Motor drive device, and motor drive control method

Abstract

To suppress power consumption by surely detecting phase switching timing of a magnetic signal and reducing a bias current during an unnecessary period without generating switching noise in a motor drive device.SOLUTION: A motor drive device 1 for driving a brushless DC motor comprises a motor drive section 3 which drives a motor 5, a magnetic sensor 6 by which a magnetic field generated by rotation of the motor 5 is detected and outputted as magnetic signals IN1 and IN2, and a bias adjustment section 4 by which a bias voltage to be used for the magnetic field detection of the magnetic sensor is adjusted and outputted. The bias adjustment section 4 adjusts the bias voltage to a second voltage value (VHB / a) lower than a first voltage value of a value at which the magnetic sensor can detect the magnetic field, during a first period after phase switching of the magnetic signals IN1 and IN2 and adjusts the bias voltage to the first voltage value (VHB) during a second period from the lapse of the first period to the next phase switching of the magnetic signals.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor drive device and a motor drive control method. [Background technology]

[0002] To rotate a brushless DC motor (BLDC), the magnet attached to the rotor must detect the movement and change in the magnetic field that occurs as the rotor rotates, and a Hall sensor is used to detect this magnetic field. To generate a magnetic field detection signal from the Hall sensor, a certain voltage must be biased to the Hall sensor.

[0003] However, if the bias voltage is unstable, the magnetic field detection signal will also be directly affected and become 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 can cause the device temperature to rise, which can restrict the conditions of use.

[0004] In view of this, for example, Patent Document 1 discloses a control for intermittently operating a Hall element. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-111912 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned Patent Document 1, when the actual Hall phase switching occurs at a timing when the Hall element is not biased in order to operate intermittently, the actual phase switching timing cannot be accurately detected. In this technology, a correction circuit is proposed in preparation for the case where the phase switching cannot be detected, but since the correction is made by predicting it from the rotation signal period, there is a risk that the detection of the phase switching timing with certainty and accuracy cannot be guaranteed. In addition, there is a risk that the switching noise during the intermittent operation of the Hall element may be superimposed on the magnetic signal.

[0007] In view of the above circumstances, the present invention aims to provide a motor drive device that can reliably detect the phase change timing of a magnetic signal without generating switching noise, reduce bias current during unnecessary periods, and suppress power consumption. [Means for solving the problem]

[0008] In order to solve the above problems, in one aspect of the present invention, A motor drive device for driving a brushless DC motor, 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; a bias adjustment unit that adjusts and outputs a bias voltage used when the magnetic sensor detects a magnetic field, The bias adjustment unit includes: adjusting the bias voltage to a second voltage value lower than a first voltage value at which the magnetic sensor can detect a magnetic field during a first period after a phase change of the magnetic signal; adjusting the bias voltage to the first voltage value during a second period from after the first period has elapsed until a next phase change of the magnetic signal; A motor drive device is provided. Effect of the Invention

[0009] According to one embodiment, in a motor drive control circuit that rotates a brushless DC motor, the phase switching timing of a magnetic signal is reliably detected without generating switching noise, and bias current during unnecessary periods is reduced, thereby suppressing power consumption. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a motor drive device according to an embodiment of the present invention; [Diagram 2] FIG. 11 is an explanatory diagram of signal operation during steady rotation in a motor drive device of a comparative example. [Diagram 3] FIG. 1 is a functional block diagram of a bias adjustment unit according to an embodiment; [Figure 4] FIG. 4 is a circuit diagram of a Hall bias output unit according to the embodiment. [Diagram 5] FIG. 4 is an explanatory diagram of signal operation during steady rotation in the motor drive device of the present invention. [Figure 6] 4 is an overall flowchart of bias control according to the present invention. [Figure 7] 4 is a detailed flowchart of a bias control execution determination process according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and duplicated descriptions may be omitted.

[0012] First, the configuration of a motor drive device according to one embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing the configuration of a motor drive device according to one embodiment of the present invention.

[0013] The motor driving device 1 is incorporated in a fan motor for cooling heat-generating components such as a processor in an electronic device such as a notebook personal computer, for example. The motor driven by the motor driving device 1 is a brushless DC (Direct Current) motor (BLDC) equipped with a Hall sensor that is a rotor position detection element.

