JP4200783B2 - Motor drive device and camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC motor drive circuit and a drive method.
[0002]
[Prior art]
A technique is known in which pulse energization is performed on a battery-driven motor (see, for example, Patent Document 1). Patent Document 1 discloses a camera that drives a photographing lens back and forth in the optical axis direction with a motor. The motor for driving the taking lens of the camera is controlled so that the starting torque rises by energizing for a predetermined time at the start, and starts driving the lens. This motor is controlled to decelerate by switching to pulse energization after starting, and the shock generated in the lens and the power transmission system at the time of mechanical stop is suppressed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 63-113431 [0004]
[Problems to be solved by the invention]
The driving of the motor according to Patent Document 1 is switched to pulse energization when the motor is started, so that the electric power supplied to the motor after the start is lower than that at the start, and the torque after the start is reduced. Also, since the motor is energized for a predetermined time regardless of the battery voltage at the start of the motor, the voltage supplied to the motor exceeds the motor rating when the battery voltage is too high, or the starting current is several times the motor rating There is a fear.
[0006]
[Means for Solving the Problems]
The motor driving device according to the present invention includes a voltage detection unit that detects a voltage supplied from a power source, a DC motor, and an effective voltage applied to the DC motor according to a voltage detection value by the voltage detection unit. A calculation means for calculating the drive duty so as not to exceed the rated value, a motor drive means for applying a supply voltage to the DC motor at a predetermined duty, and a time determined in advance according to the characteristics of the DC motor, When a voltage is applied to the DC motor at the first duty at the start of driving of the DC motor, a time t1 until the drive current flowing to the DC motor starts to increase and decreases, and after the time t1, the DC motor receives the first duty from the first duty. Information indicating the time t2 until the drive current flowing to the DC motor changes from increasing to decreasing again when a voltage is applied with a high second duty, respectively. Based on the storage means for storing and the stored information, the first duty is used until the time t1 elapses from the start of driving of the DC motor, and the second duty is used until the time t2 elapses after the time t1. And a control means for controlling the motor driving means so as to apply a voltage to the DC motor with the driving duty calculated by the calculating means, respectively, wherein the first duty and the second duty are lower than the driving duty.
The camera by this invention has the motor drive device as described in any one of Claims 1-6, It is characterized by the above-mentioned.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing an outline of a motor control circuit according to a first embodiment of the present invention. In FIG. 1, the motor control circuit includes diodes 4 and 4 ′, a stabilization circuit 5, a control circuit 6, a pre-driver 10, a P channel MOS-FET 11, and an N channel MOS-FET 12. The motor control circuit drives the DC motor 13 using electric power from a DC voltage source connected between the terminal 2 and the terminal 2 ′ or between the terminal 3 and the terminal 3 ′. In the example of FIG. 1, the battery 1 is connected between the terminal 2 and the terminal 2 ′. The terminals 3 and 3 ′ are used for connecting an external power source (not shown).
[0008]
The voltage of the battery 1 is applied between the stabilization circuit 5, the pre-driver 10, the source terminal of the P-channel MOS-FET 11 and the drain terminal of the N-channel MOS-FET 12 via the diode 4. Here, the P-channel MOS-FET 11 and the N-channel MOS-FET 12 are connected in series. That is, the drain terminal of the P-channel MOS-FET 11 and the source terminal of the N-channel MOS-FET 12 are connected. The stabilization circuit 5 DC / DC converts the voltage from the DC voltage source (battery 1 in this case) into a predetermined voltage required by the control circuit 6 and supplies it to the control circuit 6. Control circuit 6 includes a voltage detection circuit 7, an arithmetic circuit 8, and an output control circuit 9.
[0009]
The voltage detection circuit 7 detects the voltage value of an external power supply (not shown) connected between the terminals 3 and 3 ′ via the signal line 21 and also detects the voltage value supplied to the motor driving circuit. To detect through. In the present embodiment, the voltage applied between the P-channel MOS-FET 11 and the N-channel MOS-FET 12 corresponds to the voltage supplied to the motor 13. The detection result by the voltage detection circuit 7 is output to the arithmetic circuit 8 through the signal line 23. The arithmetic circuit 8 performs a predetermined calculation based on the voltage detection value by the voltage detection circuit 7 and outputs a motor control command to the output control circuit 9 via the signal line 24. The output control circuit 9 generates a control signal in response to a control command from the arithmetic circuit 8. The control signal includes two signals having an H level or an L level, and these two control signals are output to the pre-driver 10 via the signal line 25 and the signal line 26, respectively.
