JP3285318B2 - Drive device for brushless DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a brushless DC motor driving apparatus applied to a brushless DC motor used in office equipment, industrial machines, medical machines, and the like.

[0002]

2. Description of the Related Art A conventional brushless DC motor driving apparatus will be described with reference to FIGS. FIG. 3 is a block diagram showing a configuration of a conventional brushless DC motor driving device. As shown in FIG. 1, the conventional brushless DC motor driving device includes a driving element 2 for driving a brushless DC motor 3, a speed control circuit 1, a rotational speed detecting unit 12, and a current detecting unit 14. The configuration of the driving element 2 will be described later with reference to FIG. In this case, the rotation speed detecting means 12 includes a Hall element 5 for detecting a magnetic pole position of a rotor incorporated in the brushless DC motor 3, and a rotation speed signal g which is a voltage signal.
The current detecting means 14 includes a current detecting element 4 for detecting a current flowing through the brushless DC motor 3 and a comparator 8b. Signal j for setting the limit value of the maximum current flowing through the brushless DC motor 3
2, and the comparison signal is supplied to the speed control circuit 1 with the current detection signal d as a control signal. The speed control circuit 1 additionally includes signals h and F from the Hall element 5.
The signal g from the / V converter 6 is also input as a control signal.

In the above configuration, the host controller 1
A, a rotation speed command a, a start / stop signal b,
The rotation direction signal c is input to the speed control circuit 1, and the speed control circuit 1 outputs an energization signal e for driving the drive element 2 for controlling the rotation speed of the brushless DC motor 3. Here, for example, when the start / stop signal b is on (start) and the current detection signal d from the current detection means 14 is off, the energization signal e is transmitted to the brushless DC motor 3 Drive. An output signal (hereinafter, referred to as a Hall element signal h) of the Hall element 5 of the rotation speed detecting means 12 for detecting a magnetic pole position of a rotor built in the brushless DC motor 3 is subjected to a rotation speed signal by an F / V converter 6. g and input to the speed control circuit 1. Also,
In the speed control circuit 1, an energization signal e corresponding to the rotation speed command a from the host controller 1A is generated. At this time, the speed control circuit 1 controls the current detection signal d generated by the current detection means 14 so as not to exceed the set limit value.

[0004]

By the way, in the conventional brushless DC motor driving device shown in FIG. 3, the upper controller 1 is driven during the forward rotation of the brushless DC motor 3.
A, when the rotation direction signal c input from A is switched and the reverse rotation drive is performed, the regenerative current due to the induced voltage generated in proportion to the rotation speed of the brushless DC motor 3 is detected by the current detection element 4.
There was a problem that it could not be detected. The reason for this is shown in FIG.
This will be described with reference to FIG.

FIG. 4 is a connection diagram showing a circuit configuration of the driving element 2 and a relationship between the driving power supply 2A and a brushless DC motor 3 which is a load. Brushless DC motor 3
3 shows a current path flowing through the circuit. As shown in the figure, the driving element 2 has six driving transistors 2a, 2
c, 2e, 2g, 2i, 2k and six flywheel diodes 2b, 2d, 2f, 2h, 2j, 2m. In the drive element 2, when the drive transistors 2a and 2i are both turned on by the energization signal e generated by the speed control circuit 1 shown in FIG.
From A, a current m returning to the drive power supply 2A flows through the drive transistor 2a, the motor coil 3a, the motor coil 3b, the drive transistor 2i, and the current detection element 4. Next, when the Hall element signal h is switched by the rotation of the brushless DC motor 3, both the drive transistors 2e and 2i are turned on by the energization signal e, and the drive transistor 2e, the motor coil 3c, the motor coil 3
b, via the drive transistor 2i and the current detection element 4,
A current n returning to the drive power supply 2A flows. At this time, the regenerative current o returns from the motor coil 3a to the motor coil 3a via the motor coil 3b, the drive transistor 2i, and the flywheel diode 2h due to the induced voltage generated from the motor coil 3a.

As described above, the regenerative current o is
Since the current does not pass through the current detecting element 4, the current detecting means 14
Cannot detect the regenerative current o, and the speed control circuit 1 cannot limit the regenerative current o. That is, as described above, in the conventional brushless DC motor driving device shown in FIG. 3, when the reverse rotation drive is performed, the regenerative current due to the induced voltage generated in proportion to the rotation speed of the brushless DC motor 3 (see FIG. (The regenerative current o shown below, the same applies hereinafter) cannot be detected by the current detecting element 4. As a result, the brushless DC motor 3
Since the current obtained by adding the regenerative current o at the time of the reverse rotation driving at the maximum speed and the maximum current of the brushless DC motor 3 limited by the speed control circuit 1 flows to the drive transistor 2i, the magnitude of the regenerative current o is sufficiently considered, A drive element having a larger rated current than the drive element 2 when the brushless DC motor 3 is not driven in the reverse direction must be used,
There is a problem that the cost of the driving element increases and the shape of the driving device also increases.

