Motor drive device and motor drive control method

Abstract

The invention provides a motor drive device and a motor drive control method, in the motor drive device, the phase switching timing of a magnetic signal is reliably detected, the switching noise is not generated, the bias current in an unnecessary period is reduced, and the power consumption is suppressed. A motor drive device (1) for driving a brushless DC motor is provided with: a motor drive unit (3) for driving a motor (5); a magnetic sensor (6) that detects a magnetic field generated by rotation of the motor and outputs the magnetic field as magnetic signals (IN1, IN2); and a bias adjustment unit (4) for adjusting and outputting a bias voltage used when the magnetic sensor detects the magnetic field, the bias adjustment unit adjusting the bias voltage to a second voltage value (VHB / a) lower than a first voltage value, which is a value at which the magnetic sensor can detect the magnetic field, during a first period after phase switching of the magnetic signals (IN1, IN2). The bias voltage is adjusted to the first voltage value (VHB) during a second period from the elapse of the first period to the next phase switching of the magnetic signal.

Description

Technical Field

[0001] The invention relates to a motor driving device and a motor driving control method. Background Art

[0002] In order to rotate a brushless DC motor (BLDC), it is necessary to detect the movement and change of the magnetic field generated by the magnets installed on the rotor as the rotor rotates. Hall sensors are used in this magnetic field detection. In addition, in order to generate a magnetic field detection signal from the Hall sensor, a predetermined voltage needs to be biased to the Hall sensor.

[0003] However, if the bias voltage is unstable, the magnetic field detection signal is also directly affected and becomes unstable, so the bias voltage supplied to the Hall element is generated by a stabilized voltage source (regulator). In particular, the power consumption of the regulator part becomes the main cause of the temperature rise of the device, which may become a restriction on the use conditions.

[0004] Therefore, for example, Patent Document 1 discloses control for intermittently operating a Hall element.

[0005] However, in the above-mentioned patent document 1, if the actual phase switching of the Hall element occurs at a timing without bias in order to make the Hall element intermittently operate, the timing of the actual phase switching cannot be accurately detected. In this technology, in order to prevent the situation where detection cannot be made, a correction circuit is proposed, but since the prediction and correction are made based on the rotation signal cycle, it is also possible that the detection of reliable and accurate phase switching timing cannot be compensated. In addition, the switching noise during the intermittent operation of the Hall element may also be superimposed on the magnetic signal.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-111912 Summary of the invention

[0007] Therefore, in view of the above situation, an object of the present invention is to provide a motor drive device that can reliably detect the phase switching timing of a magnetic signal without generating switching noise, reduce the bias current during an unnecessary period, and suppress power consumption.

[0008] In order to solve the above-mentioned problems, a motor driving device for driving a brushless DC motor according to one embodiment of the present invention includes:

[0009] a motor driving unit that drives the motor;

[0010] a magnetic sensor that detects a magnetic field generated by the rotation of the motor and outputs the magnetic signal; and

[0011] a bias adjustment unit that adjusts and outputs a bias voltage used when the magnetic sensor detects a magnetic field,

[0012] In a first period after the phase switch of the magnetic signal, the bias adjustment unit adjusts the bias voltage to a second voltage value lower than a first voltage value, which is a value at which the magnetic sensor can detect the magnetic field, and in a second period from after the first period to the next phase switch of the magnetic signal, the bias adjustment unit adjusts the bias voltage to the first voltage value.

[0013] According to one embodiment, in a motor drive control circuit that rotates a brushless DC motor, phase switching timing of a magnetic signal is reliably detected without generating switching noise, thereby reducing bias current in an unnecessary period and suppressing power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing the structure of a motor drive device according to one embodiment of the present invention.

[0015] Figure 2 It is a diagram for explaining the signal operation during steady rotation in the motor drive device of the comparative example.

[0016] Figure 3 This is a functional block diagram of an offset adjustment unit according to an embodiment.

[0017] Figure 4 4 is a circuit diagram of a Hall bias output unit according to an embodiment.

[0018] Figure 5 This is a diagram for explaining the signal operation during stable rotation in the motor drive device of the present invention.

[0019] Figure 6 It is an overall flow chart of the bias control of the present invention.

