JPH0993979A - Controller of brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize simplification and cost reduction of the position detecting circuit of a rotor by switching the current application of a brushless motor, based on the output position detection signal from a position detecting means. SOLUTION: The specified voltage generating circuit 11d of a position detecting circuit 11 divides the DC voltage from a DC power source 8 with resistors R3 and R4, and generates positive specified voltage Va, and stabilizes it with an operational amplifier, and outputs it to a comparison circuit 11e. Moreover, a level shift circuit 11c shifts the neutral-point voltage inputted into a terminal a by specified voltage, and outputs it into the comparison circuit 11e through the terminal b. And, when the neutral-point voltage is inputted into the non-reversal input terminal of the operational amplifier constituting the comparison circuit 11e and the specified voltage Ve is inputted into the non-reversal input terminal, the comparison circuit 11 compares the neutral-point voltage with the specified voltage Va, and outputs the comparison result, and a signal, which changes at the intersecting point between the neutral-point voltage and the specified voltage Va, is inputted into a control circuit 10, and the position detection of the rotor is judged. As a result, one system of position detecting circuit will do, and the simplification and cost down can be made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technique for a sensorless DC brushless motor (hereinafter referred to as a brushless motor), and more particularly, to a brushless motor control device that realizes simplification of a rotor position detection circuit and cost reduction. It is about.

[0002]

2. Description of the Related Art In this type of brushless motor,
The position of the brushless motor rotor is detected, and the energization of the armature winding of the brushless motor is switched based on this position detection, while the energization voltage of the armature winding is used to control the rotation speed of the brushless motor, for example. The duty cycle of the PWM signal (chopping signal) that chops (applied voltage) is varied.

Therefore, as shown in FIG. 5, in the brushless motor control device, the commercial power source 1 is connected to the AC / DC converting section 2.
Is converted into DC, and the converted DC power is switched by the inverter unit 3 and supplied to the brushless motor 4 as three-phase AC.

Further, the terminal voltages of the armature windings U, V, W of the brushless motor 4 are converted into analog position detecting circuits 5.
This position detection circuit 5 differentiates at least those terminal voltages and then integrates them, compares the integrated signals (90 degree phase delayed signals) with the neutral point potential, and outputs the signals of these comparison results. (Signal changing at intersection) is output to the control circuit 6 as a position detection signal. Since the position detection circuit 5 is already known, a detailed description will be omitted.

The control circuit 6 controls the rotation of the rotor of the brushless motor 4 by switching elements (transistors) of the inverter unit 3 based on the position detection signal.
A signal for driving Ua, Va, Wa, X, Y, Z is output to the drive circuit 7, and a chopping signal is output to the drive circuit 7 for chopping the drive period.

At this time, the DC power source 8 outputs a drive power source for driving each Ua, Va, Wa, X, Y, Z of the inverter unit 3 to the drive circuit 7. Although not shown, the power source for the drive is the inverter unit 3 via the drive circuit
Is supplied to.

Then, the ON time of the duty cycle of the chopping signal is lengthened to increase the rotation speed of the brushless motor 4, and the ON time of the duty cycle is shortened to decrease the rotation speed of the brushless motor 4. By varying the ON time of the duty cycle in this manner, the rotation speed of the brushless motor 4 can be set to the target rotation speed.

[0008]

However, the position detection circuit of the controller for the brushless motor requires a differentiating circuit, an integrating circuit, a comparing circuit, and the like, and in the case of a three-phase motor, these circuits require three systems. Therefore, there is a problem that the circuit is complicated and the cost becomes high.

The present invention has been made in view of the above problems, and an object thereof is to provide a controller for a brushless motor, which can simplify a rotor position detection circuit and reduce costs. is there.

[0010]

To achieve the above object, the present invention applies at least a direct current power source to a brushless motor by switching it with a plurality of switching means of an inverter means, and at the same time, a rotor of the brushless motor. In the controller of the brushless motor that detects the position and controls the rotation of the brushless motor by switching the energization of the brushless motor based on the position detection of the rotor, the direct current component of the neutral point voltage of the brushless motor is determined. The position detection means for removing the neutral point voltage, level-shifting the neutral point voltage to a predetermined level, comparing the level-shifted neutral point voltage with a predetermined voltage, and outputting the comparison result as a position detection signal. It is characterized in that energization of the brushless motor is switched based on an output position detection signal from the means.

