JP3305640B2 - Brushless motor drive circuit - Google Patents

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 performing 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, it is forcedly commutated at a preset frequency and voltage as a synchronous motor or a stepping motor, and balances the load with the load up to a rotation range where sufficient speed electromotive force is generated for field position detection. 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 self-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 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. As a result, the commutation spike voltage due to the recirculation effect increases, causing a large error in the detectable speed electromotive force information. 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]

Accordingly, the present applicant has invented a sensorless drive circuit for a brushless motor described in Japanese Patent Application No. 7-207665. This 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.

[0005] The variable speed operation of the brushless motor is performed by PWM.
(Pulse width modulation) This can be performed by changing the on / off duty ratio of the inverter circuit by chopper control. A chopper-like voltage is applied to the brushless motor by the chopper control. The chopper-like voltage is integrated by the LR series impedance of the armature winding, so that the armature current flows almost continuously. However, since the removal is not performed until the carrier component is completely removed, the armature current has a current waveform including many harmonic components. Therefore, if the commutation timing is determined based on this current waveform, the commutation timing will be erroneous due to the influence of harmonic components.

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

[0007] However, in the above drive circuit, although the brushless motor can be operated at a variable speed by the PWM chopper control, there is a problem that when the load applied to the brushless motor fluctuates, the rotation speed changes. That is, when the load applied to the brushless motor increases, the rotation speed decreases, and conversely, when the load decreases, the rotation speed increases. For this reason, there has been a problem that the brushless motor cannot be rotated at a desired speed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a brushless motor drive circuit that can operate a brushless motor at a desired speed and at a variable speed without a sensor. .

[0009]

In order to achieve this object, a brushless motor drive 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 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 a voltage. Current detection circuit that converts Circuit detection voltage to the chopper control circuit.
Of the switching element of the inverter circuit by the path
A first sampling circuit for storing data in synchronization with the operation,
The instantaneous value of the output voltage of the sample circuit is set to one commutation operation.
The first increase region of the armature current after the second increase
A second sample circuit for storing before the area, and the first sample circuit;
The output voltage of the sampling circuit is equal to the storage voltage of the second sample circuit.
When the predetermined number of times has been reached, a commutation command is
Commutation command output to commutate the brushless motor
Path, a speed detection circuit for detecting the actual speed of the brushless motor based on a commutation command output from the commutation command circuit, a speed setting circuit for setting a target speed of the brushless motor, and the speed setting circuit The duty ratio of on / off by the chopper control circuit is changed based on the target speed set in (2) and the actual speed detected by the speed detection circuit, and the actual speed of the brushless motor is set in the speed setting circuit. A speed correction circuit for correcting the target speed.

When the brushless motor rotates, the positional relationship between the motor field and the energized armature winding changes. With this change, the value of the current flowing through the armature winding also changes. The brushless motor driving circuit according to the first aspect enables sensorless driving of the brushless motor by determining the commutation timing by paying attention to such a change in the armature current. Specifically, as shown in FIG. 1, when the armature winding is energized while the brushless motor is being driven, 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 (second current increase region).

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. An armature current flows through the armature winding of the brushless motor. This armature current is converted into a voltage by the current detection circuit and detected, and the first sample circuit detects
Switching element of inverter circuit by hopper control circuit
The output voltage of the current detection circuit is stored in synchronization with the ON operation of
And the storage voltage or a predetermined multiple of the storage voltage is
From the first sample circuit to the second sample circuit and the commutation command circuit
Output to the road. Instantaneous output voltage of the first sample circuit
The time value is the first increase of the armature current in one commutation operation.
In the second sample circuit after the region and before the second increase region
The stored voltage is output to the commutation command circuit.
In the commutation command circuit, the output voltage of the first sample circuit and the second
The stored voltage of the sample circuit is compared, and as a result of the comparison,
The output voltage of one sample circuit is equal to the storage voltage of the second sample circuit.
When the pressure becomes a predetermined multiple of the pressure, a second current increase of the armature current is performed.
The commutation control circuit from the commutation command circuit.
A commutation command is output to the road. Based on this commutation command,
The switching element of the inverter circuit is turned on or off by the conduction control circuit. As a result, commutation to the brushless motor is performed, and the brushless motor is driven without a sensor.

The actual speed of the brushless motor is detected by a speed detection circuit based on a commutation command output from the commutation command circuit. On the other hand, the target speed of the brushless motor is set in a speed setting circuit. The actual speed and the target speed are fed back (output) to the speed correction circuit, and the ON / OFF duty ratio of the chopper control circuit is changed based on the two speeds by the speed correction circuit, so that the actual speed of the brushless motor becomes the target speed. Will be corrected.

According to a second aspect of the present invention, in the brushless motor driving circuit according to the first aspect, the speed detection circuit includes a high-speed signal having a fixed time width for each commutation command output from the commutation command circuit. Or a pulse output circuit that outputs a low-level pulse, an averaging circuit that converts the output of the pulse output circuit into a voltage and averages the voltage, and a high-impedance buffer circuit connected to an output terminal of the averaging circuit. ing.

[0014]

[0015]

According to a third aspect of the present invention, in the brushless motor drive circuit according to the first or second aspect, the storing of the instantaneous value of the first sample circuit by the second sample circuit is performed by the commutation command. It is performed at the end of the pulse of the commutation command output from the circuit, the pulse width of the commutation command is shortened as the actual speed of the brushless motor detected by the speed detection circuit is increased, and conversely, A sample timing correction circuit is provided that is longer as the actual speed is lower.

When the rotation speed of the brushless motor increases, the arrival of the armature current in the second current increasing region 42 also increases. Therefore, it is necessary to increase the timing of storing the instantaneous value of the first sample circuit by the second sample circuit. is there. on the other hand,
When the rotation speed of the brushless motor decreases, the arrival of the armature current in the second current increasing region 42 also decreases.
It is necessary to delay the timing of storing the instantaneous value of the first sample circuit by the sample circuit. According to the brushless motor driving circuit of the third aspect, the operation is the same as that of the brushless motor driving circuit of the first or second aspect, and the pulse width of the commutation command is adjusted by the sampling time correction circuit. By
The higher the actual speed of the brushless motor is, the shorter it is.
The longer the actual speed is, the longer it is. Then, at the end of the pulse of the commutation command changed by the sample timing correction circuit, the instantaneous value of the first sample circuit is stored by the second sample circuit. Therefore, the storage timing of the instantaneous value of the first sample circuit by the second sample circuit is changed to an appropriate timing according to the change in the actual speed of the brushless motor. The brushless motor drive circuit according to claim 4 ,
4. The brushless motor drive circuit according to claim 1 , wherein the first sample circuit stores the detected voltage of the current detection circuit immediately before the chopper control circuit turns off a switching element of the inverter circuit. 5. Is performed at the timing shown in FIG. The brushless motor drive circuit according to claim 5 , wherein the brushless motor drive circuit according to any one of claims 1 to 4 , wherein the second sample circuit stores an instantaneous value of the first sample circuit by the energization control circuit. This is performed for each commutation operation. A brushless motor drive circuit according to claim 6 is the brushless motor drive circuit according to any one of claims 1 to 5 , wherein, when the brushless motor is started, a value sufficient to generate a starting torque of the brushless motor is provided. A start compensation circuit for outputting a voltage gradually decreasing with time to the commutation command circuit, wherein the commutation command circuit has an output voltage of the first sample circuit that is a predetermined multiple of an output voltage of the start compensation circuit. In this case, a commutation command is output to the energization control circuit. According to a seventh aspect of the present invention, in the brushless motor driving circuit according to the sixth aspect , the starting compensation circuit is configured such that an ON duty ratio of a switching element of the inverter circuit by the chopper control circuit is less than a predetermined value. Every time the value becomes equal to or more than the value, a voltage sufficient to generate a starting torque to the commutation command circuit is output. The brushless motor drive circuit according to claim 8 is the brushless motor drive circuit according to claim 6 or 7 , wherein the output voltage output from the second sample circuit to the commutation command circuit and the output voltage from the start compensation circuit. A priority circuit is provided which outputs the larger of the output voltage to the commutation command circuit to the commutation command circuit. The brushless motor drive circuit according to claim 9 is the brushless motor drive circuit according to any one of claims 1 to 8 , wherein each time a commutation command is issued by the commutation command circuit, the commutation command is output to the commutation command circuit. A zero reset circuit is provided for resetting the output voltage of the first sample circuit to zero volts.

[0018]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The principle of operation of the brushless motor drive circuit in this 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 drive circuit 1 of the present embodiment. This motor drive circuit 1 is a sensorless drive capable of variable speed operation of a brushless motor such as a small PM brushless motor for an indoor fan, a transport device capable of suddenly changing load torque, and an outdoor fan of an air conditioner subjected to disturbance due to a gust or the like. Used as a circuit. The brushless motor 51 to be driven is a surface magnet type brushless motor using a permanent magnet field as a rotor and a three-phase armature winding 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. Also,
This motor drive circuit 1 can also be used for an outer rotor motor in which a stator is provided inside and a rotor is provided outside.

The auxiliary power supply circuit 2 of the motor drive circuit 1
This is a circuit that 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 and the commutation instruction circuit 9.

