JP2004166396A - Drive device for brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size and the cost of a brushless motor and to facilitate the configuration of an integrated circuit. <P>SOLUTION: The drive device for the brushless motor detects a U-phase lower-arm current of a PWM-controlled inverter circuit 31 by a shunt resistor 31a, leads a current waveform without insulation that corresponds to a U-phase phase current of the brushless motor 4 by sample-holding the detected lower-arm current every positive peak of a carrier signal, adjusts the amplitude of a voltage command value of each phase at PWM operation so as to make a phase difference between the current waveform and a U-phase reference sine wave coincide with a phase command value from the outside, and stably performs the drive operation of the brushless motor 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a brushless motor driving device that converts a DC voltage to an AC voltage using an inverter circuit and supplies the AC voltage to the brushless motor, and more particularly to a brushless motor driving device suitable for integrated circuits.
[0002]
[Prior art]
In a brushless motor driving device, a phase difference between a terminal voltage and a winding current of the stator winding is determined without detecting a relative position between a stator winding of the brushless motor and a rotor of a permanent magnet. A method of performing a stable driving operation by controlling the value to a value is known (for example, see Patent Document 1).
[0003]
FIG. 3 shows a circuit configuration diagram of a conventional brushless motor driving device including the driving method of Patent Document 1, in which 1 is a DC power supply such as a rectified power supply, and 2 is a drive for driving the brushless motor 4. Device.
[0004]
The drive device 2 includes an inverter circuit 21 having a configuration in which U-phase, V-phase, and W-phase arms are connected in bridge by connecting an anti-parallel circuit of an IGBT and a diode as self-extinguishing elements in series. A shunt resistor 21a for detecting a U-phase output current, that is, a U-phase current of the brushless motor 4, an insulating circuit 22 for insulating and amplifying the voltage between both ends of the shunt resistor 21a, and outputting the voltage; A three-phase reference sine wave circuit 23 for generating a reference sine wave of each phase (U phase, V phase, W phase), and a U-phase reference sine wave output from the three-phase reference sine wave circuit 23 and an insulating circuit 22 A phase difference detection circuit 24 for detecting a phase difference from a current waveform corresponding to the U-phase current to be output; and a gain for each of the three-phase reference sine waves so that the phase difference becomes an external phase command value. A three-phase voltage command value circuit 25 for generating a three-phase voltage command value, a carrier generator 26 for generating a triangular carrier signal, and a three-phase voltage signal output from the three-phase voltage command value circuit 25 A comparison circuit 27 that performs PWM control with each voltage command value, and on / off each IGBT that forms the inverter circuit 21 based on the three-phase PWM-controlled logic signals output from the comparison circuit 27 And a gate drive circuit 28 for generating a drive signal for performing the operation. These circuits are all formed by a known technique.
[0005]
[Patent Document 1]
JP-A-2002-165484 (page 4-6, FIG. 1)
[0006]
[Problems to be solved by the invention]
In the circuit configuration of the conventional brushless motor driving device shown in FIG. 3, the insulating circuit 22 must be provided in the path from the shunt resistor 21a to the phase difference detecting circuit 24, and the insulating circuit 22 has a complicated circuit configuration. However, there is a problem that the cost and the size of the entire driving device are increased. In addition, by providing a hole CT including a magnetic circuit, a Hall element, and the like instead of the above-described shunt resistor 21a, the above-described insulating circuit 22 can be omitted. A new problem arises, which is a factor of upsizing and enlargement.
[0007]
An object of the present invention is to provide a brushless motor driving device that solves the above-mentioned problems.
[0008]
[Means for Solving the Problems]
In the first invention, the upper and lower arms of each phase are each formed by an anti-parallel circuit of a self-arc-extinguishing element and a diode, and a DC voltage is formed by using an inverter circuit having a bridge connection between the upper and lower arms. Is converted into a desired AC voltage by PWM control, and in a brushless motor driving device that supplies the AC voltage to the brushless motor, arm current detection means for detecting at least one of the phase arm currents of the respective phases; Current waveform generating means for generating a current waveform corresponding to the phase current of the phase from the detected arm current; and a reference sine wave of a phase corresponding to the generated current waveform among reference sine waves of the respective phases. Phase difference detecting means for detecting a phase difference between the current and the current waveform, and a reference sine for each phase so that the detected phase difference becomes a desired value specified from the outside. The is characterized in that a voltage command value generating means for generating a voltage command value of the gain obtained by multiplying each phase.
