JP4054915B2 - Stepping motor control circuit, electronic camera, and stepping motor control method - Google Patents

Description

  The present invention relates to a control circuit for a stepping motor that drives various driving objects.

As a conventional stepping motor control circuit, for example, the one described in Patent Document 1 is known. The stepping motor control circuit controls a stepping motor that drives the zoom lens of the electronic camera, and includes a system controller and a zoom lens driving circuit. When the zoom switch is turned on, the system controller operates based on the program to enter the zoom mode, and the zoom lens driving circuit is controlled to start pulse driving of the stepping motor. Subsequently, the output drive pulse value P is added or subtracted and stored, and zoom position data corresponding to the stored pulse value P is calculated. Further, pulse driving of the stepping motor is controlled based on the calculated zoom position data and zoom position data stored in advance in the system controller. Further, the drive pulse value P is compared with the pulse value corresponding to the original zoom position data stored in advance in the system controller. If they do not match, the drive pulse value P is stored in advance in the system controller. The zoom position data is corrected (Patent Document 1 FIG. 7).
JP 2000-206394 A

  As described above, in the conventional stepping motor control circuit, the system controller is not only involved in the start of driving of the stepping motor, but also adds or subtracts the driving pulse value P output thereafter, and the zoom position corresponding to the driving pulse value P. It is involved in the control of the stepping motor from the start of driving to the end of driving, such as calculating data. For this reason, the processing load of the CPU included in the system controller is large, and other necessary control is delayed or restricted in control to be realized.

  In the conventional stepping motor control circuit, when the drive pulse value P is compared with the pulse value corresponding to the original zoom position data stored in advance in the system controller, the two do not match. If it is, the system controller executes processing for correcting the zoom position data. However, there is a time lag until the zoom position data is corrected by this processing, and the stepping motor is operating during this time. For this reason, the stepping motor may not stop at a predetermined time, and the zoom lens may stop beyond a predetermined position. Then, when the zoom lens is next driven in the reverse direction, the lens is excessively moved, so that a so-called lens biting that becomes difficult to drive again occurs, and smooth re-driving becomes difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a stepping motor control circuit capable of reducing the burden on the CPU. It is another object of the present invention to provide a stepping motor control circuit capable of preventing excessive movement of a driven object driven by a stepping motor.

  In order to solve the above problem, a stepping motor control circuit according to the first aspect of the present invention divides a driving process of a stepping motor into a plurality of driving states, and stores excitation pulse switching widths set for each of the divided driving states. Switching width storage means for switching, switching frequency storage means for storing the switching frequency of excitation pulses set for each of the divided drive states, pattern data storage means for storing a plurality of excitation pulse pattern data, and drive start instruction In response to the selection means, the selection means for sequentially selecting the pattern data stored in the pattern data storage means according to the switching width stored in the switching width storage means and the switching count stored in the switching count storage means And an excitation pulse is output to the stepping motor according to the pattern data selected by the selection means. And an output means.

  Therefore, the switching width storage means stores the excitation pulse switching width set for each drive state, the switching width storage means stores the number of excitation pulse switching times, and the pattern data storage means stores a plurality of excitation pulse pattern data. Then, if a drive start instruction is issued, the stepping motor operates and stops in the drive process divided into drive states. Therefore, the CPU does not need to be involved in the control of the stepping motor after driving, and thus the processing load on the CPU is reduced.

  According to a second aspect of the invention, in response to the drive start instruction, switching is performed according to the switching width stored in the switching width storage means and the switching count stored in the switching count storage means. The switching means further operates, and the selection means sequentially selects the pattern data stored in the pattern data storage means in synchronization with the switching operation of the switching means.

  According to a third aspect of the present invention, the switching means includes a counter that performs a counting operation based on a clock signal having a predetermined period, and performs a switching operation based on the count value of the counter.

  In the invention of claim 4, the pattern data storage means stores each pattern data corresponding to different addresses, and the switching means changes the address value in accordance with the switching operation. The selection means sequentially selects pattern data corresponding to the address value.

