JP2502577B2 - Brushless motor drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device without a position detector for detecting the position of a mover of a motor.

2. Description of the Related Art In recent years, brushless motors have often been used for various driving motors in order to extend their life, increase reliability, or reduce the shape of the motor. Generally, a brushless motor requires a position detector that detects the position of the mover.To achieve further cost reduction and downsizing, a so-called commutation sensorless brushless motor without a position detector is required. It's coming. As a conventional example of such a brushless motor driving device, for example,
There is one such as that disclosed in Japanese Patent Laid-Open No. Sho 52-80415.

Hereinafter, an example of the above-described conventional brushless motor driving device will be described with reference to the drawings.

FIG. 9 is a circuit configuration diagram of a conventional brushless motor drive device. In FIG. 9, one ends of the drive coils 1 to 3 are common, and the other end of the drive coil 1 is connected to the anode of the diode 4, the cathode of the diode 5 and the drive transistor 10.
The other end of the driving coil 2 is connected to the anode of the diode 6, the cathode of the diode 7, and the collectors of the driving transistors 11 and 14,
The other end of the driving coil 3 is connected to the anode of the diode 8, the cathode of the diode 9, and the collectors of the driving transistors 12 and 15. The cathodes of the diodes 4, 6, 8 and the emitters of the drive transistors 10, 11, 12 are connected to a positive side feed line, and the anodes of the diodes 5, 7, 9 and the emitters of the drive transistors 13, 14, 15 are It is grounded. The other ends of the drive coils 1 to 3 are input to a filter circuit 16, and the output of the filter circuit 16 is input to a conduction switching circuit 17. The output of the current switching circuit 17 is input to the bases of the drive transistors 10 to 15, respectively.

The operation of the conventional brushless motor driving device configured as described above will be described below.

FIG. 10 is a diagram for explaining the operation in FIG. 9, in which U ₀ , V ₀ ,
W ₀ is the energization waveform of the drive coils 1, 2, and 3. The energizing waveform U
_The harmonic components of ₀ , V ₀ , and W ₀ are removed by the filter circuit 16 and the phases thereof are delayed by 90 °, and are converted into F ₁ , F ₂ , and F ₂ , respectively. Note that the filter circuit 16 is a primary filter, and is composed of, for example, an RC passive filter, a primary mirror integration circuit, and the like, and its cutoff frequency is set sufficiently lower than the frequency of the drive coil conduction waveform. The outputs F ₁ , F ₂ , and F ₃ of the filter circuit 16 are supplied by the energization switching circuit 17,
U _H , U _L , V _H , V _L , W _H , W _L are logically processed, and the driving transistors 10 to 15 are switched. At this time, the switching operation is performed so that the motor driving torque is always generated in one direction, and the motor is driven.

Problems to be Solved by the Invention However, in the above configuration, a filter circuit having a low cutoff frequency characteristic is required for each phase of the drive coil, and therefore a large number of capacitors having a large capacity are required.

In addition, when the inductance of the drive coil is large, there is a so-called armature reaction in which the energizing current of the drive coil is delayed with time after the drive transistor is turned on.

In such a case, it is known that if the drive coil is energized at the timing shown in FIG. 10, the efficiency is lowered. As a remedy for this, the phases of the signals of F ₁ , F ₂ and F ₃ are advanced slightly,
Japanese Patent Application Laid-Open No. 52-80415 discloses a method of operating a drive transistor so as to compensate for a delay in energization due to an armature reaction, but in order to realize this, a component such as a capacitor is further required. Also, drive coil energization waveform
U _0, V _0, W ₀ is or spike noise generated at the time of off of the driving transistor, supply voltage variation, there is a current fluctuation due to load fluctuation, U _0, V _0, W filter circuit from conduction waveform of ₀ It is often difficult to accurately obtain the energization switching signal by using. As a countermeasure against this, a system as shown in Japanese Patent Publication No. 59-36519 is devised.

However, the method of obtaining the energization switching signal from the driving coil energization waveform by using the filter circuit basically has the following problems. That is, the energization current when the drive coil is energized, the voltage drop generated by the drive coil internal impedance, and the spike noise generated immediately after the energization is stopped are superimposed on the fundamental wave (back electromotive force) of the drive coil energization waveform. It constantly fluctuates with fluctuations in power supply voltage and load. Therefore, when the energization switching signal is obtained by filtering the energization waveform of the drive coil, an error occurs due to the above-described component that is constantly fluctuating and superimposed on the fundamental wave (back electromotive force) of the energization waveform, and the energization of the drive coil is accurate. Becomes difficult.

