JPH06253588A - Driver for brushless motor - Google Patents

Abstract

PURPOSE:To provide a driver for position sensorless brushless motor performing PWM control in which a position detection signal can be obtained easily even if the PWM carrier frequency is increased. CONSTITUTION:A voltage dividing circuit 32 detects terminal voltages UV, VV and MV of the stator windings 22U, 22V and 22W of a brushless motor 21 which are then delayed through delay circuits 48, 49, 50. In this regard, the delay circuits 48-50 are set to rise earlier than PWM carrier frequency and fall slower than the commutation frequency for switching conduction of the stator windings 22U-22W. Comparators 38-40 compare delay detection voltages from the delay circuits 48-50 with a reference voltage VR and a control circuit 46 obtains a position detection signal of the brushless motor based on the comparison results.

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 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. A series circuit of 28 and 29 is connected. 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 used as detection terminals 30, 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.

The resistance value ratio between the voltage dividing resistors 24, 26 and 28 and the voltage dividing resistors 25, 27 and 29 of the voltage dividing circuit 23 is K.
The resistance value ratio of the resistors 34 and 35 of the reference voltage generating circuit 33 is set to (K + 1): 1.
Is set to.

The comparing means 37 is composed of three comparators 38, 39 and 40, each non-inverting input terminal (+) is connected to the detection terminals 30, 31 and 32, and each inverting input terminal (-). Is connected to the reference terminal 36 of the reference voltage generating circuit 32.

The control circuit 41, which is a control means, is mainly composed of a microcomputer. When functionally shown in a block diagram, a main control circuit 42, a voltage command signal generation circuit 43, a pulse width modulation (PWM) signal. It comprises a generation circuit 44 and an enable signal generation circuit 45. Then, in the main control circuit 42, the three input ports are connected to the output terminals of the comparators 38 to 40, and the other two input ports are connected to the input terminals of the PWM signal generation circuit 44 and the enable signal generation circuit 45. The six output ports are connected to the bases of the transistors 6 to 11, respectively,
The other output port is connected to the input terminal of the voltage command signal generation circuit 43.

Further, in the voltage command signal generating circuit 43, the speed command signal SV is given to the other input terminal, and the output terminal is connected to the input terminal of the PWM signal generating circuit 44. The other output terminal of the PWM signal generation circuit 44 is connected to the input terminal of the enable signal generation circuit 45.

Next, the operation of the above conventional structure will be described with reference to FIG.
Also, description will be made with reference to FIG. 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
And are input to the non-inverting input terminals (+) of the comparators 38 to 40. 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 inverting input terminals (−) of the comparators 38 to 40.

The comparators 38 to 40 compare the detection voltages UVa, VVa and WVa with the reference voltage VR to detect the zero cross points of the induced voltages induced in the stator windings 22U, 22V and 22W. In this case, the voltage dividing resistor 2
Since the resistance value ratio between the voltage dividing resistors 4, 26 and 28 and the voltage dividing resistors 25, 27 and 29 is K: 2, the detection voltages UVa, VVa and WVa are 2UV / (K + 2) and 2VV / (K +, respectively).
2) and 2 WV / (K + 2). Further, since the resistance value ratio of the resistors 34 and 35 is (K + 1): 1, the reference voltage VR is E / (K + 2). Therefore, the comparator 38
To 40 result in terminal voltages UV, VV and WV
And a reference voltage VR (= E / 2) that is ½ of the power supply voltage E.

Here, the principle of detection of the position detection signal will be described with the terminal voltage UV as a representative. The comparator 38 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. 9B. obtain. Then, the main control circuit 42 calculates a time corresponding to an electrical angle of 30 degrees from the phase signal DSU, and shifts the phase signal DSU by that amount, so that FIG.
As shown by, the position detection signal PSU is obtained. Comparator 3
9, 40 and the main control circuit 42 perform the same processing for the other terminal voltages VV and WV to obtain two position detection signals.

Then, the main control circuit 42 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 them. 6 to 11
Is 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 to adjust the output based on the speed command signal SV during the actual operation. Specifically, the main control circuit 42 detects a speed detection signal DV indicating the actual rotation speed of the brushless motor 21 on the basis of the position detection signal obtained by the calculation, and the detected voltage detection signal DV is generated by the voltage command signal generation circuit 43. Give to. Then, the voltage command signal generation circuit 43 compares the speed command signal SV and the speed detection signal DV with each other so that the difference between them becomes zero.
The duty signal of is supplied to the PWM signal generation circuit 44.

