JPH10271880A - Driver circuit for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless-motor driver circuit capable of operating a brushless motor at variable speed in a sensor-less method without being subject to the effect of chopper control. SOLUTION: The change of an armature current by the revolution of the brushless motor 51 is detected by a current detector 4 and output to a higher- harmonic filter circuit 13. Such a voltage is stored in the circuit 13 by synchronization with chopper control, amplified up to approximately quintuple or septuple, and output to a first reducing circuit 5 and a averaging circuit 6. The voltage is reduce at approximately half times by the first reducing circuit 5, and output to a communication command circuit 9 while being levelled by the averaging circuit 6, and lowered by approximately 0.7 times by a second reducing circuit 8 and output to the commutation command circuit 9. When the voltage of the first reducing circuit 5 is made larger than that of the second reducing circuit 8, the arrival or the second current increase region of the armature current is decided by the commutation command circuit 9 and a commutation command is output, and the commutation operation of the brushless motor 51 is conducted by a counter circuit 11 and a distributing circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet field type brushless motor drive circuit, and more particularly to a brushless motor drive circuit capable of sensorless variable speed operation without using a magnetic pole position sensor of a field. It is about.

[0002]

2. Description of the Related Art Conventionally, a sensorless drive circuit for a brushless DC motor of this type focuses on a correlation between a speed electromotive force generated in an armature winding of a rotating motor and a position of a magnetic field, and focuses on the speed electromotive force. Determines the commutation timing of the motor. When the motor is started, the motor is forcibly commutated at a preset frequency and voltage as a synchronous motor or a stepping motor, and balances the load with a load up to a rotation range where sufficient speed electromotive force for field position detection is generated. I kept trying to accelerate slowly.

However, in such a motor drive circuit, the acceleration time after starting the motor is inevitably increased,
In addition, it has been difficult to start and operate with low rotation and high torque. That is, since rapid acceleration control is difficult due to the instability of the speed torque characteristic, the forced commutation mode (so-called non-control operation) and the synchronous inverter operation mode by feedback of the estimated position information (so-called self-control operation) are used. It had two modes and had to accelerate gently while maintaining the balance with the inertia of the power system including the motor and the load torque. The commutation timing is determined by the speed electromotive force. However, this speed electromotive force must be detected by using the armature winding voltage of the motor. The commutation spike voltage due to the recirculation effect increases, and a large error occurs in the speed electromotive force information that can be detected. As a result, a large error occurs in the estimation result of the field pole position, and an appropriate commutation timing cannot be determined.

[0004]

Therefore, the present applicant has invented a sensorless drive circuit for a brushless motor described in Japanese Patent Application No. 7-207665. Such a motor drive circuit focuses on the waveform characteristics common to each of the four waveform blocks constituting the armature current waveform of each phase of the motor as shown in FIG. Two significant current increase areas 41, 4 appearing in each block
2 (FIG. 1 (b)), the second current increase region 42 is detected, this is determined as the arrival of the commutation timing (commutation timing), and commutation control is performed. The detection of the second current increase region 42 is performed based on the fact that the armature current of the motor has become a predetermined multiple (for example, 1.2 times) of the average value of the armature current.

The variable speed operation of the brushless motor is performed by changing the on / off duty ratio of the inverter circuit by PWM (pulse width modulation) chopper control. A chopper-like voltage is applied to the brushless motor by the chopper control. Since the chopper-like voltage is integrated by the LR series impedance of the armature winding, the armature current flows almost continuously. However, since the removal of the carrier component is not performed completely, the armature current has a current waveform containing a large amount of harmonic components. Therefore, if the commutation timing is determined based on this current waveform, there is a problem that the commutation timing is erroneously determined due to the influence of the harmonic component.

Accordingly, the applicant of the present application has filed a Japanese Patent Application No. Hei.
As shown in FIG. 2 of 207665, a low-pass filter circuit 5f formed by a capacitor and a reactance
The invention has invented a brushless motor drive circuit that removes a harmonic component of an armature current and determines a commutation timing based on the armature current from which the harmonic component has been removed and an average value of the armature current.

However, in a drive circuit using such a low-pass filter, the value of the armature current is averaged by the low-pass filter together with the removal of the harmonic components. The value of the armature current to be obtained also becomes small. Therefore, in such a case, the second current increase region 42 must be detected by a slight change in the armature current, and there is a problem that a detection error increases. That is, when the duty ratio of the chopper control is small, there is a problem that the commutation timing is erroneously caused even by a slight noise.

An object of the present invention is to provide a brushless motor drive circuit capable of operating a brushless motor at a variable speed without a sensor without being affected by chopper control. It is an object.

[0009]

In order to achieve this object, a brushless motor driving circuit according to claim 1 comprises a plurality of switching elements for sequentially supplying a DC voltage to a plurality of armature windings of a brushless motor. , An energization control circuit that turns on and off a plurality of switching elements of the inverter circuit to perform commutation, and a chopper control that turns on and off the switching elements of the inverter circuit that are turned on by the energization control circuit by chopper control The brushless motor can be operated at a variable speed without a sensor by changing an on / off duty ratio by the chopper control circuit, and a current flowing through an armature winding of the brushless motor is further provided. Current detection circuit that converts and converts A harmonic elimination circuit that stores a detection voltage of a detection circuit in synchronization with an ON operation of a switching element of the inverter circuit by the chopper control circuit, and an averaging circuit that averages an output voltage of the harmonic elimination circuit;
And a commutation command circuit that outputs a commutation command to the conduction control circuit when the output voltage of the harmonic elimination circuit becomes a predetermined multiple of the averaging voltage of the averaging circuit.

[0010] When the brushless motor rotates, the positional relationship between the field of the motor and the armature winding being energized changes. With this change, the value of the current flowing through the armature winding also changes. The brushless motor drive circuit according to claim 1,
By determining the commutation timing by focusing on such a change in the armature current, sensorless driving of the brushless motor is enabled. Specifically, as shown in FIG. 1, when energizing the armature winding during driving of the brushless motor,
The value of the current flowing through the armature winding shows a remarkable increase twice (41, 42). Therefore, the commutation timing is determined by detecting the second remarkable current increase region 42.

That is, according to the brushless motor drive circuit of the present invention, the switching element of the inverter circuit which is turned on by the energization control circuit is chopper-controlled by the chopper control circuit. A current flows through the armature winding of the brushless motor. This armature current is converted into a voltage by a current detection circuit, detected, and output to a harmonic elimination circuit. In the harmonic elimination circuit, the output voltage of the current detection circuit is stored in synchronization with the ON operation of the switching element of the inverter circuit by the chopper control circuit, and the storage voltage (or a predetermined multiple of the storage voltage) is stored in the harmonic elimination circuit. Are output to the averaging circuit and the commutation command circuit. In the averaging circuit, the output voltage of the harmonic elimination circuit is averaged, and the averaged voltage (or a predetermined multiple of the averaged voltage) is output to the commutation instruction circuit. In the commutation command circuit, the output voltage of the harmonic elimination circuit is compared with the averaging voltage of the averaging circuit. As a result of the comparison, when the output voltage of the harmonic elimination circuit becomes a predetermined multiple of the averaging voltage of the averaging circuit, the arrival of the second remarkable current increase region 42 of the armature winding current of the brushless motor is considered. Upon determination, a commutation command is output from the commutation command circuit to the conduction control circuit. Based on this commutation command, the switching element of the inverter circuit is turned on or off by the power supply control circuit, and commutation to the brushless motor is performed. By repeating the above operation, the brushless motor is driven without any sensor.

According to a second aspect of the present invention, there is provided a brushless motor driving circuit according to the first aspect, wherein an ON duty ratio of a switching element of the inverter circuit by the chopper control circuit is less than a predetermined value to more than a predetermined value. Every time the brushless motor starts to output a commutation target voltage gradually decreasing with time from a value sufficient for generating a starting torque to the commutation command circuit in place of the averaging voltage of the averaging circuit. It has a compensation circuit.

According to a third aspect of the present invention, in the brushless motor driving circuit according to the second aspect, at least a part of the starting compensation circuit and the averaging circuit are integrally formed.

According to a fourth aspect of the present invention, there is provided a brushless motor driving circuit according to any one of the first to third aspects, wherein each of the commutation commands output from the commutation command circuit has its own commutation command. A zero reset circuit is provided for resetting the output voltage of the harmonic elimination circuit output to the circuit.

According to the fourth aspect of the present invention, the operation of the brushless motor driving circuit is the same as that of the first aspect, and the output voltage of the harmonic elimination circuit is averaged. Is higher than a predetermined multiple of the averaged voltage, a commutation command is output from the commutation command circuit. When the commutation command is input to the zero reset circuit, the zero reset circuit resets the output voltage of the harmonic elimination circuit. Therefore, for each commutation command, the output voltage of the harmonic elimination circuit is reliably made smaller than a predetermined multiple of the averaging voltage of the averaging circuit, and the commutation command is reliably reset.

[0016]

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The principle of operation of the brushless motor drive circuit according to the present embodiment is described in Japanese Patent Application No. 7-207665, and a description thereof will be omitted.

