Drive circuit and motor control method

Abstract

This invention provides a drive circuit that can improve the accuracy of determining whether a three-phase DC motor is locked. [Solution] The drive circuit 200 of the three-phase DC motor includes a control unit capable of controlling the bridge circuit 230 in a two-phase modulation manner. The control unit can switch between a current reduction section in which the duty cycle of the upper arms of the second and third phases is gradually reduced while the upper arm of the first phase and the lower arms of the second and third phases are fixed off and the lower arm of the first phase is fixed on; a high impedance section in which the arms of all phases are fixed off; and a current increase section in which the duty cycle of the upper arm of the second phase and the lower arm of the third phase is gradually increased while the upper arms of the first and third phases and the lower arm of the second phase are fixed off and the lower arm of the first phase is fixed on. The control unit receives a Hall signal S in the high impedance section. HALL If no change is detected, it is determined that the motor is locked.

Description

Technical Field

[0001] The present disclosure relates to a drive circuit and a motor control method.

Background Art

[0002] A drive circuit for a three-phase DC motor detects the position of the rotor of the three-phase DC motor based on a Hall signal from a Hall element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] The Hall signal output by the Hall element reflects information on the magnetic flux density corresponding to the position of the rotor. When a current for driving a three-phase DC motor is supplied from a drive circuit to a coil, leakage magnetic flux from the coil may occur. The Hall signal may also reflect information on this leakage magnetic flux from the coil. As a result, for example, even when the three-phase DC motor is locked by an external force, the Hall signal may change due to the influence of the leakage magnetic flux from the coil, and thus there has been a problem that the drive circuit may erroneously detect that the rotor is rotating.

[0005] [Summary] The present disclosure has been made in such a situation, and an exemplary object of one aspect thereof is to provide a drive circuit capable of improving the determination accuracy of whether a three-phase DC motor is locked.

[0006] One aspect of the present disclosure is a drive circuit. The drive circuit is a drive circuit for a three-phase DC motor, and includes a control unit that can control a bridge circuit connected to the three-phase DC motor in a two-phase modulation method based on a Hall signal indicating the position of the rotor of the three-phase DC motor. The control unit fixes the upper arm of the first phase and the lower arms of the second and third phases to off, fixes the lower arm of the first phase to on, and gradually decreases the duty ratios of the upper arms of the second and third phases in a current decrease section, a high impedance section that fixes all upper and lower arms of all phases to off after the current decrease section, and after the high impedance section, fixes the upper arms of the first and third phases and the lower arm of the second phase to off, fixes the lower arm of the first phase to on, and can switch to a current increase section that gradually increases the duty ratios of the upper arm of the second phase and the lower arm of the third phase. The control unit determines that the three-phase DC motor is locked when it does not detect a change in the Hall signal in the high impedance section.

[0007] Another aspect of the present disclosure is a motor control method. The motor control method is a motor control method for controlling a three-phase DC motor in a two-phase modulation method based on a Hall signal indicating the position of the rotor of the three-phase DC motor, and includes a first step of gradually decreasing the current while driving the three-phase DC motor with a sine wave, a second step of putting the three-phase DC motor in a high impedance state after the first step, and a third step of gradually increasing the current and driving the three-phase DC motor with a sine wave after the second step.

[0008] In addition, combinations of the above components arbitrarily, and components and expressions mutually replaced between methods, apparatuses, systems, etc. are also effective as aspects of the present invention or the present disclosure. Furthermore, the description of this item does not explain all the essential features of the present invention, so sub-combinations of these described features can also be the present invention.

Brief Description of the Drawings

[0009] [Figure 1]Figure 1 illustrates the difference in the effect of leakage flux from the coil depending on the positional relationship between the rotor and the Hall element when a three-phase DC motor is locked. [Figure 2] Figure 2 is a circuit diagram of a system equipped with a drive circuit according to an embodiment. [Figure 3] Figure 3 is a waveform diagram illustrating the operation of the drive circuit immediately after the motor starts up. [Figure 4] Figure 4 is a circuit diagram of a bridge circuit used to explain the first to fourth states. [Figure 5] Figure 5 is a waveform diagram illustrating the operation of the motor when a high-impedance section is not provided. [Figure 6] Figure 6 is a waveform diagram illustrating the operation of a motor when a high-impedance section is provided, but no current-decrease or current-increase sections are provided. [Figure 7] Figure 7 is a waveform diagram illustrating the operation of the motor when a high-impedance section, a current-reducing section, and a current-increasing section are provided.