The PWM signal generating circuit 44 outputs a PWM signal (PWM carrier) having a duty corresponding to the duty signal given from the voltage command signal generating circuit 43 and gives it to the main control circuit 42. 42
Is, for example, the transistor 6 on the positive terminal side of the drive circuit 3.
Since the base signals given to 7 and 8 are modulated by the PWM signal, for example, the terminal voltage UV also becomes a pulse voltage as shown in FIG. 10A, and a phase signal obtained by comparing this with the reference voltage VR. Is also shown in Fig. 10 (b).
It becomes pulsed as shown by '. Therefore, it is not possible to obtain the position detection signal PSU shown in FIG. 9C from the phase signal DSU ′ shown in FIG. 10B. The same applies to the other terminal voltages VV and WV.

Therefore, in the prior art, in the enable signal generating circuit 45, as shown in FIG.
Enable signal SE in synchronization with WM signal (pulse signal)
The pulse signal of the phase signal DSU 'is determined only when the enable signal SE is generated. Therefore, as shown in FIG.
The same continuous phase signal DSU as in (b) can be obtained. The same applies to the other terminal voltages VV and WV.

[0019]

In the conventional configuration, the PW
When the carrier frequency of M (the frequency of the PWM signal) is increased, both the ON period and the OFF period of the terminal voltage UV (VV, WV) in the pulse form are shortened, and the phase signal DSU '
The pulse width of is also shortened. Therefore, the enable signal SE
As the main control circuit 42 that determines the presence / absence of a pulse of the phase signal DSU ′ only when the occurrence of the above occurs, high-speed determination processing is required, and the zero-cross point of the induced voltage is detected by the determination in a short time. This makes it difficult to detect the position detection signal.

Further, the PWM from the PWM signal generation circuit 44
Since the enable generation circuit 45 that generates the enable signal SE based on the signal is composed of a large number of electronic components such as ICs, the circuit becomes large and the cost becomes high.

The present invention has been made in view of the above circumstances, and an object thereof is to easily obtain a position detection signal even if pulse width modulation is performed at a high frequency, and to achieve miniaturization. It is an object of the present invention to provide a brushless motor drive device that can reduce the cost.

[0022]

According to another aspect of the present invention, there is provided a drive device for a brushless motor, the detection device detecting a terminal voltage of a stator winding of a plurality of phases of the brushless motor, and delaying the detection voltage of the detection device. And a reference voltage generating means for generating a reference voltage, and a comparing means for comparing the reference voltage from the reference voltage generating means with the delay detection voltage from the delay means. A control means for obtaining a position detection signal from the signal and outputting an energization timing signal based on the position detection signal and a pulse width modulation signal for output adjustment is provided, and the stator winding is based on the energization timing signal from the control means. An output means for energizing the line is provided, and the delay means is configured such that the rising characteristic is faster than the cycle of the carrier frequency of the pulse width modulation and the falling characteristic is the fixed frequency. Where be configured to be slower than the period of early and the carrier frequency than the period of the commutation frequency of switching the energization of the child winding has a feature.

According to another aspect of the present invention, there is provided a brushless motor driving device, which is provided with detecting means for detecting terminal voltages of stator windings of a plurality of phases of the brushless motor, and with reference voltage generating means for generating a reference voltage. Comparing means for comparing the reference voltage from the reference voltage generating means with the detected voltage from the detecting means is provided, delay means for delaying the signal from the comparing means is provided, and the position detection signal is provided by the delay signal from the delay means. Control means for outputting an energization timing signal based on this position detection signal and a pulse width modulation signal for output adjustment, and energizing the stator winding based on the energization timing signal from this control means. An output means is provided to connect the delay means with a rising characteristic earlier than a cycle of the carrier frequency of the pulse width modulation and a falling characteristic to the stator winding. When configured to be slower than the period of early and the carrier frequency than the period of the commutation frequency switches to have the features.

In this case, the control means may be configured to correct the delay generated by the delay means when obtaining the position detection signal (claim 3).

[0025]

According to the brushless motor driving device of the present invention, since the detection voltage detected by the detection means is delayed by the delay means, the delay detection voltage from the delay means is not pulsed but continuous. It becomes a waveform, and the signal from the comparison means also becomes a continuous square wave. Therefore, since the signal input to the control means becomes a square wave, the control means does not need to include an enable signal generation circuit unlike the conventional case, and even if the carrier frequency of the pulse width control is high, it becomes high. There is no need to perform speed determination processing.

