JP7599372B2 - MOTOR DRIVE CONTROL DEVICE, MOTOR UNIT, AND MOTOR DRIVE CONTROL METHOD - Google Patents

Description

The present invention relates to a motor drive control device, a motor unit, and a motor drive control method.

In general, when a motor having multiple phase coils is sinusoidally driven, it is known that the motor can be driven efficiently by matching the phase of the induced voltage in the coil and the phase of the coil current (phase current) for each phase of the motor.

However, due to the motor's rotational speed, motor load, and changes in motor characteristics due to temperature, a shift can occur between the phase of the induced voltage and the phase of the coil current (phase current), which can degrade the motor's driving efficiency.

As a technique for solving such problems, Patent Document 1 discloses a method for adjusting the phase of the drive voltage of a coil relative to the phase of the coil current of the motor. Specifically, the motor drive control device disclosed in Patent Document 1 provides a detection section for detecting induced voltage before and after the point where the induced voltage generated in a coil of a specified phase of the motor becomes zero (voltage zero cross point) by stopping the drive voltage of the coil. The motor drive control device then detects the phase of the induced voltage of the coil by comparing the magnitude of the coil terminal voltage with a threshold voltage in the detection section, and adjusts the phase of the drive voltage.

JP 2015-23734 A

However, the technology disclosed in Patent Document 1 requires that the coil be stopped during the detection period. Therefore, if the length of the period during which the coil is stopped (detection period) is not set appropriately, the motor drive waveform may be disturbed, and the motor rotation may become unstable.

The inventors therefore felt that a new motor drive control technology was needed to improve the drive efficiency of the motor.

The present invention aims to solve the above-mentioned problems and improve the driving efficiency of the motor.

A motor drive control device according to a representative embodiment of the present invention includes a control circuit that generates a drive control signal, which is a PWM signal for driving a motor having a coil of at least one phase, and a drive circuit that includes a high-side switch and a low-side switch that are connected in series to each other and are provided corresponding to the coil of each phase of the motor, and that alternately turns on and off the high-side switch and the low-side switch in response to the drive control signal to switch the direction of current flow to the coil of the corresponding phase, and the control circuit is synchronized with the induced voltage of the coil of a specified phase of the motor, and determines a target point of zero crossing of the coil current of the specified phase based on a position detection signal that corresponds to the rotational position of the rotor of the motor. a current zero-cross point estimation unit that compares, for each cycle of the PWM signal, the drive voltage of the coil of the specified phase with at least one of the on-period and off-period of the signal that turns on and off the high-side switch corresponding to the specified phase and estimates the zero-cross point of the coil current of the specified phase based on the comparison result; a phase adjustment determination unit that determines whether or not phase adjustment of the coil current is required based on the phase difference between the target point determined by the target point determination unit and the zero-cross point estimated by the current zero-cross point estimation unit; and a drive control signal generation unit that generates the drive control signal based on the determination result by the phase adjustment determination unit.

According to one aspect of the present invention, it is possible to improve the driving efficiency of the motor.

1 is a diagram showing a configuration of a motor unit equipped with a motor drive control device according to an embodiment of the present invention. 5 is a diagram for explaining a phase adjustment function of the motor drive control device according to the embodiment. FIG. 11 is a timing chart showing changes in the U-phase PWM signals Suu, Sul and the drive voltage Vu of the coil Lu when the U-phase coil current Iu switches from positive (+) polarity to negative (-) polarity. 11 is a timing chart showing changes in the U-phase PWM signals Suu, Sul and the drive voltage Vu of the coil Lu when the U-phase coil current Iu switches from negative (-) polarity to positive (+) polarity. 13 is a diagram for explaining a state when a positive coil current Iu flows through a U-phase coil Lu and a high-side switch QuH and a low-side switch QuL of the U-phase are turned off. FIG. 13 is a diagram for explaining a state when a negative coil current Iu flows through a U-phase coil Lu and a high-side switch QuH and a low-side switch QuL are turned off. FIG. 4 is a flowchart showing a flow of a motor drive control process performed by the motor drive control device according to the embodiment. 6 is a flowchart showing a process (step S4) of estimating a zero-cross point of the motor current in FIG. 5 . 6 is a flowchart showing a flow of a motor energization timing adjustment process (step S5) in FIG. 5; 5 is a timing chart showing changes in the voltages of the signals and the coil current Iu when the phase of the coil current Iu of the motor is adjusted by the motor drive control device according to the embodiment.

1. Overview of the embodiment First, an overview of a representative embodiment of the invention disclosed in this application will be described. Note that in the following description, as an example, reference numerals in the drawings corresponding to components of the invention are given in parentheses.

[1] A motor drive control device (1) according to a representative embodiment of the present invention includes a control circuit (2) that generates a drive control signal (Sd, Suu, Sul, Svu, Svl, Swu, Swl) which is a PWM signal for driving a motor (5) having a coil of at least one phase, and a drive circuit (3) that includes high-side switches (QuH, QvH, QwH) and low-side switches (QuL, QvL, QwL) connected in series to each other and provided corresponding to the coils (Lu, Lv, Lw) of each phase of the motor, and alternately turns on and off the high-side switch and the low-side switch in response to the drive control signal to switch the direction of current flow to the coil of the corresponding phase, and the control circuit synchronizes with the induced voltage of the coil of a predetermined phase (e.g., U phase) of the motor and, based on a position detection signal (Shu) corresponding to the rotational position of the rotor of the motor, The system is characterized by having a target point determination unit (12) that determines a target point (P(tp)) of the zero cross of the coil current of the specified phase, a current zero cross point estimation unit (14) that compares the drive voltage (Vu) of the coil of the specified phase with at least one of the on period (second period Th) and the off period of the high side switch (Suu) corresponding to the specified phase for each period of the PWM signal, and estimates the zero cross point (Q(tq)) of the coil current of the specified phase based on the comparison result, a phase adjustment determination unit (15) that determines whether or not phase adjustment of the coil current is required based on the phase difference (Δφ=tp-tq) between the target point determined by the target point determination unit and the zero cross point estimated by the current zero cross point estimation unit, and a drive control signal generation unit (16) that generates the drive control signal based on the determination result by the phase adjustment determination unit.

[2] In the motor drive control device described in [1] above, the current zero cross point estimation unit may determine whether the on-period of the drive voltage coincides with the on-period of the signal that turns the high-side switch on and off, detect at least one of the timing at which the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off switch from a state in which they coincide to a state in which they do not coincide, and the timing at which the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off switch from a state in which they do not coincide to a state in which they coincide, and estimate the detected timing as the zero cross point of the coil current of the specified phase.

[3] In the motor drive control device described in [2] above, the current zero cross point estimation unit may determine that the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off match when the difference (|Th-Tv|) between the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off is less than a threshold (Tth), and may determine that the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off do not match when the difference (|Th-Tv|) between the on-period of the drive voltage and the on-period of the signal that turns the high-side switch on and off is equal to or greater than a threshold (Tth).

[4] In the motor drive control device described in [3] above, the drive control signal generation unit generates the drive control signal so that when the on/off states of the high-side switch and the low-side switch are switched, a dead time period (Td) is formed during which the high-side switch and the low-side switch are simultaneously turned off, and the threshold value may be a value (Td) based on the dead time period.

[5] In the motor drive control device described in any one of [2] to [4] above, the current zero cross point estimation unit may determine the timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch switch from a state in which they match to a state in which they do not match to be a zero cross point at which the polarity of the coil current switches from positive to negative, and may determine the timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch switch from a state in which they do not match to a state in which they do not match to be a zero cross point at which the polarity of the coil current switches from negative to positive.

[6] In the motor drive control device described in any one of [1] to [5] above, the phase adjustment determination unit may calculate a phase difference between the target point and a zero cross point of the coil current, and instruct the drive control signal generation unit to shift the output timing of the drive control signal by a time corresponding to the phase difference.

