JP2006101662A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of rush current at driving a motor, without causing increase in the number of mounting components in a motor drive. <P>SOLUTION: After starting driving of a motor 1, an output current detecting section 22 of a motor drive 2 detects the output current level of the motor 1 and the detected output current level is compared with a preset current limit level. If the output current level exceeds the current limit level, the motor drive 2 performs control for lowering the output current level and the output voltage level of the motor 1. If the output current level is lower than the current limit level, the motor drive 2 performs control for elevating the output current level and the output voltage level of the motor 1. By conducting such a control, generation of rush current can be prevented at the time of starting driving of the motor 1 without mounting a new component such as a capacitor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor drive device that drives a motor mounted on, for example, a camera.

Conventionally, in a motor drive device in various drive mechanisms mounted on a device such as a camera, for example, the current is several times the rated current value due to load fluctuations within a certain period of time immediately after voltage is applied to the motor to drive it. Inrush current may occur, which not only causes damage to the equipment, but also when the inrush current occurs, the motor drive voltage may fluctuate and the motor may not operate normally. As a technique for preventing the occurrence of inrush current, for example, as disclosed in Patent Document 1, an element such as a capacitor or a switch is added to the circuit to suppress a sudden increase in current flowing to the motor. The generation of current was prevented.
JP-A-7-147767

  However, in the method as described above, new parts must be mounted in order to prevent the occurrence of inrush current, leading to an increase in manufacturing cost and volume of the device. In addition, in this method of newly mounting components, current suppression is performed only for a single operating condition of the motor, that is, a single set value of the rotational speed of the motor, so that the operating condition of the motor changes. If the rotation speed to be set changes, the inrush current cannot be suppressed appropriately.

  Therefore, an object of the present invention is to provide a motor drive device that can appropriately prevent the occurrence of an inrush current during driving of the motor without increasing the number of mounted components.

  According to the first aspect of the present invention, the output current value of the motor is detected by detecting the output current value of the motor by the detection means, and the output voltage value of the motor is controlled by the voltage control means based on the magnitude of the detected output current value. Control is performed so that the value is less than a predetermined upper limit value.

  According to a second aspect of the present invention, in the first aspect of the present invention, at least one of the detection means and the voltage control means is provided inside the motor driver.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the output voltage value of the motor is controlled to decrease when the output current value of the motor exceeds a predetermined reference value. Control is performed so that the output voltage value of the motor increases when the output current value of the motor is equal to or less than a predetermined reference value.

  According to the first aspect of the invention, the output current value of the motor is determined in advance by controlling the output voltage value of the motor by the voltage control means based on the magnitude of the output current value of the motor detected by the detection means. Since the control is performed so as to be less than the upper limit value, the occurrence of an inrush current at the start of driving of the motor can be prevented.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, at least one of the detection means and the voltage control means is provided inside the motor driver, so that the apparatus can be downsized.

  According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, when the output current value of the motor exceeds a predetermined reference value, the output voltage value of the motor is changed. When the motor output current value is less than or equal to a predetermined reference value, control is performed to increase the motor output voltage value, so that the motor output current value can be limited, and the inrush current Can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an example of the configuration of a motor drive device according to an embodiment of the present invention.
The motor drive device according to the present embodiment is used for various drive mechanisms such as a shutter or zoom mounted on a camera, for example. As shown in FIG. 1, the motor driving device is configured to drive the motor 1 and the rotor (not shown) of the motor 1 to drive and drive the motor 1 with a driving voltage (output voltage) and a driving current (output current). The motor driver 2 to be controlled, the motor drive power supply unit 3 for obtaining power to be supplied to the motor 1 through DC-DC conversion from an external power supply input, and the motor driver 2 out of the power supplies obtained by the motor drive power supply unit 3 A motor drive voltage control power supply unit (voltage control power supply unit) 4 for obtaining a control power supply for controlling the voltage of the power supply applied to the motor 1 via the motor 1 and various control signals for driving the motor 1 to the motor driver 2 A control microcomputer 5 for outputting is provided.

  The motor driver 2 is provided between the motor drive power supply unit 3 and the motor 1, and includes an H bridge circuit 21, an output current detection unit 22, and a voltage control unit 23. The voltage control power supply unit 4 is connected to the H bridge circuit 21 via the voltage control unit 23 of the motor driver 2. The H bridge circuit 21 is connected to the motor 1 and is also connected to the motor drive power supply unit 3 via the output current detection unit 22.