[0010] [Detailed explanation] (Summary of the embodiment) This section outlines some exemplary embodiments of the present disclosure. This outline is intended to provide a basic understanding of the embodiments and to simplify some concepts of one or more embodiments, serving as a prelude to the more detailed descriptions that follow. It is not intended to limit the scope of the invention or disclosure. This outline is not a comprehensive overview of all possible embodiments, nor is it intended to identify essential elements of all embodiments or to delineate the scope of some or all aspects. For convenience, “one embodiment” may be used to refer to one or more embodiments (examples or variations) disclosed herein.

[0011] A drive circuit according to one embodiment is a drive circuit for a three-phase DC motor, and includes a control unit capable of controlling a bridge circuit connected to the three-phase DC motor in a two-phase modulation manner based on a Hall signal indicating the rotor position of the three-phase DC motor. The control unit can switch between a current reduction section in which the duty cycle of the upper arms of the second and third phases is gradually reduced while the upper arm of the first phase and the lower arms of the second and third phases are fixed to the off position and the lower arm of the first phase is fixed to the on position; a high impedance section in which the upper arms and lower arms of all phases are fixed to the off position after the current reduction section; and a current increase section in which the duty cycle of the upper arm of the second phase and the lower arm of the third phase is gradually increased while the upper arms of the first and third phases and the lower arm of the second phase are fixed to the off position and the lower arm of the first phase is fixed to the on position after the high impedance section. The control unit determines that the three-phase DC motor is locked if it does not detect a change in the Hall signal in the high impedance section.

[0012] In this configuration, in the high-impedance section where leakage flux from the coil is virtually zero, the influence of leakage flux from the coil on the Hall signal is almost eliminated. Therefore, by using the Hall signal information in this high-impedance section, the accuracy of determining whether the three-phase DC motor is locked can be improved. Furthermore, in this configuration, since the current is gradually reduced in the current-decrease section before switching to the high-impedance section, sudden fluctuations in the current flowing into the coil (also called coil current) are suppressed, thereby reducing coil vibration and noise. Similarly, since the current is gradually increased when switching from the high-impedance section to the current-increase section, sudden fluctuations in the coil current are suppressed, thereby reducing coil vibration and noise.

[0013] In one embodiment, the control unit may be able to switch to a current consumption section after the current reduction section and before the high impedance section, in which the lower arm of the first phase is fixed to ON and all arms other than the lower arm of the first phase are fixed to OFF. In this case, even if coil current remains after the current reduction section, the noise when switching to the high impedance section can be further reduced by allowing the coil current to be consumed in the current consumption section.

[0014] A drive circuit according to one embodiment may be connected to a single Hall element that generates a Hall signal.

[0015] In one embodiment, the control unit may generate an energizing pattern for fixing the rotor's initial position, and then generate multiple energizing patterns for forced synchronization of the rotor, before switching to a current reduction section. In this case, if the three-phase DC motor is not locked, the rotor will already be in a rotating state, so changes in magnetic flux density due to rotor rotation are more likely to appear as changes in the Hall signal. Therefore, the accuracy of determining the locked state of the three-phase DC motor using Hall signal information can be further improved.

[0016] A motor control method according to one embodiment is a motor control method that controls a three-phase DC motor in a two-phase modulated manner based on a Hall signal indicating the position of the rotor of the three-phase DC motor, and includes a first step of gradually decreasing the current while driving the three-phase DC motor in a sinusoidal wave, a second step of putting the three-phase DC motor into a high-impedance state after the first step, and a third step of gradually increasing the current after the second step to drive the three-phase DC motor in a sinusoidal wave.

[0017] With this configuration, the coil current is gradually reduced before the three-phase DC motor is brought into a high-impedance state. This suppresses sudden fluctuations in the current flowing into the coil, thereby reducing coil vibration and noise. Similarly, by gradually increasing the current from the high-impedance state, sudden fluctuations in the coil current are suppressed, reducing coil vibration and noise. Furthermore, with this configuration, in the high-impedance section where the leakage flux from the coil is virtually zero, the influence of the leakage flux from the coil on the Hall signal is almost eliminated. Therefore, for example, by using the Hall signal information in this high-impedance section, the accuracy of determining the locked state of the three-phase DC motor can be improved.

