JP2822618B2 - Speed control device for brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a brushless motor used in consumer appliances and home electric appliances.

2. Description of the Related Art In recent years, a brushless motor has often been used for various types of motors in order to extend their life, increase reliability, or reduce the shape of the motor.

In particular, brushless fan motors used in consumer appliances and home appliances require variable speed control over a very wide range of motor rotation speed in order to adjust the air flow.

In addition, pulse width modulation (hereinafter referred to as PWM) control of the motor has become an indispensable condition as the output of equipment increases.

FIG. 4 shows a conventional example of such a brushless motor speed controller. Hereinafter, a conventional brushless motor speed control device will be described with reference to the drawings.

FIG. 4 is a circuit diagram of a conventional brushless motor speed controller. In FIG. 4, one ends of motor drive coils 101a, 101b, 101c are commonly connected, and the other ends of the drive coils 101a, 101b, 101c are connected to an output terminal of a power circuit 110. The position detection circuit 102 outputs a position detection signal of the mover, and its output terminal is an energization state command circuit 103.
Is connected to the input terminal. The energization state instruction circuit 103 outputs an energization state instruction signal and a speed detection signal, an output terminal of the energization state instruction signal is connected to an input terminal of the energization switching circuit 104, and an output terminal of the speed detection signal is connected to the speed control circuit 105. Connected to input terminal. The energization switching circuit 104 outputs an energization switching signal, and its output terminal is input to the power circuit 110 and sequentially energizes the drive coils 101a, 101b, 101c to rotate the motor. The speed command circuit 106 outputs a speed command signal, and an output terminal thereof is connected to an input terminal of the speed control circuit 105 together with a speed detection signal of the energization state command circuit 103. The speed control circuit 105 outputs a speed control signal,
Smoothed by the filter circuit 107, the output terminal of which is PWM
Connected to the non-inverting input terminal of the circuit 109. Oscillator (OSC)
108 outputs a triangular wave signal, the output terminal of which is the PWM circuit
Connected to 109 inverting input terminal. The PWM circuit 109 outputs a PNM signal which is a pulse signal having a duty,
Its output terminal is connected to the input terminal of the energization switching circuit 104.

The operation of the conventional brushless motor driving device configured as described above will be described below.

FIG. 5 shows an operation signal waveform diagram in FIG. Fifth
In the figure, V _A1 , A _B1 , and V _C1 are the position detection signal waveforms of the mover output from the position detection circuit 102. The position detection signal is logically processed by the conduction state command circuit 103 as follows to obtain conduction state command signals UH ₀₁ , VH ₀₁ , WH ₀₁ , UL ₀₁ , VL ₀₁ , WL ₀₁ .

UH ₀₁ : Logical product of V _A1 and _B1 VH ₀₁ : Logical product of V _B1 and _C1 WH ₀₁ : Logical product of V _C1 and _A1 UL ₀₁ : Logical product of V _B1 and _A1 VL ₀₁ : Logical product of V _C1 and _B1 WL _01: V _d1 in logical fifth diagram of V _A1 and _C1 has a pulse signal having a duty is a PWM signal output from the PWM circuit 109.

The PWM signal _Vd1 is logically processed by the energization switching circuit 104 as follows to obtain energization switching signals UH ₁ , VH ₁ , WH ₁ , UL ₁ , VL ₁ , WL ₁ .

UH ₁ : UH ₀₁ VH ₁ : VH ₀₁ WH ₁ : WH ₀₁ UL ₁ : Logical product of UL ₀₁ and V _d1 VL ₁ : Logical product of VL ₀₁ and V _d1 WL ₁ : Logical product of WL ₀₁ and V _d1 The exchange signal is a signal in which the PWM signal _Vd1 output from the PWM circuit 109 is superimposed on the output of the conduction state command circuit 103. These energization switching signals are
The current is input to the drive coil 110 to sequentially energize the drive coils 101a, 101b, and 101c. For example, when UH ₁ and VL ₁ are H
Current flows from 1a to energizing the coil 101b, when UH ₁ and WL ₁ is H current flows from the drive coils 101a to the drive coil 101c.
In this way, the energized state of the drive coil is switched one after another, and the motor is driven.