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, and the ground-side input terminal N of the DC power supply 50 is connected. 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 connected to the lower arm transistors Qx to Qz to prevent them from turning on at the same time.
0pF) Cu to Cw are respectively connected.

On the other hand, the gate terminals of the lower arm transistors Qx to Qz are connected to the respective outputs x to z of the distribution circuit 12 via the 1 kΩ resistors Rx1 to Rz1, and connect the inverters Ix to Iz as chopper drivers. It is connected to the output terminal of the chopper control circuit 18 via the terminal. Each of the inverters Ix to Iz is constituted by 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, the lower arm transistors Qx to Qz are turned on and off according to the outputs x to z of the distribution circuit 12 and the output of the chopper control circuit 18. Specifically, when a low signal is output from the chopper control circuit 18 to turn off the collector and the emitter of the inverters Ix to Iz, and a high signal is output from the outputs x to z of the distribution circuit 12, The arm transistors Qx to Qz are turned on. That is, as shown in FIGS. 3A and 3B,
The lower arm transistors Qx to Qz are chopper-controlled according to the output of the chopper control circuit 18.

Incidentally, 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 current to u to Dz, all the voltages are converted by the shunt resistor Rs. FIG. 3C shows the output voltage waveform of the current detection circuit 4 during the normal operation of the brushless motor 51.

The harmonic elimination circuit 13 synchronizes with the chopper control by the chopper control circuit 18 to
Is a circuit for storing the output voltage of the current detection circuit 4 while the lower arm transistors Qx to Qz are on, and outputting the output voltage to the sampling circuit 5 and the commutation command circuit 9. In other words, harmonic components are removed by chopper control,
The output voltage of the current detection circuit 4 is output to the sampling circuit 5 and the commutation command circuit 9. Harmonic removal circuit 13
Represents an analog switch AS1, a capacitor C1, a resistor R3 that functions as an RC low-pass filter together with the capacitor C1, resistors R4, R5, and an operational amplifier OP.
1 and a non-inverting amplifier configured as described above.

One channel terminal of the analog switch AS1 is connected to the output terminal of the current detection circuit 4 via a 550Ω resistor R3, and the other channel terminal is connected to a 0.1 μF capacitor C1 having one end grounded. It is connected. The gate of the analog switch AS1 is connected to the output terminal of the chopper control circuit 18 via the inverter Ia, and while the row signal is output from the chopper control circuit 18 (the lower arm of the inverter circuit 3 is controlled by the chopper control). The analog switch AS1 is turned on while the transistors Qx to Qz are turned on. Therefore, the output voltage of the current detection circuit 4 is controlled by the lower arm transistors Qx to Qx by the chopper control circuit 18.
The data is stored in the capacitor C1 in synchronization with the ON operation of Qz. Therefore, in combination with the RC low-pass filter constituted by the resistor R3 and the capacitor C1, the output voltage of the current detection circuit 4 from which higher harmonic components have been removed by the chopper control can be stored in 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. This operational amplifier OP1 forms a non-inverting amplifier together with the resistors R4 and R5. Since the resistance value of the resistor R4 is 47 kΩ and the resistance value of the resistor R5 is 10 kΩ, the output of the capacitor C1 is amplified by about 5.7 times by the non-inverting amplifiers OP1, R4 and R5, and its output terminal Is output to the sampling circuit 5 and the commutation command circuit 9 connected to 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 sampling circuit 5 and the commutation command circuit 9. FIG. 3D illustrates 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, the resistance value of the shunt resistor Rs is increased
When the resistance is doubled to 1Ω, the output voltage of the current detection circuit 4 is also increased by a factor of ten. Therefore, in such a case, the non-inverting amplifier OP
The output of the capacitor C1 may be output to the sampling circuit 5 and the commutation command circuit 9 without passing through R1, R4, and R5. In this embodiment, a resistor Rs having a small resistance value is used to suppress a temperature rise of the shunt resistor Rs.

The sampling circuit 5 includes the harmonic elimination circuit 1
3 is a circuit for storing the instantaneous value of the output voltage and outputting the instantaneous value to the amplifier circuit 6. Sampling circuit 5
Has an analog switch AS2, a capacitor C2, and resistors R7 and R8. Analog switch AS2
Is connected to the output terminal of the harmonic elimination circuit 13, and the other channel terminal is connected to a 1 kΩ resistor R7.
Are connected to a 0.1 μF capacitor C2 and a 1MΩ resistor R8, both ends of which are both circuit grounded. The gate of the analog switch AS2 is connected to the output terminal of the commutation command circuit 9, and while the high commutation command 56 is being output from the commutation command circuit 9 (see FIG. 3 (g)). AS2 is turned on.

The capacitor C2 is connected to the analog switch AS
2 is connected to the output terminal of the harmonic elimination circuit 13 via the resistor R7 while the switch 2 is on. This capacitor C2 is connected to a resistor R7
Together with an RC low-pass filter to remove harmonic components that cannot be completely removed by the harmonic removal circuit 13,
The output voltage of the harmonic elimination circuit 13 is stored. The non-ground terminal of the capacitor C2 is connected only to the analog switch AS2 via the resistor R7, the resistor R8, and the non-inverting input terminal of the operational amplifier OP2 of the amplifier circuit 6, and the resistance value of the resistor R8. Is very large at 1MΩ,
The voltage value of the capacitor C2 is held for a predetermined time even after the analog switch AS2 is turned off. Therefore, the voltage value (instantaneous output) of the harmonic elimination circuit 13 immediately before the analog switch AS2 is turned off is stored in the capacitor C2.

The commutation command 56 is, as described later,
When the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the sampling circuit 5 amplified by the amplification circuit 6, the output is output from the commutation command circuit 9. Therefore, if for some reason a large voltage value is held in the capacitor C2 of the sampling circuit 5, the output voltage of the harmonic elimination circuit 13 cannot be higher than the amplified output voltage of the sampling circuit 5, and the commutation command 56 cannot be generated, and the brushless motor 51 stops.

However, since the resistor R8 is connected in parallel to the capacitor C2 of the sampling circuit 5, the electric charge accumulated in the capacitor C2 is gradually but slightly discharged by the resistor R8. The voltage value of C2 also gradually decreases. Therefore, the resistance R8
Is connected in parallel to the capacitor C2, even if a large voltage value is held in the capacitor C2,
The commutation command 56 can always be regenerated, and the brushless motor 51 does not stop.

The resistance value of the resistor R8 is determined by the value of the capacitor C2.
And the lower limit of the commutation frequency of the inverter circuit 3 at the time of startup. That is, when the lower limit value of the commutation frequency at the time of starting is about 2 Hz, a time constant slightly larger than the cycle of 12 Hz, which is six times that of the commutation frequency, is set. The resistance value of R8 and the capacitance of capacitor C2 are determined. In this embodiment, since the capacitance of the capacitor C2 is 0.1 μF,
The resistance value of the resistor R8 is 1 MΩ.

Note that, depending on the type of the operational amplifier OP2 of the amplifier circuit 6, a leakage current (input bias current) may flow from the non-inverting input terminal to the ground. In such a case, the voltage value of the capacitor C2 rises due to the leakage current, that is, the stored commutation target voltage which is the voltage value of the harmonic elimination circuit 13 changes in the rising direction. This makes it impossible to perform a normal commutation operation. However, by connecting the resistor R8 in parallel with the capacitor C2, such a leakage current can flow through the resistor R8, so that the voltage value of the capacitor C2 can be prevented from increasing, and the voltage value of the capacitor C2 always decreases. Therefore, the output voltage of the harmonic elimination circuit 13 can be maintained in the capacitor C2.

The amplification circuit 6 amplifies the voltage value stored by the sampling circuit 5 and outputs the amplified voltage value to the priority circuit 8. The amplifier circuit 6 includes the operational amplifier OP2 and 10k
A non-inverting amplifier constituted by two resistors R9 and R10 of Ω, and a variable resistor VR1 of 100 kΩ for reducing the output of the non-inverting amplifier to 1 or less, and a slider of the variable resistor VR1 From the end, the commutation target voltage at the time of steady operation is output.

The operational amplifier OP2 of the non-inverting amplifier has a non-inverting input terminal connected to a capacitor C2 which is an output terminal of the sampling circuit 5, and an output terminal of the operational amplifier OP2 having a resistor R9 and a variable resistor having one end grounded. VR1
Is connected. The other end of the resistor R9 is connected to an operational amplifier OP
2 and one end of a resistor R10, and the other end of the resistor R10 is grounded.

The resistance values of the two resistors R9 and R10 of the non-inverting amplifier are both the same 10 kΩ. Therefore, the output of the sampling circuit 5 is supplied to the non-inverting amplifiers OP2 and OP2.
It is amplified approximately twice by R9 and R10. The output of the sampling circuit 5 that has been amplified by a factor of two is output to the variable resistor VR1, and is reduced to one or less by the variable resistor VR1.
Output to the priority circuit 8. In this embodiment, the output of the sampling circuit 5 that has been amplified twice by the non-inverting amplifiers OP2, R9, and R10 is reduced to 0.7 times by the variable resistor VR1. Therefore, the output of the sampling circuit 5 as a whole is amplified by a factor of 1.4.
FIG. 3E shows an output voltage waveform of the amplifier circuit 6.