[0018] In one embodiment, in the first step, the upper arm of the first phase and the lower arms of the second and third phases of the bridge circuit connected to the three-phase DC motor may be fixed to the OFF position, and with the lower arm of the first phase fixed to the ON position, the duty cycle of the upper arms of the second and third phases may be gradually increased. In the second step, the upper and lower arms of all phases of the bridge circuit may be fixed to the OFF position. In the third step, the upper arms of the first and third phases and the lower arm of the second phase may be fixed to the OFF position, and with the lower arm of the first phase fixed to the ON position, the duty cycle of the upper arm of the second phase and the lower arm of the third phase may be gradually increased.

[0019] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Furthermore, the embodiments are illustrative and not limiting to the disclosure and invention, and not all features or combinations thereof described in the embodiments are necessarily essential to the disclosure and invention.

[0020] In this specification, "member A connected to member B" includes cases where member A and member B are physically and directly connected, as well as cases where member A and member B are indirectly connected via other members that do not substantially affect their electrical connection or impair the functions or effects produced by their connection.

[0021] Similarly, "the state in which member C is provided between member A and member B" includes not only cases where member A and member C, or member B and member C, are directly connected, but also cases where they are indirectly connected via other members that do not substantially affect their electrical connection state or impair the functions or effects produced by their combination.

[0022] Furthermore, the vertical and horizontal axes of the waveform diagrams and time charts shown herein have been appropriately enlarged or reduced for ease of understanding, and each waveform shown has also been simplified for ease of understanding.

[0023] First, we will explain the problem in three-phase DC motors where the Hall signal can be affected by leakage flux from the coils.

[0024] Figure 1 illustrates the difference in the effect of leakage flux from the coil 14 depending on the positional relationship between the rotor 12 and the Hall element 20 when the three-phase DC motor 10 is locked. The three-phase DC motor 10 is a three-phase brushless DC motor and is a motor with a single Hall sensor, equipped with one Hall element 20. The three-phase DC motor 10 is an outer rotor type, with the rotor 12 positioned on the outside and the coil 14 positioned on the inside. The Hall element 20 is fixed inside the three-phase DC motor 10 in a position opposite the rotor 12.

[0025] As shown on the left side of Figure 1, when the rotor 12 is locked and stopped at a position where the Hall signal is high, the magnetic flux from the rotor 12 is large, and the leakage flux from the coil 14 is relatively small compared to the magnetic flux from the rotor 12, making it less susceptible to the influence of the leakage flux from the coil 14. Therefore, no change in the Hall signal is detected, and it is easier to correctly determine that the three-phase DC motor 10 is locked. When it is determined that the three-phase DC motor 10 is locked, the lock protection circuit (not shown) stops the power supply to the coil 14. This is also true when the rotor is stopped at a position where the Hall signal is low.

[0026] On the other hand, as shown on the right side of Figure 1, when the rotor 12 is locked and stopped near the phase switch of the Hall signal, the magnetic flux from the rotor 12 becomes smaller than in the state shown on the left side of Figure 1. As a result, the leakage flux from the coil 14 becomes relatively significant compared to the magnetic flux from the rotor 12, making the system more susceptible to the influence of leakage flux from the coil 14. Therefore, when a current is supplied to the coil 14 from the drive circuit (not shown) to drive the three-phase DC motor 10, a change in the Hall signal is detected, and the system is likely to be mistakenly determined not to be in a locked state. The drive circuit then mistakenly detects that the rotor 12 is rotating in response to the change in the Hall signal and continues to supply current to the coil 14 to drive the three-phase DC motor 10.

[0027] Thus, even when the three-phase DC motor 10 is locked, there is a problem in that the Hall signal can be affected by leakage flux from the coil 14 depending on the stopping position of the rotor 12. In Figure 1, an example is shown where the three-phase DC motor 10 is a motor with one Hall sensor, but the same problem can occur even with a motor that has multiple Hall elements 20. Also, in Figure 1, an example is shown where the three-phase DC motor 10 is an outer rotor type, but the same problem can occur even with an inner rotor type where the rotor 12 is located inside and the coil 14 is located outside. Furthermore, if the rotor 12 becomes detached due to damage to the three-phase DC motor 10, no magnetic flux is generated from the rotor 12, making the Hall signal more susceptible to the influence of leakage flux from the coil 14. As a result, the drive circuit cannot detect the abnormality of the three-phase DC motor 10, and mistakenly detects that the rotor 12 is rotating in response to changes in the Hall signal, continuing to supply current to the coil 14 to drive the three-phase DC motor 10.

