JP2738109B2 - Driving device for brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and in particular, detects a relative position between a magnet rotor and an armature winding by an induced voltage induced in an armature winding. The present invention relates to a brushless motor driving device that operates based on a position detection signal.

2. Description of the Related Art A brushless motor usually requires a detector for detecting the magnetic pole position of its rotor.If it is difficult to use the magnetic pole position detector, for example, the magnetic pole position detector is omitted and the motor is removed. A method of generating a commutation signal of a motor based on a voltage signal induced in a slave winding has been used. The method will be described below.

FIG. 2 is a block diagram of a brushless motor operating apparatus according to the present method, wherein 1 is a DC power supply, 2 is a semiconductor switching element group, and six transistors U to Z and six diodes respectively connected in anti-parallel. Consists of Reference numeral 3 denotes a brushless motor, which comprises an armature winding 4 and a magnet rotor 5 connected in three phases. Reference numeral 6 denotes a filter circuit for performing waveform processing on a voltage signal induced in the armature winding 4, reference numeral 7 denotes a comparison circuit for comparing output signals of the filter circuit 6, and reference numeral 8 denotes the comparison circuit 7.
Is a control circuit for controlling conduction and cutoff of the semiconductor switching element group 2 in accordance with the output signal of Here, as the filter circuit 6, a circuit in which an integrating circuit is provided at a stage subsequent to the differentiating circuit shown in FIG. 5A, and a circuit in which a differentiating circuit is provided after the integrating circuit shown in FIG.

The operation in the above configuration will be described with reference to FIGS.

FIG. 3 shows the relationship between the voltage signal induced in the armature winding 4, the output signal of the filter circuit 6, and the output signal of the comparison circuit U.
This is for one phase. In the figure,
An output signal obtained by subjecting the U-phase induced voltage Vu to waveform processing by the filter circuit 6U is like 60U. V-phase and W-phase induced voltages V
v and Vw are processed by the filter circuits 6V and 6W, respectively.
V, 60W, and the combined waveform becomes 71U. The comparison circuit 7 compares 60U and 71U to obtain a comparison circuit output of 70U. This output signal becomes a position detection signal of the magnet rotor 5.

The above waveform processing is also performed for the V phase and the W phase, and position detection signals 70V and 70W are obtained, respectively. These position detection signals 70U to 70W are signals having phases different from each other by 120 ° as shown in FIG. These position detection signals are logically operated by the control circuit 8, and commutation signals 8U to 8Z are generated. The transistors of the semiconductor switching element group 2 are switched by these commutation signals, so that the brushless motor 3 continuously generates a rotational torque. The above operation mode will be referred to as a position detection operation mode.

On the other hand, when the brushless motor 3 is stopped, no induced voltage is generated in the armature winding 4, so that at the time of startup, 8U to 8U in FIG.
An 8Z commutation signal is externally applied at a low frequency to forcibly rotate the brushless motor 3 at a low speed. Due to this rotation, an induced voltage is generated in the armature winding 4, which is subjected to waveform processing by the filter circuit 6 and compared by the comparison circuit 7 to obtain position detection signals of 70U to 70W in FIG. The above is called a synchronous operation mode. When the position detection signal is established in the synchronous operation mode, the mode shifts to the position detection operation mode in which operation is performed based on the signal.

However, in the configuration of the filter circuit as shown in FIG. 5, the capacitor 6c of the differentiation circuit and the capacitor of the integration circuit
Since a high withstand voltage of the power supply voltage level is required for 6e, the size of the device is increased and the cost is increased. Electrolytic capacitors are often used for high withstand voltage, moderate capacitance, and miniaturization.However, since the electrolytic capacitors have poor high-frequency characteristics, the stability of the position detection signal with respect to load fluctuations deteriorates. The motor easily loses synchronism when fluctuating.

5A and 5B, there is no discharge path for the capacitor 6c in the differentiating circuit, and the circuit always has a DC component when the brushless motor is stopped. When the brushless motor is started in this state, the filter circuit output immediately after the start of the synchronous operation mode (for example, 60U for the U phase) also has a DC component as shown by the dotted line in FIG. There has been a problem that the transition is likely to fail unless it is attenuated during the transition.

The present invention has been made in view of the above problems, and has been made to reduce the size of filter
An object of the present invention is to provide a brushless motor operating device which can realize cost reduction and improvement in stability at the time of load change, and can smoothly shift from a synchronous operation mode to a position detection operation mode at startup.

Means for Solving the Problems To solve the above problems, a brushless motor operating device of the present invention includes a DC power supply, a semiconductor switching element group for energizing and interrupting a current to an armature winding of the brushless motor, and A plurality of filter circuits that perform waveform processing on an induced voltage induced in the armature winding, a comparison circuit that compares the plurality of filter circuit outputs and a composite wave thereof, and a semiconductor switching element group according to the comparison circuit output. The filter circuit has a configuration in which a capacitor is arranged in series after a voltage dividing circuit composed of a plurality of resistors, and an integrating circuit is arranged in the subsequent stage. .