  The H bridge circuit 21 has a function of controlling the rotation direction of the rotor of the motor 1 to be either forward rotation or reverse rotation after energizing the motor 1 with power supplied from the motor drive power supply unit 3. The output current detection unit 22 detects the value of current flowing in the current path from the motor drive power supply unit 3. The voltage control unit 23 controls the voltage of the control power supply supplied from the voltage control power supply unit 4 to the H bridge circuit 21. As a result, the voltage of the power source supplied to the motor driver 2 among the power sources obtained by the motor drive power source unit 3 is controlled, so that the output voltage and output current of the motor 1 are controlled.

Next, the processing operation of the motor driving apparatus described above will be described.
FIG. 2 is a flowchart illustrating an example of a processing operation performed by the motor driving device according to the embodiment of the present invention. This processing operation is a processing operation for rotating the rotor of the motor 1 so that no inrush current is generated in the motor 1 based on control by the control microcomputer 5 and the motor driver 2.

FIG. 3 is a diagram illustrating an example of a graph of time characteristics of the output current and output voltage of the motor 1 when the suppression control is performed by the motor driving device according to the embodiment of the present invention.
The suppression control is control that suppresses generation of an inrush current applied to the motor 1 when the motor 1 is operated. When the suppression control is not performed, as shown in FIG. 3, the output current value of the motor 1 rapidly increases immediately after the start of driving of the motor 1 and becomes a high current, whereas the suppression control is performed. In this case, the output current value of the motor 1 does not exceed a predetermined value.

  In order to perform such suppression control, the control microcomputer 5 first outputs a motor drive voltage control signal (Output Control) for setting a target value of the drive output voltage (output voltage) of the motor 1 to the motor driver 2. (Step S1). This motor drive voltage control signal includes information on the target value of the output voltage when a sufficient time has elapsed since the start of driving of the motor 1.

  Next, the control microcomputer 5 includes a current limit level of the motor 1, that is, a rush including information on a reference value of the output current of the motor 1 that is predetermined to prevent the occurrence of a rush current after the start of driving of the motor 1. A suppression current value control signal (Current Limit) is output to the motor driver 2 (step S2). The value of the current limit level is a value less than the output current value (upper limit value) that causes damage to various devices including the motor 1 and abnormal load fluctuations, and is set according to the operation mode of the motor 1.

  The operation mode defines the driving condition of the motor 1, and includes, for example, a first operation mode in which the rotor rotation speed is low and a second operation mode in which the rotor rotation speed is high. The control microcomputer 5 performs control to switch various operation modes as necessary.

  Further, the control microcomputer 5 outputs a motor drive control signal (Motor +, Motor−) for controlling the rotation direction of the rotor of the motor 1 to the motor driver 2 (step S3). After this motor drive control signal is input to the H bridge circuit 21 of the motor driver 2, the rotational drive of the rotor of the motor 1 is started. After starting the driving of the motor 1, the output voltage value of the motor 1 increases toward the target value set by the motor driving voltage control signal described above, and the output current value of the motor 1 also increases.

  Next, the output current detection unit 22 of the motor driver 2 detects the current value flowing in the current path from the motor drive power supply unit 3 (step S4). This current value corresponds to the output current value of the motor 1. Specifically, the output current detection unit 22 of the motor driver 2 includes a logic circuit corresponding to an internal resistor for current detection, and the motor driver 2 detects the terminal voltage of the logic circuit as described above. Get the output current value.

  When the control microcomputer 5 generates a control command for stopping the operation of the motor 1 (YES in step S5), the control microcomputer 5 drives the rotation of the rotor of the motor 1 according to the control command described above. A control signal including control information to be stopped is output to the motor driver 2 (step S6). When this control signal is input to the H bridge circuit 21 of the motor driver 2, the rotational drive of the rotor of the motor 1 is stopped.

  On the other hand, if “NO” is determined in the process of step S5, the motor driver 2 determines the value of the current limit level set in the process of step S2 and the value of the output current value detected in the process of step S4. Are compared to determine whether or not the output current value of the motor 1 exceeds the value of the current limit level (step S7).

