JPH10243686A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a starting time and reduce vibration and starting current of a motor at starting operation, by denaturing the base signal into shift type base signal where the time width of each pattern of the base signal is changed, at start, and controlling AC voltage by this shift type base signal. SOLUTION: In starting operation, a frequency commander 8 outputs a frequency command for controlling the frequency of a DC brushless motor(BLM), and a waveform generator 9 generates a base signal, based on the frequency command. At this time, the waveform generator 9 generates a base signal by only the frequency command. The waveform denaturer 10 denatures the shift type of base signal where the time width of each pattern of this base signal is changed. PWM(pulse width modulation) base driver 11 drives switching elements 25u-25z, based on this shift type base signal. Hereby, the starting frequency can be reduced, and the starting time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for controlling the frequency of a brushless DC motor.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional inverter device for controlling the frequency of a brushless DC motor.
In this figure, an inverter device includes a commercial power supply 1 for outputting an AC, an inductor element 2, a converter unit 3 for rectifying the AC from the commercial power supply 1, and a smoothing capacitor 4 for smoothing the DC output from the converter unit 3. An inverter unit 5 that converts the DC voltage smoothed by the smoothing capacitor 4 into a pseudo three-phase AC voltage and outputs it to the DC brushless motor 6
An inverter frequency control unit 20b for controlling the frequency of the pseudo AC voltage output from the inverter unit 5,
DC brushless motor (hereinafter referred to as “BLM”) 6
And a phase detection unit 7 for detecting the phase of the rotor of FIG. The inverter unit 5 includes six switching elements 25u to 25z that open and close at a high speed.

In the inverter device configured as described above, an AC voltage is input from the commercial power supply 1 via the inductor element 2, rectified by the converter unit 3, and then converted into a DC output by the smoothing capacitor 4. can get. The DC voltage obtained at both ends of the smoothing capacitor 4 is converted into a frequency-variable pseudo three-phase AC voltage by the inverter unit 5 and BL
Output to M6. The rotation speed of the BLM 6 is
Is controlled by changing the frequency (hereinafter, referred to as “inverter frequency”) of the pseudo AC voltage output from the inverter. This inverter frequency is controlled by the inverter frequency control unit 20b.

[0004] The inverter frequency control section 20b includes a frequency command section 8, a waveform generation section 9, and a PWM base drive section 11. The frequency command section 8 outputs a frequency command, which is a control signal for controlling the inverter frequency, to the waveform generating section 9 and the PWM base drive section 11.
The waveform generator 9 generates a base signal for controlling the opening and closing of the switching elements 25u to 25z based on the frequency command and the phase signal as the phase detection value from the phase detector 7. The PWM base drive unit 11 performs pulse width modulation (Pulse Width Modulaton) on the base signal based on the frequency command from the frequency command unit 8, and drives the switching elements 25 u to 25 z of the inverter unit 5. As described above, the opening / closing of the switching elements 25u to 25z is controlled by the PWM base drive unit 11, whereby the frequency of the pseudo AC voltage output from the inverter unit 5 (inverter frequency) is controlled.

In the inverter frequency control section 20b,
The control of the inverter frequency during the start-up operation is different from the control of the inverter frequency during the normal operation. Specifically, during the start-up operation, the waveform generator 9 generates a base signal based on the frequency command from the frequency
The WM base drive unit 11 performs pulse width modulation on the base signal based on a duty ratio according to a frequency command from the frequency command unit 8, and uses the pulse signal generated by the pulse width modulation to switch the switching element 25u of the inverter unit 5. Open loop control for driving 〜25z. Also,
During normal operation, the waveform generator 9 generates a base signal based on the phase signal from the phase detector 7, and the PWM base drive 11 detects the frequency of the base signal.
By comparing the detected value with the frequency command from the frequency command unit 8 and increasing or decreasing the duty ratio for normal operation, a closed loop control for controlling the frequency of the pseudo AC voltage output from the inverter unit 5 is achieved.