[0020] Figure 7 This is a detailed flow chart of the determination of whether bias control is performed in the present invention. DETAILED DESCRIPTION

[0021] Hereinafter, the embodiments will be described with reference to the drawings. In each of the drawings, the same components are denoted by the same reference numerals, and overlapping descriptions may be omitted.

[0022] First, refer to Figure 1 , Figure 2 The structure of a motor drive device according to one embodiment of the present invention will be described. Figure 1 It is a diagram showing the structure of a motor drive device according to one embodiment of the present invention.

[0023] The motor driving device 1 is incorporated in a fan motor for cooling a heat generating component such as a processor in an electronic device such as a notebook personal computer. The motor driven by the motor driving device 1 is a brushless DC (direct current) motor (BLDC) having a Hall sensor as a rotor position detection element.

[0024] The motor drive device 1 is, for example, a circuit for driving a single-phase motor 5 for rotating a cooling fan, and includes a drive control device 10, a single-phase motor 5, and a Hall element 6. The drive control device 10 is configured to include a control circuit 2, an H-bridge circuit 3, and a bias adjustment unit 4. The control circuit 2 and the bias adjustment unit 4 may also include terminals to form a control IC as a semiconductor integrated circuit that controls the motor drive unit.

[0025] In the drive control device 10, the control circuit 2 includes a position detection signal generating unit 21, an output control unit 22, and a gate driver 23. In addition, in the control circuit 2, circuits such as a PWM signal generating unit and a soft switching period generating unit may be provided. In addition, the Hall element 6 inputs the Hall signals IN1 and IN2 to the control circuit 2.

[0026] The H-bridge circuit 3 is a motor driving unit and is composed of P-channel FETs M1 and M2 and N-channel FETs M3 and M4. The P-channel FET M1 is used as a first upper switch, the N-channel FET M4 is used as a first lower switch, the P-channel FET M2 is used as a second upper switch, and the N-channel FET M3 is used as a second lower switch.

[0027] The rotor of the single-phase motor 5 has magnets with N poles and S poles, and on the other hand, the Hall element 6 is fixed to be able to detect the magnetic field of the magnet of the rotor. The Hall element 6, which is a magnetic sensor, outputs Hall signals IN1 and IN2 of a voltage level corresponding to the intensity of the detected magnetic field to the terminal. As the rotor rotates, the magnet also rotates, and the Hall element 6 detects the change in the magnetic field accompanying the rotation of the magnet, thereby detecting the position of the rotor. In addition, the Hall signals IN1 and IN2 of this embodiment are, for example, sinusoidal signals with an amplitude of a predetermined voltage level, and are output to the terminals of the control IC of the drive control device 10. In addition, the Hall signals IN1 and IN2 are not limited to sinusoidal waves.

[0028] The bias adjustment unit 4 adjusts the level of the bias current applied to operate the Hall element 6. The bias adjustment unit 4 includes an oscillator 41, a timer 42, a rotation stability determination unit 43, a control signal generation unit 44, and a Hall bias output unit 45.

[0029] In the control circuit 2 , the position detection signal generating unit 21 compares the levels of the Hall signals IN1 and IN2 , and generates an FG signal (Frequency Generation) (position detection signal) whose frequency changes according to the rotation speed of the single-phase motor 5 .

[0030] The position detection signal generating unit 21 generates an FG signal which becomes a high level (hereinafter referred to as an "H" level) when the level of the Hall signal IN1 is higher than the level of the Hall signal IN2, and becomes a low level (hereinafter referred to as an "L" level) when the level of the Hall signal IN1 is lower than the level of the Hall signal IN2. However, the position detection signal generating unit 21 implements the switching operation of the FG signal based on the output of the bias adjusting unit 4 only during the period when the Hall element 6 outputs the Hall signal.

[0031] The output control unit 22 generates signals for switching the FETs M1 , M2 , M3 , and M4 of the H-bridge circuit 3 , respectively, and outputs the signals to the gate driver 23 .

[0032] The gate driver 23 controls each MOSFET of the H-bridge circuit 3 to change the drive current Idr that drives the motor coil L of the single-phase motor 5. Specifically, the gate driver 23 outputs a gate control voltage for turning on and off the gates of the FETs M1, M2, M3, and M4 of the H-bridge circuit 3, respectively.

[0033] The bias adjustment unit 4 is a circuit for adjusting, at appropriate timing, the intensity of an electric field applied to cause the Hall element 6 to output a Hall signal as a magnetic field detection signal, that is, a bias voltage.