In order to solve the above-mentioned problems, various methods have been devised to accurately obtain the energization switching signal, but basically, the phase difference between the drive coil back electromotive voltage and the energization switching signal should be kept constant. The adjustment is performed around the filter circuit, and the adjustment is extremely troublesome. In addition, a large number of capacitors are required in addition to the filter circuit configuration. Therefore, the number of external parts and the number of pins are increased in the case of an IC, which is expensive. Further, a method of digitally obtaining an energization switching signal by using a microcomputer or the like without using a filter circuit is described in JP-A-61-293191, but it is still expensive.

As described above, the conventional brushless motor driving device obtains an energization switching signal having a fixed phase relationship with respect to the position of the mover by a filter circuit from the energization waveform of the driving coil, and utilizes the driving coil to drive the driving coil by using the signal. Since it is configured to energize sequentially, voltage drop of the drive coil due to spike noise and energizing current included in the energizing waveform of the driving coil,
It is difficult to obtain an accurate energization switching signal due to fluctuations of these superimposed components due to fluctuations in the power supply voltage and load, and further to the effects of armature reaction and the like. In addition, a large number of large-capacity capacitors are required when configuring the filter circuit, especially IC
In such a case, the number of external parts and the number of pins increase, which is disadvantageous in terms of price. As described above, the conventional brushless motor driving device has various problems.

In view of the above problems, the present invention eliminates a large number of capacitors required in the conventional filter circuit configuration by obtaining a drive coil energization switching signal without using a filter circuit, and simultaneously reduces the drive coil energization waveform. An object of the present invention is to provide a novel brushless motor drive device capable of sequentially energizing and driving a drive coil without being affected by spike noise, power supply voltage fluctuation, load fluctuation, and armature reaction.

Means for Solving the Problems In order to solve the above problems, a brushless motor driving device according to the present invention includes a motor drive coil of a plurality of phases, a plurality of drive transistors provided in the drive coil, and the drive coil. Of an energization switching signal sequentially transmitted to the drive transistor, a voltage controlled oscillator for inputting a signal having an appropriate frequency to the energization switching circuit, a counter electromotive voltage generated in the drive coil and the drive coil. A phase error detector for detecting the phase difference between the energization switching signals, an error amplifier for amplifying the output of the phase error detector, and an output of the error amplifier as an input of the voltage controlled oscillator.

Action The present invention, by the above-described configuration, detects the phase difference between the back electromotive voltage generated in the motor drive coil and the energization switching signal of the coil, and controls the frequency and phase of the energization switching signal according to the detected phase difference, Since the feedback loop, that is, the phase control loop (PLL loop) is configured so that the energization switching signal maintains a constant phase relationship with respect to the position of the mover, the filter circuit that has been necessary in the past is no longer necessary. Since it has the filter circuit, it becomes unnecessary. Therefore, all the various problems caused by having the filter circuit can be eliminated.

Embodiment A brushless motor driving device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a brushless motor driving device according to an embodiment of the present invention. In FIG. 1, parts having the same functions as those of the conventional brushless motor drive device shown in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 1, the bases of the driving transistors 10 to 15 are connected to the output of a power amplifier 43, respectively, and the input of the power amplifier 43 is connected to the output of a logic circuit 42. Here, the logic circuit 42 and the power amplifier 43 constitute a conduction switching circuit 44. The input of the logic circuit 42 is connected to the output E of the frequency dividing circuit 41, and the input of the frequency dividing circuit 41 is connected to the output of the voltage controlled oscillator 40. The other output D of the frequency dividing circuit 41 and the outputs U ₁ , U ₂ , V ₁ , V ₂ , W ₁ , W _{2 of the} logic circuit 42 and one ends U ₀ , V _{0 of} the drive coils 1, 2, 3 W ₀ is input to the phase error detector 20, and the output A of the phase error detector 20 is a resistance.
Is connected to the inverting input terminal of the operational amplifier 31 via 32, and a resistor is provided between the inverting input terminal and the output terminal of the operational amplifier 31.
A series circuit of 33 and a capacitor 34 and a capacitor 35 are inserted. The non-inverting input terminal of the operational amplifier 31 is a resistor 36, 3
A constant bias voltage is applied by 7. Here, the components 31 to 37 constitute an error amplifier 30, and an output B of the error amplifier 30 is connected to an input of the voltage controlled oscillator 40. Further, the output C of the starting circuit 60 is connected to the inverting input terminal of the operational amplifier 31,
Is connected to one end of a resistor 61 provided between the common emitter of the driving transistors 13 to 15 and the ground.