Here, the base signal generated by the waveform generator 9 will be described. The base signal includes six signals Tu to Tz for driving the six switching elements 25u to 25z, respectively. Each of the base signals Tu to Tz is Low.
At the level (hereinafter, referred to as “L”), the switching elements 25 u to 25 z are turned “on”, and at the High level (hereinafter, referred to as “H”), the switching element 2 is turned on.
Turn off 5u-25z. The “L” portions of the base signals Tu to Tz are pulse-width modulated by the PWM base drive unit 11 so that the switching elements 25 u to
A pulse signal for driving 25z is generated. The base signal has six basic patterns PTN1 to PTN6 in one cycle, and the reciprocal of one cycle of the base signal is the inverter frequency. During the start-up operation, the time widths T12, T22, T32, T
42, T52 and T62 are controlled almost equally during one cycle, and even during normal operation, each pattern PTN1 is controlled.
~ Time widths T'12, T'22, T'32, T'42, T'5 of PTN6
2. T'62 is controlled to be substantially equal in one cycle. The switching from the start-up operation to the normal operation is performed after the base signal has been completed for a predetermined period. Therefore, the time Ts coincides with the end of the sixth pattern PTN6.

FIG. 6 shows a schematic configuration diagram of the phase detector 7.
The phase detector 7 includes primary low-pass filters 31a to 31c
, Comparison circuits 32a to 32c, and insulation sections 33a to 33c
, Resistors 34a to 34c, 35a to 35c, capacitors 36a to 36c, input terminals 40a to 40c, and output terminals 42a to 42c. Input terminal 40
a, 40b, and 40c respectively have the U phase and V phase of BLM6.
The phase and W-phase voltages Vu, Vv, Vw are input. The reference bus N of the inverter device is a ground GND for providing a reference potential.
Are connected to the input terminals 4
A voltage between 0a-40c and ground GND is input.
The voltage input to the input terminal 40a is a resistor 34a, 35a
, The DC component is cut by the capacitor 36a, and the DC component is filtered by the primary integrating circuit of the primary low-pass filter 31a. Similarly, input terminal 40
b, 40c are also filtered, and the respective filtered voltages are compared with the comparison circuits 32a to 32c.
32c, the BLMs are insulated from each other through the insulating units 33a to 33c to insulate the high voltage system and the low voltage system in the apparatus, and through the output terminals 42a, 42b, and 42c.
6 are output as phase signals Fw, Fu, and Fv of the U, V, and W phases.

FIG. 7 shows an example of input and output waveforms in the phase detecting section 7 configured as described above. FIG. 7A shows the voltage input to the phase detection unit 7, in this case, only the fundamental frequency component obtained by removing harmonics of the U-phase voltage Vu based on the neutral point of the armature winding inside the BLM 6. Shown in waveforms,
FIG. 7B shows the waveform of the phase signal Fu which is the result of detecting the phase of the input voltage Vu. The phase detector 7 outputs an “H” signal as a phase signal when the input voltage is positive, and outputs an “L” signal when the input voltage is negative. Therefore, the zero value point of the input voltage Vu in FIG. 7A should match the rising edge or the falling edge of the phase signal Fu in FIG. 7B, but in FIG. Indicates that the phase signal Fu is advanced by Δβ. As described above, in the phase detection unit 7, a phase difference Δβ (hereinafter, the phase difference Δβ is referred to as a “phase lead angle”) occurs between the input and the output. This is due to a primary low-pass filter, a capacitor, a comparison circuit, a resistor, and the like that constitute the phase detection unit 7. Therefore, the phase detection unit 7
6 has a characteristic of outputting as a detection result a signal having a phase advanced by a phase advance angle from the actual phase (hereinafter, this characteristic is referred to as “phase advance characteristic”).

Further, this phase lead characteristic depends on the frequency of the input voltage (here, the inverter frequency). FIG.
Shows the relationship between the frequency of the input voltage of the phase detector 7 and the phase lead angle. In this figure, the horizontal axis represents the frequency input to the phase detection unit 7, that is, the inverter frequency, and the vertical axis represents the phase signals Fu, Fv,
Fw represents the phase lead angle. As shown in this figure, as the inverter frequency decreases, the phase lead angles Fu, F
There is a characteristic that v and Fw increase.

