JP2819655B2 - Drive device for brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a brushless motor used for audio equipment, video equipment, and the like.

2. Description of the Related Art Conventional brushless motor driving devices include, for example,
As described in Japanese Patent Application Laid-Open No. 59-53696, a position sensor such as a Hall element is used to sequentially supply a current to each phase coil. However, the provision of the Hall element causes an increase in component cost and an increase in the number of wirings.
Therefore, many brushless motors without a position sensor have been devised. As an example of a so-called sensorless brushless motor in which such a sensor is omitted, as described in JP-A-61-125413, a pulse indicating the rotational position of a rotor is formed by detecting an induced voltage of a drive coil. In some cases, a fixed delay is applied to this pulse to form an energization switching pulse.

However, in the above-described conventional brushless motor driving device, the energizing timing pulse is formed using a fixed delay device such as a monostable multivibrator. It could not be applied to changing motors.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a high-performance brushless that can detect the induced voltage and switch the energization of the drive coil to always drive the motor at an optimal energization timing regardless of the motor speed. It is intended to provide a motor driving device.

Means for Solving the Problems To solve the above problems, the present invention provides a plurality of drive transistors connected to a multi-phase drive coil of a motor,
An energization switching circuit that sequentially transmits an energization switching signal of the drive coil to the drive transistor, and a comparator that compares an induced voltage of the drive coil with a neutral point potential or power supply voltage of the drive coil for each phase, A reference phase detecting means for outputting either the falling pulse or the rising pulse of each output signal of the comparator as a reference phase pulse for the number of phases, and energizing after a predetermined delay time has elapsed since the generation of the reference phase pulse An energization switching pulse generating means for outputting the number of switching pulses for the number of phases, and the predetermined delay time is set between the generation of the energization switching pulse and a reference phase pulse generated during the energization suspension of another phase to be energized next. Second
Delay time setting means for setting the time in proportion to the predetermined time of the predetermined time, the constant voltage after the induced voltage of the drive coil of the next phase to be energized and the neutral point potential or power supply voltage of the drive coil cross When the predetermined delay time corresponding to the electrical angle has elapsed, the energization is started and the energization of the phase that has been energized up to that time is ended.

Operation According to the above-described configuration, the induced voltage of the drive coil of the motor is detected to form a drive switching signal for the drive coil, so that the motor can always be driven at an optimum power supply timing regardless of the speed of the motor.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numerals 2a, 2b, and 2c denote drive coils, one ends of which are commonly connected to a power supply terminal 3, and the other ends of which are connected to the collectors of the drive transistors 1a, 1b, and 1c, respectively. Is connected to the input terminal of Each emitter of the driving transistors 1a, 1b, 1c is grounded. Another input terminal of the reference phase detecting means 6 is connected to the power terminal 3. Further, the output terminal of the reference phase detecting means 6 is connected to the conduction switching pulse generating means 7 and to the input terminal of the delay time setting means 5. The output terminal of the delay time setting means 5 is connected to the input terminal of the energization switching pulse generating means 7. The output terminal of the current switching pulse generating means 7 is connected to the input terminal of the current switching circuit 8. The output terminal of the current switching circuit 8 is connected to the input terminal of the current switching signal amplifier circuit 4. The output terminals of the switching signal amplifier 4 are connected to the bases of the drive transistors 1a, 1b, 1c, respectively.

The specific circuit operation of the embodiment of the present invention configured as described above will be described below.

In FIG. 1, Eu, Ev and Ew are drive coils 2a and 2 respectively.
b, 2c are induced voltages. FIG. 2 is an operation signal waveform diagram in the embodiment of the present invention. When the motor rotates, the drive coils 2a, 2b and 2c have three-phase induced voltages Eu and E as shown in FIG.
v and Ew occur. The induced voltages Eu, Ev, Ew are
11a, 11b, and 11c, and compared with the power supply voltage Vcc.
A rectangular wave signal such as v, Cw is output. The square wave signal
The falling edges of Cu, Cv, and Cw are detected by differentiating circuits 12a, 12b, and 12c, and reference phase pulses Puo, Pvo, and Pwo are output.
The reference phase pulses Puo, Pvo, Pwo are induced voltages Eu, Ev, Ew
Is the timing at which it crosses the power supply voltage Vcc, and indicates the reference phase of the rotation of the rotor. The reference phase pulse Puo,
Pvo and Pwo are input to the energization switching pulse generating means 7 and are converted into energization switching pulses Pu, Pv and Pw delayed by the delay time T set by the delay time setting means 5.