Operation According to the present invention, the capacitor in the filter circuit can be configured with a low withstand voltage product by the above-described configuration, and the size and cost of the device can be reduced. Further, as the withstand voltage decreases, it becomes easier to use a small-sized capacitor having good high-frequency characteristics, so that it is possible to stabilize the position detection signal with respect to a load change or the like and to extend the life of the circuit. In addition, by providing a discharge path for the capacitor, when the brushless motor is started, there is no DC component remaining in the capacitor, and the transition from the synchronous operation mode to the position detection operation mode can be smoothly performed.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The schematic configuration of the brushless motor driving device according to the embodiment of the present invention is similar to that of the conventional device shown in FIG.
Description is omitted.

FIG. 1 is a configuration diagram of the filter circuit 6, the comparison circuit 7, and the control circuit 8 of the present embodiment. The filter circuit 6 includes U, V, W
Filter circuits 6U, 6V, 6W for processing the induced voltage of each phase
The filter circuit 6U further includes resistors 6a and 6b, a capacitor 6c, and an integrating circuit 6d.A capacitor 6c is arranged in series at a stage subsequent to a voltage dividing circuit composed of the resistors 6a and 6b, and an integrating circuit 6d is arranged at a subsequent stage. Is arranged. The comparison circuit 7 compares itself with the synthesized waves of the other two phases for the filter circuit outputs 60U to 60W for the three phases, and detects the position detection signals 70U to 70W.
And the control circuit 8 generates commutation signals 8U to 8Z shown in FIG.

In the above configuration, for example, in the case of the U-phase, the induced voltage Vu of the armature winding 4 is divided by the resistors 6a and 6b,
Is 6b / (6a + 6b) * Vu. By appropriately selecting this voltage division ratio, the voltage across the resistor 6b can be kept low. As a result, the circuit after the resistor 6b can be used as a low voltage circuit, and the capacitor used for the differentiation circuit and the integration circuit
For 6c and 6e, low withstand voltage products can be used.

Also, since the DC component accumulated in the capacitor 6c of the differentiating circuit is discharged through the resistor 6b, the DC component does not remain in the capacitor 6c when the brushless motor is stopped, so that the synchronous operation mode at the next start-up and the position detection operation mode The transition can be made smoothly.

Although the U phase has been described above, the same applies to the V phase and the W phase. Further, in this embodiment, the integrating circuit is a circuit using an operational amplifier, but may be a first-order delay circuit using a resistor and a capacitor.

Effect of the Invention As described above, the present invention provides a DC power supply, a semiconductor switching element group for energizing and interrupting a current to an armature winding of a brushless motor, and a waveform processing of an induced voltage induced in the armature winding. A plurality of filter circuits, a comparison circuit for comparing the output of the plurality of filter circuits and a composite wave thereof, and a control circuit for controlling conduction and interruption of the semiconductor switching element group according to the output of the comparison circuit; The circuit is composed of a series of capacitors in series with a voltage divider consisting of multiple resistors, followed by an integrator in the subsequent stage. Thus, cost can be reduced. Further, as the withstand voltage decreases, it becomes easier to use a small-sized capacitor having good high-frequency characteristics, and it is possible to stabilize the position detection signal against a load change or the like and to prolong the life of the circuit. Further, by providing the discharge path of the capacitor, when the briless motor is started, there is no residual DC component in the capacitor, and the transition from the synchronous operation mode to the position detection operation mode can be smoothly performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a brushless motor driving device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of the driving device and a conventional driving device, and FIG. 3 is a conventional filter circuit and comparison circuit. 4 is a timing chart of the position detection signal and the commutation signal, FIG. 5 is a configuration diagram of the filter circuit, and FIG. 6 is an output waveform diagram of the filter circuit at startup. 1 DC power supply 2 Semiconductor switching element group 3
... brushless motor, 4 ... armature winding, 5 ... magnet rotor, 6 ... filter circuit, 6a, 6b ... resistance, 6c, 6e
…… Capacitor, 6d …… Integration circuit, 7 …… Comparison circuit, 8
... Control circuit.

Claims (1)

(57) [Claims] 1. A brushless motor having a plurality of phase armature windings connected to a neutral point non-ground and a magnet rotor, a DC power supply, and a semiconductor for energizing and interrupting a current to the armature windings. A switching element group, a plurality of filter circuits for performing waveform processing on an induced voltage induced in the armature winding, a comparison circuit for comparing outputs from the plurality of filter circuits and a composite wave thereof, and an output of the comparison circuit. A control circuit for controlling conduction and cutoff of the semiconductor switching element group accordingly, wherein the filter circuit arranges a capacitor in series at a stage subsequent to a voltage dividing circuit constituted by a plurality of resistors, and includes an integrating circuit at the subsequent stage. Operating device for brushless motor.