[0014] The motor driving device 1 is, for example, a circuit that drives a single-phase motor 5 for rotating a cooling fan, and includes a driving control device 10, the single-phase motor 5, and a Hall element 6. The driving control device 10 includes 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 include terminals and constitute a control IC as a semiconductor integrated circuit that controls the motor driving unit.

[0015] In the drive control device 10, the control circuit 2 has a position detection signal generating unit 21, an output control unit 22, and a gate driver 23. The control circuit 2 may also be provided with other circuits such as a PWM signal generating unit and a soft switch period generating unit. Hall signals IN1 and IN2 are input to the control circuit 2 from the Hall element 6.

[0016] The H-bridge circuit 3 is a motor drive section and is composed of PchFETs M1 and M2 and NchFETs M3 and M4. The PchFET M1 functions as a first upper switch, the NchFET M4 as a first lower switch, the PchFET M2 as a second upper switch, and the NchFET M3 as a second lower switch.

[0017] The rotor of the single-phase motor 5 is equipped with magnets of north and south poles, while the Hall element 6 is fixed so as to be able to detect the magnetic field of the magnet equipped on the rotor. The Hall element 6, which is a magnetic sensor, outputs Hall signals IN1, IN2 at a voltage level corresponding to the strength of the detected magnetic field to its terminals. The magnet also rotates with the rotation of the rotor, 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. The Hall signals IN1, IN2 in this embodiment are, for example, sine wave 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. It should be noted that the Hall signals IN1, IN2 are not limited to sine waves.

[0018] The bias adjustment unit 4 adjusts the level of a 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.

[0019] 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 (frequency generation) signal (position detection signal) whose frequency changes according to the rotation speed of the single-phase motor 5.

[0020] The position detection signal generating unit 21 generates an FG signal that goes to a high level (hereinafter, "H" level) when the level of the Hall signal IN1 becomes higher than that of the Hall signal IN2, and goes to a low level (hereinafter, "L" level) when the level of the Hall signal IN1 becomes lower than that of the Hall signal IN2. However, the position detection signal generating unit 21 performs 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 is outputting the Hall signal.

[0021] The output control unit 22 generates signals for switching the FETs M1, M2, M3, and M4 of the H-bridge circuit 3, and outputs the signals to the gate driver .

[0022] The gate driver 23 controls each MOSFET in the H-bridge circuit 3, and changes the drive current Idr that drives the motor coil L of the single-phase motor 5. In detail, the gate driver 23 outputs a gate control voltage for turning on and off the gates of the FETs M1, M2, M3, and M4 in the H-bridge circuit 3, respectively.

[0023] The bias adjustment unit 4 is a circuit for adjusting, at an appropriate timing, a bias voltage, which is the strength of an electric field applied to cause the Hall element 6 to output a Hall signal, which is a magnetic field detection signal.

[0024] <Comparative Example> Here, a general behavior of the Hall bias when the bias adjustment unit 4 is not provided will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram of signal operation during steady rotation in a motor drive control device of a comparative example.

[0025] Conventionally, a bias voltage of a level that enables the Hall element to output a Hall signal is always applied regardless of the states of the Hall signals IN1 and IN2.

[0026] As an example, when a bias voltage is applied to the Hall element, if the bias voltage is 1.0 to 1.3 V and the impedance of the Hall sensor is 200 to 500 Ω, the bias current is 2 to 7 mA.

[0027] For example, if the power supply is 24V, the regulator output voltage is 1.3V, and the bias current is 5mA, the Hall sensor consumes 1.3V x 5mA = 6.5mW of power, and the regulator output section consumes (24V - 1.3V) x 5mA = 113.5mW of power.

[0028] Furthermore, if the bias voltage is unstable, the magnetic field detection signal will also be directly affected and become unstable, so the bias to the Hall is provided by a stabilized voltage source (regulator). In particular, the power consumption of the regulator can cause the device temperature to rise, which can restrict the conditions of use.

