JP2010283908A - Drive circuit of brushless motor, drive method, and motor unit and electronic equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive circuit for stabilizing rotational speed of motors. <P>SOLUTION: A target rotational speed determination section 60 receives a pulse-modulated control signal CTL that has a duty ratio corresponding to a target rotational speed of a brushless vibrating motor 1 to be driven. The target rotational speed determination section 60 determines the target rotational speed based on the duty ratio of the control signal CTL, and generates a rotational speed setting signal S1 according to the target rotational speed. A control section 20 generates a drive signal based on the rotational speed setting signal S1 and an FG signal indicating the rotational speed of the vibrating motor 1. An H bridge circuit 10 is connected to a coil of the vibrating motor 1, and controls coil conduction state based on the drive signal. The control section 20 rotates the vibrating motor 1 with a full torque for a period from the start of driving the vibrating motor 1 until the current rotational speed indicated by the FG signal reaches a target rotational speed indicated by the rotational speed setting signal S1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for driving a brushless motor.

  An electronic device such as a mobile phone terminal or a pager (pager) is equipped with a vibration motor in order to notify the user of an incoming call. In this vibration motor, an eccentric weight is connected to a rotation shaft, and the electronic device is vibrated by rotating the rotor. In such a vibration motor, since a weight connected as a load is eccentric, a drive circuit dedicated to the vibration motor is used.

  There are brush motors and brushless motors as vibration motors. When driving a brushless type vibration motor, there is a problem that the start time and the stop time become long because the rotor is heavy. When sequence control such as the high-speed start-up mode described in Patent Document 1 is performed, the start-up time can be shortened.

International Publication No. 08/026319 Pamphlet

  However, the high-speed activation described in Patent Document 1 is controlled to rotate at full torque for a certain period from the start of driving of the motor. Therefore, due to variations in various characteristics of the motor including impedance, a situation may occur where the target rotational speed is exceeded for each individual motor or the target rotational speed is not reached. That is, even when the same control signal is given, the number of rotations of the motor varies from one motor unit to another, so that the amount of vibration becomes unstable, resulting in a decrease in yield.

  The present invention has been made in view of such circumstances, and one of the exemplary purposes of an embodiment thereof is to provide a motor driving technique capable of obtaining a stable rotational speed.

  One embodiment of the present invention relates to a brushless motor drive circuit. The brushless motor drive circuit receives a pulse-modulated control signal having a duty ratio corresponding to the target rotational speed of the brushless motor to be driven, determines the target rotational speed based on the duty ratio of the control signal, and sets the target rotational speed. And a control unit for generating a drive signal based on the rotation speed setting signal and a frequency generation signal indicating the rotation speed of the brushless motor, and a coil of the brushless motor. And a bridge output circuit for controlling the conduction state of the coil based on the drive signal. The control unit generates a drive signal for rotating the brushless motor at full torque from the start of driving the brushless motor until the rotation speed of the brushless motor indicated by the frequency generation signal reaches the target rotation speed indicated by the rotation speed setting signal.

  According to this aspect, the target rotational speed of the motor can be set according to the duty ratio of the control signal, and the motor can be quickly rotated to the target rotational speed defined by the control signal at the time of startup. That is, it is possible to shorten the startup time and stabilize the rotational speed.

  The rotation speed setting signal may have a frequency corresponding to the target rotation speed. The control unit includes a rotation detection unit that generates an activation period setting signal that is asserted during a period from the start of driving until the frequencies of the rotation speed setting signal and the frequency generation signal coincide with each other, and the rotation speed of the brushless motor is set to the target rotation speed. A speed control unit that generates a pulse width modulation signal whose duty ratio is adjusted so as to approach, and a logic unit that generates a drive signal based on a start period setting signal, a pulse width modulation signal, and a frequency generation signal . The logic unit generates the drive signal having a duty ratio of 100% during a period when the activation period setting signal is asserted, and a drive having a duty ratio corresponding to the pulse width modulation signal during the period when the activation period setting signal is negated. A signal may be generated.