[7] A motor unit (100) according to a representative embodiment of the present invention is characterized by comprising a motor drive control device (1) described in any one of [1] to [6] above and the motor (5).

[8] A method according to a representative embodiment of the present invention is a motor control method using a motor drive control device (1) that includes a control circuit (2) that generates a drive control signal, which is a PWM signal for driving a motor having a coil of at least one phase, and a drive circuit (3) that includes a high-side switch and a low-side switch connected in series to each other and provided corresponding to the coil of each phase of the motor, and that alternately turns on and off the high-side switch and the low-side switch in response to the drive control signal to switch the direction of current flow to the coil of the corresponding phase. This method includes a first step (S3) in which the control circuit determines a target point of zero crossing of the coil current of a predetermined phase based on a position detection signal that is synchronized with the induced voltage of the coil of a predetermined phase of the motor and corresponds to the rotational position of the rotor of the motor; a second step (S4) in which the control circuit compares the drive voltage of the coil of the predetermined phase with at least one of the on-period and off-period of the signal that turns on and off the high-side switch corresponding to the predetermined phase for each period of the PWM signal, and estimates the zero-crossing point of the coil current of the predetermined phase based on the comparison result; a third step (S52, S53) in which the control circuit determines whether or not phase adjustment of the coil current is required based on the phase difference between the target point determined in the first step and the zero-crossing point estimated in the second step; and a fourth step (S54 to S56) in which the control circuit generates the drive control signal based on the determination result in the third step.

2. Specific Examples of the Embodiments Specific examples of the embodiments of the present invention will be described below with reference to the drawings. In the following description, components common to the respective embodiments are designated by the same reference numerals, and repeated description will be omitted.

<Embodiment>
FIG. 1 is a diagram showing the configuration of a motor unit equipped with a motor drive control device according to an embodiment of the present invention.

The motor unit 100 shown in FIG. 1 includes a motor 5, a position detection device 6, and a motor drive control device 1.

Motor 5 is a motor having at least one coil. For example, motor 5 is a brushless DC motor having three-phase (U-phase, V-phase, and W-phase) coils (windings) Lu, Lv, and Lw.

The position detection device 6 is a device that generates a position detection signal Shu according to the rotation of the rotor of the motor 5. The position detection device 6 is, for example, a Hall element. The Hall element detects the magnetic poles of the rotor and outputs a Hall signal whose voltage changes according to the rotation of the rotor. The Hall signal is, for example, a pulse signal, and is input to the motor drive control device 1 as the position detection signal Shu.

In the motor unit 100, one Hall element serving as the position detection device 6 is disposed at a position corresponding to one of the coils Lu, Lv, Lw of the U-phase, V-phase, and W-phase of the motor 5. Therefore, the Hall signal output from the position detection device 6 is a signal synchronized with the induced voltage of one of the coils Lu, Lv, Lw of the U-phase, V-phase, and W-phase of the motor 5.

In this embodiment, one Hall element serving as the position detection device 6 is disposed at a position corresponding to, for example, the U-phase coil. As a result, the position detection signal (Hall signal) Shu is synchronized with the induced voltage of the U-phase coil Lu of the motor 5, and is a signal corresponding to the rotational position of the rotor of the motor 5.

Although details will be described later, in this embodiment, as a specific example, the position detection device 6 is disposed at a position where the rising edge of the position detection signal (Hall signal) Shu output from the position detection device 6 can be detected at a timing delayed by 30 electrical degrees from the zero cross point of the induced voltage of the U-phase coil Lu.

The motor drive control device 1 is a device that controls the drive of the motor 5. The motor drive control device 1 performs sine wave drive of the motor 5, for example, by a one-sensor drive method based on a position detection signal Shu from one position detection device 6 (Hall element) provided at a position corresponding to the U-phase coil Lu.

Specifically, the motor drive control device 1 includes a control circuit 2, a drive circuit 3, and a phase voltage detection circuit 4. The motor drive control device 1 receives a DC voltage Vdd from an external DC power supply (not shown). The DC voltage Vdd is supplied to a power supply line (not shown) in the motor drive control device 1 via, for example, a protection circuit, and is input as a power supply voltage to the control circuit 2 and the drive circuit 3 via the power supply line.

In addition, the DC voltage Vdd may not be directly supplied to the control circuit 2, but rather, for example, a voltage obtained by lowering the DC voltage Vdd using a regulator circuit may be supplied to the control circuit 2 as a power supply voltage.

The drive circuit 3 is a circuit that drives the motor 5 based on a drive control signal Sd output from the control circuit 2 described below. The drive control signal Sd is a signal for controlling the drive of the motor 5. For example, the drive control signal Sd is a PWM signal for sinusoidal drive of the motor 5.

The drive circuit 3 switches the connection destination of the coils of the motor 5 between the DC voltage Vdd and the ground potential GND based on the drive control signal Sd, thereby switching the direction of the motor current and rotating the motor 5. Specifically, the drive circuit 3 includes high-side switches QuH, QvH, QwH and low-side switches QuL, QvL, QwL that are provided corresponding to the coils Lu, Lu, Lw of each phase of the motor 5 and are connected in series with each other. The drive circuit 3 turns on and off the high-side switches QuH, QvH, QwH and the low-side switches QuL, QvL, QwL in response to the PWM signals Suu, Sul, Svu, Svl, Swu, Swl as the drive control signal Sd to switch the current flow direction of each coil Lu, Lv, Lw.

The PWM signals Suu, Sul, Svu, Svl, Swu, and Swl are input to each of the six high-side switches QuH, QvH, and QwH and the six low-side switches QuL, QvL, and QwL, and turn the corresponding switches on and off.

For example, the high-side switches QuH, QvH, and QwH are P-channel MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors), and the low-side switches QuL, QvL, and QwL are N-channel MOSFETs.

The high-side switches QuH, QvH, and QwH and the low-side switches QuL, QvL, and QwL may be other types of power transistors, such as an IGBT (Insulated Gate Bipolar Transistor).

As shown in FIG. 1, the U-phase high-side switch QuH and low-side switch QuL are connected in series between the DC voltage Vdd and the ground potential GND to form one switching leg (arm). The connection point between the high-side switch QuH and the low-side switch QuL is connected to one end of the coil Lu. The high-side switch QuH is switched on and off by the PWM signal Suu. The low-side switch QuL is switched on and off by the PWM signal Sul.

The V-phase high-side switch QvH and low-side switch QvL are connected in series between the DC voltage Vdd and the ground potential GND to form one switching leg. The connection point between the high-side switch QvH and the low-side switch QvL is connected to one end of the coil Lv. The high-side switch QvH is switched on and off by the PWM signal Svu. The low-side switch QvL is switched on and off by the PWM signal Svl.

The W-phase high-side switch QwH and low-side switch QwL are connected in series between the DC voltage Vdd and the ground potential GND to form one switching leg. The connection point between the high-side switch QwH and the low-side switch QwL is connected to one end of the coil Lw. The high-side switch QwH is switched on and off by the PWM signal Swu. The low-side switch QwL is switched on and off by the PWM signal Swl.

In addition, parasitic diodes are formed in each transistor of the high-side switches QuH, QvH, QwH and the low-side switches QuL, QvL, QwL, and these diodes function as freewheeling diodes that return the coil current to the DC voltage Vdd or ground potential GND.

The drive circuit 3 may have a pre-drive circuit for driving the high-side switch and the low-side switch of each phase based on the drive control signal Sd. Also, as shown in FIG. 1, a sense resistor for detecting the current of the motor 5 may be connected to the ground potential GND side of the drive circuit 3.

