JP6303129B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor drive device by inverter control.

Conventionally, this type of motor drive device uses a bootstrap power supply composed of a diode, a resistor, and a capacitor for the high voltage side switching element drive part of the inverter circuit, and when the motor is started, the low voltage side switching element of the inverter circuit is turned on / off. The capacitor of the bootstrap power supply is charged to a stable potential. (For example, see Patent Document 1)
FIG. 5 shows a conventional motor driving device described in Patent Document 1, and includes a one-phase (U-phase) inverter, a driving circuit, and a bootstrap circuit of a motor driving device that drives a three-phase motor. The connection relationship is shown.

  In FIG. 5, an inverter 102 that drives a three-phase motor has a three-phase full bridge configuration using six circuits in which switching elements and diodes are connected in antiparallel.

  The drive circuits 104 and 105 respectively perform on / off control of the high-voltage side switching element 102a and the low-voltage side switching element 102b according to the states of the input signals Up and Un.

  The U-phase bootstrap circuit 106 is constituted by a series connection of a DC power supply 106a of about 15 V, a diode 106b, a resistor 106c, and a capacitor 106d. The negative potential side of the capacitor 106d is connected to the negative potential side of the drive circuit 104, and the switching element Commonly connected to the emitter terminal 102a. The positive terminal of the capacitor 106 d is connected to the power supply terminal of the drive circuit 104.

  Immediately before starting the motor, the switching element 102b is intermittently energized with an on / off duty of 50%, whereby the capacitor 106d is initially charged from the DC power source 106a via the diode 106b and the resistor 106c during the ON period of the switching element 102b. As a result, the power supply of the high-voltage side drive circuit 104 is secured, and the high-voltage side switching element is in a drivable state.

  Next, PWM control is performed on the high-voltage side switching element 102a when the motor starts rotating. In the charging operation of the bootstrap circuit 106, when the high-voltage side switching element 102a is turned off, the stored energy of the motor inductance flows as a regenerative current through the low-voltage side diode 102h. At that time, the negative side terminal of the bootstrap capacitor is It becomes close to the GND level of the inverter circuit 102 and is charged.

  Therefore, since the battery is charged when the low voltage side switching element 102b is turned on and when the high voltage side switching element 102a is turned on / off, the bootstrap potential is kept stable.

JP 2000-23484 A

  However, in the above-described conventional configuration, the diode of the bootstrap circuit can be turned on / off at high speed, and a high-speed diode having a relatively large current rating that can inject charging charge into the capacitor in a short time, and the charging current of the capacitor are A current limiting resistor is required to keep it below the rated value. Further, the bootstrap circuit is required for three phases, and each circuit has a high potential difference. Therefore, it is necessary to maintain an insulation distance according to safety regulations, resulting in an increase in circuit area. Therefore, in recent years, the bootstrap circuit diode is replaced with a MOSFET capable of high-speed switching, and the gate drive of the MOSFET is performed by charging the charge pump power supply synchronized with the low-voltage side switching element drive signal. A reduction in the number of circuit components and a reduction in size have been proposed by using a semiconductor element in which a part is integrated into a single chip. However, in the conventional configuration, in the low-speed drive region immediately after startup, the low-voltage side switching element is continuously energized, and the potential of the MOSFET gate drive charge pump power supply is lowered, thereby turning off the switch part of the bootstrap power supply. There was a problem that a motor start-up failure would occur.

In order to solve the above-described conventional problems, a motor driving device according to the present invention includes a brushless DC motor including a stator and a rotor having a permanent magnet, and two switching elements connected in series. an inverter for outputting an AC voltage to input the pair of DC voltage across the connected switching element 3 pairs in parallel, a capacitor for driving the high voltage side switching element connected to the high voltage side of the inverter a bootstrap power supply and a switch unit, wherein the charge-pump power supply that drives the switch unit bootstrap supply, has an on-time correction unit for correcting the on-time of the high pressure side switching elements, a capacitor of the charge pump power supply It is charged during off of the low-pressure switching element connected to the low pressure side of the inverter, the brushless D By energizing any stator windings of the motor when starting, when fixing the rotor magnetic pole position to a predetermined position, and turns off the low-pressure Gawasu switching elements are on the inverter at an arbitrary frequency, on the low-pressure Gawasu oN time of the switching elements in the odd such become longer than a predetermined time while charging the capacitor of the charge pump power, Ri by said on-time correction section the high pressure side switching element The time is corrected.

