JPH0646879B2 - Brushless motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a brushless motor drive device in which a sensor is omitted and a magnetic pole position of a rotor is detected by a terminal voltage of a motor.

(B) Prior art Fig. 5 to Fig. 5 show a conventional example of this type of brushless motor drive device.
This will be described with reference to FIG.

In FIG. 5, reference numeral 1 is an inverter formed by connecting six transistors T1 to T6 in a three-phase bridge connection, and 2 is a brushless motor in which an armature winding is star-connected to a neutral point, 3
Is a position detection circuit for detecting the magnetic pole position of the rotor, 4 is an inverter control circuit, and 5 is a speed control circuit.

Assuming that the induced voltage generated in each phase of the star-connected armature winding is a symmetrical three-phase AC voltage, the brushless motor 2
Is normally driven, the voltage waveform of each phase is
As shown in (a). The phase excitation switching phase that maximizes the output torque of the brushless motor 2 is the phase at which the corresponding two phase voltages are equal (control lead angle = 0), and the switching timing of each phase excitation at this time is shown in FIG. As shown in b). That is, each transistor T1 that constitutes the inverter 1
~ T6 is turned on / off at the timing shown in Fig. 6 (b),
By exciting each phase of the brushless motor 2, the brushless motor 2 can be efficiently driven with the maximum output torque.

The position detection circuit 3 detects the phase excitation switching position for turning on / off the transistors T1 to T6. As shown in FIG. 7, the first-order lag filter 31 is used to detect the terminal voltages Va, Vb, and Vc.
° Phase-shifted and then phase-shifted three-phase voltage and neutral point voltage Vn obtained by star-connecting three resistors Rn to these three-phase voltages are compared by comparator 32, respectively, and position detection signal C1 Is configured to obtain ~ C3.

Inverter control circuit 4 based on these position detection signals C1 to C3
Then, if a signal for turning on / off each of the transistors T1 to T6 of the inverter 1 is produced and output as it is to the inverter 1 without passing through the speed control circuit 5, as shown in FIG. 6 (b), Transistors T1 to T at the timing shown
By turning 6 on / off, the brushless motor 2 can be driven with the maximum output torque. This brushless motor 2
In order to control the speed, the output of the inverter control circuit 4 is chopped by the output of the variable duty chopper signal generation circuit 51 of the speed control circuit 5 and added to the inverter 1 in the conventional example shown in FIG.

FIG. 8 is a waveform diagram showing the situation at this time. Chopping may be performed by setting an appropriate period of the ON period of each of the transistors T1 to T6. However, if chopping is performed for the entire period, the position detection circuit 3 can detect it. It becomes impossible.

Therefore, in this example, only the latter 60 ° period is chopped out of the 120 ° period in which the transistors T1 to T6 are turned on / off.

Also, when chopping one of the transistors,
The transistor of the corresponding arm is chopped in the opposite phase to stabilize the operation. For example, when the transistor T1 is turned off to perform chopping during the latter half 60 ° of the energization period, the armature winding U
The terminal voltage Va of the phase does not become 0 and exhibits an unstable value. In order to eliminate such a fluctuation of the terminal voltage Va and reliably switch the terminal voltage Va to 0 and E (V) during the chopping period, when the transistor T1 is turned off, the corresponding transistor T4 is turned on. This is the same when turning on the transistors T3 and T4 and chopping the transistor T4. When the transistor T4 during the chopping period is turned off, the corresponding transistor T1 is turned on.

As a result, the U-phase terminal voltage Va has a stable chopping waveform as shown in FIG. 8B, and the speed of the brushless motor 2 can be changed by changing the chopping duty.

However, in the above conventional device, the inverter 1
Each of the transistors T1 to T5 in the latter half of the 120 ° energization period
Since the 0 ° period must be chopped, the means for controlling the chopping of each of the transistors T1 to T6 becomes complicated, and the design of shifting the phase of the terminal voltage waveform of the inverter control circuit 4 by 90 ° becomes complicated. was there.

