JPH05316788A - Driver for brushless motor - Google Patents

Abstract

PURPOSE:To obtain an inexpensive driver for brushless motor having simple circuitry in which switching from external control driving to synchronous driving can be made positively at the time of starting. CONSTITUTION:Rising and falling edges of counter-electromotive force detection signal are detected through the use of signal edge detecting function 16 of a microcomputor 13 thus obtaining a timing for switching a driving output signal pattern. Time difference between a driving output switching timing and pattern switching timing for external control signal is measured by means of a timer 15 and switching is made from external control driving to synchronous driving when the time difference is equal or close to zero. If the driving output pattern switching timing occurs with time lag behind the pattern switching timing for external control signal, a decision is made that starting failed and stop process takes place. This driver realizes positive switching from external control driving to synchronous driving through simple circuitry at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor drive device for detecting the position of a rotor by a counter electromotive voltage generated in a drive winding to drive the rotor.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional brushless motor driving device disclosed in, for example, Japanese Examined Patent Publication No. 59-36520. In FIG. And an inverter circuit composed of free wheeling diodes 2Da to 2Df, 3
Is a filter circuit connected to the output of the inverter circuit 2 like the brushless motor 1, 4 is a comparator connected to the output of the filter circuit 3, 5 is an oscillator for other control drive at startup, and 6 is an oscillator 5. A shift register connected to the output, 7 is a changeover switch for changing the other control signal from the shift register 6 and the output signal of the comparator 4 by a changeover command, and 8 is a three-phase signal selected by the changeover switch 7 for a 6-phase signal. Switching element 2Ta
Is a logic circuit for converting to a 2Tf control signal.

Further, 9a to 9f, 10a and 10b in FIG.
Is a logic circuit, 11a and 11b are filters connected to the output of the logic circuit 10, and 12 is a differential amplifier connected to the output of the filter 11.

Next, the operation will be described. As a basic operation, the rotation of the brushless motor 1 is connected by controlling the switching elements 2Ta to 2Tf according to the rotational position of the rotor of the brushless motor 1.

At the time of start-up, the brushless motor 1 is driven by another control method, so that the control switch 7 selects another control signal obtained by converting the output of the oscillator 5 into three phases by the shift register 6. The rotor of the brushless motor 1 is started and accelerated by the other control signal selected by the changeover switch 7, and a counter electromotive voltage is generated in the drive winding. The back electromotive force signal is transmitted through the filter circuit 3 and the comparator 4 as shown in FIG.
20a to 20c of the counter electromotive voltage detection signal.

On the other hand, reference numeral 21a in FIG. 6 is another controlled signal for the phase a, and in addition to the logical comparison with the counter electromotive voltage signal 20a, an inverted signal of 20b is added as shown in the logic circuit 9a in FIG. When the rotor advances in phase with reference to the phase difference of zero, a pulse width signal 23 of a solid line proportional to this is obtained. Similarly, the respective phases are combined by the logic circuit 10a of FIG. 5, and the pulse width signal 23 becomes a signal shown by a solid line and a broken line.

When the phase of the rotor is delayed and the other control signal is in the state of 22a of FIG. 6, the pulse width signal 24 of FIG. 6 showing the phase delay is output by the logic circuits 9d and 10b of FIG. 5 as before. Is obtained.

When these pulse width signals 23 and 24 are respectively smoothed by the filter 11 and applied to the differential amplifier 12, the output becomes a DC signal showing a phase difference with respect to the rotation signal of the rotor, and a positive voltage due to phase advance. , With a delay, a negative voltage and a zero voltage without a phase difference are detected.Therefore, the voltage value at or near zero is detected and used as a switching command. Switch.

[0009]

Since the conventional brushless motor driving device is constructed as described above, the circuit for detecting the phase difference is complicated, and the number of parts is large and the cost is high. There was a problem.

The present invention has been made in order to solve the above problems, and a circuit configuration is simple and can be surely switched from the alternative drive to the synchronous drive, and an inexpensive brushless motor drive device can be obtained. With the goal.

[0011]

A brushless motor drive apparatus according to the present invention includes a pattern output timing determination means for determining a timing for switching a drive output signal pattern from a reverse voltage signal, a front output switching timing, and another control signal. A time difference measuring means for measuring a time difference between pattern switching timings, a means for comparing a predetermined reference time with a previous measurement result, and a means for switching from another type drive to a synchronous type drive when the time difference is zero or near zero, and another type When the timing of switching the drive output pattern by the counter electromotive voltage signal from the signal pattern switching timing occurs later than another reference time, it is determined that the startup is unsuccessful, and the startup failure determination means performs stop processing.

[0012]

The brushless motor driving device according to the present invention measures the time difference between the drive output switching timing by the back electromotive voltage signal and the pattern switching timing of the other control signal, and when the time difference is zero or near zero, it synchronizes from the other control drive. Switch to type drive. If the timing at which the drive output pattern is switched by the back electromotive force signal occurs later than the pattern switching timing of the other control signal, it is determined that the startup has failed, and the stop processing is performed.

[0013]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a brushless motor, 2 is an inverter circuit composed of switching elements 2Ta to 2Tf and freewheeling diodes 2Da to 2Df, 3
Is a filter circuit, 4 is a comparator, and these are the same parts as the conventional circuit shown in FIG.

