JP4363066B2 - Motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor drive device including an inverter circuit for driving a sensorless DC brushless motor.
[0002]
[Prior art]
A vehicle air conditioner equipped with a conventional electric compressor whose drive source is a sensorless DC brushless motor will be described.
[0003]
In FIG. 17, reference numeral 101 denotes a blower duct, which sucks air from the air inlet 103 by the action of the indoor blower fan 102 and blows out the air heat-exchanged by the indoor heat exchanger 104 from the air outlet 105 into the vehicle interior.
[0004]
The indoor heat exchanger 104 is operated by an electric compressor 106 having a sensorless DC brushless motor as a driving source, a four-way switching valve 107 for switching between a refrigerant flow and selecting cooling or heating, an expansion device 108 and an outdoor fan 109. A refrigeration cycle is configured together with an outdoor heat exchanger 110 that exchanges heat with outside air in the passenger compartment.
[0005]
Reference numeral 111 denotes a motor driving device that operates a sensorless DC brushless motor that is a driving source of the electric compressor 106. Yes.
[0006]
The air conditioner controller 112 is a communication device for communicating with the indoor air blower fan switch 113 for setting ON / OFF / strongness of indoor air blow, the air conditioner switch 114 for selecting cooling / heating / OFF, the temperature control switch 115 and the vehicle controller. 116 is connected.
[0007]
For example, when the air blower fan switch 113 turns on and weakens the air and the air conditioner switch 114 instructs cooling, the air conditioner controller 112 sets the four-way switching valve 107 to the solid line in the figure and evaporates the indoor heat exchanger 104. The outdoor heat exchanger 110 is operated as a condenser, the outdoor blower fan 109 is turned on, and the indoor blower fan 102 is set weak.
[0008]
Further, according to the temperature adjustment switch 115, the temperature of the indoor heat exchanger 104 is adjusted by changing the rotational speed of the electric compressor 106 using the motor driving device 111. When the air conditioner switch 114 turns off the air conditioning, the electric compressor 106 and the outdoor blower fan 109 are turned off.
[0009]
Further, when the indoor blower fan switch 113 is turned off, the indoor blower fan 102 is turned off, and the electric compressor 106 and the outdoor blower fan 109 are also turned off to protect the refrigeration cycle.
[0010]
On the other hand, when an air conditioning OFF command is received from the vehicle controller (not shown) for reasons such as power saving and battery protection via the communication device 116, the air conditioner controller 112 performs the same treatment as the air conditioning OFF by the air conditioner switch 113. do.
[0011]
In a vehicle air conditioner equipped with such an electric compressor, low noise and low vibration are important. In particular, the electric vehicle has no engine, so it is quiet (in a hybrid electric vehicle, the engine is not started and the motor is running), and when the vehicle is stopped, the electric compressor is driven by a battery power source. In this case, since there is no noise vibration due to running, the noise vibration of the electric compressor becomes conspicuous.
[0012]
When the motor driving device 111 is a conventional 120-degree energization method, since the magnetic field change is at intervals of 60 degrees (the energization is at intervals of 60 degrees), there is a torque fluctuation in the sensorless DC brushless motor that is the drive source of the electric compressor 106. This causes noise and vibration. (For example, see Patent Document 1)
FIG. 18 shows a circuit example. In the figure, 121 is a battery, 122 is an inverter operation switching element connected to the battery 121, and 123 is an inverter operation diode. Reference numeral 124 denotes a stator winding of the motor, and 125 denotes a magnet rotor of the motor. Further, 126 is a current sensor for detecting a power supply current, calculating power consumption, protecting a switching element, etc. 127 is a phase shift circuit for detecting the position of the magnet rotor 5 from the voltage of the stator winding. And 128 is a comparison circuit. A control circuit 129 controls the switching elements based on signals from the current sensor 126, the comparison circuit 128, and the like.
