JPH06351280A - Phase current detector for motor - Google Patents

Abstract

PURPOSE:To allow detection of the phase current of a motor through a simple constitution. CONSTITUTION:A driver 21 comprises an inverter circuit 27 for feeding drive signals to phases U, V, W of coils 23, 24, 25 and an inverter circuit 27 comprises six transistors Q1, Q2, Q3, Q4, Q5, Q6. The transistors Q1, Q2, Q3 have collectors connected with the positive pole of a DC power supply 28 and emitters connected with the collectors of the transistors Q4, Q5, Q6 having emitters connected through phase current detecting resistors Ru, Rv, Rw with the negative pole of the DC power supply 28. Voltage signal at the joints of the emitters of the transistors Q4, Q5, Q6 and the resistors Ru, Rv, Rw are fed to phase current detection circuits 34, 35, 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase current detecting device for motors such as induction motors, synchronous motors and DC brushless motors.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting a phase current of a motor, a method in which a resistance for current detection is provided in each phase or a hall current sensor is used has been the mainstream.

For example, there is a circuit shown in FIG. 6 as a circuit in which a resistance for current detection is provided in each phase.

This motor 2 has three phases, U phase and V phase.
3 and W-phase drive signals Iu, Iv, Iw are supplied.
A stator 6 having coils 3, 4, 5 of a book is provided. The motor 2 also includes a rotor (not shown) having a pair of magnetic poles made of permanent magnets. Drive circuit 1 to coil 3,
The signal lines 9u, 9v, and 9w for supplying the drive signals Iu, Iv, and Iw to 4 and 5 are respectively connected to a resistor 1 for detecting a phase current.
0u, 10v, 10w are provided. Resistance 10u, 10
In v and 10w, the currents of the U-phase, V-phase, and W-phase drive signals are converted into voltages, and the DC amplification circuits 11 and 1 are respectively generated.
2 and 13, via the phase current detection signals Iua, Iva,
Iwa is output.

In the drive circuit 1, the coils 3, 4 and 5 have the U
The inverter circuit 7 is provided with the inverter circuits 7 for supplying the drive signals Iu, Iv, and Iw for the V-phase, the V-phase, and the W-phase, respectively.
, The six transistors Q1, Q2, Q3, Q
4, Q5, Q6 are provided. Transistors Q1 to Q6
Is connected to the DC power supply 8. Transistors Q1, Q4;
The drive signals Iu, Iv, and Iw of the U-phase, V-phase, and W-phase are transmitted from the connection points of Q2, Q5;
It is output to 9v and 9w, respectively.

The detection outputs from the DC amplification circuits 11, 12 and 13 are input to a control circuit 100 which controls the motor current based on the detection output and a predetermined current command value. So as to match the predetermined current command value, the transistor Q1 of the inverter circuit.
Amplitude-modulated pulse signal is generated to drive Q6 on / off.

However, in this circuit, it is necessary to provide reference points at the resistors 10u, 10v, and 10w for each phase, so that the wiring becomes complicated, and the amplifier circuit 11 that also serves as insulation for each phase is provided. , 12, 13 must be provided, which causes a problem of high cost.

The resistors 10u, 10v, 10 for each phase are also provided.
If a Hall current sensor is used instead of w, no isolation is required, but the sensor is expensive and there is a problem with offset voltage.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned technical problems and to provide one capable of detecting a phase current with a simple structure.

[0010]

SUMMARY OF THE INVENTION A motor phase current detecting apparatus according to the present invention includes a plurality of switch elements for supplying driving power to coils for each phase of a motor having coils of a plurality of phases, and the plurality of switch elements. A drive unit for individually turning on / off the switch elements, a current detection resistor connected in series to each of the plurality of switch elements, and a terminal voltage of the current detection resistor, Switch element of ON /
A current detecting means for detecting in synchronization with the off driving is provided.

[0011]

Operation According to the present invention, the driving power is supplied to the coils of the plurality of phases of the motor by the plurality of switch elements. The plurality of switch elements are individually turned on / off by the driving unit. A current detection resistor is connected in series to each of the plurality of switch elements, and the voltage across the terminals of the current detection resistor is synchronized by the current detection means with ON / OFF drive of the plurality of switch elements by the drive unit. Then detected.