It should be noted that the variable resistor VR1
By adjusting the position of the slider, the amplification factor of the entire amplification circuit 6 can be changed, so that the amplification factor can be changed in accordance with the use situation. That is, tuning can be performed so that the motor efficiency is most improved in the normal operation region of the brushless motor 51.

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 in place of the amplified output of the sampling circuit 5 so that the brushless motor 51 can generate a sufficient starting torque at the time of starting. . This starting compensation circuit 7
Operates in conjunction with the output of the chopper control circuit 18.
That is, when the duty ratio of the chopper control output from the chopper control circuit 18 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 3.8. %, The starting compensation circuit 7 outputs the commutation target voltage at the time of starting to the commutation command circuit 9 via the priority circuit 8. The above-mentioned duty ratio of about 3.8% is determined by the voltage division ratio of the resistors R32 (390Ω) and R33 (10 kΩ).

The starting compensation circuit 7 includes a chopper control circuit 18
Is provided with a 100-kΩ resistor R31, and the other end of the resistor R31 is connected to one end of a 0.1 μF capacitor C11 and an inverting input terminal of an operational amplifier OP11. The other end of the capacitor C11 is connected to the 10 volt output of the auxiliary power supply circuit 2. Operational amplifier OP
The non-inverting input terminal 11 is connected to a 390Ω resistor R32 having one end connected to the 10 volt output of the auxiliary power supply circuit 2 and a 10kΩ resistor R33 having one end grounded. The output terminal of the operational amplifier OP11 is connected to the anode of the diode D11 and the 10 μF electrolytic capacitor C12.
Connected to the positive terminal of The cathode of diode D11 is connected to the 10 volt output of auxiliary power supply circuit 2, while the negative terminal of electrolytic capacitor C12 is
100 kΩ resistor R34 grounded to the circuit, cathode of diode D12 grounded to the anode, and 500 kΩ
It is connected to one end of a variable resistor VR2 of Ω. The other end of the variable resistor VR2 is connected to one end of a 100 kΩ resistor R35, and the other end of the resistor R35 is connected to the anode of a diode D3 which is the input terminal of the priority circuit 8 as the output terminal of the starting compensation circuit 7. I have.

The operation of the starting compensation circuit 7 will now be described with reference to FIGS. The voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is set low (FIG. 4A)
A), when the duty ratio of the row output of the chopper control circuit 18 is less than about 3.8% (FIG. 4B)
A), since the chopper pulse output from the chopper control circuit 18 is absorbed (suppressed) by the capacitor C11 constituting the low-pass filter of the starting compensation circuit 7, the input voltage to the inverting input terminal of the operational amplifier OP11 is equal to the resistance R3.
2 and about 9.6 input to the non-inverting input terminal by R33
It is 2 volts or more (FIG. 4 (c) A). In such a case, the output voltage of the operational amplifier OP11 is 0 volt (FIG. 4D). Therefore, when the duty ratio of the row output of the chopper control circuit 18 is less than about 3.8%,
The output voltage from the starting compensation circuit 7 is 0 volt (FIG. 4 (e) A). In this state, the brushless motor 5
1 is in a stopped state.

In this state, the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is increased (FIG. 4A), and the duty ratio of the row output of the chopper control circuit 18 is set to about 3.8.
% (B in FIG. 4B), the discharge of the capacitor C11 of the starting compensation circuit 7 cannot follow the charge, and the input voltage to the inverting input terminal of the operational amplifier OP11 becomes about 9.6.
The voltage drops to 2 volts or less (FIG. 4C). 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 operational amplifier OP1
1 rises from 0 volts to about 8.5 volts (FIG. 4 (d) B). Here, about 8.5 volts is a limit value of the output voltage determined by the characteristics of the operational amplifier (it can output only up to 1.5 volts or less of the power supply voltage due to the characteristics of the operational amplifier, and in this embodiment, the power supply voltage of the operational amplifier OP11). Is 10 volts, so 10 volts−1.5 volts =
It is 8.5 volts. The value of 1.5 volts naturally depends on the type of the operational amplifier.)

The output voltage of the operational amplifier OP11 is about 8.5
When the voltage reaches volts, a voltage of about 8.5 volts is applied to a differentiating circuit composed of the capacitor C12 and the resistor R34. For this reason, a differential pulse-like voltage wave that gradually decreases as time elapses from a voltage value of slightly less than 8.5 volts by subtracting the voltage drop from the starting compensation circuit 7 through the variable resistor VR2 and the resistor R35. It is output to the priority circuit 8 (FIG. 4 (e) B). Since the capacitance of the capacitor C12 is 10 μF and the resistance of the resistor R34 is 100 kΩ, this voltage wave is generated after one second (10 μF × 100 kΩ = 1).
In s), it is reduced to about 37% of its peak value.

The output voltage of starting compensation circuit 7 output to priority circuit 8 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 the brushless motor 51
When the motor is started, an armature current sufficient to generate a starting torque is passed (FIG. 4 (f) B), and the brushless motor 5
1 is started properly.

On the other hand, if the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is reduced during the rotation of the brushless motor 51 (FIG. 5A), the brushless brushless motor is driven as the duty ratio of the row output of the chopper control circuit 18 decreases. The effective value of the voltage applied to the motor 51 also decreases, and the brushless motor 51 is decelerated. And the chopper control circuit 1
When the duty ratio of the row output of No. 8 falls below about 3.8% (FIG. 5B), the charging of the capacitor C3 of the starting compensation circuit 7 cannot follow the discharging, and the operational amplifier OP11
The input voltage to the inverting input terminal of FIG. 1 rises to 9.62 volts or more, which is the input voltage to the non-inverting input terminal (FIG. 5C), and the output voltage of the operational amplifier OP11 changes from approximately 8.5 volts to 0 volts. It descends (FIG. 5D). When the output voltage of the operational amplifier OP11 becomes 0 volt, the electric charge stored in the capacitor C12 is changed to the diode D12 and the operational amplifier O11.
It is rapidly discharged through P11 and returns to the initial state.

From this state, the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is increased again (FIG. 5A), and the duty ratio of the row output of the chopper control circuit 18 is about 3.
When it exceeds 8% (FIG. 5B), the operational amplifier OP11
, The input voltage to the inverting input terminal drops to 9.62 volts or less (FIG. 5C), and the output voltage of the operational amplifier OP11 rises to about 8.5 volts (FIG. 5D). As a result, until the discharged capacitor C12 is recharged, a voltage pulse in the form of a differential pulse is output again from the starting compensation circuit 7 (FIG. 5 (e)).

When the DC power supply 50 is turned off during the operation of the brushless motor 51, the electric charge stored in the capacitor C12 is rapidly discharged through the diodes D11 and D12, and returns to the initial state. Therefore, even when the DC power supply 50 is turned on immediately after the power is turned off, the start-up compensation circuit 7 is normally operated, and the brushless motor 5 is operated.
1 can be started smoothly.

As described above, in the start compensation circuit 7 of this embodiment, even if the voltage ratio of the variable resistor VR4 of the speed setting circuit 16 is reduced and the brushless motor 51 being driven is stopped or rotated at a low speed, By increasing the voltage dividing ratio of the variable resistor VR4, the commutation target voltage sufficient for starting the brushless motor 51 from the start compensation circuit 7 can be output. Therefore, even in such a case, the brushless motor 51 can be started accurately. As described above, the start compensation circuit 7 includes the variable resistor V of the speed setting circuit 16.
It is configured to operate in conjunction with the speed setting by R4.

The priority circuit 8 outputs the output of the sampling circuit 5 amplified by the amplifier circuit 6, that is, the commutation target voltage at the time of steady operation, and the output of the starting compensation circuit 7, that is, the commutation target voltage at the time of starting. Is a circuit for outputting the larger output voltage to the commutation command circuit 9, and is constituted by a diode D3. This diode D3
Has its anode connected to the output terminal of the starting compensation circuit 7, its cathode connected to the output terminal of the amplifier circuit 6, and the inverting input terminal of the comparator CP 1 which is one input terminal of the commutation command circuit 9. . Therefore, the higher output voltage of the amplifier circuit 6 and the starting compensation circuit 7 is output to the commutation command circuit 9 as the commutation target voltage by the priority circuit 8.

The commutation command circuit 9 includes a brushless motor 51
Of the commutation command 56 of the counting circuit 11, the sampling circuit 5,
And a circuit for outputting to the zero reset circuit 10. The circuit mainly includes a comparator CP1 and a monostable multivibrator MM1. Comparator CP
1 is connected to the output terminal of the priority circuit 8, while the non-inverting input terminal is connected to the output terminal of the harmonic elimination circuit 13 via the resistor R16. Further, the comparator C
The output terminal of P1 is connected to the input terminal A of the monostable multivibrator MM1.
K, the sampling circuit 5 and the zero reset circuit 10 are connected to the gates of both analog switches AS2 and AS3.

