JPH03256590A - Brushless motor drive unit - Google Patents

Abstract

PURPOSE:To obtain an easy-to-handle drive unit having simple circuitry by subjecting an AC commercial source voltage to smoothing and rectification and then applying directly onto the power supply terminal of a power circuit. CONSTITUTION:Position of a rotor is detected through a position sensor 2 and a position detecting circuit 3, and a conducting condition command circuit 4 turns the switch of a power circuit 9 ON, OFF through a conduction switching circuit 8 thus controlling the rotation. A PWM comparator 35 is controlled based on the difference between a speed detected through the speed detecting circuit 5 and an output from a speed command circuit 6, and a signal is provided to the conduction switching circuit 8 in order to control the rotational speed. Since the output from an AC power supply 10 is smoothed through a rectifying/smoothing circuit 11 and employed as the power supply for the power circuit 9, conventional switching power supply is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive device for a brushless motor.

2. Description of the Related Art Conventionally, AC motors have often been used as driving motors for home appliances and consumer appliances such as air conditioners and water heaters. Fan motors for air conditioners and water heaters require variable speed in order to adjust the air volume. However, although AC motors have the advantage of being very easy to use because they can be driven by being directly connected to a commercial AC power source, it has been difficult to vary their rotational speed. Therefore, in recent years, DC brushless motors, which can easily change the rotational speed, have been increasingly used in place of AC motors. An example of this is shown in FIG. FIG. 5 is a circuit diagram of a conventional brushless motor drive device.

A conventional brushless motor drive device will be described below with reference to FIG. The position detection circuit 106 receives the output signal from the position detection sensor 105 and outputs a rotor position detection signal. The energization switching circuit 107 outputs an energization switching signal for the drive coil of the motor based on the position detection signal.

The power of this energization switching signal is amplified by the power circuit 1ON, and the energization state of the drive coils is sequentially switched to drive the motor. The commercial power supply 102 is rectified and smoothed into a DC voltage by a rectification and smoothing circuit 103 to drive a switching power supply, and the switching power supply changes the DC voltage applied to the power circuit to vary the circuit speed of the motor.

Problems to be Solved by the Invention However, in the brushless motor drive device configured as shown above, a switching power supply is required to vary the rotational speed of the motor, and the switching power supply requires a coil, Since many elements such as capacitors and resistors are required, a large amount of mounting space is required when configuring the system, which makes it difficult to make the system lighter and simpler, and also causes high costs. .

In view of the above-mentioned problems, the present invention applies a constant DC voltage to the power supply terminal of a power circuit, thereby making it possible to vary the rotational speed of the motor without using a switching power supply, and to generate a speed command signal. The present invention provides an inexpensive and high-performance brushless motor drive device that can obtain a rotational speed proportional to the frequency or the ratio of its ON time and OFF time.

Means for Solving the Problems To achieve this object, a brushless motor drive device of the present invention includes a multi-phase drive coil of a motor and a position detection circuit that detects the rotational position of a rotor driven by the drive coil. an energization state command circuit that sequentially switches the energization state of the drive coil based on a device detection signal constituted by the position detection circuit; and a speed detection circuit that outputs a motor speed signal based on the position detection signal. Then, the ON period of the energization state command signal is chopped by the Canoa wave number so that the rotational speed of the motor is constant according to the speed command signal output from the speed command circuit of the motor and the speed command signal outputted from the speed command circuit. /OFF duty control PW
M circuit, a power circuit for inputting the output signal of the PWM circuit to the energization switching circuit of the drive coil and power amplifying the output signal, and means for applying a constant DC voltage to the power circuit. be.

Effect of the Invention With the above-described configuration, the present invention can rectify and smooth the AC power supply voltage into DC power supply voltage and directly apply it to the power supply terminal of the power circuit, and can change the frequency of the speed command signal or its ON time and OFF time without using a switching power supply. Good accuracy in proportion to the ratio (the motor rotation speed can be variably controlled).

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a brushless motor drive device according to an embodiment of the present invention.

Now, la, lb, and lc are drive coils, which are connected to the power circuit 9. The output signal of the position detection sensor 2 is input to the position detection circuit 3. The output signal of the position detection circuit 3 is input to the energization state command circuit 4 and also to the speed detection circuit 5. The output signal of the speed detection circuit 5 and the output signal of the speed command circuit 6 are input to a PWM circuit 13. The output signal of the energization state command circuit 4 is the P
The signal is input to the WM circuit 13. The output signal of the DC voltage applying means 12 and the output signal of the PWM circuit 13 are both input to the power circuit 9.