Next, a description will be given of the case where the motor is _{variably driven} by the PWM signal _Vd1 .

In FIG. 4, F _ref1 is a speed command signal.

Further, FG ₁ is a speed detection signal of the motor, it can be obtained by logically processing the position detection signal as follows.

FG ₁ : (V _A1 · V _B1 · _C1 ) + (V _A1 · _B1 · V _C1 ) + ( _A1 · V _B1 · V _C1 ) where · represents a logical product and + represents a logical sum.

As the motor speed increases, the frequency of FG ₁ increases.
First, consider the case where the relationship between the frequency F _FG1 and the frequency f _Fref1 of the measurement command signal F _ref1 is f _FG1 > f _Fref1 .

In this case it operates to the potential of the output V ₁ of the filter circuit 107 outputs the smoothed speed control circuit 105 decreases, so that the duty of the PWM signal V _d1 output from the PWM circuit 109 is reduced, to the drive coil It operates to reduce the amount of power supply.

 Therefore, the motor decelerates.

Conversely, decreases the speed of the motor, the frequency of the FG ₁ is lowered, the relationship between the f _GF1 and f _fREF1 is, consider a case where a f _FG1 <f _Fref1.

In this case it operates to the potential of the output V ₁ of the filter circuit 107 outputs the smoothed speed control circuit 105 increases, so that the duty of the PWM signal V _d1 output from the PWM circuit 109 is increased, to the drive coil It operates to increase the amount of power supply.

 Therefore, the motor accelerates.

After all, the speed of the motor, so that the frequency of the speed detection signal FG ₁ is controlled to match the frequency of the speed command signal F _ref1.

Figure 6 is one in which the speed control of the motor showing a state of the output V ₁ and the PWM signal V _d1 of the filter circuit 107 when being performed stably. As shown in FIG.
Output V ₁ of the 7 is generally not a complete direct current signal, a signal having a ripple of the same frequency component of the FG ₁ is a speed detection signal of the motor and the fundamental wave.

The PWM signal V _d1 is a triangular wave signal output V of the oscillator (OSC) 108
The _OSC1 and the output V ₁ are those obtained by comparing the PWM circuit 109, as shown in FIG. 6, and has a pulse signal of varying duty depending on the value of V _1.

Feeding amount to the drive coil is determined according to the duty of the PWM signal V _d1, this conventional example, when the Low period of the duty of V _d1 increases, the operation as the power supply amount to the driving coil is reduced Do.

Problems to be Solved by the Invention However, in the above-described configuration, when the motor is controlled at a relatively low speed, the following problems occur. That is, when controlling the motor at a low speed, the amount of power supply to the motor is not so necessary. Therefore V ₁ is V _OSC1
, The duty of the PWM signal V _d1 is changed in a direction to decrease the amount of power supply to the drive coil (in a direction to increase the low period of V _d1 ).

However, as V ₁ was described above, the FG ₁ and the same frequency component is a speed detection signal of the motor has a ripple with a fundamental wave and V ₁ is closer to the lower limit of V _OSC1, in FIG. 7 as shown, the ripple voltage of V ₁ is period is generated below the lower limit of V _OSC1. Ripple voltage V ₁ is below the lower limit of V _OSC1, this period PWM signal V _d1 is no longer a pulse signal having a duty, V _d1 is fixed to Low level,
Power supply to the drive coil is stopped.

Such a period during which the ripple voltage of V ₁ is below the lower limit of V _OSC1, power supply to the driving coil is stopped, V _OCS1
Relatively long, repeatedly generated with a period of the ripple voltage V ₁ with respect to the oscillation frequency (typically a carrier frequency as referred in PWM control). That, or feeding is performed to the drive coil in a period of the ripple voltage of V _1, the feed is or is stopped. Such a state will be referred to as an intermittent operation state. In the intermittent operation state, the motor generates vibrations and uneven rotation, and when the repetition period of the intermittent operation state becomes an audible range, it causes noise.