[0034] <Comparative Example>

[0035] Here, use Figure 2 The behavior of a general Hall bias when the bias adjustment unit 4 is not provided will be described. Figure 2 It is a diagram for explaining the signal operation during steady rotation in the motor drive control device of the comparative example.

[0036] Conventionally, a bias voltage at a level capable of outputting a Hall signal is always applied to the Hall element regardless of the states of the Hall signals IN1 and IN2.

[0037] As an example, when a bias voltage is applied to the Hall element, the bias voltage is 1.0 to 1.3 V, and when the impedance of the Hall sensor is 200 to 500 Ω, the bias current is 2 to 7 mA.

[0038] For example, when the power supply is 24V, the regulator output voltage is 1.3V, and the bias current is 5mA, the Hall sensor consumes 1.3V×5mA=6.5mW of power, and the regulator output consumes (24V~1.3V)×5mA=113.5mW of power.

[0039] In addition, if the bias voltage is unstable, the magnetic field detection signal is also directly affected and becomes unstable, so the bias of the Hall is performed by a stabilized voltage source (regulator). In particular, the power consumption of the regulator becomes the main cause of the temperature rise of the device, which may become a restriction on the use conditions.

[0040] However, in order to rotate the BLDC motor, it is sufficient to know the timing of phase switching (= switching of magnetic fields N, S), and there is no need to stably flow the bias current. In detail, if the FG signal, which is the position detection signal of the subsequent stage, reaches the point where the Hall signals IN1 and IN2 become the same potential, the output is reversed, and the timing of the output switching of the FG signal is used in the control of the subsequent stage. In addition to the timing of the output switching of the FG signal, that is, as long as the timing of the Hall signals IN1 and IN2 becoming the same potential is known, there is no need to apply a bias current of a level that can output the Hall signal during other periods.

[0041] Therefore, in the present invention, by providing the offset adjustment unit 4, the offset voltage is significantly reduced in a period other than the timing required for control, that is, other than the predetermined period immediately before the phase of the FG signal is switched.

[0042] (Bias adjustment section)

[0043] Here, use Figure 3 The offset adjustment unit 4 and the position detection signal generation unit 21 will be described in detail. Figure 3 It is a functional block diagram of the offset adjustment unit 4 and the position detection signal generation unit 21 .

[0044] As described above, the offset adjustment unit 4 includes the oscillator 41 , the timer 42 , the rotation stability determination unit 43 , the control signal generation unit 44 , and the hall offset output unit 45 .

[0045] In more detail, the timer 42 includes a half-cycle timer 421 and an intra-cycle counter 422. The half-cycle timer 421 is a first measuring unit that measures the variation period T of the magnetic field that is substantially equal to the rotation period of the rotor of the motor 5, that is, the length of the half cycle of the FG signal, that is, the half cycle length. A clock is input from the oscillator 41 to the half-cycle timer 421, and the operation is performed stably.

[0046] The intra-cycle counter 422 is a second measuring unit, and counts the elapsed time in the current half cycle of the FG signal. Then, the intra-cycle counter 422 sets the first period in the current half cycle according to the product of the half cycle length of the previous half cycle measured by the half cycle timer 421 and a predetermined value less than 1, and performs the measurement.

[0047] The rotation stability determination unit 43 includes a period comparison unit 431 , a register 432 , a stability determination counter 433 , and a stability determination unit 434 .

[0048] The register 432 stores the half cycle length of the previous half cycle, and stores only the first specified value. The register 432 stores the half cycle length T as a measurement result, that is, rewrites the register value, every time the output logic of the FG signal is inverted.

[0049] The cycle comparison unit 431 compares the current half cycle length measured by the half cycle timer 421 with the value of the previous half cycle length or the first predetermined value stored in the register 432. When the cycle lengths of the previous half cycle and the current half cycle vary greatly, the cycle comparison unit 431 causes the stability determination unit 434 to determine that the control is the non-bias output control, and causes the control signal generation unit 44 to output L.

[0050] The stability determination counter 433 digitizes the degree of stabilization and counts. Specifically, the stability determination counter 433 counts each time the change rate of the current half cycle length relative to the previous half cycle length is less than a predetermined value (d%). The predetermined value of the change rate is, for example, about 5 to 10%.