FIG. 2 is a circuit diagram of the sensorless DC brushless motor driving circuit 1 of the present embodiment. This motor drive circuit 1 is used as a sensorless drive circuit that can be operated at a variable speed, such as a small PM brushless motor for an indoor fan. The brushless motor 51 to be driven is a surface-magnet type brushless motor using a permanent magnet field as a rotor and three-phase armature windings as a stator. The motor drive circuit 1 can be used for a motor with a slip ring using a field as a stator and an armature winding as a rotor, or a brushless motor of an embedded magnet type.

The auxiliary power supply circuit 2 of the motor drive circuit 1
This circuit generates and outputs a stable 10 volt voltage from a 0 volt DC power supply 50. The 10-volt voltage generated by the auxiliary power supply circuit 2 is supplied as a drive voltage to each circuit such as the start-up compensation circuit 7, the commutation command circuit 9, and the PWM chopper control circuit 14.

The inverter circuit 3 includes a brushless motor 5
This is a circuit for sequentially switching energization of a 30 volt DC voltage to the three armature windings of three phases (U phase, V phase, W phase).
The source terminals of three P-MOS field-effect transistors Qu, Qv, and Qw as upper arm transistors are connected to the plus-side input terminal P of the DC power supply 50 of the inverter circuit 3. Are connected to the source terminals of three N-MOS field effect transistors Qx, Qy and Qz as lower arm transistors, thereby forming three arms corresponding to three-phase armature windings.

The upper arm transistors Qu to Qw have their gate terminals connected to the respective outputs u to w of the distribution circuit 12 via the resistors Ru1 to Rw1 of 10 kΩ, respectively, according to the outputs u to w of the distribution circuit 12. It is configured to be turned on and off (see FIG. 3B). A 47 kΩ resistor R for protecting and preventing floating of the gate voltage is provided between the gates and sources of the upper arm transistors Qu to Qw.
u2 to Rw2 and the upper arm transistors Qu to Qw corresponding to the lower arm transistors Qx to Qz when the lower arm transistors Qx to Qz are turned on by chopper control.
Is a short-circuit preventing capacitor (100) for preventing the lower arm transistors Qx to Qz from turning on simultaneously.
0pF) Cu to Cw are respectively connected.

On the other hand, the gate terminals of the lower arm transistors Qx to Qz are respectively connected to the respective outputs x to z of the distribution circuit 12 via the resistors Rx1 to Rz1 of 1 kΩ and connected to the inverters Ix to Iz as chopper drivers. It is connected to the output terminal of the PWM chopper control circuit 14 via the terminal. Each of the inverters Ix to Iz is composed of an open collector NPN digital transistor whose emitter terminal is connected to the ground-side input terminal N of the DC power supply 50 (that is, the circuit is grounded). Therefore, each of the lower arm transistors Qx to Qz is connected to the output x to z of the distribution circuit 12 and PW
It is turned on and off according to the output of the M chopper control circuit 14.

More specifically, a high signal is output from the outputs x to z of the distribution circuit 12, and a low signal is output from the PWM chopper control circuit 14, so that the inverter I
When a high signal is output from x to Iz, the lower arm transistors Qx to Qz are turned on. That is, FIG.
As shown in the figure, the lower arm transistors Qx to Qz
Are chopper-controlled according to the output of the PWM chopper control circuit 14.

Note that 5.6 kΩ resistors Rx2 to Rz2 for protection and prevention of gate voltage floating are connected between the gates and sources of the lower arm transistors Qx to Qz, respectively. In addition, each arm transistor Qu
Between the source and the drain of each of the arm transistors Qu to Qz, free wheel diodes Du to Dz for circulating a current caused by a back electromotive force generated in the armature winding of the brushless motor 51 when the arm transistors Qu to Qz are turned on and off. ,
Each is connected in anti-parallel.

The current detection circuit 4 includes a brushless motor 51
This is a circuit for converting the current flowing through the armature winding into a voltage and outputting the voltage to the harmonic elimination circuit 13. The current detection circuit 4 includes a 0.1Ω (2 W) shunt resistor Rs inserted between the ground-side input terminal N of the DC power supply 50 and the inverter circuit 2. Brushless motor 5
The three-phase armature current of 1 is a freewheel diode D
Except for the return currents to u to Dz, all the voltages are converted by the shunt resistor Rs. FIG. 3C shows an output voltage waveform of the current detection circuit 4 during the normal operation of the brushless motor 51.

The harmonic elimination circuit 13 stores the output voltage of the current detection circuit 4 while the lower arm transistors Qx to Qz of the inverter circuit 3 are on, in synchronization with the chopper control by the PWM chopper control circuit 14. , And a circuit for outputting to the first reduction circuit 5 and the averaging circuit 6.
That is, the output voltage of the current detection circuit 4 is output to the first reduction circuit 5 and the averaging circuit 6 after removing the harmonic components by the chopper control. The harmonic elimination circuit 13 includes an analog switch AS1, a capacitor C1, a resistor R3 functioning as an RC low-pass filter together with the capacitor C1, and a non-inverting amplifier including resistors R4, R5 and an operational amplifier OP1.

One channel terminal of the analog switch AS1 is connected to a current detection circuit 4 via a 550Ω resistor R3.
The other channel terminal is connected to a 0.1 μF capacitor C1 whose one end is grounded. The gate of the analog switch AS1 is connected to the output terminal of the PWM chopper control circuit 14 via the inverter Ia. The analog switch AS1 is turned on while the lower arm transistors Qx to Qz are turned on. Therefore, the output voltage of the current detection circuit 4 is stored in the capacitor C1 in synchronization with the ON operation of the lower arm transistors Qx to Qz by the PWM chopper control circuit 14. Therefore, the output voltage of the current detection circuit 4 from which the higher harmonic component has been removed by the chopper control is stored in the capacitor C1, in combination with the RC low-pass filter effect constituted by the resistor R3 and the capacitor C1.

The inverter Ia is composed of an open collector type NPN digital transistor whose emitter is grounded, and is connected to a 10 volt output of the auxiliary power supply circuit 2 via a 1 kΩ pull-up resistor R6. .

The non-ground terminal of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier OP1. The operational amplifier OP1 forms a non-inverting amplifier together with the resistors R4 and R5. The resistance value of the resistor R4 is 47 kΩ, and the resistance value of the resistor R5 is 10 kΩ. Therefore, the capacitor C
The output of No. 1 is amplified by a factor of about 5.7 by the non-inverting amplifiers OP1, R4 and R5, and output to the first reduction circuit 5 and the averaging circuit 6 connected to the output terminals. That is, the output voltage of the current detection circuit 4 is amplified by a factor of about 5.7 after the harmonic components are removed by the harmonic removal circuit 13 and output to the first reduction circuit 5 and the averaging circuit 6. You. FIG.
(D) shows the output voltage of the harmonic elimination circuit 13.

The non-inverting amplifiers OP1, R4, R5
Can be eliminated by increasing the resistance value of the shunt resistor Rs of the current detection circuit 4. For example, when the resistance value of the shunt resistor Rs is increased by 10 times from the current value of 0.1Ω to 1Ω, the output voltage of the current detection circuit 4 is also increased by 10 times. Therefore, in such a case, the non-inverting amplifier OP1,
The output of the capacitor C1 may be output to the first reduction circuit 5 and the averaging circuit 6 without passing through R4 and R5. In this embodiment, a resistor Rs having a small resistance value is used in order to suppress a temperature rise of the shunt resistor Rs.

The first reduction circuit 5 is a circuit for reducing the output voltage of the harmonic elimination circuit 14 by half (divided by 0.5) and outputting it to the commutation command circuit 9. It comprises two resistors R15 and R16 of 10 kΩ and a capacitor C6 of 180 pF. One end of the resistor R16 is connected to the output end of the harmonic elimination circuit 13, and the other end is connected to one end of a capacitor C6 that is grounded to form an RC low-pass filter. The RC low-pass filter removes electrostatic transfer (induction) noise and electromagnetic noise generated by chopper control, as well as harmonic components that cannot be completely removed by the harmonic removal circuit 13. The other end of the resistor R16 has a comparator CP of the commutation command circuit 9 connected thereto.
One non-inverting input terminal and one end of another resistor R15 are connected. The other end of the resistor R15 is grounded, and the resistances of the two resistors R15 and R16 are both 10 kΩ.
Therefore, the output voltage of the harmonic elimination circuit 13 is reduced to 倍 by the resistors R15 and R16, and output to the commutation command circuit 9. That is, the output voltage of the first reduction circuit 5 is instantaneous value information of the armature winding current detected by the current detection circuit 4.

The averaging circuit 6 is a circuit for averaging the output voltage of the harmonic elimination circuit 13 and outputting it to the second reduction circuit 8. A 10 kΩ resistor R13 connected to the output terminal of the harmonic elimination circuit 13, and a 100 μF electrolytic capacitor C having a negative terminal connected to the other end of the resistor R13.
4 and an integrating circuit. The capacitor C
4 is connected to a circuit grounded 1 kΩ resistor R1.
2 are connected. The averaging circuit 6 shares a part of the configuration with a starting compensation circuit 7 to be described later, thereby reducing the circuit cost.

