JP2002305892A - Drive for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the starting trouble of a motor caused by the ripple of a power voltage, concerning drive for a brushless motor. SOLUTION: This drive is provided with comparators 36-40, which compares counter electromotive forces Vu , Vv , and Vw generated in stator coils 16-20 with a reference voltage, as a circuit for detecting the rotational position of a rotor 41 constituting the brushless motor 10. The reference voltage VCOM is set so that the potential difference ΔV from the power voltage VCC becomes the value geared to the magnitude of the power voltage VCC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device, and more particularly, to controlling the timing of energizing each of a plurality of armature windings constituting a stator. The present invention relates to a brushless motor driving device using a result of comparison between a generated back electromotive force and a predetermined reference voltage.

[0002]

2. Description of the Related Art A brushless motor driving apparatus has been known which controls a motor having a rotor having a magnet and a stator having a plurality of stator coils by using a back electromotive force.

FIG. 3 is a configuration diagram showing an example of a driving device of a conventional brushless motor 10. As shown in FIG. Brushless motor 1
0 includes a rotor 14 having a magnet and a stator 22 having three-phase stator coils 16, 18, 20. One end of each of the stator coils 16, 18, 20 is connected to the power supply terminal 24 (power supply voltage VCC), and the other end is connected to the switching elements 26, 28, 30. Each of the switching elements 26 to 30 is connected to the timing circuit 32, and is selectively turned on according to a command from the timing circuit 32. When the switching elements 26 to 30 are turned on, a current flows through the stator coils 16 to 20 corresponding to the switching elements to be in an energized state. At this time, the rotor 14 and the stator 2
The brushless motor 10 is driven to rotate by the generation of an electromagnetic force between them and the torque that rotates the rotor 14.

The timing circuit 32 includes a comparator 3
6 to 40 outputs are connected. Comparator 36 ~
40 non-inverting input terminals are respectively connected to the stator coil 1
6 to 20 and switching elements 26 to 30. The stator coils 16 to 20 generate back electromotive force by switching between energization and non-energization. For this reason, the comparators 36 to 40 include the stator coils 16 to 20.
Motor output voltages V _U , V _V ,
V _W is input. The inverting input terminals of the comparators 36 to 40 are connected to a resistor 4 having one end connected to the power supply terminal 24.
2 is connected to the other end. The other end of the resistor 42 is connected to a constant current source 44 (current value: I _CONST ) via the transistor Q1. Hereinafter, the other end of the resistor 42 is referred to as “reference terminal 4”.
6 ". The comparators 36 to 40 are connected to a reference terminal 46.
Are compared with the motor output voltages V _U , V _V , V _W as the reference voltage VCOM. The timing circuit 32
The rotational position of the rotor 14 is detected based on the result of comparison by each of the comparators 36 to 40. Then, the timing of energizing each of the stator coils 16 to 20 is determined, and the switching elements 26 to 30 are on / off controlled.

[0005]

The back electromotive force generated in the stator coils 16 to 20 changes according to the magnitude of the power supply voltage VCC. Specifically, the back electromotive force has a relatively large peak value based on the power supply voltage VCC when the power supply voltage VCC is large, and has a relatively small peak value when the power supply voltage VCC is small.

However, in the above-described conventional driving device, the reference voltage VCOM of the comparators 36 to 40 to which the back electromotive force is input has the one end connected to the power supply terminal 24 and the other end connected to the resistor 42 connected to the constant current source 44. The voltage at the other end. In such a configuration, the resistance 4
Since the current I _R flowing through the two constant potential difference between the reference voltage VCOM and the power supply voltage VCC of the comparator 36 to 40 during startup is always maintained constant.

For this reason, in the above-mentioned conventional driving device, the stator coils 16 to 20 are caused by the fluctuation of the power supply voltage VCC.
Even when the peak value of the back electromotive force generated in the comparator 3 is large or small, the comparator 3
Since the reference voltages VCOM of 6 to 40 are maintained at a constant potential difference with respect to the power supply voltage VCC regardless of the magnitude of the power supply voltage VCC, the counter electromotive force generated in the stator coils 16 to 20 is input to the comparators 36 to 40. Even so, a situation may occur in which the comparators 36 to 40 cannot output a signal indicating the specific position of the rotor 14 at an appropriate time. When such a situation occurs, the rotational position of the rotor 14 cannot be properly detected, so that each stator coil 1
6-20 cannot be energized at the right time,
The brushless motor 10 cannot be rotated properly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a brushless motor driving device capable of avoiding a motor starting failure caused by a fluctuation in power supply voltage. .

[0009]

According to a first aspect of the present invention, a back electromotive force generated in each of a plurality of armature windings (16, 18, 20) constituting a stator (22) and a predetermined reference voltage are set. Comparison means for comparing with a voltage (36, 38, 40)
A driving device for the brushless motor (10), which controls the timing of energizing each armature winding (16, 18, 20) based on the comparison result by the comparing means (36, 38, 40). And a reference voltage changing means (60) for setting the predetermined reference voltage such that a potential difference between the reference voltage and the power supply voltage changes according to the magnitude of the power supply voltage.