[0051] When the value of the stability determination counter 433 is greater than the predetermined value, the stability determination unit 434 determines that the bias output control is in effect because the change in the half-cycle length is small, and causes the control signal generation unit 44 to output H. Specifically, when the change rate of the current half-cycle length relative to the previous half-cycle length is less than the predetermined value for more than a predetermined number of times (M times), the stability determination unit 434 performs control to make the bias voltage lower than the value capable of detecting the magnetic field during the first period. The predetermined number of times (M times) is, for example, 2 to 8 times.

[0052] The control signal generating unit 44 sets the control signal for controlling the bias voltage to H and outputs it only when there is control, based on the determination of the rotation stability determining unit 43. At this time, the control signal generating unit 44 takes the phase switching of the FG signal as a starting point, and outputs the control signal for controlling the bias voltage in the first period of the current half cycle measured by the intra-cycle counter 422 in the control state.

[0053] In the control signal generating unit 44, the period during which the control signal is outputted in H (control state), i.e., the first period, is a period shorter than the length of the previous half cycle, i.e., the period other than the length of the previous half cycle × the predetermined ratio (1 / N), i.e., the product of "the length of the previous half cycle" and <predetermined value less than 1> (T×(N-1) / N). In addition, the predetermined ratio (1 / N) in the half cycle is, for example, 1 / 4 to 1 / 10, and the above-mentioned predetermined value less than 1 is 3 / 4 to 9 / 10.

[0054] On the other hand, in the control signal generating unit 44, the second period as a period for outputting the control signal at L is a remaining period from the first period to the next phase switching of the FG signal (Hall signal) in the current half cycle.

[0055] The Hall bias output unit 45 controls the bias voltage to be lower than the value at which the Hall element 6 can detect the magnetic field and outputs it during the period when the control signal is output at H (control state), and outputs the bias voltage at the value at which the Hall element 6 can detect the magnetic field during the period when the control signal is output at L (non-control state). Specifically, the Hall bias output unit 45 outputs the bias voltage at the second voltage value lower than the first voltage value during the first period when the control signal is output at H, and outputs the bias voltage at the first voltage value at which the magnetic field can be detected during the second period when the control signal is output at L.

[0056] Thus, in the second period before the next phase switch of the FG signal (Hall signal), the bias voltage is adjusted to a first voltage value that enables magnetic field detection, thereby enabling the detection of the phase switch timing of the Hall signal without missing it. Figure 5 to Figure 7 The details of the control of the offset adjustment unit 4 will be described together.

[0057] On the other hand, the position detection signal generating unit 21 includes a Hall comparator 211 and a latch unit 212. When the control signal is L and an electric field capable of detecting a magnetic field is applied to the Hall element 6, the Hall comparator 211 generates an FG signal that becomes an H level when the level of the Hall signal IN1 is higher than the level of the Hall signal IN2, and becomes an L level when the level of the Hall signal IN1 is lower than the level of the Hall signal IN2. The latch unit 212 latches the state of the FG signal while the control signal is H, and releases the latch of the FG signal when the control signal becomes L.

[0058] (Structure of Hall bias output section)

[0059] Figure 44 is a circuit diagram of the Hall bias output unit 45. The Hall bias output unit 45 has a voltage control unit 451 and an output unit 452. The voltage control unit 451 includes a constant current source 453, P-channel FETs M5 and M6, and resistors R1 and R2. The constant current source 453 is, for example, a regulator with a stable output. The P-channel FET M5 as an input switch is connected between the two resistors R1 and R2.

[0060] The output section 452 includes a P-channel FET M7 connected to the power source Vcc2. The P-channel FET M7 is a FET for reverse connection protection.

[0061] When the control signal is L, the P-channel FET M5 as the input switch is turned off, so the current Ir generated by the constant current source is connected to the ground via the resistor R2 having a resistance value <R / a> and the resistor R2 having a resistance value <R×(a-1) / a>, thereby generating a voltage. Therefore, when the control signal is L, the output unit 452 outputs a bias voltage of the current Ir×R generated by the constant current source.

[0062] When the control signal is H, the input switch M5 is turned on, so the current Ir generated by the constant current source 453 is grounded via the resistor R2 having a resistance value <R / a>, thereby generating a voltage. Therefore, when the control signal is H, the output unit 452 outputs a bias voltage of the current Ir×R / a generated by the constant current source.