The commutation command circuit 9 has a diode D4, the anode of which is connected to the output terminal of the sample timing correction circuit 19, and the cathode of which is connected to one end of a 100 kΩ variable resistor VR3. I have.
The other end of the variable resistor VR3 is connected to one end of a 10 kΩ resistor R15, and the other end of the resistor R15 is connected to one end of a 0.1 μF capacitor C5 and the monostable multivibrator MM1. The other end of the capacitor C5 is also connected to the monostable multivibrator MM1.

In the commutation command circuit 9, the comparator CP1
The output voltage of the harmonic elimination circuit 13 and the priority circuit 8
The magnitude of the output voltage is compared with the magnitude of the output voltage. As a result of the comparison, when the output voltage of the harmonic elimination circuit 13 becomes larger than the output voltage of the priority circuit 8, as shown in FIG. 3F, the high signal 55 is output from the output terminal of the comparator CP1 to the monostable multivibrator MM1. Output to input terminal A. As a result, a one-shot high signal (commutation command 56) is output from the output terminal Q of the monostable multivibrator MM1 to the counting circuit 11, as shown in FIG. The commutation command 56 is also output to the gates of the analog switches AS2 and AS3 of the sampling circuit 5 and the zero reset circuit 10 at the same time.
Is turned on.

The sampling circuit 5 holds the instantaneous output of the harmonic elimination circuit 13 immediately before the analog switch AS2 is turned off. Since the analog switch AS2 is turned on while the high commutation command 56 is output,
The sampling circuit 5 holds the instantaneous output of the harmonic removal circuit 13 at the timing when the commutation command 56 falls. Therefore, the timing of extracting the instantaneous output by the sampling circuit 5 is determined by the pulse width of the commutation command 56.

For this reason, the pulse width of the commutation command 56 is such that the end position of the pulse is located between the first current increasing region 41 and the second current increasing region 42 shown in FIG. Is set to That is, the pulse width of the commutation command 56 is set so that sampling by the sampling circuit 5 is performed in regions other than the first and second current increasing regions 41 and 42.

The reason for this is that the current value in the first current increasing region 41 is determined by the difference between the voltage applied to the armature winding of the brushless motor 51 and the speed electromotive force due to the rotation of the motor, and the armature impedance. This is because, in particular, the current increase rate is uniquely determined by the time constant of the armature impedance, and is not the current value and the increase rate determined by the generated torque of the motor. Further, the current value of the second current increasing region 42 is a difference between the voltage applied to the armature winding of the brushless motor 51 and the speed electromotive force due to the rotation of the motor,
This is because the current value is substantially determined by the resistance component in the armature impedance and hardly contributes to the generated torque of the motor.

Therefore, the first and second current increasing regions 4
It is not possible to determine an appropriate commutation timing for maintaining the generated torque according to the load based on the current values of 1, 42. In other words, an appropriate commutation timing can be determined based on current values in regions other than the first and second current increasing regions 41 and 42. Therefore, the first and second current increasing regions 4
The pulse width of the commutation command 56 is set so that the sampling circuit 5 performs extraction in an area other than the areas 1 and 42.

Specifically, the pulse of the commutation command 56 is the first
And the shortest pulse width of the commutation command 56 is 3 to 10 times or more the LR time constant (τ) determined by the armature impedance of the brushless motor 51 so as to end in an area other than the second current increasing areas 41 and 42. Time (3τ to 10τ)
Seconds). At the time of the sample holding operation of the sampling circuit 5, the instantaneous output of the harmonic elimination circuit 13 shows a tendency to be substantially saturated, and a time margin of 95% or more of the final value is considered. Further, the longest pulse width of the commutation command 56 is set to a time (２ / 3 × T seconds) which is ／ times the commutation period (T) when the brushless motor 51 rotates at the highest speed.
This is because the width of the second current increasing region 42 at the time of the highest rotation was set to 1/3 × T by an experiment ((1-1 / 3) × T = 2/3 × T).

Incidentally, as described above, the variable resistor VR
The output voltage of the sample timing correction circuit 19 is applied to the resistor 3 and the resistor R15 via the diode D4.

The sampling timing correction circuit 19 changes the pulse width of the commutation command 56 output from the commutation command circuit 9 in accordance with the rotation speed of the brushless motor 51, and changes the sampling timing (instantaneous output) of the sampling circuit 5. (Extraction time) is corrected to an appropriate timing.
The sample timing correction circuit 19 includes a comparator CP4,
It comprises a 1 kΩ pull-up resistor R43 connected to the output terminal of the comparator CP4. The non-inverting input terminal of the comparator CP4 is connected to the output terminal of the speed detection circuit 15, and the inverting input terminal is connected to the output terminal of the sawtooth wave generation circuit 14. The output terminal of the comparator CP4 is connected to the anode of the diode D4 of the commutation command circuit 9. Therefore, as shown in FIG. 6, the output voltage 6 of the speed detection circuit 15 is output from the sampling time correction circuit 19.
When 1 is higher than the output voltage 62 of the sawtooth wave generation circuit 14, a voltage of 10 volts is output. Conversely, when the output voltage 61 of the speed detection circuit 15 is lower than the output voltage 62 of the sawtooth wave generation circuit 14, 0 volt is output. Is output.

As will be described later, the speed detection circuit 15 outputs a voltage 61 corresponding to the rotation speed of the brushless motor 51.
That is, a high voltage is output when the brushless motor 51 is rotating at a high speed, and a low voltage is output when the brushless motor 51 is rotating at a low speed. On the other hand, the sawtooth wave generation circuit 14
A sawtooth voltage 62 that changes at a constant cycle of about 20 kHz is output. Therefore, the output voltage of the sample timing correction circuit 19 is a rectangular wave whose duty ratio changes according to the output voltage of the speed detection circuit 15. As shown in FIG. 6, the duty ratio of the rectangular wave increases as the rotation speed of the brushless motor 51 increases, and decreases as the rotation speed of the brushless motor 51 decreases. Therefore, the effective value of the voltage output from the sampling timing correction circuit 19 and applied to the variable resistor VR3 and the resistor R15 via the diode D4 changes according to the duty ratio of the rectangular wave.

The pulse width of the commutation command 56 output from the monostable multivibrator MM1 decreases as the voltage value applied to the variable resistors VR3 and R15 increases, and conversely, decreases as the applied voltage value decreases. become longer.
Therefore, when the rotation speed of the brushless motor 51 increases, the duty ratio of the rectangular wave output from the sampling timing correction circuit 19 increases, the effective value of the voltage applied to the variable resistor VR3 increases, and the commutation command The pulse width of 56 becomes shorter. Conversely, when the rotation speed of the brushless motor 51 decreases, the duty ratio of the rectangular wave output from the sampling timing correction circuit 19 decreases, and the variable resistance V
The effective value of the voltage applied to R3 decreases, and the pulse width of commutation command 56 also increases. In this way, the sampling timing correction circuit 19 follows the rotation speed of the brushless motor 51, the pulse width of the commutation command 56 is increased or decreased, and the instantaneous output extraction timing by the sampling circuit 5 is automatically corrected to an appropriate position. Because Therefore, commutation command 5
6, the degree of freedom of the setting range of the pulse width is increased, and the setting can be easily performed. It is most preferable that the pulse width of the commutation command 56 be set to be 倍 times (１ ／ T) of the commutation period (T) when the brushless motor 51 rotates at the highest speed.

The zero reset circuit 10 includes a commutation command circuit 9
For each commutation command 56 output from the
Is a circuit for artificially resetting the output voltage 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. With this RC low-pass filter, in addition to electrostatic transfer (induction) noise and electromagnetic noise generated by chopper control, harmonic components that cannot be completely removed by the harmonic removal circuit 13 are further removed.

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 input terminal of the commutation command circuit 9 which is a non-inverting input terminal of the comparator CP1. 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. For this reason, the high commutation command 56 from the commutation command circuit 9
Is output, the analog switch AS3 is turned on by the commutation command 56, the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 is grounded, and the voltage is reset to 0 volt.

The counting circuit 11 counts each time the commutation command 56 output from the commutation command circuit 9 rises.
It comprises a binary counter CT (TC4017 and clear circuit). The output terminal of the commutation command circuit 9 is connected to the input terminal CK of the counter CT, and the output terminals 0 to 5 of the counter CT are connected to the respective OR gates ORu to Ou of the distribution circuit 12.
The output terminals 6 to 9 of the counter CT are connected to a diode D
The terminals are connected to the clear terminal CLR through 5 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 to the circuit. When a rising signal is input from the commutation command circuit 9 to the input terminal CK of the counter CT, the output terminal 0, the output terminal 1,...
A high signal is output from the counter CT in the order of the output terminal 5 and the output terminal 0.

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 a 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 the source terminal is connected to a circuit grounded 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 ~
The output terminals of Iw and the OR gates ORx to ORz are connected to resistors R1u to R1z connected to the gate terminals of the field effect transistors Qu to Qz of the inverter circuit 3. FIG. 7 shows the relationship between the input and output of the distribution circuit 12, and
The three phases (U
(Phase, V-phase, Z-phase).

