JP2011041356A - Motor drive - Google Patents

Abstract

A motor drive device capable of effectively avoiding inability to drive and device down is provided at low cost.
A motor driving circuit for supplying a current to a motor according to a duty ratio of an input rectangular wave, a current for detecting the current supplied to the motor by the motor driving circuit and outputting the current as a real current signal The detection circuit Rs, 5, U3, the integration circuit U1 that outputs the first deviation signal S3 based on the input command value signal S1 and the actual current signal S2, and the second deviation signal S4 that is input into a predetermined triangular wave S5 The rectangular wave generation circuit U2 that generates a rectangular wave S6 having a duty ratio corresponding to the magnitude relationship and outputs the rectangular wave S6 to the motor drive circuit 3, and the first deviation signal S3 from the integration circuit U1 are set in advance. And a limit circuit 6 that outputs the second deviation signal S4 to the rectangular wave generation circuit U2 while limiting so as not to exceed the threshold value.
[Selection] Figure 1

Description

  The present invention relates to a motor driving device that drives a motor.

  In a stage apparatus or the like that moves an object, a moving magnet type linear motor is used in which a plurality of coils and a mover (magnet) are arranged close to each other and the mover is moved by an excitation magnetic field of the coil. As a motor drive device for driving such a linear motor, for example, the one described in Patent Document 1 below is known.

  This motor drive device is a constant current amplifier of PWM drive, the output stage is a full bridge circuit, and the output current is controlled by the on / off duty of the switching element. The on / off duty of the switching element is the difference (deviation signal) between the actual current signal (feedback signal) fed back based on the voltage across the current detection resistor for detecting the current supplied to the load (coil) and the command value signal. ) Is determined by the duty of the rectangular wave obtained by comparing with the triangular wave.

  In such a motor drive device, a bootstrap circuit having a bootstrap capacitor may be used to supply power to the high-side driver of the full bridge circuit, thereby reducing the size and power consumption of the power supply. Yes.

  By the way, in a stage apparatus that reciprocates at high speed, when an electric current is instantaneously applied to the load, the time when the amplitude of the triangular wave becomes smaller than the maximum value of the deviation signal described above and the PWM duty becomes 100%. May occur. In this case, the drive power supply voltage is applied to the load at the maximum. Such a method of use is advantageous for improving the slew rate because the PWM duty is close to 100%.

JP 2006-271046 A

  However, if the state where the duty of PWM is 100% continues, the voltage across the bootstrap capacitor of the bootstrap circuit described above may drop, and the drive may become impossible, and the protection circuit of the gate driver is activated to operate the device. There is a problem that the whole may stop.

  Although it is possible to avoid such a problem by using a high voltage power supply that does not have a PWM duty of 100%, an expensive high voltage power supply is used only for that purpose, and elements used in the circuit However, it is also limited and must be expensive accordingly, leading to an increase in cost and is not appropriate.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a motor driving device capable of effectively avoiding inability to drive and device down at low cost.

  The motor driving device according to the present invention is a PWM type motor driving device for driving a motor, wherein the motor driving circuit supplies current to the motor in accordance with a duty ratio of an input rectangular wave, and the motor driving circuit A current detection circuit that detects the current supplied to the motor and outputs it as an actual current signal, an integration circuit that outputs a first deviation signal based on the input command value signal and the actual current signal, and A rectangular wave generating circuit that compares the second deviation signal with a predetermined triangular wave, generates a rectangular wave having a duty ratio corresponding to the magnitude relationship, and outputs the rectangular wave to the motor drive circuit; A limit circuit that limits the first deviation signal so as not to exceed a preset threshold and outputs the second deviation signal to the rectangular wave generation circuit is provided.

  According to the present invention, since the limit circuit is provided, by setting the threshold value of the limit circuit to a value smaller than the amplitude of the triangular wave of the rectangular wave generation circuit, the PWM duty is driven in a state close to 100%. However, it is possible to effectively avoid driving failure and device down, and it is not necessary to use a high-voltage power supply, so that the motor driving device can be provided at low cost.

It is a circuit diagram which shows the structure of the motor drive device of embodiment of this invention. It is a circuit diagram which shows the structure of the limit circuit of FIG.

