JP2020080647A - Brushless dc motor voltage controller and blower mounted therewith - Google Patents

Abstract

To provide a brushless DC motor voltage controller capable of improving the accuracy in the estimation of rotor position at startup by detecting subtle changes in motor current even when the capacitor is downsized.SOLUTION: There is provided a brushless DC motor voltage controller which includes: a PWM output unit that is configured to adjust the duty on the basis of motor voltage at startup which is input from a position estimation voltage application unit and a value of a smoothing voltage which is stored later by the delay time than a value of the smoothing voltage one cycle before and which is input from the comparison determination unit, and to output the duty to an inverter circuit; an inverter circuit that is configured to apply a pulsed voltage corresponding to the adjusted duty to the brushless DC motor in a state that a rotor is stopped; a current detection unit configured to detect a motor current flowing on the brushless DC motor corresponding to the pulsed voltage; and a start position estimation unit configured to estimate the position in the stopped state just before the rotor starts to rotate on the basis of the current value detected by the current detection unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a brushless DC motor voltage control device and a blower device equipped with the same.

  In recent years, since a brushless DC motor and its voltage control device are efficient, power-saving and have excellent durability, they are suitable for blowers such as range hoods, ceiling-embedded ventilation fans, air purifiers, or ceiling fans. Are being installed. Further, such a brushless DC motor and its voltage control device are required to be further reduced in cost and size. Further, in the voltage control device, since the AC power supply is rectified and smoothed, the power factor of the power supply circuit decreases. Therefore, it is required to increase the power factor from the viewpoint of regulation of harmonic current.

  In the conventional brushless DC motor voltage control device, a magnet is provided on the surface of the rotor from the viewpoint of size reduction and cost reduction. A sensorless method that does not use a magnetic sensor is often used to detect the position of the rotor. In this method, the position estimation of the rotor at the time of startup is performed by the method described in Patent Document 1, for example.

  In Patent Document 1, first, a pulsed voltage is applied from an inverter circuit to a winding of a brushless DC motor. At this time, the position of the rotor is estimated by utilizing the fact that the iron core of the brushless DC motor is saturated by the motor current flowing through the winding and the magnetic flux of the rotor, and the magnitude of the motor current changes slightly. There is.

  Further, Non-Patent Document 1 describes a method of PWM-controlling a pulsed voltage applied from an inverter circuit to a winding of a brushless DC motor. This describes a method of suppressing fluctuations in smoothed voltage after rectification and smoothing and detecting a minute change in motor voltage with high accuracy. Specifically, the duty is decreased when the smoothing voltage is high, and the duty is increased when the smoothing voltage is low. As a result, the pulsed voltage is unlikely to be affected by the fluctuation of the smoothed voltage.

JP, 6-113585, A

Vector control technology of brushless DC motor Masayasu Ezaki CQ publisher

  However, in order to reduce the size and cost of the voltage control device, for example, when a smoothing capacitor having a small capacity is used, the voltage fluctuation of the smoothing voltage due to charging/discharging of the smoothing capacitor becomes large and is applied to the winding of the motor. The fluctuation of the voltage also becomes large. This makes it difficult to correctly detect a minute change in the motor current due to saturation of the iron core.

  Moreover, it takes some time to calculate the duty of the PWM control based on the input smoothed voltage and output it to the inverter circuit. Therefore, when a smoothing capacitor having a small capacity is used, even if an attempt is made to suppress the fluctuation of the smoothing voltage based on the PWM control described above, the smoothing voltage is further changed at the time when the smoothing voltage is actually PWM-controlled. That is, a difference occurs between the smoothed voltage for which the duty of the PWM control is calculated and the actual smoothed voltage of the PWM control target. Due to this difference, a minute change in the motor current cannot be correctly detected, so that there is a problem in that the position of the rotor at the time of startup cannot be estimated.

  Therefore, the present invention solves the above-mentioned conventional problems, and can improve the accuracy of rotor position estimation at startup even when the capacitor is downsized, and can suppress startup failure. An object is to provide a device and a blower.

  A brushless DC motor voltage control device according to the present invention is based on a rectifier circuit that rectifies an AC voltage and converts it into a DC voltage, a smoothing circuit that smoothes the DC voltage and outputs a smoothed voltage, and an input duty, An inverter circuit that PWM-controls the input smoothed voltage and supplies the brushless DC motor to the brushless DC motor, a cycle detection unit that detects a cycle of fluctuations in the smoothed voltage, and a voltage storage unit that stores the value of the smoothed voltage corresponding to the cycle. , A position estimation voltage application unit that holds the motor voltage applied to the brushless DC motor, and the time from the smoothing voltage is output by the smoothing circuit until the smoothing voltage is output to the brushless DC motor via the inverter circuit, and smoothing The delay time storage unit stores the delay time, which is the difference between the time from the output of the smoothed voltage by the circuit to the output of the duty to the inverter circuit based on the smoothed voltage, and the input from the position estimation voltage application unit. A PWM output unit that adjusts the duty based on the motor voltage and the smoothed voltage value input from the comparison and determination unit and outputs the duty to the inverter circuit.

  According to the present invention, even when the capacitor is downsized, it is possible to detect a minute change in the motor current and improve the accuracy of estimating the position of the rotor at the time of starting.

FIG. 1 is a functional block diagram of the brushless DC motor voltage control device according to the first embodiment. FIG. 2A is a diagram showing an example of an AC voltage. FIG. 2B is a diagram showing an example of a smoothed voltage obtained by rectifying and smoothing an AC voltage. FIG. 3 is a diagram showing a method in which the cycle detection unit according to the first embodiment detects the cycle of voltage fluctuation from the value of the smoothed voltage held by the voltage holding unit. FIG. 4 is a diagram showing the value of the smoothed voltage for one cycle stored in the voltage storage unit according to the first embodiment. FIG. 5 is a diagram showing details of the delay time according to the first embodiment. FIG. 6 is a schematic diagram in which the comparison/determination unit according to the first embodiment determines a smoothed voltage that is delayed by a delay time from one cycle before. FIG. 7A is a diagram showing a duty waveform output by the PWM output unit according to the first embodiment. FIG. 7B is a diagram showing a duty waveform output by the PWM output unit according to the first embodiment. FIG. 8A is a diagram showing a voltage applied to the winding when the voltage is applied to the motor in the brushless DC motor voltage control device according to the first embodiment. FIG. 8B is a diagram showing a current flowing through the winding of the motor at the time of FIG. 8A. FIG. 9 is a flowchart illustrating the operation of the brushless DC motor voltage control device according to the first embodiment. FIG. 10 is a functional block diagram of the brushless DC motor voltage control device according to the third embodiment. FIG. 11A is a diagram showing an example of an AC voltage. FIG. 11B is a diagram showing an example of a smoothed voltage obtained by rectifying and smoothing an AC voltage using a valley fill circuit. FIG. 12 is a diagram showing a range hood according to the fourth embodiment. FIG. 13 is a block diagram of a brushless DC motor voltage control device according to the fifth embodiment. FIG. 14A is a diagram showing an example of a motor current when the duty of PWM control is adjusted in the brushless DC motor voltage control device according to the fifth embodiment. FIG. 14B is a diagram showing an example of the motor current when the duty of PWM control is not adjusted in the brushless DC motor voltage control device according to the fifth embodiment. FIG. 15 is a flowchart for explaining the operation of the brushless DC motor voltage control device according to the fifth embodiment. FIG. 16A is an explanatory view of a range hood equipped with a brushless DC motor voltage control device according to a conventional example as seen from a side surface. FIG. 16B is an explanatory diagram of an installed state of the range hood shown in FIG. 16A.

