Motor driver and semiconductor device

Abstract

To provide a motor driver capable of realizing sensor-less control by sine wave drive by utilizing current flowing in a three-phase inverter.SOLUTION: A motor driver includes: a PWM signal generation unit 42 that generates a PWM signal for sine wave energization driving, and stops generation of a PWM signal of one specific phase (a W-phase), and generates the PWM signal of the other two phases (a U-phase and a V-phase) at a fixed duty ratio in a specific section (from 30 degrees to 60 degrees) of an electrical angle as a rotor position estimation period; and a current phase determination unit 45 that determines whether it is an advanced phase or a delayed phase based on current flowing through an inverter circuit 3 in the rotor position estimation period. The PWM signal generation unit 42 increases a duty ratio of the PWM signal when determination results by the current phase determination unit 45 is the advanced phase, and decreases the duty ratio of the PWM signal when determination results by the current phase determination unit 45 is the delayed phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present disclosure relates to a motor driver that drives a brushless DC motor. [Background technology]

[0002] As a simple sensorless control method for a BLDC motor, a technique has been proposed in which the rotor position of a brushless DC motor is detected by utilizing the current flowing through an inverter circuit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-43083 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since a circuit for detecting back electromotive force is required and a non-energized section of about 60 degrees is required, it is difficult to realize sensorless control using sine wave drive. Furthermore, although Patent Document 1 states that it is also applicable to sine wave drive, it does not disclose a specific control method.

[0005] The present disclosure aims to provide a motor driver that can achieve sensorless control by sine wave drive using the current flowing in a three-phase inverter. [Means for solving the problem]

[0006] The motor driver disclosed herein is a motor driver that controls the on / off of switching elements of a three-phase inverter that supplies power to a three-phase brushless DC motor using a PWM signal, The inverter includes a PWM signal generation unit that generates the PWM signal for sinusoidal wave energization drive, and that stops generation of the PWM signal for one specific phase out of three during a specific electrical angle interval as a rotor position estimation period, and generates the PWM signals for the other two phases with a fixed duty ratio, and a current phase determination unit that determines whether the phase is leading or lagging based on a current flowing through the three-phase inverter during the rotor position estimation period, wherein the PWM signal generation unit increases the duty ratio of the PWM signal when the determination result by the current phase determination unit is the leading phase, and decreases the duty ratio of the PWM signal when the determination result by the current phase determination unit is the lagging phase. [Effects of the Invention]

[0007] The motor driver of the present disclosure can achieve sensorless control by sinusoidal wave drive using the current flowing through a three-phase inverter. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of an embodiment of a motor drive device. [Figure 2] 2 is a diagram showing a modified PWM control signal generated by a duty command unit shown in FIG. 1; [Figure 3] FIG. 10 is a diagram showing a path of a V-phase current flowing during a rotor position estimation period. [Figure 4] FIG. 10 is a diagram showing a V-phase current value during a rotor position estimation period. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

[0010] Motor drive device 1 of this embodiment is a device that controls the drive of a three-phase brushless DC motor 10. Referring to Fig. 1, motor drive device 1 includes an inverter circuit 3 that drives and controls brushless DC motor 10 by converting a DC voltage supplied from a DC power supply 2 into an arbitrary frequency.

[0011] Brushless DC motor 10 includes U-phase coil 10U, V-phase coil 10V, and W-phase coil 10W. Brushless DC motor 10 rotates by passing appropriate currents through the three-phase coils 10U, 10V, and 10W.

[0012] The DC power supply 2 is composed of a power supply circuit that combines a storage battery and an AC power supply and a converter circuit.

[0013] The inverter circuit 3 is a three-phase inverter having series circuits provided in high-side arms and low-side arms, each of which has a switching element connected thereto, corresponding to the U-phase, V-phase, and W-phase. The series circuits of the U-phase, V-phase, and W-phase are connected between a positive DC bus and a negative DC bus connected to the DC power supply 2. The inverter circuit 3 outputs drive power for driving the brushless DC motor 10 by controlling the on / off of the switching elements.