[0029] However, to rotate a BLDC motor, all that is needed is to know the timing of phase switching (= switching of the magnetic fields N and S), and there is no need to constantly flow a bias current. More specifically, the output of the FG signal, which is the position detection signal for the subsequent stage, is inverted when it reaches the point where the Hall signals IN1 and IN2 have the same potential, and the timing of this FG signal output switching is used in the control of the subsequent stage. As long as it is known other than the timing of the FG signal output switching, i.e., the timing when the Hall signals IN1 and IN2 have the same potential, there is no need to apply a bias current at a level that allows the Hall signal to be output during other periods.

[0030] Therefore, in the present invention, by providing the bias adjustment unit 4, the bias voltage is significantly reduced except for the timing required for control, that is, during a period other than the predetermined period immediately before the phase switching of the FG signal.

[0031] (Bias adjustment section) Here, the bias adjuster 4 and the position detection signal generator 21 will be described in detail with reference to Fig. 3. Fig. 3 is a functional block diagram of the bias adjuster 4 and the position detection signal generator 21.

[0032] As described above, the bias 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 bias output unit 45.

[0033] More specifically, the timer 42 has a half-cycle timer 421 and an intra-cycle counter 422. The half-cycle timer 421 is a first measurement unit, and measures the fluctuation period T of the magnetic field that is approximately equal to the rotation period of the rotor of the motor 5, that is, the half-cycle length that is the length of half the period of the FG signal. A clock is input to the half-cycle timer 421 from the oscillator 41, and the half-cycle timer 421 operates steadily.

[0034] The in-period counter 422 is a second measurement unit that counts the elapsed time in the current half period of the FG signal. The in-period counter 422 sets and measures a first period in the current half period based on the product of the half period length of the immediately preceding half period measured by the half period timer 421 and a predetermined value less than 1.

[0035] 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 .

[0036] The register 432 stores the half-cycle length of the previous half cycle, and stores a specified value only the first time. Every time the output logic of the FG signal is inverted, the register 432 registers the half-cycle length T, which is the measurement result, i.e., the register value is rewritten.

[0037] The cycle comparator 431 compares the current half cycle length measured by the half cycle timer 421 with the value of the previous half cycle length stored in the register 432 or a specified value only for the first time. If there is a large change in the cycle length between the previous half cycle and the current half cycle, the cycle comparator 431 makes the stability determiner 434 determine that there is no bias output control and makes the control signal generator 44 output L.

[0038] Stability determination counter 433 quantifies the degree of stabilization and counts it. In detail, stability determination counter 433 counts every time the fluctuation rate of the current half cycle length with respect to the immediately preceding half cycle length becomes less than a predetermined value (d%). The predetermined value of the fluctuation rate is, for example, about 5 to 10%.

[0039] When the value of the stability determination counter 433 is equal to or greater than a predetermined value, the stability determination unit 434 determines that bias output control is required since there is little variation in the half cycle length, and causes the control signal generation unit 44 to output H. In detail, when the variation rate of the current half cycle length with respect to the immediately preceding half cycle length is less than a predetermined value for a predetermined number of times (M times) or more, the stability determination unit 434 causes the control to be executed to lower the bias voltage below a value at which a magnetic field can be detected during the first period. The predetermined number of times (M times) is, for example, 2 to 8 times.

[0040] Only when control is required as determined by rotation stability determiner 43, control signal generator 44 outputs the control signal for controlling the bias voltage as H. At this time, control signal generator 44 outputs the control signal for controlling the bias voltage in a controlled state during the first period in the current half period measured by intra-period counter 422, starting from the phase switch of the FG signal.

[0041] In the control signal generating unit 44, the first period during which the control signal is output at H (control state) is a period shorter than the immediately preceding half cycle length and is a period other than the immediately preceding half cycle length x a predetermined ratio (1 / N), that is, the product (T x (N-1) / N) of the "immediately preceding half cycle length" and a predetermined value less than 1. 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.

[0042] On the other hand, the second period during which the control signal generating unit 44 outputs the control signal at L is the remaining period from the end of the first period to the next phase switch of the FG signal (Hall signal) in the current half cycle.