The operation of the brushless motor driving device configured as described above will be described below.

FIG. 2 is an explanatory view of the operation principle of the present invention, and shows the phase relationship between the drive coil back electromotive voltage and the drive coil conduction waveform. FIG. 2A shows a case where the phase relationship between the back electromotive voltage (broken line) and the conduction waveform (solid line) is in an optimum state, and FIGS. The case where the state deviates from the state is shown. In FIG. 1, the output of the voltage controlled oscillator 40 is transmitted to the driving coils 1 to 3 through the frequency dividing circuit 41, the conduction switching circuit 44, and the driving transistors 10 to 15. Therefore, there is a certain phase relationship between the output of the voltage controlled oscillator 40 and the energization waveform of the drive coils 1 to 3. That is, by controlling the oscillation frequency and phase of the voltage-controlled oscillator, it is possible to control the phase difference between the drive coil back electromotive voltage and the drive coil conduction waveform. Therefore, as shown in FIGS. 2 (b) and 2 (c), when a deviation of the phase angle の 間 に occurs between the drive coil back electromotive voltage and the drive coil energization waveform, the phase error ψ is detected as a phase error. By providing a phase control loop for controlling the oscillation frequency and phase of the voltage-controlled oscillator 40 so as to be detected and amplified by the amplifier 20 and the error amplifier 30 so that ψ becomes zero, the optimum energizing state as shown in FIG. Can be secured. Therefore, the motor drive coil can always be generated stably and efficiently, and the motor is driven.

As a specific configuration of the phase error detector 20, for example, the one shown in FIG. 3 can be considered. That is, in FIG. 3, one end U ₀ of the drive coil 1 in FIG.
One end of 121, non-inverting input terminal of comparator 101 and comparator 10
4, one end V ₀ of the drive coil 2 in FIG. 1 is connected to one end of the resistor 122, the non-inverting input terminal of the comparator 102 and the inverting input terminal of the comparator 105.
One end W ₀ of the drive coil 3 in the figure is connected to one end of the resistor 123, the non-inverting input terminal of the comparator 103, and the inverting input terminal of the comparator 106.

Inverting input terminals of the comparators 101 to 103 and the comparator 104
The non-inverting input terminals of ~ 106 are common and are connected to the other ends of the resistors 121-123. The respective outputs of the comparators 101 to 106 are common via the switch circuits 111 to 116 and form the output A of the phase error detector. Frequency divider circuit 41 in FIG.
Output D and outputs of the logic circuit 42 U ₁ , U ₂ , V ₁ , V ₂ , W ₁ ,
W ₂ is input to the pulse generation circuit 130, and the switching control signals S ^UH , S ^VH , S ^WH , S ^UL , S ^VL and S of the switch circuits 111 to 116 are input.
Output ^WL .

The operation of the phase error comparator configured as described above will be described below.

FIG. 4 is an explanatory diagram of the operation, and shows a state of detection of a phase error between the back electromotive voltage and the conduction waveform of the drive coil 1. In FIG. 1, FIG. 3, and FIG.
Driving coil 1 signals U _1, U ₂ is synchronized with the D and E is divided outputs of the voltage controlled oscillator 40, it is energized as current command signal (i.e. U _H, U _L). Therefore, the period during which neither U ₁ nor U _{2 is} output is the energization suspension period, during which the drive coil energization waveform U ₀ coincides with the back electromotive force U _e . As shown in FIG. 4, the energization suspension period is a period from when U ₁ becomes Low to when U ₂ becomes High, and corresponds to 1 clock of E or 2 clocks of D. U ₂ is the U ₁ from the Low exists energization pause period also in the period until the High but for simplicity of explanation, consider only the period of the former. When the neutral point voltage N ₀ of each drive coil and the drive coil energization waveform U ₀ are compared during the energization suspension period, U ₀ and the drive coil counter electromotive voltage U _e are compared.
When the phase difference ψ is zero and, N ₀ and U ₀ is consistent from when the central i.e. U ₁ is Low energization pause period after one clock of the D. If U ₀ lags U _e by the phase difference ψ, N ₀
And U ₀ match before 1 clock after D after U ₁ becomes Low, and when U ₀ leads U _e by the phase difference ψ, N ₀ and U ₀
Matches after 1 clock of D after U ₁ becomes Low. Therefore, the phase relationship between U ₀ and U _e can be known by comparing U ₀ and N ₀ one clock after D after U ₁ becomes Low. Therefore, as a method for detecting the phase difference ψ, a phase error detection pulse signal S _UL having an appropriate width is generated with reference to one clock after D after U ₁ becomes Low, and N _{0 is} generated only when S _UL occurs. And U ₀ , the comparator output A _UL having a duty corresponding to the phase difference ψ can be obtained. In Fig. 4, S _UL occurs for a period of ± 1/2 clock of D after 1 clock of D after U ₁ becomes Low, and U ₀ lags U _e by a phase angle ψ. Is shown.