[0009]
According to a second invention, in the brushless motor driving device according to the first invention, the arm current detection means comprises a shunt resistor.
[0010]
According to a third aspect, in the brushless motor driving device according to the first or second aspect, the current waveform generating means samples the detected arm current in synchronization with a carrier signal at the time of the PWM control. , A current waveform corresponding to the phase current of the phase is derived.
[0011]
According to a fourth aspect, in the brushless motor driving device according to the first or second aspect, the arm current detecting means detects an arm current flowing on the negative side of the DC voltage input to the inverter circuit, and The waveform generation means derives a current waveform corresponding to a phase current of the phase by sampling and holding the detected arm current in synchronization with a triangular wave carrier signal at the time of the PWM control at a positive peak. Features.
[0012]
According to the present invention, it is possible to derive a phase current waveform from the arm current of the inverter circuit. As a result, as will be described later, it is possible to reduce the size of the brushless motor driving device and to reduce the current detecting means. It is not necessary to insulate the path between the power supply and the current waveform generating means.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram of a drive device for a brushless motor according to an embodiment of the present invention, and corresponds to claims 1 to 4. In this figure, the circuit is the same as the conventional circuit shown in FIG. Those having functions are denoted by the same reference numerals, and description thereof will be omitted.
[0014]
In other words, the driving circuit 3 shown in FIG. 1 includes a three-phase reference sine wave circuit 23, a three-phase voltage command value circuit 25, and a positive vertex of a triangular wave carrier signal in order to correspond to claim 3 or claim 4. Generator 26a, a comparison circuit 27, and a gate drive circuit 28, which are provided with a function of outputting a sample signal synchronized with the IGBT, a U-phase, a V-phase, and a W-phase in which an anti-parallel circuit of an IGBT and a diode is connected in series. An inverter circuit 31 having a configuration in which phase arms are bridge-connected, a shunt resistor 31a for detecting an arm current of the lower arm of the U phase of the inverter circuit 31 according to claim 2 or 4, and a shunt resistor 31a. A current waveform generating circuit 32 for deriving a current waveform corresponding to a U-phase current based on the voltage across the shunt resistor 21a and the sample signal, and a three-phase reference sine wave circuit 23 And a phase difference detection circuit 33 for detecting a phase difference φ between the current waveform corresponding to the U-phase current is the U-phase reference sine wave and the current waveform generating circuit 32 of an output for outputting.
[0015]
The operation of the drive circuit 3 shown in FIG. 1 will be described below with reference to the operation waveform diagram shown in FIG.
[0016]
While the brushless motor 4 is rotating together with a load (not shown), the PWM by the U-phase voltage command value generated by the three-phase voltage command value circuit 25 and the triangular wave-shaped carrier signal generated by the carrier generator 26a will be described later. The control is performed by the comparison circuit 27, and the PWM control result turns on or off the IGBTs of the upper and lower arms of the U-phase of the inverter circuit 31 via the gate drive circuit 28. As a result, the voltage across the shunt resistor 31a, that is, the waveform of the U-phase lower arm current is as shown in FIG.
[0017]
In the waveform of the U-phase arm current, in order to make the entire sinusoidal waveform correspond to the waveform of the U-phase current, the value of the region above the zero point (positive region) shown in FIG. , And a value in a region (negative region) below the zero point shown in FIG. 4 indicates a case where the current is flowing through the IGBT of the U-phase lower arm. Therefore, the period in which the waveform is at the zero point is when a current is flowing through the IGBT or diode of the U-phase upper arm.