[0028] The following describes a drive circuit that can improve the accuracy of determining whether a three-phase DC motor is locked.

[0029] Figure 2 is a circuit diagram of a system 100 comprising a drive circuit 200 according to an embodiment. The system 100 comprises a motor 102 and a drive circuit 200. The motor 102 is a three-phase brushless DC motor, and has a U-phase coil L U V-phase coil L V W-phase coil L W This includes the following. Motor 102 is a motor with a single Hall sensor, to which one Hall element 104 is attached. Motor 102 is, for example, a fan motor, and system 100 is, for example, a cooling device. Alternatively, system 100 may be an electronic device comprising a cooling device and a CPU (Central Processing Unit) or the like to be cooled. Motor 102 may be an outer rotor type or an inner rotor type. The drive circuit 200 controls the coil L of motor 102. U ~L W The drive signal V supplied to U ~V WDrive the motor 102 according to the situation.

[0030] The Hall element 104 is supplied with a Hall bias voltage generated by the drive circuit 200. The Hall element 104 outputs a pair of Hall voltages V H+ , V H- indicating the position of the rotor of the motor 102.

[0031] The drive circuit 200 includes a control unit 210, a pre-driver 220, a bridge circuit 230, and a Hall signal generation circuit 240, and is a functional IC integrated on a single semiconductor substrate. The drive circuit 200 has an enable terminal EN, and its operation and stop are switched according to the signal supplied to the enable terminal EN.

[0032] The bridge circuit 230 is a three-phase inverter to be driven, and has a U-phase leg, a V-phase leg, and a W-phase leg. The leg of phase # (# = U, V, W) includes an upper arm Q #-H and a lower arm Q #-L . Each of the upper arm and the lower arm includes a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an IGBT, or a bipolar transistor, and a freewheeling diode (also called a flywheel diode) connected in parallel with the switching element. As shown in FIG. 2, when a MOSFET is used as the switching element, its body diode (not shown) serves as the freewheeling diode.

[0033] The power line 232 of the bridge circuit 230 is connected to a power supply terminal (power pin) VCC, and a power supply voltage is supplied from the outside. Also, the ground line 234 of the bridge circuit 230 is grounded. A power supply voltage V CC may be supplied to the power pin VCC via an anti-reverse diode D1.

[0034] The Hall signal generation circuit 240 supplies a bias signal to the Hall element 104 via an HB pin. The Hall signal generation circuit 240 generates a Hall signal based on the Hall voltages V H+ and VH- The Hall signals S compare and show the relative magnitudes. HALL Generates the Hall signal S. HALL The Hall voltage V H+ , V H- This is a pulse signal that transitions each time the two cross paths.

[0035] The control unit 210 receives the Hall signal S from the Hall signal generation circuit 240. HALL Based on this, the bridge circuit 230 connected to the motor 102 is controlled using a two-phase modulation scheme. Specifically, when the enable signal input to the enable terminal EN indicates the enable state, the control signal Sctrl is generated to rotate the motor 102. The control signal Sctrl is controlled by the upper arm Q U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L It may include six signals indicating on or off. The control unit 210 controls the motor 102 by 180-degree energization control (also called sinusoidal drive). The drive method for the motor 102 is PWM (Pulse Width Modulation) drive method.

[0036] Although not shown in Figure 2, the control unit 210 may change the target rotational speed in response to an external rotational speed control signal or the output signal of the temperature detection element.

[0037] Based on the control signal Sctrl generated by the control unit 210, the pre-driver 220 controls the upper arm Q of the bridge circuit 230. U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L It drives the engine.

[0038] Figure 3 is a waveform diagram illustrating the operation of the drive circuit 200 immediately after the motor 102 starts up.

[0039] First, the control unit 210 generates an energizing pattern for fixing the initial position of the motor 102's rotor during a predetermined initial position fixing section. Specifically, the control unit 210 fixes the outputs OUTU, OUTV, and OUTW of each phase of the bridge circuit 230 to a predetermined state. The predetermined state is not limited, but in one example, OUTU=L, OUTV=L, and OUTW=H. The initial position fixing section is a section for fixing the position of the rotor, whose position is not yet determined, to a predetermined position (referred to as the initial position). During the initial position fixing section, the combination of outputs OUTU to OUTW applied to the motor 102 is fixed. In this state, the position of the motor 102's rotor is fixed at the target initial position corresponding to the combination of outputs, and at this time, the Hall signal S HALL It should take the appropriate level according to the initial target position.