Accordingly and during positioning of the motor stator, for a charge pump power during low-speed driving, such as immediately after the motor start also drives the switch portion of the bootstrap power supply can be ensured stably fixed potential greater than the bootstrap power switch It is possible to reliably and stably turn on the hose portion . Further, a decrease in current in the positioning control accompanying the turning off of the low voltage side switching element can be suppressed by correcting the on time of the high voltage side switching element. Therefore, since the decrease in current and starting torque at the time of positioning can be suppressed, it can be ensured reliably start of the brushless DC motor.

  The motor drive device of the present invention can realize a reliable and stable motor start-up, reduce the circuit size and cost, and reduce the number of components.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Timing chart at motor start-up in Embodiment 1 of the present invention The block diagram which shows the drive signal generation part in Embodiment 1 of this invention. Timing chart at the time of positioning in the first embodiment of the present invention Circuit diagram for one phase of a conventional motor drive device

1st invention connects the brushless DC motor which consists of a stator and the rotor which has a permanent magnet, two switching elements in series, and connects this pair of switching elements connected in three pairs in parallel. an inverter which inputs a DC voltage and outputs the AC voltage across that, the bootstrap power supply and a capacitor and a switch portion for driving the high voltage side switching element connected to the high voltage side of the inverter, the boot includes a charge-pump power supply that drives the switch section of the strap supply, the on-time correction unit for correcting the on-time of the high pressure side switching elements, a capacitor of the charge pump power supply, the low pressure side connected to the low pressure side of the inverter It is charged during off switching element, by energizing any stator winding at the start of the brushless DC motor When fixing the rotor magnetic pole position to a predetermined position, a low pressure Gawasu switching elements are on the inverter is turned off at an arbitrary frequency, the on time of the low pressure Gawasu switching element is longer than a predetermined time with the not such odd to charge the capacitor of the charge pump power supply, a motor driving device for correcting the on-time of the on-time correction Ri by the unit the high pressure side switching element. Thus in a certain period energizing a predetermined winding, even during positioning control for fixing the magnetic pole position of the motor, with always maintain a predetermined voltage is charged charges the capacitor of the charge pump power, the low-pressure side Since the decrease in the positioning current due to the switching element being turned off can be suppressed by correcting the ON time of the high-voltage side switching element, the stator of the brushless DC motor can be reliably fixed at a predetermined position, so that the brushless DC motor can be reliably started. realizable.

  Furthermore, a MOSFET capable of high-speed switching is used as the diode of the bootstrap circuit, and the gate drive of the MOSFET is performed by charging the charge pump power supply synchronized with the low-voltage side switching element drive signal. It is possible to use a semiconductor element in which the circuit part is integrated into a single chip, and the number of circuit components can be reduced, the size can be reduced, and the cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 is a block diagram of a motor driving apparatus according to an embodiment of the present invention.
In FIG. 1, a brushless DC motor 1 includes a stator having a three-phase winding and a rotor having a permanent magnet.

  The inverter 2 is configured in a three-phase full bridge by connecting three circuits connected in series in parallel in three circuits. Each switching element is connected to a diode (2g to 2l) in antiparallel.

  The brushless DC motor 1 includes a rotor 1a having a permanent magnet and a stator 1b having a three-phase winding. Each end of the three-phase winding is connected to a connection point of series connection of switching elements of the inverter 2. Yes.

The drive circuit 3 is a drive circuit for the switching element of the inverter 2, and receives the drive signal Hin of the high voltage side switching element and the low voltage side switching element Lin signal from the drive signal generation unit 10, and connects the high voltage side switching connected to the high voltage side. The element 2a is driven by the high-voltage side element driving unit 4 according to the Hin signal, and the low-voltage side switching element 2b connected to the ground side is driven by the low-voltage side element driving unit 5 according to the Lin signal.