(C) Problems to be Solved by the Invention It is an object of the present invention to solve the above-mentioned conventional problems and provide a variable speed brushless motor drive device with easy circuit design without requiring complicated chopping control. And

(D) Means for Solving the Problems For this reason, the present invention detects the magnetic pole position of the rotor from the terminal voltage of the brushless motor, controls the inverter, and switches the phase excitation at the control advance angle of zero. In the apparatus, an inverter control unit that outputs a control signal for turning on each switching circuit of the inverter, a speed control unit that controls the rotation speed of the motor by performing a chopping process on the control signal, and a chopping process that is synchronized with the chopping process. Sample-hold means for sampling the terminal voltage when the processed control signal is on and holding the terminal voltage at the sampling voltage when the control signal is off; and an output of the sample-hold means. The magnetic pole position of the rotor is detected based on the signal and output to the inverter control means. It is characterized in further comprising a position detection means that.

(E) Action Chopping control is simplified by chopping all 120 ° energization periods when energizing each arm of the inverter. In addition, the magnetic pole position at this time, that is, the phase excitation switching position, is detected by inputting the chopped terminal voltage to the sample and hold circuit that is synchronized with the chopping frequency, and a waveform almost equal to that without chopping is obtained. It can be reliably detected based on the above.

(F) Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a DC brushless motor driving device according to an embodiment of the present invention. 5th in the figure
The same reference numerals as those in the figure indicate the same or corresponding portions, and the difference is that the configurations of the position detection circuit 3 and the speed control circuit 5 are changed and a sample hold circuit 6 is newly provided.

The speed control circuit 5 uses the transistors T1, T2, and T1 among the control signals output from the inverter control circuit 4 to the inverter 1.
By chopping only the signal output to T3 from the output of the chopper signal generation circuit 51, the brushless motor 2
Is configured to speed control.

The sample and hold circuit 6 synchronizes with the chopping frequency of the chopper circuit generating circuit 51, samples the terminal voltage when the transistors T1, T2, T3 are on, and holds it when it is off to restore the terminal voltage waveform. Then, it is configured to be taken out.

As shown in FIG. 2, the position detection circuit 3 extracts the neutral point voltage Vn from the terminal voltages Sva, Svb, Svc output from the sample hold circuit 6 via three resistors Rn star-connected, Are compared by a comparator 32, and the output thereof is added to a counter 33 and phase-shifted by 90 ° to extract the phase excitation switching position detection signals P ₁ , P ₂ , P ₃ .

With the above configuration, the inverter control circuit 4 is the position detection circuit 3
Based on the position detection signals P1, P2, and P3 from, the phase excitation control signal that switches at the control advance angle (= 0) is output as shown in FIG. 6 (b). The speed control circuit 5 uses the inverter 1 among the control signals output from the inverter control circuit 4.
Since only the signals applied to the transistors T1, T2, T3 on the upper side of the above are chopped for the entire period, they are ANDed with the chopping signal from the chipper signal generation circuit 51 and output to the inverter 1. On the other hand, of the control signals output from the inverter control circuit 4, the transistor T below the inverter 1
The signals applied to 4, T5 and T6 are output as they are.

As a result, a signal as shown in FIG. 3 (a) is applied to each of the transistors T1 to T6 of the inverter 1 to chop the current flowing through the three-phase armature winding. By the chopping operation of the inverter 1, the terminal voltages Va, Vb, Vc are also chopped as shown in, for example, FIG. 3 (b). The chopping voltage is input to the sample hold circuit 6 and synchronized with the chopping frequency. By carrying out sampling and holding, as shown in FIG. 3 (c), a terminal voltage Sva almost equal to that when no chopping is performed can be obtained.

Therefore, these terminal voltages Sva, Svb, Svc are supplied to the neutral point voltage Vn by the comparator 32 of the position detection circuit 3 shown in FIG.
And outputs signals C1 to C3 which are inverted each time they match and are output to the counter 33.

On the other hand, the counter 33 (for example, 33-1) outputs the phase excitation switching position detection signal P ₁ of the corresponding phase (for example, U phase) to the immediately preceding phase (W.
The counter (33-3) that processes the terminal voltage (Svc) of (Phase) starts counting the clock, and the comparator (32-
When a value three times as high as the input of the coincidence signal C1 from 1) is counted, the phase excitation switching position detection signal P ₂ of the next phase (V phase) is output.