The phase voltage detection circuit 4 is a circuit for detecting the drive voltage of a coil of a specific phase of the motor 5. In this embodiment, the phase voltage detection circuit 4 detects, for example, the drive voltage Vu of the U-phase coil Lu and inputs it to the control circuit 2. The phase voltage detection circuit 4 is, for example, a resistive voltage divider circuit connected between one end of the coil Lu to which the U-phase high-side switch QuH and low-side switch QuL are connected and the ground potential GND.

Note that FIG. 1 shows an example of a configuration in which the drive voltage Vu of the coil Lu is divided by a resistive voltage divider circuit serving as the phase voltage detection circuit 4 and input to the control circuit 2, but the drive voltage Vu of the coil Lu may be input directly to the control circuit 2 without providing the phase voltage detection circuit 4.

The control circuit 2 is a circuit for comprehensively controlling the operation of the motor drive control device 1. In this embodiment, the control circuit 2 is a program processing device having a configuration in which a processor such as a CPU, various storage devices such as RAM, ROM, and flash memory, and peripheral circuits such as a counter (timer), an A/D conversion circuit, a D/A conversion circuit, a clock generation circuit, and an input/output interface circuit are connected to each other via a bus or a dedicated line. For example, the control circuit 2 is a microcontroller (MCU: Micro Controller Unit).

The control circuit 2 and the drive circuit 3 may be packaged as a single semiconductor integrated circuit (IC), or may be packaged as separate integrated circuits mounted on a circuit board and electrically connected to each other on the circuit board.

The control circuit 2 has a basic function of controlling the energization of the motor 5 by generating a drive control signal Sd and providing it to the drive circuit 3. Specifically, the control circuit 2 generates a drive control signal Sd based on a drive command signal Sc that indicates a target value for driving the motor 5 and is input from the outside (e.g., a higher-level device) and a position detection signal Shu that is input from the position detection device 6, and provides the drive control signal Sd to the drive circuit 3 so that the motor 5 is in the drive state specified by the drive command signal Sc.

In addition to the above basic functions, the control circuit 2 also has a function of adjusting the timing of current flow to the motor 5 so that the phase of the induced voltage in a coil of a specified phase of the motor 5 coincides with the phase of the coil current in order to improve the driving efficiency of the motor 5 (hereinafter also referred to as the "phase adjustment function").

As shown in FIG. 1, the control circuit 2 has, as functional units for realizing the above-mentioned functions, for example, a drive command analysis unit 11, a target point determination unit 12, a phase voltage input unit 13, a current zero cross point estimation unit 14, a phase adjustment determination unit 15, and a drive control signal generation unit 16.

The above-mentioned functional units of the control circuit 2 are realized, for example, by program processing of the MCU as the control circuit 2. Specifically, the processor constituting the MCU as the control circuit 2 performs various calculations according to the programs stored in the memory to control the various peripheral circuits constituting the MCU, thereby realizing the above-mentioned functional units.

The drive command analysis unit 11 receives, for example, a drive command signal Sc output from a higher-level device (not shown). The drive command signal Sc is a signal indicating a target value for driving the motor 5, for example, a speed command signal indicating a target rotation speed of the motor 5.

The drive command analysis unit 11 analyzes the target rotation speed specified by the drive command signal Sc. For example, if the drive command signal Sc is a PWM signal having a duty ratio corresponding to the target rotation speed, the drive command analysis unit 11 analyzes the duty ratio of the drive command signal Sc and outputs information on the rotation speed corresponding to that duty ratio as the target rotation speed S1.

The drive control signal generator 16 calculates the operation amount S3 of the motor 5 so that the rotation speed of the motor 5 coincides with the target rotation speed S1, and generates the drive control signal Sd based on the calculated operation amount S3. The function of the drive control signal generator 16 related to phase adjustment will be described later.

The drive control signal generating unit 16 has, for example, a PWM command unit 17 and a PWM signal generating unit 18. The PWM command unit 17 calculates the operation amount S3 of the motor 5 based on the target rotation speed S1 output from the drive command analyzing unit 11 and the judgment result S2 from the phase adjustment judgment unit 15 described later.

The operation amount S3 includes information specifying the drive amount of the motor 5 required to rotate the motor 5 at the target rotation speed S1. For example, when the motor 5 is PWM driven as in this embodiment, the operation amount S3 includes a value specifying the period (PWM period) of the PWM signal as the drive control signal Sd, a value specifying the on period of the PWM signal, and a value specifying the output timing of the PWM signal. Details of the value specifying the output timing of the PWM signal will be described later.

For example, the PWM command unit 17 calculates a value specifying the PWM period of the drive control signal Sd and a value specifying the on-period of the PWM signal based on the target rotation speed S1 output from the drive command analysis unit 11, and outputs them as the operation amount S3.

If the motor drive control device 1 has a feedback control function, for example, the PWM command unit 17 may calculate the actual rotation speed of the motor 5 based on the position detection signal Shu, and perform a PID (Proportional-Integral-Differential) control calculation so that the calculated actual rotation speed matches the target rotation speed S1 to calculate the operation amount S3 (PWM period and on-period) of the motor 5.

The PWM signal generating unit 18 generates the drive control signal Sd based on the operation amount S3 calculated by the PWM command unit 17. Specifically, the PWM signal generating unit 18 generates six types of PWM signals Suu, Sul, Svu, Svl, Swu, and Swl having PWM periods and on periods specified by the operation amount S3, and outputs them as the drive control signal Sd. The PWM signal Suu is a signal that switches the on/off of the high-side switch QuH of the U phase. The PWM signal Sul is a signal that switches the on/off of the low-side switch QuL of the U phase. The PWM signal Svu is a signal that switches the on/off of the high-side switch QvH of the V phase. The PWM signal Svl is a signal that switches the on/off of the low-side switch QvL of the V phase. The PWM signal Swu is a signal that switches the on/off of the high-side switch QwH of the W phase. The PWM signal Swl is a signal that switches the W-phase low-side switch QwL on and off.

In this embodiment, a dead time period Td is provided to prevent the high-side switch and the low-side switch constituting each switch leg of the U-phase, V-phase, and W-phase from being turned on at the same time. That is, the PWM signal generating unit 18 generates the drive control signal Sd (the six types of PWM signals described above) so that when the high-side switch and the low-side switch constituting each switch leg of the U-phase, V-phase, and W-phase are switched between on/off states, a dead time period Td is formed in which the high-side switch and the low-side switch are turned off at the same time. Details of the dead time period Td will be described later.

The target point determination unit 12, the phase voltage input unit 13, the current zero cross point estimation unit 14, and the phase adjustment determination unit 15 are functional units for realizing the phase adjustment function of the motor 5 described above. Before describing each functional unit in detail, an overview of the phase adjustment function according to this embodiment will be described.

FIG. 2 is a diagram for explaining the phase adjustment function of the motor drive control device 1 according to the embodiment.
The upper part of Figure 2 shows a waveform 200 of the position detection signal (Hall signal) Shu output from the position detection device 6, the middle part shows a waveform 201 of the drive voltage Vu of the U-phase coil Lu and a waveform 202 of the induced voltage in the U-phase coil Lu, and the lower part shows a waveform 203 of the coil current Iu of the U-phase coil Lu.

As mentioned above, generally, due to the motor's rotation speed, motor load, and changes in motor characteristics due to temperature, etc., a shift may occur between the phase of the motor's induced voltage and the phase of the coil current. For example, Figure 2 shows a case where the phase of the U-phase coil current Iu lags behind the phase of the induced voltage in the U-phase coil Lu.

As shown in FIG. 2, if a phase shift occurs between the coil current Iu and the induced voltage, the driving efficiency of the motor 5 decreases. Therefore, the motor drive control device 1 according to this embodiment detects the shift (phase difference) between the coil current Iu and the induced voltage, and adjusts the motor current supply timing so that the phase difference becomes small.

Specifically, first, the motor drive control device 1 detects the zero-cross point of the induced voltage by taking advantage of the fact that the position detection signal (Hall signal) Shu output from the position detection device 6 (Hall element) provided corresponding to a specified phase is synchronized with the induced voltage of the coil of the specified phase, and sets this as the target point P of the zero cross of the coil current Iu.