  A brushless DC motor voltage control device according to the present invention includes a rectifier circuit that rectifies an AC voltage and converts the AC voltage into a DC voltage, a smoothing circuit that smoothes the DC voltage and outputs a smoothed voltage, and an input duty cycle. An inverter circuit for PWM-controlling the input smoothed voltage to the brushless DC motor on the basis of the input voltage, a cycle detector for detecting the cycle of the fluctuation of the smoothed voltage, and a voltage for storing the value of the smoothed voltage corresponding to the cycle. The storage unit, the position estimation voltage application unit that holds the motor voltage applied to the brushless DC motor, and the time from when the smoothing voltage is output by the smoothing circuit to when the smoothing voltage is output to the brushless DC motor via the inverter circuit. , A delay time storage unit that stores a delay time that is a difference between a time from when the smoothing voltage is output by the smoothing circuit to when the duty is output to the inverter circuit based on the smoothing voltage, and a start time of the brushless DC motor. The value of the smoothed voltage output from the smoothing circuit is compared with the value of the smoothed voltage one cycle before stored in the voltage storage unit. If they match, the value of the smoothed voltage one cycle before stored in the voltage storage unit. The comparison/determination unit that outputs the stored smoothed voltage value later than the delay time, and the duty based on the motor voltage input from the position estimation voltage application unit and the smoothed voltage value input from the comparison determination unit. And a PWM output unit for adjusting and outputting to the inverter circuit.

  Further, the brushless DC motor voltage control device according to the present invention includes a current detection unit that detects a motor current flowing through the brushless DC motor, and a position of a rotor that configures the brushless DC motor based on the current value detected by the current detection unit. And a starting position estimating unit for estimating

  As a result, the brushless DC motor voltage control device can suppress the fluctuation of the smoothing voltage and accurately apply the motor voltage to the winding of the motor even if the capacity of the capacitor of the smoothing circuit is small. The accuracy of detection and position estimation of the rotor at the time of startup can be improved. Therefore, it is possible to realize a brushless DC motor voltage control device that can be downsized at low cost and can suppress failure in startup.

  When the value of the smoothed voltage output from the smoothing circuit does not match the value of the smoothed voltage stored one cycle before stored in the voltage storage unit when the brushless DC motor is started, the comparison and determination unit performs PWM until the values match. Wait for output to the output section.

  As a result, the brushless DC motor voltage control device waits until the AC voltage becomes constant even if the AC voltage temporarily fluctuates and the smoothed voltage fluctuates accordingly. That is, since the voltage is applied to the brushless DC motor only when the AC voltage is stable, it is possible to accurately estimate the position of the rotor at the time of startup and to suppress failure of startup, which is highly reliable brushless DC motor voltage control. A device can be provided.

  Further, the brushless DC motor voltage control device according to the present invention is based on a blower fan connected to the brushless DC motor, a current detection unit that detects a motor current flowing through the brushless DC motor, and a motor current detected by the current detection unit. Current detecting section for detecting the magnitude of the motor current and the position and speed of the rotor constituting the brushless DC motor, a target air volume storing section for storing a target air volume which is an air volume to be blown by the blower fan, and a current converting section. An air volume calculation unit that uses the magnitude of the motor current and the speed of the rotor detected to calculate the air volume being blown by the blower fan and compares it with the target air volume to determine the rotor speed for achieving the target air volume. And a motor voltage controller that determines the motor voltage to be applied to the brushless DC motor based on the rotor position detected by the current converter and the rotor speed determined by the air volume calculator. Then, the PWM output unit adjusts the duty based on the motor voltage determined by the motor voltage control unit and the value of the smoothed voltage output by the comparison determination unit, and outputs the duty to the inverter circuit.

  Accordingly, the brushless DC motor voltage control device can adjust the actual air volume blown by the blower fan to the target air volume by adjusting the speed of the rotor during driving.

  Further, the comparison/determination unit outputs the smoothing circuit when the value of the smoothing voltage output by the smoothing circuit does not match the value of the smoothing voltage stored in the voltage storage unit one cycle before when the brushless DC motor is driven. And outputs the value of the smoothed voltage to the PWM output unit.

  Accordingly, the brushless DC motor voltage control device can secure the air volume without stopping the device.

  The smoothing circuit is a brushless DC motor voltage control device that is a valley fill circuit.

  As a result, a brushless DC motor voltage control device having a high power factor can be realized. Further, even when the smoothed voltage of the valley fill circuit fluctuates, the fluctuation of the smoothed voltage can be suppressed and the motor voltage can be accurately applied to the winding of the motor. Therefore, a minute change in the motor current can be detected and the rotor at start-up can be detected. The accuracy of position estimation can be improved. Therefore, it is possible to realize a brushless DC motor voltage control device that can be downsized at low cost.

  Further, the blower device of the present invention is equipped with the brushless DC motor voltage control device of the present invention.

  As a result, even when a blower fan such as a range hood is large and heavy, the position of the rotor can be accurately detected at the time of startup, so that the rotor can be quickly started and hot air smoke, steam, and the like can be quickly discharged to the outside of the room. In addition, since the air volume can be adjusted to the target air volume during driving, excessive air volume does not increase the power consumption and the room temperature is not excessively discharged, and the power can be saved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention. In addition, the same reference numerals are given to the same portions throughout the drawings, and the second and subsequent explanations are omitted. Further, in the drawings to be written, the description of the details of each part not directly related to the present invention is omitted.

  It should be noted that throughout the present specification, "start-up" is a process of estimating the position of the rotor, and refers to the timing immediately before starting to rotate the rotor in a stopped state. Further, the process at the time of starting can be a process of a preparatory stage before starting the rotational start.

(Embodiment 1)
FIG. 16A is an explanatory view of a range hood equipped with a brushless DC motor voltage control device according to a conventional example as seen from a side surface. The range hood 119 includes the brushless DC motor 102, the circuit case 125, the filter 140, and the hood 141 inside the cabinet 126. The circuit case 125 contains a brushless DC motor voltage control device according to a conventional example. A blower fan 122 is attached to the brushless DC motor 102, and the blower fan 122 is rotated by being driven by the brushless DC motor 102. The hood 141 and the filter 140 are attached to the lower portion of the range hood 119.