[0043] The Hall bias output unit 45 controls and outputs a bias voltage lower than a value at which the Hall element 6 can detect a magnetic field while the control signal is output at H (control state), and outputs the bias voltage at a value at which the Hall element 6 can detect a magnetic field while the control signal is output at L (non-control state). In detail, the Hall bias output unit 45 outputs the bias voltage at a second voltage value lower than the first voltage value during a first period when the control signal is output at H, and outputs the bias voltage at the first voltage value at which a magnetic field can be detected during a second period when the control signal is output at L.

[0044] In this way, in the second period immediately before the next phase change of the FG signal (Hall signal), the bias voltage is adjusted to the first voltage value at which the magnetic field can be detected, so that the timing of the phase change of the Hall signal can be detected without missing it. Details of the control by the bias adjustment unit 4 will be described in detail with reference to Figs. 5 to 7.

[0045] On the other hand, the position detection signal generating unit 21 has a Hall comparator 211 and a latch unit 212. The Hall comparator 211 generates an FG signal that goes to H level when the level of the Hall signal IN1 becomes higher than the level of the Hall signal IN2 and goes to L level when the level of the Hall signal IN1 becomes lower than the level of the Hall signal IN2 when the control signal is L and an electric field capable of detecting a magnetic field is applied to the Hall element 6. 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.

[0046] (Hall bias output section configuration) FIG. 4 is a circuit diagram of the Hall bias output section 45. As shown in FIG. The Hall bias output unit 45 has a voltage control unit 451 and an output unit 452. The voltage control unit 451 has a constant current source 453, PchFETs M5 and M6, and resistors R1 and R2. The constant current source 453 is, for example, a regulator with a stable output. The PchFET M5, which is an input switch, is connected between the two resistors R1 and R2.

[0047] The output section 452 has a PchFET M7 connected to a power supply Vcc2. The PchFET M7 is an FET for reverse connection protection.

[0048] When the control signal is L, the input switch PchFETM5 is turned off, so the current Ir generated by the constant current source is <r a>A resistor R2 having a resistance<R×(a-1) / a> Thus, when the control signal is L, the output section 452 outputs a bias voltage of the current Ir×R generated by the constant current source.

[0049] 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 <r a>A voltage is generated by grounding the resistor R2 having a resistance of 1. Therefore, when the control signal is H, the output section 452 outputs a bias voltage of a current Ir×R / a generated by a constant current source.

[0050] That is, when the control signal is L (not in the 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, whereas when the control signal is H (in the 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.

[0051] As a result, 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, 1 / a of the low bias voltage is preferably 1 / 10 to 1 / 50, and therefore the resistance value of resistor R1 is set to be << the resistance value of resistor R2.

[0052] (Example of bias control in steady state) Next, the signal operation when performing bias control during steady rotation will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is an explanatory diagram of the signal operation during steady rotation in the motor drive control device of the present invention. Fig. 6 is an overall flowchart of the bias control of the present invention.

[0053] In a state without bias control before entering the steady state, as a prerequisite start-up operation, in S101, the Hall bias output unit 45 starts up and outputs a first voltage value (VHB) that is a voltage value at which the Hall element 6 can detect a magnetic field as a bias voltage. Then, a clock is generated by the oscillator 41, and the half-cycle timer 421 constantly counts the half-cycle length that is the length of a half cycle of the FG signal.

[0054] In this state, in step S102, when the Hall signals IN1 and IN2 reach the same potential due to the rotation of the motor (change in the magnetic field), this becomes the starting point of the cycle, and the flow from S103 onwards begins.

[0055] As the Hall signals become equal in potential in S102, the polarity of the output of the FG signal, which is a position detection signal, is inverted in S103. Immediately after the output polarity of the FG signal is inverted, the latch unit 212 latches the state of the FG signal. In addition, in response to the inversion of the output polarity of the FG signal, the half-cycle timer 421, which counts the half-cycle, ends the measurement of the length of the half-cycle of the FG signal up to that point (the previous half-cycle length T).

[0056] In S104, the half-cycle timer 421 is reset and starts measuring the length of the half cycle of the FG signal in the current cycle. At the same time, the half-cycle length of the FG signal measured in S103 is captured as the half-cycle length (half-cycle length) T in the intra-cycle counter 422, and the intra-cycle counter 422, which is the second measurement unit, starts counting the first period up to the half-cycle length T×(N−1) in that half cycle.

