KR100288282B1 - Method and apparatus for driving sensorless DC motor with bridge type inductance detection circuit - Google Patents

Abstract

Disclosed is a method and apparatus for driving a sensorless direct current motor having a breach type inductance detection circuit. A method of driving a sensorless DC motor comprising a rotor having Y-connected phase coils and a plurality of magnetic poles, the method comprising: applying an AC voltage signal to bridge circuits respectively coupled to the phase coils; And inputting each output voltage signal of the bridge circuits as an inductance detection signal of each phase, amplifying the input inductance detection signal of each phase coil, and comparing magnitudes of the inductance detection signals of each amplified phase coil. And determining the initial position of magnetizing the remaining two phase coils except the phase coil having the maximum value of the inductance detection signal in order to rotate the rotor. Therefore, in the present invention, since the initial position of the rotor can be accurately determined in the stationary state or the low speed mode, reliability in driving the motor is improved.

Description

Method and device for driving sensorless DC motor with bridge type inductance detection circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for driving a sensorless DC motor, and more particularly, to a sensorless DC motor having a bridge type inductance detection circuit for detecting an inductance according to a relative position of an upper coil and a magnetic rotor to determine the position of the rotor. It relates to a driving method and an apparatus.

The video cassette recorder (VCR) includes a capstan motor and a head drum motor. Conventionally, for driving these motors, the position of the rotor is determined using a sensor such as a hall sensor, an optical sensor, and the commutation of the phase current applied to the motor is controlled according to the determined position information. However, the sensor method is required to secure a space for installing the sensor, there is a problem that the cost of the product is increased by using expensive sensor parts.

Therefore, in recent years, the sensorless method which does not use a sensor is employ | adopted.

Conventional sensorless motors are widely used to determine the commutation of the rotor by detecting the Back ElectroMotive Force (BEMF) induced on the phase coil in order to determine the position of the magnetic rotor (see US Patent 5,235,264).

The magnitude of back EMF induced in the coil is proportional to the rotational speed of the rotor. Therefore, the counter electromotive force method has a problem in that it is difficult to detect the counter electromotive force since there is no or low counter electromotive force induced when the rotor is stopped or at a low speed. Therefore, in the counter electromotive force, the commutation control becomes unstable until the rotor is rotated at a predetermined speed or more at which the counter electromotive force can be sufficiently detected.

The present invention aims to solve this problem of the prior art, and therefore the object of the present invention is to stop by detecting the inductance of the phase coil according to the relative position of the phase coil and the magnetic rotor in order to solve this problem of the prior art. The present invention provides a method and apparatus for driving a sensorless DC motor capable of accurately detecting an initial position of a rotor in a state or a low speed mode.

1 is a driving circuit diagram of a sensorless DC motor having an Owen bridge circuit according to the present invention.

2 is a detailed circuit diagram of the Owen bridge circuit of FIG.

3 is a view showing the configuration of the upper coils and the magnetic rotor.

Fig. 4 is a waveform diagram of the output voltage of the bridge circuit when the inductance of the phase coil is 835 µH.

5 is a characteristic graph of the output voltage with respect to the inductance of the phase coil.

6 is a waveform diagram of the amplified inductance output voltage of each phase coil corresponding to the rotation angle of the magnet rotor.

7 is a driving circuit diagram of a sensorless DC motor having an inductance bridge circuit according to the present invention.

8 is a detailed circuit diagram of an inductance bridge circuit.

9 is a waveform diagram of the maximum voltage of each inductance bridge circuit corresponding to the rotation angle of the magnet rotor when a square wave is input.

Fig. 10 is a waveform diagram of a minimum voltage of each inductance bridge circuit corresponding to the rotation angle of the magnet rotor at the time of square wave input.

Fig. 11 is a waveform diagram of an inductance difference voltage between two phases during sine wave input.

12 is a graph showing inductances corresponding to rotor rotation angles of respective phase coils.

Fig. 13 is a graph showing the phase relationship between an input signal and a differential voltage signal under the condition of L1> L2.

14 is a graph showing a phase relationship between an input signal and a differential voltage signal under a condition of L2> L1.