[0010]
The pre-driver 10 generates a drive signal for turning on / off the P-channel MOS-FET 11 and a drive signal for turning on / off the N-channel MOS-FET 12 in response to the two control signals from the output control circuit 9. The signal is output to the gate terminal of the P-channel MOS-FET 11 and the gate terminal of the N-channel MOS-FET 12 through the signal line 27 and the signal line 28, respectively. The motor 13 is connected between the source terminal and the drain terminal of the N-channel MOS-FET 12. The motor 13 is controlled to any one of driving (rotation), stopping, and braking (braking) in accordance with ON / OFF of the P-channel MOS-FET 11 and the N-channel MOS-FET 12.
[0011]
FIG. 2 shows the control signal (control input) level input to the pre-driver 10, the drive signal (control output) level output from the pre-driver 10, the states of the P-channel MOS-FET 11 and the N-channel MOS-FET 12, It is a figure explaining the relationship with the operation state of the motor. In FIG. 2, when both the P-channel MOS-FET 11 and the N-channel MOS-FET 12 are off, the winding of the motor 13 (not shown) is opened, so that the motor 13 is stopped. Here, the stopped state is a state in which no torque is generated in the rotor (not shown) of the motor 13.
[0012]
When the P-channel MOS-FET 11 is off and the N-channel MOS-FET 12 is on, the winding of the motor 13 (not shown) is short-circuited, so that the motor 13 is in a braking state. Here, the braking state is a state in which torque is not generated in the rotor (not shown) of the motor 13 and the brake is electromagnetically applied.
[0013]
When the P-channel MOS-FET 11 is on and the N-channel MOS-FET 12 is off, a current flows through the winding (not shown) of the motor 13 via the P-channel MOS-FET 11, so that the motor 13 is in a driving state. Here, the driving state is a state where torque is generated in the rotor (not shown) of the motor 13. The pre-driver 10 drives the motor 13 when the control input 25 is H and the control input 26 is L, and when the control input 25 and the control input 26 are both H. It is configured.
[0014]
In the motor control circuit described above, the present invention alternately switches between a driving state and a stopped state when the motor 13 is driven. In the first embodiment, the duty of the drive state and the stop state is changed according to the voltage supplied to the motor 13.
[0015]
The arithmetic circuit 8 outputs a motor control command to the output control circuit 9 as follows.
1. When the motor 13 is stopped, the stop state calculation circuit 8 outputs a motor control command so that the control signal corresponding to the signal line 25 and the control signal corresponding to the signal line 26 are set to L level.
[0016]
2. When braking the motor 13, the braking state calculation circuit 8 outputs a motor control command so that the control signal corresponding to the signal line 25 is set to L level and the control signal corresponding to the signal line 26 is set to H level.
[0017]
3. When driving the motor 13, the driving state calculation circuit 8 outputs a motor control command so that the control signal corresponding to the signal line 25 is set to H level and the control signal corresponding to the signal line 26 is set to L level. The arithmetic circuit 8 further controls the control signal corresponding to the signal line 25 so that the voltage supplied to the motor 13 does not exceed the rated voltage of the motor 13, and the ratio (duty) between the H level and the L level according to the voltage. A control command is output so as to change. The control signal corresponding to the signal line 26 is kept at the L level.
[0018]
FIG. 3 is a diagram showing a waveform example of the control signal (signal line 25) when the voltage supplied to the motor 13 exceeds the rated voltage of the motor 13. As shown in FIG. For example, when the rated voltage of the motor 13 is 6V and the detection voltage of the voltage detection circuit 7 via the signal line 22 is 9V, the arithmetic circuit 8 calculates the duty by the following equation (1) and obtains this duty. Output control commands.
[Expression 1]
(6/9) × 100 = 67% (1)
[0019]
In the control signal (signal line 25) of FIG. 3, when 67% of one cycle is set to the H level and the remaining 33% is set to the L level, the motor 13 alternately repeats the drive state and the stop state. Actually, since the rotor of the motor 13 continues to rotate even in the stopped state due to the moment of inertia, the motor 13 is controlled while controlling the voltage so that the average value (effective voltage) of the voltage supplied to the motor 13 does not exceed the rated voltage. 13 operations can be continued. The frequency at which the control signal repeats the H level and the L level is preferably several tens KHz.
