JP2005312216A - Brushless dc motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless DC motor drive in which a position detecting element is used while eliminating the effect of its variation, and rotation can be controlled accurately and inexpensively without using vector control or an intricate system. <P>SOLUTION: One Hall IC 30 for detecting the rotational position of a rotor is provided, and one period of a phase signal HU outputted from the Hall IC 30 is measured by a counter circuit 20. Using the measured period as one period, a sine wave pattern circuit 32 generates the modulation signal of U phase for which the amplitude is determined based on a speed command signal. Subsequently, the modulation signal of V phase having phase shift of 120° from the modulation signal of U phase is generated, and the modulation signal of W phase having phase shift of 240° from the modulation signal of U phase is generated. The modulation signal of each phase is compared with a triangular wave and a PWM signal is generated and then each switching element of an inverter circuit 14 is turned on/off based on the PWM signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive device that drives a brushless DC motor by an inverter circuit.

Conventionally, in a three-phase brushless DC motor, the magnetic flux of the rotor magnet is detected by three position detection elements such as a Hall IC and a Hall element, and based on the phase signal of each phase from the three position detection elements. The position of the rotor is estimated and PWM control is performed by switching energization, and the rotation is controlled by turning on / off each switching element of the inverter circuit (for example, see Patent Document 1).
JP 2002-101683 A

  When using the three position detection elements as described above, the position detection elements are affected by mutual influences such as mounting position variations, characteristic variations, and rotor magnet variations of the three position detection elements. Therefore, there is a problem that the energization width of the phase signal from each other fluctuates, uneven rotation occurs, and noise is generated.

  In view of the above problems, the present invention is a brushless DC motor that can accurately control the rotation at low cost without using the influence of the variation and using vector control or a complicated system while using the position detection element. A driving apparatus is provided.

  According to the first aspect of the present invention, an inverter circuit that supplies a drive current to a stator winding of each phase of a three-phase brushless DC motor, and a PWM signal based on a speed command signal input from the outside are used to generate a PWM signal. A brushless DC motor drive device comprising: a PWM signal generating means for generating; and a drive means for outputting a switching signal for turning on / off each switching element constituting the inverter circuit based on the PWM signal. There is provided at least one position detecting element for detecting the rotational position of the child, and counter means for measuring the period time of one cycle of the phase signal output from the position detecting element is provided. A U-phase modulation signal having a period and an amplitude determined based on the speed command signal is generated, and the U-phase modulation signal is set to 1 Modulation signal generation means for generating a V-phase modulation signal by shifting by 0 ° and generating a W-phase modulation signal by shifting the U-phase modulation signal by 240 ° is provided. The brushless DC motor drive apparatus is characterized in that a PWM signal is generated by comparing the modulation signal of the above and a triangular wave.

  The invention according to claim 2 is the brushless DC motor drive device according to claim 1, wherein the position detection means generates a modulation signal of each phase by a two-phase modulation method.

  The invention according to claim 3 is provided with a starting control means, and the starting control means energizes a predetermined two-phase stator winding for a certain period of time when the brushless DC motor is started. When the rotor is fixed, a modulation signal that performs forced commutation at a preset start cycle is generated, and the one position detection element outputs a phase signal having a cycle corresponding to the start cycle, the one 2. The brushless DC motor driving apparatus according to claim 1, wherein the rotation is controlled based on a phase signal of the position detecting element.

  According to a fourth aspect of the present invention, there is provided an activation control means and two position detection elements in addition to the one position detection element, and the activation control means is configured so that the brushless DC motor is activated when the brushless DC motor is activated. A modulation signal of each phase is generated based on the phase signal of each phase from the three position detection elements, the rotor is rotated n times based on the modulation signal of each phase, and the rotor is rotated n times 2. The brushless DC motor driving device according to claim 1, wherein the rotation is controlled based on a phase signal of the one position detecting element after the rotation.

  In the brushless DC motor driving apparatus according to the first aspect of the present invention, a three-phase modulation signal is generated based on the phase signal output from one position detection element, and the three-phase modulation signal and the triangular wave are generated. Since the PWM signal is generated by comparing the two, there is no influence of variations in the three position detection elements as in the prior art, and rotation unevenness does not occur.

  In the brushless DC motor driving apparatus according to the second aspect of the invention, since the position detecting means generates the modulation signal of each phase by the two-phase modulation method, the switching loss of the switching element in the inverter circuit can be reduced. .

  A brushless DC motor driving apparatus according to a third aspect of the present invention will be described.

  In the brushless DC motor driving apparatus according to claim 1 or 2, since the rotation is controlled by one position detection element, the rotation direction is not determined at the time of activation. Therefore, at the time of start-up, the start-up control means fixes a rotor by energizing a two-phase stator winding fixed in advance for a certain period of time, and performs a forced commutation at a preset start-up cycle. Is generated. The rotation is controlled based on the phase signal from one position detection element according to claim 1 or 2 from when the one position detection element outputs a phase signal having a period corresponding to the activation period. Thereby, the rotation can be easily controlled even at the time of activation.

  A brushless DC motor driving apparatus according to a fourth aspect of the present invention will be described.

