JP2009201225A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive which can easily change switching speed, without having to install external components. <P>SOLUTION: A driving signal generating part 1 receives an input control signal IN and an output signal of an RS flip flop 5 and generates a drive signal for MOS-FETM1 to M4. A motor drive part 2 makes current flow to motor winding L1 by MOS-FETM1 to M4 and drives a motor. A current-detecting part 3 detects current flowing in the motor drive part 2 and triggers the RS-flip flop 5 with detection output so as to drive the motor with a constant current. An oscillator part 4 oscillates a timing signal and resets the RS-flip flop 5 with a timing signal. A frequency switching part 6 switches the oscillation frequency of the oscillator part 4, by a setting from an external input terminal 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, as shown in FIG. 7, a motor driving apparatus that drives a stepping motor with a constant current includes a driving signal generation unit 101 that generates a driving signal, and a metal oxide semiconductor field effect transistor (MOS-FET) M101 to M104. 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.

  However, if 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 device shown in FIG. 7, 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 parts 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 an object of the present invention is to provide a motor drive device in which the switching speed can be easily changed without mounting external parts.

  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, FIG. 1) and a motor drive unit (for example, equivalent to the motor drive unit 2 in FIG. 1) that drives the motor by the drive signal from the drive signal generation unit. There has been proposed a motor driving device characterized in that a frequency switching unit (for example, corresponding to the frequency switching unit 6 in FIG. 1) capable of setting the oscillation frequency of the oscillator unit by an external input is provided.

  According to the present invention, the switching speed can be easily changed by changing the oscillation frequency of the oscillator unit by an external input.

  (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 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 an external input with the stepping motor.

  (4) According to the present invention, in the motor drive devices of (1) to (3), the frequency switching unit switches the supply current amount from two or more current supply sources (for example, the constant current source I1 in FIG. 5). , I2 and SW2), a motor driving device is proposed in which the oscillation frequency of the oscillator unit is set.

  According to the present invention, since the oscillation frequency of the oscillator unit is varied depending on the amount of current supplied, the oscillation frequency of the oscillator unit can be finely varied by accurately controlling the amount of current.

  According to the present invention, by changing the oscillation frequency of the oscillator unit by an external input, when the winding ripple current is large, it is possible to increase the switching speed and reduce the winding ripple current. is there. Further, when the switching loss increases, the switching speed can be lowered to reduce the switching loss. Since the oscillation frequency of the oscillator unit can be changed by an external input, there is an effect that external parts are unnecessary and the external parts can be reduced.

  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.

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. The circuit of each part constituting these motor driving devices is integrated.

  The drive signal generator 1 receives the input control signal IN and the output signal of 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 a current flowing through the motor drive unit 2 and triggers the RS flip-flop 5 by this detection output to drive the motor 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 setting from the external input terminal 7.

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

  The source of the MOS-FET M2 and the source of the MOS-FET M2 are grounded via the detection resistor Rs1. The motor winding L1 is connected between a connection point between the source of the MOS-FET M1 and the drain of the MOS-FET M2, and a connection point between the source of the MOS-FET M3 and the drain of the MOS-FET M4.

  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 turned on. 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 increases due to the 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 FET on period is changed to the flywheel period, the MOS-FET M1 is turned off, and the MOS-FET M2 is turned on.

  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 (J), 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.

  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.

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).

  In this embodiment, by switching the oscillation frequency of the oscillator unit 4 by setting from the external input terminal 7, when the winding ripple current is large, the switching speed is increased and the winding ripple current is reduced. When the switching loss increases, the switching speed can be lowered to reduce the switching loss.

  Next, the configuration of the oscillator unit 4 capable of switching the oscillation frequency by setting 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 CMP2, a switch circuit SW1, a capacitor C1, transfer gates G1 and G2, and inverters INV1 and INV2.

  A capacitor C1 and a switch circuit SW1 are connected between one input of the comparator CMP2 and the ground. Further, the current source I1 is connected to one input of the comparator CMP2, and the current source I2 is connected via the switch circuit SW2.

  The current sources I1 and I2 and the switch circuit SW2 constitute a frequency switching unit 6. The switch circuit SW2 is switched by a control signal from the external input terminal 7.