  FIG. 16B is an explanatory diagram of the installed state of the range hood 119 shown in FIG. 16A. By installing as shown in FIG. 16B, hot air, smoke, steam, etc. generated when cooking in the kitchen are filtered from the central portion of the hood 141 by the rotation of the blower fan 122 attached to the brushless DC motor 102. It is taken into the cabinet 126 through 140.

  The hot air, smoke, steam and the like taken into the cabinet 126 are further discharged to the outside through the exhaust port 123 provided in the outer wall 124 by the rotation of the blower fan 122.

  First, the configuration of the brushless DC motor voltage control device according to the present embodiment will be described with reference to FIG. FIG. 1 is a functional block diagram of a brushless DC motor voltage control device 20a according to the first embodiment.

  The brushless DC motor voltage control device 20a is electrically connected to the AC power supply 12 and the brushless DC motor 2.

  The AC power supply 12 supplies a voltage to the brushless DC motor voltage control device 20a via, for example, an outlet in the home.

  The brushless DC motor 2 includes a rotor 4 having a magnet on its surface, and a winding 3 wound around a stator core. The rotor 4 is driven to rotate by applying a voltage to the winding 3. To do. For example, a fan or the like is connected to the rotor 4, and the fan can be rotationally driven to realize, for example, the function of a blower. Note that further details of the brushless DC motor 2 are omitted because they are not directly related to the present invention.

  The brushless DC motor voltage control device 20a includes a rectifier circuit 13, a smoothing circuit 14, an inverter circuit 1, a voltage divider 15, a current detector 5, and a controller 21a.

  The rectifier circuit 13 rectifies the AC voltage supplied from the AC power supply 12, converts it into a DC voltage, and outputs the obtained DC voltage to the smoothing circuit 14.

  The smoothing circuit 14 smoothes the DC voltage input from the rectifier circuit 13 and outputs the obtained smoothed voltage to the inverter circuit 1 and the voltage dividing unit 15. A specific component of the smoothing circuit 14 is a capacitor.

  The inverter circuit 1 PWM-controls the winding 3 of the brushless DC motor 2 based on the smoothed voltage input from the smoothing circuit 14 and the duty input from a PWM output unit 16 which will be described later and forms the control unit 21a. Apply a smooth voltage. The inverter circuit 1 has a three-phase bridge configuration including U, V, and W phases. Each switching element Q1, Q2, Q3 forming a three-phase bridge composed of U, V, W phases is an upper arm switching element of U, V, W phase, respectively. Similarly, the switching elements Q4, Q5, Q6 are lower arm switching elements of U, V, W phases, respectively. The winding 3 of the brushless DC motor 2 also has a configuration of a three-phase winding including windings Lu, Lv, and Lw, and is electrically connected to the corresponding arm switching element.

  The voltage dividing unit 15 divides the smoothed voltage input from the smoothing circuit 14 and outputs a smoothed voltage that is lower than the smoothed voltage input from the smoothing circuit 14 to the control unit 21a. The voltage dividing unit 15 is specifically configured by a resistor, and the smoothing voltage is stepped down by the resistor connected in series.

  The current detection unit 5 is electrically connected between the switching elements Q4, Q5, Q6 of the inverter circuit 1 and the ground of the brushless DC motor voltage control device 20a, and the winding Lu of each phase of the brushless DC motor 2 is The current flowing through Lv and Lw is detected. The current detection unit 5 is specifically composed of three shunt resistors Ru, Rv, and Rw.

  The control unit 21a includes a voltage holding unit 8, a cycle detection unit 6, a voltage storage unit 7, a comparison determination unit 9, a PWM output unit 16, a delay time storage unit 17, a start position estimation unit 10, and a position. The estimated voltage applying unit 11 is provided.

  Here, the problem of voltage fluctuation when smoothing an AC voltage to obtain a smooth voltage will be described.

  FIG. 2A is a diagram showing an example of an AC voltage. FIG. 2B is a diagram showing an example of a smoothed voltage obtained by rectifying and smoothing an AC voltage. The voltage fluctuation X of the smoothed voltage shown in FIG. 2B is influenced by the capacity of the capacitor used in the smoothing circuit 14, and the larger the capacity of the capacitor, the smaller the voltage fluctuation X tends to be. Generally, the larger the capacity of the capacitor, the larger the size of the capacitor, and the size of the capacitor used in the smoothing circuit 14 occupies a large volume in the circuit. That is, one of the methods for downsizing the brushless DC motor voltage control device 20a is to reduce the size of the capacitor used in the smoothing circuit 14. However, if the size of the capacitor is reduced, the capacitance of the capacitor also decreases, and the voltage fluctuation X increases. As described above, the inverter circuit 1 applies the pulsed voltage to the brushless DC motor 2 based on the smoothed voltage input from the smoothing circuit 14 and the duty input from the PWM output unit 16. That is, when the voltage fluctuation X of the smoothed voltage increases, the fluctuation of the pulsed voltage output from the inverter circuit 1 to the brushless DC motor 2 also increases. When the voltage fluctuation increases, it becomes difficult to detect a minute change in the motor current due to the saturation of the iron core forming the brushless DC motor 2, and the position of the rotor 4 cannot be accurately estimated.

  Therefore, the control unit 21a suppresses the voltage fluctuation X of the smoothed voltage. Hereinafter, processing of each unit included in the control unit 21a will be described with reference to the drawings.

  The voltage holding unit 8 holds (stores) the smoothed voltage input from the voltage dividing unit 15 for each PWM control. Here, “each PWM control” means one step of processing of the circuit during PWM control.

  The cycle detection unit 6 detects the cycle of fluctuations in the smoothed voltage from the value of the smoothed voltage held in the voltage holding unit 8. This cycle matches the cycle of the voltage fluctuation X of the smoothed voltage that the smoothing circuit 14 outputs to the inverter circuit 1.

  The smoothed voltage held by the voltage holding unit 8 and the method by which the cycle detection unit 6 detects the cycle of fluctuations in the smoothed voltage will be described in detail with reference to FIG. FIG. 3 is a diagram showing a method in which the cycle detection unit 6 detects the cycle of the fluctuation of the smoothed voltage from the value of the smoothed voltage held by the voltage holding unit 8. An image of the smoothed voltage held by the voltage holding unit 8 is shown in the upper part of FIG. The smoothed voltage acquired from the voltage dividing unit 15 is stored in the voltage holding unit 8 in association with an elapsed time from a predetermined starting point and a voltage value for each passage of the elapsed time. The unit of the elapsed time is specifically the same as or shorter than the cycle of the PWM control. The period is detected, for example, as follows. That is, as shown in the upper part of FIG. 3, the cycle detection unit 6 determines, based on the value of the smoothed voltage held in the voltage holding unit 8, a value that is ½ of the sum of the maximum voltage value and the minimum voltage value of the smoothed voltage. Is the threshold. When the value of the smoothed voltage is larger than the threshold value, it is defined as "H", and when it is smaller, it is defined as "L". Here, the cycle detection unit 6 detects the time of switching from "L" to "H" to the next switching from "L" to "H" as one cycle.