[0063] That is, when the control signal is L (not in control state), the input switch M5 is turned off, and the bias voltage is generated by multiplying the current generated by the constant current source by the resistance value of the two resistors. On the other hand, when the control signal is H (in control state), the input switch M5 is turned on, and the bias voltage is generated by multiplying the current generated by the constant current source by the resistance value of one of the two resistors.

[0064] Thus, the bias voltage value (Ir×R / a) when the control signal is H becomes 1 / a of the bias voltage value (Ir×R) when the control signal is L, and the bias voltage value and the power consumption associated with the bias voltage are reduced by Ir×R×{(a-1) / a} compared to when the bias voltage value is (Ir×R / a). For example, the bias voltage 1 / a set low is preferably 1 / 10 to 1 / 50, and therefore, the resistance value of the resistor R1 is set to be << the resistance value of the resistor R2.

[0065] (Bias control example in steady state)

[0066] Next, use Figure 5 , Figure 6 The signal operation when bias control is performed during steady rotation will be described. Figure 5 This is a diagram for explaining the signal operation during stable rotation in the motor drive control device of the present invention. Figure 6 It is an overall flow chart of the bias control of the present invention.

[0067] In a state without bias control before entering a stable state, as a startup operation that becomes a prerequisite, in S101, the Hall bias output unit 45 is started, and as a bias voltage, a voltage value that enables the Hall element 6 to detect a magnetic field, that is, a first voltage value (VHB) is output. Then, a clock is generated in the oscillator 41, and the half-cycle timer 421 always counts the half-cycle length that is the length of the half cycle of the FG signal.

[0068] In this state, when the Hall signals IN1 and IN2 reach a point where they have the same potential due to the rotation of the motor (change in the magnetic field) in step S102, the cycle starts, and the flow from S103 onwards begins.

[0069] In S102, the Hall signals become the same potential, and the polarity of the output of the FG signal as the position detection signal is reversed in S103. Immediately after the output polarity of the FG signal is reversed, the latch unit 212 latches the state of the FG signal. In addition, upon receiving the inversion of the output polarity of the FG signal, the half-cycle timer 421 for counting the half cycle completes the measurement of the length of the half cycle of the FG signal up to that time point (the previous half-cycle length T).

[0070] In step S104, the half-cycle timer 421 is reset and the half-cycle length of the FG signal of the current cycle is measured. At the same time, the half-cycle length of the FG signal measured in step S103 is taken in as the length of the half-cycle (half-cycle length) T by the intra-cycle counter 422, and the intra-cycle counter 422 as the second measuring unit starts counting the first period up to the half-cycle length T×(N-1) in the half-cycle.

[0071] Then, in S105, it is determined whether the output control of the Hall bias is performed. The FG signal inversion in S103 is received, and S104 and S105 are executed in parallel. Figure 7 Let’s elaborate together.

[0072] Then, when it is determined in S105 that the Hall bias output control is necessary, the control signal becomes H in S106.

[0073] also, Figure 6 S102, S103, S104, S105, S106 are almost in the same time Figure 5 t1 is executed.

[0074] On the other hand, when it is determined in S105 that the Hall bias output control is not necessary, in S107 the control signal is kept at L, and the operations of S108 to S111 are not performed.

[0075] In response to the switching of the control signal in S106, in S108, the Hall bias output unit 45 attenuates the Hall bias output voltage to the second voltage value (VHB / a). In conjunction with this, due to the insufficient magnetic field, the Hall element 6 becomes unable to detect the magnetic field, and the Hall signal stops being output (S108 is Figure 5 t2 execution).

[0076] In S109, if the count value in the counter 422 reaches T×(N-1) within the period, it is considered that the first period is completed, and the Hall bias control signal becomes L in S110. (S109, S110 are Figure 5 t3 execution).

[0077] The Hall bias is controlled to L, and in S111, the Hall bias output unit 45 outputs a first voltage value (VHB) which is a normal Hall bias voltage value. This enables the detection of a magnetic field, and the Hall element 6 is capable of detecting a Hall signal (detection state).

[0078] The first voltage value (VHB) is outputted in S111, and the latched state of the FG signal is released in S112. (S111 and S112 are Figure 5 t4 execution).

[0079] Then, return to S102 ( Figure 5 At t5), when the Hall signals IN1 and IN2 reach a point where they have the same potential due to the rotation of the motor (change in the magnetic field), the half cycle ends, and the second period in the half cycle ends.