[0057] Then, in S105, it is determined whether or not the output control of the Hall bias is performed. In response to the inversion of the FG signal in S103, S104 and S105 are executed in parallel. The determination whether or not the output control is performed will be described in detail with reference to FIG.

[0058] If it is determined in S105 that the Hall bias output control is necessary, the control signal becomes H in S106.

[0059] 6 are executed at t1 in FIG. 5, with almost no time lag.

[0060] On the other hand, if it is determined in S105 that the Hall bias output control is not required, the control signal remains at L in S107, and the operations of S108 to S111 are not performed.

[0061] In response to the switching of the control signal in S106, the Hall bias output unit 45 attenuates the Hall bias output voltage to the second voltage value (VHB / a) in S108. In conjunction with this, the Hall element 6 cannot detect the magnetic field due to the lack of magnetic field, and the output of the Hall signal is stopped (S108 is executed at t2 in FIG. 5).

[0062] In S109, when the count value of the intra-period counter 422 reaches T×(N−1), it is determined that the first period has ended, and in S110, the Hall bias control signal becomes L. (S109 and S110 are executed at t3 in FIG. 5).

[0063] As a result of the Hall bias control becoming L, in S111, the Hall bias output unit 45 outputs the first voltage value (VHB) which is the normal Hall bias voltage value. In response to this, the magnetic field becomes detectable, and the Hall element 6 becomes capable of detecting the Hall signal (detection state).

[0064] Furthermore, in response to the first voltage value (VHB) being output in S111, the latched state of the FG signal is released in S112 (S111 and S112 are executed at t4 in FIG. 5).

[0065] Then, returning to S102 in the flow (t5 in FIG. 5), when the rotation of the motor (change in the magnetic field) causes the Hall signals IN1 and IN2 to reach the same potential, that half cycle ends and the second period in that half cycle also ends.

[0066] At the same time, in S102 (t5 in FIG. 5), the timing at which the Hall signals IN1 and IN2 reach 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 thereafter, the above controls of S102 to S112 are repeated.

[0067] More specifically, in the next cycle 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 Tc, 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, and so on.

[0068] Since the rotation speed of the single-phase motor 5 changes slightly due to external factors, the half-cycle lengths of the half-cycles Ta, Tb, and Tc of the FG signal also change slightly. The first period, which is the bias voltage control period during which the bias voltage output is controlled to be low, is calculated based on the half-cycle length of the immediately preceding half cycle. Therefore, if the half-cycle length of the immediately preceding half cycle is long and the current half cycle is short, the proportion of the first period in that half cycle will be long, as in cycle Tb. On the other hand, if the immediately preceding half cycle is short and the current half cycle is long, the proportion of the first period in that half cycle will be short, as in cycle Tc.

[0069] Thus, in the present invention, during the first period ((N-1) / N) which is the period from immediately after detecting a phase change in the Hall signal to just before the next phase change, the bias voltage is controlled to a second voltage value (VHB / a) lower than the value at which the Hall element can detect a magnetic field, and during the second period other than the first period, the bias voltage is set to the first voltage value (VHB), which is the value at which the magnetic field can be detected.

[0070] During the bias output control period, the phase switch detection operation of the Hall signal is not performed, and the current consumption of the Hall bias output unit 45 is reduced.

[0071] For example, in the comparative example of Figure 2, 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 x 5mA = 6.5mW of power, and the regulator output consumes (24V - 1.3V) x 5mA = 113.5mW of power.

[0072] In contrast, in the present invention, the power consumption of the Hall bias when the motor rotation is stable is ((N-1) / N)×(1-1 / a) compared to the case without Hall bias control. 2 )×100[%] of power can be reduced. If the control of the present invention is executed under the same conditions as in FIG. 2, for example, with N=8 and a=30, the power consumption will be 15.1 mW (12.6%), and the power consumption due to the Hall bias can be reduced by 87.4%. In this way, by controlling the Hall bias voltage according to the present invention, the power consumption due to the Hall bias can be significantly reduced compared to the case without the Hall bias control.

[0073] As described above, in the present invention, the Hall sensor is biased only in the vicinity of the required timing to detect the phase switching timing, thereby reducing unnecessary bias current and significantly suppressing power consumption.