  The voltage storage unit 7 stores the value of the smoothed voltage for at least one cycle in association with the cycle of the smoothed voltage detected by the cycle detection unit 6.

  The smoothed voltage stored in the voltage storage unit 7 will be described with reference to FIG. FIG. 4 is a diagram showing the value of the smoothed voltage for one cycle stored in the voltage storage unit 7. The right end is the latest smoothed voltage value, and the left end is the smoothed voltage value one cycle before. The value of the smoothed voltage for one cycle stored in the voltage storage unit 7 is updated for each PWM control, and the latest value of the smoothed voltage and the value of the smoothed voltage one cycle before are also updated accordingly. Although only the value of the smoothed voltage for one cycle is shown in FIG. 4, there is no problem in storing more than one cycle.

  The delay time storage unit 17 stores the delay time. The delay time is predetermined by the circuit and is stored in the delay time storage unit 17 as a fixed value. The details of the delay time will be described later.

  When the brushless DC motor 2 is activated, the comparison/determination unit 9 receives the latest value of the smoothing voltage output from the smoothing circuit 14 via the voltage dividing unit 15 and one cycle before input from the voltage storage unit 7. And the smoothed voltage value of. If they match, the value of the smoothed voltage stored later than the one cycle stored in the voltage storage unit 7 by the delay time stored in the delay time storage unit 17 is output to the PWM output unit 16. Here, the value of the smoothed voltage stored late is, in other words, the value of the smoothed voltage at the time point when the delay time has elapsed from the time point one cycle before.

  The PWM output unit 16 adjusts the duty of the PWM control based on the value of the smoothed voltage input from the comparison determination unit 9 and the motor voltage VM input from the position estimation voltage application unit 11 described later, and the inverter circuit 1 Output to. Details will be described later.

  The starting position estimating unit 10 determines whether or not the brushless DC motor 2 is starting, and at the time of starting, the motor current flowing through the winding 3 based on the voltage applied from the inverter circuit 1 is passed through the current detecting unit 5 via the current detecting unit 5. To get. Details will be described later.

  The position estimation voltage application unit 11 transmits the motor voltage VM stored as a predetermined parameter to the PWM output unit 16 when the brushless DC motor 2 is activated. The PWM output unit 16 calculates the energization time t of each switching element based on the motor voltage VM and outputs the duty to the inverter circuit 1. Details will be described later.

  Here, the delay time stored in the delay time storage unit 17 will be described with reference to FIG. FIG. 5 is a diagram showing details of the delay time according to the first embodiment. Here, if the frequency of the alternating current is 50 Hz, one cycle of the smoothing voltage is 10 ms. On the other hand, in the present embodiment, the PWM control cycle is 62.5 μs (16 kHz). The PWM control cycle is remarkably short with respect to one cycle of the smoothed voltage, and is therefore shown in an enlarged view.

  The voltage holding unit 8, the comparison/decision unit 9, and the PWM output unit 16 perform the following operations A, B, and C for each cycle of the PWM control by the control unit 21a.

  A: The voltage holding unit 8 holds the value of the smoothed voltage acquired from the voltage dividing unit 15.

  B: The comparison and determination section 9 compares the latest smoothed voltage value input via the voltage dividing section 15 with the smoothed voltage value one cycle before input from the voltage storage section 7, and compares the latest smoothed voltage value with the inverter circuit. The value of the smoothed voltage input to 1 is determined, and the determined smoothed voltage is output to the PWM output unit 16.

  C: The PWM output unit 16 adjusts the duty of the PWM control based on the value of the smoothed voltage input from the comparison determination unit 9 and the motor voltage VM input from the position estimation voltage application unit 11, that is, the energization time t. Is calculated and the duty is output to the inverter circuit 1.

  That is, the sum of the processing times of A, B, and C is “the time until the duty is output to the inverter circuit 1 based on the smoothed voltage output from the smoothing circuit 14”. The delay time is obtained by subtracting "the time until the smoothed voltage output by the smoothing circuit 14 is output to the brushless DC motor 2 via the inverter circuit 1" from "the sum of the processing times of A, B, and C". It is a value. When the delay time occurs, the voltage difference shown in FIG. 5 occurs.

  Next, the process in which the PWM output unit 16 adjusts the duty of PWM control and outputs the adjusted duty to the inverter circuit 1 will be described.

  Here, the comparison process performed by the comparison determination unit 9 will be described with reference to FIG. FIG. 6 is a schematic diagram in which the comparison/determination unit 9 determines a smoothed voltage that is delayed by a delay time compared to one cycle before.

  The comparison/determination unit 9 obtains the latest smoothed voltage value Va acquired from the voltage storage unit 7 or the smoothing circuit 14 via the voltage holding unit 8 and the latest smoothed voltage stored in the voltage storage unit 7. The value of the smoothed voltage value Vb of one cycle before is compared. Normally, if the AC voltage is stable, the smoothed voltage value Va and the smoothed voltage value Vb match. Then, when the comparison/judgment unit 9 confirms that they match with each other, the comparison result of the delay time stored in the delay time storage unit 17 is calculated from the value of the smoothed voltage value Vb stored in the voltage storage unit 7 one cycle before. The value Vh of the smoothed voltage stored later by the amount is acquired and output to the PWM output unit 16.

  The PWM output unit 16 uses the smoothed voltage value Vh, the PWM control cycle T (constant), and the motor voltage VM obtained from the position estimation voltage application unit 11 in order to output the duty to the inverter circuit 1. , The energization time t required for the PWM control is calculated from the equation (1). As described above, the motor voltage VM is a value stored in the position estimation voltage applying unit 11 as a predetermined parameter, that is, a constant value, and is not affected by the delay time.

Energization time t=VM×T/Vh... Equation (1)
As shown in Expression (1), the energization time t required for the PWM control is determined by the magnitude of the smoothed voltage value Vh.

  7A and 7B are diagrams showing the waveform of the duty output by the PWM output unit according to the first embodiment. 7A shows the case where the smoothed voltage value Vh is lower than the threshold value, and FIG. 7B shows the case where the smoothed voltage value Vh is higher than the threshold value. As shown in FIGS. 7A and 7B, in the inverter circuit 1, the energization time is long when the smoothed voltage value Vh is lower than the threshold value, and the energized time is short when the smoothed voltage value Vh is higher than the threshold value. The duty is controlled so that That is, the duty is controlled so that the value of the motor voltage VM is constant regardless of the value of the smoothed voltage Vh.