In this embodiment, for example, as shown in FIG. 2, the position detector 6 is pre-positioned at a position where the rising edge of the position detection signal Shu of the position detector 6 can be detected at a timing delayed by 30 electrical degrees from the zero-cross point of the induced voltage of the U-phase coil Lu. This allows the motor drive control device 1 to detect (estimate) the zero-cross point of the induced voltage of the coil Lu by detecting the edge of the position detection signal Shu.

The location of the position detection device 6 may be any location where the phase difference between the timing at which the rising edge of the position detection signal Shu is detected and the zero cross point of the induced voltage of a coil of a specified phase is known, and is not limited to the above example.

The motor drive control device 1 detects the rising edge or falling edge of the position detection signal Shu, and estimates the zero-cross point of the induced voltage from at least one of the detected edges. The motor drive control device 1 determines the estimated zero-cross point of the induced voltage as the target point P of the zero-cross of the coil current Iu.

The motor drive control device 1 then compares the drive voltage (phase voltage) of the coil of a specified phase (U phase in this embodiment) with at least one of the on-period and off-period of a signal for turning on and off the high-side switch corresponding to the specified phase, and estimates the zero-cross point Q of the coil current of the specified phase of the motor based on the comparison result. The method of estimating the zero-cross point of the coil current will be described in detail later.

Then, the motor drive control device 1 adjusts the phase of the coil current Iu so that the zero-cross point Q of the estimated coil current Iu coincides with the zero-cross target point P of the coil current Iu (the zero-cross point of the induced voltage). For example, as shown in Fig. 2, the phase of the coil current Iu is adjusted by adjusting the timing of application of the drive voltage Vu to the U-phase coil Lu (performing advance angle control or delay angle control) so that the zero-cross point Q of the U-phase coil current Iu coincides with the target point P. This enables the motor drive control device 1 to improve the drive efficiency of the motor 5.
Hereinafter, each of the functional units for realizing the above-mentioned phase adjustment function will be described in detail.

The target point determination unit 12 is synchronized with the induced voltage of a coil of a specified phase of the motor 5 and determines the target point of the zero crossing of the coil current of a specified phase based on the position detection signal Shu that corresponds to the rotational position of the rotor of the motor 5.

In this embodiment, the target point determination unit 12 detects the rising edge or falling edge of the position detection signal Shu that is synchronized with the induced voltage of the U-phase coil Lu, and determines the zero-cross point of the induced voltage of the U-phase coil Lu, i.e., the target point P of the zero-cross of the U-phase coil current Iu, based on the detected edge. For example, in FIG. 2, if the target point determination unit 12 detects the rising edge of the position detection signal Shu at time t1, the target point determination unit 12 determines time (timing) t0 that is 30 electrical degrees ahead of time t1 as the target point P. Note that the target point P is also determined in a similar manner when detecting the falling edge of the position detection signal Shu.

The phase voltage input unit 13 acquires the value of the voltage of a specific phase of the motor 5. For example, the phase voltage input unit 13 acquires the drive voltage Vu of the U-phase coil Lu detected by the phase voltage detection circuit 4, converts it into a digital value, and provides it to the current zero cross point estimation unit 14.

The current zero cross point estimation unit 14 is a functional unit that compares the drive voltage (phase voltage) of a coil of a specified phase with at least one of the on-period and off-period of a signal that turns on and off a high-side switch corresponding to the specified phase for each period of the drive control signal Sd, which is a PWM signal, and estimates the zero cross point of the coil current of the specified phase based on the comparison result. Below, the method of estimating the zero cross point of the coil current by the current zero cross point estimation unit 14 is explained in detail using figures.

FIG. 3A is a timing chart showing changes in the U-phase PWM signals Suu, Sul and the drive voltage Vu of the coil Lu when the U-phase coil current Iu switches from positive (+) polarity to negative (-) polarity.
FIG. 3B is a timing chart showing changes in the U-phase PWM signals Suu, Sul and the drive voltage Vu of the coil Lu when the U-phase coil current Iu switches from negative (-) polarity to positive (+) polarity.

In Figures 3A and 3B, from top to bottom, the waveforms of the U-phase coil current Iu, the PWM signal Suu for driving the U-phase high-side switch QuH, the PWM signal Sul for driving the U-phase low-side switch QuL, and the drive voltage Vu of the U-phase coil Lu are shown in that order. Note that in Figures 3A and 3B, the horizontal axis represents time, and the vertical axis represents current or voltage, respectively.

FIG. 4A is a diagram for explaining a state when the high-side switch QuH and the low-side switch QuL of the U-phase are turned off while a positive (+) polarity coil current is flowing through the U-phase coil Lu.
FIG. 4B is a diagram for explaining a state when the U-phase high-side switch QuH and low-side switch QuL are turned off while a negative (−) polarity coil current is flowing through the U-phase coil Lu.

For example, as shown in FIG. 3A, when the PWM signal Suu is at a high level and the PWM signal Sul is at a low level, the U-phase high-side switch QuH is turned on and the U-phase low-side switch QuL is turned off. At this time, current flows from the DC voltage Vdd through the U-phase high-side switch QuH to the U-phase coil Lu, so the U-phase coil current Iu has a positive (+) polarity.

In this state, that is, when a positive (+) coil current Iu flows through the U-phase coil Lu, when the U-phase high-side switch QuH and low-side switch QuL are both turned off, the coil Lu tries to continue to pass current. Therefore, as shown in FIG. 4A, a positive coil current Iu flows from the ground potential GND through the parasitic diode of the low-side switch QuL. As a result, the drive voltage Vu of the coil Lu drops to near the ground potential GND.

Therefore, as shown in FIG. 3A, when the U-phase coil current Iu is positive (+) polarity, during the dead time period Td when both the U-phase high-side switch QuH and the U-phase low-side switch QuL are off, the U-phase drive voltage Vu is at a low level.

As a result, as shown in FIG. 3A, during the period when the U-phase coil current Iu is positive (+), in one cycle of the PWM signal Suu, the first period Tv during which the drive voltage Vu of the U-phase coil Lu is at a high level coincides with the second period Th during which the PWM signal Suu that switches the U-phase high-side switch QuH on and off is at a high level.

On the other hand, as shown in FIG. 3B, when the PWM signal Suu is at a low level and the PWM signal Sul is at a high level, the U-phase high-side switch QuH is turned off and the U-phase low-side switch QuL is turned on. At this time, current flows from the U-phase coil Lu to the ground potential GND via the U-phase low-side switch QuL, so the U-phase coil current Iu has a negative (-) polarity.

In this state, i.e., when a negative (-) coil current Iu flows through the U-phase coil Lu, when the U-phase high-side switch QuH and low-side switch QuL are both turned off, the coil Lu tries to continue to pass current. Therefore, as shown in FIG. 4B, a negative coil current Iu flows from the U-phase coil Lu to the DC voltage Vdd side via the parasitic diode of the high-side switch QuH. As a result, the drive voltage Vu of the coil Lu rises to near the DC voltage Vdd.

Therefore, as shown in FIG. 3B, when the U-phase coil current Iu is negative (-) polarity, during the dead time period Td when both the U-phase high-side switch QuH and the U-phase low-side switch QuL are off, the U-phase drive voltage Vu is at a high level.

As a result, as shown in FIG. 3B, during the period when the U-phase coil current Iu is negative (-) polarity, in one cycle of the PWM signal Suu, the second period Th during which the PWM signal Suu that switches the U-phase high-side switch QuH on and off is at a high level is longer than the first period Tv during which the drive voltage Vu of the U-phase coil Lu is at a high level, and the first period Tv and the second period Th do not match.