[0014] The motor drive device 1 includes a motor driver 4 that controls the on / off of switching elements of the inverter circuit 3. Part or all of the motor driver 4 can be configured as a driver IC, which is a semiconductor device integrated on a substrate.

[0015] The motor driver 4 includes a duty command unit 41, a PWM signal generation unit 42, a drive circuit 43, a current detection unit 44, a current phase determination unit 45, and a PWM fixing command 46.

[0016] Duty command unit 41 generates a voltage waveform shown in Fig. 2(a) that determines the duty ratio of the PWM signal for each phase as a modified PWM control signal and outputs it to PWM signal generation unit 42. Fig. 2(b) shows a PWM control signal for 180-degree modulation (sine wave drive) in which a third harmonic is superimposed on three sine waves shifted by 120°. The modified PWM control signal shown in Fig. 2(a) is obtained by using PWM fixing command 46 to set a specific section of the electrical angle (e.g., 30 degrees to 60 degrees of the U phase) as a rotor position estimation period in which the duty values ​​of the other two phases (e.g., the U phase and the V phase) are kept constant.

[0017] When the brushless DC motor 10 is started, it is started in a forced commutation mode using a PWM control signal for 180-degree modulation shown in FIG. 2(b), and after the forced commutation mode is over, the PWM control signal is switched to the modified PWM control signal shown in FIG. 2(a).

[0018] The PWM signal generating unit 42 generates a modified PWM control signal based on the input from the duty command unit 41 and the PWM fixing command 46. The PWM signal generating unit 42 generates, for example, a PWM signal with a 360-degree electrical angle interval in which the duty ratio is determined by comparing the duty command value, the modulated waveform of FIG. 2(b), and a triangular wave carrier (not shown), and a PWM signal in which a part of this interval is replaced with a PWM fixed by the PWM fixing command 46.

[0019] The modified PWM control signal has constant values ​​for two specific phases (e.g., U-phase and V-phase) during the rotor position estimation period. Therefore, during the rotor position estimation period, the duty ratios of the PWM signals for the two specific phases generated by the PWM signal generation unit 42 are fixed. Furthermore, during the rotor position estimation period, the PWM signal generation unit 42 stops outputting PWM signals for phases other than the two specific phases with fixed duty ratios (e.g., W-phase).

[0020] The drive circuit 43 converts the PWM signals generated by the PWM signal generation unit 42 into drive signals Hou, Hov, How, Lou, Lov, and Low with optimal voltages and switching speeds, and outputs these drive signals to the inverter circuit 3. The drive signals Hou, How, and How are drive signals that drive the switching elements of the high-side arms of the U, V, and W phases in the inverter circuit 3, respectively, and the drive signals Lou, Low, and Low are drive signals that drive the switching elements of the low-side arms of the U, V, and W phases in the inverter circuit 3, respectively.

[0021] In this embodiment, during the rotor position estimation period, the switching element of the U-phase high-side arm is chopped by PWM control, and the switching element of the V-phase low-side arm is controlled to be on (always at a high level at input) without being chopped. During the rotor position estimation period, the switching elements of the V-phase and W-phase high-side arms and the switching elements of the U-phase and W-phase low-side arms are controlled to be off. Therefore, during the rotor position estimation period, a V-phase current flows through the switching element of the U-phase high-side arm and the switching element of the V-phase low-side arm, as shown by the arrows in FIG. 3.

[0022] The motor drive device 1 includes current detection resistors RSu, RSv, and RSw connected between the low-side arm switching elements of the U-, V-, and W-phases of the inverter circuit 3 and the grounded negative DC bus. The current detection resistors RSu, RSv, and RSw convert the currents flowing from the output voltages U-, V-, and W-phases of the inverter circuit 3 to the brushless DC motor 10 into voltages.

[0023] The current detection unit 44 detects an overcurrent or a short-circuit current based on the U-phase current value, V-phase current value, and W-phase current value converted by the current detection resistors RSu, RSv, and RSw, and outputs an error signal.