[0020]
When the voltage supplied to the motor 13 is equal to or lower than the rated voltage of the motor 13, the arithmetic circuit 8 outputs a control command so as to obtain a duty of 100%. The duty 100% is a state in which the control signal (signal line 25) is always at the H level when the motor 13 is driven. The control signal corresponding to the signal line 26 is kept at the L level.
[0021]
The first embodiment described above will be summarized. The arithmetic circuit 8 performs the calculation according to the above equation (1) so that the voltage supplied to the motor 13 does not exceed the rated voltage of the motor 13. The arithmetic circuit 8 further outputs a control command to the output control circuit 9 so that the control signal corresponding to the signal line 25 is alternately switched between the H level and the L level according to the voltage exceeding the rated voltage. The control signal corresponding to the signal line 26 is kept at the L level. As a result, the motor 13 is alternately driven and stopped at a duty (67% in the above example) obtained by the above calculation, and the effective voltage supplied to the motor 13 is kept below the rated voltage of the motor 13. be able to. As a result, since the motor 13 is always used within the rating, the life of the motor 13 is not adversely affected. In addition, since the effective voltage as rated is applied during duty driving, the motor 13 can be stably operated continuously without causing a reduction in torque of the motor 13.
[0022]
In the driving state of the motor 13, instead of keeping the control signal corresponding to the signal line 26 at the L level, the signal level may be changed in the same manner as the control signal corresponding to the signal line 25.
[0023]
Although the driving state and the stopped state of the motor 13 are alternately repeated during the duty driving, the driving state and the braking state may be alternately repeated. In this case, the control signal corresponding to the signal line 25 is alternately switched between the H level (driving state) and the L level (braking state) according to the voltage exceeding the rated voltage, and also corresponds to the signal line 26. The control signal is kept at the H level.
[0024]
(Second embodiment)
In general, at the initial stage of starting (starting) the motor 13, a current estimated from a winding (not shown) resistance of the motor 13 and a voltage applied to the winding flows in the motor 13. This current gradually decreases due to the counter electromotive force generated by the rotation of the motor 13 and converges to a value determined by the load of the motor 13 and the like in a steady state. In the second embodiment, when the motor is started, the duty for repeating the drive state and the stop state is changed so as to gradually increase.
[0025]
FIG. 4 is a diagram showing the duty of the control signal (signal line 25) when the motor 13 is started. In FIG. 4, the horizontal axis represents time, and the vertical axis represents duty. The arithmetic circuit 8 sets the duty to 20% from the start start time t0 to the time t1, to 40% from the time t1 to the time t2, to 60% from the time t2 to the time t3, and after the time t3 has elapsed (steady state) ) Outputs a control command so that the duty is 67%. As in the first embodiment, the duty 67% assumes that the rated voltage of the motor 13 is 6V and the detection voltage by the voltage detection circuit 7 is 9V.
[0026]
FIG. 5 is a diagram illustrating a waveform example of a control signal (signal line 25) having a duty of 20%. When 20% of one cycle is set to the H level and the remaining 80% is set to the L level, the motor 13 alternately repeats the drive state and the stop state. FIG. 6 is a diagram illustrating a waveform example of a control signal (signal line 25) having a duty of 40%. When 40% of one cycle is set to the H level and the remaining 60% is set to the L level, the motor 13 alternately repeats the drive state and the stop state. By gradually increasing the duty, the driving torque of the motor 13 is gradually increased.
[0027]
A period in which the duty is lowered compared to the steady state (time t0 to time t3 in the above example), the number of steps for gradually changing the duty (3 in the above example), and the duty value in each step (20 in the above example) %, 40%, and 60%) are determined in advance according to the starting characteristics of the motor 13, and these values are stored in advance in a memory (not shown) in the arithmetic circuit 8.
[0028]
The output control circuit 9 changes the duty of the control signal according to the control command sent from the arithmetic circuit 8. Specifically, the timer circuit (not shown) starts timing at the start start time t0, and the duty of the control signal is changed as described above every time the timer circuit counts a predetermined time.