  Further, the stepping motor control circuit according to the invention of claim 5 is a virtual value storage means for storing the maximum value and the minimum value when the driving range of the drive object driven by the stepping motor is given by a virtual numerical value. And a measuring means for measuring the virtual position of the driving object based on the control content for outputting the excitation pulse to the stepping motor, the virtual position of the driving object measured by the measuring means, and the virtual value storage means A comparison means for comparing the maximum value and the minimum value stored in the output, and an output stop means for stopping the output of the excitation pulse according to the comparison result of the comparison means. Therefore, the stepping motor can be stopped before the driving target driven by the stepping motor exceeds the maximum and minimum values when the driving range is given by a virtual numerical value, and the driving target is excessively moved. Is prevented in advance.

  In the invention according to claim 6, the driving object is a lens provided in a camera. Therefore, it is possible to prevent so-called biting of the lens.

  In the electronic camera according to the seventh aspect of the present invention, a lens system, a driving unit having a stepping motor that drives the lens system, and an imaging unit that captures an image formed by the lens system, The stepping motor driving process is divided into a plurality of driving states, and the switching width storage means for storing the switching width of the excitation pulse set for each of the divided driving states, and the divided Switching number storage means for storing the excitation pulse switching number set for each drive state, pattern data storage means for storing a plurality of excitation pulse pattern data, and the switching width storage means in response to a drive start instruction Is stored in the pattern data storage means according to the switching width stored in the memory and the number of switching times stored in the switching number storage means. Selecting means for sequentially selecting the turn data, and an output means for outputting an excitation pulse to the stepping motor in accordance with the pattern data selected by the selection means.

  Therefore, the switching width storage means stores the excitation pulse switching width set for each drive state, the switching width storage means stores the number of excitation pulse switching times, and the pattern data storage means stores a plurality of excitation pulse pattern data. Then, if a drive start instruction is issued, the stepping motor operates and stops in the drive process divided into drive states. Therefore, the CPU in the electronic camera does not need to be involved in the control of the stepping motor after driving, and thus the processing load on the CPU is reduced.

  In the stepping motor control method according to the eighth aspect of the invention, the driving process of the stepping motor is divided into a plurality of driving states, and the excitation pulse switching width set for each of the divided driving states is stored. A switching width storing step, a switching number storing step for storing the number of switching of excitation pulses set for each of the divided driving states, and a switching width stored in the switching width storing step in response to a drive start instruction And a selection step of sequentially selecting pattern data stored in the pattern data storage means for storing a plurality of pattern data of the excitation pulse according to the switching count stored in the switching count storage step, and selecting in this selection step And outputting an excitation pulse to the stepping motor according to the pattern data. Therefore, the same effects as those of the first aspect of the invention can be achieved by executing the operations shown in the respective steps.

  According to the inventions according to claims 1 to 4, 7 and 8, the switching width storage means stores the excitation pulse switching width set for each of the divided drive states, and the switching width storage means switches the excitation pulse. By storing the number of times and storing a plurality of excitation pulse pattern data in the pattern data storage means and then instructing to start driving, the stepping motor can be operated and stopped in the driving process divided into driving states. Therefore, it is not necessary for the CPU to be involved in the control of the stepping motor after driving, and thus the processing load on the CPU can be reduced.

  According to the fifth aspect of the present invention, the stepping motor is stopped until the driving target driven by the stepping motor exceeds the maximum value and the minimum value when the driving range is given by a virtual numerical value. It is possible to prevent an excessive movement of the drive target. As a result, it is possible to prevent the occurrence of a phenomenon that makes it difficult to drive the drive target again.

  The invention according to claim 6 is advantageous in that so-called lens biting can be prevented in advance.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a digital camera to which an embodiment of the present invention is applied. The digital camera 1 includes a CPU 2, and an input device 3, a display control unit 4, an imaging control unit 5, a lens drive control unit 6, a RAM 12, a flash memory 8, a ROM 9, and an external memory 10 are connected to the CPU 2.

  The CPU 2 controls each unit based on a program stored in the ROM 9. The input device 3 includes various operation keys necessary for a digital camera such as a shutter key, and sends an operation signal corresponding to the key operation to the CPU 2. The display control unit 4 controls the operation of the display device 11 including an LCD or the like under the control of the CPU 2. The imaging control unit 5 performs a process of generating image data by converting an imaging signal output from an imaging device 55 such as a CCD into a digital signal.