The position detecting means applies a terminal voltage of the armature winding of the brushless motor and divides the voltage to artificially obtain a neutral point voltage of the brushless motor, and a DC circuit of the neutral point voltage. A capacitor for removing a component, a predetermined voltage generating circuit for generating a predetermined voltage, a level shift circuit for predetermined shifting of the neutral point voltage from which the direct current component has been removed, the shifted neutral point voltage and the predetermined voltage. And a comparison circuit for comparing the two, and the energization of the brushless motor may be switched by an output signal of the comparison circuit.

Further, the brushless motor has a lead-out terminal for a neutral point voltage of the brushless motor, and the position detecting means has a voltage dividing circuit for obtaining a neutral point voltage from the lead-out terminal, and the neutral point. A capacitor for removing the direct current component of the point voltage, a predetermined voltage generating circuit for generating a predetermined voltage, a level shift circuit for predetermined shifting of the neutral point voltage from which the direct current component has been removed, and the shifted neutral point voltage A comparison circuit for comparing with the predetermined voltage may be provided, and energization of the brushless motor may be switched by an output signal of the comparison circuit.

In this case, it is preferable that the predetermined voltage for shifting the neutral point voltage is a positive voltage. Further, it is preferable that the predetermined voltage generation circuit divides the power supply for driving the switching element of the inverter means to generate a predetermined voltage.

In the level shift circuit, a first resistor connected to the driving power source for the switching element of the inverter means and a first resistor connected to the ground of the driving power source or the switching element of the inverter means are connected. 1 resistor to shift the neutral point voltage to a predetermined value.

As a result, the power supply for the position detection circuit can be a single positive voltage, which facilitates the circuit configuration.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. 1 and 4, those parts that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

Referring to FIG. 1, a brushless motor control apparatus according to the present invention comprises an armature winding U of a brushless motor 4,
The neutral point voltage of the brushless motor 4 is pseudo-obtained by using the terminal voltages of V and W, the direct current component of the neutral point voltage is removed, and the level is shifted to a predetermined level. A position detection circuit 11 is provided which compares the voltage with a predetermined voltage and outputs the comparison result as a position detection signal to the control circuit 10.

Therefore, the position detection circuit 11 includes a resistor circuit 11a, a capacitor 11b, a level shift circuit 11c,
It comprises a predetermined voltage generation circuit 11d and a comparison circuit 11e. The control circuit 10 is the control circuit 6 shown in FIG.
In addition to this function, the position of the rotor of the brushless motor 4 is detected by the output signal (position detection signal) of the comparison circuit 11e of the position detection circuit 11 to obtain the energization switching timing of the brushless motor 4.

Next, the operation of the control device having the above configuration will be specifically described with reference to the time chart of FIG. The three-phase brushless motor 4 is accelerated to such an extent that position detection operation is possible, and the armature windings U, V, W of the brushless motor 4 are accelerated.
It is assumed that three voltage waveforms having a phase difference of 120 degrees are generated in the waveform.

First, the resistor circuit 11a adds a voltage of three terminal voltage waveforms by resistors R1 and R2 and divides the voltage (for example, 5 V).
Output) (see FIG. 2A). This voltage is a pseudo neutral point voltage of the brushless motor 4. When this neutral point voltage is passed through the capacitor 11b, the capacitor 11b
Cuts off the direct current component and outputs it to the input terminal a of the level shift circuit 11c (see FIG. 2B).

On the other hand, the predetermined voltage generating circuit 11d is a DC voltage from the DC power source 8 (for example, a positive voltage for driving the lower arm).
Is divided by resistors R3 and R4 to generate a predetermined positive voltage Va, and the predetermined voltage Va is stabilized by an operational amplifier and output to the comparison circuit 11e. As described in the conventional example,
The lower arm drive voltage is used to drive the transistors X, Y, Z of the inverter section 3.

The level shift circuit 11c shifts the neutral point voltage (see FIG. 2C) input to the terminal a by a predetermined voltage, and the shifted neutral point voltage is compared via the terminal b to the comparison circuit 11e. Output to.

As an example of the level shift circuit 11c, for example, as shown in FIG. 3, a first resistor R7 and a second resistor R8 (resistance ratio; R7: R8 = R3: R4).
It consists of. One end of each of the first and second resistors R7 and R8 is connected to the drive power source (DC power source 8) for the switching element of the inverter unit 3, and the other end is connected to the ground of the DC power source 8 or the switching element of the inverter unit 3. Connect to ground.