The present invention solves the above-mentioned problems (problems),
Provided is a brushless DC motor drive device that suppresses an excessive current generated by the reverse drive of the brushless DC motor and uses a drive element with a small rated current to realize a compact and low-cost drive device. The purpose is to do.

[0008]

DISCLOSURE OF THE INVENTION The brushless DC of the present invention
In order to solve the above-mentioned problems, a motor driving device includes a driving element for driving a brushless DC motor, a current detection unit for the brushless DC motor, a rotation speed detection unit, a host controller, and a rotation direction from the host controller. A speed control circuit for receiving a signal, a current detection signal from the current detection means and a rotation speed signal from the rotation speed detection means, and generating an energization signal for the drive element. Brushless D
A current limiting control circuit including a rotation direction detecting means for the C motor; receiving the rotation direction signal, a rotation direction detection signal from the rotation direction detection means, and a rotation speed signal from the rotation speed detection means; By detecting the reverse drive of the brushless DC motor and generating a current limit switching signal,
The reference signal for limiting the maximum current flowing through the brushless DC motor during the forward drive is automatically switched to the reference signal for limiting the maximum current to a smaller value. As a result, an excessively large current of the brushless DC motor can be suppressed, so that a driving element having a large rated current does not need to be used, and the rated current can be made smaller than that of a conventional brushless DC motor driving device. The drive device can be reduced in size and cost.

The current limit control circuit may be a rotation direction detection circuit which receives a Hall element signal h from the rotation speed detection means and outputs a rotation direction detection signal f. And the rotation direction detection signal f
And an EX-OR gate that receives the rotation direction signal c as input and outputs a rotation direction determination signal k, and a comparator that compares the reference signal j1 with the rotation speed signal g from the rotation speed detection means to generate a comparison signal i. An AND gate that receives the rotation direction determination signal k and the comparison signal i and outputs a current limit switching signal p, and receives one of the current limit switching signal p and receives one of a reference signal j2 and a reference signal j3. What is necessary is just to have the structure provided with the changeover switch.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brushless DC motor driving apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of a brushless DC motor driving device according to the present invention. As shown in FIG. 1, the driving device of the present invention is a conventional brushless DC motor driving device shown in FIG. Is characterized in that a current limit control circuit 13 is added to the configuration. In the following description, the same components as those of the conventional driving device are denoted by the same reference numerals as in FIG. 3, and the description is omitted.

As shown in FIG. 1, a current limit control circuit 13 provided in the drive device of the present invention receives a Hall element signal h from the rotational speed detecting means 12 as a rotational direction detecting means, and outputs a rotational direction detecting signal f Is used. Further, the current limit control circuit 13 receives the rotation direction detection signal f from the rotation direction detection circuit 9 and the rotation direction signal c from the host controller 1A, and outputs a rotation direction determination signal k EX (Exclusive) -O.
R gate 10, reference signal j1 and rotational speed detecting means 12
The comparator 8a compares the rotation speed signal g from the comparator 8a to generate a comparison signal i, the rotation direction discrimination signal k from the EX-OR gate 10, and the comparison signal i from the comparator 8a.
, And an AND gate 11 that outputs a current limit switching signal p, and a switch 7 that receives the current limit switching signal p and switches to one of a reference signal j2 and a reference signal j3. .