  In the brushless DC motor driving apparatus according to claim 1 or 2, since the rotation is controlled by one position detection element, the rotation direction is not determined at the time of activation. Therefore, at the time of activation, the activation control unit generates a modulation signal of each phase based on the phase signal of each phase from the three position detection elements, and rotates the rotor n times based on the modulation signal of each phase. After the rotor is rotated n times, the rotation is controlled based on the phase signal of one detection element described in claim 1 or claim 2. As a result, the activation can be performed reliably, and during normal rotation, the rotation is controlled based on one position detection element, so that it is not affected by variations in the three position detection elements.

(First embodiment)
Hereinafter, a driving device 12 of a three-phase brushless DC motor (hereinafter simply referred to as a motor) 10 according to a first embodiment of the present invention will be described. The motor 10 is a drive source for the fan device.

(1) Configuration of Drive Device 12 The configuration of the drive device 12 will be described based on the block diagram of FIG.

  The drive device 12 includes an inverter circuit 14, a drive circuit 16, a position estimation circuit 18, a counter circuit 20, a system clock generation circuit 22, a triangular wave generation circuit 24, and a control unit 26 that is a microcomputer and is a main control unit of the fan device. Has been. The drive circuit 16 includes a sine wave pattern circuit 32, a comparator 34, and a NOT circuit 36 for each phase.

  The inverter circuit 14 includes six MOSFETs, two MOSFETs are connected in series, and three sets of these two FETs connected in series are connected in parallel. A stator winding 28 of each phase is connected between two MOSFETs connected in series. In addition, a diode for current return is connected in parallel with each MOSFET. Further, the DC power supply + Vm is connected to the drain terminals of the three MOSFETs.

  One Hall IC 30 for detecting the position of the magnet of the rotor of the motor 10 is provided. The phase signal HU from the Hall IC 30 is input to the position detection circuit 18. The position detection circuit 18 outputs the clock signal from the system clock generation circuit 22 and the input phase signal HU to the counter circuit 20. As shown in FIG. 2, the counter circuit 20 counts the time from the falling position of the phase signal HU to the next falling position and sets this as one cycle. This one cycle varies depending on the number of rotations. In the case of FIG. 2, the first cycle is T1, and the next cycle is T2.

  The time of one cycle counted by the counter circuit 20 and the falling timing of the phase signal are input to the sine wave pattern circuit 32 of each phase of the drive circuit 16.

  The U-phase sine wave pattern circuit 32 generates a sine wave U-phase modulation signal SU by the two-phase modulation method. The timing at which the U-phase modulation signal SU is output is determined by the falling edge of the phase signal, the modulation signal cycle is set to be the same as the input cycle (for example, T1), and the amplitude is based on the voltage of the speed command signal. Determined.

  Similarly, the V-phase modulation signal SV is generated in the V-phase sine wave pattern circuit 32, but the generation timing of the V-phase modulation signal SV is shifted by 120 ° with respect to the U-phase modulation signal SU. Is generated.

  Similarly, the W-phase modulation signal SW is generated in the W-phase sine wave pattern circuit 32. The W-phase modulation signal SW is generated in a state of being shifted by 240 ° with respect to the U-phase modulation signal SU.

  Note that one cycle of the modulation signal of each phase differs depending on one cycle of the input phase signal, and when T1 is input, one cycle of T1 is set, and the number of rotations changes and one cycle becomes T2. In this case, one cycle is T2.

  When the modulation signal for each phase is generated in this way, it is input to the comparator 34 for each phase. The comparator 34 of each phase receives the triangular wave input from the triangular wave generating circuit 24 and compares the triangular wave with the input modulation signal, and the comparator 34 outputs a PWM signal. The triangular wave generation circuit 24 generates a triangular wave by the clock signal from the system clock generation circuit 22.

  The PWM signal output from the U-phase comparator 34 is input to the gate terminal of the U-phase upper MOSFET of the inverter circuit 14. The PWM signal output from the U-phase comparator 34 is inverted by the NOT circuit 36, and this inverted PWM signal is input to the gate terminal of the lower-stage MOSFET of the U phase.

  Similarly, the PWM signal output from the U-phase comparator 34 and the PWM signal output from the W-phase comparator 34 are also input to the upper and lower MOSFETs of the U phase and the upper and lower MOSFETs of the W phase, respectively.

(2) Control state during normal rotation The control state of the drive device 10 during normal rotation other than during startup will be described.

  When the rotor of the motor 10 is rotating at a predetermined speed, a phase signal HU is output by a change in the magnetic flux of the rotor magnet.

  The phase signal HU is counted by the position estimation circuit 18 and the counter circuit 20 at the time of falling and one cycle time, and is input to the sine wave pattern circuit 32 of each phase. In the U phase, a modulation signal is generated with reference to the time of falling. In this case, the amplitude changes depending on the voltage of the speed command signal, and one period is set to be the same as one period of the phase signal. The V-phase modulation signal is generated in a state shifted by 120 ° with respect to the U-phase modulation signal, and the W-phase modulation signal is generated in a state shifted by 240 ° with respect to the U-phase modulation signal.