[0013]
On the other hand, in the case of sinusoidal drive, torque fluctuation is reduced because the permanent magnet rotor is driven by a continuous rotating magnetic field. Therefore, it is desirable to use a sine wave drive motor driving device that outputs a sine wave current. However, two current sensors are used for detecting the position of the permanent magnet rotor in order to detect the current of the stator winding (see, for example, Patent Document 2).
[0014]
FIG. 19 shows a circuit example. Compared to FIG. 18, there is no comparison circuit 128 / phase shift circuit 127, and a U-phase current detection current sensor 130 and a W-phase current detection current sensor for detecting the position of the magnet rotor 125 from the current of the stator winding. There are 131. The control circuit 129 calculates the current of the other one phase based on the current value for the two phases from the two current sensors (two current sensors are required, but the U phase, the V phase, and the W phase). The position of the magnet rotor 125 is detected, and the switching element is controlled based on a signal from the current sensor 126 or the like. Reference numeral 117 denotes a sine wave drive motor drive device that replaces the 120-degree energization motor drive device 111.
[0015]
In addition to the above-mentioned low noise and low vibration, the motor drive device is required to be small and light in terms of securing mountability and running performance.
[0016]
[Patent Document 1]
JP-A-8-163891 (page 8, FIG. 4)
[Patent Document 2]
Japanese Unexamined Patent Publication No. 2000-333465 (page 9, FIG. 2)
[0017]
[Problems to be solved by the invention]
As described above, the use of a sine wave drive motor driving device that outputs a sine wave current has an advantage that torque fluctuation is reduced. However, in the conventional configuration shown in FIG. 19, the position of the magnet rotor is detected. For this reason, two current sensors are required, and there is a problem that the motor driving device becomes an obstructive factor in reducing the size and weight.
[0018]
The present invention solves such a conventional problem, and an object of the present invention is to provide a motor drive device that is low in noise and low in vibration and that is small and light.
[0019]
[Means for Solving the Problems]
In order to solve the above problems, the present invention detects the position of a magnet rotor by using a current sensor for detecting a power supply current also for current detection of a stator winding. In this current detection, the same energization time is added to the energization period in the carrier period of each phase including the phase not modulated in the two-phase modulation, and the addition is performed in either the first half or the second half or the first half and the second half in the carrier period. Is selected for each phase.
[0020]
With the above configuration, even if two phase current detection current sensors are not added, position detection does not become inaccurate, and the current waveform is not distorted. In addition, the conventional phase shift circuit / comparison circuit in 120-degree energization is not required, and the number of components is reduced, so that a motor drive device that is low in noise, low in vibration, small, light, and highly reliable can be obtained.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0022]
(Embodiment 1)
FIG. 1 shows an electric circuit diagram of the present embodiment. In the figure, 1 is a battery, 2 is a switching element for inverter operation connected to the battery 1, and 3 is a diode for inverter operation. Reference numeral 4 denotes a stator winding of the motor, and 5 denotes a magnet rotor of the motor. Further, reference numeral 7 denotes a control circuit that controls the switching element based on a signal from the current sensor 6. Reference numeral 20 denotes a motor drive device according to the present invention which replaces the conventional motor drive device 111.
[0023]
Compared with the electrical circuit diagram of FIG. 1 and the electrical circuit diagram for 120-degree energization driving of FIG. 18, the comparison circuit 128 and the phase shift circuit 127 are deleted.
[0024]
Further, comparing the electric circuit diagram of FIG. 1 with the electric circuit diagram for sine wave driving provided with the phase current detection current sensor of FIG. 19, the U-phase current detection current sensor 130 and the W-phase current detection current sensor 131. Has been deleted.
[0025]
The detected current value of the current sensor 6 is sent to the control circuit 7, used for power consumption calculation, determination for protection of the switching element 2, etc., and further used for position detection of the magnet rotor 5.