The starting compensation circuit 7 includes a brushless motor 51
Is a circuit for outputting a commutation target voltage to the commutation command circuit 9 instead of the output of the averaging circuit 6 so that the brushless motor 51 can generate a sufficient starting torque at the time of starting. The start compensation circuit 7 operates in conjunction with the PWM chopper control circuit 14. That is, when the duty ratio of the chopper control by the PWM chopper control circuit 14 is increased from a small value less than a predetermined value to a predetermined value or more, for example, when the duty ratio is increased from less than 3% to 3% or more, The commutation target voltage is output to the commutation command circuit 9.

The start-up compensation circuit 7 has a diode D1 connected to the output terminal of the PWM chopper control circuit 14 at the cathode, and the anode of the diode D1 is connected to the anode of a 9-volt Zener diode ZD. The cathode of the Zener diode ZD is 0.1 μF
, And one end of a 56 kΩ resistor R11 and the base terminal of the transistor Q1. The emitter terminal of the transistor Q1 is connected to a capacitor C
3 and the other end of the resistor R11 and the 10 volt output of the auxiliary power supply circuit 2. The collector terminal of the transistor Q1 is connected to a circuit grounded 1 kΩ resistor R12.
Is connected to the plus side terminal of a 100 μF electrolytic capacitor C4. The minus side terminal of the electrolytic capacitor C4 has a 100 kΩ variable resistor V
R2 and one end of a 10 kΩ resistor R13.

The variable resistor VR2 constitutes a part of the start compensation circuit 7, while itself constitutes a second reduction circuit 8 for reducing the output voltages of the averaging circuit 6 and the start compensation circuit 7. The slider end of the variable resistor VR2 is connected to the inverting input terminal of the comparator CP1 of the commutation command circuit 9 as the output terminal of the second reduction circuit 8. Thus, the starting compensation circuit 7
Since the averaging circuit 6 includes the second reduction circuit 8 and shares a part (C4, R12) of the averaging circuit 6, the circuit cost can be reduced accordingly.

The reduction rate of the output voltage of the averaging circuit 6 and the starting compensation circuit 7 can be changed by adjusting the position of the slider of the variable resistor VR2. Therefore, it is needless to say that by adjusting the position of the slider, the brushless motor 51
The brushless motor drive circuit 1 can be tuned so that the motor efficiency is most improved in the normal operation region. In this embodiment, the position of the slider of the variable resistor VR2 is adjusted so that the output voltage of the averaging circuit 6 and the starting compensation circuit 7 is reduced (divided) by 0.7 times by the second reduction circuit 8. It is assumed that

The operation of the starting compensation circuit 7 will now be described with reference to FIGS. PWM chopper control circuit 1
For example, when the voltage dividing ratio of the variable resistor VR4 of FIG. 4 is less than 3% (FIG. 4A), the duty ratio of the row output of the PWM chopper control circuit 14 also becomes less than 3%. (FIG. 4B). Even if a chopper pulse having a duty ratio of less than 3% is input to the starting compensation circuit 7,
Suppressed by the capacitor C3 forming the low-pass filter, the base voltage of the transistor Q1 cannot be reduced to 9.4 volts or less (FIG. 4 (c) A). Therefore,
Since the transistor Q1 cannot be turned on (FIG. 4D), when the duty ratio of the row output of the PWM chopper control circuit 14 is less than 3%, the start compensation circuit 7
Is 0 volt (FIG. 4 (e)).
A).

From this state, the PWM chopper control circuit 1
4 is increased to, for example, 3% or more (FIG. 4A), the duty ratio of the row output of the PWM chopper control circuit 14 is also increased to 3% or more (FIG. 4 (B)). b) B). Then, the discharge of the capacitor C3 of the start-up compensation circuit 7 cannot follow the charge, the base voltage of the transistor Q1 is lowered to 9.4 volts or less (FIG. 4C), and the transistor Q1 is turned on (FIG. 4C). 4
(D) B).

When the transistor Q1 is turned on, 1 is supplied to the differentiating circuit constituted by the capacitor C4 and the variable resistor VR2.
Since a voltage of 0 volt is applied, the variable resistor VR2
A voltage wave in the form of a differential pulse that gradually decreases with time is output from the end of the slider to the commutation command circuit 9 (FIG. 4 (e) B). Thereby, the commutation target voltage at the time of starting the brushless motor 51 is set high, and an armature current sufficient to generate a starting torque at the time of starting the brushless motor 51 flows (FIG. 4 (f) B). The brushless motor 51 is started accurately.

On the other hand, when the voltage division ratio of the variable resistor VR4 of the PWM chopper control circuit 14 is reduced, the duty ratio of the row output of the PWM chopper control circuit 14 is reduced, and
The effective value of the voltage applied to the brushless motor 51 also decreases, and the rotation speed of the brushless motor 51 is reduced. When the voltage dividing ratio of the variable resistor VR4 is reduced to less than 3% (FIG. 5A), the PWM chopper control circuit 1
4 also drops to less than 3% (FIG. 5).
(B) A), the charging of the capacitor C3 of the starting compensation circuit 7 cannot follow the discharging, and the base voltage of the transistor Q1 rises to 9.4 volts or more (FIG. 5 (c) A),
The transistor Q1 is turned off (A in FIG. 5D). When the transistor Q1 is turned off, the electric charge charged in the capacitor C4 is transferred to the resistors R15, R16, R13 (total 30k).
Ω) and R12 (1 kΩ) to return to the initial state.

From this state, when the voltage dividing ratio of the variable resistor VR4 of the PWM chopper control circuit 14 is increased to 3% or more again (FIG. 5 (A) B), the PWM chopper control circuit 14
The row output duty ratio also increases to 3% or more (see FIG. 5).
(B) B), the base voltage of the transistor Q1 is lowered to 9.4 volts or less (FIG. 5 (c) B),
1 is turned on (FIG. 5 (D) B). This transistor Q
By turning on 1, the differentiated pulse-shaped voltage wave is output again from the starting compensation circuit 7 until the discharged capacitor C4 is charged again (FIG. 5 (B)).

As described above, in the starting compensation circuit 7, the voltage division ratio of the variable resistor VR4 of the PWM chopper control circuit 14 is reduced to a value less than a predetermined value (for example, less than 3%), and the brushless motor 51 being driven is temporarily stopped. Even if the rotation speed of the variable resistor VR4 is increased again to a predetermined value or more (for example, 3% or more) even if the rotation speed becomes low or the rotation speed becomes low, the start-up compensation circuit 7 is sufficient for starting the brushless motor 51 or the like. The commutation target voltage is output, and the brushless motor 51 is started properly. That is, the start compensation circuit 7 operates in conjunction with the PWM chopper control circuit 14.

The commutation command circuit 9 includes a brushless motor 51
Counting circuit 11 and the zero reset circuit 1
This is a circuit for outputting to 0. This commutation command circuit 9
Are 0.1 μF capacitors C5 and 100 for setting the pulse width of the comparator CP1, the monostable multivibrator MM, and the one-shot pulse (commutation command 56) output from the monostable multivibrator MM.
and a variable resistor VR3 of kΩ. Comparator C
The non-inverting input terminal of P1 is connected to the output terminal of the first reduction circuit 5, and the inverting input terminal is connected to the slider terminal of the variable resistor VR2, which is the output terminal of the second reduction circuit 8. The output terminal of the comparator CP1 is connected to the input terminal A of the monostable multivibrator MM. The output terminal Q of the monostable multivibrator MM is connected to the input terminal CK of the counting circuit 11 and the analog switch AS3 of the zero reset circuit 10. Connected to the gate.

In the commutation command circuit 9, the comparator CP1
Thus, the output voltage of the first reduction circuit 5 and the second reduction circuit 8
Is compared with the output voltage. As a result of the comparison, when the output voltage of the first reduction circuit 5 becomes higher than the output voltage of the second reduction circuit 8, as shown in FIG. The signal is output to the input terminal A of the MM. As a result, FIG.
As shown in (f), the monostable multivibrator M
A one-shot high signal (commutation command 56) is output from the output terminal Q of M to the counting circuit 11. The commutation command 56 is transmitted to the analog switch A of the zero reset circuit 10.
The signal is also output to the gate of S3, and while high, the analog switch AS3 is turned on.

The zero reset circuit 10 includes a commutation command circuit 9
Is a circuit for falsely resetting the output voltage of the first reduction circuit 5 to 0 volt for each commutation command 56 output from the controller, and is configured by an analog switch AS3. One channel terminal of the analog switch AS3 is connected to the output terminal of the first reduction circuit 5 and the comparator CP of the commutation command circuit 9.
1 non-inverting input terminal. On the other hand, the other channel terminal of the analog switch AS3 is grounded, and the gate of the analog switch AS3 is connected to the output terminal of the commutation command circuit 9. Therefore, the commutation command circuit 9
Outputs a high commutation command 56, the analog switch AS3 is turned on by the commutation command 56,
The output voltage of the first reduction circuit 5 is reset to 0 volt.