The specific circuit operation of the brushless motor drive device in one embodiment of the present invention configured as described above will be described below.

In FIG. 2, vAvBvc is the rotor position detection signal waveform. The position detection signal is logically processed by the energization state command circuit 4 as follows and becomes energization state command signals UHo and VHo.
, WHO, UL, VL, and WL are obtained.

UHO: Logical product of VA and vB VHo: Logical product of VB and VC WHO・Logic product of Vc and VA UL: Logical product of Va and Vx VL: Logical product of Vc and ■〒 Logical product of v^ and 〒However , V, V, and V are inverted signals of vAvBvc, respectively.

FIG. 2 is an operating signal waveform diagram in FIG. 1, and the energization state command signal is UHo in FIG. 2, respectively.

6° second like VHo, WHOo, UL, VL, WL
In the figure, Vd is the output signal of the duty control circuit 7, and as shown in FIG. 2, it is a <0N10FF signal. V
d is logically processed by the energization switching circuit 8 as follows, and becomes energization switching signals UH and VH.

Obtain WH, UL, VL, and WL.

UH: Logical product of UHo and Vd VH: Logical product of VHo and Vd WH: Logical product of WHo and Vd UL: UL VL: VL WL: WL These energization switching signals are applied to the input base of the drive transistor of the power circuit 9 be done. For example, UH and VL are H
When , current flows from the U-phase drive coil to the V-phase drive coil, and when UH and WL are H, current flows from the U-phase drive coil to the W-phase drive coil. In this way, the excitation state of the drive coils is switched one after another, and the motor rotates. Also,
By controlling the ON time of Vd, the current flowing through the drive coil can be controlled and the speed of the motor can be varied.

Next, the motor variable speed means will be explained.

FIG. 3 is an operation signal waveform diagram of the PWM circuit 13 in FIG. 1. Fref is a speed command signal.

The first D/A converter 31 converts Fref into an analog voltage signal Vref as follows. That is, F
When refJ<H, the capacitor is charged with a constant current, when F ref fJ<L, the voltage is held, and the moment F ref becomes H, it is rapidly discharged and then charged again with a constant current. Let's do it. In this way F ref
is converted to Frefl. The hold voltage of Fref 1 is output as an analog voltage signal Vref. That is, Vref changes according to the frequency of F ref,
When the frequency of F ref decreases, the potential of V ref decreases, and when the frequency of F ref decreases, the potential of V ref increases. Fsp is a motor speed detection signal, which can be obtained by logic processing a position detection signal as follows.

Fsp: (v^・VB-VC)+〈v^・VB-VC
)(VA·vB-vc> where * represents a logical product, and + represents a logical sum.

Fsp is converted into an analog voltage signal Vsp using the same method as Fref. Therefore, as the rotational speed of the motor increases, the frequency of Fsp increases and the potential of Vsp decreases. Conversely, when the rotational speed of the motor decreases, the frequency of Fsp decreases and the potential of Vsp increases. Now, when the motor rotation speed is low with respect to the speed command signal Fref, ysp
>Vref and the output VT)I of the speed error amplifier circuit 33
The potential of increases. The PWM comparator 35 compares VTH with the output Vo sc of the ONC 34 and outputs Vd. At this time, the ON time of Vd increases and the motor current increases, so the motor rotation speed increases, and V s p
= V r e f, that is, it is controlled so that Fsp = F ref. Further, when the rotational speed of the motor is higher than Fref, the ON time of Vd is reduced, the motor current is reduced, and the control is performed so that Fsp=Fref. In other words, the speed command signal allows variable speed control of the motor with ease and accuracy.

Next, the speed command signal and F/V converter will be described.

FIG. 4 is an operating signal waveform diagram of the second F/V converter in FIG. 1. This will be explained below with reference to FIGS. 1 and 4.

In FIG. 1, the duty control circuit 7 outputs a speed command signal F.
ref to speed command voltage Vref, speed detection signal Fsp to speed detection voltage Vsp, Vref=V
The rotational speed of the motor is controlled so that sp. Therefore, the rotational speed of the motor is uniquely determined for a certain frequency of Fref. In FIG. 4, Fref(A)
Fref(B) indicates a case where the frequency of the speed command signal is high, and Fref(B) indicates a case where the frequency is low. At this time, if the F/V conversion gain adjustment circuit 36 adjusts the F/V conversion gain, specifically the value of the constant current that charges the capacitor,
ref(A>≠Fref(B) and Vref(A
)−Vref(B). That is, the same motor rotation speed can be set for different frequencies. In other words, F re in any frequency band
It is possible to deal with f.