The control unit may transition to the activated state and start driving the brushless motor when the period in which the control signal is at the high level in the stopped state continues for a predetermined first period.
In this case, it is possible to prevent the motor from starting unintentionally when the control signal instantaneously becomes a high level in the stop state.

In the normal driving state in which the brushless motor is rotated at the number of rotations corresponding to the duty ratio of the control signal, the control unit transitions to the reverse brake state when the period during which the control signal is at the low level continues for the second period. In the state, the bridge output circuit may apply reverse brake to the brushless motor for a predetermined reverse brake period.
In this case, the motor can be stopped in a short time.

  Another aspect of the present invention is a motor unit. This motor unit includes a brushless vibration motor, a Hall element that outputs a Hall signal indicating positional information of the rotor of the vibration motor, and the brushless motor drive circuit according to any one of the above aspects that drives the vibration motor based on the Hall signal. A control signal is inputted from the outside, a control terminal connected to the brushless motor driving circuit, a power supply voltage is applied from the outside, a power supply terminal connected to the brushless motor driving circuit, a ground voltage is applied from the outside, and a brushless A ground terminal connected to the motor drive circuit.

  Yet another embodiment of the present invention is an electronic device. This electronic device includes a communication unit that communicates with a base station and generates a control signal, and the motor unit described above.

  Yet another embodiment of the present invention relates to a method for driving a brushless motor. This method monitors a pulse-modulated control signal having a duty ratio according to the target rotational speed of the brushless motor, determines the target rotational speed based on the duty ratio of the control signal, and sets the rotational speed according to the target rotational speed. The step of generating a signal, the step of generating a frequency generation signal indicating the rotation speed of the brushless motor based on the Hall signal from the Hall element, and the rotation speed of the brushless motor indicated by the frequency generation signal from the start of driving of the brushless motor And a step of rotating the brushless motor at full torque until a target rotational speed indicated by the rotational speed setting signal is reached.

  It should be noted that any combination of the above-described constituent elements, and those in which constituent elements and expressions of the present invention are mutually replaced between methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to an aspect of the present invention, the rotational speed of the brushless motor can be stabilized.

It is a circuit diagram which shows the structure of an electronic device provided with the motor unit which concerns on embodiment. It is a time chart which shows the operation example of the motor unit of FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components and members shown in the drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. In the drawings, some of the members that are not important for describing the embodiment of the present invention are omitted.

  In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are physically directly connected, or the member A and the member B are electrically connected. The case where it is indirectly connected through another member that does not affect the state is also included.

  Embodiments described herein relate generally to a brushless vibration motor drive circuit mounted on an electronic device having a communication function such as a mobile phone terminal. Such an electronic device includes a communication unit that communicates with the base station. For example, when an incoming call is detected from the base station, the vibration motor is rotated to notify the user of the incoming call.

  FIG. 1 is a circuit diagram illustrating a configuration of an electronic device 6 including a motor unit 2 according to an embodiment. The electronic device 6 includes a motor unit 2, a communication unit 4, and an antenna 5. The communication unit 4 is connected to the antenna 5 and communicates with the base station. The communication unit 4 rotates the vibration motor 1 when receiving a call, generates a control signal CTL for stopping, and outputs the control signal CTL to the motor unit 2.

The motor unit 2 is a three-terminal device, and specifically includes a power supply terminal P3 that receives the power supply voltage VDD, a ground terminal P4 that receives the ground voltage VGND, and a control terminal P5 that receives the control signal CTL.
The motor unit 2 includes the vibration motor 1 and the motor drive circuit 100, and constitutes one package.

  The vibration motor 1 is a brushless motor with a weight eccentric to the rotor shaft, and is formed such that drive voltages OUT1 and OUT2 can be applied to both terminals P1 and P2 of the coil from the outside.

  The motor drive circuit 100 controls the rotation of the vibration motor 1 based on the control signal CTL. Hereinafter, the configuration of the motor drive circuit 100 will be described.

  The motor drive circuit 100 includes a H bridge circuit 10, a control unit 20 (20a to 20c), a hall signal processing unit 40, and a target rotational speed determination unit 60, and is a functional IC integrated on one semiconductor substrate.