  Hereinafter, a motor drive device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  This motor driving device is a PWM-driven constant current amplifier that drives a linear motor used in a stage device or the like that moves by placing an object. In the present embodiment, a linear motor as a driving target is a moving magnet type linear motor in which a plurality of coils and a mover (magnet) are arranged close to each other and the mover is moved by an exciting magnetic field of the coil. The motor drive device of this embodiment is particularly suitable for use in a stage device that reciprocates at high speed. In order to supply three-phase (U-phase, V-phase, and W-phase) exciting currents to the coil group of the linear motor, three motor driving devices as shown in FIG. 1 are provided. One of them will be described.

  As shown in FIG. 1, the motor drive device 1 includes a motor drive circuit (full bridge circuit 3 and smoothing circuit 4) that supplies current to the motor (load) 2 in accordance with the duty ratio of the input rectangular wave S6. , A current detection circuit (current detection resistor Rs, optical isolation amplifier 5, differential amplifier U3) that detects the current supplied to the motor by the motor drive circuit and outputs it as an actual current signal S2, and an input command value signal The integration circuit (operational amplifier U1) that outputs the first deviation signal S3 based on S1 and the actual current signal S2 and the input second deviation signal S4 are compared with a predetermined triangular wave S5, and the duty corresponding to the magnitude relationship is compared. When the rectangular wave generation circuit (comparator U2) that generates the ratio square wave S6 and outputs it to the motor drive circuit and the first deviation signal S3 from the integration circuit exceed a preset threshold value By limiting the portion exceeding the threshold value below the threshold value, it is configured to include a schematic of the limiter circuit 6 for outputting as said second difference signal with respect to the rectangular wave generating circuit.

  A command value signal S1 from a control device (not shown) provided in the stage device, and an actual current signal (feedback signal) S2 fed back from a current detection circuit (current detection resistor Rs, optical isolation amplifier 5, differential amplifier U3). Is input to the operational amplifier U1 constituting the integrating circuit, and a signal proportional to the difference between the command value signal S1 and the actual current signal S2 is supplied to the limit circuit 6 as the first deviation signal S3.

  Details of the limit circuit 6 are shown in FIG. When the first deviation signal S3 from the operational amplifier U1 exceeds a preset threshold (upper limit threshold, lower limit threshold) (when the upper limit threshold is lower than or lower than the lower limit threshold), the limit circuit 6 This is a circuit that outputs a second deviation signal S4 to the comparator U2 while limiting the range. The threshold set in the limit circuit 6 is set to a value smaller than the amplitude of the triangular wave S5 input to the comparator U2. As an example, this threshold value can be about A−0.2V ± 0.1V, where A is the amplitude of the triangular wave.

  As shown in FIG. 2, the output terminal of the operational amplifier U1 in FIG. 1 is connected to the non-inverting input terminal (+) of the operational amplifier U4. The comparator of FIG. 1 is connected to the output terminal of the operational amplifier U4 via resistors R1 and R2. The non-inverting input terminal (+) of U2 is connected. The limit circuit 6 includes an upper limit circuit having a variable resistor R3, an operational amplifier U5, a capacitor C1, and a diode D1, and a lower limit circuit having a variable resistor R4, an operational amplifier U6, a capacitor C2, and a diode D2. The upper limit threshold can be changed by adjusting the variable resistor R3, and the lower limit threshold can be changed by adjusting the variable resistor R4.

  Returning to FIG. 1, the comparator U2 compares the second deviation signal S4 from the limit circuit 6 with the triangular wave S5 to generate a rectangular wave S6 having a duty ratio corresponding to the magnitude relationship, and this rectangular wave S6 is a full bridge. It is supplied to the circuit 3.

  The comparator U2 receives a triangular wave S5 set to a predetermined amplitude, and the comparator U2 compares the peak value of the triangular wave S5 with the magnitude of the second deviation signal S4 from the limit circuit 6 to obtain a second value. A rectangular wave S6 is output as a pulse that is H level when the deviation signal S4 is larger, and is L level when the second deviation signal S4 is smaller.

