JP3258743B2 - Brushless motor drive - Google Patents

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 apparatus for controlling an inverter having a plurality of switching elements to rotate a rotor of a brushless motor.

[0002]

2. Description of the Related Art A conventional brushless motor driving apparatus is disclosed in, for example, Japanese Patent Publication No.
As disclosed in Japanese Unexamined Patent Publication No. 1-293191, the position of a magnetic pole of a rotor is detected based on each terminal voltage of a brushless motor, thereby controlling an inverter including a plurality of switching elements to rotate the brushless motor. There is something that rotates the child.

Here, such a driving device includes, for example, field effect transistors (hereinafter referred to as FETs) S1 to S6 as six switching elements connected in a three-phase bridge as shown in FIG. An inverter 1, a brushless motor (hereinafter referred to as a motor) 2 in which armature windings are star-connected to a neutral point, and terminal voltages Vu, Vv, Vw of terminals U, V, W of the motor 2 and a neutral point A rotor that detects rotor position signals Cu, Cv, and Cw (see FIG. 12B) indicating the magnetic pole position of the rotor 3 that is the rotor of the motor 2 by comparing the voltage Vn (see FIG. 12A). The position detector 4 and the rotor position signal C
The phase of u, Cv, Cw is 60 ° × n + 30 °, for example, 9
A rotor position signal delay unit 5 that delays by 0 ° (n = 1) to generate delay signals Du, Dv, and Dw (see FIG. 12C) serving as a basis of the commutation timing, and a signal from the rotor position signal delay unit 5 Based on the delay signals Du, Dv, Dw, the F
FET drive signal generator 6 for generating an FET drive signal (not shown) for controlling on / off of ETS1 to S6
There are those composed of

Then, the FETs S1 to S6 are turned on / off by an FET drive signal to excite the respective phases of the motor 2, while the rotor position signals Cu, C
After delaying v and Cw by 90 ° in the rotor position signal delay unit 5 to obtain delay signals Du, Dv, and Dw, the delay signals Du, Dv, and Dw are input to the FET drive signal generator 6 to generate an FET drive signal. The FETs S1 to S6 are turned on and off at timings at which the motor 2 is rotated efficiently.

[0005]

However, in such a conventional brushless motor driving device, as shown in FIG. 11, the rotor position detecting section 4 and the rotor position signal delaying section 5 each need three phases. There is a problem that the circuit configuration becomes complicated.

Further, since the rotor position signal processing is performed by each of the rotor position detection section 4 and the rotor position signal delay section 5, the signal processing varies.
There has been a problem that accurate rotor position detection cannot be performed, and the commutation timing is thereby shifted.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brushless motor driving device capable of accurately detecting a rotor position with a simple circuit configuration.

[0008]

[0009]

[0010]

According to the present invention, there is provided a brushless motor driving apparatus which includes a plurality of switching elements and controls an inverter to rotate a rotor of a brushless motor. And the low-side switching elements are simultaneously turned on and off, and when turned off, a current due to stored energy flows through a flywheel diode provided in the switching elements, and each terminal of the brushless motor is turned on and off during the switching elements. The average voltage of the maximum terminal voltage of the phase that has become the maximum of the voltages and the minimum terminal voltage of the phase that has become the minimum, and a signal obtained by comparing the neutral point voltage of the brushless motor with the signal of the rotor. The inverter is controlled by detecting a magnetic pole position.

[0011]

With the above arrangement, the switching element for driving the brushless motor simultaneously turns on and off both the high-side and low-side switching elements when the motor is driven, and uses the stored energy through the flywheel diode provided in the switching element when the motor is off. Electric current flows,
A signal obtained by comparing the average voltage of the maximum terminal voltage of the maximum phase and the minimum terminal voltage of the minimum phase of each terminal voltage with the neutral point voltage of the brushless motor at this time. The rotor magnetic pole position can be detected,
The inverter is controlled by this detection.

[0012]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a brushless motor driving device according to a first embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts.

In FIG. 1, reference numeral 7 denotes a DC power supply voltage E of 1 /
A half voltage (E / 2) input from the voltage dividing resistor section 8 for dividing the voltage into 2 and the neutral point voltage Vn are compared to detect a rotor position signal indicating the magnetic field position of the rotor 3 as described later. This is a rotor position detection unit for performing the operation.