15 shows an energizing sequence of phase coils.

<Explanation of symbols for main parts of drawing>

10: AC voltage power supply 12,14,16: bridge circuit

18,20,22: amplifier 24: commutation control

26: drive unit 28, 30, 32: upper coil

34: motor case

In order to achieve the above object, a first method of the present invention provides a method of driving a sensorless DC motor including a rotor having Y-connected phase coils and a plurality of magnetic poles, the bridge circuit being coupled to each of the phase coils. Applying an AC voltage signal to each field, inputting each output voltage signal of the bridge circuits as an inductance detection signal of each phase, amplifying the inductance detection signals of each phase coil, and amplifying each phase Comparing the magnitudes of the inductance detection signals of the coils, and determining an initial position of magnetizing the other two phase coils except the phase coil having the maximum magnitude of the inductance detection signal to rotate the rotor. It is characterized by.

A first device of the present invention is a drive device for a sensorless DC motor including a rotor having Y-connected phase coils and a plurality of magnetic poles, the AC voltage source for providing an AC voltage signal and the AC voltage signal. Bridge circuits coupled to the respective phase coils and an amplifier for amplifying each inductance detection signal of the bridge circuits in order to input and output a difference voltage signal between the reference voltage signal and the terminal voltage signal of the phase coil as an inductance detection signal. And the magnitudes of the inductance detection signals of each of the amplified phases, and determine an initial position of magnetizing the remaining two phases except the phase having the maximum value of the inductance detection signal, and for each predetermined rotation angle of the rotor. A commutation control unit for comparing the magnitude and determining the commutation; and responding to the control of the commutation control unit It characterized in that it comprises a driving section for providing a driving current to a coil of more than a couple.

The bridge circuit includes a first input terminal connected to one terminal of the AC voltage power supply and a common connection point of a Y connection, a second input terminal connected to the other terminal of the AC voltage power supply, and the first and second input terminals. A first resistor and a first capacitor connected in series to each other, a second capacitor and a second resistor connected in series between one terminal of the phase coil of each phase and one terminal of the AC voltage source, and one terminal of the phase coil. A first output terminal and a second output terminal provided as a common connection point of the first resistor and the first capacitor.

A second method of the present invention is a method of driving a sensorless DC motor including a rotor having a center tap-connected phase coils and a plurality of magnetic poles, wherein each pair of phase coils is connected to bridge circuits respectively coupled to each other. Sequentially applying a voltage signal, inputting each output voltage signal of the bridge circuits as inductance difference detection signals of each pair of phase coils, and inputting inductance difference detection signals of each pair of phase coils Amplifying, comparing the magnitudes of the inductance difference detection signals of the amplified pairs of phase coils, and rotating the rotor, except for the pair having the maximum magnitude of the inductance difference detection signal to rotate the rotor. Determining an initial position to magnetize.

A second device of the present invention is a drive device for a sensorless DC motor comprising a center tap-connected phase coils and a rotor having a plurality of magnetic poles, the AC voltage source for providing an AC voltage signal, and the AC voltage signal. Amplifying bridge circuits coupled to a pair of phase coils and amplifying respective inductance difference detection signals of the bridge circuits to output a difference voltage signal of the terminal voltage signals of the two phase coils as an inductance difference detection signal by inputting a. Compare the amplifiers with the amplitude of each phase inductance difference detection signal, determine the initial position of magnetizing the phase coils other than the pair of phase coils having the maximum magnitude of the inductance difference detection signal, and the rotor A commutation control unit for determining a commutation by comparing magnitudes of inductance difference detection signals at predetermined rotation angles of the commutation unit; In response to the control of the controller design and is characterized in that it comprises a driving section for providing a driving current to each phase coil.

The bridge circuit includes a first input terminal connected to one terminal of the AC voltage power supply, a first input terminal serving as a center tap, a second input terminal connected to the other terminal of the AC voltage power supply, one side terminal of each phase coil, and the second input terminal. And first and second output terminals provided between first and second resistors connected between the first and second resistors and one terminals of a pair of phase coils respectively connected to the first and second resistors.