[0074] Furthermore, because the bias voltage itself is not turned off even in areas where Hall sensor detection is not required, no on-off switching occurs and no switching noise is generated. In addition, by allowing idling current to flow at a low bias voltage value, operation can be smoothly transitioned after returning to a high bias voltage value.

[0075] However, when the rotation is unstable, such as during startup or deceleration for stopping, rather than during steady state operation, the FG cycle may be unstable, causing a large change in the preceding and following FG cycles. For example, in an operation mode in which the acceleration of the rotation speed increases, such as during startup or when the rotation speed control input changes (rotation speed change), if the Hall bias control of the present invention is performed, the phase of the Hall signal may change during the half cycle <(N-1) / N> in which the bias voltage is set low based on the previous half cycle, and the accurate magnetic field fluctuation cycle T may not be detected, and the FG signal may not be switched.

[0076] Therefore, in the present invention, Hall bias control is not performed during each period from when the motor is started until the motor rotation speed stabilizes, from when a control command for changing the speed is input until that speed stabilizes, and from when the motor lock is detected until the motor is restarted and the motor rotation speed stabilizes.Instead, the first voltage value VHB, which is a Hall bias voltage that can steadily detect a magnetic field, is output to bias the Hall sensor.

[0077] Then, a determination is made as to whether or not to perform control to lower the bias voltage, and the Hall bias control is performed only when the rotation speed is stable.

[0078] The bias voltage control / non-control determination will be described with reference to Fig. 3 and Fig. 7. Fig. 7 is a detailed flowchart of the bias control / non-control determination of the present invention. This bias control determination is performed at the timing of S105 in Fig. 6, that is, between t1 and t2 in Fig. 5.

[0079] During the unstable period before entering the steady state, a clock is output so that the half-cycle timer 421 constantly counts the half-cycle length, the Hall bias output unit 45 outputs the first voltage value VHB which is the normal Hall bias voltage, and a predetermined maximum value is set in the register 432.

[0080] This flow in FIG. 7 is executed in parallel with S104 when the period measurement by the half period timer 421 in S103 in FIG. 6 is completed.

[0081] 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.

[0082] In parallel with the above 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 value stored in the register 432. The value stored in the register 432 generally corresponds to the half cycle length of the previous cycle. However, if this control is the first time, the value stored in the register 432 is the maximum value that has been set.

[0083] In S503, if the amount of change in the half cycle length, which is the current timer measurement value, from the stored value is ±d% or more, it is determined that the rotation is unstable, and in S505 the count value of the stability determination counter 433 is reset to 0, and in S508 the stability determination unit 434 determines that the Hall bias output control is not performed. When it is determined that the Hall bias output control is not performed in this way, the output control signal remains at L (S510).

[0084] On the other hand, if NO in S503, it is determined that there is little variation in the current half cycle length from the previous half cycle length, and the count number of the stability determination counter 433 is incremented by +1 in S504.

[0085] Thereafter, it is determined whether the count number of the stability determination counter 433 counted up in S505 is equal to or greater than M (M is a natural number equal to or greater than 2), and if it is equal to or greater than M (YES), the stability determination unit 434 determines that the Hall bias output control is being performed (S507). Then, the control signal for the Hall bias output control is set to H (S509).

[0086] In this way, in S503, the current half-cycle length is compared with the previous half-cycle length and it is confirmed that the amount of variation is small. In addition, in S505, it is confirmed that the amount of variation is small by accumulating M or more half-cycle lengths. Then, output of the second voltage value in the first period, which is bias control of voltage attenuation, is started.

[0087] Therefore, in the present invention, by suppressing power consumption and performing Hall bias control only when the rotation speed is stable, the timing to switch the FG signal can be detected reliably and accurately, and the motor can be driven and controlled.

[0088] (Variation 1) In the above, a Hall element has been described as an example of a magnetic sensor that detects the magnetic field of a motor. However, any type of magnetic sensor that can detect the magnetic field of a rotating motor as a magnetic signal may be used, and other magnetic sensors such as an MR (Magneto Resistance) sensor may also be used.

[0089] (Variation 2) In FIG. 1, a configuration has been described in which FETs are used as the switches of the H-bridge circuit, but the switches of the H-bridge may be configured with bipolar transistors.