  As a result, the pulse voltage applied from the inverter circuit 1 to the winding 3 is controlled by the controller 21a to be equal to the motor voltage VM.

  Next, a method of estimating the position of the rotor 4 will be described with reference to FIGS. 8A and 8B.

  FIG. 8A is a diagram showing voltages applied to the windings Lu, Lv, and Lw when the motor voltage VM is applied to the brushless DC motor 2 in the brushless DC motor voltage control device 20a according to the first embodiment. .. FIG. 8A shows that when the rotor 4 is at the positions of 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees with reference to the U-phase winding Lu, the winding 3 is pulsed. The pulsed motor voltage applied to the windings Lu, Lv, and Lw of each phase when the motor voltage VM is applied is shown. The magnitude of the pulsed voltage fluctuates under the influence of the voltage fluctuation X of the smoothed voltage shown in FIG. 2B.

  FIG. 8B is a diagram showing currents flowing through windings of respective phases of the motor at the time of FIG. 8A. FIG. 8B shows the motor current flowing through the shunts Ru, Rv, Rw of the current detector 5 when the pulsed voltage VM is actually applied to the U-phase, V-phase, and W-phase windings Lu, Lv, Lw. An example is shown. At the time of startup, the smoothing voltage value Vh stored late by the delay time is output from the comparison and determination unit 9 to the PWM output unit 16 and is reflected in the duty. Therefore, the voltage change of the smoothed voltage input to the inverter circuit 1 is suppressed by the PWM control, and the motor voltage VM of a certain magnitude can be applied in a pulse form. That is, as shown in FIG. 8A, even if the pulse-shaped voltage output from the inverter circuit 1 is not uniform in shape, the voltage applied to the windings Lu, Lv, and Lw is a delay of the smoothed voltage on the circuit. In consideration of the above, the control is performed so that the motor voltage VM becomes constant. Therefore, the starting position estimation unit 10 can determine the minute difference in the motor current.

  A procedure for estimating the position of the rotor 4 with high accuracy by the activation position estimation unit 10 discriminating a minute difference in the motor current will be specifically described. The motor current flows at each angle with reference to the U-phase winding Lu, and when the magnetic poles of the magnetic flux generated from the motor current and the magnetic poles of the magnetic flux generated from the surface magnet of the rotor 4 match, the iron core The saturated motor current increases. If they do not match, the iron core is not saturated and the motor current does not increase. In the example of FIG. 8B, the motor current detected by the current detection unit 5 is larger than the other angles at the position of 90 degrees and is the maximum. The starting position estimating unit 10 compares the motor currents of the respective phases at the respective angles, detects that the 90-degree V-phase and W-phase motor currents are larger than the other currents, and is the maximum. It can be estimated that the position of 4 is at the position of 90 degrees. The determination of such a minute difference in motor current is realized by considering the delay time on the circuit. That is, when the delay time is not taken into consideration, the voltage change in the delay time of the smoothed voltage affects the value of the motor current, so the values of the motor current shown in FIG. 8B become non-uniform, and the maximum value is accurately determined. You cannot do it. In the present embodiment, since the delay time of the smoothed voltage is taken into consideration at the time of startup, it is possible to accurately specify the position of the rotor 4.

  Next, the operation of the brushless DC motor voltage control device 20a according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating the operation of brushless DC motor voltage control device 20a according to the first embodiment. FIG. 9 shows a flowchart from the voltage holding unit 8 holding the smoothed voltage to the starting position estimating unit 10 estimating the position of the rotor 4. The processing described below is performed for each step in PWM control.

  First, the voltage holding unit 8 holds the value of the smoothed voltage input from the voltage dividing unit 15 (S1).

  Next, the cycle detection unit 6 detects the cycle of voltage fluctuation of the smoothed voltage held by the voltage holding unit 8 (S2).

  Subsequently, the voltage storage unit 7 stores the value of the smoothed voltage for one cycle held by the cycle detection unit 6 (S3).

  Then, the starting position estimating unit 10 determines whether or not it is at the time of starting, and at the time of starting, proceeds to the process of the next comparison and determination unit 9 (S5). When stopped or during operation, the process proceeds to the end (S11) without doing anything (S4).

  Next, the comparison and determination unit 9 compares the smoothed voltage value Vb one cycle before and the latest smoothed voltage value Va, and if they match, determines the smoothing voltage value of the next comparison and determination unit 9 (S6). Proceed (S5).

  Subsequently, the comparison and determination unit 9 outputs to the PWM output unit 16 the smoothed voltage value Vh stored later by the delay time stored in the delay time storage unit 17 than one cycle before stored in the voltage storage unit 7 ( S6).

  Subsequently, the PWM output unit 16 calculates the duty of the PWM control based on the smoothed voltage value Vh input from the comparison determination unit 9 and the motor voltage VM input from the position estimation voltage application unit 11 to calculate the duty ratio of the inverter circuit 1. (S7).

  Subsequently, the inverter circuit 1 performs PWM control of the smoothed voltage input from the smoothing circuit 14 using the duty output from the PWM output unit 16, and applies a pulsed voltage to the windings Lu, Lv, Lw of each phase. Then, the motor current is supplied (S8).

  Then, the starting position estimation unit 10 receives the magnitude of the motor current from the current detection unit 5 (S9).

  Then, the starting position estimating unit 10 compares the motor currents flowing through the windings of the respective phases and estimates the position of the rotor 4 (S10).

  After estimating the position of the rotor 4, a normal starting process is performed based on the position. Since the position of the rotor 4 is accurately estimated, it is possible to suppress the start failure.

  With the above configuration, the PWM output unit 16 calculates the duty of the PWM control from the smoothed voltage at the time point delayed by the delay time from the previous cycle. As a result, the inverter circuit 1 can correct the smoothed voltage difference caused by the delay time and accurately output the motor voltage VM. In addition, the starting position estimation unit 10 can accurately determine a minute change in the motor current and accurately estimate the position of the rotor 4. That is, even if the capacity of the capacitor of the smoothing circuit 14 is small, the smoothing voltage can be corrected and the motor voltage VM can be accurately applied to the winding 3 of the brushless DC motor 2. Therefore, a minute change in the motor current can be accurately detected, The position estimation accuracy of the rotor 4 at the time of startup can be improved. Therefore, it is possible to realize the brushless DC motor voltage control device 20a that can be downsized at low cost.

  Although the cycle detection unit 6 detects one cycle from the voltage change of the smoothed voltage, it may detect one cycle directly from the alternating current.

  As for the rotor position estimation method at the time of startup, the method of applying the pulsed motor voltage six times at 30, 90, 150, 210, 270 and 330 degrees has been described. The position may be estimated by applying an angle or a number of times.