The speed detection circuit 15 outputs the brushless motor 5 based on the commutation command 56 output from the commutation command circuit 9.
1 is a circuit for detecting a commutation period of one and detecting the rotation speed of the brushless motor 51 from the commutation period. The detected speed is converted into a voltage value and output to the speed correction circuit 17 and the sample timing correction circuit 19. In addition, an inverted output (Q bar) of the commutation command 56 is input to the speed detection circuit 15 on the circuit. This takes into account the drive capability of the monostable multivibrator MM1 of the commutation command circuit 9.
Therefore, the output terminal Q of the monostable multivibrator MM <b> 1 may be input to the speed detection circuit 15 when there is no problem in the drive capability. That is, the monostable multivibrator MM2 described later may be configured to output a single pulse for each single pulse output operation of the monostable multivibrator MM1.

The speed detecting circuit 15 has a monostable multivibrator MM2. The input terminal A of the monostable multivibrator MM2 is connected to the output terminal Q of the monostable multivibrator MM1 of the commutation command circuit 9. ing. The monostable multivibrator MM2 has one end connected to a 10-volt output of the auxiliary power supply circuit 2 and a 50 k output terminal.
The resistor R36 of Ω, the other end of the resistor R36 and the 0.1 μF capacitor C13 connected to the monostable multivibrator MM2 are connected. Further, the output terminal Q of the monostable multivibrator MM2 has a resistance R of 100 kΩ.
The other end of the resistor R37 is connected to a plus terminal of a 10 μF electrolytic capacitor C14 whose minus terminal is grounded to the circuit and an input terminal of an operational amplifier OP12 forming a buffer. Operational amplifier OP
The output terminal 12 is connected to a speed correction circuit 17 and a sample timing correction circuit 19 as an output terminal of the speed detection circuit 15.

When a high pulse is output from the output terminal Q bar of the monostable multivibrator MM1 of the commutation command circuit 9 every time the commutation command 56 falls (FIG. 8 (b)), A one-shot high pulse 58 is output from the output terminal Q of the monostable multivibrator MM2 of the speed detection circuit 15 (FIG. 8C). The high pulse 58 is averaged by an RC averaging circuit including the resistor R37 and the capacitor C14, and the averaged voltage value appears at a connection end between the resistor R37 and the capacitor C14. By the way, the resistor R36 and the capacitor C13 connected to the monostable multivibrator MM2
Is fixed, the width of the high pulse 58 is constant. The high pulse 58 is output for each commutation command 56. Therefore, the shorter the period of generation of the commutation command 56, that is, the higher the rotation speed of the brushless motor 51, the higher the voltage between the terminals of the capacitor C14 (FIG. 8C).
B) Conversely, the longer the generation cycle of the commutation command 56, that is, the lower the rotation speed of the brushless motor 51, the lower the voltage between the terminals of the capacitor C14 (FIG. 8C).
A). Thus, the rotation speed of the brushless motor 51 is
This is detected as a voltage between terminals of the capacitor C14.

Since the output impedance (R37) of the RC averaging circuit is relatively large at 100 kΩ, the output impedance is reduced through the buffer constituted by the operational amplifier OP12 to the speed correction circuit 17 and the sample timing correction circuit 19. Output. Therefore, without causing an RC averaging calculation error in the speed detection circuit 15,
The averaging result can be transmitted to a plurality of circuits (speed correction circuit 17 and sample timing correction circuit 19).

The speed setting circuit 16 includes the brushless motor 5
1 is a circuit for starting and stopping, and for setting a rotation speed. The speed setting circuit 16 is connected to the auxiliary power supply circuit 2.
A 2.2 kΩ resistor R41 connected to the volt output, a 560Ω resistor R42 grounded to the circuit, and both resistors R41,
And a variable resistor VR4 of 5 kΩ connected between R42. A target voltage of the rotation speed is output from a slider end of the variable resistor VR4. That is, by changing the position of the slider of the variable resistor VR4, the brushless motor 51 can be started or stopped, and further its rotation speed can be changed.

The slider end of the variable resistor VR4 has a resistance of 10 kΩ.
A first-order delay circuit composed of a resistor R40 and a 10 μF electrolytic capacitor C16 is connected. The negative terminal of the capacitor C16 is grounded, and the positive terminal thereof is connected to the speed correction circuit 17 together with the resistor R40.

Variable resistance V for setting target voltage of rotation speed
If the slider position of R4 is suddenly changed by the user, the current flowing through the brushless motor 51 changes abruptly, so that the commutation timing becomes unstable or the brushless motor 51
In such a case, a problem such as an overcurrent may flow. However, in the speed setting circuit 16, the target voltage is output through the primary delay circuit including the resistor R40 and the capacitor C16. Therefore, even in such a case, the target voltage can be changed gently. The occurrence of points can be avoided. Therefore, even when the position of the slider of the variable resistor VR4 changes abruptly, the rotation speed of the brushless motor 51 can be gradually changed and the brushless motor 51 can be driven smoothly.

The speed correction circuit 17 compares the voltage value of the target speed set by the speed setting circuit 16 with the voltage value of the actual speed detected by the speed detection circuit 15, and determines the amount of operation to be corrected by the chopper. This is for outputting to the control circuit 18. The speed correction circuit 17 allows the speed setting circuit 16
The brushless motor 51 can be rotated at the target speed set in the above.

The speed correction circuit 17 has an operational amplifier OP13. The non-inverting input terminal of the operational amplifier OP13 is connected to the output terminal of the speed setting circuit 16, and the inverting input terminal is connected to the output of the speed detecting circuit 15 via a 5 kΩ resistor R38. Each end is connected. The inverting input terminal of the operational amplifier OP13 is connected to a resistor R39 of 50 kΩ and one end of an integrating capacitor C15 of 0.1 μF. The other ends of the resistor R39 and the capacitor C15 are connected to the output terminal of the operational amplifier OP13. Further, the output terminal of the operational amplifier OP13 is connected to the inverting input terminal of the comparator CP3 of the chopper control circuit 18 as the output terminal of the speed correction circuit 17.

The operational amplifier OP13 of the speed correction circuit 17
Constitutes a non-inverting amplifier for the output of the speed setting circuit 16 together with the resistors R38 and R39. Operational amplifier O
Input voltage to the noninverting input of P13, i.e., the output voltage of the speed setting circuit 16 and V _1, whereas, the operational amplifier OP1
3, the voltage at the other end of the resistor R38 connected to the inverting input terminal of
That is, assuming that the output voltage of the speed detection circuit 15 is V ₂ , 2
Since One of the resistors R38, the resistance value of R39 is respectively 5kΩ and 50kohm, the output voltage V _o of the operational amplifier OP13 _{is, V o = V 1 + 50} /5 × (V 1 -V 2) = V 1 +10
(V ₁ −V ₂ ).

The output voltage of the speed correction circuit 17 is output to the inverting input terminal of the comparator CP3 of the chopper control circuit 18. On the other hand, as described later, the comparator CP
The sawtooth wave generating circuit 14 outputs a sawtooth wave oscillating at a constant period to the non-inverting input terminal of No. Therefore, the target voltage V ₁ of the speed setting circuit 16 is higher than the speed detection circuit 15.
In the case of higher than the detection voltage V ₂ is chopper control circuit 1
The duty ratio of the row output of the rectangular wave output from 8 increases, the effective value of the voltage applied to the brushless motor 51 increases, and the rotational speed of the brushless motor 51 is corrected in the upward direction. Conversely, when the target voltage V ₁ of the speed setting circuit 16 is lower than the detection voltage V ₂ of the speed detection circuit 15, the duty ratio of the row output of the rectangular wave output from the chopper control circuit 18 decreases. Thus, the effective value of the voltage applied to the brushless motor 51 is reduced, and the rotation speed of the brushless motor 51 is corrected in the downward direction. Note that the stability of the control system is achieved by the integration capacitor C15.

The sawtooth wave generation circuit 14 is a circuit for generating a sawtooth wave 62 having a constant frequency (about 20 kHz in the present circuit) (see FIG. 6). The generated sawtooth wave is output to chopper control circuit 18 and sample timing correction circuit 19.

The sawtooth wave generating circuit 14 includes a comparator CP2, and a non-inverting input terminal of the comparator CP2 is connected to a resistor R19 of 100 kΩ, a resistor R20 of 220 kΩ, and an anode of a diode D9. . The other end of the resistor R20 is grounded, and the resistor R19
Is connected to the 10 volt output of the auxiliary power supply circuit 2. The cathode of the diode D9 is connected to a resistor R18 of 1 kΩ whose other end is connected to the 10-volt output of the auxiliary power supply circuit 2, an output terminal of the comparator CP2, and an output terminal of 82 kΩ.
And the cathode of the diode D10. The other end of the resistor R21 and the anode of the diode D10 are connected to a 180-pF capacitor C8, the other end of which is grounded, and the inverting input terminal of the comparator CP2. An inverting input terminal of the comparator CP2 is connected to a chopper control circuit 18 and a sample timing correction circuit 19 as an output terminal of the sawtooth wave generation circuit 14. That is, the sawtooth wave 62 of about 20 kHz applied to the inverting input terminal of the comparator CP2 is output to the chopper control circuit 18 and the sample timing correction circuit 19.