[0090] (Variation 3) Furthermore, the motor driving unit of the motor driving device of the present invention is applicable to BLDC motors with not only a 1-channel H-bridge but also a 1.5-channel H-bridge (three half-bridges).

[0091] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and can be applied not only to brushless DC motors but also to stepping motors equipped with magnetic sensors. Various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0092] 1 Motor drive unit 2. Control circuit 3 H-bridge circuit (motor drive section) 4. Bias adjustment section 5 Motors (single-phase motors, brushless DC motors) 6 Hall element (magnetic sensor) 10 Drive control device 21 Position detection signal generator 22 Output control section 23 Gate Driver 41 Oscillator 42 Timer 43 Rotation stability judgement unit 44 Control signal generator 45 Hall bias output section 421 Half-period timer (first measuring unit) 422 Intra-period counter (second measurement unit) 431 Period comparison section 432 Register 433 Stability Determination Counter 434 Stability judgment section IN1, IN2 Hall signal (magnetic signal) FG signal Position detection signal VHB 1st voltage value VHB / a Second voltage value< / r> < / r>

Claims

1. A motor drive device for driving a brushless DC motor, 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; a bias adjustment unit that adjusts and outputs a bias voltage used when the magnetic sensor detects a magnetic field, The bias adjustment unit includes: adjusting the bias voltage to a second voltage value lower than a first voltage value at which the magnetic sensor can detect a magnetic field during a first period after a phase change of the magnetic signal; During a second period from the end of the first period to the next phase switching of the magnetic signal, the bias voltage is adjusted to the first voltage value. Motor drive unit.

2. a position detection signal generating unit that outputs a position detection signal whose phase is switched when the phase of the magnetic signal generated by the magnetic sensor is switched; The bias adjustment unit includes: a first measurement unit that measures a half-cycle length of the position detection signal; a second measurement unit that measures a first period in a current half cycle based on a product of a half cycle length of the immediately preceding half cycle measured by the first measurement unit and a predetermined value less than 1; 2. The motor drive device according to claim 1.

3. The bias adjustment unit includes: a control signal generating unit configured to output a control signal for controlling the bias voltage in a controlled state during a first period in the current half cycle measured by the second measuring unit, the first period being determined based on a phase change of the position detection signal; a bias output unit that outputs the bias voltage at the second voltage value while the control signal is being output in the control state. The motor drive device according to claim 2.

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

5. The bias adjustment unit has a rotation stability determination unit that compares the half cycle length measured by the first measurement unit immediately before the phase switching of the magnetic signal with the half cycle length two periods before that to determine whether or not to adjust the bias voltage. The motor drive device according to claim 2.

6. The bias adjustment unit does not execute control to set the bias voltage to the second voltage value during a first period in the current half cycle when a fluctuation rate of the immediately preceding half cycle length with respect to the half cycle length two cycles before is equal to or greater than a predetermined value. The motor drive device according to claim 5.

7. The rotation stability determination unit is a stability determination counter which counts each time a fluctuation rate of a current half cycle length with respect to a half cycle length immediately before it becomes less than a predetermined value; When a case where the rate of change of the immediately preceding half circumference length with respect to the half cycle length two cycles before is less than a predetermined value continues for a predetermined number of times or more, control is executed to set the bias voltage to the second voltage value in a first period of the current half cycle. The motor drive device according to claim 5.

8. A motor drive control method for supplying a drive voltage to a brushless DC motor via a motor drive unit, comprising: a position detection signal generating step of outputting a position detection signal whose phase is switched when the phase of the magnetic signal generated by the magnetic sensor is switched; measuring a half cycle length at which a phase of the position detection signal is switched by a first measurement unit; a step of measuring, by a second measuring unit, a first period in a current half cycle based on a product of the immediately preceding half cycle length measured by the first measuring unit and a predetermined value less than 1; 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, during a first period after a phase change of the magnetic signal, the bias voltage is adjusted to a second voltage value lower than a first voltage value at which the magnetic sensor can detect a magnetic field, and output the second voltage value; During a second period from the end of the first period to the next phase switching of the magnetic signal, the bias voltage is adjusted to the first voltage value and output. Motor drive control method.

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