As described above, the conventional brushless motor speed control device has various problems.

Means for Solving the Problems In order to solve the conventional problems, a speed control device for a brushless motor according to the present invention includes an energization state instruction unit that outputs an instruction signal for sequentially switching energization states of a plurality of phases of drive coils,
A speed detecting means for detecting a speed, a speed commanding means, and a pulse width modulation signal for controlling an amount of power supplied to the drive coil by a duty of a pulse signal, which is superimposed on an output signal of the energization state commanding means Pulse width modulation means, minimum duty clamp means for limiting the duty of a pulse signal output from the pulse width modulation means, and a command signal of the energization state command means on which a pulse width modulation signal is superimposed by the pulse width modulation means And power means for amplifying the power and transmitting the amplified power to the drive coil.
The pulse width modulation means includes: a speed control means for outputting a speed control signal corresponding to a difference between a speed detection signal output from the speed detection means and a speed command signal output from the speed command means; An oscillator for outputting a carrier signal of the signal, and comparing means for comparing the carrier signal with the speed control signal, wherein the speed control signal is, for example, a period during which the speed control signal is lower than a predetermined value set by the minimum duty clamp means. Outputs a pulse signal having a duty determined by a result of comparison between the carrier signal and the speed control signal, while in a high period,
A pulse signal having the same cycle as the carrier signal and having a duty determined by a result of comparison between the carrier signal and a predetermined value set by the minimum duty clamp means is output.

Effect of the Invention With the above-described configuration, the present invention limits the minimum duty of a pulse signal when controlling the speed of the motor by varying the duty of the pulse signal output from the PWM circuit and adjusting the amount of power supplied to the motor. Since the speed control is performed so that the amount of power supplied to the motor drive coil does not fall below a predetermined level, it is possible to stably control the motor without intermittent operation even when performing speed control at a low speed. The speed of the motor can be controlled over a wide range from low speed to high speed.

Embodiment Hereinafter, a speed control device for a brushless motor according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a brushless motor speed controller according to an embodiment of the present invention. In FIG. 1, reference numerals 1a, 1b, and 1c denote motor drive coils. One ends of the driving coils 1a, 1b, 1c are connected to an output terminal of the power circuit 9, and the other ends are commonly connected. An output terminal of the position detection circuit 2 is connected to an input terminal of the conduction state instruction circuit 3, and an output terminal of the conduction state instruction circuit 3 is connected to an input terminal of the conduction state switching circuit 8. The output signal of the energization switching circuit 8 is power-amplified by the power circuit 9 and
a, 1b, and 1c are sequentially energized to rotate the motor. The speed detection circuit 4 combines the signals output from the conduction state command circuit 3 and outputs a motor speed detection signal FG. The speed command circuit 5 outputs a motor speed command signal _Fref and is input to the PWM circuit 6 together with the motor speed detection signal FG.
The PWM circuit 6 includes a speed control circuit 20 to which the output of the speed detection circuit 4 and the output of the speed command circuit 5 are input.
, An OSC 21, and a PWM comparator 22 to which the output of the speed control circuit 20 and the output of the OSC 21 are respectively input, and transmits a pulse signal having a duty to the energization switching circuit 8. Reference numeral 7 denotes a minimum duty clamp circuit 7, which is connected to a PWM comparator 22, which is a component of the PWM circuit 6.

The operation of the speed controller for a brushless motor according to the embodiment of the present invention configured as described above will be described below.

FIG. 2 is an operation signal waveform diagram in FIG. Second
In the figure, VA, VB and VC are the position detection signal waveforms of the mover output from the position detection circuit 2. Position detection signals VA, VB,
VC is logically processed by the conduction state command circuit 3 as follows to obtain conduction state command signals UH0, VH0, WH0, UL0, VL0, WL0.