(Embodiment 2)
In the present embodiment, the points of processing of the comparison/determination unit 9 different from those of the first embodiment will be described. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

  In the first embodiment, the latest smoothed voltage value Va output by the smoothing circuit 14 when the brushless DC motor 2 is started and the smoothed voltage stored in the voltage storage unit 7 and which is one cycle before are compared with each other. The description has been made assuming that the value Vb matches. However, when the AC power supply is unstable, the voltage fluctuation Y shown in FIG. The causes of the voltage fluctuation Y are transient, such as startup of the AC power supply, voltage fluctuation of the AC power supply, noise application of lightning surge, and the like. In the present embodiment, the comparison/determination unit 9 compares the latest smoothed voltage value Va with the smoothed voltage value Vb one cycle before, and if they do not match, the PWM output unit 16 outputs until they match. Wait for output.

  Further, the comparison/determination unit 9 according to the present embodiment compares the smoothed voltage value Vb one cycle before and the latest smoothed voltage value Va, as shown in FIG. Instead, it is set to proceed to the end (S11).

  With the above-described configuration, the brushless DC motor voltage control device 20a according to the present embodiment waits until the smoothing voltage periodically changes and recovers from the inverter circuit 1 even if the AC voltage temporarily changes. The voltage is accurately output to the brushless DC motor 2, and a minute change in the motor current can be accurately detected. That is, since the voltage is applied to the winding 3 of the brushless DC motor 2 only when the AC voltage is stable, the accuracy of rotor position estimation at the time of startup can be improved and startup failure can be suppressed with high reliability. The brushless DC motor voltage control device 20a can be obtained.

(Embodiment 3)
In the present embodiment, the smoothing circuit 14 will be described by referring to differences from the first and second embodiments. The same components as those in the first and second embodiments are designated by the same reference numerals and detailed description thereof will be omitted.

  In the first and second embodiments, the smoothing circuit 14 includes one smoothing capacitor. In the present embodiment, an example in which the valley fill circuit 18 is used as the smoothing circuit 14 will be described.

  In the present embodiment, the valley fill circuit 18 includes a smoothing capacitor, a diode, and a resistor.

  FIG. 10 is a functional block diagram of the brushless DC motor voltage control device 20a according to the third embodiment. As shown in FIG. 10, the brushless DC motor voltage control device 20a according to the present embodiment is obtained by replacing the smoothing circuit 14 of FIG. 1 with a valley fill circuit 18. In this configuration, the valley fill circuit 18 includes two smoothing capacitors, and the time during which the current flows through the two smoothing capacitors, the so-called charging time, is longer than that when only one smoothing capacitor is used. That is, the current waveform of the AC power supply 12 is closer to a sine wave than in the first and second embodiments. As a result, the power factor can be improved without changing other configurations.

  FIG. 11A is a diagram showing an example of an AC voltage. FIG. 11B shows an example of a smoothed voltage obtained by rectifying and smoothing an AC voltage using the valley fill circuit 18.

  As shown in FIGS. 11A and 11B, even if the valley fill circuit 18 is used for the smoothing circuit 14, the smoothed voltage output from the valley fill circuit 18 has a periodic large fluctuation of the AC power supply. Specifically, the smoothed voltage output from the valley fill circuit 18 changes to 1/2 of the maximum voltage Vmax. However, as described in the first embodiment, the voltage input to the brushless DC motor 2 is set to be constant by the control unit 21a even if the smoothed voltage changes.

  With the above configuration, even if the valley fill circuit 18 is used for the smoothing circuit 14, the fluctuation of the smoothing voltage can be suppressed by the same method as in the first and second embodiments, and the accuracy of the position estimation of the rotor 4 at the time of startup can be improved. it can. That is, it is possible to provide the brushless DC motor voltage control device 20a that has a high power factor due to the power factor improving characteristic of the valley fill circuit 18 and that can suppress failure in startup.

  As an example of the valley fill circuit 18, the capacitor having two stages is shown, but the capacitor may have three stages.

(Embodiment 4)
In the present embodiment, an air blower equipped with the brushless DC motor voltage control device 20a according to the first to third embodiments will be described. The same components as those in the first to third embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 12 is a diagram showing a range hood according to the fourth embodiment. The range hood 19 includes a brushless DC motor 2, a circuit case 25, a filter 40, and a hood 41 inside a cabinet 26. The circuit case 25 contains the brushless DC motor voltage control device 20a according to the first to third embodiments. A blower fan 22 is attached to the brushless DC motor 2. The filter 40 and the hood 41 are structures attached to the lower portion of the range hood 19.

  Hot air, smoke, steam and the like generated when cooking in the kitchen are discharged from the central portion of the hood 41 through the filter 40 to the outside by the rotation of the blower fan 22 attached to the brushless DC motor 2.

  The brushless DC motor 2 is started by a brushless DC motor voltage control device 20a built in the circuit case 25.

  As a result, the brushless DC motor 2 can be started with sufficient torque because the position of the rotor 4 is accurately estimated at the time of starting and a voltage according to the position of the rotor 4 is applied. Therefore, even when a blower fan such as a range hood is large and heavy, it is possible to provide a blower that can be quickly activated and quickly discharge hot air, smoke, steam, and the like.

(Embodiment 5)
In the present embodiment, the control unit 21a will be described by referring to differences from the first to fourth embodiments. The same components as those in the first to fourth embodiments are designated by the same reference numerals and detailed description thereof will be omitted.

  FIG. 13 is a block diagram of a brushless DC motor voltage control device 20b according to the fifth embodiment. As shown in FIG. 13, the brushless DC motor voltage control device 20b includes a rectifier circuit 13, a smoothing circuit 14, an inverter circuit 1, a voltage divider 15, a current detector 5, and a controller 21b. ..

  The control unit 21b replaces the starting position estimation unit 10 and the position estimation voltage application unit 11 included in the control unit 21a of the brushless DC motor voltage control device 20a, and replaces the current conversion unit 27, the target air volume storage unit 28, and the air volume. The calculation unit 29 and the motor voltage control unit 30 are provided.

  The current converter 27 acquires the motor current flowing through the winding 3 via the current detector 5. Then, the current converter 27 detects the magnitude of the motor current, the position θ and the speed ω of the rotor 4 based on the acquired motor current. The position θ and the speed ω of the rotor 4 are detected by conversion based on the so-called sensorless sine wave driving method. The current converter 27 outputs the magnitude and speed ω of the motor current to the target air volume storage 28 and the position θ of the rotor 4 to the motor voltage controller 30.

  The target air volume storage unit 28 stores a predetermined target air volume Qs, which is the air volume to be blown from the central portion of the hood 41 through the filter 40 by the rotation of the blower fan 22. The target air volume storage unit 28 outputs the target air volume Qs to the air volume calculation unit 29.