[0018]
In the above-described PWM control, as the magnitude relationship between the U-phase voltage command value and the carrier signal shown in FIG. 2, during the period of U-phase voltage command value ≧ carrier signal, the IGBT or the diode of the U-phase upper arm is in the ON state. Since the IGBT or the diode of the U-phase lower arm is in the ON state during the period of the U-phase voltage command value <the carrier signal, at the positive peak of the triangular wave-shaped carrier signal as shown in FIG. The IGBT or the diode is in the ON state. Therefore, the U-phase lower arm current shown in FIG. As a result, a waveform of the detection current as shown in FIG. 2 is obtained, and the waveform of the detection current has an average value delayed by the half cycle of the carrier signal, It has become the waveform corresponding to the current. That is, the phase difference detection circuit 33 may detect the phase difference φ from the U-phase reference sine wave while correcting the delay.
[0019]
In the circuit configuration shown in FIG. 1, the phase difference φ of only the U phase is detected as described above, and the three-phase voltage command value circuit 25 controls the three-phase voltage command value circuit 25 so that the detected value φ becomes an external phase command value. For example, a proportional-integral calculation of the deviation is performed, and the calculation result is used as a gain to multiply the reference sine wave of each of the three phases by the gain to obtain a three-phase voltage command value. A shunt resistor is provided on the lower arm, and three sets of current waveform generation circuit 32 and three phase difference detection circuits 33 are provided. The three-phase voltage command value circuit 25 individually performs the above-described arithmetic operation based on the phase difference of each phase. Is also good.
[0020]
【The invention's effect】
According to the present invention, it is possible to derive a phase current waveform from an arm current of an inverter circuit without passing through an insulating circuit, and as a result, it is possible to reduce the size and cost of a drive device for this type of brushless motor. Therefore, the driving circuit of the brushless motor is suitable for forming an integrated circuit.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a brushless motor driving device showing an embodiment of the present invention; FIG. 2 is a waveform diagram illustrating the operation of FIG. 1; FIG. 3 is a circuit configuration diagram of a brushless motor driving device showing a conventional example; [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2,3 ... Drive device, 4 ... Brushless motor, 21 ... Inverter circuit, 21a ... Shunt resistance, 22 ... Insulation circuit, 23 ... Three-phase reference sine wave circuit, 24 ... Phase difference detection circuit, 25 ... Three-phase voltage command value circuit, 26, 26a carrier generator, 27 comparison circuit, 28 gate drive circuit, 31 inverter circuit, 31a shunt resistor, 32 current waveform generation circuit, 33 phase difference detection circuit.

Claims (4)

The upper and lower arms of each phase are each formed by an anti-parallel circuit of a self-arc-extinguishing element and a diode, and a DC voltage is controlled by PWM control using an inverter circuit in which the upper and lower arms are bridge-connected. In a brushless motor drive device that converts the AC voltage to a voltage and supplies the AC voltage to the brushless motor,
Arm current detecting means for detecting an arm current of at least one of the phases;
Current waveform generating means for generating a current waveform corresponding to the phase current of the phase from the detected arm current,
Among the reference sine waves of the respective phases, a phase difference detecting means for detecting a phase difference between the reference sine wave of the phase corresponding to the generated current waveform and the current waveform,
Voltage command value generation means for generating a voltage command value of each phase obtained by multiplying the reference sine wave of each phase by a gain so that the detected phase difference becomes a desired value specified from the outside. A drive device for a brushless motor, characterized in that: The drive device for a brushless motor according to claim 1,
A drive device for a brushless motor, wherein the arm current detecting means comprises a shunt resistor. The brushless motor driving device according to claim 1 or 2,
The brushless motor, wherein the current waveform generating means derives a current waveform corresponding to a phase current of the phase by sampling the detected arm current in synchronization with a carrier signal at the time of the PWM control. Control device. The brushless motor driving device according to claim 1 or 2,
The arm current detecting means detects an arm current flowing on the negative side of the DC voltage input to the inverter circuit,
The current waveform generating means derives a current waveform corresponding to a phase current of the phase by sampling and holding the detected arm current in synchronization with a triangular carrier signal at the time of the PWM control at a positive peak. A controller for a brushless motor.

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