As described above, when the motor is PWM driven, in one cycle of the PWM signal Suu, the first period Tv and the second period Th coincide during the period when the coil current of a specified phase is positive, and the first period Tv and the second period Th do not coincide during the period when the coil current is negative.

Therefore, as shown in Figures 3A and 3B, by detecting the timing of the transition from a state in which the first period Tv and the second period Th match to a state in which the first period Tv and the second period Th do not match, and the timing of the transition from a state in which the first period Tv and the second period Th do not match to a state in which the first period Tv and the second period Th match, it is possible to estimate the zero-crossing point of the coil current of a specified phase.

The current zero crossing point estimation unit 14 monitors the drive voltage Vu of the U-phase coil Lu acquired by the phase voltage input unit 13 and the PWM signal Suu of the U-phase high-side switch QuH, and for each period of the PWM signal Suu, compares a first period Tv during which the drive voltage Vu of the U-phase coil Lu is at a high level with a second period Th during which the PWM signal Suu of the U-phase high-side switch QuH is at a high level, and determines whether the first period Tv and the second period Th match.

As described above, the switching of the drive voltage Vu to a high level or a low level and the switching of the PWM signal Suu to a high level or a low level correspond to the on/off switching of the U-phase high-side switch QuH. Therefore, in the following description, the first period Tv in which the drive voltage Vu is at a high level may be referred to as the "on period Tv," and the second period Th in which the PWM signal Suu is at a high level may be referred to as the "on period Th."

Whether or not the on-period (first period) Tv and the on-period (second period) Th match may be determined as follows.
For example, the current zero-crossing point estimation unit 14 calculates the difference |Th-Tv| between the on-period Tv during which the drive voltage Vu of the U-phase coil Lu is at a high level and the on-period Th during which the PWM signal Suu of the U-phase high-side switch QuH is at a high level, and determines whether the difference |Th-Tv| is greater than or equal to a threshold value Tth.

When the difference |Th-Tv| is equal to or greater than the threshold value Tth, the current zero crossing point estimation unit 14 determines that the on-period Tv and the on-period Th do not match, and determines that the U-phase coil current Iu is negative. On the other hand, when the difference |Th-Tv| is less than the threshold value Tth, the current zero crossing point estimation unit 14 determines that the on-period Tv and the on-period Th match, and determines that the U-phase coil current Iu is positive.

Here, the threshold value Tth for determining whether the on-period Tv and the on-period Th match or not may be set based on the dead time period Td of the drive control signal Sd, which is a PWM signal. For example, Tth may be set to Td.

The current zero cross point estimation unit 14 detects at least one of the timing when the on-period Tv and the on-period Th switch from a state in which they coincide to a state in which they do not coincide, and the timing when the on-period Tv and the on-period Th switch from a state in which they do not coincide to a state in which they coincide, and estimates the detected timing as the zero cross point Q of the coil current Iu of the U phase.

Specifically, the current zero cross point estimation unit 14 determines the timing when the on-period (first period Tv) of the drive voltage Vu of the U-phase coil Lu and the on-period (second period Th) of the PWM signal of the U-phase high-side switch QuH switch from a matching state to a mismatched state as the zero cross point Q at which the polarity of the coil current Iu switches from positive to negative. The current zero cross point estimation unit 14 also determines the timing when the on-period Tv and the on-period Th switch from a mismatched state to a matching state as the zero cross point Q at which the polarity of the coil current Iu switches from negative to positive.

For example, the current zero-crossing point estimation unit 14 outputs to the phase adjustment determination unit 15 a zero-crossing point detection signal Sct that is at a high level when the on-period Tv and the on-period Th coincide (the coil current Iu is positive polarity) and is at a low level when the on-period Tv and the on-period Th do not coincide (the coil current Iu is negative polarity).

As a result, the phase adjustment determination unit 15 can detect the edge (rising edge or falling edge) of the zero-crossing point detection signal Sct to know the zero-crossing point Q of the coil current Iu. For example, the timing at which a falling edge at which the zero-crossing point detection signal Sct switches from high level to low level is detected is the zero-crossing point Q at which the coil current Iu switches from positive to negative polarity, and the timing at which a rising edge at which the zero-crossing point detection signal Sct switches from low level to high level is detected is the zero-crossing point Q at which the coil current Iu switches from negative to positive polarity.

In the present embodiment, as described above, the current zero cross point estimation unit 14 compares the on-period (first period) Tv in which the drive voltage Vu of the U-phase coil Lu is at a high level with the on-period (second period) Th in which the PWM signal Suu of the U-phase high-side switch QuH is at a high level to determine the zero cross point Q of the coil current Iu, but this is not limited to the above. For example, the current zero cross point estimation unit 14 may compare the off-period in which the drive voltage Vu of the U-phase coil Lu is at a low level with the off-period in which the PWM signal Suu of the U-phase high-side switch QuH is at a low level for each cycle of the PWM signal Suu, and determine whether the two off-periods match each other to determine the zero cross point Q of the coil current Iu.

The phase adjustment determination unit 15 determines whether or not phase adjustment of the coil current is necessary based on the phase difference Δφ between the zero-crossing target point P of the coil current Iu determined by the target point determination unit 12 and the zero-crossing point Q of the coil current Iu estimated by the current zero-crossing point estimation unit 14.

For example, as shown in FIG. 2, the phase adjustment determination unit 15 calculates the phase difference Δφ (= tp - tq) by subtracting the phase (time tq) of the zero cross point Q of the coil current Iu estimated by the current zero cross point estimation unit 14 from the phase (time tp) of the target point P (zero cross point of the induced voltage of the U-phase coil Lu) determined by the target point determination unit 12.

The phase adjustment determination unit 15 instructs the drive control signal generation unit 16 to shift the output timing of the drive control signal Sd by a time period corresponding to the phase difference Δφ (=tp−tq).
Specifically, when the phase difference Δφ is a positive (+) value, for example, when the phase difference Δφ is equal to or greater than +φth, the phase adjustment determination unit 15 determines that the phase of the coil current Iu leads the phase of the induced voltage of the U-phase coil Lu, and instructs the drive control signal generation unit 16 to perform advance control to delay the phase of the coil current Iu. For example, the phase adjustment determination unit 15 outputs a determination result S2 that instructs the execution of advance control to delay the coil current Iu by the phase difference Δφ.

When the phase difference Δφ is a negative (-) value, for example, when the phase difference Δφ is less than or equal to -φth, the phase adjustment determination unit 15 determines that the phase of the coil current Iu lags behind the phase of the induced voltage of the U-phase coil Lu, and instructs the drive control signal generation unit 16 to execute advance control to advance the phase of the coil current Iu. For example, the phase adjustment determination unit 15 outputs a determination result S2 that instructs the execution of advance control to advance the coil current Iu by the phase difference Δφ.

In addition, for example, when the phase difference Δφ is greater than -φth and less than +φth (-φth<Δφ<+φth), the phase adjustment determination unit 15 determines that the phase of the coil current Iu is approximately the same as the phase of the induced voltage of the U-phase coil Lu, and outputs a determination result S2 instructing that neither advance control nor retard control be performed.

The drive control signal generator 16 generates a drive control signal Sd based on the judgment result S2 of the phase adjustment judger 15 so as to reduce the difference between the zero cross point Q of the coil current Iu and the zero cross target point P. Specifically, the PWM command unit 17 generates a value that specifies the output timing of the PWM signal based on the judgment result S2 of the phase adjustment judger 15, and outputs it as an operation amount S3 together with the values of the PWM period and the on period of the PWM signal.

Here, the value that specifies the output timing of the PWM signal is a value that specifies the time shift (offset time) from the reference time for outputting the PWM signal as the drive control signal Sd.

For example, when the phase adjustment judgment unit 15 outputs a judgment result S2 instructing the execution of advance angle control to advance the angle by the phase difference Δφ, the PWM command unit 17 calculates a value "-Δtφ" instructing the output of a PWM signal earlier than the reference time by a time Δtφ corresponding to the phase difference Δφ, and sets this value as the output timing of the PWM signal.