The counting circuit 11 counts every time the commutation command 56 output from the commutation command circuit 9 rises.
Decimal counter CT (comprising TC4017 and clear circuit)
It consists of. The output terminal of the commutation command circuit 9 is connected to the input terminal CK of the counter CT. The output terminals 0 to 5 of the counter CT are connected to the respective OR gates ORu to ORz of the distribution circuit 12 and the output terminal 6 of the counter CT. To 9 are connected to the clear terminal CLR via diodes D5 to D8, respectively. The clear terminal CLR is connected to a capacitor C7 for noise prevention and a pull-down resistor R17 whose other end is grounded. When a rising signal is input from the commutation command circuit 9 to the input terminal CK of the counter CT, the input terminal CK outputs an output terminal 0, an output terminal 1,... Counter C
A high signal is output from T.

The distribution circuit 12 is a circuit for distributing the output from the counting circuit 11 to the inverter circuit 3 and outputting the same. The distribution circuit 12 includes six OR gates ORu to ORz and three inverters Iu to Iw. I have. Inverters Iu to I
w is an open collector type NPN type digital transistor whose emitter terminal is grounded to the circuit, and has a high withstand voltage. It should be noted that each of the inverters Iu to Iw is replaced with a digital transistor, and N
-It may be constituted by a MOS field effect transistor. Moreover, you may comprise using a photocoupler etc. as needed.

The input terminal of the OR gate ORu of the distribution circuit 12 is connected to the output terminals 0 and 1 of the counter CT, and the output terminal is connected to the input terminal of the inverter Iu. The input terminal of the OR gate ORv is connected to the output terminals 2 and 3 of the counter CT, and the output terminal is connected to the input terminal of the inverter Iv. The input terminal of the OR gate ORw is a counter C
It is connected to the output terminals 4 and 5 of T, and its output terminal is connected to the input terminal of the inverter Iw. The input terminal of the OR gate ORx is connected to the output terminals 3 and 4 of the counter CT, the input terminal of the OR gate ORy is connected to the output terminals 5 and 0 of the counter CT, and the input terminal of the OR gate ORz is connected to the counter C
It is connected to the output terminals 1 and 2 of T. Inverter Iu ~
Output terminals of Iw and the OR gates ORx to ORz are connected to resistors R1u to R1z connected to gate terminals of the field effect transistors Qu to Qz of the inverter circuit 3, respectively. FIG. 6 shows the relationship between the input and output of the distribution circuit 12, and
The three phases (U
3 shows the directions of the currents flowing through the armature windings (phase, V-phase, and Z-phase).

The PWM chopper control circuit 14 is a circuit for outputting a chopper-shaped rectangular wave to the lower arm transistors Qx to Qz of the inverter circuit 3 to control the brushless motor 51 chopper. By changing (controlling) the duty ratio of the rectangular wave output from the PWM chopper control circuit 14, the effective voltage applied to the brushless motor 51 is changed (controlled).
The variable speed operation 1 is performed.

The PWM chopper control circuit 14 has a comparator CP2.
Are connected to a non-inverting input terminal of a resistor R19 of 100 kΩ,
The resistor R20 of 0 kΩ and the anode of the diode D9 are connected. The other end of the resistor R20 is grounded, and the other end of the resistor R19 is connected to the 10 volt output of the auxiliary power supply circuit 2. The cathode of the diode D9 is
1 whose other end is connected to the 10 volt output of the auxiliary power circuit 2
a resistor R18 of kΩ, an output terminal of the comparator CP2,
It is connected to a resistor R21 of 82 kΩ and a cathode of a diode D10. The other end of the resistor R21 and the anode of the diode D10 are connected to a 180 pF capacitor C8 grounded to the circuit and an inverting input terminal of the comparator CP2.

The inverting input terminal of the comparator CP2 is connected to the non-inverting input terminal of the comparator CP3. On the other hand, the inverting input terminal of the comparator CP3 is connected to the positive terminal of a 10 μF electrolytic capacitor C9 whose negative terminal is grounded and a resistor R22 of 10 kΩ. The other end of the resistor R22 is a variable resistor VR of 5 kΩ.
2.2, one end of the variable resistor VR4 is connected to the 10 volt output of the auxiliary power supply circuit 2.
The other end is connected to a kΩ resistor R23 and the other end is connected to a circuit grounded 560Ω resistor R24.

Further, the output terminal of the comparator CP3 is 1
It is connected to a 10 volt output of the auxiliary power supply circuit 2 via a pull-up resistor R25 of kΩ, and serves as an output terminal of the PWM chopper control circuit 14 as an inverter Ia, Ix to
The input terminal of Iz and the input terminal of the starting compensation circuit 7 are connected.

From the PWM chopper control circuit 14,
A rectangular wave of about 20 kHz is output. The duty ratio of the rectangular wave is changed by changing the position of the slider of the variable resistor VR4. Even when the position of the slider of the variable resistor VR4 is suddenly changed, the duty ratio of the rectangular wave output from the PWM chopper control circuit 14 is gradually changed without sudden change by the action of the capacitor C9. Go. Therefore, even when the position of the slider is suddenly changed, the rotation speed of the brushless motor 51 is gradually changed, and the brushless motor 51 is driven smoothly.

Next, the operation of the brushless motor drive circuit 1 configured as described above will be described. When a DC voltage of 30 volts is applied from DC power supply 50, auxiliary power supply circuit 2
Supplies a stabilized voltage of 10 volts to each circuit. The counting circuit 11 receiving the driving voltage of 10 volts from the auxiliary power supply circuit 2 outputs, for example, “10000” from the output terminals 0 to 5.
A signal “0” is output to the distribution circuit 12. Upon receiving this, the distribution circuit 12 outputs “011010” to the inverter circuit 3 as an output of “uvwxyz” (FIG. 6).
reference). In the inverter circuit 3, the upper arm transistor Qu is turned on by the signal, and the lower arm transistor Qy is turned on and off based on the chopper-shaped rectangular wave output from the PWM chopper control circuit 14. As a result, U of the armature winding of the brushless motor 51
The armature current flows from the phase to the V phase, and the brushless motor 51
Is started. The armature current is accompanied by a substantially triangular pulsation (harmonic component) that increases when the lower arm transistor Qy is on and decreases when the lower arm transistor Qy is off.

The armature current flowing through the brushless motor 51 is detected by the shunt resistor Rs of the current detection circuit 4, converted into a voltage, and output to the harmonic elimination circuit 13. The output voltage of the current detection circuit 4 is synchronized by the harmonic elimination circuit 13 with the output of the PWM chopper control circuit 14 to output the lower arm transistor Qy of the inverter circuit 3.
Is stored in the capacitor C1 while is turned on.
By storing the output voltage of the current detection circuit 4 in synchronization with the chopper control in this manner, harmonic components due to the chopper control are removed. The output voltage of the current detection circuit 4 stored in the capacitor C1 is amplified by a factor of about 5.7, and then the output voltage of the current reduction circuit 4 is reduced to 1 /
It is reduced by a factor of 2 (divided by a factor of 0.5) and output to the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9.

On the other hand, in the starting compensation circuit 7, when the duty ratio of the row output of the rectangular wave output from the PWM chopper control circuit 14 reaches a predetermined value or more (for example, 3% or more) (FIG. 4B). Then, the transistor Q1 is turned on (FIG. 4 (D) B). When the transistor Q1 is turned on, a differentiating circuit composed of the capacitor C4 and the variable resistor VR2 is operated, and a gradually decreasing differential pulse-like voltage is generated.
Starting compensation circuit 7 (second reduction circuit 8) to commutation command circuit 9
Is output to the inverting input terminal of the comparator CP1 of FIG.
(E) B).

In the commutation command circuit 9, the comparator CP1
As a result, the output voltage of the first reduction circuit 5 and the output voltage of the second reduction circuit 8 are compared. As a result of the comparison, the first reduction circuit 5
Until the output voltage of the second reduction circuit 8 becomes higher than the output voltage of the second reduction circuit 8. Commutation command 56
The same phase of the armature winding (eg,
Since energization from the U-phase to the V-phase is continued, a sufficient armature current is supplied to the brushless motor 51 to generate a starting torque, and the field rotor of the brushless motor 51 gradually starts rotating. .

The armature current value of the brushless motor 51 changes with the rotation of the field. The change in the armature current value is detected by the shunt resistor Rs of the current detection circuit 4 and stored in the harmonic removal circuit 13 in synchronization with the output of the PWM chopper control circuit 14. The stored output voltage of the current detection circuit 4 is approximately 5.7 in the harmonic elimination circuit 13.
It is amplified by a factor of 2 and then further reduced by 1
It is reduced by a factor of 2 (divided by a factor of 0.5) and output to the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 as instantaneous value information of the armature current. As a result, when the output voltage of the first reduction circuit 5 becomes higher than the output voltage of the second reduction circuit 8, the high signal 55 is output from the comparator CP1 of the commutation command circuit 9, and the one-shot multivibrator MM outputs a one-shot signal. The commutation command 56 is output to the counting circuit 11.

The counter CT of the counting circuit 11 to which the commutation command 56 is input updates the output state of the output terminals 0 to 5 in response to the rise of the pulse of the commutation command 56, and
Output to For example, if the output state of the output terminals 0 to 5 before the commutation command is “100000”, the output state is updated to “010000” by the commutation command 56 (see FIG. 6). As a result, each output of “uvwxyz” of the distribution circuit 12 becomes “01”
1001 ”, the field effect transistors Qu and Qz are turned on instead of the field effect transistors Qu and Qy that were turned on in the inverter circuit 3, and the armature current of the brushless motor 51 flowing from the U phase to the V phase is reduced. It is commutated from the U phase to the W phase.