  The hall signal processing unit 40 is provided to process hall signals H + and H− indicating the position (polarity) of the rotor of the vibration motor 1. The hall signal processing unit 40 includes a hall element 3, an offset cancel circuit 42, an amplifier 44, a sample hold circuit 46, and a comparator 48. In the present embodiment, the Hall element 3 is integrated in the motor drive circuit 100. When the Hall element 3 is built in the IC, the amplitude of the Hall signal is smaller and the offset is larger than when a discrete element is used.

  The hall element 3 has four terminals, which are connected to the offset cancel circuit 42. The offset cancel circuit 42 cancels the offset of the Hall element 3 and generates Hall signals H + and H− having opposite phases indicating the position of the rotor of the vibration motor 1. The hall signals H + and H− have a frequency corresponding to the rotational speed of the motor. Since the Hall signal output from the offset cancel circuit 42 is weak, it is amplified by the amplifier 44 and sampled and held by the sample and hold circuit 46. The comparator 48 compares the sampled and held Hall signals H + and H−, converts them into a so-called FG (Frequency Generation) signal having a rectangular wave shape, and outputs it to the control unit 20.

  The configuration of the block from the Hall element 3 to the comparator 48 via the offset cancel circuit 42, the amplifier 44, and the sample hold circuit 46 may be a known technique, and is not particularly limited in the present invention. Further, when the Hall element 3 is constituted by a discrete element, the amplifier 44 and the sample hold circuit 46 may be omitted.

  The H bridge circuit 10 includes a plurality of switches connected to terminals P1 and P2 of the vibration motor 1 to be driven. Specifically, the H bridge circuit 10 includes a first high side transistor MH1, a second high side transistor MH2, a first low side transistor ML1, and a second low side transistor ML2. The H bridge circuit 10 corresponds to a bridge output circuit for driving the vibration motor 1. The first high side transistor MH1 and the first low side transistor ML1 are connected in series between the power supply terminal P3 and the ground terminal P4. Similarly, the second high side transistor MH2 and the second low side transistor ML2 are also connected in series between the power supply terminal P3 and the ground terminal P4. In the present embodiment, the high side transistors MH1 and MH2 are P channel MOSFETs, and the low side transistors ML1 and ML2 are N channel MOSFETs. These transistors may all be N-channel MOSFETs or may be bipolar transistors.

  A first drive voltage OUT1 at a connection point between the first high-side transistor MH1 and the first low-side transistor ML1 is applied to the first terminal P1 of the vibration motor 1. The on / off states of the first high-side transistor MH1 and the first low-side transistor ML1 are controlled by a first high-side drive signal SH1 and a first low-side drive signal SL1 that are applied to the gates of the transistors. When the first high-side transistor MH1 is on, the first drive voltage OUT1 is the power supply voltage VDD, and when the first low-side transistor ML1 is on, the first drive voltage OUT1 is the ground potential VGND. When both of the two transistors MH1 and ML1 are off, the first terminal P1 of the vibration motor 1 is in a high impedance state.

  Similarly, the second drive voltage OUT2 at the connection point between the second high-side transistor MH2 and the second low-side transistor ML2 is connected to the second terminal P2 of the vibration motor 1. The on / off states of the second high side transistor MH2 and the second low side transistor ML2 are controlled by a second high side drive signal SH2 and a second low side drive signal SL2 applied to the gates of the transistors.

  In the present embodiment, the vibration motor 1 is driven by setting the high-side transistor MH1 and the low-side transistor ML2 as a pair and the high-side transistor MH2 and the low-side transistor ML1 as another pair and alternately turning on and off these pairs. At that time, the length of the ON period is adjusted based on the pulse signal PWM.

  The motor unit 2 changes the following states.

Stop state φ1
The state where the vibration motor 1 is stopped. The control signal CTL is fixed at a low level.

Starting state φ2
The vibration motor 1 is rotated at full torque (100% duty ratio).

Normal drive state φ3
The vibration motor 1 is rotated at a target rotational speed corresponding to the duty ratio of the control signal CTL.