UH ₀ : V Logical product of _A and _B VH ₀ : Logical product of V _B and _C WH ₀ : Logical product of V _C and _A UL ₀ : Logical product of V _B and _A VL ₀ : Logical product of V _C and _B WL ₀ : Logical product of V _A and _{C In} FIG. 2, V _d is a PWM signal output from the PWM circuit 6 and is a pulse signal having a duty. PW
The M signal _Vd is logically processed as follows, and the energization switching signals UH, V
Obtain H, WH, UL, VL, WL.

UH: UH ₀ VH: VH ₀ WHWH ₀ UL: Logical product of UL ₀ and V _d VL: Logical product of V ₀ and V _d WL: Logical product of WL ₀ and V _d the output of the circuit 3 is a signal obtained by superimposing a PWM signal V _d output from the PWM circuit 6.

These energization switching signals are input to the power circuit 9 to sequentially energize the drive coils 1a, 1b, 1c. For example, UH and VL are H
When current is flowing from the driving coil 1a to the driving coil 1b, when UH and WL are H, the driving coil 1a
Current flows to 1c. In this way, the energized state of the drive coil is switched one after another, and the motor is driven.

Then the PWM signal V _d, is described that the motor is variable speed. In FIG. 2, FG is a motor speed detection signal, which can be obtained by performing the following logical processing on the position detection signals VA, VB, VC.

FG: (V _A V _{B C} ) + (V _{A B} V _C ) + ( _A V _B V _C ) where represents a logical product and + represents a logical sum.

As the speed of the motor increases, the frequency of FG increases. First, consider the case where the relationship between the frequency f _FG and the frequency f _Fref of the speed command signal F _reF is f _FG > f _Fref .

At this time, the potential of the output signal V of the speed control circuit 20 increases, reducing the duty of the PWM signal V _d output from the PWM comparator 22, operates to reduce the amount of power supplied to the driving coil. As a result, the motor decelerates.

Conversely, consider the case where the motor speed decreases, the frequency of FG decreases, and the relationship between f _FG and f _{Fref1 satisfies} f _FG <f _Fref .

At this time, the potential of the output signal V of the speed control circuit 20 decreases, increasing the duty of the PWM signal V _d output from the PWM comparator 22, it operates to increase the power supply amount to the drive coil. As a result, the motor accelerates.

Eventually, the speed of the motor is controlled so that the frequency of the speed detection signal FG matches the frequency of the speed command signal _Fref .

Next, the PWM circuit 6 and the minimum duty clamp circuit 7
Will be described in detail.

FIG. 3 is an operation signal waveform diagram of the PWM circuit and the minimum duty clamp circuit in FIG. In FIG. 3, V is an output signal of the speed control circuit 20, and V _OSC is OSC21.
This is a triangular signal output from PWM comparator 22
Is a differential amplifier circuit composed of transistors 31 to 35, a constant current source 30, and a resistor 36. V and V _OSC are transistors 31 and 32
Is input to each of the bases. Assuming that currents flowing through the transistors 31 to ₃₄ are I _{31 to} I ₃₄ , respectively, when V> V _OSC , I ₃₁ <I ₃₂ unless the minimum duty clamp circuit 7 is added. The transistors 33 and 34 form a current mirror circuit, and I ₃₁ = I ₃₄ . Also, I ₃₁ = I
_33, so I ₃₂ > I ₃₄ .

At this time, the transistor 35 is turned ON, since they produce a voltage drop in the resistor 36, V _d becomes L.

And transistor 35 is OFF when the opposed V <V _OSC, V _d becomes H. The operation waveform at this time is shown in FIG. 3 assuming that V _d = V _d0 .

When V _d0 is H, power is supplied to the motor, and when V _d0 is L, power supply to the motor is stopped.

Next, the operation when the minimum duty clamp circuit 7 is added will be described. Minimum duty clamp circuit 7
Is composed of a transistor 40 and a reference voltage source 41 (output voltage V _L ). If the current flowing through the transistor 40 is I ₄₀ , then I ₃₃ = I ₃₁ + I ₄₀ .

When V> _VL , I ₃₁ ≪I ₄₀ , which can be approximated to I ₃₃ ≒ I ₄₀ . Accordingly, the duty of the output signal V _d of the PWM comparator 22 is determined by the reference voltage V _L.