[0024] Furthermore, current detection unit 44 detects current values ​​(V-phase current values ​​in this embodiment) of the phase through which current flows at multiple timings synchronized with the frequency of the PWM signal during the rotor position estimation period, and outputs the detected multiple V-phase current values ​​as rotor position estimation data to current phase determination unit 45. The multiple timings synchronized with the frequency of the PWM signal are specified by a current detection trigger from PWM signal generation unit 42. In other words, PWM signal generation unit 42 outputs current detection triggers to current detection unit 44 to notify the current detection unit 44 of the multiple timings synchronized with the frequency of the PWM signal during the rotor position estimation period.

[0025] FIG. 4(a) shows the V-phase current value during the rotor position estimation period. The solid line shows the waveform when the magnet position of brushless DC motor 10 is in the leading phase when the voltage phase of PWM signal generator 42 (modified PWM control signal) is applied to the stator windings of brushless DC motor 10. The dotted line shows the waveform when the magnet position of brushless DC motor 10 is in the lagging phase when the voltage phase of PWM signal generator 42 (modified PWM control signal) is applied to the stator windings of brushless DC motor 10. The V-phase current values ​​detected at times t1, t2, t3, and t4 synchronized with the PWM signal frequency are compared between the leading and lagging phases. The transition of the V-phase current value (current deviation) in the leading phase rises from time t1 to t2 and falls from time t3 to t4. In contrast, the transition of the V-phase current value (current deviation) in the lagging phase rises from time t1 to t2 and also rises from time t3 to t4. The transition of the V-phase current value (current deviation) from time t3 to t4 differs between the leading phase and the lagging phase. Therefore, the current detection unit 44 outputs the V-phase current values ​​at times t3 and t4 shown in FIG. 4 to the current phase determination unit 45 as rotor position estimation data.

[0026] Current phase determination unit 45 determines whether the phase is leading or lagging based on the rotor position estimation data, and outputs the determination result to duty command unit 41. Current phase determination unit 45 determines that the phase is leading when the V-phase current value decreases from time t3 to t4, and determines that the phase is lagging when the V-phase current value increases from time t3 to t4.

[0027] Note that there is no limit to the number of V-phase current values ​​that can be detected as rotor position estimation data as long as the current phase determination unit 45 can determine whether the rotor position estimation data is a leading phase or a lagging phase. Because the current phase determination unit 45 determines the phase based on the current deviation using multiple V-phase current values, it can determine whether the rotor position estimation data is a leading phase or a lagging phase using a simple algorithm.

[0028] 4(b), the current phase determination unit 45 may store in advance the transition of the V-phase current value in the reference phase and determine the phase by comparing it with the reference phase. In this case, there is also no limit to the number of V-phase current values ​​used as rotor position estimation data, and the rotor position estimation data may be continuous V-phase current values.

[0029] If the current phase determination unit 45 determines that the phase is leading, the duty command unit 41 increases the amplitude command of the modified PWM control signal to be generated, and if the current phase determination unit 45 determines that the phase is lagging, the duty command unit 41 decreases the amplitude command of the modified PWM control signal to be generated. As a result, the PWM signal generated by the PWM signal generation unit 42 increases the duty ratio if the current phase determination unit 45 determines that the phase is leading, and decreases the duty ratio if the current phase determination unit 45 determines that the phase is lagging. In other words, the motor driver 4 determines whether the phase is leading or lagging for each rotor position estimation period, and executes control to adjust the duty ratio of the PWM signal.

[0030] As described above, this embodiment of the present invention relates to a motor driver 4 that uses PWM signals to control the on / off of switching elements in an inverter circuit 3 (three-phase inverter) that supplies power to a three-phase brushless DC motor 10. The motor driver 4 includes a PWM signal generator 42 that generates a PWM signal for sinusoidal drive and stops generating a PWM signal for a specific phase (W phase) among the three phases during a specific electrical angle range (30 degrees to 60 degrees) as a rotor position estimation period, and generates PWM signals for the other two phases (U phase and V phase) with a fixed duty ratio. The motor driver 42 also includes a current phase determiner 45 that determines whether the current flowing through the inverter circuit 3 is in a leading phase or lagging phase during the rotor position estimation period. When the current phase determiner 45 determines that the current is in a leading phase, the PWM signal generator 42 increases the duty ratio of the PWM signal. This increases the motor rotation speed, shifting the rotor position phase of the motor in a lagging direction, thereby enabling phase control of the rotor position. When the current phase determiner 45 determines that the current is in a lagging phase, the PWM signal generator 42 decreases the duty ratio of the PWM signal. With this configuration, sensorless control using sine wave drive can be achieved by utilizing the current flowing through the inverter circuit 3. The current flowing through the inverter circuit 3 can use the current detection circuit used for overcurrent detection, etc. For a fan motor that is driven at a constant frequency with no load fluctuations, sine wave energization drive without uneven rotation is possible even if discontinuous rotor position estimation periods are provided in some sections. Sensorless drive equivalent to that achieved with the BEMF detection method can be achieved without increasing the scale of the control logic.