Reverse brake state φ4
Apply reverse brake to vibration motor 1.

  The target rotational speed determination unit 60 receives a pulse-modulated control signal CTL having a duty ratio corresponding to the target rotational speed of the vibration motor 1. The target rotational speed determination unit 60 detects the duty ratio of the control signal CTL, determines the target rotational speed set by the communication unit 4, and generates a rotational speed setting signal S1 corresponding to the target rotational speed.

  The control unit 20 generates drive signals SH 1, SH 2, SL 1, SL 2 based on the rotation speed setting signal S 1 and the FG signal indicating the current rotation speed of the vibration motor 1, and supplies them to the H bridge circuit 10.

  The control unit 20 is in the above-described activation state φ2 during the period from the start of driving of the vibration motor 1 until the current rotation speed of the vibration motor 1 indicated by the FG signal reaches the target rotation speed indicated by the rotation speed setting signal S1, Drive signals SH1, SH2, SL1, and SL2 are generated so that the vibration motor 1 rotates at full torque.

  In order to realize the above functions, the motor unit 2 specifically has the following characteristics.

The rotation speed setting signal S1 generated by the target rotation speed determination unit 60 has a frequency corresponding to the target rotation speed. For example, the target rotational speed determination unit 60 includes an edge detection unit 62 and a counter 64.
Contains. The edge detector 62 detects a positive edge and a negative edge of the control signal CTL. The counter 64 counts the time interval between edges detected by the edge detection unit 62 (that is, the high period and the low period) using the reference clock signal CK. By this count operation, the duty ratio of the control signal CTL is measured. In the motor unit 2, a target rotational speed is determined for each duty ratio. For example, a duty ratio of 70% corresponds to 10,000 rpm, and 80% corresponds to 12000 rpm. The counter 64 uses the reference clock signal CK to generate a rotation speed setting signal S1 having a frequency corresponding to the target rotation speed.

  The control unit 20 includes a logic unit 20a, a rotation detection unit 20b, and a speed control unit 20c.

  The rotation detection unit 20b receives the rotation speed setting signal S1 and the FG signal, and generates an activation period setting signal S2. Specifically, the rotation detection unit 20b asserts the activation period setting signal S2 (high level) from the start of driving of the vibration motor 1 until the frequency of the rotation speed setting signal S1 matches the frequency of the FG signal. Then, negate (low level). That is, the period during which the activation period setting signal S2 is asserted is the activation state φ2.

  The speed control unit 20c receives the rotation speed setting signal S1 and the FG signal and generates a pulse width modulation signal (PWM signal). The duty ratio of the PWM signal is adjusted so that the rotational speed of the vibration motor 1 indicated by the speed controller 20c and the FG signal approaches the target rotational speed indicated by the rotational speed setting signal S1. The speed control unit 20c includes, for example, a phase detection unit 50, an oscillator 52, and a PWM comparator 54. The phase detector 50 monitors the timing of the edge (for example, positive edge) of the rotation speed setting signal S1 and the edge (for example, positive edge) of the FG signal, and increases or decreases the threshold voltage Vth before and after the two timings. Let For example, the phase detection unit 50 may include a block that generates an up / down signal corresponding to the result of the phase comparison, and a capacitor that is charged / discharged according to the up / down signal.

  The oscillator 52 generates a triangular wave or sawtooth wave periodic signal OSC. The PWM comparator 54 slices the periodic signal OSC at the level of the threshold voltage Vth, and generates a PWM signal whose level transitions at each intersection of the two signals. The duty ratio of the PWM signal changes according to the level of the threshold voltage Vth, and is stabilized at a value in which the phase of the edge of the rotation speed setting signal S1 and the edge of the FG signal coincide. The configuration of the speed control unit 20c is not limited to that shown in FIG. 1, and other known techniques may be used.