From the detected phase current, the number of rotations of the motor, the torque of the motor, the rotation angle of the motor can be estimated, and in the case of an induction motor, the torque, the exciting current, etc. can be controlled.

[0013]

1 is a circuit diagram showing the electrical construction of a drive unit 21 for a DC brushless motor according to an embodiment of the present invention.
The motor 22 of the present embodiment is, for example, three-phase and includes a stator 26 having three coils 23, 24 and 25,
The coils 23, 24, 25 of the respective phases are excited by the U-phase, V-phase and W-phase drive signals Iu, Iv, Iw from the drive unit 21. The motor 22 includes a rotor (not shown) including a permanent magnet having a pair of magnetic poles.

The drive unit 21 includes coils 23, 24 and 25.
Is provided with an inverter circuit 27 for supplying the U-phase, V-phase and W-phase drive signals, respectively, and the inverter circuit 27 has six transistors Q1, Q2, Q3, Q4, Q5, Q.
6 are provided and each transistor Q1, Q2, Q3, Q
4, Q5, Q6 in parallel with diodes D1, D2, D
3, D4, D5, D6 are provided. Transistor Q
The collectors of 1, Q2 and Q3 are connected to the positive electrode of the DC power supply 28, and the emitters of the transistors Q1, Q2 and Q3 are
It is connected to the collectors of the transistors Q4, Q5, Q6, respectively. The emitters of the transistors Q4, Q5, Q6 are phase current detection resistors (hereinafter simply referred to as resistors) Ru,
It is connected to the negative electrode of the DC power supply 28 via Rv and Rw, respectively. Transistors Q1, Q4; Q2, Q5; Q
The U-phase, W-phase, and V-phase drive signals Iu, Iv, and Iw are extracted from the connection points of Q3 and Q6.

The driving device 21 corresponds to a predetermined reference speed of the motor 22, and has a reference speed signal input from the outside and a phase current for each phase of the motor 22 detected as described later. Therefore, a motor drive voltage signal generation circuit (hereinafter referred to as a signal generation circuit) 29 for generating drive voltage signals Su, Sv, Sw for driving the motor 22 is provided. The drive voltage signals Su, Sv, Sw from the signal generating circuit 29
Is input to an amplitude modulation (hereinafter referred to as PWM) circuit 30, and a triangular wave having a predetermined frequency and a predetermined amplitude and a drive voltage signal S
PWM for each phase by comparing u, Sv, Sw
A modulated signal is generated. The amplitude modulation signal for each phase is
Transistors Q1, Q4; Q2, Q5; Q for each phase
The signals are input to base drive circuits 31, 32 and 33 which generate drive control signals input to the bases of Q3 and Q6, respectively.

In this embodiment, the transistors Q4, Q
The voltage signals at the connection points between the emitters of Q5 and Q6 and the resistors Ru, Rv, and Rw are the phase current detection circuits 34, 35, and
36 respectively. Each phase current detection circuit 34, 3
LPFs 5 and 36, to which the voltage signals from the resistors Ru, Rv, and Rw are input, remove high frequency components.
(Low-pass filter) 37, 38, 39 and each LPF 3
DC amplifier 40 for amplifying the voltage signal from 7 to 39,
41 and 42 and a sample-hold circuit 4 for sample-holding the voltage signals from the DC amplifiers 40, 41 and 42.
3, 44, 45. Sample hold circuit 43
The PWM modulation signals from the PWM circuit 30 are used as the sampling signals of ~ 45. The output from each sample-hold circuit 43, 44, 45 is the phase current detection signal Iu.
a, Iva, and Iwa.

FIG. 2 shows resistors Ru, Rv, Rw of this embodiment.
FIG. 3 is a circuit diagram illustrating a phase current detection operation according to FIG.
[Fig. 3] is a waveform diagram illustrating this phase current detection operation. Figure 3
(1) shows the U-phase drive voltage signal Su from the signal generation circuit 29 and the triangular wave generated in the PWM circuit 30. 3 (2) shows a U-phase PWM modulation signal from the PWM circuit 30, FIG. 3 (3) shows a terminal voltage waveform of the resistor Ru, and FIG. 3 (4) shows the U-phase PWM.
FIG. 3 (5) shows the phase current detection signal Iua from the sample hold circuit 43, and FIG. 3 (6) shows the sampling timing and hold timing determined based on the modulation signal. The electrical angle relating to the drive voltage waveform of the motor 22 is shown.