According to the brushless motor driving device of the second aspect, since the signal from the comparison means is delayed by the delay means, the delayed signal from the delay means does not have a pulse shape but has a continuous waveform. Therefore, since the signals input to the control means are continuous, the same result as in claim 1 is obtained. In this case, if the delay generated by the delay means is corrected by the control means, an accurate position detection signal can be obtained.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.
As described with reference to FIG. 5, in this embodiment,
The same parts as those of the conventional example shown in FIGS. 8 to 10 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

That is, in FIG. 1, the control circuit 46 serving as the control means includes a main control circuit 42 and a voltage command signal generation circuit 43.
And a PWM signal generation circuit 44, and unlike the conventional control circuit 41, the enable signal generation circuit 45 is not provided.

The delay means 47 is composed of three delay circuits 48 to 50. These delay circuits 48, 49
And 50, the input terminals are connected to the detection terminals 30, 31 and 32 of the detection circuit 23, respectively, and the output terminals are connected to the non-inverting input terminals (+) of the comparators 38, 39 and 40, respectively. .

The delay circuits 48 to 50 have the same structure, and the delay circuit 48 will be described below with reference to FIGS. 4 and 5.
Will be described on behalf of. Input terminal 48a and output terminal 4
8b and a diode 48c in the forward direction and a resistor 4
The series circuit of 8d is connected, and the cathode of the diode 48c is grounded via the parallel circuit of the capacitor 48e and the resistor 48f.

This delay circuit 48 outputs a pulse-like input signal which is wetted in FIG. 5A, and an output signal having delay characteristics of a rising time Ta and a falling time Tb as shown in FIG. 5B. The rising time Ta is PW
It is set to be smaller than the cycle of the carrier frequency of M, and the fall time Tb is smaller than the cycle of the commutation frequency for switching the energization of the stator windings 22U to 22W and larger than the cycle of the PWM carrier frequency. Is set to.

Next, the operation of this embodiment will be described with reference to FIGS. 2 and 3. Now, the terminal voltage UV shown in FIG.
Will be described on behalf of. That is, conventionally, as shown in FIG. 3A, the comparator 38 substantially compares the pulsed terminal voltage UV with the reference voltage VR.

However, in this embodiment, since the detection voltage UVa becomes the delayed detection voltage delayed by the delay circuit 38, the comparator 38 is substantially the same as that shown in FIG.
As shown by, the reference voltage VR is compared with the terminal voltage UV 'having the delay characteristics on the rising and falling edges.

In this case, the terminal voltage UV 'input to the comparator 38 is supplied by the delay circuit 48 as described above.
The pulse at the terminal voltage UV has a rising characteristic faster than the carrier frequency of PWM (the rising time Ta is smaller than the cycle of the carrier frequency), and the falling characteristic has a stator winding 22U.
To 22 W faster than the commutation frequency of energization (fall time T
Since b is smaller than the cycle of the carrier frequency and slower than the carrier frequency (fall time Tb is larger than the cycle of the commutation frequency), the result is continuous rather than pulsed. It becomes a typical delay detection voltage.

Therefore, in the comparator 38, the reference voltage V
The terminal voltage UV 'compared with R has a continuous waveform,
The output signal from the comparator 48 is a rectangular wave phase signal DSU, as shown in FIG. The above description is for the terminal voltage UV, but the same operation is performed by the delay circuits 49 and 50 for the other terminal voltages VV and WV.

Incidentally, for example, the terminal voltage UV 'to be compared with the reference voltage VR by the comparator 38 is the terminal voltage UV delayed by the delay circuit 48, and therefore, at the falling time of the terminal voltage UV'. It is also possible to cause a delay so as to cross the reference voltage VR in the delay portion. However, the delay is about one pulse of the PWM carrier frequency, and considering that the carrier frequency is sufficiently higher than the commutation frequency, the delay is practically no problem. This also applies to the other delay circuits 39 and 40.

As described above, according to this embodiment, the detection signals UVa, VVa, and WVa from the detection circuit 23 are delayed by the delay circuits 38, 39, and 40, so that the main control circuit 42 is provided with a conventional signal. Unlike the pulsed phase signal like this, I tried to give a continuous signal,
The main control circuit 42 only needs to make a theoretical judgment as shown in FIG. 9, and therefore, the position detection signal can be obtained more easily than in the conventional case.

Moreover, from the above, it is not necessary to provide the enable signal generating circuit 45 as in the prior art, and it is sufficient to provide the delay circuits 48 to 50 having a simple structure.
As a whole, the size can be reduced and the cost can be reduced.

6 and 7 show a second embodiment of the present invention, in which the same parts as those in the first embodiment are designated by the same reference numerals. That is, in FIG. 6, the difference from FIG. 1 is that the delay circuits 48, 49 and 50 are interposed between the output terminals of the comparators 38, 39 and 40 and the input ports of the main control circuit 42.

