middle speed range, as shown in FIG. 6, Va and Vb are “low” and Vc is “high”, so that only the transistor Q1 is turned “on” as shown in FIG. Become. At this time, since the comparator CMP2 functions as a buffer, the output corresponding to the external input voltage value is supplied to the current mirror circuit constituted by the transistors Q4 and Q5 as shown in FIG. The corresponding current value is supplied to the capacitor C1 of the oscillator unit 4 with I1 as I4.

  Further, in the case of the high speed region, as shown in FIG. 6, Va and Vc are “low” and Vb is “high”, so that only the transistor Q3 is “on” as shown in FIG. . As a result, the current I3 flows as I4 to the capacitor C1 of the oscillator unit 4.

  That is, the frequency switching unit in the present embodiment can change the oscillation frequency to three or more levels according to the voltage value from the external input, and in the middle speed range, the oscillation frequency corresponds to the external input voltage value. Therefore, the switching speed can be easily changed by changing the oscillation frequency of the oscillator unit as described above.

<Oscillator operation>
The operation of the oscillator unit 4 will be described with reference to the waveform diagram of FIG. As shown in FIG. 8, when the output FIG. 8E of the comparator CMP5 is at a low level, the switch circuit SW2 is turned off as shown in FIG. 8B. When the switch circuit SW2 is off, the terminal voltage of the capacitor C1 is supplied to one input of the comparator CMP5.

  When the output of the comparator CMP5 (FIG. 8E) is at a low level, the transfer gate G1 is opened and the transfer gate G2 is closed as shown in FIGS. 8C and 8D. Therefore, the charge upper limit voltage (power supply) V1 is supplied to the other input of the comparator CMP5.

  A charging current flows from the constant current sources Iref1 and Iref2 and the current mirror circuit to the capacitor C1. As a result, the terminal voltage of the capacitor C1 gradually increases as shown in FIG.

  Note that the charging current for the capacitor C1 changes as described in the operation of the frequency switching unit.

  In the comparator CMP5, the terminal voltage of the capacitor C1 is compared with the charging upper limit voltage (power supply) V1, and when the terminal voltage of the capacitor C1 exceeds the charging upper limit voltage V3, as shown in FIG. The output of becomes high level.

  When the output of the comparator CMP5 (FIG. 8E) becomes high level, the switch circuit SW2 is turned on as shown in FIG. 8B. Further, as shown in FIGS. 6C and 6D, the transfer gate G2 is opened and the transfer gate G1 is closed. Therefore, the charging lower limit voltage V4 is supplied to the other input of the comparator CMP5.

  When the switch circuit SW2 is turned on, the charge of the capacitor C1 is discharged through the switch circuit SW2, and the terminal voltage of the capacitor C1 drops as shown in FIG. 8A. The comparator CMP5 compares the terminal voltage of the capacitor C1 with the charging lower limit voltage V4. When the terminal voltage of the capacitor C1 falls below the charging lower limit voltage V4, as shown in FIG. Become low level.

  When the output of the comparator CMP5 (FIG. 8E) becomes low level, the switch circuit SW2 is turned off as shown in FIG. 8B, and the terminal voltage of the capacitor C1 is as shown in FIG. 8A. , Gradually rising. Also, as shown in FIGS. 8C and 8D, the transfer gate G1 is opened, the transfer gate G2 is closed, and the comparator CMP5 compares the terminal voltage of the capacitor C1 with the charge upper limit voltage V3. The

  Thereafter, the same operation is repeated. Thereby, an oscillation output as shown in FIG. 8E can be obtained.

  In such an oscillator unit 4, the charging time of the capacitor C1 shown in FIG. 8A varies depending on the charging current of the capacitor C1. Thereby, the oscillation frequency can be changed.

  In this example, in the low speed region, only the transistor Q2 is turned “ON”, and the current I2 flows as I4 to the capacitor C1 of the oscillator unit 4. In this case, since the charging current for the capacitor C1 is only from the constant current source Iref1, the charging time for the capacitor C1 is lengthened and the oscillation frequency is lowered.

  In the case of the high speed region, only the transistor Q3 is turned “ON”, and the current I3 flows as I4 to the capacitor C of the oscillator unit 4. In this case, the charging current for the capacitor C1 is only from the current source Iref2, but since the current source Iref2 has a larger current capacity than the other current sources, the charging time of the capacitor C1 is shortened, and the oscillation frequency is reduced. Go up.

  Further, in the middle speed range, only the transistor Q1 is “ON”. At this time, since the comparator CMP2 functions as a buffer, the output corresponding to the external input voltage value is supplied to the current mirror circuit constituted by the transistors Q4 and Q5 as shown in FIG. The corresponding current value is supplied to the capacitor C of the oscillator unit 4 with I1 as I4. As a result, the charging time of the capacitor C1 varies according to the external input voltage value, whereby the oscillation frequency varies linearly according to the external input voltage value.

  Therefore, according to the present embodiment, the frequency switching unit can change the oscillation frequency to three or more stages according to the voltage value from the external input, and the oscillation frequency is set to the external input voltage value in the medium speed range. Therefore, the switching speed can be easily changed by changing the oscillation frequency of the oscillator unit.

  Note that the present invention is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the spirit of the present invention. For example, according to the present embodiment, the example in which the oscillation frequency changes linearly with respect to the external input voltage value in the medium speed range has been described. However, the present invention is not limited to this, and may be changed stepwise. .

1: drive signal generation unit,
2: Motor drive unit,
3: Current detection unit,
4: Oscillator part,
5: RS flip-flop 6: Frequency switching unit,
7: External input terminal,
M1-M4: MOS-FET,
L1: Motor winding

Claims (5)

An oscillator that oscillates the timing signal;
A drive signal generation unit that generates a drive signal based on a timing signal from the oscillator unit;
A motor drive unit having a motor drive unit that drives a motor by a drive signal from the drive signal generation unit
According to the external input voltage value, the oscillation frequency of the oscillator unit is variable in three or more stages, and a frequency switching unit is provided that varies the oscillation frequency in the medium speed region corresponding to the external input voltage value. A motor drive device.   The motor driving apparatus according to claim 1, wherein the motor is driven with a constant current.   The motor driving apparatus according to claim 1, wherein the motor is a stepping motor. The frequency switching unit includes two or more fixed current supply sources and a variable current supply source that varies a current value according to the external input voltage value,
The oscillation frequency of the oscillator unit is set by switching to the variable current supply source when the external input voltage value is a voltage value corresponding to the medium speed range. 4. The motor driving device according to any one of 3. The motor driving device according to claim 4, wherein a current value of the variable current supply source changes linearly according to the external input voltage value.

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