Hereinafter, the configuration and operation of a driving apparatus of a sensorless DC motor according to embodiments of the present invention will be described with reference to the drawings.

1 shows a driving circuit of a sensorless DC motor having an Owen bridge circuit according to the present invention. 1 includes an AC voltage power supply 10, bridge circuits 12, 14, 16, amplifiers 18, 20, 22, commutation controller 24, driver 26, Y-connected upper coils 28, 30, 32.

When the rotor rotates, a drive current flows through the phase coil of the motor. Because of the resistance loss, the temperature increases as the running time increases. Increasing the temperature increases the resistance of the phase coil. The resistivity of copper is linearly dependent on temperature. This condition breaks the Owen bridge's equilibrium and makes the output voltage of the inactive phase coil unusable to determine the rotor position. Therefore, it is preferable to install the phase coils and the bridge circuits together in the motor case 34 to compensate for the breakage of the equilibrium state of the bridge circuit due to the temperature rise due to the resistance loss of the phase coils.

2 shows a detailed circuit diagram of a bridge circuit and an amplifier for one phase coil.

The bridge circuit 12 has a first input terminal C connected to one terminal of the AC voltage power source 10 and a common connection point of the Y connection, and a second input terminal to which the other terminal of the AC voltage source 12 is connected. D), a first resistor R1 and a first capacitor C1 connected in series between the first and second input terminals C and D, one terminal of the upper coil 28, and the AC voltage source ( The second capacitor (C2) and the second resistor (R2) connected in series between one terminal of the 10, the first output terminal (B) provided to one side terminal of the phase coil 280, and the first resistor ( And a second output terminal A provided as a common connection point of R1) and the first capacitor C1. The upper coil 28 is represented by an internal resistance Rx and an inductance Lx.

The amplifier 18 is a non-inverting terminal (+) connected to the first output terminal (B) through the resistor (R4) and the inverting terminal (-) connected to the second output terminal (A) through the resistor (R3) It consists of an amplifier U1. The non-inverting terminal + of the operational amplifier U1 is grounded through the resistor R5, and the output terminal is grounded through the resistor R7. A resistor R6 is connected between the inverting terminal (−) and the output terminal. The resistors R3 and R4 have the same resistance value, and the resistors R5 and R6 have a resistance value of m times that of the resistances of the resistors R3 and R4.

Each circuit constant value of the bridge circuit 18 first obtains a change in inductance having a resistance value (22.5 mA) and a range of 813 to 846 µH with respect to the phase coil 28. Based on this information, the resistance values R1 and R2 and the capacitor values C1 and C2 at the equilibrium state of the bridge system are obtained.

The voltage characteristics of the bridge system according to the applied AC voltage v (t) are as follows.

------------------------(One)

------------(2)

The values of i1 and i2 are obtained by the above expressions (1) and (2). The voltages v _A (t) and v _B (t) of the output terminals A and B are obtained as follows.

v _A (t) = v (t) -R ₁ i ₁ --------------------------- (3)

---------------------(4)

In equilibrium, the voltage at output terminal A is equal to the voltage at output terminal B. Therefore, there is no voltage difference between the two output terminals.

3 shows the configuration of the upper coils 28, 30, 32 and the magnetic rotor 36. Each phase coil is composed of two coils 28a, 28b, 30a, 3b, and 32a, 32b arranged diagonally. Thus, the six coils are arranged distributed 60 degrees on the same circumference. The magnet rotor 36 is distributed 45 degrees on the same circumference and eight magnet poles are arranged. The magnet poles are alternately arranged with the north pole and the south pole.

Therefore, if the upper coils and the magnet rotor overlap in the state shown, most of the S poles are overlapped on the upper coil 28, and most of the N poles are overlapped on the upper coil 30, but the N poles are on the upper coil 32. And S poles overlap by 1/2.

When the rotor 36 rotates in such a state, the magnetic field is changed, so that the inductance value of the phase coil is changed, and thus the voltage difference between the two output terminals appears. However, this voltage difference is too small for direct use. Therefore, a differential amplifier 18 is used to amplify this signal.