That is, as shown in FIG. 3 (d), the coincidence signal C1 is output from the comparator 32-1. Assuming that the switching time from the U phase to the V phase is A (this time is known by the output P ₁ from the counter 33-3), from this time A the time B at which the terminal voltage Sva matches the neutral point voltage Vn (this The time until it is known by the coincidence signal C1) is just 30 ° in electrical angle. Therefore, from this time point A to B, the clock input at a constant cycle is counted by the counter 33 to obtain a value, and at the time point C which is three times the count value, the switching position to the next phase is set. By outputting the detection signal (P ₂ ), it is possible to calculate the excitation period of one phase (V phase), which is a period of 120 ° in electrical angle from time A to C.

Therefore, the phase excitation switching position detection signal from the position detection circuit 3
By inputting P ₁ .P ₃ to the inverter control circuit 4,
With the control lead angle = 0, an inverter control signal for switching the phase excitation can be obtained, and the brushless motor 2 can be driven with the maximum output torque.

At this time, by changing the duty cycle of the chopper signal output from the chopper signal generation circuit 51,
The brushless motor 2 can be controlled at a variable speed.

FIG. 4 is a circuit configuration diagram showing an example of the chopper signal generation circuit 51 for that purpose. The sawtooth wave 5A from the sawtooth wave generation circuit 511 and the set voltage 5B from the high speed setting device 512 are compared with the comparator 513.
By comparing with, the chopping pulse 5C having a duty compared with the set voltage 5B can be easily obtained.

As described above, since the speed control circuit 5 only needs to perform a simple chopping process on the base input signals of the transistors T1 to T3 as shown in FIG. 3 (a), the structure is extremely simple. Further, the three-phase terminal voltage can be reliably obtained by providing the sample hold circuit 6, and the phase excitation switching position can be accurately detected.

In the above embodiment, the hardware configuration is shown, but it goes without saying that a microcomputer including the speed control circuit 5 can be used to perform software processing.

(G) Effect of the Invention As described above, according to the present invention, the electric current when the control signal chopped by the sample hold means is turned on while chopping the current supplied to the armature winding during the entire conduction period. Since the terminal voltage of the subsidiary winding is sampled, the terminal voltage is held at the sampling voltage when the control signal is off, and the output signal from the sample-hold means is input to the position detecting means. A terminal voltage waveform almost equal to that in the case where it is not provided is obtained, an accurate excitation switching position can be detected, and chopping processing for speed control is simplified.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a DC brushless motor drive device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing an example of a position detection circuit used in the device, and FIG. Waveform diagram, FIG. 4 is a circuit configuration diagram showing an example of a chopper signal generation circuit used in the same device, FIG. 5 is a circuit configuration diagram of a conventional brushless motor drive device, and FIG. 6 is an inverter control circuit of the device. Waveform diagram for explaining the output signal, No. 7
FIG. 8 is a block diagram of the position detection circuit of the device, and FIG. 8 is a waveform diagram of each part of the device. 1 ... Inverter, 2 ... Brushless motor, 3 ... Position detection circuit, 4 ... Inverter control circuit, 5 ... Speed control circuit,
6 ... Sample and hold circuit, 31 ... Filter, 32 ... Comparator, 33 ... Counter, 51 ... Chopper signal generating circuit.

Claims (1)

[Claims] 1. In a brushless motor drive device for detecting a magnetic pole position of a rotor from a terminal voltage of a brushless motor to control an inverter, and performing phase excitation switching at a control advance angle of zero, control for turning on each switching circuit of the inverter. Inverter control means for outputting a signal, speed control means for controlling the rotation speed of the motor by chopping the control signal, and when the chopping-processed control signal is ON in synchronization with the chopping processing Sample-holding means for sampling the terminal voltage of, and holding the terminal voltage at the sampling voltage when the control signal is off, and detecting the magnetic pole position of the rotor based on the output signal of the sample-holding means. Position detecting means for outputting to the inverter control means. Brushless motor drive device.