JPH06205597A - Driver of brushless motor - Google Patents

Abstract

PURPOSE:To prevent oscillation from occurring by PWM control in the terminal voltage of the stator winding in a brushless motor. CONSTITUTION:Position signals are gotten by detecting the terminal voltages UV to WV of the output terminals 18 to 20 of oscillating circuit 3 with the potential dividing circuit 23 consisting of potential dividing resistors 24 to 29, and comparing the detected voltage with the reference voltage VR from a reference voltage generating circuit 33 by means of a control circuit 37, and current application timing signals for turning on or turning off the transistors 6 to 11 of a drive circuit 3 are gotten based on this and a PWM signal. And, a waveform shaping circuit 44 consisting of the series circuit composed of resistors 38 to 40 and capacitors 41 to 43 is constituted between the output terminals 18 to 20 and the earth.

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 device for obtaining a position detection signal based on a terminal voltage of a stator winding.

[0002]

2. Description of the Related Art For example, as a drive motor for a compressor of a refrigerator or an air conditioner, a brushless motor has come to be adopted because of its ease of controlling the rotation speed in the case where the capacity of the compressor needs to be varied. In particular, the relative position of the stator winding and the permanent magnet type rotor is induced in the stator winding without using a position sensor such as a Hall element because of the characteristics such as a small number of drawn wires. A position sensorless system that uses an induced voltage for detection has been adopted.

A conventional brushless motor driving device of this type will be described with reference to FIGS. First,
The overall configuration will be described with reference to FIG. DC power supply 1
The positive and negative terminals of are connected to the input terminals 4 and 5 of the drive circuit 3 via the current detection resistor 2 on the negative terminal side. The negative terminal of the DC power supply 1 is grounded.

The drive circuit 3 serving as output means has an input terminal 4,
NPN-type transistors 6 to 8 and 9 to 11 which are semiconductor switching elements are connected between the three five-phase bridge connection. Diodes 12 to 17 are connected in parallel to the transistors 6 to 11, respectively. The common connection point of the transistors 6 and 9 is the output terminal 18
, The common connection point of the transistors 7 and 10 is connected to the output terminal 19, and the common connection point of the transistors 8 and 11 is connected to the output terminal 20.

The brushless motor 21 includes a stator 2 having U, V and W phase stator windings 22U, 22V and 22W.
2 (see FIG. 9) and a permanent magnet type rotor (not shown). Then, one terminal of the stator windings 22U, 22V and 22W is connected in common, and the other terminals are connected to the output terminals 18, 19 and 20 of the drive circuit 3, respectively.

The voltage dividing circuit 23 serving as the detecting means includes a voltage dividing resistor 2
4 to 29, stator windings 22U, 22V
And 22W each, that is, the output terminal 1 of the drive circuit 3
Between 8, 19 and 20 and the ground (the input terminal 5 which is the ground side terminal of the drive circuit 3), a series circuit of the voltage dividing resistors 24 and 25, a series circuit of the voltage dividing resistors 26 and 27, and a voltage dividing resistor. It is configured by connecting a series circuit of 28 and 29. The common connection points of the voltage dividing resistors 24 and 25, the voltage dividing resistors 26 and 27, and the voltage dividing resistors 28 and 29 are connected to the detection terminal 3 respectively.
It is set to 0, 31 and 32.

Reference voltage generating circuit 3 as reference voltage generating means
3 includes resistors 34 and 35 for voltage division, which are connected between the positive terminal and the negative terminal of the DC power supply 1.
The common connection point of these resistors 34 and 35 is used as a reference terminal 36. Incidentally, the voltage dividing resistor 2 of the voltage dividing circuit 23
The resistance value ratio between the voltage dividing resistors 4, 26 and 28 and the voltage dividing resistors 25, 27 and 29 is set to K: 2 (where K is a natural number), and the resistance value ratio between the resistors 34 and 35 of the reference voltage generating circuit 33 is (K
+1) to 1 is set.

The control circuit 37 as a control means is constituted by including a microcomputer, and its three input ports are connected to the detection terminals 30, 31 and 32, and the other one input port is connected to the reference terminal 36. The speed command signal SV is applied to the other input port, and the six output ports are connected to the bases of the transistors 6 to 11, respectively.

Next, the operation of the above conventional structure will be described with reference to FIG.
It will be described with reference to FIGS. While the brushless motor 21 is rotating, the stator windings 22U, 22V
The terminal voltages UV, VV and WV of 22 and 22 W are the voltage dividing circuit 2
Detection voltage UVa, VVa and WVa divided by 3
Are detected, and these are input to the control circuit 37.
The power supply voltage E of the DC power supply 1 is divided by the reference voltage generation circuit 33 and output as the reference voltage VR, which is input to the control circuit 37.