The output voltage Vout of the differential amplifier is given by

v _out = m (v _A -v _B ) ------------------------- (5)

Where m is the gain of the differential amplifier, mR / R.

The AC voltage power supply 10 is a voltage source that supplies a square wave of magnitude 10V, frequency 100kHz, and duty ratio 25%.

4 shows the amplified output voltage of the output voltage of the bridge circuit when the inductance of the phase coil is 835 µH, and FIG. 5 shows a characteristic graph of the output voltage with respect to the inductance of the phase coil.

In FIG. 5, when the inductance value is 830 μH or more, the absolute value of the maximum voltage is always greater than the absolute value of the minimum voltage. However, in the case of 835 µH or less, the opposite is true. The output voltage dependent on the inductance value is measured at 62.5 6. The reason is preferably measured after about six cycles have been applied to the system to ignore the transition state.

Fig. 6 shows a waveform diagram of the output voltage of each phase coil corresponding to the rotation angle of the magnet rotor. The solid line shows the output voltage waveform for the upper coil 28, the dotted line shows the output voltage waveform for the upper coil 30, and the dashed-dotted line shows the output voltage waveform for the upper coil 32.

In an 8-pole three-phase (6 coil) motor, phase commutation must be performed every 15 degrees of rotor rotation. As shown in Fig. 6, the voltage profiles of the three phases are well separated and at each angle the voltage of one phase is greater than the voltage of the other phases.

The commutation control unit 24 compares the magnitudes of the inductance detection signals of each of the amplified phase coils, and determines the initial position of magnetizing the other two phase coils except for the phase coil having the maximum value of the inductance detection signal.

In the stopped state, the input signal is applied sequentially to the three phases. The returned signal is then amplified and the voltage value is measured at a specific time. The voltage values of the three phases are compared to determine activating the phases based on the largest or smallest value.

At the start of the motor, the commutation determination is performed by the rotation of the rotor in the desired direction.

If the inductance detection signal of the upper coil 28 is larger than the inductance detection signal of the upper coils 30 and 32, the commutation control unit 24 controls the driving unit 26 to rotate the rotor and the upper coils 30 and 32. Magnetization is made by flowing a drive current through the circuit. At the next rotation angle of 15 degrees, since the inductance detection signal of the upper coil 30 is the largest, the upper coils 28 and 32 are activated. In rotation of the motor, an inactive coil is used as a sensor. The magnetization of the corresponding phase must be performed while the output voltage is within a certain range.

7 shows a driving circuit of a sensorless DC motor having an inductance bridge circuit according to the present invention. In FIG. 7, the apparatus includes an AC voltage power supply 40, bridge circuits 42, 44, 46, amplifiers 48, 50, 52, commutation controller 54, driver 56, a center. Tab wired upper coils 58, 60, 62. The upper coils 58, 60, 62 are installed in the motor case 64.

8 shows a detailed circuit diagram of the inductance bridge circuit. The bridge circuit 42 for detecting the inductance difference voltages of the two phase coils 58 and 60 includes a first input terminal C connected to one terminal of the AC voltage power supply 40 and a center tap, and an AC voltage. A second input terminal D connected to the other terminal of the power supply 40 and first and second resistors connected between one terminal of each phase coil 58 and 60 and the second input terminal D. First and second output terminals A provided to one terminals of a pair of phase coils 58 and 60 connected to R1 and R2 and the first and second resistors R1 and R2, respectively. B). The upper coil 58 is represented by an internal resistance R58 and an inductance L58, and the upper coil 60 is represented by an internal resistance R60 and an inductance L60.

The amplifier 48 is a non-inverting terminal (+) connected to the first output terminal (B) through the resistor (R4) and the inverting terminal (-) is connected to the second output terminal (A) through the resistor (R3) It consists of amplifier U1. The non-inverting terminal + of the operational amplifier U1 is grounded through the resistor R5, and the output terminal is grounded through the resistor R7. A resistor R6 is connected between the inverting terminal (−) and the output terminal. The resistors R3 and R4 have the same resistance value, and the resistors R5 and R6 have a resistance value of m times that of the resistances of the resistors R3 and R4.