For example, when the phase adjustment judgment unit 15 outputs a judgment result S2 instructing the execution of advance control to retard the angle by the phase difference Δφ, the PWM command unit 17 calculates a value "+Δtφ" instructing the output of the PWM signal later than the reference time by a time Δtφ corresponding to the phase difference Δφ, and sets this value as the output timing of the PWM signal.

Also, for example, if the phase adjustment determination unit 15 outputs a determination result S2 that does not instruct the execution of either advance angle control or retard angle control, the PWM command unit 17 sets the value specifying the output timing of the PWM signal to "0 (zero)."

When the PWM signal generating unit 18 outputs the drive control signal Sd, it changes the timing at which it outputs the drive control signal Sd based on a value that specifies the output timing of the PWM signal included in the operation amount S3. For example, a reference time for outputting the drive control signal Sd is set in advance, and the PWM signal generating unit 18 outputs the drive control signal Sd at a timing shifted from the reference time by the time specified by the value that specifies the output timing of the PWM signal.

For example, when the value specifying the output timing of the PWM signal is "+Δtφ", the PWM signal generating unit 18 outputs the drive control signal Sd generated based on the PWM cycle and on-period information included in the operation amount S3, delayed by Δtφ from the reference time.

For example, when the value specifying the output timing of the PWM signal is "-Δtφ", the PWM signal generating unit 18 outputs the drive control signal Sd generated based on the PWM cycle and on-period information included in the operation amount S3, Δtφ earlier than the reference time.

For example, when the value specifying the output timing of the PWM signal is "0 (zero)", the PWM signal generating unit 18 outputs the drive control signal Sd generated based on the PWM cycle and on-period information included in the operation amount S3 at the reference time without shifting the output timing. Note that not shifting the output timing means that if phase adjustment (advance angle, retard angle control) is being performed at that time, that phase adjustment is maintained.

Next, the flow of drive control of the motor 5 by the motor drive control device 1 according to this embodiment will be described.

Figure 5 is a flowchart showing the flow of the motor drive control process performed by the motor drive control device 1 according to the embodiment.

For example, when the DC voltage Vdd is applied to the motor drive control device 1 and the motor drive control device 1 starts up, the motor drive control device 1 first determines whether or not the drive command signal Sc has been input (step S1). If the drive command signal Sc has not been input (step S1: NO), the motor drive control device 1 waits until the drive command signal Sc is input.

When the drive command signal Sc is input (step S1: YES), the motor drive control device 1 starts drive control of the motor 5 (step S2). Specifically, the drive control signal generation unit 16 determines the PWM period and on-period based on the target rotation speed S1 of the motor 5 analyzed by the drive command analysis unit 11, generates six types of PWM signals Suu, etc. having the determined PWM period and on-period, and inputs them to the drive circuit 3 as drive control signals Sd. As a result, the drive circuit 3 switches the current direction of the coils Lu, Lv, and Lw of the motor 5 to rotate the motor 5.

Next, the motor drive control device 1 determines the target point P of the zero crossing of the U-phase coil current Iu (step S3). For example, as described above, the target point determination unit 12 determines the timing 30 electrical degrees ahead of the rising edge of the position detection signal Shu as the target point P (see FIG. 2).

Next, the motor drive control device 1 estimates the zero-crossing point of the U-phase coil current Iu (step S4).

Figure 6 is a flowchart showing the process (step S4) of estimating the zero-crossing point of the U-phase motor current Iu in Figure 5.

In step S4, the current zero-cross point estimation unit 14 first determines whether the duty ratio of the PWM signal Suu that drives the U-phase high-side switch QuH is 0% (step S41).

If the duty ratio of the PWM signal Suu is 0% (step S41: YES), the current zero cross point estimation unit 14 determines that the U-phase coil current Iu is negative (step S44). If the duty ratio of the PWM signal Suu is not 0% (step S41: NO), the current zero cross point estimation unit 14 calculates the difference |Th-Tv| between the on-period Tv during which the drive voltage Vu of the U-phase coil Lu is at a high level and the on-period Th during which the PWM signal Suu of the U-phase high-side switch QuH is at a high level, and determines whether the difference |Th-Tv| is equal to or greater than the threshold value Tth (step S42).

If the difference |Th-Tv| between the on-period Tv and the on-period Th is equal to or greater than the threshold value Tth (step S42: YES), the current zero crossing point estimation unit 14 determines that the on-period Tv and the on-period Th do not match, and determines that the U-phase coil current Iu is negative (step S44).

On the other hand, if the difference |Th-Tv| between the on-period Tv and the on-period Th is less than the threshold value Tth (step S42: NO), the current zero crossing point estimation unit 14 determines that the on-period Tv and the on-period Th match, and determines that the U-phase coil current Iu is positive (step S43).

After step S43 or step S44, the current zero cross point estimation unit 14 determines whether the polarity of the coil current Iu of the motor 5 has switched (step S45). For example, the current zero cross point estimation unit 14 determines whether the polarity of the coil current Iu determined in step S43 or step S44 differs from the polarity of the coil current Iu determined in the previous step S43 or step S44.

If the polarity of the coil current Iu has not switched (step S45: NO), i.e., if the polarity of the coil current Iu determined in step S43 or step S44 matches the polarity of the coil current Iu determined in the previous step S43 or step S44, the current zero cross point estimation unit 14 returns to step S41 and executes the processes from step S41 to S45 again.

On the other hand, if the polarity of the coil current Iu has switched (step S45: YES), that is, if the polarity of the coil current Iu determined in step S43 or step S44 does not match the polarity of the coil current Iu determined in the previous step S43 or step S44, the current zero cross point estimation unit 14 estimates the zero cross point Q of the U-phase coil current Iu (step S46). For example, the current zero cross point estimation unit 14 determines a point within the period (zero cross point existence range) Tz1 (or Tz2) between the time when step S43 or step S44 is executed and the time when the previous step S43 or step S44 is executed as the zero cross point Q of the U-phase coil current Iu (see FIG. 3A or FIG. 3B). This ends the processing of step S4.

As shown in FIG. 5, after step S4 is completed, the motor drive control device 1 adjusts the energization timing of the motor 5 (step S5).

Figure 7 is a flowchart showing the flow of the process (step S5) for adjusting the energization timing of motor 5 in Figure 5.

In step S5, the phase adjustment determination unit 15 first calculates the phase difference Δφ (= tp - tq) between the target point P determined in step S3 and the zero cross point Q of the U-phase coil current Iu estimated in step S4 (step S51).

Next, the phase adjustment determination unit 15 determines whether the phase difference Δφ calculated in step S51 is equal to or greater than +φth (step S52). If the phase difference Δφ is equal to or greater than +φth (step S52: YES), the phase adjustment determination unit 15 determines that the phase of the coil current Iu leads the phase of the induced voltage of the U-phase coil Lu, and instructs the drive control signal generation unit 16 to execute retard control to retard the phase of the coil current Iu (step S54). As a result, as described above, the drive control signal generation unit 16 outputs the drive control signal Sd at a timing delayed from the reference time by the time Δtφ corresponding to the phase difference Δφ.

On the other hand, in step S52, if the phase difference Δφ is less than +φth (step S52: NO), the phase adjustment determination unit 15 determines whether the phase difference Δφ is less than or equal to -φth (step S53). If the phase difference Δφ is less than or equal to -φth (step S53: YES), the phase adjustment determination unit 15 determines that the phase of the coil current Iu lags behind the phase of the induced voltage of the U-phase coil Lu, and instructs the drive control signal generation unit 16 to execute advance angle control to advance the phase of the coil current Iu (step S55). As a result, as described above, the drive control signal generation unit 16 outputs the drive control signal Sd at a timing earlier than the reference time by the time Δtφ corresponding to the phase difference Δφ.