[0040] The control unit 210 generates an energizing pattern for forced synchronization of the motor 102's rotor during a predetermined forced synchronization start-up period, after the initial position fixing period. Specifically, the control unit 210 checks the state of each phase output OUTU, OUTV, and OUTW of the bridge circuit 230 at predetermined intervals, i.e., the Hall signal S HALL Regardless of the changes, the states are switched in a predetermined order. The control unit 210 generates multiple energization patterns for forced synchronization of the motor 102's rotor, and then sequentially takes the first state φ1 to the fourth state φ4 at timings included in the forced synchronization start section.

[0041] Here, we will explain the overview of the first state φ1 to the fourth state φ4. As explained using Figure 1, even when the motor 102 is locked, the Hall signal S may be affected depending on the rotor's stopping position. HALL However, this can be affected by leakage flux from the coil. Therefore, the control unit 210 takes a third state φ3 in which the outputs OUTU, OUTV, and OUTW of the bridge circuit 230 are in a high impedance state (Hi-Z). While the control unit 210 is in the third state φ3, the Hall signal S HALL If no change is detected in the Hall signal S, it is determined that the motor 102 is locked. HALL This eliminates the influence of leakage magnetic flux from the coil.

[0042] If the control unit 210 switches to the third state φ3 during the forced synchronous startup section, noise generation may become a problem. The inventors have found that this noise is caused by vibration of the coil due to rapid fluctuations in the coil current. Therefore, the control unit 210 can reduce noise by entering a first state φ1 that gradually decreases the coil current immediately before entering the third state φ3, and a fourth state φ4 that gradually increases the coil current immediately after entering the third state φ3. Furthermore, the control unit 210 can further reduce noise when switching to the third state φ3 by entering a second state φ2 that consumes the coil current after the first state φ1 and before entering the third state φ3. Details of the first state φ1 to the fourth state φ4 will be described later.

[0043] The control unit 210 generates an energizing pattern to stably rotate the rotor of the motor 102 during the Hall drive section, following the forced synchronous startup section. Specifically, the control unit 210 uses the state of the outputs OUTU, OUTV, and OUTW of each phase of the bridge circuit 230 to generate the Hall signal S HALL It switches in a predetermined order, synchronized with the rotation of the rotor, that is, usually in sync with the rotation of the rotor.

[0044] Figure 4 is a circuit diagram of the bridge circuit 230 used to explain the first state φ1 to the fourth state φ4. The control unit 210 can sequentially switch between the sections in the first state φ1, the second state φ2, the third state φ3, and the fourth state φ4.

[0045] In the first state φ1, the control unit 210 controls the upper arm Q of the V phase. V-H And the lower arm Q of the U and W phases U-L ,Q W-L And are fixed to OFF, V-phase lower arm Q V-L With the ON position fixed, the upper arm Q of the U-phase and W-phase U-H ,Q W-HThe duty cycle is gradually reduced. This causes the coil current to gradually decrease. The period in which the control unit 210 takes the first state φ1 is also called the current reduction period. The longer the current reduction period, the more effective it is in reducing noise, but in one example, the current reduction period has an electrical angle of 30°. The current reduction period is the first step in a motor control method that controls the motor 102 in a two-phase modulation scheme, in which the current is gradually reduced while the motor 102 is driven sinusoidally.

[0046] In the second state φ2, the control unit 210 controls the lower arm Q of the V phase. V-L Fix it to ON, V-phase lower arm Q V-L All arms except the one specified are locked in the off position. This consumes any remaining coil current in the bridge circuit 230. The period in which the control unit 210 takes the second state φ2 is also called the current consumption period. The current consumption period should preferably have enough time to consume the coil current, but it is undesirable if it is too long as it may switch to the power generation state. In one example, the current consumption period has an electrical angle of 15°.

[0047] In the third state φ3, the control unit 210 fixes the upper and lower arms of all phases to the OFF state. As a result, the outputs OUTU, OUTV, and OUTW of the bridge circuit 230 enter a high-impedance state. The section in which the control unit 210 enters the third state φ3 is also called the high-impedance section. In a motor control method that controls the motor 102 using a two-phase modulation scheme, the high-impedance section is the second step after the first step, in which the motor 102 is brought into a high-impedance state.