The phase current detection operation will be described below by focusing on the U phase, but the same detection operation is performed for the other V and W phases.

The electrical angle 0 to π (ra in FIG. 3 (6)
In the period of d), the PWM circuit 30 shown in FIG.
The ON period of the transistor Q1 when the PWM modulation signal from is at a high level is longer than the ON period of the transistor Q4. When the transistor Q1 is on, the drive signal Iu
2 flows in the direction of arrow i1 in FIG. Figure 3 (2)
When the PWM modulation signal shown in is low level, the transistor Q1 is turned off. Immediately after the transistor Q1 is turned off and the transistor Q4 is turned on, the current of the drive signal Iu flows in the direction of the arrow i1 due to the influence of the motor winding inductance, so that the diode D4 becomes conductive.
The current at this time flows through the resistor Ru and the diode D4 in the arrow i4 direction.

Further, the electrical angle π to 2π in FIG. 3 (6)
In the period (rad), the on period of the transistor Q4 is longer than the on period of the transistor Q1. When the transistor Q4 is on, the current as the drive signal Iu is as shown in FIG.
Flows in the direction of arrow i2. The transistor Q4 turns off,
In the period immediately after the transistor Q1 is turned on, the current of the drive signal Iu flows in the direction of arrow i2, which is the direction that has been flowing so far, as in the above case. At this time, the current is blocked by the transistor Q4 and the diode D4 and does not flow through the resistor Ru. At this time, the diode D1 becomes conductive, and the current passes through the diode D1 in the arrow i3 direction.

Therefore, the current flows through the resistor Ru only when the transistor Q1 is off and the transistor Q4.
When is on. Due to this current, a terminal voltage as shown in FIG. 3C is generated across the resistor Ru. The instantaneous value of the voltage between the terminals is proportional to the value of the current that is the drive signal Iu flowing through the U-phase coil 23.

Therefore, when the PWM modulation signal shown in FIG. 3 (2) is low, the sample-hold circuit 43 samples the terminal voltage of the resistor Ru, and the PWM modulation signal is high level. During the period, the sampled terminal voltage is held. The timing of such a sampling / hold period is shown in FIG.
It is shown in (4). By such sampling / holding operation, the phase current detection signal I shown in FIG.
u is output from the sample hold circuit 43. The phase current detection operation can detect a phase current in the coil 23 in both positive and negative directions, and can detect the phase current in the coil 23 with high accuracy.

As described above, the present embodiment can detect the phase currents in the coils 23, 24 and 25 with a simple structure without using a hole current sensor or the like.

In the present embodiment, the frequency of the PWM modulation signal is increased by increasing the frequency of the triangular wave generated inside the PWM circuit 30 to improve the detection accuracy of the phase current. May be.

FIG. 4 is a circuit diagram showing an application example of the driving device 21 shown in FIG. In this circuit example, the motor 2
2. A magnetic pole sensor 47 that detects a change in the magnetic pole due to the rotation of the rotor composed of the permanent magnet of FIG. 2 and outputs a detection signal that changes corresponding to the change in the magnetic pole, and a motor detected by the magnetic pole sensor 47. There is provided a speed sensor 48 that outputs a rotation speed signal that changes based on a change in the magnetic pole due to the rotation of 22. The signal generating circuit 29 is connected to the motor 22.
Speed command signal amplifier (hereinafter referred to as amplifier) 46 to which a speed command signal from the outside corresponding to the reference rotation speed of is input.
And the multipliers 49, 50, 51 for each phase to which the speed command signals from the amplifier 46 are respectively input.

