JP3481751B2 - Drive device for DC motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a DC motor. 2. Description of the Related Art FIG. 5 is a circuit diagram showing an electric configuration of a typical driving circuit 10. In the following, reference is made to FIG. Conventionally, in the field of driving automatic doors, for example, 3
A phase DC brushless motor (hereinafter, motor) 1 is used. In such a motor 1, the stator 2 is provided with 3n coils, for example, three coils 3, 4 and 5, and the N pole and the S pole are alternately magnetized in the circumferential direction as the rotor 6,
As an example, a permanent magnet having two magnetic poles is used. In addition, the motor 1 is provided with a magnetic pole detection element 7 including, for example, three Hall elements, and detects the rotation speed of the motor 1. Further, a transistor that supplies a driving current to the coils 3 to 5 (hereinafter, sometimes referred to as an upper transistor) and a transistor into which current from the coils 2 to 4 flows (hereinafter, sometimes referred to as a lower transistor). Is used for each of the coils 3 to 5. In the inverter circuit 8 used for the three-phase motor, three transistors Q1,
Q2, Q3, Q4, Q5, Q6 (hereinafter collectively referred to as Q
May be used), and transistors Q1, Q
2, Q3, Q4, Q5, and Q6 have transistors Q
Diodes D1, D2, D3, D4, D5, D with the source sides of 1, Q2, Q3, Q4, Q5, Q6 as cathodes
6 are transistors Q1, Q2, Q3, Q4, Q5,
Each is connected in parallel with Q6. Further, the upper transistor Q1, Q2, Q3 and the lower transistor Q
4, a DC power supply 9 is provided between Q5 and Q6. The detection signal PS from the magnetic pole detection element 7
Is input to a drive control circuit (not shown) for controlling the number of rotations of the motor 1, and the drive control circuit
An amplitude-modulated pulse signal is generated based on S and a speed signal corresponding to a predetermined rotation speed. Each transistor Q of the inverter circuit 7 is turned on / off by the pulse signal so that the rotation speed of the motor 1 matches the predetermined rotation speed. FIG. 6 is a timing chart for explaining the operation of the conventional motor driving device. FIG. 6 (1) to (3)
Is a detection signal PSU for each phase from the magnetic pole detection element,
6 (4) to 6 (6) show drive control signals UH, VH, WH input to the upper transistor.
6 (7) to 6 (9) show drive control signals UL, VL, WL input to the lower transistor.
(10) shows the modulation signal PWM for amplitude modulation generated in the drive control circuit, and FIG. 6 (11) shows a reference pulse PG generated in connection with the motor. In this prior art drive control circuit, as shown in FIG. 6, the motor is driven in a six-step, 120-degree conduction mode for each phase. Further, this control method is a so-called one side chopper type. That is, focusing on the driving of the U-phase as an example, when the upper-stage U-phase transistor is turned on, the drive control circuit keeps the high level for the entire conduction period and maintains the low level for the entire cutoff period. Drive control signal UH is output to the U-phase transistor, and is a pulse-like signal having the same cycle as the modulation signal PWM over the entire conduction period, and maintains a low level over the entire cut-off period. UL is output to the lower U-phase transistor. In the conventional driving method, control for outputting a pulse-like driving signal during the conduction period of the transistor is performed only for the lower transistor.