A switching element 2 includes a memory 14, a timer 15, a signal edge detecting function 16 and the like.
It is a microcomputer (hereinafter, referred to as a microcomputer) that outputs a Ta to 2Tf control signal.

Next, the operation will be described. The basic operation is the same as the conventional example, but in order to drive the brushless motor 1 in another system at the time of start-up, the other system signal stored in advance in the memory 14 of the microcomputer 13 is output. The rotor of the brushless motor 1 is started and accelerated by the other control signal, and a counter electromotive voltage is generated in the drive winding. The counter electromotive voltage signal is passed through the filter circuit 3 and the comparator 4 to 30a of FIG.
A counter electromotive voltage detection signal such as ~ 30c is obtained. Then, the rising edge and the falling edge of each back electromotive voltage detection signal are detected by using the signal edge detection function 16 of the microcomputer 13 to obtain the timing for switching the drive output signal pattern.

On the other hand, 31a to 31c and 32a to 3 in FIG.
2c is an alternative control signal for each phase, but since output from the microcomputer 13 is started under substantially the same conditions, the counter electromotive force detection signal edge generated by acceleration of the rotor (for example, a in FIG. 2) is And the rising edge of the other system signal (Fig. 2B)
Is delayed, and the time difference between both edges (33 in FIG. 2) becomes smaller as time passes.

Now, the method of measuring the time difference and other operations will be described with reference to the flowchart of FIG. First, in step 40, it is determined whether the time difference measurement has already been performed, and if not, it is determined in step 41 whether it is the timing for switching the drive output. If it is not the switching timing, the process returns, but if it is the switching timing, the timer count is started using the timer 15 in step 42 and the process returns. If the measurement has already been performed in step 40, it is determined in step 43 whether it is the switching timing of the other system signal during which the output is continued. At this time as well, the process returns if it is not the switching timing, but if it is the switching timing, the timer count is stopped in step 44. By the flow so far, the time difference between the edge of the back electromotive force detection signal and the rising edge of the other control signal is measured.

Next, in step 45, the reference time 1 which is close to zero as the value stored in the memory 14 is compared with the measured time. If the reference time is 1 or less, in step 46 the other system drive is switched to the synchronous drive. .. If it is not within the reference time 1, the measured time is further compared with the reference time 2 stored in the memory 14 in step 47. If the reference time 2 is not reached, the process returns, but the reference time 2 or more is reached. In this case, the drive output is immediately stopped in step 48 because the start has failed.

Therefore, when there is a small time difference such as C or D in FIG. 2C, the other system drive is switched to the synchronous system drive. On the contrary, when the time difference becomes large to some extent, the other system signal is given. If the timing for switching the drive output pattern by the counter electromotive voltage signal occurs later than the pattern switching timing, it is determined that the startup has failed, and the stop processing is performed.

[0020]

As described above, according to the present invention, the inverter circuit is controlled by the other control signal to start the brushless motor, and then the inverter circuit is synchronized based on the counter electromotive voltage signal generated in the drive winding. In a drive device for a brushless motor that is controlled by a formula signal to normally operate the brushless motor, pattern output timing discriminating means for discriminating the timing for switching the drive output signal pattern from the reverse voltage signal after another control start, and front output switching The time difference measuring means for measuring the time difference between the timing and the pattern switching timing of the other control signal is compared with the predetermined reference time and the previous measurement result to change from the other control drive to the synchronous drive when the time difference is zero or near zero. Switching means and drive output by counter electromotive voltage signal from pattern switching timing of other system signal If the timing for switching the turn occurs later than another reference time, it is determined that the startup has failed and the startup failure determination means for performing the stop processing is provided. There is an effect that a simple and inexpensive product can be obtained.

[Brief description of drawings]

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

FIG. 2 is a waveform chart of each part for explaining the operation of the brushless motor driving device according to the embodiment of the present invention.

FIG. 3 is a flow chart for explaining the operation of the brushless motor driving device according to the embodiment of the present invention.

FIG. 4 is a circuit configuration diagram showing a conventional brushless motor driving device.

FIG. 5 is a circuit diagram for detecting a phase in a conventional brushless motor driving device.

FIG. 6 is a waveform chart for explaining the operation of a conventional brushless motor driving device.

[Explanation of symbols]

 1 Brushless Motor 2 Inverter Circuit 3 Filter Circuit 4 Comparator 5 Oscillator 6 Shift Register 7 Changeover Switch 8 Conversion Logic Circuit 9 Logic Circuit 10 Logic Circuit 11 Filter 12 Differential Amplifier 13 Microcomputer 14 Memory 15 Timer 16 Signal Edge Detection Function

Claims (1)

[Claims] 1. A brushless motor is started by controlling an inverter circuit by another control signal, and then the inverter circuit is controlled by a synchronous signal based on a counter electromotive voltage signal generated in a drive winding to keep the brushless motor steady. In the drive device of the brushless motor to be operated, after the other system start,
Pattern output timing determination means for determining the timing of switching the drive output signal pattern from the reverse voltage signal, time difference measuring means for measuring the time difference between the previous output switching timing and the pattern switching timing of the other control signal,
Means to switch from other control drive to synchronous drive when the time difference is zero or near zero by comparing the predetermined reference time with the previous measurement result, and drive output by counter electromotive voltage signal from the pattern switching timing of other control signal A drive device for a brushless motor, comprising: a start failure determination means that determines a start failure and performs a stop process when the timing of switching patterns occurs later than another reference time.