On the other hand, in step S53, if the phase difference Δφ is greater than −φth (step S53: NO), the phase adjustment determination unit 15 determines that the zero cross point Q of the coil current Iu is within the target range of the target point P, and does not instruct the drive control signal generation unit 16 to adjust the phase of the coil current Iu (step S56). As a result, as described above, the drive control signal generation unit 16 outputs the drive control signal Sd at the reference time without shifting the output timing.
This completes the process in step S5.

As shown in FIG. 5, after step S5 is completed, the motor drive control device 1 returns to step S2 and repeats the processing of steps S2 to S6. This allows the motor 5 to continue rotating without a decrease in drive efficiency.

Figure 8 is a timing chart showing the changes in the voltage and coil current of each signal when the motor drive control device 1 according to the embodiment adjusts the phase of the coil current of the motor 5.

The figure shows the voltage and current states of the motor unit 100 when the motor drive control device 1 performs phase adjustment of the coil current Iu of the U phase of the motor 5.

In FIG. 8, from top to bottom, the waveforms of the position detection signal (Hall signal) Shu, the PWM signal Suu of the U-phase high-side switch QuH, the U-phase drive voltage Vu, the zero-crossing point detection signal Sct, and the U-phase coil current Iu are shown in that order. In FIG. 8, the horizontal axis represents time, and the vertical axis represents voltage or current.

As shown in FIG. 8, at time t1, a zero-cross point Q where the U-phase coil current Iu switches from negative to positive is detected, and it can be seen that the phase of the coil current Iu is adjusted so that the zero-cross point Q coincides with a target range (target point P of the zero-cross of the U-phase coil current Iu) that is 30 electrical degrees in phase from the rising edge of the position detection signal (Hall signal) Shu. This results in the induced voltage of the motor 5 and the coil current Iu being approximately in phase, making it possible to improve the driving efficiency of the motor 5.

As described above, the motor drive control device 1 according to this embodiment determines the zero-cross target point P of the coil current of a specified phase based on the position detection signal Shu synchronized with the induced voltage of the coil of a specified phase of the motor 5, compares the on-period (first period) Tv of the drive voltage of the coil of the specified phase with the on-period (second period) Th of the signal that turns on and off the high-side switch that drives the coil of the specified phase, and estimates the zero-cross point Q of the coil current of the specified phase based on the comparison result. The motor drive control device 1 determines whether or not phase adjustment of the coil current is necessary based on the phase difference Δφ (= tp - tq) between the estimated zero-cross point Q of the coil current of the specified phase and the zero-cross target point P, and generates a drive control signal Sd (PWM signal) for driving the motor 5 based on the determination result.

As described above, by arranging the position detection device 6 (Hall element) at a position corresponding to the coil of a specified phase of the motor 5, it is possible to obtain a position detection signal Shu synchronized with the induced voltage of the coil of the specified phase. Then, if the phase difference between the position detection signal Shu and the induced voltage is known, it is possible to determine the zero cross point of the induced voltage, i.e., the target point P of the zero cross of the coil current of a specified phase of the motor 5, based on the rising edge or falling edge of the position detection signal Shu.

Furthermore, as described above, during the period when the coil current of a specified phase (e.g., U phase) of the motor 5 is positive (+) polarity, the on-period Tv and the on-period Th match, and during the period when the coil current is negative (-) polarity, the on-period Tv and the on-period Th do not match. Therefore, by comparing the on-period Tv and the on-period Th, it is possible to detect the zero-crossing point where the coil current switches from positive polarity to negative polarity or the zero-crossing point where the coil current switches from negative polarity to positive polarity.

Specifically, the motor drive control device 1 determines whether the on-period Tv and the on-period Th coincide with each other, and detects at least one of the timing when the on-period Tv and the on-period Th switch from a coincident state to a non-coincident state and the timing when the on-period Tv and the on-period Th switch from a non-coincident state to a coincident state, and estimates the detected timing as the zero-crossing point of the coil current of a specified phase.
This makes it possible to easily estimate the zero crossing point of the coil current without directly monitoring the coil current of the motor 5.

The motor drive control device 1 can reduce the phase difference between the phase of the induced voltage of a coil of a specified phase of the motor and the phase of the coil current by performing phase adjustment according to the phase difference Δφ between the zero-cross target point P of the coil current of a specified phase and the zero-cross point Q of the coil current of a specified phase.

As described above, the motor drive control device 1 according to this embodiment makes it possible to improve the drive efficiency of the motor.

The motor drive control device 1 also determines that the on-period Tv and the on-period Th match when the difference |Th-Tv| between the on-period Tv and the on-period Th is less than the threshold value Tth, and determines that the on-period Tv and the on-period Th do not match when the difference |Th-Tv| between the on-period Tv and the on-period Th is equal to or greater than the threshold value Tth.

As a result, even if the on-period Tv and the on-period Th are theoretically equal to each other, and various factors, such as the parasitic diode of a transistor serving as a high-side switch, cause the on-period Tv and the on-period Th to not completely match, it is possible to accurately determine whether the on-period Tv and the on-period Th match or not.

The motor drive control device 1 also generates a drive control signal Sd so that when the high-side switch and the low-side switch are switched between on and off states, a dead time period Td is formed during which the high-side switch and the low-side switch are simultaneously turned off. The threshold value Tth for determining whether the on-period Tv and the on-period Th match or not is a value based on the dead time period Td.

As shown in Figures 3A and 3B, when the on-period Tv and the on-period Th do not match, theoretically the on-period Tv is longer than the on-period Th by twice the dead-time period Td. In other words, since the difference between the on-period Tv and the on-period Th is based on the dead-time period Td, for example, by setting Tth = Td, the accuracy of determining whether the on-period Tv and the on-period Th match or not can be further improved.

In addition, the motor drive control device 1 determines the timing when the on-period Tv and the on-period Th switch from a state in which they coincide to a state in which they do not coincide to be the zero-crossing point where the polarity of the coil current switches from positive to negative, and determines the timing when the on-period Tv and the on-period Th switch from a state in which they do not coincide to a state in which they coincide to be the zero-crossing point where the polarity of the coil current switches from negative to positive.
This makes it possible to easily distinguish and detect the zero-crossing points where the polarity of the coil current switches from positive to negative and the zero-crossing points where the polarity of the coil current switches from negative to positive.

The motor drive control device 1 also calculates the phase difference Δφ (= tp - tq) between the zero-cross target point P of the coil current of a specified phase and the zero-cross point Q of the coil current, and shifts the output timing of the drive control signal Sd by a time Δtφ (= tp - tq) that corresponds to the phase difference Δφ.

This adjusts the phase of the coil current (coil drive voltage) by an amount corresponding to the phase difference Δφ between the zero-cross target point P of the coil current of a specified phase and the zero-cross point Q of the coil current, i.e., the amount of deviation between the phase of the induced voltage and the phase of the coil current, making it possible to more reliably bring the phase of the coil current closer to the phase of the induced voltage. In other words, compared to the conventional technology of Patent Document 1 mentioned above, which performs advance or delay angle control without accurately detecting the zero-cross point of the coil current, more precise phase adjustment is possible, making it possible to further improve the drive efficiency of the motor.

<<Extension of the embodiment>>
The invention made by the present inventors has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

For example, in the above embodiment, the position detector 6 is arranged for the coil of the U phase among the three phases (U phase, V phase, and W phase) of the motor 5, and the zero cross point of the drive voltage Vu and the coil current Iu of the U phase is detected. However, this is not limited to this, and the position detector 6 may be arranged for the coil Lv of the V phase to detect the zero cross point of the drive voltage Vv and the coil current Iv of the V phase to adjust the phase of the coil current Iv, or the position detector 6 may be arranged for the coil Lw of the W phase to detect the zero cross point of the drive voltage Vw and the coil current Iw of the W phase to adjust the phase of the coil current Iw. In addition, the position detector 6 may be arranged for two or all of the U, V, and W phases to detect the zero cross point of the drive voltage and the coil current of any of the phases and adjust the phase of the coil current of the detected phase.