The upper transistor is controlled to maintain a high level over the entire conduction period. Note that the upper and lower transistors may operate in reverse. Therefore, after switching the upper-stage transistor Q1 of the U-phase from the conduction state to the interruption state and switching the lower-stage transistor Q5 of the V-phase from the interruption state to the conduction state, for example, the switching in the period 3-4 in FIG. In a period (hereinafter, referred to as period A), a current flowing through the inverter circuit 7 and the motor 1 flows through a path from the diode D4 → the U-phase coil 3 → the W-phase coil 5 → the diode D3. As a result, a negative potential is generated in the U-phase coil 3 and a positive potential is generated in the W-phase coil 5. In a period immediately before the period A, the upper transistor Q1 of the U phase is in a conductive state, the coil 3 is at a positive potential, the lower transistor Q5 of the V phase is in a cutoff state, and the coil 5 is at a negative potential. Therefore, before and after the timing of switching the upper-stage transistor Q1 of the U-phase from the conductive state to the cut-off state and switching the lower-stage transistor Q5 of the V-phase from the cut-off state to the conductive state, the potentials of the coils 3 and 5 are inverted. 1, a large transient current flows. Such a phenomenon similarly occurs in any of the coils 3 to 5. For this reason, there is a problem that the change in the current flowing through the coil of the motor 1 becomes extremely large, which causes noise and vibration in the motor 1. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to suppress a change in current in a coil of a motor when a switch element for driving the motor switches from a cut-off state to a conductive state. It is another object of the present invention to provide a DC motor drive device that reduces motor noise and vibration. According to a first aspect of the present invention, there is provided a driving apparatus for a DC motor, wherein the DC motor is provided at a predetermined rotational speed on a coil for each phase of the DC motor having a plurality of phase coils. A drive signal to be rotated is output, a switch element in one stage is connected to a positive potential, a switch element in the other stage is connected to a negative potential, and a plurality of switch elements are connected to each other. A drive control means for outputting a drive control signal for outputting a drive signal, wherein the drive control signal is output to any one of the switch elements of each stage from the drive control means, and the drive control signal is at one level. The corresponding switch element is turned on, and the other switch element is turned off when the corresponding switch element is at the other level.
A conduction period for conducting the corresponding switch element and a interruption period for interrupting the corresponding switching element are alternately provided, and a first period predetermined from a start timing of the conduction period is shorter than the first period and the one level and the other level are shorter than the first period. Is repeated so as to maintain the one level in the remaining second period of the conduction period, and the switching timing of one of the switch elements of one stage from the conduction state to the cutoff state is determined by one of the one stage. The switch element is selected near the start timing of the second period in one of the other switch elements corresponding to the switch element, whereby the above object can be achieved. According to the first aspect of the present invention, when the DC motor is driven, a drive signal for rotating the DC motor at a predetermined number of revolutions is applied to the coils of each of the plurality of phase coils of the DC motor. Are output from a plurality of switch elements. A drive control signal is input from the drive control unit to the plurality of switch elements, and the drive signal is output. At this time, with respect to the drive control signal output from the drive control means to any of the switch elements in each stage, the drive control signal conducts the corresponding switch element when it is at one level and turns on the corresponding switch element when it is at the other level. The drive signal is turned off, and the drive signal alternately has a conduction period in which the corresponding switch element is turned on and a cut-off period in which the corresponding switch element is turned off, and a first period predetermined from the start timing of the conduction period is shorter than the first period. One level and the other level are repeated in the period, and one level is maintained in the remaining second period of the conduction period. In a first period determined in advance from the start timing of the conduction period, the control of repeating the one level and the other level in a period shorter than the first period is performed for any transistor in each of the stages. . When driving the motor, one of the upper transistors is turned on, and one of the lower transistors is turned on. All other transistors are turned off. Also,
The timing at which the transistor in the conductive state switches to the cut-off state is near the start timing of the second period in another transistor into which the current flowing from the transistor to the motor flows. At this time, when the transistor that switches from the conductive state to the cut-off state switches to the cut-off state, the other one transistor maintains the conductive state in the second period by the drive signal that maintains one level. At this time, a negative potential is generated in the coil connected to the one-stage switch element, but a negative potential is connected to the other-stage switch element, so that the coil is connected to the other-stage switch element. No positive potential is generated in the coil. Therefore, with respect to the coil corresponding to any of the transistors, the amount of current change in the coil of the motor when the switch element is switched from the conductive state to the cutoff state is suppressed, and the noise and vibration of the motor are reduced. A driving device for a DC motor is realized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. 1 to 4 show an embodiment of the present invention. FIG. 1 is a circuit diagram showing an electric configuration of a motor driving device 21 according to one embodiment of the present invention. FIG. 2 is a circuit diagram of a part of the driving device 21. FIG. 3 is a time chart for explaining the operation of the driving device 21. FIG. 4 is a detailed time chart for explaining the operation of the driving device 21. Hereinafter, FIG. 1 and FIG. 2 will be referred to together. In this embodiment, a motor for driving an automatic door will be described as an example. However, the motor drive circuit of the present invention is not limited to this example. The motor 22 of this embodiment is, for example, three-phase and includes a stator 26 having three coils 23, 24, 25. Each of the coils 23, 24, 25 is
It is driven by U-phase, V-phase, and W-phase drive signals from 1. In this embodiment, three magnetic pole detecting elements 27, such as Hall elements, are provided facing the coils 23, 24, and 25, for example, and the detection signals PSU shown in FIGS. , PSV, and PSW (hereinafter sometimes collectively referred to as a code PS). The motor 22
Is a rotor 3 made of a permanent magnet or the like having a pair of magnetic poles.