The chopper control circuit 18 converts the chopper-shaped rectangular wave into the lower arm transistors Qx to Qx of the inverter circuit 3.
This is a circuit for outputting to Qz to control the brushless motor 51 by chopper control. The brushless motor 5 is controlled by controlling the duty ratio of the rectangular wave output from the chopper control circuit 18, that is, by performing pulse width modulation.
1, the effective voltage applied to the brushless motor 51 is controlled, and the variable speed operation of the brushless motor 51 is performed.

The chopper control circuit 18 has a comparator CP3, the non-inverting input terminal of which is connected to the output terminal of the sawtooth wave generating circuit 14, and the inverting input terminal of which is connected to the output terminal of the speed correction circuit 17, respectively. ing. The output terminal of the comparator CP3 is a 1 kΩ pull-up resistor R25.
And the output terminals of the chopper control circuit 18 are connected to the input terminals of the inverters Ia, Ix to Iz and the input terminal of the starting compensation circuit 7. .

The chopper control circuit 18 outputs a rectangular wave of about 20 kHz, which is the same as the frequency of the sawtooth wave output from the sawtooth wave generation circuit 14. The duty ratio of this rectangular wave is determined by the position of the slider of the variable resistor VR4 of the speed setting circuit 16 and the rotation speed of the brushless motor 51 detected by the speed detection circuit 15. As the duty ratio of the rectangular wave row output increases, the brushless motor 51 rotates at a higher speed.

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 the DC power supply 50, the 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 the output of “uvwxyz” (FIG. 7).
reference). In the inverter circuit 3, the upper arm transistor Qu is turned on by such a signal, and the lower arm transistor Qy is turned on and off based on the chopper-shaped rectangular wave output from the chopper control circuit 18. As a result, an armature current flows from the U-phase to the V-phase of the armature winding of the brushless motor 51, and the driving of 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 stored in the capacitor C1 by the harmonic elimination circuit 13 in synchronization with the output of the chopper control circuit 18 while the lower arm transistor Qy of the inverter circuit 3 is on. By storing the output voltage of the current detection circuit 4 in synchronization with the chopper control in this way, 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 approximately 5.7 times, and
6 through the RC low-pass filter composed of the capacitor C6 and the capacitor C6.
Is output to the non-inverting input terminal.

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 chopper control circuit 18 reaches a predetermined value or more (for example, about 3.8% or more) (FIG. 4B). ), The output voltage of the operational amplifier OP11 is 0
It rises sharply from the bolt to about 8.5 volts (Fig. 4 (d)
B). Due to the increase of the output voltage of the operational amplifier OP11, a differentiating circuit constituted by the capacitor C12 and the resistor R34 operates, and a differential pulse-like voltage gradually falling from a voltage value of slightly less than 8.5 volts is output to the priority circuit 8. (FIG. 4 (e) B).

To the priority circuit 8, in addition to the output of the starting compensation circuit 7, the sampling circuit 5 amplified by the amplification circuit 6
Is also output. However, when the commutation command has not been issued yet, the sampling operation of the sampling circuit 5 is not performed, and the output voltage is 0 volt.
Therefore, the priority circuit 8 gives priority to the output of the starting compensation circuit 7 over the output of the sampling circuit 5 and the commutation command circuit 9
To the inverting input terminal of the comparator CP1.

In the commutation command circuit 9, the comparator CP1
Thus, the output voltage of the harmonic elimination circuit 13 and the priority circuit 8
Is compared with the output voltage of the starting compensation circuit 7 output through As a result of the comparison, the output of the commutation command 56 is on standby until the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the starting compensation circuit 7. While the output of the commutation command 56 is on standby, the same phase of the armature winding (for example, U-phase to V-phase)
Phase), the brushless motor 51
The armature current sufficient to generate a starting torque is supplied to the motor, and the field rotor of the brushless motor 51 gradually starts rotating.

As the field rotates, the value of the armature current of the brushless motor 51 changes. 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 chopper control circuit 18. Stored current detection circuit 4
Is amplified approximately 5.7 times in the harmonic elimination circuit 13 and output to the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 via the zero reset circuit 10.
As a result, when the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the start compensation circuit 7, the high signal 55 is output from the comparator CP1 of the commutation command circuit 9, and the one-shot multivibrator MM1 outputs the one-shot Flow command 5
6 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 is updated to “010000” by the commutation command 56 (see FIG. 7). As a result, each output of “uvwxyz” of the distribution circuit 12 becomes “0”.
11001 ", and the field effect transistors Qu and Qz are turned on in place 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 output not only to the counting circuit 11 but also to the sampling circuit 5 and the zero reset circuit 10, and the analog switches AS2 and Turn on AS3.

When the analog switch AS3 of the zero reset circuit 10 is turned on, the output voltage of the harmonic elimination circuit 13 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 is switched from high to low, A pulse 55 is generated (FIG. 3 (f)).
Therefore, the commutation command circuit 9 responding to the single pulse 55
The monostable multivibrator MM1 of the first embodiment has a high output duty ratio of the sample timing correction circuit 15 and a variable resistor VR.
3. When a predetermined time determined by the resistor R15 and the capacitor C5 elapses, the output is switched from high to low, and the state shifts to a state in which the next commutation command 56 is generated.

On the other hand, the sampling circuit 5 receives the commutation command 5
6, when the analog switch AS2 is turned on, the analog switch AS2 is connected to the output terminal of the harmonic elimination circuit 13, and the output voltage of the harmonic elimination circuit 13 is applied to the capacitor C2 of the RC low-pass filter including the resistor R7 and the capacitor C2. Is entered. When the commutation command 56 switches from high to low from this state, the analog switch AS2 is turned off.
The voltage value (instantaneous output) of the harmonic elimination circuit 13 immediately before turning off is stored in the capacitor C2. The stored voltage value (instantaneous output) is amplified by about 1.4 times by the amplifier circuit 6 and output to the priority circuit 8. Note that, as described above, the commutation command 56 is transmitted to the first and second current increasing regions 4.
Since it switches from high to low in the middle area of 1,42,
The instantaneous output of the current detection circuit 4 in the intermediate region is extracted by the sampling circuit 5 via the harmonic removal circuit 13.

As shown in FIG. 4 (e) B, the output voltage of the starting compensation circuit 7 gradually decreases with a lapse of time from a voltage value of slightly less than 8.5 volts with a negative gradient. . On the other hand, since the output voltage of the sampling circuit 5 is the instantaneous value of the armature current detected by the current detection circuit 4, the output voltage gradually (stepwise) increases after the start of the brushless motor 51. That is, the amplified output voltage of the sampling circuit 5 gradually increases discretely with the passage of time after the start of the passage of the armature current.

The priority circuit 8 outputs the larger one of the amplified output voltage of the sampling circuit 5 and the output voltage of the starting compensation circuit 7 to the commutation command circuit 9.
Therefore, the output of the priority circuit 8 switches from the output voltage of the starting compensation circuit 7 to the amplified output voltage of the sampling circuit 5 at a certain point in time. After this switching, the amplified output voltage of the sampling circuit 5 is continuously output to the commutation command circuit 9 as the output voltage of the priority circuit 8 (that is, the commutation target voltage).

The comparator CP1 of the commutation command circuit 9
When the output voltage of the harmonic elimination circuit 13 becomes 1.4 times or more the output voltage of the sampling circuit 5, a high signal 55 is output to the monostable multivibrator MM1 (FIG. 3).
(F)). As a result, a one-shot commutation command 56 is output from the commutation command circuit 9 to the counting circuit 11 (and the sampling circuit 5 and the zero reset circuit 10) (FIG. 3).
(G)) The commutation of the brushless motor 51 is performed by the counting circuit 11, the distribution circuit 12, and the inverter circuit 3. Then, by continuing this commutation, the brushless motor 51 is rotated.

The commutation command 56 is output from the commutation command circuit 9.
(Q bar output) is output to the speed detection circuit 15 (FIG. 8). In the speed detection circuit 15, a one-shot high pulse 58 having a fixed time width is output from the monostable multivibrator MM2 every time the inverted output rises.
The high pulse 58 is supplied to the resistor R37 and the capacitor C14.
(FIG. 8)
(C)). Since the high pulse 58 is output for each commutation command, the shorter the commutation cycle, that is, the brushless motor 51
The higher the rotation speed of is, the higher the averaged voltage value (the voltage value between the terminals of the capacitor C14). Therefore, the averaged voltage between the terminals of the capacitor C14 is used as the actual speed information of the brushless motor 51 via the buffer OP12 via the speed correction circuit 17 and the sample timing correction circuit 19.
Output to

The speed correction circuit 17 receives a voltage value as the actual speed information output from the speed detection circuit 15,
The voltage value as the target speed information set by the speed setting circuit 16 is output. The speed correction circuit 17 compares and amplifies the two voltage values, and outputs the amplified result to the chopper control circuit 18 as an operation amount. As described above, V ₁ the voltage value of the target speed, when the voltage value of the actual speed is V _2, from the speed correction circuit 17, V _o = V ₁ +10 voltage V _o of (V ₁ -V ₂₎
Is output to the inverting input terminal of the comparator CP3 of the chopper control circuit 18.