The bootstrap power supply 6 is a power supply for the high-voltage side element driving unit 4 constituted by a diode 6a, a switch unit 6b, and a capacitor 6c, and serves as a gate drive voltage for the low-voltage side switching element 2b. Note that the switch unit 6b is a semiconductor element switch and uses a MOSFET.

  The switch drive unit is configured as a charge pump power supply 7 by the diode 7a, the capacitor 7b, and the drive unit 7c, and the switch unit 6b can be turned on by supplying a voltage to the switch unit 6b. Since the drive unit 7c receives the drive signal Lin for the low-voltage side switching element 2b, the drive unit 7c is driven in synchronization with the low-voltage side switching element.

  In the bootstrap circuit, a high-speed diode is generally used for the series circuit portion of the diode 6a and the switch portion 6b. However, in the present invention, a MOSFET capable of high-speed switching is used, and the charge charge VCC of the capacitor is obtained. A diode 6b is inserted in series so as to prevent backflow to the side.

  In addition, by using the switch unit 6b as a MOSFET, commercially available semiconductor components in which the high-voltage side drive unit 4, the low-voltage side drive unit 5, the diode 6a, the MOSFET 6b, and the charge pump power supply 7 are configured as a one-chip integrated circuit are used. The number of parts of the drive circuit 3 can be reduced, and the size and cost can be reduced.

  For simplicity, the drive circuit 3 shows only one phase for the switching elements 2a and 2b, but has the same circuit for the other two phases (switching elements 2c and 2d and 2e and 2f). .

  Here, the operation of the bootstrap power supply 6 will be described.

  In FIG. 1, the capacitor 6c of the bootstrap power supply is connected to VCC when the switch unit 6b is turned on, and is charged when the potential difference between the VCC potential and the capacitor 6c potential is larger than the forward voltage of the diode 6a.

  There are two paths for charging the capacitor 6c. The low voltage when the low voltage side switching element 2b is turned on (first charging mode) and immediately after the high voltage side switching element 2a is energized (shift from on to off). This is when the side diode 2h is turned on (second charging mode).

  First, in the first charging mode, when the switching element 2b is turned on, the potential at the connection point A (shown in FIG. 1) drops to near GND, and the capacitor from the power supply VCC through the diode 6a and the switch unit 6b. 6c is charged.

  Next, in the second charging mode, when the high-voltage side switching element 2a is switched from the energized state to the off state, the energy stored in the motor winding 1b is released in the reflux mode via the diode 2h. Accordingly, the potential at the connection point A drops below the GND level, and the capacitor 6c is charged from the power supply VCC.

The operation of the charge pump power supply 7 will be described. When Lin is a low signal, the low-voltage side element drive unit 5 outputs a low signal, and the low-voltage side switching element 2b is in an off state. At the same time, a low signal is input to the drive element 7c of the charge pump power supply 7 and a low signal is output. As a result, the driving element 7c connection side terminal of the capacitor 7b becomes a potential near GND, and is charged from VCC via the diode 7a. As a result, the drive voltage of the switch unit 6b is a voltage obtained by subtracting the ON voltage of the diode 7a from VCC. When the potential difference between this voltage and the capacitor 6c of the bootstrap power supply 6 is equal to or greater than a predetermined potential difference, the switch unit 6b is turned on. That is, when the voltage of the capacitor 6c is lower than a certain level, the switch unit 6b is turned on.

Next, when Lin changes from a low signal to a high signal, the output of the driving element 7c becomes VCC, and the potential of the capacitor 7b rises to a potential obtained by subtracting the forward voltage of the diode 7a from twice the VCC voltage. At this time, when the potential of the capacitor 6c of the bootstrap power supply 6 is near VCC, the switch unit 6b is turned on.

  FIG. 2 shows driving signals of the switching elements when the brushless DC motor 1 is started. In FIG. 2, the shaded area indicates a section in which the phase switching element that energizes the motor winding is turned on.

  Control at startup will be described with reference to FIG. When the brushless DC motor 1 is in a stopped state, Lin (Un, Vn, Wn in FIG. 2) outputs a low signal (section A), and the drive element 7c is in an output state close to the GND level. Therefore, the capacitor 7b is charged near the VCC voltage.