[0080] At the same time, in S102( Figure 5 In t5), the timing when the Hall signals IN1 and IN2 reach the point of having the same potential due to the rotation of the motor (change in the magnetic field) becomes the starting point of the next half cycle, and then the above-mentioned control of S102 to S112 is repeated.

[0081] Specifically, in the next cycle of Tb, S102, S103, S104, S105, and S106 are executed at t5, S108 is executed at t6, S109 and S110 are executed at t7, and S111 and S112 are executed at t8. In the next cycle of Tc, control is repeatedly performed in such a manner that S102, S103, S104, S105, and S106 are executed at t9, S108 is executed at t10, S109 and S110 are executed at t11, and S111 and S112 are executed at t12.

[0082] In addition, due to external factors, the rotation speed of the single-phase motor 5 changes slightly, so the half-cycle lengths of the half-cycles Ta, Tb, and Tc of the FG signal also change slightly. The bias voltage control period, that is, the first period, which controls the output of the bias voltage to be low, is calculated based on the half-cycle length of the previous half cycle. Therefore, in the case where the half-cycle length of the previous half cycle is long and the half cycle of this time is short, as in the cycle Tb, the proportion of the first period in the half cycle becomes longer. On the other hand, in the case where the previous half cycle is short and the half cycle of this time is long, as in the cycle Tc, the proportion of the first period in the half cycle becomes shorter.

[0083] Thus, in the present invention, during the first period (period of (N-1) / N) from just after the phase switching of the Hall signal is detected to just before the next phase switching, the second voltage value (VHB / a) obtained by controlling the bias voltage to be lower than the value at which the Hall element can detect the magnetic field is output. On the other hand, during the second period other than the first period, the bias voltage set to the value at which the magnetic field can be detected, i.e., the first voltage value (VHB), is output.

[0084] During the bias output control period, the phase switching detection operation of the Hall signal is not performed, and the current consumption of the Hall bias output unit 45 is reduced.

[0085] For example, in Figure 2 In the comparative example, when the power supply is 24V, the regulator output voltage is 1.3V, and the bias current is 5mA, the Hall sensor consumes 1.3V×5mA=6.5mW of power, and the regulator output consumes (24V-1.3V)×5mA=113.5mW of power.

[0086] In contrast, in the present invention, the power consumption of the Hall bias when the motor is in a stable rotation state can be reduced by ((N-1) / N)×(1-1 / a) compared to the case where the Hall bias control is not performed. 2 )×100[%] of electricity. Figure 2 Under the same conditions, when the control of the present invention is performed, for example, when N=8 and a=30, the power consumption is 15.1 mW (12.6%), and the power consumption of the Hall bias can be reduced by 87.4%. In this way, by controlling the Hall bias voltage of the present invention, the power consumption of the Hall bias can be greatly reduced compared with the case without the Hall bias control.

[0087] As described above, in the present invention, the Hall sensor is biased only near the necessary timing to detect the phase switching timing, so that the bias current of an unnecessary portion can be reduced and the power consumption can be greatly suppressed.

[0088] Furthermore, the bias voltage itself is not disconnected even in a portion where detection by the Hall sensor is not required, so no on / off switching or switching noise is generated, and by allowing an idle current to flow at a low bias voltage value, the action can be smoothly transferred after returning to a high bias voltage value.

[0089] However, when the rotation is not stable but in an unstable state such as when starting or decelerating for stopping, the FG cycle is unstable, so the previous and next FG cycles sometimes vary greatly. For example, in an operation mode where the acceleration of the rotation speed increases such as when starting or when the rotation speed control input changes (rotation speed changes), when the Hall bias control of the present invention is performed, the phase switching of the Hall signal occurs during the period <(N-1) / N> of the half cycle in which the bias voltage is set low based on the previous half cycle, and it may be impossible to detect the accurate magnetic field change period T, and the FG signal cannot be switched.

[0090] Therefore, in the present invention, Hall bias control is not performed in each period from when the motor is started to when the motor speed is stabilized, from when a control instruction for speed change is input to when the speed is stabilized, and from when the motor is locked to when the motor is restarted and the motor speed is stabilized. Instead, a Hall bias voltage, i.e., a first voltage value VHB, which can stably detect the magnetic field is output and the Hall sensor is biased.