1 is provided. The driving device 21 includes coils 23, 24, 25
And an inverter circuit 28 for supplying the U-phase, V-phase and W-phase drive signals, respectively. Inverter circuit 28
Have six transistors Q1, Q2, Q3, Q4, Q
5, Q6 are provided. Transistors Q1, Q2, Q3
Are connected to the positive potential of the DC power supply 29. The drains of the transistors Q1, Q2 and Q3 are
4, connected to the sources of Q5 and Q6. Transistor Q
4, the drains of Q5 and Q6 are connected to the negative potential of DC power supply 29. Transistors Q1, Q4; Q2, Q5; Q
The drive signals of the U-phase, V-phase and W-phase shown in FIGS. 3 (4) to (9) are taken out from the respective connection points of Q3 and Q6. Also, transistors Q1, Q2, Q3, Q4, Q
5 and Q6 include transistors Q1, Q2, Q3, Q
Diodes D1, D2, D3, D4, D5, and D6 having the source sides of 4, Q5, and Q6 as cathodes are connected in parallel with the transistors Q1, Q2, Q3, Q4, Q5, and Q6, respectively. The upper transistors Q1, Q2 and Q
Drive control signals UH, VH, and WH shown in FIGS. 2 (4) to (6) are input to the gate of the third transistor Q.
The drive device 21 is provided with a drive control circuit 30 for inputting the drive control signals UL, VL, WL shown in FIGS. 3 (7) to (9) to the gates of 4, Q5, Q6. Drive control signal U
The timings of H, VH, WL are also shown in FIGS. The drive control circuit 30 has a fixed period and generates a modulation signal PWM shown in FIG. 3 (10) used for pulse modulation, and a PWM generation circuit 31 shown in FIG. 3 (1).
And (3) a pulse generating circuit 32 for outputting a reference pulse PG shown in FIG. 3 (11) obtained by logically converting the PSU, PSV and PSW. Hereinafter, the transistors Q1, Q2, Q3, Q4, Q5, and Q6 are collectively referred to as a transistor Q, and diodes D1, D2, and D
3, D4, D5, and D6 may be collectively referred to as a diode D. The drive control circuit 30 includes the magnetic pole detecting element 2
7, a modulation signal PWM from the PWM generation circuit 31, and a reference pulse PG from the pulse generation circuit 32, a conduction start timing detection circuit for detecting the start timing of the conduction period of each transistor Q. 33
A pulse waveform generating circuit 34 for generating pulse-like signals shown in FIGS. 3 (4) to 3 (9) in synchronization with the modulation signal PWM based on the signals PS, PWM and PG;
And a constant level generating circuit 35 for generating a high level or low level constant signal shown in (4) to (9). The pulse signal from the pulse waveform generation circuit 34 and the constant level signal from the constant level generation circuit 35
As described later, the pulse signal and the constant level signal are switched by the switching operation input to the changeover switch unit 36 and based on the signal from the conduction period detection circuit 33, and the U-phase, V-phase, and W-phase Each time it is output to the corresponding transistor Q of the inverter circuit 28. Hereinafter, the operation of the driving device 21 of the present embodiment will be described. Each of the coils 23, 24, 25 is
Driven by the U-phase, V-phase and W-phase drive signals. 3
The three detection elements 27 detect the magnetic flux densities of the coils 23, 24, and 25 and output detection signals PS1, PS2, and PS3 shown in FIGS. Drive control circuit 30
Is a detection signal PS output from each of the detection elements 27.