  The other input of the comparator CMP2 is connected to the charging upper limit voltage V1 via the transfer gate G1, and is connected to the charging lower limit voltage V2 via the transfer gate G2.

  The output of the comparator CMP2 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 V1, and the transfer gate G2 turns on / off the supply of the charging lower limit voltage V2.

  The operation of the oscillator unit 4 will be described with reference to the waveform diagram of FIG. 6, when the output of the comparator CMP2 (FIG. 6 (E) is at a low level, the switch circuit SW1 is turned off as shown in FIG. 6 (B), and when the switch circuit SW1 is turned off, The terminal voltage of the capacitor C1 is supplied to one input of the comparator CMP2.

  When the output of the comparator CMP2 (FIG. 6E) is at a low level, the transfer gate G1 is opened and the transfer gate G2 is closed as shown in FIGS. 6C and 6D. Therefore, the charge upper limit voltage V1 is supplied to the other input of the comparator CMP2.

  A charging current flows from the current sources I1 and I2 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 is switched by the switch circuit SW2. When the switching frequency is set low, the switch circuit SW2 is turned off. In this case, the charging current for the capacitor C1 is the current source I1. When the switching frequency is set high, the switch circuit SW2 is turned on. When the switch circuit SW2 is turned on, the charging current for the capacitor C1 is the sum of the current source I1 and the current source I2.

  The comparator CMP2 compares the terminal voltage of the capacitor C1 with the charge upper limit voltage V1. When the terminal voltage of the capacitor C1 exceeds the charge upper limit voltage V1, the output of the comparator CMP2 becomes high level as shown in FIG. 6 (E).

  When the output of the comparator CMP2 (FIG. 6E) becomes high level, the switch circuit SW1 is turned on as shown in FIG. 6B. 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 V2 is supplied to the other input of the comparator CMP2.

  When the switch circuit SW1 is turned on, the charge of the capacitor C1 is discharged through the switch circuit SW1, and the terminal voltage of the capacitor C1 drops as shown in FIG. The comparator CMP2 compares the terminal voltage of the capacitor C1 with the charge lower limit voltage V2. When the terminal voltage of the capacitor C1 falls below the charging lower limit voltage V2, the output of the comparator CMP2 becomes low level as shown in FIG. 6 (E).

  When the output of the comparator CMP2 (FIG. 6E) becomes low level, the switch circuit SW1 is turned off as shown in FIG. 6B, and the terminal voltage of the capacitor C1 is as shown in FIG. 6A. , Gradually rising. Further, as shown in FIGS. 6C and 6D, the transfer gate G1 is opened, the transfer gate G2 is closed, and the comparator CMP2 compares the terminal voltage of the capacitor C1 with the charge upper limit voltage V1. The

  Thereafter, the same operation is repeated. Thereby, an oscillation output as shown in FIG. 6E can be obtained.

  In such an oscillator unit 4, the charging time of the capacitor C1 shown in FIG. 6A varies depending on the charging current of the capacitor C1. Thereby, the oscillation frequency can be changed.

  In this example, the charging current for the capacitor C1 is switched by the switch circuit SW2. When the switching frequency is set low, the switch circuit SW2 is turned off. In this case, since the charging current for the capacitor C1 is only from the current source I1, the charging time for the capacitor C1 is lengthened and the oscillation frequency is lowered.

  When the switching frequency is set high, the switch circuit SW2 is turned on. When the switch circuit SW2 is turned on, the charging current for the capacitor C1 is the sum of the current source I1 and the current source I2. This shortens the charging time of the capacitor C1 and increases the oscillation frequency.

  As described above, in the present embodiment, by switching the oscillation frequency of the oscillator unit 4 by setting from the external input terminal 7, it is possible to easily switch between the high speed operation and the low speed operation without mounting external components. Can do.

  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.

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 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.

Explanation of symbols

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 (4)

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;
A motor driving apparatus comprising a frequency switching unit capable of setting an oscillation frequency of the oscillator unit by an external input.   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.   5. The motor drive according to claim 1, wherein the frequency switching unit switches an amount of current supplied from two or more current supply sources to set an oscillation frequency of the oscillator unit. 6. apparatus.

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