The comparator CP of the chopper control circuit 18
A sawtooth wave oscillating at a constant period is output from the sawtooth wave generating circuit 14 to the non-inverting input terminal 3. Therefore, the target voltage V ₁ is the speed detection circuit of the speed setting circuit 16 1
When 5 higher than the detection voltage V ₂ of (V _1> V _2), chopper control circuit 18 increases the duty ratio of the low output of the rectangular wave output from the effective voltage applied to the brushless motor 51 Is increased, and the rotation speed is corrected in the upward direction. Conversely, if the target voltage V ₁ of the speed setting circuit 16 is lower than the detection voltage V ₂ of the speed detection circuit 15 (V ₁ <V ₂ ), the duty of the rectangular wave row output output from the chopper control circuit 18 The ratio becomes smaller, the effective value of the voltage applied to the brushless motor 51 decreases,
The rotation speed is corrected in the downward direction. As described above, the actual rotation speed of the brushless motor 51 is fed back and corrected so as to match the target speed.

As described above, the brushless motor 5
When the armature current 1 becomes 1.4 times or more the instantaneous value held by the sampling circuit 5, a commutation command 56 is output. Since the extraction by the sampling circuit 5 is performed in the area between the first and second current increasing areas 41 and 42, the commutation command 56 is output in the second current increasing area 42, and the brushless motor 51 commutation is performed. Therefore, the brushless motor drive circuit 1 allows the brushless motor 51 to be used without using a rotor magnetic pole position sensor such as a Hall element or a shaft encoder.
Can be driven smoothly.

In particular, in the motor drive circuit 1 of the present embodiment,
The actual speed information of the brushless motor 51 is fed back, compared with the target speed set by the user, and the effective voltage applied to the brushless motor 51 is changed according to the difference. Therefore, the brushless motor 51
Can be rotated at a speed consistent with the target.

The effective voltage applied to the brushless motor 51 is changed by pulse width modulation (PWM) control, and chopper control is used to perform the pulse width modulation control. Harmonic components accompany the chopper control, but the harmonic components are not removed by averaging with a low-pass filter but are removed by operating the harmonic removing circuit 13 in synchronization with the chopper control. Therefore, even when the duty ratio of the chopper control is small, the detection can be performed while the armature current is kept at a correct value. be able to. Therefore, the brushless motor 51 can be operated at a variable speed in the entire range where the duty ratio is about 3.8% to 100%.

Further, the instantaneous output of the current detection circuit 4 is extracted by the sampling circuit 5 for each commutation operation, and the commutation operation is performed based on the instantaneous value. The commutation timing is quickly adjusted, and an appropriate commutation operation can be performed.

Next, a modification of the above-described embodiment will be described with reference to the drawings. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

First, referring to FIG.
A modified example of the chopper driver composed of Iz will be described. The chopper driver shown in FIG. 9 replaces three inverters Ix to Iz with one inverter (NPN type digital transistor) Ib and three diodes D1.
5, D16, and D17 to reduce the cost of the circuit. The output terminal of the inverter Ib is connected to the cathodes of the three diodes D15 to D17, and 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 chopper control circuit 18, when the chopper pulse is output from the chopper control circuit 18, the input terminal of the inverter Ib is turned on by the distribution circuit 12 in synchronization with the output. The arm transistors Qx to Qz are chopper-controlled.

FIGS. 10 and 11 show modified examples of the distribution circuit. As described in the section of the prior art, conventionally, the commutation timing of the motor is determined by focusing on the correlation between the speed electromotive force generated in the armature winding of the rotating motor and the position of the field. Brushless motor 51
The three-phase armature winding could not be energized by 180 degrees. However, the brushless motor drive circuit 1 of the present embodiment
Focuses on the change in the armature current, and
Since the sensor 1 is driven sensorlessly, it is possible to energize 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.

Therefore, FIG. 10 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 the 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. May be configured. Such a configuration can be realized very easily by a microcomputer.

The present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various 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, as long as the current detection circuit can detect the armature current, it may be provided at a position other than the ground line of the DC link. Further, three current detection circuits may be separately provided so that the three-phase armature currents can be individually detected.

The detection of the instantaneous output of the harmonic elimination circuit 13 by the sampling circuit 5 was performed for each commutation command in order to quickly respond to a sudden change in load torque. But,
The present invention is not limited to this, and the instantaneous output of the harmonic elimination circuit 13 may be detected once for each of a plurality of commutation commands. In the brushless motor 51 provided with the three-phase armature winding as in the present embodiment, such detection may be performed once every three or six commutation instructions.

Further, the output of the sampling circuit 5 is amplified by about 1.4 times by the amplifier circuit 6, but this amplification factor is naturally changed according to the sample position of the armature current. . Therefore, the amplification factor of the amplifier circuit 6 is not necessarily limited to 1.4 times, and may be 1 time or more or 1 time or less. Further, the output of the starting compensation circuit 7 is output from the priority circuit 8 to the commutation command circuit 9 without being amplified at all, and the output of the starting compensation circuit 7 is also at least one time (or at most one time). ) May be amplified (or reduced) and output to the commutation command circuit 9.

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, the upper arm transistors Qu to Q in which chopper control is not performed
Regarding w, since high-speed operation is not required, in order to reduce the cost of the circuit 1 and improve the availability of parts,
Instead of the field effect transistor, a junction type PNP transistor may be used. Also, instead of the lower arm transistors Qx to Qz, an upper arm transistor Qx
You may comprise so that chopper control may be carried out by u-Qw. Further, the chopper control may be performed by both the upper and lower arm transistors Qu to Qz.

The output voltage of the harmonic elimination circuit 13 is
It is stored in the sampling circuit 5 at the timing when the commutation command 56 falls, and the next commutation command 56 is issued based on the stored voltage of the sampling circuit 5. That is,
When the voltage value of the harmonic elimination circuit 13 becomes approximately 1.4 times the voltage value stored in the sampling circuit 5, the commutation command 56 is issued. However, instead of this method, when the output voltage of the harmonic elimination circuit 13 is averaged, and the averaged voltage value becomes a predetermined multiple of the voltage value (instantaneous value) of the harmonic elimination circuit 13, The commutation command 56 may be configured to be issued.

Further, the principle configuration similar to those described above is applied to A / D
It may be configured using a combination of a converter and a microcomputer or a digital signal processor, or using a microcomputer and software with a built-in A / D converter.

(Preliminary 1) The storage of the detection voltage of the current detection circuit by the first sample circuit is performed at a timing immediately before the switching element of the inverter circuit is turned off by the chopper control circuit. The brushless motor drive circuit according to claim 3.

(Preparation 2) The storage of the instantaneous value of the first sampling circuit by the second sampling circuit is performed every commutation operation by the current supply control circuit. The brushless motor drive circuit according to 1.

(Preliminary 3) The second sample circuit stores the instantaneous value of the first sample circuit after the first increase region of the armature current in one commutation operation and before the second increase region. The brushless motor driving circuit according to claim 3 or 4, or the preliminary (1) or (2).

(Preliminary 4) At the time of starting the brushless motor, a start compensation circuit is provided for outputting to the commutation command circuit a voltage gradually decreasing with time from a value sufficient to generate the starting torque of the brushless motor. Wherein the commutation command circuit outputs a commutation command to the energization control circuit when the output voltage of the first sample circuit becomes a predetermined multiple of the output voltage of the start compensation circuit. Item 4. The brushless motor drive circuit according to any one of Items 3 or 4, or Reserves 1 to 3.

(Preliminary 5) The starting compensation circuit supplies the starting torque to the commutation command circuit every time the ON duty ratio of the switching element of the inverter circuit by the chopper control circuit becomes less than a predetermined value or more than a predetermined value. A spare 4 characterized by outputting a voltage sufficient to generate
The brushless motor drive circuit according to the above.

(Preliminary 6) The larger of the output voltage output from the second sample circuit to the commutation command circuit and the output voltage output from the starting compensation circuit to the commutation command circuit A standby circuit for outputting a voltage to the commutation command circuit by priority;
Or the brushless motor drive circuit according to 5.

(Preliminary 7) Each time a commutation command is issued by the commutation command circuit, a zero reset circuit is provided which falsely resets the output voltage of the first sample circuit output to the commutation command circuit to zero volts. 7. The brushless motor drive circuit according to claim 3, wherein the brushless motor drive circuit comprises:

[0123]

According to the brushless motor drive circuit of the present invention , the armature current of the brushless motor is converted into a voltage and detected by the current detection circuit.
The arrival of the armature current in the second current increase region is detected based on the detected voltage. A commutation command is output at the timing when the second current increase region arrives, and commutation to the brushless motor is performed, so that the brushless motor can be rotated (driven) without a sensor. The application of the drive voltage to the brushless motor is performed by chopper control, and the effective voltage applied to the brushless motor can be changed by changing the duty ratio of the chopper control. Therefore, there is an effect that the brushless motor can be operated at a variable speed without a sensor.

Further, the actual speed of the brushless motor is detected by the speed detection circuit based on the commutation command, and is fed back to the speed correction circuit. The target speed of the brushless motor is set in the speed setting circuit, and this target speed is also output to the speed correction circuit. In the speed correction circuit,
Based on the two speeds, the duty ratio of the chopper control by the chopper control circuit is changed so that the actual speed of the brushless motor matches the target speed. Therefore, there is an effect that the brushless motor can be rotated (driven) at a desired speed (target speed).