  If “YES” is determined in the process of step S7, the voltage control unit 23 of the motor driver 2 performs control to decrease the value of the output voltage of the motor 1 (step S8). Specifically, the voltage control unit 23 of the motor driver 2 includes a logic circuit corresponding to a variable resistor for setting an output voltage, and the value of the variable resistor applied to the logic circuit is set to the switch element of the logic circuit. Raise through on-off and so on. As a result, the voltage value of the power supplied from the voltage control power supply unit 4 to the H bridge circuit 21 decreases, so that the output voltage value of the motor 1 increases. Accordingly, the output current value also decreases. After performing the process of step S8, it returns to the process of step S4 and the subsequent processes are repeated.

  On the other hand, if “NO” is determined in the process of step S7, that is, if the output current value of the motor 1 is equal to or less than the current limit level, the voltage control unit 23 of the motor driver 2 Control is performed to increase the value of the output voltage toward the target value described above (step S9). Specifically, the voltage control unit 23 of the motor driver 2 lowers the value of the variable resistor applied to the above-described logic circuit through ON / OFF of the switch element of the logic circuit. As a result, the voltage of the power source supplied from the voltage control power supply unit 4 to the H bridge circuit 21 increases, so that the output voltage value of the motor 1 increases. Accordingly, the output current value also increases. After performing step S9, the process returns to step S4.

  That is, the output current value of the motor 1 increases after the start of driving of the motor 1, and when the output current detection unit 22 detects that this value exceeds the current limit level value, the above-described step is performed. By the process of S8, the output current value falls to a value below the current limit level. When the output current detection unit 22 detects that the output current value has fallen below the current limit level, the output current value increases by the process of step S9 described above.

  As a result, the output current value of the motor 1 again exceeds the value of the current limit level described above, and the processes of steps S8 and S9 are repeated thereafter. That is, the value of the output current of the motor 1 is repeatedly changed little by little between a value exceeding the current limit level and a value less than or equal to the current limit level. Further, the output voltage value rises toward the target value while repeating small and small changes according to the change in the output current value.

  That is, if the current limit level is set so that no inrush current is generated unless the output current value significantly exceeds the value of the current limit level described above, the output current of the motor 1 as shown in the graph of FIG. The value of the value can be limited, and the occurrence of inrush current can be prevented. By preventing the occurrence of the inrush current, it is possible to prevent damage to the device due to overcurrent and stop operation of the device due to load fluctuations, so that the motor 1 can be driven normally and safely.

  As described above, according to the motor driving apparatus described in the above-described embodiment, driving of the motor 1 is started by detecting the output current value of the motor 1 and controlling the output voltage of the motor 1 based on the magnitude of the detected current value. Therefore, it is not necessary to mount a new component such as a capacitor for preventing the occurrence of the inrush current. Moreover, since the value of the current limit level can be set to a value suitable for the type of operation mode by the control microcomputer 5, appropriate inrush current suppression control can be performed according to the driving conditions of the motor 1.

  Although the motor drive device according to the embodiment described above is provided with a single motor 1, a plurality of motors 1 may be provided. In this case, the number corresponds to the number of motors 1 provided. The H bridge circuit 21 may be provided in the motor driver 2, and the H bridge circuit 21 and each motor 1 may be connected in a one-to-one relationship.

  In the above embodiment, the case where the present invention is applied to a camera drive mechanism is described. However, the present invention is not limited to this, and the present invention can be applied to a drive mechanism of other devices as long as the drive mechanism includes a motor. It is possible to apply.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The figure which shows an example of a structure of the motor drive device according to embodiment of this invention. The flowchart which shows an example of the processing operation by the motor drive device according to the embodiment of the present invention. The figure which shows the example of the graph of the time characteristic of the output current of a motor, and the output voltage at the time of performing suppression control by the motor drive device according to embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Motor driver, 3 ... Motor drive power supply part, 4 ... Motor drive voltage control power supply part, 5 ... Control microcomputer, 21 ... H bridge circuit, 22 ... Output current detection part, 23 ... Voltage control part 23

Claims (3)

Detection means for detecting the output current value of the motor;
Voltage control means for controlling the output current value of the motor to be less than a predetermined upper limit value by controlling the output voltage value of the motor based on the magnitude of the output current value detected by the detection means; A motor drive device comprising the motor drive device.   The motor driving apparatus according to claim 1, wherein at least one of the detection unit and the voltage control unit is provided inside a motor driver that drives the motor. The voltage control means includes
When the output current value detected by the detection means is less than the upper limit value and exceeds a predetermined reference value, the output voltage value of the motor is lowered, and the detected output current value is equal to or less than the reference value. If it is, the motor drive device according to claim 1 or 2, wherein control is performed to increase an output voltage value of the motor driver.

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