[0029]
FIG. 7 is a diagram showing a waveform of a current flowing through the motor 13 during the control according to FIG. In FIG. 7, the horizontal axis represents time, and the vertical axis represents the magnitude of current. When the motor 13 is started at time t0, a current starts to flow through the motor 13. Since the duty is set to 20% from time t0 to time t1, the maximum current value is kept small compared to the current waveform (FIG. 8) when the motor 13 is started at a duty of 100% after the start time t0. It is done. The duty 20% is determined so that the maximum current value does not exceed the current limit target value of the motor 13 at times t0 to t1.
[0030]
The current flowing through the motor 13 starts to decrease due to the counter electromotive force generated by the rotation of the motor 13. When the duty is set to 40% at time t1 after the current has changed from increasing to decreasing, the current flowing through the motor 13 starts increasing again. Similarly, by increasing the duty of the control signal each time the current changes from increasing to decreasing, the current waveform flowing in the motor 13 becomes a sawtooth waveform that alternately repeats rising and falling. Thereby, the motor 13 is started so that the maximum value of the current flowing through the motor 13 does not exceed the current limit target value.
[0031]
The second embodiment described above will be summarized. The arithmetic circuit 8 sets the duty to 20% from the start start time t0 to the time t1, to 40% from the time t1 to the time t2, to 60% from the time t2 to the time t3, and after the time t3 has elapsed (steady state) ) Outputs a control command so that the duty is 67%. As a result, the current waveform flowing in the motor 13 is controlled in a sawtooth shape that alternately repeats rising and falling, and the current at the time of starting the motor 13 can be suppressed to a current limit target value or less. As a result, since the voltage drop resulting from the overload of the battery 1 does not occur, the motor 13 can be stably started by a battery-driven device.
[0032]
In the first embodiment and the second embodiment described above, the description has been made on the assumption that the rated voltage of the motor 13 is 6V and the detection voltage by the voltage detection circuit 7 is 9V. The duty of the control signal for driving was set to 67%. When the voltage of the battery 1 decreases and the detection voltage by the voltage detection circuit 7 decreases, the duty is gradually increased. When the detection voltage reaches 6V, the duty of the control signal is set to 100%.
[0033]
When the battery 1 is consumed, the duty of the control signal does not have to be 100% even when the voltage detected by the voltage detection circuit 7 falls below the rated voltage of the motor 13. For example, when the battery 1 is consumed and the voltage by the battery 1 is lower than a predetermined voltage (for example, 5V), the upper limit of the duty of the control signal is limited to 80%, for example. Thereby, since the discharge power of the battery 1 is limited in a state where the battery 1 is exhausted, an overload on the battery 1 can be prevented and the battery 1 can be protected.
[0034]
The upper limit of the duty of the control signal may be limited when the temperature of the battery 1 is detected and the detected temperature falls below a predetermined temperature. In this case, a temperature sensor is provided in the vicinity of the battery 1 and this temperature detection signal is input to the arithmetic circuit 8. Thereby, since the discharge power of the battery 1 is limited in a state where the capacity of the battery 1 is reduced at a low temperature (for example, 0 ° C. or less), an overload on the battery 1 can be prevented and the battery 1 can be protected. .
[0035]
The operation of changing the duty of the control signal according to the detection voltage by the voltage detection circuit 7 or limiting the upper limit of the duty of the control signal is performed only in a state where no power is supplied from an external power source (not shown). It may be. The external power source is an AC / DC adapter or the like. As described above, when an external power source (not shown) is connected to the terminal 3 and the terminal 3 ′ in FIG. 1 and the power is supplied from this external power source, the voltage from the external power source is connected to the voltage detection circuit via the signal line 21. 7 is detected. In general, since the external power supply is configured to generate a constant voltage, it is considered that the voltage fluctuation accompanying the driving of the motor 13 occurs when the battery 1 is supplied with power. Therefore, the arithmetic circuit 8 changes or restricts the duty of the control signal only when the voltage via the signal line 21 is not detected by the voltage detection circuit 7, that is, when power is supplied from the battery 1. . As a result, useless processing by the arithmetic circuit 8 can be omitted and the burden on the arithmetic circuit 8 can be reduced.