On the other hand, the commutation command 56 output from the commutation command circuit 9 is also output to the zero reset circuit 10, during which the analog switch AS3 is turned on. When the analog switch AS3 of the zero reset circuit 10 is turned on, the first
The output voltage of the reduction circuit 5 is reset to 0 volt. This ensures that the output voltage of the comparator CP1 to the non-inverting input terminal is lower than the output voltage to the inverting input terminal, so that the output of the comparator CP1 of the commutation command circuit 9 switches from high to low in a short time. One pulse 5
5 (FIG. 3E). The monostable multivibrator MM of the commutation command circuit 9 that outputs the commutation command 56 in response to the single pulse 55 changes the commutation command 56 from high when a predetermined time determined by the variable resistor VR3 and the capacitor C5 has elapsed. The state is switched to low, and the state shifts to the state of waiting for the generation of the next commutation command 56.

The second reduction circuit 8 outputs to the commutation command circuit 9 the larger one of the output voltage of the averaging circuit 6 and the output voltage of the start-up compensation circuit 7. Therefore, the output of the second reduction circuit 8 switches from the output voltage of the starting compensation circuit 7 to the output voltage of the averaging circuit 6 at a certain point in time. After this switching, the output voltage of the averaging circuit 6 is reduced to the output voltage of the second reduction circuit 8 (that is, This is continuously output to the commutation command circuit 9 as the target voltage).

In the present embodiment, the reduction rate of the first reduction circuit 5 is 0.5 times and the reduction rate of the second reduction circuit 8 is 0.7 times. When the output voltage of the first reducing circuit 5 becomes 1.4 times or more the output voltage of the averaging circuit 6, the high signal 55 is output to the monostable multivibrator MM (FIG. 3 (e)). As a result, the one-shot commutation command 56
Is output to the counting circuit 11 (and the zero reset circuit 10) (FIG. 3 (f)), and the commutation of the brushless motor 51 is performed by the counting circuit 11, the distribution circuit 12, and the inverter circuit 3. By repeating this commutation operation, the brushless motor 51 is rotated.

As described above, according to the brushless motor drive circuit 1, when the armature current of the brushless motor 51 becomes 1.4 times or more the voltage averaged by the averaging circuit 6, the commutation command 56 is issued. The commutation operation is performed upon output. Therefore, without using a rotor magnetic pole position sensor such as a Hall element or a shaft encoder, the second current increase region 42 of the armature current is detected, and the commutation operation is performed at that timing, so that the brushless motor 51 is smoothly operated. Can be driven.

In particular, in the motor drive circuit 1 of this embodiment,
Harmonic components accompanying the chopper control are not averaged and removed by a low-pass filter, but are removed by a harmonic removing circuit 1.
3 is removed by operating in synchronization with the chopper control. Therefore, even when the duty ratio of the chopper control is small, it is possible to detect the armature current while keeping it at a normal level. Therefore, even during low-speed operation with a small duty ratio, the commutation operation can be performed at an appropriate timing, so that the duty ratio is 3% to 100%.
%, The brushless motor 51 can be operated at a variable speed.

Next, a modification of the first embodiment will be described with reference to FIGS. The same portions as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 7 shows a brushless motor drive circuit 100 according to the second embodiment. The brushless motor drive circuit 100 according to the second embodiment includes a PWM chopper control circuit 1
4, the output voltage of the harmonic elimination circuit 13 is averaged in synchronization with the chopper control of FIG.
4 is configured such that the lower the duty ratio is, the longer the averaging process time constant of the averaging circuit 5 is, and the accuracy of the result of averaging the armature current in the low rotation range is improved to stabilize the brushless motor 51. That is, it can be driven. For this reason, in the brushless motor drive circuit 100 of the second embodiment, the averaging circuit 101 and the second reduction circuit 102 of the brushless motor drive circuit 1 of the first embodiment described above are changed. Also, the starting compensation circuit 10
3, and a priority circuit 104 is added.

The averaging circuit 101 synchronizes the chopper control of the PWM chopper control circuit 14 with the harmonic elimination circuit 13.
Is a circuit for averaging the output voltages of the first and second output circuits and outputting the result to the second reduction circuit 102. The averaging circuit 101 includes an analog switch AS2, a resistor R101 of 10 kΩ,
μF electrolytic capacitor C10. One channel terminal of the analog switch AS2 is connected to the output terminal of the harmonic elimination circuit 13, and the other channel terminal is connected to a resistor R.
101 is connected to one end. The other end of the resistor R101 is connected to a positive terminal of the capacitor C10, and a negative terminal of the capacitor C10 is grounded.
The gate of the analog switch AS2 is a harmonic elimination circuit 1
3 analog switch AS1, the inverter Ia
The output voltage of the harmonic elimination circuit 13 can be averaged in synchronization with the harmonic elimination circuit 13 and the chopper control of the PWM chopper control circuit 14. Therefore, the accuracy of the result of averaging the armature current in the low rotation range is improved, and the brushless motor 51 is improved.
Can be driven stably.

The second reduction circuit 102 comprises a variable resistor VR10 of 100 kΩ. One end of the variable resistor VR10 is connected to a capacitor C1 which is an output terminal of the averaging circuit 101.
0 is connected to the positive terminal and the other end is grounded. The slider end of the variable resistor VR10 is connected to the inverting input terminal of the comparator CP1 of the commutation command circuit 9 as the output terminal of the second reduction circuit 102. In the present embodiment, the averaging circuit 101 is used by the second reduction circuit 102.
The slider position of the variable resistor VR10 is adjusted so that the output voltage of the variable resistor VR10 is reduced (divided) by 0.7 times.

When the brushless motor 51 is started, the start compensation circuit 103 generates a second starting circuit 102 so that the brushless motor 51 can generate a sufficient starting torque.
Is a circuit for outputting a commutation target voltage to the commutation command circuit 9 in place of the output of. This start compensation circuit 103
It operates in conjunction with the PWM chopper control circuit 14. That is, when the duty ratio of the chopper control output from the PWM chopper control circuit 14 is increased from a small value less than the predetermined value to a predetermined value or more, for example, in this embodiment, the duty ratio of the row output is about 3. Less than 8% to about 3.8%
In this case, the starting compensation circuit 103 outputs the commutation target voltage to the commutation command circuit 9 via the priority circuit 104. The above-mentioned duty ratio of about 3.8% corresponds to the resistances R103 (390Ω) and R104 (10k
Ω).

The starting compensation circuit 103 includes a 100 kΩ resistor R 1 connected to the output terminal of the PWM chopper control circuit 14.
02, and the other end of the resistor R102 is 0.1
One end of the μF capacitor C11 and the inverting input terminal of the operational amplifier OP11 are connected. The other end of the capacitor C11 is connected to the 10 volt output of the auxiliary power supply circuit 2. The non-inverting input terminal of the operational amplifier OP11 has a 390Ω resistor R103 having one end connected to the 10 volt output of the auxiliary power supply circuit 2, and a 10kΩ resistor R10 having one end grounded.
104. Also, the operational amplifier OP11
Output terminal is connected to the anode of the diode D101 and 10 μm.
F is connected to the positive terminal of the electrolytic capacitor C12. The cathode of the diode D101 is the auxiliary power circuit 2
, While the electrolytic capacitor C
12 has a 100 kΩ resistor R105 grounded to the circuit and a diode D10 grounded to the anode.
2 and one end of a 500 kΩ variable resistor VR11. The other end of the variable resistor VR11 is connected to the anode of the diode D104, which is the input terminal of the priority circuit 104, as the output terminal of the starting compensation circuit 103.

Here, the operation of the starting compensation circuit 103 will be described with reference to FIGS. The voltage dividing ratio of the variable resistor VR4 is set low (FIG. 8A), and the duty ratio of the row output of the PWM chopper control circuit 14 is about 3.8.
% (FIG. 8 (b) A), the PWM
The chopper pulse output from the chopper control circuit 14 is suppressed by the capacitor C11 constituting the low-pass filter of the starting compensation circuit 103, and the operational amplifier OP11
The input voltage to the inverting input terminal of resistors R103 and R10
4, the output voltage of the operational amplifier OP11 becomes 0 volts (A in FIG. 8 (d)). Therefore, when the duty ratio of the row output of the PWM chopper control circuit 14 is less than about 3.8%, the start compensation circuit 103
Is 0 volt (FIG. 8 (e)).
A), the brushless motor 51 is in a stopped state.

In this state, when the voltage dividing ratio of the variable resistor VR4 is increased (B in FIG. 8A) and the duty ratio of the row output of the PWM chopper control circuit 14 is increased to about 3.8% or more (FIG. b) B), the discharge of the capacitor C11 of the start compensation circuit 103 cannot follow the charge, and the input voltage to the inverting input terminal of the operational amplifier OP11 drops to about 9.62 volts or less (FIG. 8C). As a result, the input voltage to the non-inverting input terminal of the operational amplifier OP11 becomes higher than the input voltage to the inverting input terminal, and the output voltage of the operational amplifier OP11 rises from 0 volts to about 8.5 volts (FIG. 8).
(D) B). Here, about 8.5 volts, the operational amplifier can output only up to 1.5 volts or less of the power supply voltage due to its characteristics. This is because, in this embodiment, the power supply voltage of the operational amplifier OP11 is 10 volts, so that 10 volts−1.5 volts = 8.5 volts. The value of 1.5 volts naturally depends on the type of the operational amplifier.