The control circuit 37 controls these detection voltages UV.
a, VVa and WVa are compared with the reference voltage VR to detect the zero cross point of the induced voltage induced in the stator windings 22U, 22V and 22W. In this case, the voltage dividing resistor 24,
Since the resistance value ratio between the voltage dividing resistors 26 and 28 and the voltage dividing resistors 25, 27 and 29 is K: 2, the detection voltages UVa, VVa and W
Va becomes 2UV / (K + 2), 2VV / (K + 2) and 2WV / (K + 2), respectively. Also, the resistor 34 and the resistor 35
Since the resistance value ratio of (K + 1) to 1 is 1, the reference voltage V
R becomes E / (K + 2). Therefore, the control circuit 37
As a result, the terminal voltages UV, VV and WV and the power supply voltage E
Of the reference voltage VR (= E / 2).

Now, the principle of detecting the position detection signal on behalf of the terminal voltage UV will be described. The control circuit 37 is shown in FIG.
As shown in (a), the terminal voltage UV and the reference voltage VR (=
E / 2), that is, the zero crossing point of the induced voltage induced in the stator winding 22U is detected to detect the phase signal DSU as shown in FIG. 6 (b). obtain. Then, the control circuit 37 calculates a time corresponding to an electrical angle of 30 degrees from this phase signal DSU, and shifts the phase signal DSU by that amount, and as a result, as shown in FIG. 6C, position detection is performed. Obtain the signal PSU. Control circuit 37
Performs the same processing on the other terminal voltages VV and WV to obtain two position detection signals.

Then, the control circuit 37 logically converts these three position detection signals to obtain six base signals which are energization timing signals, supplies them to the transistors 6 to 11 of the drive circuit 3, and sequentially supplies the transistors 6 to 11. 11 to 11 are turned on and off, and the stator windings 22U, 22V and 22W are energized to rotate the rotor.

By the way, the control circuit 37 performs pulse width modulation (PWM) control in order to adjust the output based on the speed command signal SV during the actual operation. Specifically, since the control circuit 37 modulates the base signal given to the transistors 6, 7 and 8 on the positive terminal side of the drive circuit 3 by the PWM signal (pulse signal),
For example, the terminal voltage UV also becomes a pulsed voltage as shown in FIG. 7A, and the phase signal DSU obtained by comparing this with the reference voltage VR also becomes pulsed as shown in FIG. 7B. Therefore, from the phase signal DSU shown in FIG. 7B to the position detection signal PSU shown in FIG.
Can't get The same applies to the other terminal voltages VV and WV.

Therefore, conventionally, in the control circuit 37, as shown in FIG. 8B, the enable signal SE is generated in synchronization with the PWM signal (pulse signal), and only when the enable signal SE is generated, for example, the terminal. The configuration is such that the comparison between the voltage UV and the reference voltage VR is permitted, so that the continuous phase signal DSU similar to that of FIG. 6B can be obtained as shown in FIG. 8C. The same applies to the other terminal voltages VV and WV.

[0015]

Now, as shown in FIG. 9, the transistor 6 of the drive circuit 3 is turned on / off by the PWM control and the transistor 10 is turned on to energize the stator windings 22U and 22V of the brushless motor 21. The equivalent circuit in the case of doing is as shown in FIG. That is, FIG.
0, the inductances of the stator windings 22U, 22V and 22W are indicated by L22U, L22V and L22W, and the emitter. The stray capacitance between the collectors is indicated by C11 and transistor 6 is switch S
It is shown by W6 and the diode 15 is shown by switch SW15.

Therefore, the transistor 6 under PWM control
When the switch 6 is on, the switch SW6 is turned on, and when the transistor 6 is off, the switch SW15 is turned on. As a result, the switches SW6 and SW15 are alternately turned on during the PWM control of the transistor 6, and the voltage at the common connection point of the inductances L22U, L22V and L22W repeats the high level and the low level. Capacitance C
The voltage at the common connection point of 11, that is, the terminal voltage WV of the output terminal 20 does not become a rectangular wave, and as shown in FIG. 11A, vibration is generated when the PWM signal (pulse signal) is switched. .

Thus, when the terminal voltage WV oscillates,
Since the waveform reciprocates up and down with respect to the reference voltage VR in the vicinity of the reference voltage VR, it becomes impossible to accurately detect the zero-cross point of the induced voltage in the terminal voltage WV. Such a problem also occurs at other terminal voltages UV and VV.