  The logic unit 20a generates drive signals SH1, SH2, SL1, and SL2 based on the activation period setting signal S2, the PWM signal, and the FG signal. Specifically, the logic unit 20a generates drive signals SH1, SH2, SL1, and SL2 having a duty ratio of 100% in the activation state φ2 in which the activation period setting signal S2 is asserted. Thereafter, when the activation period setting signal S2 is negated, the state transits to the normal drive state φ3, and drive signals SH1, SH2, SL1, and SL2 having a duty ratio corresponding to the PWM signal are generated.

In addition, when the period during which the control signal CTL is at the high level in the stop state φ1 (the control signal CTL is fixed at the low level) continues for the predetermined first period T _RISE , the control unit 20 transitions to the activation state φ2. The drive of the vibration motor 1 is started.

In the normal drive state φ3 in which the vibration motor 1 is rotated at the target rotational speed corresponding to the duty ratio of the control signal CNT, the control unit 20 performs reverse rotation when the period during which the control signal CTL is at the low level continues for the second period T _FALL. Transition to the brake state φ4. When the reverse brake period _TBRK elapses in the reverse brake state φ4, the state changes to the stop state φ1. The reverse brake period T _BRK is a period until the rotational speed of the motor decreases to a certain value, or a predetermined fixed time.

The first period T _RISE and the second period T _FALL , in other words, the time constant of the filter 32 is set longer than the cycle of the control signal CTL subjected to pulse width modulation.

  Monitoring of the level and period of the control signal CTL referred to at the time of state transition can be executed using the edge detection unit 62 and the counter 64 of the target rotation speed determination unit 60.

  The above is the configuration of the motor unit 2. Next, the operation will be described. FIG. 2 is a time chart showing an operation example of the motor unit 2 of FIG.

Prior to time t0, the power supply voltage VDD is supplied, and the motor drive circuit 100 is in the stop state φ1. At time t0, the control signal CTL becomes high level, and the start of rotation of the vibration motor 1 is instructed. The high level of the control signal CTL transits to the activation state φ2 at the timing t1 when the first period T _RISE lasts.

  During the startup state φ2, the startup period setting signal S2 is asserted, the vibration motor 1 is driven at full torque (100% duty), and its rotational speed increases rapidly. Thereafter, when the rotational speed of the vibration motor 1 reaches the target rotational speed at time t2, the activation period setting signal S2 is negated, and the normal driving state φ3 is transitioned (time t3). FIG. 2 shows a waveform when driving the vibration motor 1 having different impedances.

  When transitioning to the normal drive state φ3, the vibration motor 1 is driven at a target rotational speed corresponding to the duty ratio of the control signal CTL by using the PWM signal.

At time t4, the control signal CTL becomes low level (duty ratio 0%), and the stop of the vibration motor 1 is instructed. At time t5 after the elapse of the second period T _FALL from time t4, the state changes to the reverse brake state φ4. During the reverse brake period _TBRK , a torque in the direction opposite to the rotation direction is applied to the vibration motor 1, the number of rotations of the vibration motor 1 rapidly decreases, and the vibration motor 1 stops.

At time t6, the stop state φ1 is entered. In this state, a control signal CTL having a certain pulse width is input, but since the high level is not maintained for the first period T _RISE , the stop state φ1 is maintained without transitioning to the start state φ2.

  The above is the operation of the motor unit 2.

The motor unit 2 according to the embodiment has the following advantages.
1. Since the control signal CTL can use the signal of the conventional brush vibration motor platform as it is, the designer of the electronic device 6 replaces the conventional brush vibration motor unit with the motor unit 2 according to the embodiment. By replacing, a brushless vibration motor can be used easily.

2. The brushed vibration motor does not rotate even if a signal having the same phase is applied to both ends of the vibration motor 1. Therefore, in the conventional vibration motor platform with a brush, the duty ratio and level of the control signal CTL are allowed to fluctuate non-zero when the motor is stopped.
On the other hand, since the brushless motor rotates even when in-phase signals are applied to both ends thereof, a malfunction due to the control signal CTL having a non-zero duty ratio or level becomes a problem. In the stopped state, the motor unit 2 according to the embodiment is mounted on the vibration motor platform with a brush because the vibration motor 1 does not rotate even if the control signal CTL becomes high level for a period shorter than the first period _TRISE. Even then, no malfunction occurs (after time t6 in the time chart).