FIG. 9 shows a timing chart of the base signal and the phase signal near the time of switching from the starting operation to the normal operation. In this figure, the operation is switched from the start-up operation to the normal operation at the time boundary Ts (coincident with the rise of the base signal Tx).

At the time of the start-up operation, the waveform generating section 9 does not refer to the phase signal from the phase detecting section 7 but only at the predetermined timing as shown in FIG. The base signal is sequentially changed from the pattern PTN1 to the sixth pattern PTN6. During normal operation, the waveform generator 9 sequentially changes each pattern of the base signal based on the phase signal. That is, the waveform generator 9
Generates the first pattern PTN1 immediately after switching from the start-up operation to the normal operation (immediately after the time boundary line Ts), and generates the second pattern PTN1 at the rising edge of the phase signal Fu.
2, a third pattern PTN3 at the falling edge of the phase signal Fw, and a fourth pattern PTN3 at the rising edge of the phase signal Fv.
, The fifth pattern PTN5 at the falling edge of the phase signal Fu, the sixth pattern PTN6 at the rising edge of the phase signal Fw, and the phase signal Fv.
Respectively generate the first patterns PTN1 at the falling edge of. FIG. 9 shows a pattern of the base signal in a case where the BLM 6 can be activated by sequentially generating each pattern of the base signal according to the change of each phase signal Fu to Fw after the time boundary Ts. Is shown.

However, in the conventional inverter device, the transition from the start-up operation to the normal operation cannot be performed due to the phase advance characteristic of the phase detection unit 7, and the BLM 6 may not be started. FIG. 10 shows a timing chart of the base signal and the phase signal when the activation of the BLM 6 becomes impossible. FIG. 10 illustrates a case of “low-frequency start” in which the BLM 6 is started at a low inverter frequency. As described above, due to the phase advance characteristic of the phase detection unit 7, the phase advance angle of the phase signal becomes larger as the inverter frequency becomes lower, and the phase signal becomes shorter in time (see FIG. 9).
Or, it moves leftward in FIG. for that reason,
In the case of the low-frequency start shown in FIG. 10, since the inverter frequency is low immediately before switching from the start operation to the normal operation,
The phase lead angle becomes larger, the rising edges of the phase signals Fu to Fw move in the direction of earlier time, and the phase signal Fu rises before the time Ts. As a result, since there is no rising edge of the phase signal Fu after the time boundary line Ts, the first pattern PTN1 is not switched to the second pattern PTN2. As a result, the brake torque acts on the BLM6, and the rotational movement of the BLM6 Stops at the stop time line Te and cannot be started. As described above, in the closed loop control of the inverter device, the startup of the inverter device becomes impossible due to the phase lead characteristic of the phase detection unit 7.

Therefore, in order to start the inverter device, it is necessary that a rising edge of the phase signal Fu exists after the start-up operation is switched to the normal operation, that is, after the time boundary Ts. Assuming that the time from the time boundary Ts to the rising edge of the phase signal Fu is a phase margin Δθ, a necessary condition for starting is that Δθ> 0. Further, since the phase advance angle of the phase signal Fu changes according to the inverter frequency due to the phase advance characteristic of the phase detection unit 7, the magnitude of the phase margin Δθ is determined by the value of the frequency immediately before switching from the start-up operation to the normal operation. It is determined. Determine this phase margin Δθ,
The frequency immediately before switching from the startup operation to the normal operation is referred to as “start switching frequency”, and the inverter frequency immediately before switching from the startup operation to the normal operation is referred to as “start frequency”. In the case of the conventional inverter device, since the time width of each pattern of the base signal is equal, the start switching frequency is equal to the start frequency.

[0014]

Therefore, BLM6
, It is necessary to set the start switching frequency (start frequency) to a high value so as to satisfy the phase margin Δθ> 0. However, when the start switching frequency is set to be high, the following problem occurs. (1) It is necessary to gradually increase the inverter frequency from a relatively low value to a start switching frequency in response to a frequency command from a frequency command unit at the time of start operation. Therefore, if the start switching frequency is high, the start time becomes longer accordingly. . (2) Since the BLM is over-excited during the start-up operation, the higher the start-up switching frequency, the greater the vibration of the BLM during the start-up operation. (3) The required start-up torque increases as the start-up switching frequency increases due to the viscosity coefficient inside the BLM. Further, since the BLM is over-excited, the start-up current increases.