According to a second aspect of the present invention, in the driving device for a brushless motor (10) according to the first aspect, the reference voltage changing means (60) sets the predetermined reference voltage to a value higher than the power supply voltage. In a brushless motor driving apparatus, the potential difference from the power supply voltage is set to be large, and if the power supply voltage is small, the potential difference from the power supply voltage is set to be small.

According to a third aspect of the present invention, in the brushless motor driving device according to the first or second aspect, the reference voltage changing means (60) is connected to a power supply terminal (24) where the power supply voltage appears. A brushless motor driving device, wherein the predetermined reference voltage is changed by changing the magnitude of a current flowing toward a reference terminal (46) at which the predetermined reference voltage appears.

In the present invention, the comparing means (36, 38,
40) is a predetermined reference voltage and a multi-phase armature winding (1).
6, 18, 20) are compared with the back electromotive force generated respectively. The predetermined reference voltage is set such that the potential difference from the power supply voltage changes according to the magnitude of the power supply voltage. Therefore, even when the peak value of the back electromotive force changes due to the fluctuation of the power supply voltage, the reference voltage is changed according to the magnitude of the power supply voltage, so that the rotational position of the brushless motor (10) is changed. It can be detected properly. Therefore, according to the present invention, the energization to the armature windings (16, 18, 20) can be switched at an appropriate timing, so that the start-up failure of the brushless motor (10) due to the fluctuation of the power supply voltage can be prevented. Can be avoided.

Note that the reference numerals in the parentheses are provided for easy understanding, are merely examples, and are not limited to the illustrated embodiment.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a driving device for a brushless motor 10 according to one embodiment of the present invention. still,
1, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, in the driving device of the brushless motor 10 according to the present embodiment, the other end of the resistor 42 having one end connected to the power supply terminal 24 is connected to the collector of the transistor Q1. The emitter of the transistor Q1 is connected to the emitter of the transistor Q2 whose collector is connected to the power supply terminal 24. The transistors Q1 and Q2 form a differential circuit. The emitter of a transistor Q3 whose collector and base are connected to the power supply terminal 24 is connected to the base of the transistor Q1.

Transistors Q4 and Q4 each having a collector connected to the power supply terminal 24 are provided at the base of the transistor Q2.
The emitters of Q5 and Q6 are connected. The base of the transistor Q4 is connected to the W-phase terminal via the resistor R1, and is connected to the collector of the transistor Q9 whose emitter is grounded. The base of the transistor Q5 is connected to a V-phase terminal via a resistor R2.
The emitter is connected to the grounded collector of transistor Q10. The base of the transistor Q6 is connected to the U-phase terminal via the resistor R3, and is connected to the collector of the transistor Q11 whose emitter is grounded.

The bases of the transistors Q9, Q10 and Q11 are connected to the comparator 50 via resistors R4, R5 and R6.
Connected to the output. The reference terminal 46 is connected to the non-inverting input terminal of the comparator 50, and the reference voltage V
COM is input. On the other hand, an oscillator 52 is connected to the inverting input terminal of the comparator 50, and a triangular wave having a constant period is input. The comparator 50 outputs the reference voltage V
A low signal or a high signal is output according to the comparison result between COM and the triangular wave.

The power supply terminal 24 is connected via a resistor 60 to the collector of a transistor Q7 whose emitter is grounded. The collector of the transistor Q7 is connected to the base. The base of the transistor Q7 is connected to the base of the transistor Q8 whose emitter is grounded. The collector of the transistor Q8 is connected to the emitters of the transistors Q1 and Q2.

In the above circuit configuration, when a current I _R flows from the power supply terminal 24 to the reference terminal 46 via the resistor 42, the reference voltage VCOM of the comparators 36 to 40 becomes a voltage shown by the following equation (1).

[0020] _{VCOM = VCC - I R · R} EXT ··· (1) In this case, the motor comparators 36-40, which includes a take reference voltage VCOM, the counter electromotive force generated in the stator coils 16 to 20 The output voltages V _U , V _V , and V _W are compared, and a signal corresponding to the comparison result is output to the timing circuit 32. The timing circuit 32 includes comparators 36 to
40, the rotational position of the rotor 14 is detected based on the output signal, and each of the stator coils 16 to 2 corresponding to the rotational position is detected.
Switching element 26 in accordance with the energization timing to zero.
30 are selectively turned on and off.

FIG. 2 shows a brushless motor 10 according to this embodiment.
FIG. 5 is a diagram for explaining the operation of the drive device at the time of startup. FIG. 2A shows a U-phase terminal when the power supply voltage VCC is relatively large (power supply voltage = VCC1).
The waveforms of the motor output voltages V _U , V _V , and V _W appearing at one of the V-phase terminal and the W-phase terminal (these are generally referred to as V *) are shown. FIG. 2B shows a case where the power supply voltage VCC is relatively small (power supply voltage = VCC2).
> VCC1), the waveform of the motor output voltage V * appearing at any one of the U-phase terminal, the V-phase terminal, and the W-phase terminal is shown. In FIGS. 2A and 2B, U
The motor output voltage V * appearing at any one of the phase terminal, the V-phase terminal, and the W-phase terminal is indicated by a solid line, and the signal (reference voltage VCOM) input to the inverting input terminal is indicated by a broken line.