[0026]
Therefore, the control circuit 7 can reduce the signal input circuits (hardware) for the comparison circuit 128 of FIG. 18, the U-phase current detection current sensor 130, and the W-phase current detection current sensor 131 of FIG. Just do it.
[0027]
Then, the switching element 2 is controlled based on a rotational speed command signal (not shown) or the like. The current sensor 6 may be any sensor that can detect the peak of the switching current due to the switching element 2, such as a sensor using a Hall element, a shunt resistor, or the like.
[0028]
Conventionally, since the current sensor 6 can detect the peak of the switching current in order to protect the switching element 2 and the like, it can be used as it is.
[0029]
In FIG. 1, the current sensor 6 is inserted on the negative side of the power supply line. However, since the current is the same, it may be on the positive side. By adopting such a configuration, the number of components is reduced as compared with the conventional one, so that miniaturization can be achieved and reliability such as vibration resistance can be improved (the current sensor or the like is mounted on a printed circuit board). Therefore, it becomes a concern for vibration resistance).
[0030]
Next, a method for detecting the position of the magnet rotor 5 will be described with reference to FIG.
[0031]
In the figure, the relationship between the phase current and the induced voltage in the U phase is shown. Since the induced voltage is a voltage induced in the stator winding 4 by the rotation of the magnet rotor 5 shown in FIG. 1, it can be used for detecting the position of the magnet rotor 5.
[0032]
In the stator winding 4 shown in FIG. The sum of the induced voltage, the voltage of the inductance L, and the voltage of the resistor R is equal to the applied voltage from the motor driving device 20. Assuming that the induced voltage is EU, the phase current is iU, and the applied voltage is VU, VU = EU + R · iU + Ld · iU / dt (FIG. 3 shows an example of the voltage / current of a sensorless DC brushless motor) The induced voltage EU is expressed by EU = VU-R.iU-Ld.iU / dt.
[0033]
Since the control circuit 7 in FIG. 1 controls the switching element 2, the applied voltage VU is known. Therefore, if the values of the inductance L and the resistance R are input to the program software of the control circuit 7, the induced voltage EU can be calculated by detecting the phase current iU.
[0034]
Next, a method for detecting the position of the magnet rotor 5 with the current sensor 6 will be described.
[0035]
First, the waveform of two-phase modulation is shown. FIG. 4 shows two-phase modulation with a maximum modulation of 100%, and FIG. 5 shows two-phase modulation with a maximum modulation of 50%.
[0036]
41 represents a U-phase terminal voltage, 42 represents a V-phase terminal voltage, 43 represents a W-phase terminal voltage, and 29 represents a neutral point voltage.
[0037]
Next, an example will be described with reference to the drawings. FIG. 6 shows an example of energization of the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z within one carrier (carrier cycle). In this case, in the two-phase modulation with the maximum modulation of 50% in FIG. There are three energization patterns (a), (b), and (c).
[0038]
In the energization pattern (a), the upper arm switching elements U, V, W are all OFF, and the lower arm switching elements X, Y, Z are all ON. FIG. 7 shows the current flow at this time.
[0039]
U-phase current and V-phase current flow from the diodes in parallel with the lower arm switching elements X and Y to the stator winding 4, respectively, and W-phase current flows from the stator winding 4 to the lower arm switching element Z. Therefore, no current flows through the current sensor 6 and is not detected.
[0040]
In the energization pattern (b), the upper arm switching element U is ON, and the lower arm switching elements Y and Z are ON. FIG. 8 shows the current flow at this time.
[0041]
The U-phase current flows from the upper arm switching element U to the stator winding 4, the V-phase current flows from the diode parallel to the lower arm switching element Y to the stator winding 4, and the W-phase current flows to the stator winding 4. To the lower arm switching element Z. Therefore, a U-phase current flows through the current sensor 6 and is detected.
[0042]
In the energization pattern (c), the upper arm switching elements U and V are ON, and the lower arm switching element Z is ON. FIG. 9 shows the current flow at this time.
[0043]
The U-phase current and the V-phase current flow from the upper arm switching elements U and V to the stator winding 4, respectively, and the W-phase current flows from the stator winding 4 to the lower arm switching element Z. Therefore, a W-phase current flows through the current sensor 6 and is detected.
[0044]
As described above, since the U-phase current and the W-phase current are detected, the remaining V-phase current can be obtained by applying Kirchhoff's current law at the neutral point of the stator winding 4.
[0045]
In this case, the U-phase current is a current that flows into the neutral point of the stator winding 4, and the W-phase current is a current that flows out of the neutral point of the stator winding 4. It is obtained by taking the difference in current.
[0046]
Since the above current detection can be performed for each carrier, the position can be detected for each carrier and the output to the stator winding 4 can be adjusted. Therefore, torque fluctuation is small compared to 120 degree energization, and low noise and low vibration can be realized. In addition, startability is improved.
[0047]
It can be seen that the phase current that can be detected by the current sensor 6 is determined in the ON and OFF states of the upper arm switching elements U, V, and W. When only one phase is ON, the current of the phase can be detected. When the two phases are ON, the current of the remaining phases can be detected. When the three phases are OFF, the current cannot be detected. Therefore, the detectable phase current can be known by confirming that the upper arm switching elements U, V, and W in one carrier are ON. In FIG. 6, the ON state of each phase of the upper arm may be confirmed.
[0048]
In FIG. 10, the current that can be detected using this fact can be examined. The upper arm switching elements U, V, and W are turned on within one carrier (carrier cycle) at 90 degrees, 105 degrees, 120 degrees, 135 degrees, and 150 degrees in the two-phase modulation of 100% maximum modulation in FIG. The (energized) state is displayed evenly from the center.
[0049]
The U-phase energization period is represented by a thin solid line, and the V-phase energization period is represented by a solid solid line. Furthermore, U and W indicated by arrows below each energization period indicate a U-phase current detectable period and a W-phase current detectable period, respectively.
[0050]
At 90 degrees, the U-phase modulation is 87% from FIG. 4, so that 1 carrier (carrier cycle) is 100%, and U-phase (thin solid line) modulation (energization time) 87% is evenly distributed from the center. Displayed (V-phase modulation (not shown because it is 0%). The same applies to other phases.
[0051]
The reason why the angle is set to 90 degrees to 150 degrees is that this energization time pattern is repeated although the energized phases are different.
[0052]
Similarly, FIG. 11 shows a case where the maximum modulation is 50%.
[0053]
Here, at the phase of 90 degrees in FIGS. 10 and 11, the V phase is not energized, and at the phase of 150 degrees, the energization times of the two phases are the same, so only the current for one phase is present. The situation is undetectable. In this case, measures such as reusing the previously detected value, estimating, or intentionally changing the energization time are necessary, but problems such as inaccurate position detection and distortion of the current waveform occur. (Low noise, low vibration, start-up effect is reduced) At the phase of 90 degrees, if an energization time capable of detecting current is added to the V phase, the W phase current can be detected during the energization time, but the current waveform will be distorted. It is necessary to reduce the added energization time from the V phase. However, since the energization time of the V phase is close to 0, it cannot be reduced. Therefore, the current waveform is distorted.
[0054]
This handling method is shown below.
[0055]
Even if the same energizing time is added to each phase, the phase voltage does not change. As an example, when 20% is added to each phase in FIG. 5, the neutral point voltage (the sum of the terminal voltages of each phase divided by 3) increases by 20%. Since the phase voltage is a value obtained by subtracting the neutral point voltage from the terminal voltage, 20% is canceled out and is not different from the phase voltage before addition.
[0056]
Therefore, the following can be dealt with.
[0057]
An example is shown in FIG. This is referred to as adjustment 1. The minimum time required for the current sensor 6 to detect a current is represented by δ.