[0048] In the fourth state φ4, the control unit 210 controls the upper arm Q of the V phase and W. V-H ,Q W-H And the lower arm Q of the U phase U-L And are fixed to OFF, V-phase lower arm Q V-L With the ON position fixed, the upper arm Q of the U phase U-H and the lower arm Q of the W phase W-LIt may include six signals indicating on and off. The control unit 210 gradually increases the duty cycle of 180. This causes the coil current to gradually increase. The section in which the control unit 210 takes the fourth state φ4 is also called the current increase section. In a motor control method that controls the motor 102 under a two-phase modulation scheme, the current increase section is the third step after the second step in which the current is gradually increased to drive the motor 102 in a sinusoidal wave.

[0049] Note that the states of the U, V, and W phases shown in Figure 4 are examples, and any two phases may be swapped with each other. That is, among the first to third phases that can be arbitrarily selected from the U, V, and W phases, the V phase is an example of the first phase, the U phase is an example of the second phase, and the W phase is an example of the third phase.

[0050] The noise reduction effect of this embodiment will be explained with reference to Figures 5 to 7. In Figures 5 to 7, I U The U-phase coil L U This shows the coil current to the device.

[0051] Figure 5 is a waveform diagram illustrating the operation of the motor when a high-impedance section is not provided. As shown in Figure 5, when a high-impedance section is not provided, the problem of noise generation does not occur, but the Hall signal S HALL There is noise present. This noise is thought to be due to leakage magnetic flux from the coil.

[0052] Figure 6 is a waveform diagram illustrating the operation of a motor when a high-impedance section is provided, and no current-decrease or current-increase sections are provided. As shown in Figure 6, when a high-impedance section is provided, the Hall signal S is present in the high-impedance section. HALL The noise has been reduced. However, the noise is louder at the timing before and after the high-impedance section.

[0053] Figure 7 is a waveform diagram illustrating the operation of the motor when a high-impedance section, a current-reducing section, and a current-increasing section are provided. As shown in Figure 7, when a high-impedance section is provided, the Hall signal S is present in the high-impedance section. HALL The noise is reduced. Furthermore, by providing a current reduction section immediately before the high-impedance section and a current increase section immediately after the high-impedance section, the generation of noise is also suppressed.

[0054] The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing steps, and that such modifications also fall within the scope of this disclosure or the present invention. Such modifications will be described below.

[0055] (Variation 1) The number of Hall elements 104 attached to the motor 102 is not limited to one, but may be multiple. For example, the motor 102 may be a motor with three Hall elements 104 attached, equipped with a 3-Hall sensor.

[0056] (Modification 2) The control unit 210 may be composed of logic circuits, or it may be implemented as a combination of a processor and a software program.

[0057] (Note) This specification discloses the following technologies:

[0058] (Item 1) A drive circuit for a three-phase DC motor, The control unit is equipped with a control unit capable of controlling a bridge circuit connected to the three-phase DC motor in a two-phase modulation manner based on a Hall signal indicating the position of the rotor of the three-phase DC motor. The control unit, With the upper arm of the first phase and the lower arms of the second and third phases fixed in the OFF position, and the lower arm of the first phase fixed in the ON position, a current reduction section is provided in which the duty cycle of the upper arms of the second and third phases is gradually reduced. After the current reduction section, there is a high-impedance section in which the upper and lower arms of all phases are fixed to the OFF position, After the high-impedance section, the upper arms of the first and third phases and the lower arm of the second phase are fixed in the off position, and the lower arm of the first phase is fixed in the on position. In this current-increasing section, the duty cycle of the upper arm of the second phase and the lower arm of the third phase are gradually increased. It is possible to switch between these two modes. The control unit determines that the three-phase DC motor is locked if it does not detect a change in the Hall signal in the high-impedance section. Drive circuit.

[0059] (Item 2) The control unit, After the current reduction section and before the high impedance section, it is possible to switch to a current consumption section in which the lower arm of the first phase is fixed to ON and all arms other than the lower arm of the first phase are fixed to OFF. The drive circuit described in item 1.

[0060] (Item 3) A drive circuit according to item 1 or 2, to which one Hall element that generates the Hall signal is connected.

[0061] (Item 4) The control unit generates an energizing pattern for fixing the initial position of the rotor, and then generates multiple energizing patterns for forcibly synchronizing the rotor, after which it can switch to the current reduction section. A drive circuit as described in any of items 1 through 3.