[0036]
The arithmetic circuit 8 sets the duty of the control signal to a fixed value when the voltage via the signal line 21 is detected by the voltage detection circuit 7, that is, when power is supplied from an external power source (not shown). May be. As described above, since it is considered that the external power supply does not cause voltage fluctuations due to the driving of the motor 13, the arithmetic circuit 8 changes the duty of the control signal to a fixed value when power is supplied from the external power supply. The fixed value in this case may be determined in advance according to the supply voltage from the external power supply and stored in a memory (not shown) in the arithmetic circuit 8.
[0037]
The present invention can be applied to devices including a battery-driven motor, such as a camera, a toy, and a peripheral device for a personal computer.
[0039]
【The invention's effect】
According to the present invention, the DC motor can be driven within the rating even at the start.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a motor control circuit according to a first embodiment of the present invention.
FIG. 2 illustrates the relationship among the control signal level input to the pre-driver, the drive signal level output from the pre-driver, the state of the P-channel MOS-FET and the N-channel MOS-FET, and the operating state of the motor. FIG.
FIG. 3 is a diagram illustrating an example of a waveform of a control signal when a voltage supplied to a motor exceeds a rated voltage of the motor.
FIG. 4 is a diagram showing a duty of a control signal at the time of starting a motor.
FIG. 5 is a diagram illustrating a waveform example of a control signal having a duty of 20%.
FIG. 6 is a diagram illustrating a waveform example of a control signal having a duty of 40%.
7 is a diagram illustrating a waveform of a current flowing through a motor during control according to FIG.
FIG. 8 is a diagram showing a current waveform when a motor is driven with a duty of 100%.
[Explanation of symbols]
1 ... battery, 5 ... stabilization circuit,
7 ... voltage detection circuit, 8 ... arithmetic circuit,
9 ... Output control circuit, 10 ... Pre-driver,
11 ... P-channel MOS-FET, 12 ... N-channel MOS-FET,
13 ... Motor

Claims (7)

Voltage detection means for detecting the voltage supplied from the power supply;
A DC motor;
In accordance with the voltage detection value by the voltage detection means, calculation means for calculating the drive duty so that the effective voltage applied to the DC motor does not exceed the rated value of the DC motor ;
And motor driving means for applying the supply voltage to the DC motor at a predetermined duty,
The drive current that flows to the DC motor when the voltage is applied to the DC motor with a first duty at the start of driving the DC motor is a predetermined time according to the characteristics of the DC motor. A time t1 until turning, and a time t2 until the driving current flowing through the DC motor starts to increase again when the voltage is applied to the DC motor at a second duty higher than the first duty after the time t1. Storage means for storing information indicating
Based on the stored information, the time t2 is set at the first duty until the time t1 elapses from the start of driving of the DC motor, and at the second duty until the time t2 elapses after the time t1 elapses. Control means for controlling the motor driving means so as to apply a voltage to each of the DC motors at a driving duty calculated by the calculating means after the passage ,
The motor driving apparatus characterized in that the first duty and the second duty are lower than the driving duty . The motor drive device according to claim 1,
Determination means for determining whether the power source is a battery or an external power source,
The motor drive device characterized in that the control means performs the control on the motor drive means at the start of driving of the DC motor when the battery is determined by the determination means. In the motor drive device according to claim 2,
Said computing means, said the effective voltage applied to the DC motor is calculated so as to lower the driving duty so as not to exceed the rated value of the direct current motor, the voltage value detected by said voltage detecting means decreases the effective calculated to increase the driving duty in the range in which the voltage does not exceed the rated value, the voltage detection value in the case of less than the predetermined voltage and limits the driving duty to a predetermined value less than 100% Motor drive device . In the motor drive device according to claim 2 or 3,
A temperature detecting means for detecting the temperature of the battery;
The calculating means sets the driving duty to a predetermined value lower than 100% when the battery is determined by the determining means and the temperature detection value by the temperature detecting means is not more than a predetermined temperature. Drive device . In the motor drive device according to any one of claims 2 to 4,
The motor drive apparatus according to claim 1, wherein the external power source is constituted by an AC / DC adapter. In the motor drive device according to any one of claims 1 to 5,
Said DC motor, a motor drive device and repeating the driving state and a stop state by the duty. A camera comprising the motor drive device according to claim 1.

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