The energization switching pulses Pu, Pv, Pw are input to the energization switching circuit 8. The energization switching circuit 8 includes flip-flops 15a, 15
b, 15c. Now, the energization switching pulse Pu
Is input to the conduction switching circuit 8, the flip-flop 15a
Is set. Next, when the energization switching pulse Pv is input to the energization switching circuit 8, the flip-flop 15b is set and the flip-flop 15a is reset. Further, when the energization switching pulse Pw is input to the energization switching circuit 8, the flip-flop 15c is set and the flip-flop 15b is reset. Hereinafter, this operation is repeated, and the energization switching circuit 8 outputs the three-phase energization switching signals OUTU, OUTV, OU
Output TW.

Referring to FIG. 2, the energization switching signals OUTU, OUTV, and OUTW have optimal timings with respect to the induced voltages Eu, Ev, and Ew. The energization switching signals OUTU, OUTV, OUTW of each phase are power-amplified by the energization switching signal amplifier circuit 4 and the drive transistors 1a, 1b,
Since the voltage is applied to the base of 1c and the energized state of the drive coils 2a, 2b, 2c is sequentially switched, the motor rotates efficiently.

Next, the operation of the delay time setting means 5 will be described in detail.

First, when the motor is stopped, the drive coils 2a, 2b,
Since the induced voltages Eu, Ev, Ew are not generated from 2c, the reference phase pulses Puo, Pvo,
No Pwo is generated, no electric charge is stored in the capacitor C25, and the potential of the terminal voltage Vco is zero, so that the delay time setting means 5 does not operate.

Next, consider the case where the power supply Vcc is applied for starting the motor. Further, since the motor is not rotating and no reference phase pulse is generated, the logical sum Po is L. Also the capacity
Since the terminal voltage Vco of C25 is lower than the high voltage side threshold _VH of the comparator 20, the output of the comparator 20 becomes L,
Also, the output of the comparator 21 becomes H because it is lower than the low-voltage threshold _VL of the other comparator 21,
The flip-flop 24 is reset and its inverted output -Q becomes H. Then, the transistor 30 is turned on, and the current mirror circuit formed by the transistors 31 and 32 is turned off. Therefore, the capacitor C25 is charged with the constant current Io from the transistor 33, and the potential of the terminal voltage Vco gradually increases.

Eventually, when Vco ≧ V _H , the output of the comparator 20 becomes H
And the output of the OR gate 23 also becomes H. As a result, the flip-flop 24 is set, its inverted output -Q becomes L, and the transistor 30 is turned off, so that a constant current 4Io flows by the current mirror circuit composed of the transistors 31 and 32,
The capacitor C25 is discharged at a constant current of 4Io-Io = 3Io. When the terminal voltage of capacitor C25 becomes Vco ≦ _{VL due} to discharge, the comparator
Since the output of 21 becomes H and the flip-flop 24 is reset, the inverted output -Q becomes H and the transistor 30 is turned ON again. At this time, 4Io does not flow and the capacity C25 is charged again with Io. Thereafter, by repeating this operation, the capacitor C25 is charged and discharged at a current ratio of 1: 3.