Next, referring to FIG. 2, the brushless D of the present invention will be described.
The operation of the current limit control circuit 13 used in the drive device for the C motor will be described. FIG. 2 is a flowchart showing the operation of the current limit control circuit 13. As shown in the figure, when the rotation direction signal c from the host controller 1A of FIG. 1 matches the rotation direction detection signal f output from the rotation direction detection circuit 9, the output of the EX-OR gate 10 ( The rotation direction discrimination signal k) becomes low (L). On the other hand, when the rotation speed signal g from the rotation speed detection means 12 is smaller than the reference signal j1, the comparison signal i which is the output of the comparator 8a becomes (L), so that the output of the AND gate 11 (the current limit switching signal p ) Are both (L). At this time, the changeover switch 7 receives the output of the AND gate 11 (current limit changeover signal p) and connects the comparator 8b to the reference signal j2. When the rotation direction signal c from the host controller 1A does not match the rotation direction detection signal f output from the rotation direction detection circuit 9, the output of the EX-OR gate 10 (rotation direction discrimination signal k) is high. (H). At this time, the brushless DC motor 3 is in a reverse drive state or stopped (the output of the rotation direction detection circuit 9 is undefined when the brushless DC motor 3 is stopped). Here, when the rotation speed signal g is larger than the reference signal j1, the comparison signal i, which is the output of the comparator 8a, becomes (H), and it can be detected that the brushless DC motor 3 is not stopped. As a result, the output of the AND gate 11 (current limit switching signal p) becomes (H) only when the brushless DC motor 3 is driven in reverse rotation, and the switch 7 receives the output of the AND gate 11 (current limit switching signal p). , Comparator 8b and reference signal j3.

Therefore, the reference signal j3 is set so as to limit the maximum current of the brushless DC motor 3 to a sufficiently small value in consideration of the regenerative current generated when the brushless DC motor 3 is driven in the reverse direction. During the reverse rotation drive, an excessive current of the brushless DC motor 3 can be suppressed. Therefore, the brushless D of the present invention
In the drive device of the C motor, the drive element 2 having a large rated current is used.
Of the conventional brushless DC shown in FIG.
The rated current can be made smaller than that of the drive element 2 used in the motor drive device, and the drive device can be reduced in size and cost.

[0014]

Since the brushless DC motor driving device of the present invention is constructed as described above, the reference signal is controlled so as to limit the maximum current of the brushless DC motor to a sufficiently small value when the brushless DC motor is driven in reverse rotation. By switching, the excessive current of the brushless DC motor can be suppressed, so that the drive element 2 having a large rated current is not required, and the rated current is smaller than that of the conventional brushless DC motor drive device. As a result, the drive device can be reduced in size and cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a drive device for a brushless DC motor according to the present invention.

FIG. 2 is a flowchart showing an operation of a current limit control circuit used in the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional brushless DC motor driving device.

FIG. 4 is a connection diagram showing a circuit configuration of a driving element and a relationship between a driving power supply thereof and a brushless DC motor which is a load in a conventional brushless DC motor driving apparatus. It shows the route of the.

[Explanation of symbols]

 1: Speed control circuit 1A: Host controller 2: Drive element 3: Brushless DC motor 5: Hall element 7: Changeover switch 8a, 8b: Comparator 9: Rotation direction detection circuit 10: EX-OR gate 11: AND gate 12: Rotation speed detection means 13: Current limit control circuit 14: Current detection means c: Rotation direction signal d: Current detection signal f: Rotation direction detection signal g: Rotation speed signal h: Hall element signal i: Comparison signal j1 to j3: Reference Signal p: Current limit switching signal

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/22 H02P 6/24

Claims (2)

(57) [Claims] 1. A driving element for driving a brushless DC motor, a current detecting means of the brushless DC motor, a rotational speed detecting means, a host controller, a rotation direction signal from the host controller, and a current from the current detecting means. A speed control circuit for receiving a detection signal and a rotation speed signal from the rotation speed detection means and generating an energization signal for the drive element; and a brushless DC motor drive device comprising: A current limiting control circuit provided for receiving the rotation direction signal, the rotation direction detection signal from the rotation direction detection unit, and the rotation speed signal from the rotation speed detection unit, and detecting the reverse rotation drive of the brushless DC motor. Then, by generating the current limit switching signal, the maximum current flowing through the brushless DC motor during the forward drive is reduced. Brushless D, characterized in that the reference signal to limit and to switch automatically to the reference signal to limit to suppress smaller the maximum current
Drive device for C motor. 2. A rotation direction detection circuit for receiving a Hall element signal h from said rotation speed detection means and outputting a rotation direction detection signal f, said current limit control circuit comprising: a rotation direction detection signal f; An EX-OR gate which receives the signal c as an input and outputs a rotation direction determination signal k, and a reference signal j1
And a comparator that compares the rotation speed signal g from the rotation speed detection means to generate a comparison signal i, and an AND that receives the rotation direction determination signal k and the comparison signal i as inputs and outputs a current limit switching signal p. 2. The brushless DC motor drive device according to claim 1, further comprising a gate, and a changeover switch that receives the current limit changeover signal p and switches between a reference signal j2 and a reference signal j3. .