For this reason, it is desired that the start switching frequency satisfies the condition of the phase margin Δθ> 0 and is set to a value as low as possible. However, the phase margin Δθ =
The value of the frequency that becomes 0 is determined by the phase lead characteristic of the phase detection unit 7, and this value is set to the frequency z (point C in FIG. 8).
Then, in order to satisfy the phase margin Δθ> 0, the following relationship needs to be satisfied. Start switching frequency (start frequency)> frequency z (21) Therefore, at present, there is a problem that the start switching frequency (start frequency) cannot be reduced below the frequency determined by the phase lead characteristic of the phase detector 7. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the starting frequency of a DC brushless motor to shorten the starting time and reduce the vibration of the motor during the starting operation. And to provide an inverter device with reduced starting current.

[0017]

An inverter device according to the present invention includes a switching element, converts a DC voltage into a pseudo AC voltage by opening and closing the switching element, and outputs the pseudo AC voltage to a brushless DC motor. DC-to-AC conversion means, a phase detection characteristic having a phase lead characteristic dependent on the frequency of the pseudo AC voltage, detecting a rotation phase of the brushless DC motor, and outputting rotation phase information, and the DC-to-AC conversion means And frequency control means for controlling the frequency of the AC voltage output by the brushless DC motor. The frequency control means outputs a frequency command for performing frequency control of the AC voltage applied to the brushless DC motor. Frequency command means for generating a base signal for controlling the frequency based on the frequency command and the rotational phase information; A waveform generating means for performing, based on the base signal and the frequency command, a waveform transforming means for transforming the base signal into a shift-type base signal, and a pulse width modulation of the shift-type base signal based on the frequency command; PWM base drive means for controlling opening and closing of the switching element by a width-modulated signal.

Further, in the inverter device, the base signal output from the waveform generating means has six patterns of uniform width in one cycle, and the waveform modifying means converts the base signal into The width of the final pattern during the start-up operation of the six patterns may be reduced, and a modified base signal may be output so that the length of one cycle does not change.

Further, in the inverter device, the waveform modifying means outputs the shift-type base signal, which is a modification of the base signal output from the waveform generating means, during a start-up operation of the brushless DC motor,
During the normal operation after the start-up operation, the base signal output from the waveform generating means may be output as it is.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an inverter device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration diagram of the inverter device. The inverter device of the present embodiment is different from the inverter frequency control unit 20b of the conventional inverter device shown in FIG.
A waveform modifying unit 10 is provided between the M base drive unit 11 and a frequency command from a frequency command unit 8 is input to the waveform modifying unit 10. The waveform transforming section 10 transforms the base signal input from the waveform generating section 9 into a shift-type base signal, and outputs the shifted base signal to the PWM base drive section 11. The shift type base signal will be described later. The other components of the inverter device according to the present embodiment are the same as those described in the related art, and thus detailed description of the operation of each component is omitted here.

Hereinafter, the operation of the inverter device of the present embodiment will be described. FIG. 2 shows a timing chart of the shift-type base signal or the base signal output from the waveform modifying unit 10 near the transition from the start-up operation to the normal operation.
In this figure, the start operation is switched to the normal operation at the time boundary Ts. The signals T'u to T'z are shift-type base signals or base signals output from the waveform transforming unit 10, and are signals for controlling the switching elements 25u to 25z, respectively.

First, the operation during normal operation will be described. In the normal operation, the frequency command unit 8 outputs a frequency command to control the rotation speed of the BLM 6. The waveform generator 9 generates a base signal based only on the phase signals Fu to Fw from the phase detector 7. The waveform transforming section 10 includes a waveform generating section 9
Base signal input from the PWM base drive unit 11
Output as is. The PWM base drive unit 11
The switching elements 25u to 25z of the inverter unit 5 are driven based on the base signals T'u to T'z from the waveform modifying unit 10.