  For this reason, there is no variation based on the signals from the three modulation signals as in the conventional case, and the modulation signal shifted by 120 ° is output accurately. Therefore, variation in the rotation of the rotor by the PWM signal based on this is generated. do not do. Moreover, since vector control and a complicated system are not used, cost can be reduced.

(3) Control method at start-up At the time of normal rotation as described above, the rotation direction is known because the rotor has already been rotated, but at start-up, the rotation direction is not fixed, so one hole The IC 30 is difficult to control. At the start-up in this start-up control method, by energizing a predetermined two-phase stator winding for a certain time, fixing the position of the rotor of the motor 10, and then forcibly commutating to start-up the motor 10 The rotation direction is determined, and after startup, the normal rotation control method described above is switched.

  The activation control method will be described based on the flowchart of FIG.

  In step 1, the rotor position is fixed by energizing a predetermined two-phase stator winding for a predetermined time, that is, by performing DC excitation.

  In step 2, a start phase signal for performing forced commutation at a preset cycle is output from the control unit 26 to the position estimation circuit 18.

  In step 3, since the rotor starts to rotate based on the start-up phase signal, the Hall IC 30 detects this and outputs the phase signal to the position detection circuit 18. In the position detection circuit 18, when the input phase signal coincides with the starting phase signal, the process proceeds to step 4 and shifts to the normal rotation control described above. On the other hand, if the input phase signal does not coincide with the starting phase signal, the process returns to step 1 to continue the DC excitation.

  As described above, at the time of activation, activation is performed by a preset activation phase signal, and then the normal rotation control described above is performed, so that even one of the hall ICs 30 can be activated at the time of activation.

(Second Embodiment)
The activation control method according to the second embodiment will be described with reference to FIG.

  In the startup control method of the first embodiment, startup is performed based on a preset startup phase signal. In the present embodiment, three Hall ICs are provided as in the prior art, and at startup, this 3 It is activated using a single Hall IC.

  The activation control method will be described based on the flowchart of FIG.

  When the motor stops in step 11 and an activation signal is input from the outside in step 12, the control unit 26 starts energization in step 13.

  In Step 14, when the rotor starts to rotate due to energization, the three Hall ICs output the phase signal of each phase in the same manner as in the prior art, and generate the PWM signal based on the phase signal of each phase to control the rotation. To do.

  In step 15, when the rotor rotates continuously n times, the normal rotation control described above is performed. When the rotor does not reach n times, rotation control is performed using the three Hall ICs 30.

  In the activation control method of the second embodiment, since three Hall ICs 30 are used only at the time of activation and control is performed by one Hall IC 30 at the time of normal rotation, uneven rotation or the like does not occur at the time of normal rotation.

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

  The brushless DC motor drive device of the present invention is suitable as a drive source that does not change the rotational speed of a fan device or the like.

It is a block diagram of the drive device which shows the 1st Embodiment of this invention. It is a time chart of a drive device. It is a flowchart in a starting control method. It is a flowchart of the starting control method of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 Drive circuit 18 Position estimation circuit 20 Counter circuit 22 System clock generation circuit 24 Triangular wave generation circuit 26 Control part 28 Stator winding 30 Hall IC
32 Sine wave pattern circuit 34 Comparator 36 NOT circuit

Claims (4)

An inverter circuit for supplying drive current to the stator windings of each phase of the three-phase brushless DC motor;
PWM signal generating means for generating a PWM signal by performing PWM control based on a speed command signal input from the outside;
Drive means for outputting a switching signal for turning on / off each switching element constituting the inverter circuit based on the PWM signal;
In the drive device of the brushless DC motor having
At least one position detecting element for detecting the rotational position of the rotor is provided;
Counter means for measuring a cycle time of one cycle of the phase signal output from the position detection element is provided;
A U-phase modulation signal whose amplitude is determined based on the speed command signal is generated with the measured cycle time as one cycle, and the U-phase modulation signal is shifted by 120 ° to obtain a V-phase modulation signal. Modulation signal generation means for generating and generating a W-phase modulation signal by shifting the U-phase modulation signal by 240 °;
The PWM signal generating means includes
The PWM signal is generated by comparing the modulation signal of each phase and the triangular wave. The brushless DC motor driving apparatus according to claim 1, wherein the position detecting means generates a modulated signal of each phase by a two-phase modulation method. A starting control means is provided,
The activation control means includes:
When starting up the brushless DC motor, a predetermined two-phase stator winding is energized for a certain period of time to fix the rotor,
Generate a modulation signal that performs forced commutation at a preset start cycle,
2. The brushless according to claim 1, wherein when one position detection element outputs a phase signal having a period corresponding to the activation period, rotation is controlled based on the phase signal of the one position detection element. 3. DC motor drive device. In addition to the starting control means and the one position detecting element, there are two position detecting elements,
The activation control means includes:
When the brushless DC motor is started, a modulation signal of each phase is generated based on the phase signal of each phase from the three position detection elements, and the rotor is rotated n times based on the modulation signal of each phase. Rotate,
The brushless DC motor drive device according to claim 1, wherein the rotation is controlled based on a phase signal of the one position detecting element after the rotor is rotated n times.

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