  A section B is an initial charging section of the capacitor 6c of the bootstrap circuit, and when a driving command for the brushless DC motor 1 is generated, the driving signals Lin (Un, Vn, Wn) of all the three-phase low-voltage side switching elements are in a high state. It becomes. Thereby, the low voltage side switching elements 2b, 2d, and 2f are turned on. At this time, a high signal is output from the drive element 7c of the charge pump power supply 7, and the capacitor potential becomes a potential reduced by a voltage drop of the diode 7a from twice Vcc, and the switch element 6b of the bootstrap power supply 6 is turned on. At this time, since the low-voltage side switching element is in the ON state, the connection-side terminal with the switching element of the capacitor 6c of the bootstrap circuit is at a potential close to the GND level. Therefore, the capacitor of the bootstrap circuit is charged with the charge from VCC, and the power supply voltage of the high-voltage side element driving unit 4 is secured, so that the high-voltage side switching element can be driven.

  In section C, when the high-voltage side switching element is energized in section D, the upper and lower switching elements in the same phase (W-phase high-pressure side element 2e and W-phase low-pressure side element 2f in FIG. 2) are provided so as not to be energized simultaneously. However, this is not necessary when using elements that logically prohibit simultaneous energization of the upper and lower sides by a half-bridge gate driver or the like.

  Section D is a "positioning control" section in which the rotor rotating position is fixed at a predetermined position by energizing an arbitrary phase of the stator winding of the brushless DC motor 1, and the high voltage side switching element 2e and the low voltage side The switching element 2b is in an on state.

  By determining the magnetic pole position of the rotor to a predetermined position in this way, the motor is stably started by switching the driving pattern of the switching element (that is, the winding for starting energization) determined in advance in section E. Can drive.

  When the energization of the winding of the brushless DC motor 1 is a rectangular wave drive with an electrical angle of 150 degrees or less, the brushless DC motor is switched by switching either the upper or lower switching element at an arbitrary frequency at an arbitrary on / off ratio. The voltage applied to 1 is adjusted (PWM control).

  While the high-voltage side switching element is on, the voltage at both ends of the capacitor 6c is lowered due to the consumption and discharge of the charge of the capacitor 6c of the bootstrap power supply 6. Accordingly, when the continuous energization time of the high-voltage side switching element is long, a large-capacitance capacitor is necessary (upsizing of parts and cost increase). Therefore, in the embodiment of the present invention, the high-voltage side switching elements (2a, 2c, 2e) Is turned on / off by PWM control to provide a bootstrap capacitor charging path.

  However, if the ON time of the low-voltage side switching element becomes longer, the non-charging period of the capacitor of the charge pump power supply 7 becomes longer, and the voltage decreases due to the influence of internal leakage current or the like.

Therefore, in the present embodiment, the “on-time control period of the stator” and the “low-speed driving period after startup” in which the on-time of the low-voltage side switching element (that is, the non-charging period of the capacitor 7b of the charge pump power supply 7) is particularly long. so the switching element of the high-pressure side conducting phase, also the switching element of the low-pressure side conduction phase so as to be turned on / off at predetermined intervals, are provided charging period of capacitor 7b of the charge pump power.

  On the other hand, providing an OFF period for the switching element of the low-voltage energized phase is accompanied by a decrease in motor winding current during positioning control during startup and low-speed driving. Therefore, in the present embodiment, the on-time of the high-voltage side switching element is corrected according to the off-time of the low-voltage side switching element, and the energization time is increased to suppress a decrease in current at startup and at low speed. Yes.

  FIG. 3 is a block diagram of the drive signal generation unit 10 for the switching element in the first embodiment, and shows a method for generating an on / off signal for each switching element, including correction of the on-time of the high-voltage side switching element.

  In FIG. 3, the output of the drive signal generation unit 10 is each phase of the inverter 2, the high-voltage side switching element drive signal Hin, and the low-voltage side switching element drive signal Lin, and turns on or off the switching element.

  In FIG. 3, the low-voltage side drive waveform generation unit 11 inputs a commutation cycle based on the off time by the lower element off time setting unit 12 and the motor drive speed by the second PWM timer 13 and the commutation cycle command unit 14. A drive signal for the low voltage side switching element is generated.