When the output voltage of the operational amplifier OP11 is about 8.5
When the voltage becomes volts, a voltage of about 8.5 volts is applied to a differentiating circuit composed of the capacitor C12 and the resistor R105. Therefore, the variable resistor VR1 is output from the starting compensation circuit 103.
1, a differential pulse-like voltage wave that gradually decreases with time from a voltage value of slightly less than 8.5 volts obtained by subtracting the voltage drop is output to the priority circuit 104 (FIG. 8).
(E) B). Note that the capacitance of the capacitor C12 is 10 μm.
F, since the resistance value of the resistor R105 is 100 kΩ, this voltage wave decreases to about 37% of its peak value after one second (10 μF × 100 kΩ = 1 s).

The output voltage of starting compensation circuit 103 output to priority circuit 104 is output to commutation command circuit 9 as a commutation target voltage. Therefore, the commutation target voltage at the time of starting the brushless motor 51 is set high, so that at the time of starting the brushless motor 51, a sufficient armature current flows to generate a starting torque (FIG. 8 (f) B). , The brushless motor 51 is started properly.

On the other hand, if the voltage dividing ratio of the variable resistor VR4 is reduced while the brushless motor 51 is rotating (FIG. 9A),
As the duty ratio of the row output of the PWM chopper control circuit 14 decreases, the effective value of the voltage applied to the brushless motor 51 also decreases, and the brushless motor 51 is decelerated. When the duty ratio of the row output of the PWM chopper control circuit 14 drops to less than about 3.8% (A in FIG. 9B), the capacitor C11 of the starting compensation circuit 103
Charging cannot follow the discharging, and the operational amplifier OP1
The input voltage to the inverting input terminal of No. 1 rises to 9.62 volts, which is the input voltage to the non-inverting input terminal (FIG. 9C).
A), the output voltage of the operational amplifier OP11 drops from about 8.5 volts to 0 volt (FIG. 9 (d) A). When the output voltage of the operational amplifier OP11 becomes 0 volt, the capacitor C
The charge that has been charged in 12 is quickly discharged through the diode D102 and the operational amplifier OP11, and returns to the initial state.

From this state, the voltage dividing ratio of the variable resistor VR4 is increased again (FIG. 9A), and when the duty ratio of the row output of the PWM chopper control circuit 14 becomes about 3.8% or more (FIG. 9A). (B) B), the input voltage to the inverting input terminal of the operational amplifier OP11 drops to 9.62 volts or less (FIG. 9)
(C) B), the output voltage of the operational amplifier OP11 is about 8.5
It rises to a bolt (FIG. 9D). As a result, until the discharged capacitor C12 is recharged, a voltage pulse in the form of a differentiated pulse is output again from the starting compensation circuit 103 (FIG. 9 (e) B).

When the DC power supply 50 is turned off during the operation of the brushless motor 51, the charge stored in the capacitor C12 is rapidly discharged through the diodes D101 and D102, and returns to the initial state. Therefore,
Even when the DC power supply 50 is turned on again immediately after it is turned off, the start-up compensation circuit 103 can operate normally and the brushless motor 51 can be started up smoothly.

The priority circuit 104 outputs the output of the averaging circuit 101 reduced by the second reduction circuit 102, ie, the commutation target voltage at the time of steady operation, and the output of the start compensation circuit 103, ie, the commutation at the time of startup. This is a circuit for outputting the larger one of the target voltage and the output voltage to the commutation command circuit 9, and is constituted by a diode D103.
The anode of the diode D103 is the starting compensation circuit 1
03 is connected to the output terminal of the second reduction circuit 10
2 and the comparator CP of the commutation command circuit 9
1 inverting input terminal. Therefore, priority circuit 1
04, the second reduction circuit 102 and the starting compensation circuit 103
Is output to the commutation command circuit 9 as the commutation target voltage.

As described above, according to the brushless motor drive circuit 100 of the second embodiment, the harmonic elimination circuit 1 is synchronized with the chopper control of the PWM chopper control circuit 14.
3 is averaged, and the commutation timing is determined based on the averaged armature current voltage value. Therefore, the lower the rotation speed, the longer the armature current averaging process time becomes. Thus, the brushless motor 51 can be driven more stably by improving the accuracy of the conversion result.

FIG. 10 shows a brushless motor drive circuit 200 according to the third embodiment. The brushless motor drive circuit 200 of the third embodiment is configured so that the brushless motor 51 can be driven stably even when the armature current is small. Specifically, the output voltage of the harmonic elimination circuit 13 is output to the commutation command circuit 9 without being reduced (divided), and the output voltage of the averaging circuit 111 is amplified.
2 and output to the commutation command circuit 9, and the two are compared by the commutation command circuit 9 to generate a commutation command 56. Therefore, in the brushless motor drive circuit 200 of the third embodiment, the zero reset circuit 110, the averaging circuit 111, the amplifying circuit 112, and the starting compensation circuit 113 of the brushless motor drive circuit 1 of the first embodiment described above.
Has been changed.

The zero reset circuit 110 is provided for each commutation command 56 output from the commutation command circuit 9,
3 is a circuit for artificially resetting the output voltage at 0 to 0 volts, and includes a resistor R16 of 10 kΩ, a capacitor C6 of 180 pF, and an analog switch AS3. One end of the resistor R16 is connected to the output terminal of the harmonic elimination circuit 13, and the other end of the resistor R16 is connected to one end of a capacitor C6 that is grounded to form an RC low-pass filter. The RC low-pass filter removes electrostatic transfer (induction) noise and electromagnetic noise generated by chopper control, as well as harmonic components that cannot be completely removed by the harmonic removal circuit 13.

The other end of the resistor R16, that is, the output end of the RC low-pass filter is connected to the analog switch A
It is connected to one channel terminal of S3 and one non-inverting input terminal of the comparator CP1, which is one input terminal of the commutation command circuit 9. The other channel terminal of the analog switch AS3 is grounded, and the gate of the analog switch AS3 is connected to the output terminal of the commutation command circuit 9. Therefore, the high commutation command 56 is transmitted from the commutation command circuit 9.
Is output, the analog switch AS3 is turned on by the commutation command 56, and the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 is grounded. That is, 0
It is fake reset to Bolt.

The averaging circuit 111 includes the harmonic elimination circuit 13
Is a circuit for averaging the output voltage of the amplifier circuit and outputting the result to the amplifier circuit 112. It comprises an integrating circuit of a resistor R111 of 100 kΩ connected to the output terminal of the harmonic elimination circuit 13 and a 10 μF electrolytic capacitor C13 having a positive terminal connected to the other end of the resistor R111. The negative terminal of the capacitor C13 is grounded.

The amplifying circuit 112 amplifies the voltage value averaged by the averaging circuit 111 and outputs the amplified voltage value to the commutation command circuit 9. The amplifier circuit 112 includes an operational amplifier O
A non-inverting amplifier composed of P12 and two resistors R112 and R113, and a variable resistor VR11 of 100 kΩ for reducing the output of the non-inverting amplifier to 1 or less. A commutation target voltage is output from a slider end of the variable resistor VR11.

The non-inverting operational amplifier OP12 has a non-inverting input terminal connected to the positive terminal of a capacitor C13, which is the output terminal of the averaging circuit 111, and an operational amplifier OP12.
The output terminal of P12 has a resistor R112 and a variable resistor VR11.
Are connected at one end. The other end of the resistor R112 is connected to the inverting input terminal of the operational amplifier OP12 and one end of the resistor R113, and the other end of the resistor R113 is grounded.

The two resistors R112 and R1 of the non-inverting amplifier
13 have the same resistance value of 10 kΩ. Therefore, the output of the averaging circuit 111 is
12, R112 and R113 substantially double the amplification.
The output of the averaging circuit 111, which has been amplified twice, is reduced to one or less by the variable resistor VR11.
Output to In this embodiment, the non-inverting amplifier OP12,
The output of the averaging circuit 111, which is amplified twice by R112 and R113, is reduced (divided) by 0.7 times by the variable resistor VR11. Therefore, the output of the averaging circuit 111 is amplified by a factor of 1.4 as a whole of the amplifier circuit 112.

It is to be noted that the variable resistor VR1
By adjusting the position of the first slider, the amplification factor of the entire amplification circuit 112 can be changed. Therefore, the amplification factor is changed according to the use condition, and the motor efficiency is most improved in the normal operation region of the brushless motor 51. It can be tuned like this.

When the brushless motor 51 starts, the start compensation circuit 113 replaces the output of the averaging circuit 111 amplified by the amplifier circuit 112 in order to enable the brushless motor 51 to generate a sufficient starting torque. This is a circuit for outputting the current target voltage to the commutation command circuit 9. The start compensation circuit 113 operates according to the position of the slider of the variable resistor VR4 of the PWM chopper control circuit 14. When the position of the slider of the variable resistor VR4 is changed, PWM
The duty ratio of the chopper control output from the chopper control circuit 14 is changed. That is, the starting compensation circuit 11
3 operates in conjunction with the PWM chopper control circuit 14.