In order to eliminate such a problem, conventionally, as shown in FIG. 11B, it may be considered to shift the enable signal SE to avoid the vibrating portion of the terminal voltage WV. Has been. However, FIG.
As shown in (a), when the duty of the PWM signal is small and the pulse width is small in order to rotate the brushless motor 21 at a low speed, the detection period by the enable signal SE disappears or decreases, and the It becomes impossible to detect such a phase signal, and the brassless motor 21 cannot be driven, or a smooth start cannot be performed, which causes a new problem of vibration.

The present invention has been made in view of the above circumstances, and an object thereof is to be able to obtain an accurate position detection signal even when the duty of pulse width modulation is small and to reliably drive a brushless motor. Another object of the present invention is to provide a drive device for a brushless motor that can perform smooth start and does not generate vibration.

[0020]

A brushless motor drive apparatus according to the present invention comprises a detecting means for detecting terminal voltages of stator windings of a plurality of phases of a brushless motor, a reference voltage generating means for generating a reference voltage, A position detection signal is obtained by comparing the reference voltage from the reference voltage generation means with the detection voltage from the detection means, and an energization timing signal is output based on the position detection signal and the pulse width modulation signal for output adjustment. Control means, output means for energizing the stator winding based on the energization timing signal from the control means, and waveform shaping of the terminal voltage connected to each terminal of the stator windings of the plurality of phases. The configuration is characterized by including waveform shaping means.

In this case, the detecting means is composed of a voltage dividing resistor connected between the terminals of the stator windings of a plurality of phases and the ground side terminal of the detecting means, and the waveform shaping means is a fixing means of the plurality of phases. It is composed of a series circuit of a resistor and a capacitor connected between the terminal of the subsidiary winding and the ground side terminal of the output means, and the resistance value of the resistance of the series circuit is 50 times the resistance value of the voltage dividing resistor.
It is better to set it to% or less.

Further, the detecting means is composed of a voltage dividing resistor connected between the terminals of the stator windings of a plurality of phases and the ground side terminal of the output means, and the waveform shaping means is a stator of the plurality of phases. It may be configured by a resistor connected between the winding terminal and the ground side terminal of the output means, and the resistance value of the resistor may be set to 50% or less of the resistance value of the voltage dividing resistor.

[0023]

According to the brushless motor driving device of the present invention, since the terminal voltage of the stator winding of each phase in the brushless motor is waveform shaped by the waveform shaping means, it is possible to perform each pulse width modulation. Oscillation does not occur in the terminal voltage, and therefore an accurate position detection signal can be obtained by comparison with the reference voltage from the reference voltage generating means.

According to the brushless motor driving device of the second aspect, since the waveform shaping means is composed of a series circuit of a resistor and a capacitor, the waveform shaping means is accumulated in the stray capacitance of the semiconductor switching element of the output means. The electric charge is discharged by the resistor, so that the waveform of the terminal voltage of the stator winding of each phase is shaped. In this case, the capacitor acts as a switching element that allows only the vibration generated in the terminal voltage to pass.

According to the brushless motor driving device of the third aspect, since the waveform shaping means is constituted by the resistor, the electric charge accumulated in the floating electrostatic capacitance of the semiconductor switching element of the output means is discharged by the resistor. Therefore, the waveform of the terminal voltage is shaped with a simple structure.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In this embodiment, FIG.
The same parts as those of the conventional example shown in FIGS.

That is, in FIG. 1, between the output terminals 18, 19 and 20 of the drive circuit 3 and the ground, a resistor 38,
A series circuit of 39 and 40 and capacitors 41, 42 and 43 is connected to each other, and thus a waveform shaping circuit 44 as a waveform shaping means is configured. In this case, the resistance values of the resistors 38, 39 and 40 of the waveform shaping circuit 44 are the sum of the resistance values of the voltage dividing resistors 24 and 25 of the voltage dividing circuit 23, the sum of the resistance values of the voltage dividing resistors 26 and 27, and Each of the sums of the voltage dividing resistors 28 and 29 is set to 50% or less.

As shown in FIGS. 9 to 12, when the terminal voltage WV (see FIG. 2) is vibrated, the emitter of the transistor 11 of the drive circuit 3,
The charge accumulated in the floating electrostatic capacitance between the collectors is the resistance 40
Is discharged by the terminal voltage WV of FIG.
The waveform is shaped as shown in (a), and no vibration occurs. As a result, the enable signal SE does not need to be shifted as shown in FIG. In this case, the capacitor 43 acts as a switching element that passes only the vibration component of the terminal voltage WV. Such an operation is the same for the other terminal voltages UV and VV, and the waveform shaping of the terminal voltages UV and VV is similarly performed.