  The voltage command unit 15 instructs a voltage to be applied to the motor based on a preset positioning current value, a starting torque at the time of starting, and speed feedback control when the motor is driven. The on-time correction unit 16 adds a correction value that is set by the lower element off-time setting unit 12 to the voltage to be applied to the motor by the voltage command unit 15 and takes the off-time of the lower element into consideration, thereby Input to the drive waveform generator 18. The high voltage side waveform generator 18 receives the first PWM timer 17 and the commutation cycle based on the motor drive speed by the commutation cycle command unit 14 and generates a drive signal for the high voltage side switching element.

  The output phase selection unit 19 inputs the signals of the low-voltage side drive waveform generation unit 11 and the high-voltage side drive waveform generation unit 18 and outputs an on / off signal of each switching element in an output pattern for generating a three-phase AC voltage. To do.

  In FIG. 3, the first PWM timer and the second PWM timer are assumed to use different timers. However, both timers may use a common PWM timer.

  FIG. 4 is a timing chart of the switching element in the energized phase (current flows from the W-phase winding to the U-phase winding) during positioning in the first embodiment, where Wp is the W-phase high-voltage side switching element, and Un is The drive signal of a U-phase low voltage | pressure side switching element is shown.

In FIG. 4, the first PWM timer 17 and the second PWM timer 13 are timers having the same frequency, but may be different frequencies. Time T is a PWM cycle, which is the cycle of the first PWM timer 17 and the second PWM timer 13 .

A section D1 is an OFF section of the U-phase low-pressure side switching element during positioning control and motor startup. This period is set by the lower element off time setting unit 12 as a charging period of the capacitor 7b of the charge pump power supply. In this section, since the Lin signal in FIG. 1 is L, the L signal is output from the drive element 7c of the charge pump power supply, and the capacitor 7b is charged every VCC period from VCC, so that a stable potential can always be secured. In other words, even when a specific winding is energized for a long period of time, such as during motor positioning control or during low-speed driving immediately after startup, the charge pump power supply is always provided by providing a periodic off interval for the lower switching element. A predetermined potential is secured, and the switch unit 6b of the bootstrap power supply can be driven reliably.

  A section D <b> 2 is an ON section of the high-voltage side switching element set by the voltage command unit 15. This section is based on a voltage (based on a starting torque (that is, a starting current) applied in positioning control based on a current necessary for securely fixing the rotor position of the motor to a predetermined position, and in starting after positioning ( That is, the PWM on-duty) is set in advance. Further, in the section D2, the input voltage of the inverter 2 (VDC in FIG. 1), or when the AC power supply is rectified and smoothed to generate VDC, the input voltage of the inverter 2 is adjusted by the AC power supply voltage. A more reliable startability of the motor can be secured without affecting the fluctuation.

  A section D3 is a correction section for the on-time of the high-voltage side switching element. This section is set by the on-time correction unit 16 based on the time set by the lower element off-time setting unit 12. Specifically, for example, when the off-duty of the lower element is 1%, the on-time correcting unit sets the correction amount so as to add 1% of the on-duty correction amount of the upper element. Thus, by adding a correction amount to the ON time of the upper switching element according to the OFF period of the lower switching element, the current flowing through the motor winding can be reduced by providing the OFF period of the lower switching element. Suppress.

  Therefore, the sum of the section D2 and the section D3 becomes the ON section of the upper switching element, and the difference between the ON section of the upper element and the OFF section of the lower element is increased by a predetermined time, Torque at start-up is ensured and motor start-up is maintained. Sections D2 and D3 are sections in which the lower switching element is also turned on. In the sections D2 and D3, the capacitor of the charge pump power supply is sufficiently charged by the section D1, so that the switch portion of the bootstrap power supply can be driven. Therefore, in this section, the lower switching element is turned on and the capacitor of the bootstrap power supply is charged in the first charging mode.