Next, consider the case where the motor is rotating. When the motor rotates, induced voltages Eu, Ev, Ew are generated, and reference phase pulses Puo, Pvo, Pwo are generated from the reference phase detection means 6,
The reference phase pulse signal Po of the logical sum is input to the OR gate 23. Incidentally, the capacitance C25 is being charged and discharged repeatedly as described above, the reference phase pulse Puo before the terminal voltage Vco reaches the high voltage side threshold V _H of the comparator 20, Pvo, Pw
The flip-flop 24 is set by the reference phase pulse signal Po of the logical sum of o, the inverted output -Q becomes L, and the transistor 30 is turned off, so that a constant current 4Io flows through the current mirror circuit composed of the transistors 31 and 32, Capacity C
25 is discharged at a constant current of 4Io-Io = 3Io. That is, the discharge start timing of the capacitor C25 is based on the reference phase pulse Pu.
The signal is synchronized with the reference phase pulse signal Po of the logical sum of o, Pvo, and Pwo. After that, as described above, the capacity C25
When the terminal voltage Vco ≦ V _L , the output of the comparator 21 becomes H
And the flip-flop 24 is reset, so that the inverted output -Q becomes H and the transistor 30 is turned on again.
At this time, 4IO does not flow and the capacity C25 is charged again with Io. Thereafter, by repeating this operation, the capacitor C25 is charged and discharged at a current ratio of 1: 3. Therefore, the waveform of the terminal voltage Vco of the capacitor C25 is a triangular wave whose slope at the time of discharging is three times that at the time of charging.

Here, the relationship between the rotation speed of the motor and the predetermined delay time T and the second predetermined time 3T shown in FIG. 2 will be further described. As is clear from the timing of the reference phase pulse signal Po in FIG. 2 and the waveform of the terminal voltage Vco of the capacitor C25, the predetermined delay time T starts discharging the capacitor C25 from the timing of a certain reference phase pulse signal Po. This corresponds to the time required for the potential of the terminal voltage Vco to fall with the discharge, reach the low-voltage threshold _VL of the comparator 21, and be inverted to charging. Therefore, for example, when the rotation speed increases, the generation timing of the reference phase pulse signal Po also advances, and since the discharge starts from the lower potential level of the terminal voltage Vco, the absolute time of T decreases. Conversely, when the rotation speed decreases, the generation timing of the reference phase pulse signal Po also delays, and since the discharge starts from a higher potential level of the terminal voltage Vco, the absolute time of T increases. That is, the predetermined delay time T is not a fixed value uniquely determined by the capacity C and the constant current value 3Io, but the absolute time varies depending on the rotation speed. The capacity C and the constant current value Io during charging and the constant current value 3Io during discharging are determined by the ratio of the charging time to the discharging time (3:
This ratio is only 1), and this ratio is ensured if the motor is rotating steadily regardless of whether the rotation speed of the motor is high or low.

Next, the energization timing will be described. The reference phase pulse signal Po is output each time the induced voltages Eu, Ev, Ew cross the power supply voltage Vcc, and in this embodiment, is output every 120 electrical degrees. Further, since the capacitor C repeats charging and discharging in synchronization with the reference phase pulse signal Po, one cycle of the charging and discharging also corresponds to an electrical angle of 120 degrees. And the capacity C
If the ratio of the charge current to the discharge current is set to 1: 3, the ratio of the charge time to the discharge time becomes 3: 1, and the delay time setting means 5
Is equivalent to an electrical angle of 30 degrees.
Accordingly, the energization is started after the induced voltage crosses the power supply voltage Vcc and the electrical angle has elapsed by 30 degrees, and the energization of the phase that has been energized up to that time is ended. 12 in electrical angle
When 0 degree has elapsed, the energization of the energized phase ends, and the energization switches to the next phase.

As described above, when forming the energization switching signal of the drive coil, energization of the phase to be energized is started at the end of energization of the immediately preceding energized phase, and generation of the reference phase pulse of the next phase during energization suspension is performed. Since the energization of the next phase is started after a predetermined delay time has elapsed from the time point and the energization of the current energized phase is terminated, the motor can follow the change in motor speed well. The motor can always be driven at the optimal timing.

In the present embodiment, the delay time T is set to be 30 degrees in electrical angle, but the delay time T is appropriately set by changing the ratio of the charging current and the discharging current as necessary, and the electrical angle is set. Changes can be made to improve the required motor performance.