In the circuit configuration of this embodiment, FIG.
As shown in FIG. 7, when the power supply voltage VCC is relatively large, the peak value of the back electromotive force generated in the stator coils 16 to 20 becomes relatively large according to the magnitude of the power supply voltage VCC. , And the peak value of the motor output voltage V * appearing at the W-phase terminal also increases. At this time, the reference voltage VCOM at the reference terminal 46 is set such that the potential difference ΔV is somewhat larger than the power supply voltage VCC (VCOM = VCOM1, ΔV = Δ
V1).

On the other hand, as shown in FIG.
When CC is relatively small, the peak value of the back electromotive force becomes a small value according to the magnitude of the power supply voltage VCC.
The peak values of the motor output voltage V * appearing at the phase terminal, the V-phase terminal, and the W-phase terminal are also reduced. In the circuit configuration of the present embodiment, when the power supply voltage VCC decreases, the power supply terminal 24
The magnitude of the current I ₁ flowing from the resistor 60 decreases, also decreases the current flowing into the collector of the transistor Q8. In this case, the current flowing into the collector of transistor Q1, i.e., current I _R flowing through the resistor 42 also be smaller, the voltage drop across the resistor 42 (= I _R ·
R _EXT ) is smaller than when the power supply voltage VCC is large. Therefore, in this embodiment, when the power supply voltage VCC is low, the reference voltage VCOM at the reference terminal 46 is
Is equal to the power supply voltage VC as compared with the case where the power supply voltage VCC is large.
The potential difference ΔV from C is set to be small (VCOM = VCOM2, ΔV = ΔV2).

As described above, according to the circuit configuration of this embodiment, the reference voltage VCOM is set to the potential difference Δ from the power supply voltage VCC.
V can be set to a value corresponding to the magnitude of the power supply voltage VCC. That is, even if the peak value of the back electromotive force generated in stator coils 16 to 20 fluctuates due to the fluctuation of power supply voltage VCC, reference voltage VCOM according to the magnitude of power supply voltage VCC can be set.

For this reason, in the present embodiment, even when the peak value of the back electromotive force fluctuates due to the fluctuation of the power supply voltage VCC, the comparators 36 to 40 operate at the timing according to the peak time. Signals indicating fourteen specific positions can be output. At this time, the timing circuit 3
2 makes it possible to appropriately detect the rotational position of the rotor 14. Therefore, according to the driving device for the brushless motor 10 of the present embodiment, the energization of each of the stator coils 16 to 20 can be switched at an appropriate timing.
Brushless motor 10 due to fluctuation of power supply voltage VCC
Does not cause oscillation start-up or start-up failure, and the brushless motor 10 can be appropriately rotated and driven.

In the above-described embodiment, the present invention is applied to the three-phase brushless motor 10 having three stator coils 16 to 20, but the present invention is not limited to this. Can be applied to the brushless motor.

As described above, according to the first to third aspects of the present invention, even when the power supply voltage fluctuates, the current is applied to each armature winding using the back electromotive force generated in each armature winding. Since the switching can be performed at an appropriate timing, it is possible to avoid a failure in starting the motor due to the fluctuation of the power supply voltage.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a driving device for a brushless motor according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the brushless motor driving device according to the embodiment at the time of startup.

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

[Explanation of symbols]

10 brushless motor 16-20 stator coil 22 stator 24 power terminals 26 to 30 the switching element 32 the timing circuit 36 to 40 comparators VCC supply voltage VCOM reference voltage _{V U,} V V, V _W back EMF

Claims (3)

[Claims] 1. A comparison device for comparing a back electromotive force generated in each of a plurality of phase armature windings constituting a stator with a predetermined reference voltage, wherein each armature winding is based on a comparison result by the comparison device. A drive device for a brushless motor that controls a timing of energizing the power supply, wherein reference voltage changing means is provided for setting the predetermined reference voltage so that a potential difference from the power supply voltage changes according to the magnitude of the power supply voltage. And a brushless motor driving device. 2. The brushless motor driving device according to claim 1, wherein the reference voltage changing unit sets the predetermined reference voltage such that a potential difference from the power supply voltage increases when the power supply voltage is high. A brushless motor driving device characterized in that when the power supply voltage is low, the potential difference from the power supply voltage is set to be small. 3. The drive device for a brushless motor according to claim 1, wherein the reference voltage changing unit detects a current flowing from a power supply terminal where the power supply voltage appears to a reference terminal where the predetermined reference voltage appears. A driving device for a brushless motor, wherein the predetermined reference voltage is changed by changing a magnitude.