  A section D4 is a section in which the upper switching element is off and the lower switching element is on. This section is a section in which the energy stored in the motor winding by the turn-off of the upper switching element is discharged through a diode connected in reverse parallel to the W-phase lower switching element, and the capacitor 6c of the bootstrap power supply is the second one. It is charged in the charge mode. In this period, the drive signal Lin of the lower switching element is high, and the capacitor 7b of the charge pump power supply cannot be charged, while the potential drops due to charge discharge due to internal leakage current or the like. However, the charge pump power supply is made shorter by setting the off period (section T in FIG. 4) of the lower switching element to be shorter than the time required for the capacitor of the charge pump power supply to discharge below the potential required for driving the switch section of the bootstrap power supply. As a result, the capacitor potential can stably secure a predetermined potential or more, and as a result, the bootstrap power supply can be operated reliably and the drive voltage of the upper switching element can be stably secured. As a result, the motor can be reliably and stably started by realizing reliable positioning of the motor stator and ensuring appropriate starting torque.

  In FIG. 3, the ON / OFF cycle of the U-phase low-voltage side switching element is made to coincide with the PWM cycle of the W-phase high-voltage side, but it can be arbitrarily set as the time when the charge of the capacitor 7b of the charge pump power supply is discharged. I do not care.

As described above, in the embodiment of the present invention, a brushless DC motor composed of a stator and a rotor having a permanent magnet, and two switching elements are connected in series, and a pair of switching units connected in series. an inverter for outputting an AC voltage to input DC voltage across the connected elements 3 pairs in parallel, and a capacitor and a switch portion for driving the high voltage side switching element connected to the high voltage side of the inverter a bootstrap power supply, a charge-pump power supply that drives the switch unit of the bootstrap power supply, having the high pressure side on-time correcting unit for correcting the on-time of the switching element, the capacitor of the charge pump power supply, the inverter It is charged during off of the low-pressure switching element connected to the low pressure side, at the start of the brushless DC motor By energizing the meaning of the stator winding, when fixing the rotor magnetic pole position to a predetermined position, and turns off the low-pressure Gawasu switching elements are on the inverter at an arbitrary frequency, the low-pressure Gawasu thereby charging the capacitor of the charge pump power-on time of the switching element is in the longer become such odd predetermined time, correcting the on-time of Ri by said on-time correction section the high pressure side switching element It is a motor drive device. Thus in a certain period energizing a predetermined winding, when positioning control for fixing the magnetic pole position of the motor and, starting even during operation immediately, always charge accumulates in the capacitor of the charge pump supply a predetermined voltage In addition, the decrease in the motor current caused by the low-voltage side switching element being turned off can be suppressed by correcting the on-time of the high-voltage side switching element, so that the positioning of the stator of the brushless DC motor can be reliably performed by securing a predetermined positioning current. Thus, it is possible to reliably start the brushless DC motor by securing a predetermined starting torque.

  Furthermore, a MOSFET capable of high-speed switching is used as the diode of the bootstrap circuit, and the gate drive of the MOSFET is performed by charging the charge pump power supply synchronized with the low-voltage side switching element drive signal. Therefore, it is possible to use an element in which a single-chip integrated circuit is used, and to reduce the number of circuit components, reduce the size, and reduce the cost.

  As described above, the motor driving device according to the present invention can stably start the motor while reducing the number of circuit components, reducing the size and cost, and is therefore a device for driving a three-phase brushless DC motor by inverter control. Applicable to all uses.

1 Brushless DC motor 2 Inverter 6 Bootstrap power supply 7 Charge pump power supply 16 On-time correction unit

Claims (1)

A brushless DC motor composed of a stator and a rotor having a permanent magnet, and two switching elements are connected in series, and a DC voltage is applied to both ends of the three pairs of switching elements connected in parallel. an inverter for outputting an AC voltage to input, and the bootstrap power source is constituted by a capacitor and a switch portion for driving the high voltage side switching element connected to the high voltage side of the inverter, the switch portion of the bootstrap power supply a charge pump power supply for driving, have the high pressure side on-time correcting unit for correcting the on-time of the switching element, the capacitor of the charge pump power supply, the time off in the low-pressure switching element connected to the low pressure side of the inverter When the brushless DC motor is charged, an arbitrary stator winding is energized, and the rotor magnetic pole position When fixing to a predetermined position, a low pressure Gawasu switching elements are on the inverter off at any frequency, no matter on-time of the low pressure Gawasu switching element such become longer than the predetermined time to together to charge capacitor of the charge pump power, the motor driving device for correcting the on-time of the on-time correction Ri by the unit the high pressure side switching element.

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