As a result, the neutral point voltage can be shifted by the same amount as the predetermined voltage generated by the predetermined voltage generating circuit 11d. That is, the DC voltage from the DC power supply 8 is used.

The level shift circuit 11c is not limited to the circuit configuration shown in FIG. Further, as shown in FIG. 2D, it is preferable to level shift the input neutral point voltage above the zero potential.

The neutral point voltage from the terminal b of the level shift circuit 11c is input to the non-inverting input terminal of the operational amplifier forming the comparison circuit (comparator) 11e, and the predetermined voltage Va generated by the predetermined voltage generation circuit 11d is output. Input to the inverting input terminal of the operational amplifier. As the power source of the operational amplifier, the DC voltage (lower arm driving power source) from the DC power source 8 is used.

As a result, the comparison circuit 11 compares the level-shifted neutral point voltage with the predetermined voltage Va, and outputs the comparison result (see FIG. 2 (e)). This comparison is to obtain the intersection of the neutral point voltage and the predetermined voltage Va, which is the midpoint of the induced voltage generated in the armature windings U, V, W (1/2 point of the induced voltage). is there. That is, FIG.
This is because the voltage waveform of contains the information of the induced voltage generated in the armature windings U, V and W.

The comparison result of the comparison circuit 11, that is, a signal that changes at the intersection of the neutral point voltage and the predetermined voltage Va is input to the control circuit 10, and the control circuit 10 generates an induced voltage by the signal (position detection signal). 1/2 point (detection of rotor position) is determined.

The control circuit 10 detects the position of the rotor by the edge (rising edge, falling edge) of the position detection signal after switching the energization (see the broken line arrow in FIG. 2D). Based on this position detection, a drive signal for driving each transistor of the inverter unit 3 is generated (see FIGS. 2E to 2J), and the energization of the brushless motor 4 is switched.

In this way, the terminal voltage of each armature winding U, V, W is applied and divided to obtain a pseudo neutral point voltage, and the direct current component of the obtained neutral point voltage is removed. , The neutral point voltage obtained by cutting the direct current component is level-shifted to a predetermined level, the neutral point voltage thus leveled is compared with a predetermined voltage, and the induced voltage generated in each of the armature windings U, V, W is 1 A signal (position detection signal) including / 2 points is obtained.

Therefore, only one position detection circuit is required and a simple circuit configuration can be used, and the cost of the control device can be reduced.

Although the neutral point voltage of the brushless motor 4 is artificially obtained externally by using the resistance circuit 11a in the above embodiment, as shown in FIG. When the terminal c is provided for drawing out the point voltage to the outside, this terminal (drawing terminal) c is used. In FIG. 4, the same parts as those in FIG. 1 and the corresponding parts are designated by the same reference numerals, and a duplicate description will be omitted.

In this case, the position detecting circuit 12 uses a voltage dividing circuit 12a for dividing the neutral point voltage from the lead-out terminal c of the brushless motor 4 by R5 and R6 in place of the resistance circuit 11a. The neutral point voltage (for example, about 5V) is passed through the capacitor 11b. Therefore, the circuit configuration of the position detection circuit 11 is further simplified, and the cost can be further reduced.

As is apparent from the circuit diagrams of FIGS. 1 and 4, the DC power source of the DC power source 8 is connected to the predetermined voltage generating circuit 11.
d, the level shift circuit 11c shown in FIG. 3, and the comparison voltage of the comparison circuit 11e, that is, the position detection circuits 11 and 12 need only be supplied with a single positive voltage. The position detection circuits 11 and 12 have a simple circuit configuration, and it is not necessary to provide a new power source, which is advantageous in terms of cost.

[0035]

As described above, according to claim 1 of the controller for a brushless motor of the present invention, the position of the rotor of the brushless motor is detected by using the neutral point voltage of the brushless motor, and Since the energization of the brushless motor is switched based on the position detection, only one system of position detection circuit is required, which simplifies the rotor position detection circuit.
There is an effect that the cost can be reduced.

According to the second aspect of the present invention, the neutral point voltage of the brushless motor is pseudo-obtained by the resistance circuit, and the position of the rotor of the brushless motor is detected by using this neutral point voltage. Since the energization of the brushless motor is switched based on the position detection, the rotor position detection circuit can be simplified and the cost can be reduced as in the first aspect.