Also, as shown in Fref (C) in Fig. 4, the O of Fref is
Since Vref changes also when the N/○FF ratio changes, it is possible to cope with the case where the speed command signal is given at the 0N10FF ratio. Also, Fref
Since it is a digital signal, it is possible to exchange signals using elements such as photocoupler, and it isolates the motor control system from the motor drive system and prevents noise generated from the motor drive system from having an adverse effect on the motor control system. It is possible to prevent this from occurring.

Effects of the Invention As is clear from the above explanation, the present invention rectifies and smoothes the AC voltage of the commercial power supply voltage and applies it directly to the power supply terminal of the power circuit, so it is very easy to use and easy to use just like an AC motor. Since the speed of the motor can be varied according to the speed command signal without using a power supply, the coils, capacitors, resistors, etc. that were required to configure a conventional switching power supply are no longer required, making the motor drive system light and simple. It is possible to reduce the cost of parts significantly. In addition, since the motor rotation speed can be varied in proportion to the frequency of the speed command signal or the ratio of its ON time and OFF time, it has very high precision (it is possible to variably control the rotation speed over a wide range. /
By adjusting the V conversion gain, it is possible to correspond to speed command signals of all frequency ranges and 0N10FF ratios.

Furthermore, since the speed command signal can be insulated by a photocoupler or the like, it is possible to provide an excellent brushless motor drive device in which the motor drive system does not adversely affect the motor control system that generates the speed command signal. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a brushless motor drive device according to an embodiment of the present invention, FIG. 2 is an operating signal waveform diagram in FIG. 1, and FIG. 3 is an operating signal waveform diagram of the PWM circuit in FIG. FIG. 4 is an operating signal waveform diagram of the second F/V converter in FIG. 1. FIG. 5 is a circuit diagram of a conventional brushless motor drive device. 1, a, lb, lc...drive coil, 2...
...Position detection sensor, 3...Position detection circuit,
4... Energization state command circuit, 5... Speed detection circuit, 6... Speed command circuit, 7...
・Duty control circuit, 8... Energization switching circuit,
9... Power circuit, 10... AC power supply voltage, 11... Rectifier smoothing circuit, 12...
・DC voltage application means. Figure 2 L Ward〉〉〉

Claims (3)

[Claims] (1) A plural-phase drive coil of the motor, a position detection circuit that detects the rotational position of the rotor driven by the drive coil, and a position detection circuit that detects the rotational position of the rotor driven by the drive coil, and a An energization state command circuit that sequentially switches the energization state, a speed detection circuit that outputs a motor speed signal based on the position detection signal, a motor speed command circuit, and a speed command signal output from the speed command circuit. A PWM circuit that controls the ON/OFF duty by chopping the ON period of the energization state command signal at a carrier frequency so that the rotational speed of the motor is kept constant according to the frequency, and the output signal of the PWM circuit is used to energize the drive coil. 1. A brushless motor drive device comprising: a power circuit that inputs to a switching circuit and amplifies the power of an output signal thereof; and means for applying a constant DC voltage to the power circuit. (2) The brushless motor drive device according to claim 1, wherein a voltage obtained by rectifying and smoothing a commercial power source is directly applied to the power circuit. (3) The duty control circuit that controls the duty includes a first F/V converter that converts the motor speed signal into an analog voltage proportional to its frequency, and a speed command signal that converts the speed signal into an analog voltage proportional to its frequency or its ON time and OFF time. a second F/V converter that converts into an analog voltage proportional to the ratio; an F/V conversion gain adjustment circuit that adjusts the conversion gain of the second F/V converter; and an F/V conversion gain adjustment circuit that adjusts the conversion gain of the second F/V converter; a speed error amplification circuit that amplifies the error between the output signal and the output signal of the second F/V converter; an oscillation circuit (hereinafter referred to as OSC) that oscillates at a constant frequency; and an output voltage of the speed error amplification circuit and the The brushless motor according to claim 1 or 2, comprising a PWM comparator that compares the output voltage of the OSC and controls the rotational speed of the motor to be proportional to the frequency of the speed command signal or the ratio of its ON time and OFF time. drive unit.