The pattern of the base signals T'u to T'z at this time is represented by the time boundary Ts in the timing chart of FIG.
This is the pattern shown below. Here, assuming that the time widths for the first pattern PTN1 to the sixth pattern PTN6 are T′10 to T′60, respectively,
The time widths T'10 to T'60 of the PTN 6 are controlled to be substantially equal.

Next, the operation during the start-up operation will be described.
In the start-up operation, the frequency command section 8 outputs a frequency command for controlling the frequency of the BLM 6, and the waveform generating section 9 generates a base signal based on the frequency command. At this time, the waveform generating section 9 does not use the phase signal from the phase detecting section 7 and generates a base signal only by the frequency command. The waveform altering unit 10 alters a shift-type base signal in which the time width of each pattern of the base signal is changed. The PWM base drive unit 11 drives the switching elements 25u to 25z based on the shift type base signal. Hereinafter, the shift type base signal will be described.

FIG. 3 shows a pattern of a base signal (hereinafter, referred to as a base signal pattern).
It is called “base pattern”. ) And a pattern of a shifted base signal obtained by transforming the base signal (hereinafter referred to as a “shifted base pattern”) for one cycle. As shown in FIG. 3A, the shift type base signal has six patterns in one cycle similarly to the base signal. That is, the first to sixth patterns PTN1 ′ to
It has PTN 6 '. As shown in FIG. 3, the time widths T10 to T60 of each pattern of the shift type base signal are modified based on the time width T of the base patterns PTN1 to PTN6. The metamorphic condition at this time will be described later.

In FIG. 2, the pattern of the shift type base signal is shown before the time boundary Ts. Here, for example, in the first pattern PTN1 ′,
The shift type base signals T'w and T'y are "L", and the other shift type base signals T'u, T'v, T'x and T'z are "H". The waveform modifying section 10 converts the shift-type base signal into a first signal.
From the pattern PTN1 'to the sixth pattern PTN6'. The inverter repeats this cycle by a predetermined number in the start-up operation, and shifts to the normal operation after the end of the predetermined cycle. The transformation conditions of the shift-type base signal are shown below. (A) The length of one cycle of the base pattern and the shift type base pattern is the same. That is, T10 + T20 + T30 + T40 + T50 + T60 = T × 6 (1) (b) T10 ≧ T20 ≧ T30 ≧ T40 ≧ T50 ≧ T60 (2) (c) T10> T (3) (d) 0 <T60 <T (4) The frequency transformation unit 10 transforms the base pattern into a shift base pattern based on the above relationship.

The time width T of the shift type base pattern
The following relationship exists between 10 to T60 and the time width T of the base pattern. T10 = α1 × T (5a) T20 = α2 × T (5b) T30 = α3 × T (5c) T40 = α4 × T (5d) T50 = α5 × T (5e) T60 = α6 × T (5f) Here, α1 to α6 are metamorphic coefficients, each of which takes a positive value. The following conditions are satisfied by the conditions (a) to (d) and the expressions (5a) to (5f). (A ′) α1 + α2 + α3 + α4 + α5 + α6 = 6 (6) (b ′) α1 ≧ α2 ≧ α3 ≧ α4 ≧ α5 ≧ α6 (7) (c ′) α1> 1 (8) (d ′) 0 <α6 <1 … (9)

The waveform modifying section 10 generates a shift type base pattern from the base pattern using the values of the modifying coefficients α1 to α6 satisfying the conditions (a ′) to (d ′). That is, when the first base pattern PTN1 is output from the waveform generating section 9, the waveform modifying section 10 outputs the first shift-type base pattern PTN1 ', and the time width is determined based on the frequency command from the frequency command section 8. T is calculated and the transformation coefficient α1 ~
By calculating T10 to T60 using α6, the subsequent shift type base pattern is output.