The speed sensor 48 is provided in the amplifier 46.
The rotation speed signal from is converted into a voltage level corresponding to the change of the rotation speed signal by the speed converter 52, and the obtained voltage signal is input, and the voltage signal is added / subtracted to / from the speed command signal to correspond to the calculation result. A level signal or voltage is output. Based on the signals from the magnetic pole sensor 47 and the speed sensor 48, each of the multipliers 49, 50, 51 is
A current distribution signal from a current distribution signal generator 53 that generates a timing signal for current application for each ancestor is input. The speed signals from the multipliers 49 to 51 are supplied to the current amplifiers 54 and 5 respectively.
5 and 56 respectively. Each current amplifier 54-5
The output of 6 is input to the PWM circuit 30.

Further, in this configuration example, the phase current detecting resistors are provided only in the U phase and the W phase.

Therefore, the amplifier circuit 57 is used as the phase current detection circuit 35 shown in FIG. 1 corresponding to the V phase. That is, the amplifier circuit 57 calculates Iv from Iv =-(Iu + Iw) because Iu + Iv + Iw = 0.

The outputs of the phase current detection circuits 34 to 36 are input to the corresponding current amplifiers 54 to 56, and the multipliers 49 to 5 are respectively provided in the current amplifiers 54 to 56.
It is added to or subtracted from the output of 1. The outputs of the phase current detection circuits 34 and 36 are input to the amplifier 57 corresponding to the V-phase phase current detection circuit 35.

The above-described phase current detection operation can also be performed by the driving device 21 having such a configuration example.

FIG. 5 shows a driving device 2 according to another embodiment of the present invention.
It is a circuit diagram which shows the structure of 1a. This embodiment is similar to the embodiment shown in FIG. 1 described above, and corresponding parts are designated by the same reference numerals.

The feature of this embodiment is that the resistor R for detecting the phase current is used.
That is, u, Rv, and Rw are provided in the collectors of the transistors Q1, Q2, and Q3, respectively. In the present embodiment, the timing for detecting the phase current as described above is when the transistor Q1 is on and the transistor Q4 is off. While the transistor Q1 is on and the transistor Q4 is off, the voltage across the terminals of the resistors Ru, Rv, Rw is sampled, and during the period when the transistor Q4 is on, the sampled voltage between the terminals is held.

The same effects as those described in the above-described embodiments can be achieved also by the embodiment having such a configuration and the phase current detecting operation.

The detected phase current is, for example, in addition to the above-mentioned usage. The number of rotations of the motor, the torque of the motor, the rotation angle of the motor, etc. can be estimated.

[0035]

As described above, according to the present invention, the driving power is supplied to the coils of the plurality of phases of the motor by the plurality of switch elements. The switch elements are
It is individually turned on / off by the driving unit. A current detection resistor is connected in series to each of the plurality of switch elements, and the voltage across the terminals of the current detection resistor is synchronized by the current detection means with ON / OFF drive of the plurality of switch elements by the drive unit. Then detected. In this case, since no expensive element is used, it can be realized at low cost.

Thus, the detected phase current can be used to estimate the rotation speed of the motor, the torque of the motor, the rotation angle of the motor, and in the case of an induction motor, the torque, the exciting current, etc. can be controlled.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a motor driving device 21 according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a phase current detection operation by resistors Ru, Rv, and Rw of the present embodiment.

FIG. 3 is a waveform diagram illustrating a phase current detection operation.

FIG. 4 is a circuit diagram showing an application example of a driving device 21 shown in FIG.

FIG. 5 is a circuit diagram showing a configuration of a drive device 21a according to another embodiment of the present invention.

FIG. 6 is a block diagram of a drive circuit 1 for a conventional motor.

[Explanation of symbols]

 21,21a Drive device 22 Motor 23,24,25 Coil 26 Stator 27 Inverter circuit 28 DC power supply 34,35,36 Phase current detection circuit Ru, Rv, Rw Phase current detection resistance

Claims (1)

[Claims] 1. A plurality of switch elements for supplying drive power to the coils for each phase of a motor having a plurality of phase coils, and a drive section for individually turning on / off the plurality of switch elements. , A current detection resistor connected in series to each of the plurality of switch elements and a voltage between terminals of the current detection resistor are detected in synchronization with ON / OFF driving of the plurality of switch elements by the drive unit. A motor phase current detecting device comprising a current detecting means.