[0091] Then, it is determined whether to perform control to reduce the bias voltage, and the Hall bias control is performed only when the rotation speed is stable.

[0092] use Figure 3 , Figure 7 The determination of whether or not the bias voltage is controlled will be described. Figure 7 FIG. 1 is a detailed flow chart of the bias control determination of the present invention. Figure 6 The timing of S105, i.e. Figure 5 Executed between t1 and t2.

[0093] During the unstable period before entering the stable state, a clock is output, so that the half-cycle length is always counted in the half-cycle timer 421, and the first voltage value VHB as the normal Hall bias voltage is output in the Hall bias output unit 45. A predetermined maximum value is set in the register 432.

[0094] Figure 7 This process is in Figure 6 At the same time as the cycle measurement of the half-cycle timer 421 of S103 is completed, it is executed in parallel with S104.

[0095] In step S501 , the register 432 rewrites the current half cycle length measured by the current half cycle timer 421 into the register value and stores it.

[0096] In parallel with the above-mentioned S501, in S502, the stability determination unit 434 compares the current (previous) half cycle length (measured value) of the half cycle timer 421 with the stored value of the register 432. The stored value of the register 432 is substantially equivalent to the half cycle length of the previous cycle. However, when this control is the first time, the stored value of the register 432 becomes the set maximum value.

[0097] In S503, when the change in the half cycle length of the timer measurement value relative to the stored value is more than ±d%, the rotation is considered unstable, and the count value of the stability determination counter 433 is reset to 0 in S505. In S508, the stability determination unit 434 determines that there is no Hall bias output control. When it is determined that there is no Hall bias output control, the output control signal is kept at L (S510).

[0098] On the other hand, if it is "No" in S503, it is considered that the change of the half cycle length this time with respect to the half cycle length last time is small, and in S504, the count value of the stability determination counter 433 is increased by 1.

[0099] Then, it is determined whether the count value of the stability determination counter 433 that is incremented in S505 becomes M or more (M is a natural number greater than 2), and if it is M or more (Yes), the stability determination unit 434 determines that the Hall bias output control is in effect (S507). Then, the control signal of the Hall bias output control is set to H (S509).

[0100] In this way, in addition to comparing the current half-cycle length with the previous half-cycle length in S503 and finding a small change, after accumulating more than M half-cycle lengths in S505 and obtaining confirmation that the change is small, the bias control of voltage attenuation, that is, the output of the second voltage value in the first period, is started.

[0101] Therefore, in the present invention, by performing Hall bias control only when the rotation speed is stable while suppressing power consumption, it is possible to reliably and accurately detect the switching timing of the FG signal without missing it, and drive control of the motor can be performed.

[0102] (Variant 1)

[0103] In the above, the example of the Hall element is described as an example of a magnetic sensor for detecting the magnetic field of the motor, but the type of magnetic sensor that can detect the magnetic field of the rotating motor as a magnetic signal is not limited, for example, it can also be other magnetic sensors such as MR (Magneto Resistance) sensors.

[0104] (Variant 2)

[0105] In the above Figure 1 , a structure using FETs as switches of the H-bridge circuit is described, but the switches of the H-bridge may also be constituted by bipolar transistors.

[0106] (Variant 3)

[0107] Furthermore, the motor driving unit of the motor driving device of the present invention can be applied not only to a 1-channel H-bridge but also to a 1.5-channel H-bridge (3 half-bridge) BLDC motor.

[0108] The preferred embodiments are described in detail above, but are not limited to brushless DC motors and can be applied to stepper motors with magnetic sensors. They are not limited to the above-mentioned embodiments and can be variously modified and replaced without departing from the scope described in the scope of the patent protection requested.

[0109] Explanation of symbols

[0110] 1 motor drive device,

[0111] 2. Control circuit,

[0112] 3H bridge circuit (motor drive unit),

[0113] 4Bias adjustment unit,

[0114] 5 motors (single-phase motors, brushless DC motors),

[0115] 6 Hall element (magnetic sensor),

[0116] 10. Drive control device,

[0117] 21 position detection signal generating unit,

[0118] 22 output control unit,

[0119] 23Gate driver,

[0120] 41 Oscillator,

[0121] 42 timers,

[0122] 43 rotation stability determination unit,

[0123] 44 control signal generating unit,

[0124] 45 Hall bias output section,

[0125] 421 half-cycle timer (first measuring unit),

[0126] 422 cycle counter (second measurement unit),

[0127] 431 cycle comparison unit,

[0128] 432 registers,

[0129] 433 Stability determination counter,

[0130] 434 Stability Determination Unit,

[0131] IN1, IN2 Hall signal (magnetic signal),

[0132] FG signal position detection signal,

[0133] VHB first voltage value,

[0134] VHB / a second voltage value.