The first sample 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 detected armature current can be accurately detected. Since the commutation command is output based on the detection voltage of the first sample circuit from which the harmonic component has been removed, the commutation operation can be performed at an appropriate timing without being affected by the chopper control. effective.

Further, the second sample circuit stores the instantaneous value of the output voltage of the first sample circuit, and the commutation command indicates that the output voltage of the first sample circuit is a predetermined multiple of the storage voltage of the second sample circuit. Is output if That is, the commutation command is
The output is based on the instantaneous value of the output voltage of the first sample circuit stored in the second sample circuit. Therefore, even when the load torque of the brushless motor suddenly changes, the sudden change is quickly stored by the second sample circuit, so that the generation timing of the commutation command is quickly adjusted. Therefore, even when the load torque changes suddenly, an appropriate commutation operation can be performed, and there is an effect that the brushless motor can be driven stably.

The instantaneous value of the first sample circuit is stored by the second sample circuit at the end of the commutation command pulse. The shorter the actual speed, the longer the speed. Therefore, the storage timing of the instantaneous value by the second sample circuit is changed to an appropriate timing according to the actual speed of the brushless motor. Accordingly, the instantaneous value of the armature current that directly contributes to the torque generated by the brushless motor can be stored by the second sample circuit. By generating a commutation command based on this instantaneous value, the appropriate timing can be obtained. There is an effect that a commutation operation can be performed and the brushless motor can be driven stably.

[Brief description of the drawings]

1A is a diagram showing a current waveform flowing in one phase of an armature winding of a brushless motor, and FIG.
FIG. 3 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 one 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 the figure which showed the output voltage waveform of the PWM chopper control circuit, (b) was the figure which showed the ON operation | movement of each transistor of the inverter circuit, (c) showed the output voltage waveform of the current detection circuit. It is a figure, (d) is a figure showing the output voltage waveform of the harmonic elimination circuit, (e) is a figure showing the output voltage waveform of the amplifier circuit, (f) is a commutation command FIG. 3 is a diagram showing an output voltage waveform of a comparator of the circuit;
(G) 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 speed setting circuit at the time of starting a brushless motor and an output voltage waveform of each circuit. (A) is a figure which shows the mode of change of the voltage division ratio of the variable resistor of a speed setting circuit, (b)
FIG. 3 is a partially enlarged view of an output voltage waveform of a PWM chopper control circuit, and FIG. 3C is a view illustrating a voltage waveform input to an operational amplifier of a start compensation circuit;
(D) is a diagram showing an output voltage waveform of the operational amplifier of the start compensation circuit, (e) is a diagram showing an output voltage waveform of the start compensation circuit, and (f) is an output of the current detection circuit. FIG. 3 is a diagram illustrating a voltage waveform.

FIG. 5 is a diagram illustrating a relationship between a voltage dividing ratio of a variable resistor of a speed setting circuit and an output voltage waveform of each circuit when the brushless motor is driven from a stop to a stop and from a stop to a start. (A) is a diagram showing a state of a change in a voltage dividing ratio of a variable resistor of a speed setting circuit, and (b) is a diagram showing a partially enlarged output voltage waveform of a PWM chopper control circuit. , (C) is a diagram showing a voltage waveform input to the operational amplifier of the starting compensation circuit, (d) is a diagram showing an output voltage waveform of the operational amplifier of the starting 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. 6 is a diagram showing a relationship between output voltage waveforms of a speed detection circuit, a sawtooth wave generation circuit, and a sample timing correction circuit.

FIG. 7 shows the relationship between the output of the counting circuit and the output of the distribution circuit,
FIG. 4 is a diagram illustrating a relationship between directions of current flowing through an armature winding of the brushless motor at that time.

8A is a diagram showing a voltage waveform of a Q output of a monostable multivibrator of a commutation command circuit, and FIG.
FIG. 3 is a diagram showing a voltage waveform of a Q bar output of a monostable multivibrator of a commutation command circuit, and FIG. FIG. 4 is a diagram illustrating a relationship with a voltage.

FIG. 9 is a circuit diagram showing a modification of the chopper driver.

FIG. 10 is a circuit diagram of a distribution circuit that performs 180-degree conduction, showing a modification of the distribution circuit.

FIG. 11 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 direction of a current flowing through an armature winding of the brushless motor at that time.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 brushless motor drive circuit 2 auxiliary power supply circuit 3 inverter circuit 4 current detection circuit 5 sampling circuit (second sample circuit) 6 amplifier circuit 7 start compensation circuit 8 priority circuit 9 commutation command circuit 10 zero reset circuit 11 counting circuit (power control) Part of circuit) 12 Distribution circuit (part of conduction control circuit) 13 Harmonic elimination circuit (first sample circuit) 14 Sawtooth wave generation circuit 15 Speed detection circuit 16 Speed setting circuit 17 Speed correction circuit 18 Chopper control circuit 19 Sample Timing correction circuit 41 First increasing area of armature current 42 Second increasing area of armature current 50 DC power supply 51 Brushless motor 56 Commutation command MM2 Monostable multivibrator (pulse output circuit) C14 Capacitor (of averaging circuit) R37 resistor (part of the averaging circuit) OP12 OP (Buffer circuit)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 6/06 H02P 6/18 H02P 6/20

Claims (9)

(57) [Claims] 1. A multi-phase armature winding of a brushless motor.
Multiple switching elements to sequentially apply DC voltage to
And an inverter circuit having
Energization that commutates by turning on and off a number of switching elements
Before being turned on by the control circuit and its energization control circuit
The switching element of the inverter circuit is used for chopper control
Therefore, a chopper control circuit for turning on and off is provided,
Change the on / off duty ratio by the chopper control circuit
By making the brushless motor sensorless
Brushless motor drive circuit capable of variable speed operation
Wherein the current flowing through the armature winding of the brushless motor is
A current detection circuit that converts and detectsThe detection voltage of the current detection circuit is applied to the chopper control circuit.
ON operation of the switching element of the inverter circuit
A first sample circuit that stores the data in synchronization with The instantaneous value of the output voltage of the first sample circuit is represented by 1 commutation
After the first increasing region of the armature current in operation and
A second sample circuit for storing before an increment of 2; The output voltage of the first sample circuit is changed to the second sample time.
When the storage voltage of the circuit becomes a predetermined multiple, the energization control circuit
Output a commutation command to the
Commutation command circuit  Based on the commutation command output from the commutation command circuit,
Speed detection circuit that detects the actual speed of the brushless motor
Speed setting times for setting a target speed of the brushless motor.
Road, target speed set in the speed setting circuit and the speed detection
Based on the actual speed detected by the circuit,
Change the on / off duty ratio by the
Set the actual speed of the brushless motor in the speed setting circuit
And a speed correction circuit for correcting to the set target speed.
A brushless motor drive circuit, characterized in that: 2. A pulse output circuit for outputting a high or low pulse having a predetermined time width for each commutation command output from the commutation command circuit, and a voltage output from the pulse output circuit. 2. An averaging circuit for converting and averaging, and a high impedance buffer circuit connected to an output terminal of the averaging circuit.
The brushless motor drive circuit according to the above. 3. The storage of the instantaneous value of the first sample circuit by the second sample circuit at the end of a pulse of a commutation command output from the commutation command circuit. the pulse width shortens the faster the actual speed of the brushless motor detected by the speed detection circuit, according to claim conversely, characterized in that the actual speed and a sample timing correction circuit for longer as slow 1 Or the brushless motor drive circuit described in 2. 4. A storage of the detection voltage of the current detection circuit according to the first sample circuit, claims, characterized in that the switching elements of the inverter circuit by the chopper control circuit is performed at the timing immediately before being turned off 1
4. The brushless motor drive circuit according to any one of claims 1 to 3 . 5. The storage of the instantaneous value of the first sample circuit according to the second sample circuit from claim 1, characterized in that it is performed for each commutation operation by the energization control circuit 4
The brushless motor drive circuit according to any one of the above. 6. A time of starting of the brushless motor, comprising a starting compensation circuit for outputting a voltage decreasing with the passage from the value sufficient time to generate a starting torque of the brushless motor to the commutation command circuit, said commutation command circuit, according to claim 1 in which the output voltage of the first sample circuit when a predetermined multiple of the output voltage of the starting compensation circuit, and outputs a commutation command to the energization control circuit Or
6. The brushless motor drive circuit according to any one of claims 5 to 5 . 7. The starting compensation circuit generates a starting torque to the commutation command circuit 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 or more than a predetermined value. 7. The brushless motor drive circuit according to claim 6 , wherein a sufficient voltage is output to drive the motor. 8. A output voltage output from the second sample circuit to the commutation command circuit, among from the starting compensation circuit between the output voltage to be output to the commutation command circuit, the output voltage of the larger The brushless motor drive circuit according to claim 6, further comprising a priority circuit that outputs the commutation command circuit by priority. 9. For each commutation command by said commutation command circuit,
Brushless motor driving circuit according to any one of claims 1 to 8, characterized in that it comprises a zero reset circuit for constructive reset to zero volts the output voltage of the first sample circuit output to its commutation command circuit .