  3. At startup, the current rotational speed of the vibration motor 1 is monitored by referring to the FG signal, and the motor is rotated at full torque until the rotational speed matches the target value. . Further, even if the motor characteristics (impedance) vary as shown in FIG. 2, it can be increased to the target rotational speed specified by the control signal CTL, and the performance and yield of the motor unit 2 can be improved. Can do.

  4). Furthermore, since the motor unit 2 according to the embodiment applies reverse braking when the duty ratio of the control signal CTL becomes the second state (L level), the motor unit 2 can stop the rotation in a short period (time t5 in the time chart). ~ T6).

  5. The motor unit 2 according to the embodiment can be mounted on a conventional two-wire system, that is, a platform for a brushless motor that operates with only the power supply voltage VDD and the ground voltage VGND. In this case, the control terminal P5 in FIG. 1 may be short-circuited with the power supply terminal P3. In this case, when the power supply voltage VDD is supplied, the state transits to the startup state φ2, and subsequently transitions to the normal drive state φ3. When the control signal CTL is the power supply voltage VDD, the duty ratio is 100%. Therefore, in the normal driving state φ3, the target rotational speed corresponding to the duty ratio of 100% is set, and the PWM for obtaining the target rotational speed is obtained. A signal is generated. When the supply of the power supply voltage VDD is stopped, a transition is made to the reverse brake state φ4, and the rotation of the vibration motor 1 is stopped in a short time.

  Those skilled in the art will understand that the above-described embodiment is an exemplification, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

In the embodiment, the case has been described in which the torque opposite to the rotation is applied at a duty ratio of 100% in the brake period _TBRK , but the present invention is not limited to this. For example, when the brake is applied, the control unit 20 may monitor the number of rotations of the rotor and adjust the duty ratio so that the reduction speed becomes a desired speed. In this case, it is possible to obtain brake characteristics that do not depend on characteristics of the brushless vibration motor to be driven, for example, internal friction.

In the embodiment, the configuration in which the first period T _RISE and the second period T _FALL are measured by the counter 64 has been described, but the present invention is not limited to this. For example, the first period T _RISE and the second period T _FALL may be measured using an analog or digital filter.

  In the embodiment, the case where the vibration motor 1 is driven has been described. However, the present invention can also be applied to driving a small motor mounted on a remote controller such as an ultra-small fan motor or a game machine.

  In the circuit described in the embodiment, the setting of the high level and low level logic values of the signal is an example, and can be freely changed by appropriately inverting it with an inverter or the like. Further, according to this, replacement of the AND gate and the OR gate can be easily conceived by those skilled in the art.

DESCRIPTION OF SYMBOLS 1 ... Vibration motor, 2 ... Motor unit, 3 ... Hall element, 4 ... Communication part, 5 ... Antenna, 6 ... Electronic device, 10 ... H bridge circuit, 20 ... Control part, 20a ... Logic part, 20b ... Rotation detection part , 20c ... speed control unit, 40 ... hall signal processing unit, 42 ... offset cancel circuit, 44 ... amplifier, 46 ... sample hold circuit, 48 ... comparator, 50 ... phase detection unit, 52 ... oscillator, 54 ... PWM comparator, 60 ... target rotational speed determination unit, 62 ... edge detection unit, 64 ... counter, 100 ... motor drive circuit, P3 ... power supply terminal, P4 ... ground terminal, P5 ... control terminal, P1 ... first terminal, P2 ... second terminal, S1 ... rotational speed setting signal, S2 ... start-up period setting signal, FG ... frequency generation signal.