Here, for convenience of explanation, in the base signal or the shift-type base signal, the frequency based on only the sixth pattern is referred to as a "differential frequency" and is distinguished from the "inverter frequency" which is a frequency for one cycle. In the prior art, each pattern PTN1 of the base signal during the start-up operation is
Since PTN6 have the same time width,
The “inverter frequency” and the “differential frequency” are equal. The frequency immediately before switching from the start-up operation to the normal operation, that is, the start-up switching frequency is the sixth base pattern PT which is a shift type base pattern immediately before the time boundary Ts.
It is almost equal to the differential frequency of N6 '. For this reason, in the present embodiment, the differential frequency, that is, the start switching frequency can be set higher than the start frequency by generating the shift-type base pattern at the time of the start operation, thereby suppressing the start frequency lower. The phase margin Δθ can be made larger than before.

As described in the prior art, the condition for shifting from the start operation to the normal operation is that the start switching frequency satisfies the equation (21). When the shift-type base signal is used, the activation switching frequency is the differential frequency of the shift-type base pattern PTN6 ′, and therefore the following expression is established from Expression (21). Differential frequency of shift type base pattern PTN6 ′> frequency z (10)

The differential frequency of the base pattern PTN6 is as follows. The differential frequency of the base pattern PTN6 = 1 / T / 6 (11) Therefore, the differential frequency of the shift type base pattern PTN6 'is as follows. Differential frequency of shift type base pattern PTN6 '= 1 / T60 / 6 = 1 / (T.alpha.6) / 6 = (1 / T / 6) /. Alpha.6 = frequency of base pattern PTN6 / .alpha.6 (12) In the example, since the starting frequency, that is, the inverter frequency of the base signal is equal to the differential frequency of the base pattern PTN6, the starting frequency = the differential frequency of the base pattern PTN6 = the differential frequency of the shift type base pattern PTN6 ′ · α6 (13) Expression (10) ) And equation (13), the starting frequency> frequency Z · α6 (0 <α6 <1) (14). The above equation shows the condition of the frequency when the shift type base pattern is used. Since the transformation coefficient α6 is a value smaller than 1, the starting frequency can be set lower than that of the conventional one.

For example, when the frequency at which the phase margin Δθ = 0 is the frequency z (point C in FIG. 8), the starting frequency is lower than the frequency z and the frequency y (point B in FIG. 8) is activated. Think. In this case, in the conventional inverter device, starting cannot be performed because the starting frequency y is lower than the frequency z.
In the inverter device of the present embodiment, even if the start frequency is the frequency y, the start can be started by setting the start switching frequency to a value higher than the frequency z. Assuming that the startup switching frequency at this time is x (point A in FIG. 8), the following equation holds. y = 1 / T / 6 (15) x ≒ 1 / T60 / 6 = 1 / T / 6 × T / T60 = y / α6 (16) Therefore, α6 ≒ y / x (0 <α6 <1) ... (17) Using α6 obtained by the above equation, the condition (a ′)
The other metamorphic coefficients α1 to α5 are determined so as to satisfy (c ′), and a shift-type base pattern is generated based on the metamorphic coefficients α1 to α6 determined in this manner. At this time, the phase margin Δθ0 in FIG. Δθ0 ≒ ca> 0 (18)

FIG. 4 shows a specific example of the shift base pattern. Here, y / x = 0.3 (19a) α1 = α2 = α3 = 1.6 (19b) α4 = 0.6 (19c) α5 = α6 = 0.3 (19d) For example, if the frequency x = 10, the frequency y =
It becomes 3. At this time, the shift type base pattern PTN1 ′
The time width T11 to T61 of PTN6 'is as follows: T = 0.05556 (20a) T11 = T21 = T31 = 1.6 × T = 0.88989 (20b) T41 = 0.6 × T = 0.03333 .. (20c) T51 = T61 = 0.3 × T = 0.01667 (20d)

In the present embodiment, the shift type base signal is modified so that the time width of the sixth pattern PTN 6 ′ is minimized, but this is the end of the sixth pattern PTN 6 ′ of the shift type base signal. This is because the mode is switched to the normal operation later.
Modification may be made so that the time width is minimized, and the same effect is obtained.

As described above, the inverter device of this embodiment modifies the shift type base signal in which the time width of each pattern of the base signal is changed in the frequency control of the DC brushless motor 6 in the start mode. This allows
Since the driving of the switching elements 25u to 25z of the inverter unit 5 is controlled, the starting switching frequency can be set high while the starting frequency of the pseudo AC voltage applied to the DC brushless motor 6 is kept low, and the phase margin Can be higher. Therefore, the DC brushless motor 6 can be started at a low frequency.