According to the third aspect of the present invention, the brushless motor having the lead-out terminal for the neutral point voltage is used, and the output voltage of the lead-out terminal is divided to obtain the neutral point voltage. The position detection circuit can be further simplified, and the cost can be further reduced.

According to the fourth aspect of the present invention, the neutral point voltage is shifted by a predetermined voltage, the shifted neutral point voltage is compared with the predetermined voltage, and the position of the rotor is detected by the comparison result. However, since the predetermined voltage is a positive voltage, there is an effect that the configuration of the position detection circuit is easy in addition to the effects of the first to third aspects.

According to claim 5 of the present invention, since the positive predetermined voltage in claim 4 is obtained from the driving power source for the switching means of the inverter means, it is not necessary to provide a new power source. In addition to the effect of 4, there is an effect that the cost can be further reduced.

According to a sixth aspect of the present invention, in addition to the first to third aspects, the neutral point voltage is set to a predetermined level by two resistors, and the power source of the two resistor circuits is used as a drive power source for the switching means. Since it was obtained from, it is possible to do with a simple circuit, there is no need to install a new power supply,
In addition to the effects of claims 1 to 3, there is an effect that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control device for a brushless motor illustrating an embodiment of the present invention.

FIG. 2 is a schematic flowchart for explaining the operation of the control device shown in FIG. 1;

3 is a schematic partial circuit diagram of the control device shown in FIG. 1. FIG.

FIG. 4 is a schematic block diagram of a brushless motor control device for explaining a modified embodiment of the present invention.

FIG. 5 is a schematic block diagram of a conventional brushless motor control device.

[Explanation of symbols]

1 AC power supply 2 AC / DC conversion unit 3 Inverter unit 4 Brushless motor (sensorless DC brushless motor) 8 DC power supply 10 Control circuit 11, 12 Position detection circuit 11a Resistance circuit 11b Capacitor 11c Level shift circuit 11d Predetermined voltage generation circuit 11e Comparison circuit 12a voltage dividing circuit c lead terminal R7 first resistor R8 second resistor

Claims (6)

[Claims] 1. At least a DC power source is switched by a plurality of switching means of an inverter means to be applied to a brushless motor, while detecting the position of a rotor of the brushless motor, and based on the position detection of the rotor. In a controller for a brushless motor that controls the rotation of the brushless motor by switching the energization of the brushless motor, a direct current component of the neutral point voltage of the brushless motor is removed, and the neutral point voltage is level-shifted to a predetermined level. The brushless motor is provided with position detecting means for comparing the level-shifted neutral point voltage with a predetermined voltage and outputting the comparison result as a position detecting signal, based on the output position detecting signal from the position detecting means. A brushless motor control device characterized in that energization is switched. 2. The position detecting means applies a terminal voltage of an armature winding of the brushless motor, divides the voltage, and artificially obtains a neutral point voltage of the brushless motor, and the neutral point voltage. , A predetermined voltage generating circuit for generating a predetermined voltage, a level shift circuit for predeterminedly shifting the neutral point voltage from which the direct current component has been removed by the generated predetermined voltage, and the shifted neutral voltage. 2. The brushless motor control device according to claim 1, comprising a comparison circuit for comparing a point voltage and the predetermined voltage, and switching the energization of the brushless motor by an output signal of the comparison circuit. 3. The brushless motor has a lead-out terminal for the neutral point voltage of the brushless motor, and the position detecting means has a voltage dividing circuit for obtaining the neutral point voltage from the lead-out terminal, and the neutral point. A capacitor for removing a direct current component of the point voltage, a predetermined voltage generating circuit for generating a predetermined voltage, a level shift circuit for predetermined shifting of the neutral point voltage from which the direct current component is removed by the generated predetermined voltage, and the shifted 2. The brushless motor control device according to claim 1, comprising a comparison circuit for comparing a neutral point voltage with the predetermined voltage, and switching the energization of the brushless motor by an output signal of the comparison circuit. 4. The controller for a brushless motor according to claim 1, wherein the predetermined voltage for shifting the neutral point voltage is a positive voltage. 5. The brushless motor control device according to claim 1, wherein the predetermined voltage generating circuit divides the power supply for driving the switching element of the inverter means to generate a predetermined voltage. 6. The first level shift circuit is connected to a power source for driving a switching element of the inverter means.
And a first resistor connected to the ground of the driving power source or the ground of the switching element of the inverter means, and the neutral point voltage is level-shifted to a predetermined level. 4. A controller for a brushless motor according to any one of 3 to 3.