[0062] (Item 5) A motor control method for controlling a three-phase DC motor in a two-phase modulated manner based on a Hall signal indicating the position of the rotor of the three-phase DC motor, The first step involves gradually reducing the current while driving the three-phase DC motor with a sinusoidal wave, After the first step, a second step is to put the three-phase DC motor into a high-impedance state, Following the second step, a third step is to gradually increase the current to drive the three-phase DC motor in a sinusoidal manner, A motor control method including the following.

[0063] (Item 6) In the first step, the upper arm of the first phase and the lower arms of the second and third phases of the bridge circuit connected to the three-phase DC motor are fixed in the OFF position, and with the lower arm of the first phase fixed in the ON position, the duty cycle of the upper arms of the second and third phases is gradually increased. In the second step, the upper and lower arms of all phases of the bridge circuit are fixed to the OFF position. In the third step, with the upper arms of the first and third phases and the lower arm of the second phase fixed in the off position, and the lower arm of the first phase fixed in the on position, the duty cycle of the upper arm of the second phase and the lower arm of the third phase are gradually increased. The motor control method described in item 5. [Explanation of Symbols]

[0064] 10 Three-phase DC motor 12 rotors 14 coils 20 Hole elements 100 Systems 102 Motor 104 Hall element 200 drive circuit 210 Control Unit 220 Pre-driver 230 Bridge Circuit 232 Power Line 234 Grounding line 240 Hall signal generation circuit D1 diode EN Enable terminal L U U-phase coil L V V-phase coil LW W-phase coil S HALL Hall signal Sctrl control signal VCC power supply pin V CC Power supply voltage V U drive signal V V drive signal V W drive signal V H+ Hall voltage V H- Hall voltage

Claims

1. A drive circuit for a three-phase DC motor, The control unit is equipped with a Hall signal indicating the rotor position of the three-phase DC motor, and is capable of controlling the bridge circuit connected to the three-phase DC motor in a two-phase modulation manner. The control unit, With the upper arm of the first phase and the lower arms of the second and third phases fixed in the OFF position, and the lower arm of the first phase fixed in the ON position, a current reduction section is provided in which the duty cycle of the upper arms of the second and third phases is gradually reduced. After the current reduction section, there is a high-impedance section in which the upper and lower arms of all phases are fixed to the OFF position, After the high-impedance section, the upper arms of the first and third phases and the lower arm of the second phase are fixed in the OFF position, and the lower arm of the first phase is fixed in the ON position. In this current-increasing section, the duty cycles of the upper arm of the second phase and the lower arm of the third phase are gradually increased. It is possible to switch between these two modes. The control unit determines that the three-phase DC motor is locked if it does not detect a change in the Hall signal in the high-impedance section. Drive circuit.

2. The control unit, After the current reduction section and before the high impedance section, it is possible to switch to a current consumption section in which the lower arm of the first phase is fixed to ON and all arms other than the lower arm of the first phase are fixed to OFF. The drive circuit according to claim 1.

3. The drive circuit according to claim 1, wherein one Hall element that generates the Hall signal is connected.

4. The control unit generates an energizing pattern for fixing the initial position of the rotor, and then generates multiple energizing patterns for forcibly synchronizing the rotor, after which it can switch to the current reduction section. The drive circuit according to claim 1.

5. A motor control method for controlling a three-phase DC motor in a two-phase modulation scheme based on a Hall signal indicating the position of the rotor of the three-phase DC motor, The first step involves gradually reducing the current while driving the three-phase DC motor with a sinusoidal wave, After the first step, a second step is to put the three-phase DC motor into a high-impedance state, After the second step, the third step is to gradually increase the current to drive the three-phase DC motor in a sinusoidal manner, A motor control method including the following.

6. In the first step, the upper arm of the first phase and the lower arms of the second and third phases of the bridge circuit connected to the three-phase DC motor are fixed in the OFF position, and with the lower arm of the first phase fixed in the ON position, the duty cycle of the upper arms of the second and third phases is gradually increased. In the second step, the upper and lower arms of all phases of the bridge circuit are fixed to the OFF position. In the third step, with the upper arms of the first and third phases and the lower arm of the second phase fixed in the OFF position, and the lower arm of the first phase fixed in the ON position, the duty cycle of the upper arm of the second phase and the lower arm of the third phase are gradually increased. The motor control method according to claim 5.

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