Above, with respect to conduction waveform U ₀ of the driving coil 1, U ₁ is Low
Although U ₂ is explained the operating principle for the detection of the conduction pause period phase difference using ψ between until High from when the other conduction rest periods for U _0, i.e. U ₂ is Low
After that, it can be similarly detected in the period from when U ₁ becomes High and in the energization waveforms V ₀ and W ₀ of the other drive coils 2 and 3, and in the present embodiment, by combining all of these, the phase The error detector output A is obtained.

FIG. 5 shows the operation waveforms of the respective components when the configuration shown in FIG. 3 is used as the phase error detector 20 in FIG. 1, and the phase difference between the drive coil conduction waveform and the back electromotive voltage is zero. FIG. 6 shows how the oscillation frequency f of the voltage controlled oscillator is controlled so that

As described above, according to this embodiment, the motor drive coil is always energized based on the output of the voltage controlled oscillator, and the phase difference between the energization waveform and the drive coil counter electromotive voltage is detected by the phase error detector, By providing a so-called phase control loop (PLL loop) that controls the oscillation frequency and phase of the voltage controlled oscillator so that the phase error becomes zero by the amplified signal, there is no effect of armature reaction and the motor is driven efficiently. In addition, a filter circuit which has been necessary in the past is not required, and therefore a large capacity capacitor can be significantly reduced. Also, the phase error detector generates a phase error detection pulse during the drive coil energization pause period, and obtains the phase error output by comparing the drive coil energization waveform and the neutral point voltage only during the detection pulse generation period. By setting the pulse generation timing while avoiding the spike noise generation period that occurs immediately after the drive coil is de-energized, it is possible to eliminate the influence of the spike noise. Further, since the phase error is detected during the energization stop time, there is no influence of the voltage drop due to the energization current generated during the energization period and the impedance of the drive coil or its variation. Furthermore, the width of the phase error detection pulse that occurs during the power-off period is the electrical angle of the motor or
The phase error is constant with respect to the mechanical angle, and the phase error depends only on the duty of the comparison output between the counter electromotive voltage and the neutral point voltage during the detection pulse generation period. Therefore, the phase control loop can always be operated stably.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a circuit configuration diagram of a brushless motor driving device according to a second embodiment of the present invention. In FIG. 6, the configuration is the same as that of FIG. 1 except that the center frequency setting circuit 50 is added to the input of the voltage controlled oscillator 40.

The operation of the brushless motor driving device configured as described above will be described below.

FIG. 7 is a circuit connection diagram showing a specific configuration of the center frequency setting circuit 50. In FIG. 7, I _m is the current flowing through the motor drive coil, and thus V _i is determined by the motor drive current I _m . Further, V _m is determined by V _cc, that is, the power supply voltage. Here, the values of resistors 61 and 51 to 54 are
Assuming R ₆₁ and R _{51 to} R ₅₄ , the output current I _o of the center frequency setting circuit shown in FIG. 7 is calculated by the following equation.

However, it is assumed that the current amplification factor of each transistor constituting the circuit shown in FIG. 7 is sufficiently large and the characteristics are well aligned.

On the other hand, the load characteristic of the motor is generally given by the following equation.

Here, N is the rotation speed, K _a is the induced voltage constant, μ is the load change rate, K _T is the torque constant, V _cc is the power supply voltage (motor terminal voltage), and I _m is the motor current.

Comparing the equations (1) and (2), it can be seen that there is the following correspondence.