The starting compensation circuit 113 includes an operational amplifier OP1
And a non-inverting input terminal of the operational amplifier OP13, a PWM connected to a slider end of the variable resistor VR4.
The other end of the resistor R22 of the chopper control circuit 14 is connected. The other end of the resistor R22 has a PWM chopper control circuit 1
Since a voltage that determines the duty ratio of the chopper control of No. 4 is output, this voltage is input to the operational amplifier OP13, so that the start compensation circuit 113 is linked with the change of the duty ratio of the chopper control of the PWM chopper control circuit 14 It can work.

The inverting input terminal of the operational amplifier OP13 has a resistor R114 of 18 kΩ connected to the 10 volt output of the auxiliary power supply circuit 2 and a resistor R11 of 1.5 kΩ grounded to the circuit.
5 are connected. A voltage of about 0.77 volts is input to the inverting input terminal of the operational amplifier OP13 by the resistors R114 and R115. A variable resistor VR12 of 100 kΩ is connected to the output terminal of the operational amplifier OP13, and the other terminal of the variable resistor VR12 is connected to the plus terminal of the 100 μF electrolytic capacitor C14 and the anode of the diode D111. The cathode of the diode D111 is connected to the 10 volt output of the auxiliary power supply circuit 2. The negative terminal of the capacitor C14 is connected to the cathode of the diode D112 whose anode is grounded, and the amplifier circuit 1
It is connected to one end of 12 variable resistors VR11.

Here, the operation of the starting compensation circuit 113 will be described. The voltage dividing ratio of the variable resistor VR4 is set low,
When the duty ratio of the row output of the PWM chopper control circuit 14 is less than a predetermined value (for example, less than 3%), the input voltage to the non-inverting input terminal of the operational amplifier OP13 is applied to the inverting input terminal by the resistors R114 and R115. The input voltage is about 0.77 volts or less. In such a case, the output voltage of the operational amplifier OP13 is 0 volt. In this state, the brushless motor 51 is in a stopped state.

From this state, the PWM chopper control circuit 1
4 has a duty ratio of a predetermined value or more (for example, 3%
If the voltage dividing ratio of the variable resistor VR4 is increased in order to increase the voltage, the input voltage to the non-inverting input terminal of the operational amplifier OP13 increases to about 0.77 volt or more. As a result, the input voltage to the inverting input terminal becomes higher than the input voltage to the non-inverting input terminal, and the output voltage of the operational amplifier OP13 rises from 0 volts to about 8.5 volts. When the output voltage of the operational amplifier OP13 becomes approximately 8.5 volts, the variable resistor VR1
2. A voltage of about 8.5 volts is applied to a differentiating circuit composed of the capacitor C14 and the variable resistor VR11. Therefore, a differential pulse-like voltage wave that gradually decreases with time is output from the starting compensation circuit 113 to the commutation command circuit 9 via the variable resistor VR11. Therefore, since the commutation target voltage at the time of starting the brushless motor 51 is set high, at the time of starting the brushless motor 51, a sufficient armature current flows to generate a starting torque, and the brushless motor 51 starts accurately. It is done.

On the other hand, when the voltage dividing ratio of the variable resistor VR4 is reduced while the brushless motor 51 is rotating, the duty ratio of the row output of the PWM chopper control circuit 14 is reduced, and the effective value of the voltage applied to the brushless motor 51 is reduced. Is also lowered, and the brushless motor 51 is decelerated.
When the duty ratio of the row output of the PWM chopper control circuit 14 falls below a predetermined value (for example, less than 3%), the input voltage to the non-inverting input terminal of the operational amplifier OP13 is the input voltage to the inverting input terminal. The voltage becomes 0.77 volts or less, and the output voltage of the operational amplifier OP13 drops from approximately 8.5 volts to 0 volt. When the output voltage of the operational amplifier OP13 becomes 0 volt, the charge stored in the capacitor C14 is discharged through the diode D112, the variable resistor VR12, and the operational amplifier OP13, and returns to the initial state.

From this state, when the voltage dividing ratio of the variable resistor VR4 is increased again and the duty ratio of the row output of the PWM chopper control circuit 14 becomes a predetermined value or more (for example, 3% or more), the non-inverting input terminal of the operational amplifier OP13. Input voltage rises to 0.77 volts or more, and the output voltage of the operational amplifier OP13 rises to approximately 8.5 volts. As a result, until the capacitor C14 is recharged, the starting compensation circuit 113
Output a differential pulse-like voltage wave again. Therefore,
The commutation target voltage at the time of starting the brushless motor 51 is set high, and the brushless motor 51 is started accurately.

When the DC power supply 50 is turned off during the operation of the brushless motor 51, the electric charge stored in the capacitor C14 is changed to the diodes D112 and D11.
1 rapidly discharges and returns to the initial state. Therefore, when the DC power supply 50 is turned on immediately after the power is turned off, the start compensation circuit 113 is operated normally, and the brushless motor 51 can be started smoothly.

As described above, the start compensation circuit 113 of the present embodiment is used.
, The variable resistance V of the PWM chopper control circuit 14
Even if the voltage division ratio of R4 is lowered and the brushless motor 51 being driven is stopped or rotated at a low speed, then the voltage division ratio of the variable resistor VR4 is increased to start the brushless motor 51 from the start compensation circuit 113. A sufficient commutation target voltage can be output. Therefore, even in such a case, the brushless motor 51 can be started accurately. Thus, the starting compensation circuit 113
It is configured to operate in conjunction with the PWM chopper control circuit 14.

As described above, according to the brushless motor drive circuit 200 of the third embodiment, the voltage value of the armature current detected by the current detection circuit 4 and amplified by the harmonic elimination circuit 13 is reduced. Without being output to the averaging circuit 111 and the commutation command circuit 9, and the output voltage of the averaging circuit 111 is further amplified by the amplifier circuit 112 and output to the commutation command circuit 9. The magnitude of both is compared by the commutation command circuit 9 and the commutation command 5
6 is generated. Therefore, even when the armature current is very small, the commutation timing can be accurately detected, and the brushless motor 51 can be driven stably.

Next, referring to FIG. 11, inverter Ix
A modified example of the chopper driver composed of .about.Iz will be described. The chopper driver shown in FIG. 11 replaces three inverters Ix to Iz with one inverter (NPN).
Digital transistor) Ib and three diodes D
15, D16, and D17 to reduce the cost of the circuit. The output terminal of the inverter Ib is 3
The anodes of the diodes D15 to D17 are connected to the gate terminals of the lower arm transistors Qx to Qz, respectively. Since the input terminal of the inverter Ib is connected to the output terminal of the PWM chopper control circuit 14,
When a chopper pulse is output from the M chopper control circuit 14, the lower arm transistors Qx to Qz turned on by the distribution circuit 12 are chopper controlled in synchronization with the output.

FIGS. 12 and 13 show modified examples of the distribution circuit. Conventionally, as described in the section of the prior art, focusing on the correlation between the speed electromotive force generated in the armature winding of the rotating motor and the position of the field, the commutation timing of the motor is determined by the speed electromotive force. The brushless motor 5
The three-phase armature winding No. 1 could not be energized by 180 degrees. However, since the brushless motor drive circuits 1, 100, and 200 of the first to third embodiments focus on changes in the armature current to drive the brushless motor 51 sensorlessly, it is possible to conduct electricity by 180 degrees. . By performing the 180-degree energization instead of the 120-degree energization, the rotation speed and output of the motor can be improved.

FIG. 12 shows a circuit diagram of the distribution circuit 30 in the case where 180-degree conduction is performed, and FIG.
The relationship of the direction of current flowing through the armature winding of the brushless motor 51 at each output of the distribution circuit 30 is shown. The resistance value of each resistor in the distribution circuit 30 of FIG.
Each was 10 kΩ, and the capacitance of each capacitor was 1000 pF. Also, the distribution circuit is not fixed to 120-degree conduction or 180-degree conduction, but the output of the distribution circuit can be switched between 120-degree conduction and 180-degree conduction in accordance with the driving state of the brushless motor 51. You may do it.

The present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Can easily be inferred.

For example, in the brushless motor drive circuit 1 of the present embodiment, the shunt resistor R
s is inserted into the ground line of the DC link so that one shunt resistor Rs detects all three-phase armature currents. However, a current detection circuit that can detect an armature current may be provided at a position other than the ground line of the DC link. Alternatively, three current detection circuits may be separately provided so as to individually detect three-phase armature currents.

In this embodiment, in order to reduce power consumption,
Lower arm transistors Qx to Q for which chopper control is performed
A field effect transistor was used not only for z but also for the upper arm transistors Qu to Qw. However, since the high-speed operation is not required for the upper arm transistor in which the chopper control is not performed, the circuits 1, 100, 2
In order to reduce the cost of 00 and improve the availability of parts, a junction type PNP transistor may be used instead of the field effect transistor.