  The lens drive control unit 6 includes a motor control unit 13 described later, and the motor control unit 13 outputs an excitation pulse. The lens driving unit 7 includes a stepping motor 14 that drives the lens in the lens optical axis direction. When an excitation pulse is input to the stepping motor 14 from the motor control unit 13, the stepping motor 14 operates and the lens is driven in the optical axis direction.

  The RAM 12 temporarily stores programs and various data stored in the ROM 9 and is used as a work area for the CPU 2. The flash memory 8 is a memory for storing image data obtained by imaging when the external memory 10 is not attached. The ROM 9 stores various data necessary for the program and control. The external memory 10 is detachable and stores the image data taken in with the operation of the shutter key.

  FIG. 2 is a block diagram showing details of the motor control unit 13. In the figure, a pulse width setting register 15 is a register in which the CPU 2 sets an excitation pulse width (switching width of first to eighth states) of a driving state divided into a plurality of parts for driving the stepping motor 14. The selector 16 sequentially selects the excitation pulse widths (switching widths) of the first to eighth states set in the pulse width setting register 15, and the latch 17 selects the excitation pulses output by the selector 16. This is a storage element that temporarily stores the width. The pulse width counter 18 is a counter that measures the excitation pulse width with a clock having a constant frequency, and the coincidence circuit 19 takes the coincidence of the value stored in the latch 17 and the value of the excitation pulse width measured by the pulse width counter 18. Circuit.

  The pattern setting register 20 is a register in which the CPU 2 sets the excitation pulse pattern data 1 to 8. The pattern data address counter 21 is the excitation pulse pattern data (pattern data 1 to 8) at each timing matched by the matching circuit 19. 8) is a counter that generates an address for selecting. The selector 22 selects any pattern data from the pattern setting register 20 based on the address generated by the pattern data address counter 21, and the latch 23 receives the excitation pulse pattern data selected by the selector 22. It is a storage element that stores temporarily.

  The pulse switching number register 24 is a register in which the CPU 2 sets the number of excitation pulse switching times in each of the drive states (first to eighth states). The selector 25 sequentially selects the number of switching times of the first to eighth states set in the pulse switching number register 24, and the latch 26 temporarily selects the number of excitation pulse switching times selected and output by the selector 25. It is a memory element that memorizes. The excitation pulse switching number counter 27 is a counter that is measured every time the excitation pulse pattern data is switched. The coincidence circuit 28 includes the excitation pulse switching number stored in the latch 26 and the switching number measured by the excitation pulse switching number counter 27. It is a circuit that takes a match. The drive state counter 29 is a counter that counts the drive state at each timing coincided by the coincidence circuit 28. The lens virtual position counter 30 is a counter that counts the virtual position of the lens at each timing coincided by the coincidence circuit 19.

  The maximum value register 31 is a register in which the CPU 2 sets the maximum value (lens virtual MAX position) when the lens driving range is given by a virtual numerical value, and the minimum value register 32 is a virtual value for the lens driving range. This is a register in which the CPU 2 sets the minimum value (lens virtual MIN position) when given numerically. The comparator 33 compares the lens virtual MAX position set in the maximum value register 31, the lens virtual MIN position set in the minimum value register 32, and the value counted by the lens virtual position counter 30. It is. The drive start register 34 is a register in which the CPU 2 sets the drive start of the stepping motor 14, and the drive end signal generation circuit 35 is a circuit that generates a drive end signal of the stepping motor 14 according to the motor drive end condition. is there. The drive end signal generation circuit 35 is configured to output a drive range out-of-drive interrupt signal SO and a drive end interrupt signal SE to the CPU 2.

  In the present embodiment having the above configuration, for example, when the lens is advanced to a predetermined position and stopped when the power is turned on, or when the lens is moved back to a predetermined position and stopped when the power is turned off, as shown in FIG. Then, the stepping motor 14 is stopped by acceleration driving → constant speed driving → deceleration driving. At this time, as illustrated in the figure, the CPU 2 divides the acceleration drive into the first to third states, sets the constant speed drive as the fourth state, and divides the deceleration drive into the fifth to seventh states. Further, as illustrated in FIG. 4, the CPU 2 stores the switching widths “6”, “4”, “3”, “2”, “3”, “4”, “6”, and “6” in the first to eighth states in the pulse width setting register 15. 1 ”and the number of switching times“ 2 ”,“ 3 ”,“ 4 ”,“ 9 ”,“ 4 ”,“ 3 ”,“ 2 ”, and“ 0 ”of the first to eighth states are set in the pulse switching number register 24. .

  Thereafter, the CPU 2 sets the drive start register 34 to start driving the stepping motor 14. Then, as shown in the timing chart of FIG. 5, first, the switching width data “6” of the current state selected by the selector 16 is latched in the latch 17, and the switching of the current state selected by the selector 25 is latched in the latch 26. The count data “2” is latched. The pulse width counter 18 measures the excitation pulse width using a clock with a fixed period. At this time, since the switching width of the first state in this example is “6”, the pulse width counter 18 in the first state clears the value every time the count value becomes “6”. The excitation pulse switching number counter 27 becomes an initial value “1” when the drive start is set in the drive start register 34, and then counts up every time the count value of the pulse width counter 18 is cleared. The pattern data address counter 21 counts up when the initial value is “0” and the coincidence circuit 19 matches, that is, when the value of the pulse width counter 18 becomes “6” in the first state.

  On the other hand, at the start of driving, the CPU 2 sets the excitation pulse pattern data 1 to 8 in the pattern setting register 20, and these pattern data 1 to 8 are stored in the pattern setting register 20 corresponding to the addresses 0 to 7, respectively. Yes. Therefore, when the count value of the pattern data address counter 21 is “0”, the selector 22 selects the pattern data 1 from the pattern setting register 20 based on the address “0” generated by the pattern data address counter 21. To do. The excitation pulse pattern data 1 selected by the selector 22 is latched by the latch 23, and the excitation output pulse P of the pattern data 1 is output. When the count value of the pattern data address counter 21 becomes “1”, the selector 22 selects the pattern data 2 from the pattern setting register 20.

  That is, in the first state in which the switching width is “6” and the switching count is “2”, when the value of the pulse width counter 18 becomes “6”, the excitation pulse switching count counter 27 changes from “1” to “2”. Then, the pattern data address counter 21 changes from “0” to “1”, and the excitation output pulse P changes from “pattern 1” to “pattern 2”.

  In the second state in which the switching width is “4” and the number of times of switching is “3”, when the value of the pulse width counter becomes “4”, the excitation pulse switching number counter 27 is changed from “1” → “2” → “ 3 ”, the pattern data address counter 21 changes from“ 2 ”→“ 3 ”→“ 4 ”, and the excitation output pulse P changes from“ pattern 3 ”→“ pattern 4 ”→“ pattern 5 ”, respectively. Change three times. Further, in the third state in which the switching width is “3” and the number of times of switching is “4”, when the value of the pulse width counter becomes “3”, the excitation pulse switching number counter 27 is changed from “1” → “2” → “ 3 ”→“ 4 ”, the pattern data address counter 21 changes from“ 5 ”→“ 8 ”→“ 7 ”→“ 0 ”, and the excitation output pulse P changes from“ pattern 6 ”to“ pattern 7 ”. -> "Pattern 8"-> "Pattern 1" each change four times.

  Then, the fourth state corresponding to the next constant speed driving is the switching number “9” with the switching width “2” as shown in FIG. Therefore, as shown in FIG. 5B, when the value of the pulse width counter 18 becomes “2”, the excitation pulse switching number counter 27 becomes “1” → “2” → “3”. Then, the pattern data address counter 21 changes from “1” → “2” → “3”... “1” following the third state, and the excitation output pulse P follows the third state as “pattern”. “2” → “Pattern 3” → “Pattern 4”... “Pattern 2” each change nine times.

  Subsequently, among the fifth to seventh states corresponding to the deceleration driving, the fifth state, which is the first state, has the switching width “3” and the switching count “4”. Therefore, as shown in FIG. 7, when the value of the pulse width counter 18 becomes “3”, the excitation pulse switching number counter 27 changes from “1” → “2” → “3” → “4”, and the pattern data The address counter 21 changes from “2” → “3” → “4” → “5” following the fourth state, and the excitation output pulse P also changes from “pattern 3” → “pattern 4” following the fourth state. -> "Pattern 5"-> "Pattern 6" each change four times.

  Further, in the sixth state in which the switching width is “4” and the number of times of switching is “3”, when the value of the pulse width counter becomes “4”, the excitation pulse switching number counter 27 is changed from “1” → “2” → “ 3 ”, the pattern data address counter 21 changes from“ 6 ”→“ 7 ”→“ 0 ”, and the excitation output pulse P changes from“ pattern 7 ”→“ pattern 8 ”→“ pattern 1 ”, respectively. Change three times. Further, in the seventh state where the switching width is “3” and the switching count is “4”, when the value of the pulse width counter 18 becomes “3”, the excitation pulse switching count counter 27 is changed from “1” → “2” → “ 3 ”→“ 4 ”, the pattern data address counter 21 also changes from“ 1 ”→“ 2 ”→“ 3 ”→“ 4 ”, and the excitation output pulse P changes from“ pattern 2 ”to“ pattern 3 ”. -> "Pattern 4"-> "Pattern 5" each change four times.

  The eighth state, which is the final state following the seventh state, has a switching width “1” and the number of switching times “0”. Therefore, even if the value of the pulse width counter 18 becomes “1”, the excitation pulse switching counter 27 and the pattern data address counter 21 do not change, the excitation output pulse P stops, and the stepping motor 14 also stops. Further, the drive end signal generation circuit 35 generates a drive end interrupt signal and outputs it to the CPU 2, and the CPU 2 thereby stops the motor control unit 13.

  Therefore, as described above, the CPU 2 sets the switching widths of the first to eighth states in the pulse width setting register 15 and starts the first to eighth states in the pulse switching number register 24 at the start of driving of the stepping motor 14. If the number of times of switching is set, the pattern data 1 to 8 of the excitation pulse are set in the pattern setting register 20, and the driving start of the stepping motor 14 is set in the driving start register 34, the stepping motor 14 is accelerated, constant speed, decelerated. Driven to stop. Therefore, when the driving width is set, the switching width and the number of switching times of the first to eighth states are set, the excitation pulse pattern data 1 to 8 are set, and the driving start is set. There is no need to do so, and the processing load on the CPU 2 is reduced.

  On the other hand, when the CPU 2 accelerates, drives at a constant speed, and decelerates the lens as described above, the maximum value register 31 gives the maximum value when the lens driving range is given as a virtual value (the lens virtual MAX position). ) And a minimum value (lens virtual MIN position) when the lens driving range is given by a virtual numerical value is set in advance in the minimum value register 32. The lens virtual position counter 30 counts the virtual position of the lens and outputs it to the comparator 33 at each timing matched by the matching circuit 19. Then, the comparator 33 compares the lens virtual MAX position set in the maximum value register 31 with the lens virtual MIN position set in the minimum value register 32 and the value counted by the lens virtual position counter 30. . When the value counted by the lens virtual position counter 30 reaches the lens virtual MAX position set in the maximum value register 31 or the lens virtual MIN position set in the minimum value register 32, the comparator 33 finishes driving. A signal is output to the signal generation circuit 35. The drive end signal generation circuit 35 generates an out-of-drive-range interrupt signal and outputs it to the CPU 2, and the CPU 2 stops the motor control unit 13. Accordingly, when the motor control unit 13 is stopped, the stepping motor 14 is also stopped, so that the lens driven by the stepping motor 14 is stopped within the lens virtual MAX position or the lens virtual MIN position. As a result, it is possible to prevent so-called biting of the lens, which becomes difficult to drive again due to excessive movement of the lens.

It is a block diagram which shows the circuit structure of the digital camera to which one embodiment of this invention is applied. It is a block diagram which shows the detail of a motor control part. It is a figure which shows the relationship between the drive process of a stepping motor, and the drive state divided | segmented. It is a figure which shows the value set to the pulse width setting register in this Embodiment, and the value set to the pulse switching frequency register. It is a timing chart which shows the operation | movement at the time of the acceleration drive in this Embodiment. (A) is a diagram showing storage states of a pulse width setting register, a pulse switching number register, and a pattern setting register, and (B) is a timing chart showing an operation at a constant speed drive in the present embodiment. It is a timing chart which shows the operation | movement at the time of the deceleration drive in this Embodiment.

Explanation of symbols

2 CPU
5 Imaging control unit 6 Lens drive control unit 7 Lens drive unit 9 ROM
11 Display device 12 RAM
13 Motor Control Unit 14 Stepping Motor 15 Pulse Width Setting Register 16 Selector 17 Latch 18 Pulse Width Counter 19 Matching Circuit 20 Pattern Setting Register 21 Pattern Data Address Counter 22 Selector 23 Latch 24 Pulse Switching Number Register 25 Selector 26 Latch 27 Excitation Pulse Switching Number counter 28 Match circuit 29 Drive state counter 30 Lens virtual position counter 31 Maximum value register 32 Minimum value register 33 Comparator 34 Drive start register 35 Drive end signal generation circuit 55 Imaging device

Claims (8)

A switching width storage unit that divides the driving process of the stepping motor into a plurality of driving states and stores a switching width of the excitation pulse set for each of the divided driving states;
Switching frequency storage means for storing the excitation pulse switching frequency set for each of the divided drive states;
Pattern data storage means for storing a plurality of pattern data of the excitation pulse;
In response to the drive start instruction, the pattern data stored in the pattern data storage unit is sequentially selected according to the switching width stored in the switching width storage unit and the switching count stored in the switching count storage unit. Selection means to
A stepping motor control circuit comprising output means for outputting an excitation pulse to the stepping motor in accordance with the pattern data selected by the selection means. In response to the drive start instruction, further comprises switching means that performs a switching operation according to the switching width stored in the switching width storage means and the switching count stored in the switching count storage means,
2. The stepping motor control circuit according to claim 1, wherein the selection means sequentially selects the pattern data stored in the pattern data storage means in synchronization with the switching operation of the switching means.   3. The stepping motor control circuit according to claim 2, wherein the switching unit includes a counter that performs a counting operation based on a clock signal having a predetermined cycle, and performs the switching operation based on a count value of the counter.   The pattern data storage means stores each pattern data corresponding to different addresses, the switching means changes and outputs an address value in accordance with the switching operation, and the selection means corresponds to this address value. 3. The stepping motor control circuit according to claim 2, wherein the pattern data is sequentially selected. Virtual value storage means for storing a maximum value and a minimum value when a driving range of a driving target driven by a stepping motor is given by a virtual numerical value;
Measuring means for measuring the virtual position of the drive target based on the control content for outputting an excitation pulse to the stepping motor;
A comparison means for comparing the virtual position of the drive target measured by the measurement means with the maximum value and the minimum value stored in the virtual value storage means;
A stepping motor control circuit comprising output stop means for stopping output of the excitation pulse in accordance with a comparison result of the comparison means.   6. The stepping motor control circuit according to claim 5, wherein the driving target is a lens provided in a camera. An electronic camera comprising a lens system, a driving unit having a stepping motor that drives the lens system, and an imaging unit that captures an image formed by the lens system,
A switching width storage unit that divides the driving process of the stepping motor into a plurality of driving states and stores a switching width of excitation pulses set for each of the divided driving states;
Switching frequency storage means for storing the excitation pulse switching frequency set for each of the divided drive states;
Pattern data storage means for storing a plurality of pattern data of the excitation pulse;
In response to the drive start instruction, the pattern data stored in the pattern data storage unit is sequentially selected according to the switching width stored in the switching width storage unit and the switching count stored in the switching count storage unit. Selection means to
An electronic camera comprising: output means for outputting an excitation pulse to the stepping motor according to the pattern data selected by the selection means. A switching width storing step of dividing the driving process of the stepping motor into a plurality of driving states and storing the switching width of the excitation pulse set for each of the divided driving states;
A switching frequency storage step of storing the excitation pulse switching frequency set for each of the divided drive states;
In response to a drive start instruction, pattern data storage means for storing a plurality of excitation pulse pattern data in accordance with the switching width stored in the switching width storage step and the switching count stored in the switching count storage step A selection step of sequentially selecting pattern data stored in
A stepping motor control method comprising: an output step of outputting an excitation pulse to the stepping motor according to the pattern data selected in the selection step.

Images