N → I _o Therefore, by properly setting the circuit constants of R ₆₁ and R _{51 to} R ₅₄ , the output I _o corresponding to the load characteristics of the motor can be obtained. This is shown in FIG. If an output according to the load characteristics of the motor can be obtained, the voltage-controlled oscillator output can be set to bring the phase difference between the drive coil back electromotive force voltage and the energization waveform close to zero to some extent without a phase control loop. it can. Therefore, the load on the phase control loop for reducing the phase difference to zero is lightened, and the motor drive coil can be obtained more stably and efficiently.

As described above, according to the present embodiment, by providing the center frequency setting circuit of the voltage controlled oscillator in addition to the phase control loop shown in the embodiment of FIG. 1, the voltage controlled oscillator is adjusted according to the load characteristics of the motor. Coarsely adjusts the oscillation frequency of the control loop to reduce the operation load of the phase control loop, improve the responsiveness of the phase control loop to abrupt changes in the power supply voltage and load change, and expand the motor to a wider operating voltage range and operating load range. Is applicable.

The starting circuit 60 shown in FIGS. 1 and 6 is used.
Is for operating so that the oscillation frequency of the voltage controlled oscillator gradually rises until the frequency of the drive coil counter electromotive voltage and the energization waveform approach each other when the power is turned on and the phase control loop can be established. The operation is performed when the energizing current of the drive coil is extremely increased, a minute current is generated from the output C, the output of the error amplifier 30 is gradually changed, and the voltage controlled oscillator is operated.

Further, although the full-wave drive type motor is shown in the present embodiment, it is also applicable to a half-wave drive type motor.

As described above, according to the present invention, the motor drive coil is energized based on the output of the voltage controlled oscillator, and the phase difference between the energization waveform and the motor drive coil back electromotive force is detected by the phase error detector and detected. After amplifying the phase error signal by the error amplifier,
By inputting to the voltage controlled oscillator and constructing a phase control loop to control the output, the filter circuit that was required before is not required, therefore the large capacity capacitor can be greatly reduced, and the drive coil energization waveform can be reduced. Spike noise included, voltage drop due to current and drive coil impedance, these fluctuations due to fluctuations in power supply voltage and load,
Furthermore, there is no problem such as a decrease in efficiency due to armature reaction,
A drive device for a brushless motor having extremely excellent characteristics can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a brushless motor drive device according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operating principle of FIG. 1, and FIG. 3 is a specific circuit configuration diagram of a phase error detector. ,
FIG. 4 is an operation explanatory view of FIG. 3, FIG. 5 is an operation waveform diagram in the embodiment of the present invention, and FIG. 6 is a circuit configuration diagram of a brushless motor drive device in the second embodiment of the present invention. 7
Fig. 8 is a concrete circuit diagram of the center frequency setting circuit, Fig. 8 is an operation characteristic diagram of Fig. 7, Fig. 9 is a circuit configuration diagram of a conventional brushless motor driving device, and Fig. 10 is an operation of Fig. 9. FIG. 1-3 drive coil, 10-15 drive transistor,
20 ... Phase error detector, 30 ... Error amplifier, 40 ... Voltage controlled oscillator, 44 ... Energization switching circuit, 50 ... Center frequency setting circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-50-23807 (JP, A) JP-A-52-12412 (JP, A) JP-A-52-80414 (JP, A) JP-A-54- 72413 (JP, A)

Claims (2)

(57) [Claims] 1. A multi-phase motor drive coil, a plurality of drive transistors provided in the drive coil, an energization switching circuit for sequentially transmitting an energization switching signal of the driving coil to the drive transistor, and the energization switching circuit. A voltage controlled oscillator for inputting a signal having an appropriate frequency, a phase error detector for detecting a phase difference between a counter electromotive voltage generated in the drive coil and a conduction switching signal of the drive coil, and a phase error detector of the phase error detector. An error amplifier that amplifies an output, and a brushless motor drive device that uses the output of the error amplifier as an input of the voltage controlled oscillator. 2. A pulse generation circuit for inputting a signal corresponding to an energization switching signal of a motor drive coil to a phase error detector and generating a pulse signal during an energization suspension period of the drive coil,
A comparator for comparing the energization signal of the drive coil and a neutral point voltage of each drive coil or a signal corresponding thereto, a switch circuit provided at the output of the comparator, and a pulse for opening and closing the switch circuit. The brushless motor drive device according to claim 1, wherein the drive circuit is configured to perform the output of the generating circuit.