The commutation control unit 54 compares the magnitudes of the inductance difference detection signals of each amplified phase, and determines that the inductance difference detection signal is an initial position for magnetizing the remaining phase coils except for a pair of phase coils having a maximum value. The commutation is determined by comparing the magnitudes of the inductance difference detection signals for each predetermined rotation angle of the rotor.

The driver 56 provides a driving current to each of the phase coils 58, 60, and 62 under the control of the commutation controller 54.

The output voltages of the output terminals A and B in the bridge circuit 42 can be obtained by the following equations (6) and (7).

------------------ (6)

------------------- (7)

The output voltage Vout of the amplifier is given by the following equation (6) (7).

v _out = m (v _A -v _B ) -------------------------------(8)

If the resistance and inductance of the two phase coils 58 and 60 are the same, there is no voltage difference between the two output terminals A and B. The inductance of the phase coil is changed because the relative position of the magnet pole with respect to the coil changes. Even though the resistance of the two phase coils is the same, the inductance change creates a voltage difference between the two output terminals (A, B).

When the square wave of magnitude 10V, frequency 100kHz, and duty ratio 25% is applied to the bridge circuit in the AC voltage power supply 10, the inductance difference voltage waveforms of FIGS. 9 and 10 can be obtained.

9 is a waveform diagram of the maximum voltage of each inductance bridge circuit corresponding to the rotation angle of the magnet rotor at the square wave input, Figure 10 is a minimum voltage of each inductance bridge circuits corresponding to the rotation angle of the magnet rotor at the square wave input The waveform diagram of is shown.

In FIG. 9, the solid line indicates the inductance maximum differential voltage between the upper coils 60 and 62, the dashed-dotted line indicates the inductance maximum differential voltage between the upper coils 60 and 58, and the dotted line indicates the upper coils 58 and 62. 60) shows the maximum difference voltage between inductances. In FIG. 10, the solid line indicates the inductance minimum difference voltage between the upper coils 60 and 62, the dashed-dotted line indicates the inductance minimum difference voltage between the upper coils 60 and 58, and the dotted line indicates the upper coils 58 and 62. 60) represents the minimum difference voltage between inductances.

In the stationary state, an input signal is applied to two pairs of two phase coils. The commutation based on the maximum or minimum voltage is performed to rotate the rotor by measuring and comparing the signal returned from each pair of phase coils. However, two phase coils are used to determine the rotor position and the other phase coil is magnetized. In this case the maximum voltage is used to determine the phase coil to be magnetized.

For example, when the difference voltage between the two phase coils 60-62 is greater than 62-58, 58-60, a drive current is applied to the phase coil 58 to rotate the rotor to magnetize it. At the next rotor rotation angle of 15 degrees, the upper coil 60 is activated.

If there are two maximums, it becomes difficult to determine which phase to activate. In this case, the minimum voltage is used for commutation. For example, there is a commutation change point P from the upper coil 62 to 58 at 15 degrees. The output voltage at this time is the same. However, the output voltages of 62-58 are lower than the output voltages of 60-62 and 58-60. If the commutation magnetizes the upper coil 58, the rotor will rotate in the desired direction.

11 is a waveform diagram of an inductance difference voltage between two phase coils corresponding to the rotation angle of the rotor when a sine wave is input. The solid line represents the inductance difference voltage between the two phase coils 58-60, the dashed line represents the inductance difference voltage between the two phase coils 60-62, and the dotted line represents the inductance difference voltage between the two phase coils 62-58. In FIG. 11, a sinusoidal wave of 10 V and 50 Hz is supplied from the AC voltage power supply 40 to the bridge circuit.

The difference voltage of FIG. 11 is the voltage magnitude measured at T = 15 mA when the input signal reaches the minimum value at a specific time.

For example, at 36 degrees of rotor rotation, the differential voltage between the two phase coils 62-58 is greater than the other voltage outputs. Therefore, the upper coil 60 must be magnetized to rotate the rotor. The phase coil 60 continues to magnetize while the difference voltage between the phase coils 62-58 is greater than the difference voltage of the other phase coil pairs.