And a speed command signal input from the outside, FIG.
(4) to the drive control signal UH shown in FIG.
VH, WH; create and output UL, VL, WL. In the present embodiment, the drive control signals UH, VH, WH for controlling the switching state of the upper transistors Q1, Q2, Q3 of the inverter circuit 28 may be generated or the lower transistors Q4, Q5, Q6 Drive control signals UL, VL, WL for controlling the switching state
Also, as shown in FIGS. 3 (4) to (9), when each transistor Q is switched from the cut-off state to the conduction state, a period of time from the start timing of the full conduction period T0 to the pulse period T1 is determined. , The changeover switch unit 36 switches to the pulse generation circuit 34 side, and FIG.
As shown in (9), a pulse signal synchronized with the modulation signal PWM is output, and in the remaining constant level period T2 of the entire conduction period T0, the changeover switch unit 36 is switched to the constant level output circuit 35 side. As shown in 3 (4) to (9), a signal of a fixed level of a high level or a low level is output. The timing at which the upper-stage conducting transistor Q is switched to the cut-off state is near the start timing of the constant level period T2 in the lower-stage transistor Q into which the current flowing from the transistor Q to the motor 22 flows. At this time, when the transistor Q that switches from the conductive state to the cut-off state switches to the cut-off state, the transistor Q in the lower stage is turned on for the certain level period T.
In 2, the conductive state is maintained by the drive signal that maintains one level. The driving control signals UH, VH,
WH; UL, VL, and WL are input to the corresponding transistors Q1 to Q6, respectively, and each drive control signal U
H, VH, WH: ON / OFF at the same timing as the level change of UL, VL, WL, and the conduction / cutoff state is alternately switched. When the transistors Q are turned on, current flows through the corresponding coils 23, 24, 25, and the motor 22 is driven to rotate. Hereinafter, an example of a characteristic operation of the driving device 21 of the present embodiment will be described. When driving the motor 22, one of the upper transistors Q1 to Q3, for example, the transistor Q1 is turned on as shown in periods 1 to 3 in FIG. The transistor Q4 is turned off, the transistor Q5 is turned on during the pulse period T1 of the transistor Q1, and the transistor Q6 is turned on during the constant level period of the transistor Q1. At this time, the timing at which the transistor Q1 switches from the conductive state to the cutoff state is determined by the timing of the transistor Q1.
Transistor Q into which the current flowing from
6 is near the start timing of the constant level period T2. At this time, the current flowing through the drive circuit 21 and the motor 22 during the period B shown in FIG.
6 → coil 23 → coil 25 → transistor Q3. Therefore, a negative potential is generated in the coil 23. On the other hand, in the period B, the transistor Q3 maintains the conductive state in the constant level period T2 by the drive signal that maintains the high level in the period T2. Thus, the coil 25 is connected to the negative potential of the DC power supply 29, and no positive potential is generated in the coil 25. Such control is performed not only when the phase is switched from the U phase to the V phase but also when the phase is switched for all the phases. The drive circuit 21 of the present embodiment having such a configuration and operation can achieve the following effects. In the driving device 21 of the present embodiment, when the motor 22 is driven, the conduction / cutoff state of each transistor Q that outputs the driving signal is determined in order to determine the driving signal output to the coils 23, 24, and 25 of the motor 22. Drive control signals UH, VH,
Regarding any of the drive control signals WH, UL, VL, and WL, the pulse period T1 determined in advance from the start timing of the entire conduction period T0 is determined as a pulse-like signal having a cycle shorter than the pulse period T1. In the remaining constant level period T2, the high or low constant signal level is maintained. The switching timing of one upper transistor Q from the on state to the off state is determined by the constant level period T2 of the lower transistor Q in which the current flowing from the upper transistor Q to the motor 22 flows.