  This rectangular wave S6 is supplied to the full bridge circuit 3. The full bridge circuit 3 includes a plurality of gate driver circuits, MOS-FETs, and the like, and also includes a bootstrap circuit having a bootstrap capacitor to obtain a gate driving voltage for the high-side MOS-FET. In the full bridge circuit 3, the gate driver circuit is driven based on the input rectangular wave S6. When the rectangular wave S6 is at the H level, a positive current is generated. When the rectangular wave S6 is at the L level, a negative current is output. This is supplied to the load 2 via the smoothing circuit 4. The smoothing circuit 4 includes an LC low-pass filter and a capacitor, and smoothes the pulse current supplied to the load 2.

  When the second deviation signal input to the comparator U2 is 0 (ground potential), the output of the comparator U2 is the same as the H level time and the L level time, that is, the duty ratio is 50%. Therefore, no current is supplied to the load 2. When the second deviation signal S4 becomes positive, the output of the comparator U2 is longer in the time when it is at the H level than when it is at the L level (the duty ratio is greater than 50%). Current flows, and the current value is proportional to the magnitude of the second deviation signal S4. When the second deviation signal S4 becomes negative, the output of the comparator U2 is shorter at the H level than at the L level (because the duty ratio is smaller than 50%). Directional current flows, and the current value is proportional to the magnitude of the second deviation signal S4.

  The current supplied from the full bridge circuit 3 to the load 2 via the smoothing filter 4 is detected from the voltage across the current detection resistor Rs and is actually transmitted via the optical isolation amplifier 5 and the differential amplifier (operational amplifier U3). The current signal S2 is fed back to the operational amplifier U1 constituting the integrating circuit.

  According to the present embodiment, the limit circuit 6 is provided between the operational amplifier U1 constituting the integrating circuit and the comparator U2 to be compared with the triangular wave, and the threshold value of the limit circuit 6 is a value slightly smaller than the amplitude of the triangular wave (for example, , The amplitude is set to −0.2 V ± 0.1 V), so that the PWM duty ratio is prevented from reaching 100%. This prevents the voltage across the bootstrap capacitor from dropping and the voltage from becoming the UV trip voltage of the gate drive circuit even if the command to output the maximum power continues, stopping the gate switching. The protection circuit is prevented from operating and the apparatus from being stopped. Moreover, in order to prevent the duty ratio of PWM from reaching 100%, it is not necessary to use an expensive high-voltage power supply, the number of elements used in the circuit is limited and an inexpensive one can be used, and the cost is also suppressed. Can do.

  Since the limit circuit 6 can accurately set the threshold value, the limit circuit 6 can be used in a state where the duty ratio is close to 100% without reaching 100%, and the slew rate of 100% duty can be obtained. . Further, even when the frequency characteristic is changed by changing (decreasing) the amplitude of the triangular wave, it is possible to flexibly cope with the change by adjusting the threshold value of the limit circuit 6.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Motor drive device, 2 ... Load (motor), 3 ... Full bridge circuit, 4 ... Smoothing circuit, 5 ... Optical insulation amplifier, 6 ... Limit circuit, U1 ... Operational amplifier (integration circuit), U2 ... Comparator, Rs ... Current detection resistor, R3, R4 ... variable resistor, S1 ... command value signal, S2 ... actual current signal (feedback signal), S3 ... first deviation signal, S4 ... second deviation signal, S5 ... triangular wave, S6 ... rectangular wave.

Claims (3)

A motor driving device for driving a motor,
A motor drive circuit for supplying a current to the motor in accordance with a duty ratio of an input rectangular wave;
A current detection circuit for detecting a current supplied to the motor by the motor drive circuit and outputting it as an actual current signal;
An integration circuit for outputting a first deviation signal based on the input command value signal and the actual current signal;
A rectangular wave generating circuit that compares the input second deviation signal with a predetermined triangular wave, generates a rectangular wave having a duty ratio corresponding to the magnitude relationship thereof, and outputs the rectangular wave to the motor drive circuit;
A limit circuit that limits the first deviation signal from the integration circuit so as not to exceed a preset threshold value and outputs the first deviation signal to the rectangular wave generation circuit as the second deviation signal. A motor drive device.   The motor driving apparatus according to claim 1, wherein the threshold is set to a value smaller than the amplitude of the triangular wave.   The motor driving apparatus according to claim 1, further comprising a threshold value changing circuit that changes the threshold value.

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