Claims (10)

A pulse-modulated control signal having a duty ratio corresponding to the target rotational speed of the brushless motor to be driven is received, the target rotational speed is determined based on the duty ratio of the control signal, and the rotational speed corresponding to the target rotational speed A target rotational speed determination unit for generating a setting signal;
A controller that generates a drive signal based on the rotation speed setting signal and a frequency generation signal indicating the rotation speed of the brushless motor;
A bridge output circuit connected to the coil of the brushless motor and controlling the conduction state of the coil based on the drive signal;
With
The controller rotates the brushless motor at full torque from the start of driving the brushless motor until the rotational speed of the brushless motor indicated by the frequency generation signal reaches the target rotational speed indicated by the rotational speed setting signal. A brushless motor drive circuit that generates the drive signal. The rotation speed setting signal has a frequency corresponding to the target rotation speed,
The controller is
A rotation detection unit that generates an activation period setting signal that is asserted during a period from the start of driving until the frequency of each of the rotation speed setting signal and the frequency generation signal matches;
A speed control unit that generates a pulse width modulation signal in which a duty ratio is adjusted so that the rotation speed of the brushless motor approaches the target rotation speed;
A logic unit that generates the drive signal based on the activation period setting signal, the pulse width modulation signal, and the frequency generation signal;
Including
The logic unit generates the drive signal having a duty ratio of 100% during a period in which the activation period setting signal is asserted, and a period corresponding to the pulse width modulation signal in a period in which the activation period setting signal is negated. The brushless motor driving circuit according to claim 1, wherein the driving signal having a ratio is generated.   2. The control unit according to claim 1, wherein the control unit transitions to an activated state and starts driving the brushless motor when a period in which the control signal is at a high level in a stopped state continues for a predetermined first period. Brushless motor drive circuit.   In a normal driving state in which the brushless motor is rotated at a rotation speed corresponding to the duty ratio of the control signal, the control unit transitions to a reverse brake state when a period during which the control signal is at a low level continues for a second period. 2. The brushless motor drive circuit according to claim 1, wherein the bridge output circuit applies reverse brake to the brushless motor during a predetermined reverse brake period in the reverse brake state. A brushless vibration motor,
A hall element that outputs a hall signal indicating positional information of the rotor of the vibration motor;
The brushless motor drive circuit according to any one of claims 1 to 4, wherein the vibration motor is driven based on the hall signal.
A control terminal to which the control signal is input from the outside and connected to the brushless motor driving circuit;
A power supply voltage is applied from the outside and connected to the brushless motor drive circuit;
A ground voltage is applied from the outside and connected to the brushless motor drive circuit;
A motor unit comprising: A communication unit that communicates with a base station and generates the control signal;
A motor unit according to claim 5;
An electronic device comprising: A driving method of a brushless motor,
Monitor a pulse-modulated control signal having a duty ratio according to the target rotational speed of the brushless motor, determine the target rotational speed based on the duty ratio of the control signal, and set the rotational speed according to the target rotational speed Generating a signal;
Generating a frequency generation signal indicating the number of rotations of the brushless motor based on the Hall signal from the Hall element;
Rotating the brushless motor at full torque from the start of driving the brushless motor until the rotational speed of the brushless motor indicated by the frequency generation signal reaches the target rotational speed indicated by the rotational speed setting signal;
A method comprising the steps of: The rotation speed setting signal has a frequency corresponding to the target rotation speed,
The method
Generating an activation period setting signal that is asserted during a period from the start of driving until the frequency of each of the rotation speed setting signal and the frequency generation signal matches;
Generating a pulse width modulation signal in which a duty ratio is adjusted so that the rotation speed of the brushless motor approaches the target rotation speed;
Further comprising
The brushless motor is driven at a duty ratio of 100% during the period when the activation period setting signal is asserted, and the brushless motor is driven at the duty ratio of the pulse width modulation signal during a period when the activation period setting signal is negated. The method according to claim 7. Further comprising monitoring the control signal in a stopped state;
9. The method according to claim 7, wherein the driving of the brushless motor is started when a period during which the control signal is at a high level lasts for a predetermined first period. In the normal drive state in which the brushless motor is rotated at a rotation speed corresponding to the duty ratio of the control signal, the method further comprises the step of monitoring the control signal,
10. The reverse brake state is applied when a period during which the control signal is at a low level lasts for a second period, and the reverse brake is applied to the brushless motor for a predetermined reverse brake period. The method in any one of.

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