Considering, for example, the case of the comparator 38, the output signal of the comparator 38 is a pulse-like phase signal DSU 'similar to the conventional one, as shown in FIG. By being delayed by the delay circuit 48, a continuous phase signal DSUa is obtained, as shown in FIG. 7B. Therefore, a threshold SL smaller than the lowest delay level LL of the phase signal DSUa is set in the main control circuit 42, and the threshold SL and the phase signal DSUa are set.
Comparing with, as shown in FIG. 7 (c), the phase signal DS
Ua 'can be obtained.

Therefore, unlike the conventional phase signal DSU ', the phase signal DSUa' is not a pulse-shaped one but a rectangular wave-shaped one, so that the same effect as that of the first embodiment can be obtained. The effects of the other delay circuits 49 and 50 are similar.

In this case, the phase signal DSUa 'is as shown in FIG.
The original phase signal DSU shown in (d) causes a delay time Tx, but this is not a problem because the carrier frequency of PWM is generally high in practice. . However, when the PWM carrier frequency is set to a relatively low frequency, the pulse width of the PWP signal becomes the set constant and the delay time Tx also becomes constant, so the main control circuit 42. It is possible to correct the delay time Tx when the position detection signal is obtained by calculation based on the phase signal DSUa ′ by means of this. A detection signal can be obtained.

The present invention is not limited to the embodiments described above and shown in the drawings. For example, a photocoupler having a delay characteristic may be used as the delay means.
It is needless to say that the comparison means may be functionally configured as a part of the control means, and may be appropriately modified and implemented without departing from the scope of the invention.

[0044]

Since the present invention is as described above,
It has the following effects. According to the brushless motor driving device of the present invention, the detection signal from the detection means or the signal from the comparison means is delayed by the delay means, so that the control means has a conventional pulse signal. Contrary to the above, a continuous signal is input, so that the control means can easily obtain the position detection signal without performing the high speed judgment processing, and further, the enable signal generation as in the conventional case. Since it is not necessary to provide a circuit, miniaturization can be achieved and cost can be reduced. Further, according to the brushless motor drive device of the third aspect, the control means is made to correct the delay by the delay means, so that an accurate position detection signal can be obtained.

[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 an enlarged waveform diagram of each part.

FIG. 4 is a configuration diagram of a delay circuit.

FIG. 5 is a waveform diagram of each part.

FIG. 6 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

[Figure 7] Waveform diagram of each part

FIG. 8 is a view corresponding to FIG. 1 of a conventional example.

FIG. 9 is an explanatory diagram of a principle for obtaining a position detection signal.

FIG. 10 is a waveform diagram of each part.

[Explanation of symbols]

In the drawing, 3 is a drive circuit (output means), 21 is a brushless motor, 22 is a stator, 22U to 22W are stator windings, 23 is a voltage dividing circuit (detecting means), 33 is a reference voltage generating circuit (reference voltage). Generating means), 37 comparing means, 38 to 40 comparators, 42 seed control circuit, 43 voltage command signal generating circuit, 44 PWM signal generating circuit, 46 control circuit (control means), 47 delay means , 48 to 50 denote delay circuits.

Claims (3)

[Claims] 1. A detection means for detecting terminal voltages of a plurality of phases of stator windings of a brushless motor, a delay means for delaying a detection voltage of the detection means, a reference voltage generation means for generating a reference voltage, and Comparison means for comparing the reference voltage from the reference voltage generation means with the delay detection voltage from the delay means, and a position detection signal obtained from the signal from the comparison means, and the position detection signal and pulse width modulation for output adjustment Control means for outputting an energization timing signal based on the signal,
Output means for energizing the stator winding based on an energization timing signal from the control means, wherein the delay means has a rising characteristic earlier than a cycle of a carrier frequency of the pulse width modulation and a falling characteristic. A drive device for a brushless motor, characterized in that the characteristic is configured to be faster than a cycle of a commutation frequency for switching energization to the stator winding and slower than a cycle of the carrier frequency. 2. 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 reference voltage from the reference voltage generating means and the detecting means. Comparing means for comparing the detected voltage with the detection voltage, the delay means for delaying the signal from the comparing means, the position detection signal by the delay signal from the delay means, and the position detection signal and the pulse width modulation for output adjustment. A control means for outputting an energization timing signal based on the signal, and an output means for energizing the stator winding based on the energization timing signal from the control means. The period of the carrier frequency of the pulse width modulation is faster, and the falling characteristic is earlier than the period of the commutation frequency for switching the energization to the stator winding and the period of the carrier frequency. A drive device for a brushless motor, which is configured to be slower. 3. The brushless motor drive device according to claim 2, wherein the control means is configured to correct the delay generated by the delay means when the position detection signal is obtained.