I ₃₁ »I ₄₀ next when V <V _L, the duty of V _d so can be approximated by I ₃₃ ≒ I ₃₁ is determined by the output signal V of the speed control circuit 20. That is, the output of V _d becomes as shown in V _dC of FIG. 3, the period during which power supply is stopped to the motor for generating the low-speed control time as described in the prior art is no longer present, the intermittent operation of the motor Disappears.

As described above, according to the present embodiment, the provision of the minimum duty clamp circuit 7 prevents the motor from being in an intermittent operation state, and reduces the brushless motor without generating vibration, uneven rotation, noise, and the like. It is possible to perform variable speed control from speed to high speed.

Advantageous Effects of the Invention As is clear from the above description, the present invention adds a minimum duty clamp circuit to vary the duty of the pulse signal output from the PWM circuit to control the power supply to the motor. Since the minimum duty of the pulse signal is limited and the speed is controlled so that the amount of power supplied to the motor drive coil does not fall below a predetermined level, the power supply to the motor is stopped for a period longer than the cycle of the carrier frequency. This is particularly effective when it is not necessary to supply power to the motor at low-speed rotation command when the operation is not performed.The motor can be controlled at a variable speed from a low speed to a high speed over a wide range. Can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a brushless motor speed controller according to an embodiment of the present invention, FIG. 2 is an operation signal waveform diagram in FIG. 1, and FIG. 3 is a PWM circuit and a minimum duty clamp circuit in FIG. FIG. 4 is a circuit configuration diagram of a conventional brushless motor speed control device, FIG. 5 is an operation signal waveform diagram in FIG. 4, and FIG. 6 is an operation signal of a PWM circuit in FIG. FIG. 7 is a waveform diagram of an operation signal of the PWM circuit for the motor low speed command in FIG. 1a, 1b, 1c: drive coil, 3: energization state command means (energization state instruction circuit), 4: speed detection means (speed detection circuit), 5: speed instruction means (speed instruction circuit), 6 ... ... Pulse width modulation means (PWM circuit), 7 ... Minimum duty clamp means (Minimum duty clamp circuit), 9 ... Power means (power circuit), 20 ... Speed control means (Speed control circuit), 21 ... Oscillator (OSC), 22 …… Comparison means (PWM
comparator).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-46192 (JP, A) JP-A-60-51492 (JP, A) JP-A-3-11397 (JP, U) (58) Survey Field (Int.Cl. ⁶ , DB name) H02P ^6/ 00-6/24

Claims (1)

(57) [Claims] 1. A motor having a plurality of phases of driving coils, an energizing state instructing means for outputting a command signal for sequentially switching energizing states of the driving coils, a speed detecting means for detecting a motor speed, and a motor speed instructing means. And a pulse width modulation unit that outputs a pulse width modulation signal that controls the amount of power supplied to the drive coil by the duty of a pulse signal, and that is superimposed on an output signal of the energization state command unit. Minimum duty clamping means for limiting the duty of the output pulse signal; and power for amplifying the output signal of the conduction state command means on which the pulse width modulation signal is superimposed by the pulse width modulation means and transmitting the output signal to the drive coil. Means for controlling the speed of the brushless motor, wherein the pulse width modulation means is output from the speed detection means. A speed control unit that outputs a speed control signal corresponding to a difference between a degree detection signal and a speed command signal output from the speed command unit; an oscillator that outputs a carrier signal of a pulse width modulation signal; A speed control signal and a comparing means for comparing the speed control signal with the predetermined value set by the minimum duty clamp means.
A pulse signal having a duty determined by a comparison result between the carrier signal and the speed control signal is output, and the magnitude relationship between the speed control signal and a predetermined value set by the minimum duty clamp unit is opposite to the above state. In the period, a pulse signal having the same cycle as the carrier signal and having a duty determined by a comparison result between the carrier signal and a predetermined value set by the minimum duty clamp means is output. Speed control device for brushless motor.