As described above, according to the present embodiment, the waveform shaping circuit 44 shapes the waveforms of the terminal voltages UV, VV and WV, so that the terminal voltages UV, VV and W are obtained.
Since V does not vibrate, it is not necessary to shift the enable signal SE. Accordingly, in the configuration in which the PWM control is performed by the control circuit 37 to adjust the output, even if the PWM duty is reduced and the pulse width of the PWM signal is reduced in order to operate the brushless motor 21 at a low speed, the position detection is performed. Signal (PSU, P
SV and PSW) can be accurately obtained, and the brushless motor 21 can be reliably driven.
It can be started smoothly and does not generate vibration.

Although the capacitors 41 to 43 are provided in the waveform shaping circuit 44 in the above embodiment, the capacitors 41 to 43 are omitted as in the second embodiment of the present invention shown in FIG. 4, for example. Then, the waveform shaping circuit 45, which is a waveform shaping means including only the resistors 38 to 40, may be configured. Also according to this second embodiment, the terminal voltages UV, VV and W
There is an advantage that the waveform shaping effect of V can be obtained and can be realized with a simple configuration.

Besides, the present invention is not limited to the above-mentioned embodiments, and it is needless to say that the present invention can be appropriately modified and carried out within a range not departing from the gist.

[0032]

As described above, the brushless motor driving device of the present invention is configured to waveform-shape the terminal voltage of the stator winding in the brushless motor, so that even if output adjustment is performed by pulse width modulation. It is possible to prevent the terminal voltage from vibrating. Therefore, even if the duty of the pulse width modulation control becomes small, the position detection signal can be accurately obtained, the brushless motor can be reliably driven, and it can be started smoothly. This produces the excellent effect of being able to generate and not generating vibration.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 Waveform diagram of terminal voltage

FIG. 3 is a waveform diagram of a terminal voltage and an enable signal.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 6 is an explanatory diagram of the principle for obtaining a position detection signal.

FIG. 7 is a view corresponding to FIG.

8 is a view equivalent to FIG. 6 for solving the problem of FIG. 7.

FIG. 9 is an electrical configuration diagram for explaining a principle that a terminal voltage vibrates.

FIG. 10 is an equivalent circuit diagram of the same.

FIG. 11 is an explanatory diagram for avoiding oscillation of terminal voltage.

FIG. 12 is an explanatory diagram of a conventional defect.

[Explanation of symbols]

In the drawing, 3 is a drive circuit (output means), 4 and 5 are input terminals, 6 to 11 are transistors (semiconductor switching elements), 18 to 20 are output terminals, 21 is a brushless motor, and 23 is a voltage dividing circuit (detection means). ), 24 to 29 are voltage dividing resistors, 33 is a reference voltage generating circuit (reference voltage generating means),
37 is a control circuit (control means), 38 to 40 are resistors, 4
1 to 43 are capacitors, and 44 and 45 are waveform shaping circuits (waveform shaping means).

Claims (3)

[Claims] 1. A detection means for detecting terminal voltages of a plurality of phases of stator windings of a brushless motor, a reference voltage generation means for generating a reference voltage, a reference voltage from the reference voltage generation means and the detection means. A control means for obtaining a position detection signal by comparison with the detection voltage and outputting an energization timing signal based on this position detection signal and a pulse width modulation signal for output adjustment; and on the basis of the energization timing signal from this control means. Drive device for brushless motor, comprising: output means for energizing the stator windings and a waveform shaping means connected to each terminal of the stator windings of the plurality of phases to shape the waveform of the terminal voltage. . 2. The detecting means is composed of a voltage dividing resistor connected between the terminals of the stator windings of a plurality of phases and the ground side terminal of the output means, and the waveform shaping means is a stator of the plurality of phases. It is composed of a series circuit of a resistor and a capacitor connected between the terminal of the winding and the ground side terminal of the output means, and the resistance value of the resistance of the series circuit is 5 of the resistance value of the voltage dividing resistor.
The drive device for the brushless motor according to claim 1, wherein the drive ratio is set to 0% or less. 3. The detecting means comprises a voltage dividing resistor connected between a terminal of a stator winding of a plurality of phases and a ground side terminal of the output means, and the waveform shaping means comprises a stator of the plurality of phases. It is composed of a resistor connected between the terminal of the winding and the ground side terminal of the output means, and the resistance value of the resistor is set to 50% or less of the resistance value of the voltage dividing resistor. The drive device for the brushless motor according to claim 1.