It can be seen with reference to FIG. 12 that the inductance of the upper coil 60 decreases as compared with the increase of the inductance of the other two phase coils during the 28-43 degrees in which the upper coil 60 is magnetized. 12 shows the inductance according to the rotor rotation angle of each phase coil.

Fig. 13 shows the phase relationship between the input signal and the differential voltage signal under the condition L60> L58. That is, it can be seen that the input signal and the difference voltage signal have the same phase.

Fig. 14 shows the phase relationship between the input signal and the difference voltage signal under the condition L58> L60. That is, it can be seen that the input signal and the difference voltage signal have different phases.

In addition to the maximum differential voltage, such phase angle transition information can be used for correct commutation.

15 shows a magnetization sequence of phase coils. First, a positive driving current is applied to the upper coil 58 during the first 15 degrees, a negative driving current is applied to the upper coil 60 during the first 15-30 degrees, and a positive direction is applied to the upper coil 62 during the next 30 to 45 degrees. Driving current is applied. Thus, commutation is determined such that the phase coils are magnetized sequentially in the order of 58-60-62-58.

As described above, in the present invention, by detecting the change in inductance of the phase coil according to the relative position of the magnet pole of the rotor by using the bridge circuit, the weak signal can be detected more reliably and responding to the detected inductance change signal. It is possible to accurately detect the initial position of the rotor in the stationary state and the low speed mode.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (6)

In the driving device of a sensorless DC motor comprising a rotor having a Y-connected phase coils and a plurality of magnetic poles, An AC voltage source for providing an AC voltage signal; Bridge circuits coupled to the respective phase coils to input the AC voltage signal and output a difference voltage signal between a reference voltage signal and a terminal voltage signal of an upper coil as an inductance detection signal; Amplifiers for amplifying each inductance detection signal of the bridge circuits; Compare the magnitudes of the inductance detection signals of each amplified phase, determine the initial position of magnetizing the remaining two phases except the phase having the maximum value, and compare the magnitudes of the inductance detection signals at predetermined rotation angles of the rotor. A commutation controller configured to determine a commutation; And And a driving unit for providing a driving current to the pair of phase coils in response to the control of the commutation control unit. The method of claim 1, wherein the bridge circuit A first input terminal connected to one side terminal of the AC voltage power source and a common connection point of a Y connection; A second input terminal connected to the other terminal of the AC voltage power supply; A first resistor and a first capacitor connected in series between the first and second input terminals; A second capacitor and a second resistor connected in series between one terminal of the phase coil of each phase and one terminal of the AC voltage source; A first output terminal provided to one side terminal of the upper coil; And And a second output terminal provided as a common connection point of the first resistor and the first capacitor. The sensorless DC motor of claim 1, wherein the rotor has eight magnetic poles, and each phase coil is composed of two coils, and determines commutation at each rotation angle of the rotor. Drive system. In the driving device of a sensorless DC motor comprising a rotor having a center tap connected phase coils and a plurality of magnetic poles, An AC voltage source for providing an AC voltage signal; Bridge circuits respectively coupled to a pair of phase coils to input the AC voltage signal and output a difference voltage signal of a terminal voltage signal of two phase coils as an inductance difference detection signal; Amplifiers for amplifying each inductance difference detection signal of the bridge circuits; Compare the magnitudes of the inductance difference detection signals of each phase to be amplified, determine the initial position where the magnitude of the inductance difference detection signal is magnetized except for a pair of phase coils having a maximum value, and for each predetermined rotation angle of the rotor. A commutation controller for determining a commutation by comparing the magnitudes of the inductance difference detection signals; And And a driving unit for providing a driving current to each phase coil in response to the control of the commutation control unit. The method of claim 4, wherein the bridge circuit A first input terminal connected to one terminal of the AC voltage power source and a center tap; A second input terminal connected to the other terminal of the AC voltage power supply; First and second resistors connected between one side terminal of each phase coil and the second input terminal; And And first and second output terminals provided to one terminals of a pair of phase coils connected to the first and second resistors, respectively. 6. The sensorless DC motor of claim 5, wherein the rotor has eight magnetic poles, and each phase coil is composed of two coils, and determines commutation at every 15 degrees of rotation of the rotor. Drive system.