Is selected near the start timing of the game. The control of the transistor Q outputting a pulse-like signal from the start timing of the full conduction period T0 to the pulse period T1 is performed for any of the transistors Q in each stage. As a result, with respect to the coils 23 to 25 corresponding to any of the transistors Q, FIG.
Compared with the motor driving method using only the high-level or low-level driving control signal described with reference to (4) to (6), the coils 23 to 23 when the upper-stage transistor Q is cut off at the time of phase switching. 25 can be suppressed from changing. Therefore, when the transistor Q for driving the motor 22 switches from the cut-off state to the conductive state, the coils 23, 24, 2
5, the noise and vibration of the motor 22 can be reduced. The following effects can be achieved by using the motor control device according to the first aspect of the present invention. According to the invention of claim 1, when the DC motor is driven, a drive signal for rotating the DC motor at a predetermined number of rotations is supplied to the coil for each phase of the multi-phase coil of the DC motor in a plurality of switch elements. Output from each. A drive control signal is input from the drive control unit to the plurality of switch elements, and the drive signal is output. At this time, with respect to the drive control signal output from the drive control means to any of the switch elements in each stage, the drive control signal conducts the corresponding switch element when it is at one level, and turns off the corresponding switch element when it is at the other level. The drive signal is turned off, and the drive signal alternately has a conduction period in which the corresponding switch element is turned on and a cut-off period in which the corresponding switch element is turned off, and a first period predetermined from the start timing of the conduction period is shorter than the first period. One level and the other level are repeated in the period, and the second
The period is set to maintain one level. When driving the motor, one of the upper transistors is turned on and one of the lower transistors is turned on. All other transistors are turned off. Also,
The timing at which the transistor in the conductive state switches to the cut-off state is near the start timing of the second period in another transistor into which the current flowing from the transistor to the motor flows. At this time, when the transistor that switches from the conductive state to the cut-off state switches to the cut-off state, the other one transistor maintains the conductive state in the second period by the drive signal that maintains one level. At this time, a negative potential is generated in the coil connected to the one-stage switch element, but a negative potential is connected to the other-stage switch element, so that the coil is connected to the other-stage switch element. No positive potential is generated in the coil. Therefore, with respect to the coil corresponding to any of the transistors, the amount of change in current in the coil of the motor when the switch element is switched from the conductive state to the cutoff state is suppressed, and the noise and vibration of the motor are reduced. A driving device for a DC motor is realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a driving device 21 according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a part of the driving device 21. FIG. 3 is a time chart illustrating an operation of the driving device 21. FIG. 4 is a detailed time chart illustrating the operation of the driving device 21. FIG. 5 is a circuit diagram of a conventional driving device 10. FIG. 6 is a time chart for explaining a problem of the conventional example. [Description of Signs] 21 Drive device 22 Motor 23 24, 25 Coil 27 Magnetic pole detection element 28 Inverter circuit 30 Drive control circuit 31 PWM generation circuit 32 Pulse generation circuit 33 Conduction start timing detection circuit 34 Pulse generation circuit 35 Constant level generation circuit 36 Changeover switches D1, D2, D3, D4, D5, D6 Diodes Q1, Q2, Q3, Q4, Q5, Q6 Transistors

Claims (1)

(57) Claims 1. A drive signal for rotating the DC motor at a predetermined number of revolutions is output to a coil for each phase of a DC motor having a plurality of phase coils. A plurality of switch elements, each having a positive potential connected to the switch element and a negative potential connected to the other switch element, and a drive control signal for outputting the drive signal from the plurality of switch elements. A drive control signal output from the drive control means to the switch element in each stage, the drive control signal conducts the corresponding switch element at one level and shuts off the corresponding switch element at the other level. And the drive signal alternately has a conduction period for conducting the corresponding switch element and an interruption period for interruption.
A first period determined from the start timing of the conduction period repeats the one level and the other level in a period shorter than the first period, and is determined so as to maintain the one level in a remaining second period of the conduction period. The switching timing of one of the switch elements in one stage from the conductive state to the cutoff state is near the start timing of the second period in the one switch element in the other stage corresponding to the one switch element in the one stage. DC motor drive device selected for.