Claims

1. A motor driving device for driving a brushless DC motor, characterized in that: The motor drive device comprises: a motor driving unit that drives the motor; a magnetic sensor that detects a magnetic field generated by the rotation of the motor and outputs the magnetic signal; and a bias adjustment unit that adjusts and outputs a bias voltage used when the magnetic sensor detects a magnetic field, During a first period after the phase of the magnetic signal is switched, the bias adjustment unit adjusts the bias voltage to a second voltage value lower than a first voltage value at which the magnetic sensor can detect a magnetic field. The bias adjustment unit adjusts the bias voltage to the first voltage value in a second period from the first period to the next phase switching of the magnetic signal.

2. The motor drive device according to claim 1, characterized in that: The motor drive device includes: a position detection signal generating unit that outputs a position detection signal whose phase is switched by switching the phase of the magnetic signal generated by the magnetic sensor; The bias adjustment unit has: a first measuring unit for measuring a half-cycle length of the position detection signal; The second measuring unit measures a first period in the current half cycle based on a product of a half cycle length of the previous half cycle measured by the first measuring unit and a predetermined value smaller than 1.

3. The motor drive device according to claim 2, characterized in that: The bias adjustment unit further comprises: a control signal generating unit that outputs a control signal for controlling the bias voltage in a control state during a first period of the current half cycle measured by the second measuring unit, starting from the phase switching of the position detection signal; as well as The bias output unit outputs the bias voltage at the second voltage value while the control signal is output in the control state.

4. The motor drive device according to claim 3, characterized in that: The bias output unit includes: an input terminal, a constant current source, two resistors, and an input switch connected between the two resistors. When the control signal is not in the control state, the input switch is turned off, and the current generated by the constant current source is multiplied by the resistance values ​​of the two resistors to generate a bias voltage. When the control signal is in the control state, the input switch is turned on, and the current generated by the constant current source is multiplied by the resistance value of one of the two resistors to generate a bias voltage.

5. The motor drive device according to claim 2, characterized in that: The bias adjustment unit includes a rotation stability determination unit that compares the half cycle length immediately before the phase switching of the magnetic signal measured by the first measurement unit with the half cycle lengths two cycles before that to determine whether to adjust the bias voltage.

6. The motor drive device according to claim 5, characterized in that: When the rate of change of the previous half cycle length relative to the two previous half cycle lengths is equal to or greater than a predetermined value, the offset adjustment unit does not perform control to set the offset voltage to the second voltage value during a first period in the current half cycle.

7. The motor drive device according to claim 5, characterized in that: The rotation stability determination unit includes a stability determination counter that counts each time a change rate of the current half cycle length relative to the previous half cycle length is less than a predetermined value. When the change rate of the previous half cycle length relative to the two previous half cycle lengths is smaller than a predetermined value for more than a predetermined number of times, control is performed to set the bias voltage to the second voltage value during the first period of the current half cycle.

8. A motor drive control method, supplying a drive voltage to a brushless DC motor via a motor drive unit, characterized in that: The steps are as follows: a position detection signal generating step of outputting a position detection signal whose phase is switched by switching the phase of the magnetic signal generated by the magnetic sensor; A step of measuring, by a first measuring unit, a half cycle length of a phase switching of the position detection signal; The step of setting and measuring a first period in this half cycle by a second measuring unit based on a product of a length of a previous half cycle measured by the first measuring unit and a predetermined value less than 1; and a bias adjustment step of adjusting and outputting a bias voltage used when the magnetic sensor detects a magnetic field, In the bias adjustment step, In a first period after the phase of the magnetic signal is switched, the bias voltage is adjusted to a second voltage value lower than a first voltage value at which the magnetic sensor can detect the magnetic field, and outputted; In a second period from after the first period to the next phase switching of the magnetic signal, the bias voltage is adjusted to the first voltage value and output.

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