Here, the terminal voltages Vu, V of the motor 2
v and Vw are shown in FIG. 2 as the FETs S1 to S6 are turned on and off.
As shown in FIG. 2A, the neutral point voltage Vn is periodically increased and decreased between 0 and E, whereby the neutral point voltage Vn is reduced by half as shown in FIG.
The increase / decrease is repeated based on the voltage (E / 2). In the figure, Sp is a spike generated when the FETs S1 to S6 are turned on and off.

When the rotor position detector 7 compares the half voltage (E / 2) with the neutral point voltage Vn, as shown in FIG. A rotor position signal Cn that repeats on and off every time the voltage becomes equal to two voltages (E / 2) is obtained.

The rotor position signal Cn indicates that the position of the rotor 3 is equal to the neutral point voltage Vn and the half voltage (E / 2).
Are equal to each other, that is, the magnetic field generated by the magnetic field of the rotor 3 and the magnetic field generated by one armature winding are shifted by, for example, 90 °.

However, since the signal for generating commutation timing cannot be used as it is, the rotor position signal Cn is input to the rotor position signal delay unit 9. Here, the rotor position signal delay unit 9
Sets the phase of the rotor position signal Cn to 60 ° × n + 30 °,
For example, as shown in FIG. 2D, the delay signal is to be delayed by 30 ° (n = 0) to generate a delay signal Dn that matches the commutation timing. In the rotor position signal delay unit 9, the spike Sp is removed.

The delay signal Dn that coincides with the commutation timing is input to the FET drive signal generator 6, and the FET drive signal generator 6 turns on and off the FETs S1 to S6 in accordance with the rise and fall thereof. The FET drive signal (not shown) is generated.

In the thus constructed brushless motor driving device, when the motor 2 is energized, the rotor position detecting unit 7 first receives the 1/2 voltage (E) inputted from the voltage dividing resistor 8. / 2) and the neutral point voltage Vn
And a rotor position signal Cn is detected.

Next, the rotor position signal Cn is input to the rotor position signal delay unit 9 and its phase is delayed by 30 ° to become a delay signal Dn that matches the commutation timing.
It is input to the ET drive signal generator 6. And FE
An FET drive signal is generated by the T drive signal generator 6, and the FET drive signals are used to generate the FETs S1 to S6.
Is turned on and off, and the motor 2 is driven efficiently.

As described above, by comparing the 1/2 voltage (E / 2) with the neutral point voltage Vn in the rotor position detecting section 7, the rotor position signal Cn can be detected. Then, the rotor position signal Cn is delayed in the rotor position signal delay unit 9 to generate a delay signal Dn that matches the commutation timing, and the delay signal Dn is input to the FET drive signal generation unit 6 to generate the FET drive signal. Can be made.

Further, since the detection of the rotor position signal Cn can be performed by a set of the rotor position detection unit 7 and the rotor position signal delay unit 9, the circuit configuration is simplified, and the processing of the rotor position signal Cn also varies. Disappears.

Note that, as shown in FIG.
Wiring is drawn out from between the motor 2 and the same three resistors R
Is formed, the neutral point of the pseudo-neutral point forming circuit 10 is defined as a pseudo-neutral point, and the neutral point voltage Vn of the neutral point is set to 1/2. Voltage (E /
By comparing with 2), the rotor position signal Cn can be detected without wiring to the motor 2.

In the above description, it has been described that the neutral point voltage Vn is always detected. However, when the motor is driven by the PWM control, for example, as shown in FIG. 6FETS6
Is turned on, the current flows as shown by the arrow, but PW
When the first FET S1 is turned off by the M off signal, the voltage is grounded and becomes zero.

In this case, that is, during the PWM off signal period (see FIG. 5C), the terminal voltage and the neutral point voltage are not output or greatly change (FIG. 5).
(See (a) and (b).) During this period, the position of the rotor cannot be detected.

Therefore, when the motor is driven by the PWM control, the FET drive signal generator 6 shown in FIG. 1 turns off the first FET S1.
When the drive signal is generated, the FET drive signal applied to the sixth FET S6 is turned off.

When the first FET S1 and the sixth FET S6 are simultaneously turned off in this way, a current flows as shown by an arrow as shown in FIG. 6, and the terminal voltage and the neutral point voltage are changed as shown in FIG. Since it changes continuously as shown in (b), the neutral point voltage can be detected even during the PWM off signal period, and the position of the rotor can be detected.

By the way, in such a PWM control, when the PWM off signal period is long, FIG.
As shown in (b), after the PWM signal shifts from the on state to the off state, a portion a in which the current that has flowed stops flowing and the current does not flow occurs.