In the above embodiment, the current zero cross point estimation unit 14 detects both the timing at which the on-period (first period Tv) of the drive voltage Vu of the coil Lu and the on-period (second period Th) of the PWM signal of the U-phase high-side switch switch from a matching state to a non-matching state (zero cross point Q at which the coil current Iu switches from positive to negative) and the timing at which the on-period Tv and the on-period Th switch from a non-matching state to a matching state (zero cross point Q at which the coil current Iu switches from negative to positive), but it may detect either one of the zero cross points Q. For example, the current zero cross point estimation unit 14 may detect only the zero cross point Q at which the coil current Iu switches from negative to positive.

In the above embodiment, the type of motor 5 is not limited to a brushless DC motor. Also, the motor 5 is not limited to a three-phase motor, and may be, for example, a single-phase brushless DC motor.

In the above embodiment, a Hall element is used as the position detection device 6, but this is not limiting. For example, a Hall IC, an encoder, a resolver, etc. may be provided as the position detection device 6, and the detection signal from these may be input to the motor drive control device 1 as the position detection signal Shu.

The above-mentioned flowcharts are merely examples and are not limiting. For example, other processes may be inserted between each step, or the processes may be parallelized.

1...motor drive control device, 2...control circuit, 3...drive circuit, 4...phase voltage detection circuit, 5...motor, 6...position detection device, 11...drive command analysis unit, 12...target point determination unit, 13...phase voltage input unit, 14...current zero cross point estimation unit, 15...phase adjustment judgment unit, 16...drive control signal generation unit, 17...PWM command unit, 18...PWM signal generation unit, 100...motor unit, 200...waveform of position detection signal Shu, 201...waveform of drive voltage Vu of U-phase coil Lu, 202...waveform of induced voltage of U-phase coil Lu, 203...waveform of coil current Iu of U-phase coil Lu, Lu, Lv, Lw...coil, Iu...U-phase coil current, S1...target rotation speed, S2...judgment result, S3...operation amount, Sc... Drive command signal, Sct...zero-cross point detection signal, Shu...position detection signal, Sd...drive control signal, Suu, Sul, Svu, Svl, Swu, Swl...PWM signal, Tv...on period (first period) of drive voltage Vu of coil Lu, Th...on period (second period) of PWM signal Suu, Td...dead time period, QuH, QvH, QwH...high-side switch, QuL, QvL, QwL...low-side switch, Δφ...phase difference, +φth, -φth...threshold, Tth...threshold, Vu...drive voltage of coil Lu, Vv...drive voltage of coil Lv, Vw...drive voltage of coil Lw, Vdd DC voltage, P...target point of zero cross of coil current Iu, Q...zero cross point of coil current Iu.

Claims (7)

A control circuit that generates a drive control signal, which is a PWM signal for driving a motor having at least one phase coil;
a drive circuit including a high-side switch and a low-side switch connected in series to each other and provided corresponding to a coil of each phase of the motor, and alternately turning on and off the high-side switch and the low-side switch in response to the drive control signal to switch a current direction of the coil of the corresponding phase;
The control circuit includes:
a target point determination unit that is synchronized with an induced voltage in a coil of a predetermined phase of the motor and determines a target point of a zero cross of a coil current of the predetermined phase based on a position detection signal corresponding to a rotational position of a rotor of the motor;
a current zero-cross point estimating unit that compares, for each cycle of the PWM signal, a drive voltage of a coil of the predetermined phase with at least one of an on period and an off period of a signal that turns on and off the high-side switch corresponding to the predetermined phase, and estimates a zero-cross point of a coil current of the predetermined phase based on a result of the comparison;
a phase adjustment determination unit that determines whether or not a phase adjustment of the coil current is required based on a phase difference between the target point determined by the target point determination unit and the zero cross point estimated by the current zero cross point estimation unit;
a drive control signal generation unit that generates the drive control signal based on a result of the determination by the phase adjustment determination unit ,
The current zero-cross point estimating unit determines whether or not an on-period of the drive voltage coincides with an on-period of a signal that turns on and off the high-side switch, and detects at least one of a timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch change from a coincident state to a non-coincident state and a timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch change from a non-coincident state to a coincident state, and estimates the detected timing as a zero-cross point of a coil current of the specified phase.
Motor drive control device. 2. The motor drive control device according to claim 1 ,
the current zero cross point estimator determines that the on period of the drive voltage and the on period of the signal that turns the high-side switch on and off match when a difference between the on period of the drive voltage and the on period of the signal that turns the high-side switch on and off is less than a threshold, and determines that the on period of the drive voltage and the on period of the signal that turns the high-side switch on and off do not match when a difference between the on period of the drive voltage and the on period of the signal that turns the high-side switch on and off is equal to or greater than the threshold. 3. The motor drive control device according to claim 2 ,
the drive control signal generation unit generates the drive control signal so that, when the on/off states of the high-side switch and the low-side switch are switched, a dead time period in which the high-side switch and the low-side switch are simultaneously turned off is formed;
The motor drive control device, wherein the threshold value is a value based on the dead time period. The motor drive control device according to any one of claims 1 to 3 ,
the current zero-cross point estimation unit determines a timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch change from a state in which they coincide to a state in which they do not coincide to be a zero-cross point at which the polarity of the coil current changes from positive to negative, and determines a timing at which the on-period of the drive voltage and the on-period of the signal that turns on and off the high-side switch change from a state in which they do not coincide to a state in which they coincide to be a zero-cross point at which the polarity of the coil current changes from negative to positive;
Motor drive control device. The motor drive control device according to any one of claims 1 to 4 ,
The phase adjustment determination unit calculates a phase difference between the target point and a zero cross point of the coil current, and instructs the drive control signal generation unit to shift an output timing of the drive control signal by a time corresponding to the phase difference. A motor drive control device according to any one of claims 1 to 5 ,
A motor unit comprising the motor. A motor control method using a motor drive control device including: a control circuit that generates a drive control signal, which is a PWM signal for driving a motor having a coil of at least one phase; and a drive circuit that includes a high-side switch and a low-side switch that are connected in series to each other and are provided corresponding to the coil of each phase of the motor, and that alternately turns on and off the high-side switch and the low-side switch in response to the drive control signal to switch a current flow direction of the coil of the corresponding phase,
a first step in which the control circuit determines a zero-cross target point of a coil current of a predetermined phase of the motor based on a position detection signal that is synchronized with an induced voltage of the coil of the predetermined phase of the motor and corresponds to a rotational position of a rotor of the motor;
a second step in which the control circuit compares, for each cycle of the PWM signal, a drive voltage of a coil of the predetermined phase with at least one of an on period and an off period of a signal that turns on and off the high-side switch corresponding to the predetermined phase, and estimates a zero-cross point of a coil current of the predetermined phase based on a result of the comparison;
a third step in which the control circuit determines whether or not a phase adjustment of the coil current is required based on a phase difference between the target point determined in the first step and the zero cross point estimated in the second step;
a fourth step of the control circuit generating the drive control signal based on a result of the determination in the third step ;
The second step comprises:
a step of the control circuit determining whether an on-period of the drive voltage coincides with an on-period of a signal that turns on and off the high-side switch;
detecting at least one of a timing at which the on-period of the drive voltage and an on-period of a signal that turns on and off the high-side switch change from a state in which they coincide to a state in which they do not coincide, and a timing at which the on-period of the drive voltage and an on-period of a signal that turns on and off the high-side switch change from a state in which they do not coincide to a state in which they coincide, and estimating the detected timing as a zero-cross point of a coil current of the predetermined phase.
A motor drive control method.

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