[0058]
FIG. 12A shows a case where the phase is 90 degrees at the maximum modulation of 100%. As described above, the V phase is not energized.
[0059]
In FIG. 12B, 2δ is equally added to the first half and the second half of the energization period in the U-phase energization time. Similarly, 2δ is added to the V phase at the energization time 0. Furthermore, 2δ is similarly added to the unmodulated W phase. The energization period of the W phase is represented by a thick solid line.
[0060]
As a result, during the energization time 2δ at the center of the carrier cycle, the upper arm is turned on for all three phases. This state is shown in the energization pattern (d) in FIG. In the energization pattern (d), the upper arm switching elements U, V, W are all ON, and the lower arm switching elements X, Y, Z are all OFF. FIG. 14 shows the current flow at this time. U-phase current and V-phase current flow from the upper arm switching elements U and V to the stator winding 4, respectively, and W-phase current flows from the stator winding 4 from the upper arm switching element W. Therefore, no current flows through the current sensor 6 and is not detected. Therefore, in addition to the case when the three phases are OFF, the detection is impossible even when the three phases are ON, and during the energization time 2δ in the center of the carrier cycle, power is not supplied from the power source to the stator winding 4. Adding 2δ does not change the modulation.
[0061]
In FIG. 12C, the W-phase energization period is shifted by δ toward the first half of the carrier cycle (the W-phase energization period is only the first half).
As a result, the minimum current detection required time δ can be secured, so that the V-phase and W-phase currents can be detected.
[0062]
Here, the current change of each phase by energization is confirmed. In the period in which the V-phase current can be detected, since the upper arms of the U-phase and the W-phase are ON, if the current change of the U-phase is 1, the W-phase is also 1. In the V phase, the lower arm is ON and the current change is reversed, and the currents in the U phase and the W phase flow. Similarly, in the period in which the W-phase current can be detected, since the upper arms of the U-phase and the V-phase are ON, the U-phase is 1 and the V-phase is 1. The W phase is -2 because the lower arm is ON. When all three phases are ON, the current does not change. Therefore, the current change in each phase during the energization time 3δ at the center of the carrier cycle is 2 for the U phase, −1 for the V phase, and −1 for the W phase. On the other hand, in the same period of FIG. 12B, there is a current change only in the period corresponding to the period in which the V-phase current of FIG. Since the upper arm is ON only for the U phase, the U phase is 2, the V phase is -1, and the W phase is -1. Therefore, the energization in FIG. 12C is equivalent to the energization in FIG.
[0063]
Therefore, even when only one phase can be detected, it is possible to detect the currents of the V phase and the W phase in addition to the U phase. Thus, the position of the permanent magnet rotor can be determined. Further, since the same energization time is applied to all three phases, there is no change in modulation, and the current waveform is not distorted. Therefore, in the above description, in which the motor drive device having low noise, low vibration, high startability, small size, light weight and high reliability is obtained, it is specified at the phase 90 degrees where the energization time is 0, but the energization time is close to 0 The same applies to around 0 degree. The same applies to the case where the phase is 90 degrees at another maximum modulation of 50% or the like. Further, the present invention can also be applied to the case where the energization times of the two phases at the phase around 150 degrees coincide (adjacent). The addition of the energization time 2δ to the U phase may be performed in the first half of the energization period that is the same as that of the W phase as long as it falls within the carrier cycle. δ may be equal to or longer than the minimum time required for current detection. It is not necessary to add the energization time at a location (phase) where the phase current can be detected.
[0064]
(Embodiment 2)
FIG. 15 shows a method for dealing with the case where the energization times coincide. This is referred to as Adjustment 2.
[0065]
FIG. 15A shows a case where the phase is 150 degrees at the maximum modulation of 100%.
[0066]
In FIG. 15B, δ is equally added to the first half and the second half of the energization period in the energization time of the U phase and the V phase. Similarly, δ is added to the unmodulated W phase. As a result, during the energization time δ at the center of the carrier cycle, the upper arm is turned on for all three phases.
[0067]
As described above, power is not supplied from the power source to the stator winding 4 during the energization time δ at the center of the carrier cycle, so that modulation does not change even if δ is added to the U-phase and V-phase energization times.
[0068]
In FIG. 15C, the U phase is shifted to the first half and the V phase is shifted to the second half so as to ensure the minimum current detection required time δ in the first half and the second half of the energization period. As a result, the minimum current detection required time δ can be secured, so that the V-phase and V-phase currents can be detected.
[0069]
Here, as described above, the current change in each phase due to energization is confirmed. In the period in which the U-phase current can be detected, the upper arm is ON only for the U-phase, so the U-phase is 2, the V-phase is -1, and the W-phase is -1. In the period in which the V-phase current can be detected, the upper arm is ON only for the V-phase, so the V-phase is 2, the U-phase is -1, and the W-phase is -1. Therefore, when the total is obtained, the U phase is 1, the V phase is 1, and the W phase is -2. In the energization period (energization time δ) between the U phase and the V phase in FIG. 15B, the upper arms of the U phase and the V phase are ON, so the U phase is 1, the V phase is 1, and the W phase is − 2. Therefore, the sum of the U-phase current detectable period (energization time δ) and the V-phase current detectable period (energization time δ) is equal to the U-phase and V-phase energization period (energization period) in FIG. Therefore, the energization in FIG. 15C is equivalent to the energization in FIG. 15B.
[0070]
Therefore, even when only one phase can be detected, U-phase and V-phase currents can be detected in addition to the W-phase. Thus, the position of the permanent magnet rotor can be determined. Further, since the same energization time is applied to all three phases, there is no change in modulation, and the current waveform is not distorted. Thus, in the above description, the motor drive device having low noise, low vibration, high startability, small size, light weight, and high reliability is obtained. The same applies before and after. The same applies to the case of a phase of 150 degrees at other maximum modulation of 50% or the like. Further, the present invention can be applied to a case where the energization time of one phase around 90 degrees is 0 (small). δ may be equal to or longer than the minimum time required for current detection. In the adjustment 2, the amount of energization to be added may be smaller than that in the adjustment 1. It is not necessary to add the energization time at a location (phase) where the phase current can be detected.
[0071]
(Embodiment 3)
FIG. 16 shows a view in which the motor driving device 20 is attached in close contact with the left side of the electric compressor 40. A compression mechanism 28, a motor 31 and the like are installed in a metal casing 32. The refrigerant is sucked from the suction port 33 and is compressed by driving the compression mechanism unit 28 (scroll in this example) by the motor 31.
[0072]
The compressed refrigerant passes through the motor 31 (cools) and is discharged from the discharge port 34. A terminal 39 internally connected to the winding of the motor 31 is connected to the motor driving device 20.
[0073]
The motor driving device 20 uses a case 30 so that it can be attached to the electric compressor 40. The inverter circuit unit 37 serving as a heat source dissipates heat to the metal casing 32 of the electric compressor 40 via the case 30 (the refrigerant inside the electric compressor 40 via the metal casing 32). Cooled by).
[0074]
The terminal 39 is connected to the output part of the inverter circuit part 37. The connection line 36 includes a power supply line to the battery 1 and a control signal line to the air conditioner controller. By adopting concentrated winding for the winding of the motor 31, the length in the lateral direction can be shortened compared to distributed winding. Since concentrated windings have a large inductance, the time required for recirculation to the diode becomes long with 120-degree energization, making position detection difficult and control difficult. However, with sinusoidal drive, control is possible because the position is detected by current.
[0075]
In such an electric compressor integrated with a motor drive device, the motor drive device 20 needs to be small and resistant to vibration. It is suitable as an embodiment of the present invention.