Now, the delay time setting means, which is a component of the present invention,
OR means for calculating the OR of the reference phase pulses detected for each phase, and a change in the value in proportion to the elapse of time from the time when one of the reference phase pulses from the OR means arrives A first time setting means, and a time until the value of the first time setting means reaches a preset limit value is the predetermined delay time, and the value of the first time setting means is set in advance. At the time when the limit value is reached, the generation of the energization switching pulse is energized to the energization switching pulse generation means, and the time at which the preset limit value is reached is set as a starting point, and the value is proportional to the elapse of time from that point. The second time setting means that changes and the time until the next reference phase pulse arrives while the second time setting means is operating is set to the second time setting means.
And a means for switching the operation to the first time setting means when the next reference phase pulse arrives during the operation of the second time setting means. In the present embodiment, an example of analog signal processing has been described. However, it is needless to say that digital signal processing and software using a microcomputer or the like can also be implemented.

Furthermore, generally the values and characteristics of the capacitor C as the external component when energized phase turned into IC, with the independent on the value of the threshold voltage V _L and V _H, the capacitance C of the charging and discharging current Since it depends only on the ratio, a motor drive device that is easy to realize and has extremely high reliability can be realized.

As is clear from the above embodiments, the present invention detects the induced voltage in the drive coil of the motor and switches the energization of the drive coil, so that a position sensor such as a Hall element for detecting the position of the rotor is provided. Is unnecessary, and the cost of parts and the number of wirings can be reduced.

Also, when forming the energization switching signal for the drive coil, energization of the phase to be energized is started at the end of energization of the immediately preceding energized phase, and a predetermined phase is generated from the generation of the reference phase pulse of the next phase during energization suspension. After the delay time elapses, the energization of the next phase is started and the energization of the current energized phase is set to end. The motor can be driven at the energization timing.

In addition, by appropriately setting the value of the ratio between the predetermined delay time and the second predetermined time as necessary, the energization timing can be set at an arbitrary electrical angle from the zero cross point of the induced voltage of the drive coil. Measures against vibration and noise,
There is also an advantage that a device for improving the motor performance by performing an advance angle control or the like can be freely performed.

Furthermore, in the case of an IC, since the setting of energization timing does not depend on the characteristics of external components such as a capacitor, a highly reliable brushless motor driving device can be realized, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a circuit connection diagram of a brushless motor driving device according to an embodiment of the present invention, and FIG. 2 is an operation signal waveform diagram in FIG. 1a, 1b, 1c: drive transistor, 2a, 2b, 2c: drive coil, 3: power supply terminal, 4: energization switching signal amplifier circuit, 5
... delay time setting means, 6 ... reference phase detection means, 7 ...
... Energization switching pulse generating means, 8.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P ^6/ 00-6/24

Claims (1)

(57) [Claims] 1. A drive coil having a plurality of phases of a motor, a plurality of drive transistors connected to the drive coil, an energization switching circuit for sequentially transmitting an energization switching signal of the drive coil to the drive transistor, and the drive coil And a neutral point potential or a power supply voltage of the drive coil is compared for each phase by a comparator, and either one of a falling pulse or a rising pulse of each output signal of the comparator is used as a reference phase pulse, and A reference phase detecting means for outputting the power supply switching pulse for a number of phases after a predetermined delay time has elapsed since the generation of the reference phase pulse; and When it is proportional to a second predetermined time from the generation of the energization switching pulse to the reference phase pulse generated during the suspension of energization of the next phase to be energized next And a delay time setting means for setting a predetermined electrical angle corresponding to a certain electrical angle after the induced voltage of the drive coil of the phase to be energized next and the neutral point potential or the power supply voltage of the drive coil cross each other. A brushless motor driving device configured to start energization at a time point when a delay time has elapsed and to terminate energization of a phase that has been energized up to that time, wherein the delay time setting means detects each phase. OR means for calculating the logical sum of the reference phase pulses to be obtained, and a first time in which a value changes in proportion to a lapse of time from a point in time at which one of the reference phase pulses from the logical OR means arrives The time until the value of the setting means and the value of the first time setting means reaches the preset limit value is the predetermined delay time, and the value of the first time setting means reaches the preset limit value. At the time A second time setting means for energizing the energization switching pulse generation means to generate an energization switching pulse and starting from a point in time when the preset limit value is reached, and changing the value in proportion to a lapse of time thereafter. And the time until the next reference phase pulse arrives while the second time setting means is operating is defined as the second predetermined time. Means for switching the operation to the first time setting means at the time of arrival of the pulse.