In the part a where no current flows,
All the FETs S1 to S6 are turned off, the terminal voltage of the motor 2 with respect to the ground of the DC power supply voltage E is not determined, and even if the half voltage (1 / 2E) is compared with the neutral point voltage Vn, the rotor position signal Cannot be detected. At this time, induced voltages Eu, Ev, and Ew are generated at the terminals U, V, and W as shown in FIG.

Therefore, in such a case, as shown in FIG. 10, wiring is drawn out from between the inverter 1 and the motor 2 to form the same six diodes D1 to D6 and the same two resistors R1 and R2. To form the pseudo voltage circuit 11.

The upper three diodes D1 to D3 of the six diodes D1 to D6 are connected to terminals U,
The maximum induced voltage of the induced voltages Eu, Ev, Ew generated in V and W, that is, the maximum terminal voltage, and the three lower diodes D4 to D6 output the minimum induced voltage, that is, the minimum terminal voltage. Things.

The six diodes D1 to D6
Thus, for example, when the U-phase induced voltage Eu becomes maximum and the V-phase induced voltage Ev becomes minimum as in the period A in FIG. 9A, the upper three diodes D1 to D3 output U The phase induced voltage Eu is output, and the V-phase induced voltage Ev is output from the lower three diodes D4 to D6.

Note that the maximum induced voltage Eu and the minimum induced voltage Ev output by these three diodes D1 to D3 and D4 to D6 are the same two resistors R1,
The voltage is averaged by R2 to become an average voltage (E / 2) ', which periodically increases and decreases with reference to the neutral point voltage Vn as shown in FIG.

Here, the average voltage (E / 2) 'is input to the rotor position detector 7 and compared with the neutral point voltage Vn in the rotor position detector 7, as shown in FIG. The rotor position signal Cn can be detected.

As described above, instead of the 1/2 voltage (E / 2), the average voltage (E / 2) 'of the maximum induced voltage and the minimum induced voltage of the induced voltages Eu, Ev, Ew and the neutral point voltage Vn By comparing with the above, the rotor position signal can be detected even in a portion where no current flows during the off signal period.

[0038]

As described above, according to the present invention, in the PWM control, even in a portion where no current flows during the off signal period, the average of the maximum terminal voltage and the minimum terminal voltage of the terminal voltage is compared with the neutral point voltage. By doing so, the rotor position signal can be detected.

[0039]

[Brief description of the drawings]

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

FIG. 2 is a diagram showing signals generated in respective components of the driving device.

FIG. 3 is a circuit diagram of a brushless motor driving device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a current flowing in a conventional brushless motor driving device that performs PWM control.

FIG. 5 shows the terminal voltage, neutral point voltage and PW of the driving device.
The figure which shows an M signal.

FIG. 6 is a diagram showing an example of a current flowing in a brushless motor driving device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing a terminal voltage and a neutral point voltage of the driving device.

FIG. 8 is a diagram showing a terminal voltage and a neutral point voltage when the off time of the PWM control is long.

FIG. 9 shows an induced voltage when the off time of the PWM control is long,
The figure which shows an average voltage and a neutral point voltage.

FIG. 10 is a circuit diagram of a brushless motor driving device according to a fourth embodiment of the present invention.

FIG. 11 is a circuit diagram of a conventional brushless motor driving device.

FIG. 12 is a diagram showing signals generated in respective components of the driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter 2 Brushless motor 3 Rotor 4, 7 Rotor position detecting part 10 Pseudo neutral point formation circuit 11 Pseudo voltage circuit Cn Rotor position signal S1-S6 Field effect transistor

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-230392 (JP, A) JP-A-2-1599992 (JP, A) JP-A-4-372595 (JP, A) JP-A-6-230 178587 (JP, A) JP-A-61-42288 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/00-6/24

Claims (1)

(57) [Claims] 1. A brushless motor drive device comprising a plurality of switching elements and controlling an inverter to rotate a rotor of a brushless motor, wherein the switching elements are connected to a high side when the motor is driven.
And low-side switching elements are simultaneously turned on
Off, and a fly provided in the switching element when off.
The current due to the stored energy through the wheel diode
So that the switching element is turned on and off
Of the terminal voltages of the brushless motor during
Maximum terminal voltage of the phase that has increased and the minimum end of the phase that has minimized
And the neutral point of the brushless motor
A brushless motor driving device, wherein the inverter is controlled by detecting a magnetic pole position of the rotor based on a signal obtained by comparing the voltage with a voltage .