[0076]
【The invention's effect】
As is apparent from the above, the present invention uses a current sensor for detecting the power supply current to detect the current of the stator windings to detect the position of the magnet rotor. Sine-wave drive is possible without adding a phase current detection current sensor, and the conventional phase shift circuit and comparison circuit for 120-degree conduction are not required, reducing the number of components, resulting in low noise and vibration. There is an effect that a motor driving device having high startability, small size and light weight and high reliability can be obtained.
[0077]
Further, the present invention adds the same energization time to the energization period in the carrier period of each phase including the phase not modulated in the two-phase modulation in the current detection, and the addition is performed in the first half, the second half, or the first half in the carrier period. In the latter half, one of the distributions is selected for each phase, and the current flowing through the stator winding is detected by a current sensor. According to this configuration, the value detected last time is used again, and estimated. It is unnecessary to take measures such as intentionally changing the energization time, and there is an effect that the position detection is not inaccurate and the problem that the current waveform is distorted does not occur.
[0078]
In addition, the present invention is compact and strong against vibration resistance, and concentrated windings can be used for the motor windings. This has the effect of reducing the lateral length of the electric compressor integrated with the motor drive device.
[Brief description of the drawings]
FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention. FIG. 2 is an explanatory diagram of an induced voltage detection method in sinusoidal driving. FIG. 3 is a waveform diagram showing voltage and current of a sensorless DC brushless motor. FIG. 5 is a waveform diagram showing the modulation of each phase at the maximum modulation of 100% of the two-phase modulation. FIG. 5 is a waveform diagram showing the modulation of each phase at the maximum modulation of 50% of the two-phase modulation. Energization timing chart showing a phase current detection method according to FIG. 7 is an electric circuit diagram showing a current path at the same energization timing (a). FIG. 8 is an electric circuit diagram showing a current path at the energization timing (b). FIG. 10 is an electric circuit diagram showing a current path at the same energization timing (c). FIG. 10 is an explanatory diagram showing energization of the upper arm at every phase of 100% maximum modulation of two-phase modulation. % Phase FIG. 12 is an explanatory diagram showing phase current detection of two-phase modulation according to the first embodiment of the present invention. FIG. 13 is a timing diagram (d) showing an in-phase current detection method. Added energization timing chart FIG. 14 is an electric circuit diagram showing a current path at the same energization timing (d). FIG. 15 is an explanatory diagram showing phase current detection of two-phase modulation according to the second embodiment of the present invention. 16 is a sectional view of a motor drive unit-integrated electric compressor showing a third embodiment of the present invention. FIG. 17 is a block diagram of a conventional vehicle air conditioner equipped with an electric compressor. Electrical circuit diagram for energization drive [FIG. 19] Electrical circuit diagram for sine wave drive with current sensor for detecting common-mode current [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery 2 Switching element 3 Diode 4 Stator winding 5 Magnet rotor 6 Current sensor 7 Control circuit 20 Motor drive device 30 Integrated case 31 of motor drive device Motor part 40 Electric compressor

Claims (5)

An inverter circuit that outputs a sine-wave AC current to a sensorless DC brushless motor by switching a DC voltage of the DC power supply; and a current sensor that detects a current between the DC power supply and the inverter circuit. The same energizing time is added to the energizing period in the carrier cycle of each phase including phase that is modulated and not modulated, and the addition is performed in either the first half or the second half or the first half and the second half in the carrier cycle. A motor drive device that is selected for each phase, detects the current flowing through the stator winding by the current sensor, determines the position of the permanent magnet rotor, and controls switching of the inverter circuit. 2. The motor driving apparatus according to claim 1, wherein only one phase is added to the first half or second half of the carrier period. The motor driving device according to claim 1, wherein one phase is added to the first half and another phase is added to the second half in the carrier period. The motor drive apparatus in any one of Claims 1-3 mounted in the electric compressor provided with the sensorless DC brushless motor. The motor drive device according to claim 1, which is mounted on a vehicle air conditioner.

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