JPH0678586A - Driving device for brushless dc motor - Google Patents

Abstract

PURPOSE:To provide a driver for a brushless DC motor in which an optimum efficiency of the motor can be realized by always correcting a commutation control signal to an optimum phase. CONSTITUTION:The driver for a brushless DC motor comprises a comparator 7 for comparing a motor current value received from motor current detecting means CT with a zero level value near zero to output a pulse signal each time the current value exceeds the zero level value. A microcomputer 5 has a pulse signal counter 8 for counting the number of pulse signals output from the comparator 7, a phase correction amount calculator 10 for calculating a phase correction amount phi of a commutation control signal in which the number of the pulse signals is made equal in an OFF period before and after an ON period based on the number of the pulse signals counted by the counter 8 in the OFF period in which an absolute value of a motor current becomes substantially zero before and after the ON period in which an absolute value of the motor current becomes a maximum value, and a second timer 12 for correcting a phase of the commutation control signal based of the correction amount phicalculated by the calculator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the relative position between a rotor and an armature winding based on the induced voltage induced in the armature winding of a brushless DC motor, and based on the detected relative position. The present invention relates to a brushless DC motor driving device that drives a brushless DC motor.

[0002]

2. Description of the Related Art Conventionally, as a drive circuit of this type, for example, a drive circuit as shown in FIG.
No. 144747 publication). This drive circuit includes six transistors Tr1 each having freewheeling diodes 36a-36f.
~ Tr6 is connected to a three-phase full bridge, power supply 32
Inverter circuit 31 connected to and the armature winding 3 connected in three phases fed by this inverter circuit 31
7a to 37c and a permanent magnet rotor 38, a brushless DC motor 33, an induced voltage detecting means 34 for detecting the position of the rotor 38 from the terminal voltage of the armature windings 37a to 37c, and this detecting means 34. Depending on the detected position of the rotor, the transistor Tr of the inverter circuit 31
The control unit 35 is configured to sequentially switch 1 to Tr6 and conduct them to synchronously rotate the rotor 38.

As shown in FIG. 6 (B), the induced voltage detecting means 34 comprises a resistor and a grounding capacitor, and is a primary type low-pass filter 3 for removing harmonics from the terminal voltage.
9a to 39c, a coupling capacitor and a grounding resistor for removing a DC component from each output signal, and a non-inverting input terminal + for receiving an output from each coupling capacitor, and a resistor 40 having a three-phase Y connection for receiving the output. It is composed of comparators 42a to 42c receiving from the neutral point 41 to the inverting input terminal-.

The terminal voltages of the three armature windings 37a to 37c are 12 as shown by 43-a, 43-b and 43-c in FIG.
It is a three-phase balanced voltage with a phase shift of 0 ° (electrical angle), and harmonics and DC components are removed by passing through the low-pass filters 39a to 39c and the coupling capacitor, and the terminal voltage, that is, the fundamental frequency of motor operation. In the predetermined range of, the phase is delayed by about 90 ° with respect to the terminal voltage,
It becomes a triangular wave signal as shown by 44-a to 44-c in FIG. These triangular wave signals are superimposed at the neutral point 41 and become a signal as indicated by 45 in FIG. 7 and are input to the-terminal of each comparator, and the comparators 42a to 42c are connected to this signal 45 and the + terminal. The magnitudes of the input signals 44-a to 44-c are compared and the position signals as shown by 46-a to 46-c in FIG. 7 are output. Next, the control means 35 receives this position signal and outputs a commutation control signal as indicated by 47 in FIG. 7 for sequentially turning on and off the transistors Tr1 to Tr6 of the inverter circuit 31 at the rising or falling edge thereof. Thus, the rotor 38 of the brushless DC motor 33 is synchronously rotated.

However, since the low-pass filter 39 and the direct-current component removal filter composed of the coupling capacitor and the resistor which constitute the induced voltage detecting means 34 of the above-mentioned conventional drive circuit are not flat in frequency characteristic, the phase of the output signal is the motor 33. Exactly 9 for the input signal over all operating frequencies of
Output signals 44-a to 44-c, not 0 ° delay
Is exactly 90 ° behind the input signal (terminal voltage).
The phase of the triangular wave signal indicated by the solid line is advanced as shown by the broken line triangular wave or delayed as shown by the one-dot chain line triangular wave. Therefore, the phase signals of the position signals 46-a to 46-c and the commutation control signal 47 output from the control means 35 to the inverter circuit 31 are also advanced or delayed, and the brushless DC motor 33 is operated with optimum efficiency. There is a problem that you can not.

Therefore, in order to solve the above problem, the output signal of the induced voltage detecting means 34 with respect to the input signal (terminal voltage of the armature winding) to the induced voltage detecting means 34 at each frequency obtained in advance by experiments. A memory that stores the amount of phase shift of the (position signal), a first timer that measures the cycle of the position signal to obtain the frequency, and the first timer.
A second timer that counts a time corresponding to the amount of phase shift stored in the memory, which corresponds to the frequency obtained from the period measured by the timer, and the phase shift direction is limited to the time measured by the second timer. In the opposite direction to the above commutation control signal 4
There is a system in which the phase shift of the commutation control signal due to the phase shift between the input signal and the output signal of the induced voltage detecting means 34 is eliminated by shifting the phase of No.

[0007]

However, since the phase shift is affected not only by the frequency but also by the magnitude of the load on the motor, as described above, the commutation control is performed according to the frequency. Even if the phase of the signal is corrected, there is a problem that the optimum efficiency of the motor cannot be realized and the optimum phase cannot be set during the operation of the motor depending on the magnitude of the load applied to the motor.

Therefore, an object of the present invention is to provide a brushless DC motor which can always correct the commutation control signal to the optimum phase even if the magnitude of the load applied to the motor changes during the operation of the motor and realize the optimum efficiency of the motor. It is to provide a drive device.

[0009]

In order to achieve the above object, a brushless DC motor driving device of the present invention is provided with a terminal of the armature winding of a brushless DC motor (1) having a rotor and an armature winding. Position detection means (2) for detecting the position of the rotor from the voltage, an inverter circuit (3), and commutation control to the inverter circuit (3) according to a position detection signal from the position detection means (2). A signal is output to sequentially switch the flow state of the inverter circuit (3) to switch the motor.
In a brushless DC motor drive device including a control means (5) for driving (1), a motor current detection means (CT) for detecting a motor current flowing from the inverter circuit (3) to the motor (1). , The motor current detection means (CT)
And a comparator (7) for comparing the motor current value received from the motor controller with a zero level value close to zero and outputting a pulse signal each time the motor current value exceeds the zero level value. The control means (5) includes pulse signal counting means (8) for counting the number of pulse signals output from the comparator (7), and the motor.
The pulse counted by the pulse signal counting means in the off period in which the absolute value of the motor current should be substantially zero before and after the on period in which the absolute value of the motor current to the armature winding of (1) takes the maximum value. Phase correction amount calculation means (10) for calculating the phase correction amount of the commutation control signal that equalizes the number of pulse signals in the off periods before and after the on period based on the number of signals, and the phase correction amount calculation means ( Phase correction means for correcting the phase of the commutation control signal based on the phase correction amount calculated in 10).
(12) is provided.

[0010]

As shown in FIG. 2 (A), the present inventor has found that the motor current to the armature winding has a positive maximum value during the ON period (the period corresponding to modes 1, 2 and modes 4, 5). )In front of the,
If the number of times the motor current exceeds the zero level value (7 times) is greater than the number of times the motor current exceeds the zero level value (2 times) after the on period, the motor is operated at optimum efficiency. The phase of the motor current is advanced with respect to the optimum phase of the motor current that can be operated. On the other hand, as shown in FIG. 2 (C), the motor current has a zero level value before the on period. If the number of times (2 times) is less than the number of times the motor current exceeds the zero level value (7 times) after the ON period, the phase of the motor current with respect to the optimum phase of the motor current It was possible to confirm by experiment that the time was delayed.

That is, as shown in FIG. 2B, the present inventor has found that the number of times the motor current exceeds the zero level value before the on period and the motor current is zero after the on period. If the number of times the level value is exceeded is equal, that is, the number of pulse signals counted during the OFF period is the OFF state before and after the ON period when the absolute value of the current to the armature winding of the motor takes the maximum value. It has been confirmed that the phase of the motor current becomes the optimum phase when the periods are equal.

According to the drive apparatus of the present invention, the comparator compares the motor current value received from the motor current detecting means with a zero level value close to zero, and the motor current value is zero level. A pulse signal is output each time the value is exceeded. Then, the pulse signal counting means counts the number of pulse signals output from the comparator, and the phase correction amount calculating means counts the pulse signals based on the number of pulse signals counted in the off period before and after the on period. A phase correction amount of the commutation control signal that equalizes the number of signals in the off period before and after the on period is calculated. Then, the phase correction means corrects the phase of the commutation control signal based on the phase correction amount.

Therefore, according to the present invention, unlike the conventional example in which only a predetermined phase correction corresponding to the frequency is performed, the load variation to the motor is always dealt with according to the actual motor current. The phase of the motor current can be corrected to the optimum phase.

Therefore, according to the present invention, the commutation control signal can always be corrected to the optimum phase even when the magnitude of the load applied to the motor changes during motor operation, and the optimum efficiency of the motor can be realized.

[0015]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

In the brushless DC motor driving device of this embodiment, the terminal voltage of the armature winding (not shown) connected to the three phases of the brushless DC motor 1 is input, and the brushless DC motor is driven based on the terminal voltage. A position detection circuit 2 for detecting the position of the rotor of the DC motor 1, an inverter circuit 3,
A control for outputting an inverter switching signal, which is a commutation control signal, to the inverter circuit 3 based on the position detection signal output from the position detection circuit 2 to sequentially switch the flow state of the inverter circuit 3 for driving. And a microcomputer 5 as means.

The inverter circuit 3 is constructed by connecting six transistors Tr1 to Tr6 each having freewheeling diodes 3a to 3f to a three-phase full bridge. A rectifier circuit 10 connected to a power supply of 100 V AC is connected to the inverter circuit 3. The rectifier circuit 10 includes four diodes 10a ...
10d, and three electrolytic capacitors 11a to 11 for smoothing
It consists of c and.

The drive device of this embodiment is connected between the inverter circuit 3 and the motor 1 and has a motor current detecting means CT for detecting a motor current flowing from the inverter circuit 3 to the motor 1. The motor current value received from the motor current detecting means CT is compared with a zero level value close to zero, and a pulse signal is generated every time the motor current value exceeds the zero level value, as shown in FIG. And a comparison circuit 7 for outputting.

The comparison circuit 7 comprises a comparator 6, as shown in FIG. The non-inverting input terminal + of the comparator 6 is connected to the motor current detecting means CT.
The inverting input terminal-is connected between the resistors R1 and R2 connected in series between the power supply voltage Vcc and the ground. The resistors R1 and R2 form a voltage divider, and the voltage divider outputs the zero level value. In this case, the zero level value is Vcc × R1 /
(R1 + R2).

Further, the microcomputer 5 as the control means includes the first timer 11 for measuring the cycle of the position signal from the position detection circuit 2 and the number of pulse signals output from the comparison circuit 7 of the motor 1. Current counter 8 as pulse signal counting means for counting
Based on the number of pulse signals counted by the current counter 8 during the off period in which the absolute value of the current should be approximately zero before and after the on period when the absolute value of the current to the armature winding takes the maximum value. And the phase correction amount calculation circuit 1 for calculating the phase correction amount of the commutation control signal that equalizes the number of pulse signals in the off periods before and after the on period.
The second timer 12 as a phase correction means for correcting the phase of the commutation control signal based on the phase correction amount calculated by 0.
Is equipped with.

The microcomputer 5 of the brushless DC motor drive device having the above-mentioned configuration, as shown in the flow chart of FIG. 4A, uses the combination of the logical levels of the position signals received from the position detection circuit 2 to form the inverter circuit 3 The mode number m'determined by the transistor to be turned on and off and the combination of on and off of each transistor is determined (step S1). Then, a commutation control signal is output to each of the transistors (step S2). Next, calculate the previous mode number m of the above mode number m '
(Step S3). Then, the current counter 8 shown in FIG.
The number p of pulse signals counted as shown in (B) is stored as the number n'm of times when the motor current in the mode number m exceeds the zero level (step S4). Next, the current counter 8 is reset (step S
5).

Next, the operation of the microcomputer 5 for correcting the phase of the commutation control signal will be described with reference to the flow chart shown in FIG. 5, as shown in FIG. The number of pulse signals n0 = 7 in the off period (mode 0) before the on period (corresponding to modes 1 and 2) in which the absolute value of the motor current takes the maximum value is The number n3 of pulse signals in 3)
It will be described with reference to the case where the number is larger than 2 (when the motor current is in the advanced phase).

First, in the phase correction amount calculation circuit 10, the current counter 8 counts during the off period (mode 0 and mode 3) before and after the on period when the absolute value of the motor current should be substantially zero. The number of pulse signals n0 = 7 and n3 = 2
Based on, the phase correction amount φ is calculated according to the following equation 1.
(Step S21).

[0024]

## EQU1 ## φ = Kp × Δn + Ki × ΣΔn In this equation 1, Kp is a proportional gain of PI control, Δn
Is the difference (n3-n0) between the number of pulse signals n3 and n0, and Ki is the integral gain calculated by Ki = Kp * T / Ti. The T is a calculation cycle, and the Ti is an integration cycle.

That is, during the lead phase shown in FIG. 3 (A),
Since the number n0 of pulse signals before the ON period is larger than the number n3 of pulse signals after the ON period, the phase correction amount φ has a negative value, and the lead phase of the motor current is delayed in the delay direction. It is designed to be corrected to. On the contrary, when the phase of the motor current is a delayed phase, the number n0 of pulse signals before the ON period is smaller than the number n3 of pulse signals after the ON period. φ becomes a positive value, and the delay phase of the motor current is corrected in the forward direction.

In this way, the phase correction amount φ is always commutation controlled so that the numbers n0 and n3 of the pulse signals in the off period before and after the on period are always equal as shown in FIG. 3 (B). It is calculated as the phase correction amount of the signal.

Next, the phase correction amount calculation circuit 10 sets the phase correction amount φ in the second timer 12, and the second timer 12 starts counting the time and the phase correction amount for the time corresponding to φ. Correct the phase of the commutation control signal by φ
(Step S22). Next, the first timer 11 is reset and the time counting of the first timer 11 is started again.
(Step S23). The first timer 11 measures the cycle of the position signal of the position detection circuit 2.

As described above, in the brushless DC motor drive device of the above embodiment, the comparison circuit 7 compares the motor current value received from the motor current detection means CT with a zero level value close to zero. A pulse signal is output every time the motor current value exceeds the zero level value. Then, the current counter 8 of the microcomputer 5 counts the number of pulse signals output from the comparison circuit 7 during the off period.
Then, based on the number of pulse signals counted by the phase correction amount calculation circuit 10 in the off period before and after the on period, the number of pulse signals becomes equal in the off period before and after the on period. The phase correction amount φ of the commutation control signal is calculated so that the optimum phase of the motor current that can realize the optimum efficiency of the motor can be realized. Then, the second timer 12 corrects the phase of the commutation control signal based on the phase correction amount φ.

Therefore, according to the above-described embodiment, unlike the conventional example in which only the predetermined phase correction corresponding to the frequency is performed, the load variation to the motor is dealt with according to the actual motor current. The phase of the motor current can always be corrected to the optimum phase.

Therefore, according to the above embodiment, the commutation control signal can always be corrected to the optimum phase even if the magnitude of the load applied to the motor changes during motor operation, and the optimum efficiency of the motor can be realized.

[0031]

As is apparent from the above, in the brushless DC motor drive device of the present invention, the comparator compares the motor current value received from the motor current detecting means with a zero level value close to zero. Each time the motor current value exceeds the zero level value, a pulse signal is output, the pulse signal counting means counts the number of pulse signals output by the comparator, and the phase correction amount calculating means turns on the ON period. A phase correction amount of the commutation control signal that equalizes the number of pulse signals in the off period before and after the on period is calculated based on the number of pulse signals counted in the off period before and after the Corrects the phase of the commutation control signal based on the phase correction amount.

Therefore, according to the present invention, unlike the conventional example in which only the predetermined phase correction according to the frequency is performed, the load variation to the motor is always dealt with according to the actual motor current. The phase of the motor current can be corrected to the optimum phase.

Therefore, according to the present invention, even if the magnitude of the load applied to the motor changes during the operation of the motor, the commutation control signal is always corrected to the optimum phase, and the optimum efficiency of the motor can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of a brushless DC motor drive device of the present invention.

FIG. 2 is a waveform diagram of each phase of a motor current of a brushless DC motor.

FIG. 3 is a waveform diagram showing the motor current and a pulse signal waveform corresponding to the motor current.

FIG. 4 is a flowchart showing the operation of the microcomputer of the above embodiment.

FIG. 5 is a flowchart illustrating a phase correction operation of a commutation control signal according to the above embodiment.

FIG. 6 is an overall view showing a conventional brushless DC motor drive device and a detailed view of an induced voltage detection circuit.

FIG. 7 is a timing chart showing a terminal voltage of an armature winding of a conventional brushless DC motor, waveforms in the induced voltage detection circuit, a position signal, and a commutation control signal.

8 is a timing chart for explaining delay, advance, delay correction, and advance correction of the signal in FIG.

[Explanation of symbols]

1 ... Brushless DC motor, 2 ... Position detection circuit, 3 ... Inverter circuit, 5 ... Microcomputer, 6 ... Comparator, 7 ... Comparison circuit, 8 ... Current counter, 10 ... Phase correction amount calculation circuit, 11 ... First timer 12 … Second timer.

Claims (1)

[Claims] 1. A position detecting means (2) for detecting the position of the rotor from a terminal voltage of the armature winding of a brushless DC motor (1) having a rotor and an armature winding, and an inverter circuit (3). ) And a commutation control signal to the inverter circuit (3) in response to the position detection signal from the position detection means (2) to sequentially switch the flow state of the inverter circuit (3) to switch the motor. A brushless DC motor driving device comprising a control means (5) for driving (1), and a motor current detection means (CT) for detecting a motor current flowing from the inverter circuit (3) to the motor (1). A comparator that compares the motor current value received from the motor current detection means (CT) with a zero level value close to zero and outputs a pulse signal each time the motor current value exceeds the zero level value. (7), and the above control means (5) A pulse signal counting means (8) for counting the number of pulse signals output from the comparator (7), and an ON period in which the absolute value of the motor current to the armature winding of the motor (1) takes the maximum value. Before and after, the number of pulse signals is equalized in the off period before and after the on period based on the number of pulse signals counted by the pulse signal counting means in the off period when the absolute value of the motor current should be substantially zero. Phase correction amount calculation means (10) for calculating the phase correction amount of the commutation control signal
And a phase correction means (12) for correcting the phase of the commutation control signal based on the phase correction amount calculated by the phase correction amount calculation means (10). Drive.