  The air volume calculation unit 29 determines whether or not the brushless DC motor 2 is driven, and at the time of driving, the blower fan 22 is actually used by using the magnitude of the motor current input from the current conversion unit 27 and the speed ω of the rotor 4. The air volume Q that is being blown to is calculated. Then, the air volume calculation unit 29 compares the target air volume Qs input from the target air volume storage unit 28 with the air volume Q to determine the target speed ωs, and outputs the obtained target speed ωs to the motor voltage control unit 30. That is, when the air volume is determined to be large, the air volume calculation unit 29 decreases the speed ω so that the air volume is small, and when the air volume is small, the air volume is increased to increase the air volume. Further, the air volume calculation unit 29 does not perform any processing when the brushless DC motor 2 is stopped or started. The term “during driving” refers to a state in which the rotor continues to rotate after being activated, and a blower fan attached to the rotor is blowing air.

  The motor voltage control unit 30 outputs the position θ of the rotor 4 input from the current conversion unit 27 and the target motor voltage VMS determined based on the target speed ωs input from the air volume calculation unit 29 to the PWM output unit. Output to 16.

  The PWM output unit 16 adjusts the duty of PWM control based on the value of the smoothed voltage input from the comparison determination unit 9 and the motor voltage VMS input from the motor voltage control unit 30, and outputs the duty to the inverter circuit 1.

  Here, the target motor voltage VMS output by the motor voltage control unit 30 is a voltage in which the duty under PWM control is a sine wave.

  14A and 14B, the PWM output unit 16 adjusts the duty of PWM control based on the value of the smoothed voltage input from the comparison determination unit 9 and the target motor voltage VMS input from the motor voltage control unit 30. An example of the motor current with and without adjustment is shown. FIG. 14A is a diagram showing a case where the duty is adjusted. As shown in FIG. 14A, the duty of the PWM control is adjusted based on the value of the smoothed voltage input from the comparison/determination unit 9, so that the motor current has a constant magnitude. FIG. 14B is a diagram showing a case where the duty is not adjusted. In this case, as shown in FIG. 14B, the magnitude of the motor current is constantly changing. The current converter 27 acquires a constant magnitude motor current output from the inverter circuit 1, and detects the magnitude of the motor current and the rotor speed ω. The air volume calculation unit 29 calculates the air volume Q generated from the blower fan 22 using the magnitude of the motor current output by the current conversion unit 27 and the speed ω of the rotor 4.

  Next, the operation of the brushless DC motor voltage control device 20b according to the present embodiment will be described with reference to FIG. FIG. 15 is a flowchart explaining the operation of the brushless DC motor voltage control device 20b according to the fifth embodiment. FIG. 15 shows a flowchart from the voltage holding unit 8 holding the smoothed voltage to the PWM output unit 16 outputting the duty. The same operations as those in FIG. 9 are designated by the same reference numerals, and detailed description thereof will be omitted. The processing described below is performed for each step in PWM control.

  First, the voltage holding unit 8 holds the value of the smoothed voltage input from the voltage dividing unit 15 (S1).

  Next, the cycle detection unit 6 detects the cycle of voltage fluctuation of the smoothed voltage held by the voltage holding unit 8 (S2).

  Subsequently, the voltage storage unit 7 stores the value of the smoothed voltage for one cycle held by the cycle detection unit 6 (S3).

  Subsequently, the air volume calculation unit 29 determines whether or not it is driving, and when driving, proceeds to the next process of the current conversion unit 27 (S22). At the time of stopping or starting, the operation ends without doing anything (S11) (S21).

  Next, the current converter 27 detects the magnitude of the motor current, the position θ and the speed ω of the rotor 4 from the motor current flowing through the winding 3 based on the applied voltage (S22).

  Subsequently, the air volume calculation unit 29 calculates the air volume Q generated from the blower fan 22 using the magnitude of the motor current and the speed ω of the rotor 4. Then, the air volume calculation unit 29 compares the target air volume Qs input from the target air volume storage unit 28 with the air volume Q to determine the target speed ωs (S23).

  Subsequently, the motor voltage control unit 30 determines the target motor voltage VMS based on the position θ of the rotor 4 input from the current conversion unit 27 and the target speed ωs input from the air volume calculation unit 29, and the PWM output unit It outputs to 16 (S24).

  Next, the comparison/judgment unit 9 compares the smoothed voltage value Vb one cycle before and the latest smoothed voltage value Va, and if they match, determines the smoothing voltage value of the next comparison/judgment unit 9 (S6). (S5).

  Subsequently, the comparison and determination unit 9 outputs to the PWM output unit 16 the smoothed voltage value Vh stored later by the delay time stored in the delay time storage unit 17 than one cycle before stored in the voltage storage unit 7 ( S6).

  Subsequently, the PWM output unit 16 adjusts the duty of the PWM control based on the smoothed voltage value Vh input from the comparison/determination unit 9 and the target motor voltage VMS input from the motor voltage control unit 30, and the inverter circuit 1 (S7).

  With the above configuration, the brushless DC motor voltage control device 20b according to the present embodiment adjusts the speed ω of the rotor 4 at the time of driving so that the actual air volume Q blown from the blower fan 22 becomes the target air volume. It can be adjusted to Qs. Further, the brushless DC motor voltage control device 20b according to the present embodiment calculates the duty of the PWM control based on the smoothed voltage at the time point delayed by the delay time from the previous cycle. As a result, the inverter circuit 1 can correct the difference in smoothed voltage caused by the delay time and accurately output the target motor voltage VMS. Therefore, the current converter 27 can accurately detect the motor current via the current detector 5. The air volume Q is obtained by converting the motor current and using the magnitude of the motor current and the speed ω. That is, in the present embodiment, since the air volume Q is accurately calculated, it is possible to accurately adjust the actual air volume Q blown from the air blowing fan to the target air volume Qs.

  Although the air volume calculation unit 29 calculates the air volume Q using the motor current and the speed ω, the air volume may be calculated using, for example, the motor voltage instead of the speed ω.

  Further, although the current converter 27 detects the speed ω using the motor current, it may detect the speed ω using a signal from a magnetic sensor in the vicinity of the surface magnet applied to the rotor 4.

  Further, in the present embodiment, the valley fill circuit 18 may be used as the smoothing circuit 14. The description of the effects and the like when the valley fill circuit 18 is used is the same as that described in the third embodiment, and therefore will be omitted.

(Embodiment 6)
In the present embodiment, the points of processing of the comparison/determination unit 9 different from those of the fifth embodiment will be described.

  In the fifth embodiment, the latest smoothing voltage value Va output by the smoothing circuit 14 when the brushless DC motor 2 is driven and the smoothing voltage stored by the voltage storage unit 7 and compared with the previous smoothing voltage are compared. The description has been made assuming that the value Vb matches. However, as described in the second embodiment, when the AC power supply is unstable, there is a case where they do not match due to the voltage fluctuation Y in FIG. 2A. In the present embodiment, the comparison/determination unit 9 compares the latest smoothed voltage value Va with the smoothed voltage value Vb one cycle before, and if they do not match, the latest smoothed voltage value Va is determined by the PWM output unit. The output to 16 is made. The latest smoothed voltage value Va here is a smoothed voltage value that does not match the smoothed voltage Vb one cycle before.