[0103]

According to the brushless motor drive circuit of the first aspect, the harmonic elimination circuit stores the output voltage of the current detection circuit in synchronization with the ON operation of the switching element of the inverter circuit by the chopper control circuit. The armature current converted into a voltage can be detected by removing harmonic components by the chopper control. The commutation command is output based on the stored voltage of the harmonic elimination circuit from which the harmonic components have been eliminated. Flow operation can be performed. Accordingly, even in such a case, there is an effect that the brushless motor can be driven at a variable speed without a sensor.

According to the brushless motor drive circuit of the second aspect, in addition to the effect of the brushless motor drive circuit of the first aspect, the ON duty ratio of the chopper control circuit is reduced to less than a predetermined value, and the brushless motor is driven. When the on-duty ratio is increased to a predetermined value or more even after the motor stops or rotates at a low speed, the starting torque is transmitted from the start compensation circuit to the commutation command circuit instead of the averaging voltage of the averaging circuit. Is output as the commutation target voltage. Therefore, there is an effect that even a brushless motor once stopped or rotated at a low speed can be restarted accurately.

According to the brushless motor driving circuit according to the third aspect, in addition to the effect of the brushless motor driving circuit according to the second aspect, at least a part of the starting compensation circuit and the averaging circuit are integrally formed. This has the effect that the cost of the brushless motor drive circuit can be reduced as compared with the case where both circuits are provided separately.

According to the brushless motor drive circuit of the fourth aspect, in addition to the effect of the brushless motor drive circuit of any one of the first to third aspects, in addition to the commutation command, the output voltage of the harmonic elimination circuit is averaged. It is output when the averaged voltage of the conversion circuit becomes a predetermined multiple or more. When the commutation command is input to the zero reset circuit, the output voltage of the harmonic elimination circuit is pseudo-reset by the zero reset circuit, and is reliably reduced to a predetermined multiple of the averaging voltage of the averaging circuit. Therefore, the commutation command can be reliably reset for each commutation command even when the armature current is in a small no-load condition, so that multiple commutation commands are generated or abnormally long commutation is performed. The output of the command is prevented, and there is an effect that stable sensorless operation can always be realized.

[Brief description of the drawings]

FIG. 1A is a diagram showing a current waveform flowing in one phase of an armature winding of a brushless motor, and FIG.
FIG. 4 is an enlarged view of one block of the current waveform of FIG.

FIG. 2 is a circuit diagram of a brushless motor drive circuit according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between output voltage waveforms of each circuit during a steady operation of the brushless motor. (A)
It is a figure showing an output voltage waveform of a PWM chopper control circuit, (b) is a figure showing ON operation of a transistor of an inverter circuit, and (c) is a figure showing an output voltage waveform of a current detection circuit. (D) is a diagram showing an output voltage waveform of the harmonic elimination circuit, (e) is a diagram showing an output voltage waveform of the comparator of the commutation command circuit,
(F) is a diagram showing an output voltage waveform of the commutation command circuit.

FIG. 4 is a diagram showing a relationship between a voltage dividing ratio of a variable resistor of a PWM chopper control circuit and an output voltage waveform of each circuit when the brushless motor according to the first embodiment is started.
(A) is a figure which shows the mode of change of the voltage division ratio of the variable resistance of a PWM chopper control circuit, (b) is the figure which expanded and showed the output voltage waveform of the PWM chopper control circuit partially. (C) is a diagram showing a voltage waveform applied to the base terminal of the transistor of the starting compensation circuit;
(D) is a diagram showing a voltage waveform of the collector terminal of the transistor of the start compensation circuit, (e) is a diagram showing an output voltage waveform of the start compensation circuit, and (f) is a diagram of the current detection circuit. FIG. 4 is a diagram illustrating an output voltage waveform.

FIG. 5 is a diagram illustrating the PWM of the first embodiment when the brushless motor is driven and stopped, and when the brushless motor is stopped and started
FIG. 3 is a diagram illustrating a relationship between a voltage dividing ratio of a variable resistor of a chopper control circuit and an output voltage waveform of each circuit. (A) PWM
It is a figure which showed the mode of change of the voltage division ratio of the variable resistor of a chopper control circuit, (b) is a figure which expanded and showed the output voltage waveform of the PWM chopper control circuit partially, (c)
FIG. 3 is a diagram illustrating a voltage waveform applied to a base terminal of a transistor of a start compensation circuit, FIG. 4D is a diagram illustrating a voltage waveform of a collector terminal of a transistor of the start compensation circuit, and FIG. FIG. 3 is a diagram illustrating an output voltage waveform of a start compensation circuit, and FIG.

FIG. 6 shows the relationship between the output of the counting circuit and the output of the distribution circuit,
FIG. 3 is a diagram illustrating a relationship between directions of current flowing through an armature winding of the brushless motor at that time.

FIG. 7 is a circuit diagram of a brushless motor drive circuit according to a second embodiment.

FIG. 8 is a diagram illustrating a relationship between a voltage dividing ratio of a variable resistor of a PWM chopper control circuit and an output voltage waveform of each circuit when the brushless motor according to the second embodiment is started.
(A) is a figure which shows the mode of change of the voltage division ratio of the variable resistance of a PWM chopper control circuit, (b) is the figure which expanded and showed the output voltage waveform of the PWM chopper control circuit partially. (C) is a diagram illustrating a voltage waveform input to the operational amplifier of the start compensation circuit, (d) is a diagram illustrating an output voltage waveform of the operational amplifier of the start compensation circuit,
(E) is a diagram showing an output voltage waveform of the starting compensation circuit, and (f) is a diagram showing an output voltage waveform of the current detection circuit.

FIG. 9 is a PWM diagram of the brushless motor according to the second embodiment when the brushless motor is driven and stopped, and when the brushless motor is stopped and started.
FIG. 3 is a diagram illustrating a relationship between a voltage dividing ratio of a variable resistor of a chopper control circuit and an output voltage waveform of each circuit. (A) PWM
It is a figure which showed the mode of change of the voltage division ratio of the variable resistor of a chopper control circuit, (b) is a figure which expanded and showed the output voltage waveform of the PWM chopper control circuit partially, (c)
5A is a diagram illustrating a voltage waveform input to the operational amplifier of the start compensation circuit, FIG. 5D is a diagram illustrating an output voltage waveform of the operational amplifier of the start compensation circuit, and FIG. It is a figure showing an output voltage waveform, and (f) is a figure showing an output voltage waveform of a current detection circuit.

FIG. 10 is a circuit diagram of a brushless motor drive circuit according to a third embodiment.

FIG. 11 is a circuit diagram showing a modification of the chopper driver.

FIG. 12 is a circuit diagram of a distribution circuit that performs 180-degree energization and shows a modification of the distribution circuit.

FIG. 13 is a diagram illustrating a relationship between an output of a counting circuit and an output of a distribution circuit that performs 180-degree conduction, and a relationship of a current direction flowing through an armature winding of the brushless motor at that time.

[Explanation of symbols]

1,100,200 Brushless motor drive circuit 2 Auxiliary power supply circuit 3 Inverter circuit 4 Current detection circuit 5 First reduction circuit 6,101,111 Averaging circuit 7,103,113 Start compensation circuit 8,102 Second reduction circuit 9 Flow command circuit 10, 110 Zero reset circuit 11 Count circuit (part of conduction control circuit) 12, 30 Distribution circuit (part of conduction control circuit) 13 Harmonic removal circuit 14 PWM chopper control circuit (chopper control circuit) 41 First increase area of armature current 42 Second increase area of armature current 50 DC power supply 51 Brushless motor 56 Commutation command

Claims (4)

[Claims] An inverter circuit having a plurality of switching elements for sequentially supplying a DC voltage to a plurality of armature windings of a brushless motor, and commutation is performed by turning on and off the plurality of switching elements of the inverter circuit. An energization control circuit; and a chopper control circuit for turning on and off a switching element of the inverter circuit that is turned on by the energization control circuit by chopper control. The brushless motor is provided by changing an on / off duty ratio of the chopper control circuit. A brushless motor drive circuit capable of performing variable speed operation without a sensor, a current detection circuit that converts a current flowing through an armature winding of the brushless motor into a voltage and detects the voltage, and detects a detection voltage of the current detection circuit with the chopper control circuit. Switch of the inverter circuit A harmonic elimination circuit that stores in synchronization with the ON operation of the switching element, an averaging circuit that averages an output voltage of the harmonic elimination circuit, and an output voltage of the harmonic elimination circuit that averages the averaging circuit. A brushless motor drive circuit, comprising: a commutation command circuit that outputs a commutation command to the energization control circuit when the voltage becomes a predetermined multiple of the voltage. 2. Each time the on-duty ratio of the switching element of the inverter circuit by the chopper control circuit becomes less than a predetermined value and becomes more than a predetermined value, a time from a value sufficient for the brushless motor to generate a starting torque. 2. A brushless motor drive circuit according to claim 1, further comprising: a start compensation circuit for outputting a commutation target voltage gradually decreasing as time elapses to the commutation command circuit instead of the averaging voltage of the averaging circuit. . 3. The brushless motor driving circuit according to claim 2, wherein at least a part of said starting compensation circuit and said averaging circuit are integrally formed. 4. A system according to claim 1, further comprising a zero reset circuit for resetting the output voltage of said harmonic elimination circuit output to said commutation command circuit for each commutation command output from said commutation command circuit. The brushless motor drive circuit according to any one of claims 1 to 3, wherein: