JP5307997B2 - Brushless DC motor drive device - Google Patents

Description

  The present invention relates to a brushless DC motor (hereinafter simply referred to as a motor) having a position detection element such as a Hall element.

  Since the motor needs to perform inverter control, it is necessary to apply a control voltage to a control IC for this control. Therefore, this control voltage is generated as a consumption current even in a standby state where the motor is not driven.

In order to prevent the wasteful power consumption in such a standby state from being consumed, a rotation detection unit that detects the rotation position of the rotor when the rotation speed detected by the rotor speed detection unit exceeds a predetermined value. A technique has been proposed in which the energization of the rotation detecting means is stopped when the energization of the rotation detecting means is maintained and below a predetermined value (see, for example, Patent Document 1).
Japanese Patent No. 3736728

  However, in the technique of Patent Document 1, since the structure is such that energization to the rotation detection means is maintained when the rotation speed detected by the speed detection means exceeds a predetermined value, in order to detect this speed, It is necessary to use the rotation position detected from the rotation detection means.

  Therefore, when the energization to the rotation detecting means is stopped, the speed detecting means cannot be detected, so that the operation works well in the vicinity of a predetermined value for determining whether or not to maintain the energization to the rotation detecting means. There is a problem that is not done.

  Therefore, in view of the above problems, the present invention provides a brushless DC motor driving apparatus capable of stopping unnecessary power supply to a position detection element in a standby state.

The present invention includes a brushless DC motor, an inverter circuit that supplies a three-phase drive current to the brushless DC motor, a plurality of position detection elements that detect the position of a rotor of the brushless DC motor, and the position detection element. A position detection unit that determines the position of the rotor based on the detection signal of the motor, a control unit that PWM-controls the inverter circuit based on the speed command signal input from the external device and the position detection signal from the position detection unit The control unit includes a triangular wave oscillation circuit that outputs a triangular wave, a first comparison unit that compares the speed command signal and the triangular wave, and outputs a compared signal, and the first comparison unit. the signal is input, a PWM control unit for outputting a PWM signal, separately from the first comparison unit, the speed command signal is input, comparing the speed command signal and the threshold value, before Brushless having a second comparing section that the speed command signal and outputs a start signal when it reaches the threshold value, while the start signal is not input, and a control current control unit for opening the power supply to the position detection element DC motor drive device.

  According to the present invention, since the current to the position detection element is stopped until the speed command signal reaches the threshold value of the brushless DC motor, the power consumption can be reduced.

  Hereinafter, a driving device 12 of a brushless DC motor (hereinafter simply referred to as a motor) 10 according to an embodiment of the present invention will be described with reference to FIGS.

(1) Configuration of Motor 10 and Drive Device 12 Next, the configuration of the motor 10 and the drive device 12 will be described based on FIG.

  The motor 10 is a three-phase motor, and the rotor rotates inside a stator to which a three-phase stator winding is attached.

  The drive device 12 includes an inverter circuit 14, a control unit 16, and a position detection unit 18.

  The inverter circuit 14 is composed of six switching elements, and causes drive currents to flow through the three-phase stator windings of the motor 10 based on the drive signal output from the control unit 16. The inverter circuit 14 is driven by a DC motor voltage VM.

  The controller 16 is driven by the control voltage Vcc, and the speed command voltage Vsp is input from the outside. The control unit 16 includes a comparator 20 to which the speed command voltage Vsp is input, a triangular wave oscillation circuit 22, a timing control unit 24, an energization signal forming unit 26, an upper arm drive circuit 28, a lower arm drive circuit 30, and a control current control unit 32. Consists of. The control unit 16 is formed by one IC.

  The position detection unit 18 includes three Hall ICs 34, 34, 34 provided near the outside of the rotor of the motor 10. The three Hall ICs 34, 34, 34 are supplied with power from the position detection unit 18.

(2) Driving State of Driving Device 12 Next, a case where the motor 10 is rotated using the driving device 12 will be described.

  A speed command voltage Vsp input from the outside is input to the comparator, and compared with the triangular wave from the triangular wave oscillation circuit 22 to output a pulse signal. This pulse-shaped signal is the original signal of the PWM signal and is input to the PWM control unit 23 to form a PWM signal, which is input to the timing control unit 24.

  In the timing control unit 24, the timing such as the rise of the PWM signal is adjusted based on the rotational speed described later, and is input to the energization signal forming unit 26.

  The energization signal forming unit 26 adjusts and outputs a voltage value corresponding to the upper and lower arm drive circuits 28 and 30 based on the adjusted PWM signal.

  The upper arm drive circuit 28 and the lower arm drive circuit 30 output ON / OFF drive signals to the respective switching elements of the inverter circuit 14.

  In the inverter circuit 14, the six switching elements are turned on / off in response to the drive signal, and a three-phase drive current is output so as to rotate the motor 10 at a rotation speed corresponding to the speed command voltage Vsp.

  On the other hand, the position detection unit 18 detects the rotational position of the rotor based on the position detection signals from the three Hall ICs 34, 34, 34 provided in the motor 10, and outputs it to the control current control unit 32. The timing control unit 24 calculates the current rotation speed of the rotor based on the rotor position sent from the control current control unit 32, and performs feedback control so as to match the speed command voltage Vsp.

(4) Operation in Standby State As described in the background art, it is necessary to keep the power consumption of the control voltage Vcc low. Therefore, in the present embodiment, supply of current to the position detection unit 18 and the three Hall ICs 34, 34, 34 is stopped in the standby state.

  The structure will be described with reference to FIGS.

  FIG. 2 is a block diagram of the control current control unit 32, and the control current control unit 32 is provided with an all-off comparator 36. A speed command voltage Vsp is input to one input terminal of the all-off comparator 36, and an operation start voltage similar to that of the motor 10 is applied to the other input terminal.

  When the speed command voltage Vsp does not reach the operation start voltage as shown in FIG. 3, the output signal is not output from the all-off comparator 36, and the position detection power supply for supplying power to the position detection unit 18 is provided. Between the two.

  On the other hand, when the operation start voltage is reached, an output signal is output from the all-off comparator 36, power is supplied from the position detection power source to the position detection unit 18, and the three Hall ICs 34, 34, 34 also operate. The rotation speed can be detected.

(5) Effect According to the present embodiment, the speed command voltage is compared with the operation start voltage, and the position detection unit 18 and the three are detected until the speed command voltage reaches the operation start voltage (that is, in the standby state). Since no current is supplied to the Hall ICs 34, 34, 34, power consumption can be reduced.

(6) Modification Examples The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

(6-1) Modification 1
First, Modification Example 1 will be described.

  In the above embodiment, the current path from the IC constituting the control unit 16 to the position detection unit 18 is interrupted. Instead, the power IC and the control IC are used in a period in which the speed command voltage Vsp does not reach the operation start voltage. A reset signal may be output between them to interrupt the current to the position detector 18.

  That is, the inverter circuit 14 and the upper and lower arm drive circuits 28 and 30 are formed by one power IC, and the comparator 20, the triangular wave oscillation circuit 22, the PWM control unit 23, the timing control unit 24, the energization signal forming unit 26, and the control current control. When the unit 32 is formed by a single control IC and the speed command voltage Vsp does not reach the operation start voltage, a reset signal is continuously output between the power IC and the control IC, so that the position detection unit 18 can be output. To interrupt the current.

  Even in the first modification, the current to the position detection unit 18 and the Hall ICs 34, 34, 34 in the standby state is interrupted, so that power consumption can be reduced.

(6-2) Modification 2
Next, Modification Example 2 will be described.

  In this modified example 2, as shown in FIG. 4, the triangular wave oscillated from the triangular wave oscillation circuit 22 is compared with the rising speed command voltage Vsp, and the period of voltage or the like in which the triangular wave and the speed command voltage Vsp overlap is as follows. The current to the position detector 18 is cut off.

  Even in this modified example 2, it is possible to reduce the power consumption as in the above embodiment.

It is a block diagram of a motor and a drive device showing one embodiment of the present invention. It is a block diagram of a control current control part. It is a graph which shows the relationship between a speed command voltage and an operation start voltage. It is a graph which shows the relationship between the triangular wave and speed command voltage in the example 2 of a change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Brushless DC motor 12 Drive apparatus 14 Inverter circuit 16 Control part 18 Position detection part 20 Comparator 22 Triangle wave oscillation circuit 23 PWM control part 24 Timing control part 26 Current supply signal formation part 28 Upper arm drive circuit 30 Lower arm drive circuit 32 Control current control Part 34 Hall IC
36 All-off comparator

Claims (2)

A brushless DC motor;
An inverter circuit for supplying a three-phase drive current to the brushless DC motor;
A plurality of position detection elements for detecting the position of the rotor of the brushless DC motor;
A position detection unit that determines the position of the rotor based on a detection signal from the position detection element;
A speed command signal input from an external device, and a control unit that PWM-controls the inverter circuit based on a position detection signal from the position detection unit,
The controller is
A triangular wave oscillation circuit that outputs a triangular wave;
A first comparison unit that compares the speed command signal with the triangular wave and outputs a compared signal;
A PWM controller that receives a signal from the first comparator and outputs a PWM signal;
Separately from the first comparison unit , a second comparison unit that receives the speed command signal, compares the speed command signal with a threshold value, and outputs a start signal when the speed command signal reaches the threshold value; ,
A control current control unit that releases power supply to the position detection element while the start signal is not input;
A brushless DC motor drive device having
The control current controller is
While the start signal is not input , the power supply to the position detection unit is released.
The brushless DC motor drive device according to claim 1.

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