[0031] Furthermore, according to this embodiment, the current phase determination unit 45 determines whether the current flowing through the inverter circuit 3 is in a leading phase or lagging phase based on the current deviation of the current detection values ​​detected at multiple timings synchronized with the PWM signal. With this configuration, current phase determination unit 45 determines the phase from the current deviation using a plurality of detected V-phase current values, and therefore can determine whether the phase is leading or lagging using a simple algorithm.

[0032] Furthermore, this embodiment includes a duty command unit 41 that generates a modified PWM control signal that keeps constant the duty values ​​of two specific phases (U phase, V phase) in a specific electrical angle range (30 degrees to 60 degrees) as a PWM fixed command 46 in a PWM control signal for sinusoidal wave drive (for 180-degree modulation) that determines the duty ratio of the PWM signal, and the duty command unit 41 increases the amplitude of the modified PWM control signal when the determination result by the current phase determination unit 45 is the leading phase, and decreases the amplitude of the modified PWM control signal when the determination result by the current phase determination unit 45 is the lagging phase. With this configuration, rotor position estimation control can be performed using a simple algorithm according to the determination result by the current phase determination unit 45.

[0033] It is clear that the present invention is not limited to the above-described embodiments, and that each embodiment can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and the number, position, shape, etc. can be set to be suitable for implementing the present invention. Note that the same components are denoted by the same reference numerals in each drawing. [Explanation of symbols]

[0034] 1. Motor drive unit 2 DC power supply 3. Inverter circuit 4 Motor drivers 10 Brushless DC motor 10U, 10V, 10W coil 41 Duty Command 42 PWM signal generation section 43 Drive circuit 44 Current detection section 45 Current phase determination section 46 PWM fixed command RSu, RSv, RSw Current detection resistors

Claims

1. A motor driver that controls on / off of a switching element of a three-phase inverter that supplies power to a three-phase brushless DC motor using a PWM signal, a PWM signal generating unit that generates the PWM signal for sinusoidal wave energization drive, and stops generating the PWM signal for one specific phase out of three phases during a specific section of electrical angle as a rotor position estimation period, and generates the PWM signals for the other two phases with a fixed duty ratio; a current phase determination unit that determines whether the phase is leading or lagging based on a current flowing through the three-phase inverter during the rotor position estimation period, The motor driver is characterized in that the PWM signal generation unit increases the duty ratio of the PWM signal when the determination result by the current phase determination unit is the leading phase, and decreases the duty ratio of the PWM signal when the determination result by the current phase determination unit is the lagging phase.

2. 2. The motor driver according to claim 1, wherein the current phase determination unit determines whether the current flowing through the three-phase inverter is in the leading phase or the lagging phase based on a current deviation of current detection values ​​detected at multiple timings synchronized with the PWM signal.

3. a duty command unit that generates a modified PWM control signal in which specific duty values ​​of specific two phases are constant for a specific section of the electrical angle in a PWM control signal for sinusoidal wave drive that determines a duty ratio of the PWM signal; 3. The motor driver according to claim 1, wherein the duty command unit increases the amplitude of the modified PWM control signal when the determination result by the current phase determination unit is the leading phase, and decreases the amplitude of the modified PWM control signal when the determination result by the current phase determination unit is the lagging phase.

4. 10. A semiconductor device comprising: a motor driver according to claim 1 integrated on a substrate.

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