[0036]

According to the inverter device of the present invention, DC
In the inverter frequency control unit for controlling the frequency of the pseudo AC voltage output to the brushless motor, at the time of start-up, provided a waveform transformation means for transforming the base signal into a shift type base signal in which the time width of each pattern of the base signal is changed, The frequency control of the AC voltage is performed by the shift type base signal. As a result, the starting frequency can be reduced, so that low-frequency starting can be performed, so that the starting time can be reduced, the vibration of the DC brushless motor at the time of starting and the starting current can be reduced. In addition, DC associated with vibration reduction
It is also possible to improve the durability of the brushless motor and peripheral devices and to reduce the cost by reducing the capacity of each element due to the reduction of the starting current.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an inverter device according to an embodiment.

FIG. 2 is a timing chart of a base pattern and a shift-type base pattern according to the embodiment.

FIG. 3 is a diagram illustrating a relationship between time widths of a base pattern and a shift-type base pattern according to the embodiment;

FIG. 4 is a timing chart of a specific example of a shift base pattern.

FIG. 5 is a schematic configuration diagram of a conventional inverter device.

FIG. 6 is a schematic configuration diagram of a conventional phase detection unit.

FIG. 7 is a diagram showing an input voltage waveform and an output signal waveform of a phase detection unit.

FIG. 8 is a diagram showing a phase lead angle-frequency characteristic of a phase detection unit.

FIG. 9 is a timing chart of a base signal and a phase signal when the BLM can be activated.

FIG. 10 is a timing chart of a base signal and a phase signal when activation of a BLM becomes impossible.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Inductor, 3 ... Converter part, 4 ... Smoothing capacitor, 5 ... Inverter part, 6
... DC brushless motor (BLM), 7 ... Phase detector, 8 ... Frequency commander, 9 ... Waveform generator, 10 ...
Waveform altering section, 11 PWM base drive section, 20
a: Inverter frequency control unit (the present invention), 20b: Inverter frequency control unit (conventional), 25u to 25z: Switching element, 31a to 31c: Primary low-pass filter, 32a to 32c: Comparison circuit, 33a to 33c: Insulation unit , 34a to 34c, 35a to 35c ... resistance, 3
6a to 36c: capacitor, 40a to 40c: input terminal, 42a to 42c: output terminal, Te: stop time line, Ts: time boundary line.

Claims (3)

[Claims] A switching device for converting a DC voltage into a pseudo AC voltage by opening and closing the switching device;
DC / AC converting means for outputting the pseudo AC voltage to the brushless DC motor, and having a phase lead characteristic dependent on the frequency of the pseudo AC voltage, detecting a rotation phase of the brushless DC motor, and obtaining rotation phase information. In an inverter device comprising: a phase detection unit that outputs the voltage; and a frequency control unit that controls a frequency of the AC voltage output by the DC / AC conversion unit, the frequency control unit includes: Frequency command means for outputting a frequency command for performing frequency control, waveform generating means for generating a base signal for controlling the frequency based on the frequency command and the rotational phase information, the base signal and the frequency A waveform modifying means for transforming the base signal into a shift-type base signal based on a command; An inverter device comprising: PWM base drive means for performing pulse width modulation of a base signal based on the frequency command, and controlling opening and closing of the switching element by the pulse width modulated signal. 2. The inverter device according to claim 1, wherein the base signal output from the waveform generating means has six patterns having a uniform width in one cycle, and the waveform modifying means includes: Outputting a shift-type base signal in which the base signal is modified so as to reduce the width of the final pattern at the time of the start-up operation of the six patterns and to keep the length of one cycle unchanged. Features inverter device. 3. The inverter device according to claim 1, wherein the waveform modifying means modifies the base signal output from the waveform generating means during a start-up operation of the brushless DC motor. An inverter device which outputs a shift-type base signal and outputs the base signal output from the waveform generating means as it is in a normal operation after the start-up operation is completed.