  As a result, the air volume can be secured without stopping the device. After that, if the latest smoothed voltage value Va and the smoothed voltage value Vb one cycle before match, the comparison/determination unit 9 performs the normal operation as described in the fifth embodiment.

  Next, the comparison/determination unit 9 compares the latest smoothed voltage value Va with the smoothed voltage value Vb one cycle before, and the operation of the brushless DC motor voltage control device 20b when they do not match is shown in FIG. Explanations will be given with reference.

  As shown in FIG. 15, the comparison/determination unit 9 compares the latest smoothed voltage value Va with the smoothed voltage value Vb one cycle before, and if they do not match, the next smoothed voltage of the comparison/determination unit 9 is determined. The process proceeds to the process of determining the latest value of the smoothed voltage (S25) (S5).

  Then, the comparison and determination unit 9 determines the latest smoothed voltage value to be the smoothed voltage value Vh (S25).

  Subsequently, the PWM output unit 16 adjusts the duty of the PWM control based on the smoothed voltage value Vh input from the comparison/determination unit 9 and the target motor voltage VMS input from the motor voltage control unit 30, and the inverter circuit 1 (S7).

  With the above configuration, even if the AC voltage fluctuates temporarily, the air volume can be secured without stopping the motor, and when the AC voltage becomes normal, the motor voltage is output and the motor current is accurately measured. Can be detected. That is, it is possible to provide a highly reliable brushless DC motor voltage control device 20b that can keep the air volume substantially constant.

  Further, in the present embodiment, the valley fill circuit 18 may be used as the smoothing circuit 14. The description of the effects and the like when the valley fill circuit 18 is used is the same as that described in the third embodiment, and therefore will be omitted.

  INDUSTRIAL APPLICABILITY The voltage controller for a brushless DC motor according to the present invention can estimate the rotor position even if the capacitor is downsized, and is therefore useful as a voltage controller that needs to be downsized.

1 Inverter Circuit 2, 102 Brushless DC Motor 3, Lu, Lv, Lw Winding 4 Rotor 5 Current Detection Section 6 Cycle Detection Section 7 Voltage Storage Section 8 Voltage Holding Section 9 Comparison Judgment Section 10 Start Position Estimation Section 11 Position Estimated Voltage Applying unit 12 AC power supply 13 Rectifying circuit 14 Smoothing circuit 15 Voltage dividing unit 16 PWM output unit 17 Delay time storage unit 18 Valley fill circuit 19 Range hood 20a, 20b Brushless DC motor voltage control device 21a, 21b Control unit 22 Blower fan 25 Circuit case 26 Cabinet 27 Current conversion unit 28 Target air volume storage unit 29 Air volume calculation unit 30 Motor voltage control unit 40 Filter 41 Hood 119 Range hood 122 Blower fan 123 Exhaust outlet 124 Outer wall 125 Circuit case 126 Cabinet 140 Filter 141 Hood

Claims (6)

A rectifier circuit that rectifies AC voltage and converts it to DC voltage,
A smoothing circuit that smoothes the DC voltage and outputs a smoothed voltage;
An inverter circuit that PWM-controls the smoothed voltage that is input based on the input duty and supplies the smoothed voltage to a brushless DC motor;
A cycle detection unit that detects the cycle of fluctuations in the smoothed voltage,
A voltage storage unit that stores the value of the smoothed voltage in association with the cycle,
The time from the output of the smoothed voltage by the smoothing circuit to the output of the smoothed voltage to the brushless DC motor via the inverter circuit, and the smoothed voltage after the smoothing voltage is output by the smoothing circuit. A delay time storage unit that stores a delay time that is a difference between the time until the duty is output to the inverter circuit based on
A comparison and determination unit that outputs a stored smoothing voltage value that is later by the delay time than the smoothing voltage value stored in the voltage storage unit one cycle before when the brushless DC motor is activated;
A PWM output unit that outputs the duty to the inverter circuit;
A current detector for detecting a motor current flowing through the brushless DC motor;
A position estimation voltage applying section that holds a motor voltage to be applied to the brushless DC motor at startup,
A starting position estimating unit that estimates the position of the rotor that constitutes the brushless DC motor,
The PWM output section is
Smoothing stored later by the delay time than the value of the motor voltage at the time of startup input from the position estimation voltage application unit and the value of the smoothed voltage stored in the voltage storage unit input from the comparison and determination unit. The duty is adjusted based on the value of the voltage and output to the inverter circuit,
The inverter circuit is
A pulsed voltage corresponding to the adjusted duty is applied to the brushless DC motor when the rotor is stopped,
The current detector is
Detecting a motor current flowing through the brushless DC motor corresponding to the pulsed voltage,
The starting position estimating unit,
The current detection unit detects, based on the current value corresponding to the pulsed voltage, to estimate the position in a stopped state immediately before the rotor starts rotating,
Brushless DC motor voltage controller. The comparison and determination unit,
When the value of the smoothed voltage output by the smoothing circuit does not match the value of the smoothed voltage stored in the voltage storage unit one cycle before when the brushless DC motor is started, the PWM output unit is operated until the values match. The brushless DC motor voltage control device according to claim 1, which waits for the output of the brushless DC motor. A blower fan connected to the brushless DC motor,
A current detector for detecting a motor current flowing through the brushless DC motor;
A current converter that detects the magnitude of the motor current and the position and speed of the rotor that constitutes the brushless DC motor based on the motor current detected by the current detector;
A target air volume storage unit that stores a target air volume that is the air volume to be blown by the blower fan;
Using the magnitude of the motor current detected by the current converter and the speed of the rotor, the air volume blown by the air blowing fan is calculated and compared with the target air volume, and the rotor for achieving the target air volume is calculated. An air volume calculator that determines the speed of
A motor voltage controller that determines a motor voltage to be applied to the brushless DC motor based on the position of the rotor detected by the current converter and the speed of the rotor determined by the airflow calculator.
The PWM output section is
The brushless DC motor voltage control according to claim 1, wherein the duty is adjusted and output to the inverter circuit based on the motor voltage determined by the motor voltage control unit and the value of the smoothed voltage output by the comparison determination unit. apparatus. The comparison and determination unit,
When driving the brushless DC motor,
When the value of the smoothed voltage output by the smoothing circuit does not match the value of the smoothed voltage stored in the voltage storage unit one cycle before, the value of the smoothed voltage output by the smoothing circuit is sent to the PWM output unit. The brushless DC motor voltage control device according to claim 1, which outputs the voltage. The brushless DC motor voltage control device according to claim 1, wherein the smoothing circuit is a valley fill circuit. An air blower equipped with the brushless DC motor voltage controller according to claim 1.

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