KR20040096766A - Motor Driving Device and Air Conditioning Device - Google Patents

Abstract

PURPOSE: A motor driving device and an air conditioning device are provided to reduce noises and leakage current caused by an inverter circuit. CONSTITUTION: A motor driving device comprises a maintaining unit for maintaining switching elements(60u,60v,60w,60x,60y,60z) at on state during electrified period of stator winding of each phase; and a voltage regulating unit for detecting rotational frequency of a rotor, and regulating DC voltages applied to an inverter circuit so as to permit the detected rotational frequency of the rotor to become a target rotational frequency. The voltage regulating unit has a step-down converter circuit(59) having step-down switching elements(59a,59b), and regulates DC voltages by on/off controlling the step-down switching elements.

Description

Motor Driving Device and Air Conditioning Device

The present invention relates to a motor drive device, a compressor drive device and an air conditioner having an inverter circuit.

Generally, a rectification circuit for converting AC power into DC power and an inverter circuit having a plurality of switching elements and connected to the stator windings of each phase of the brushless DC motor, and energizing the stator windings of each phase A motor drive device that controls a phase voltage applied to the stator windings of each phase in the inside and controls the rotation speed of the rotor to the target rotation speed is known (see Patent Document 1, for example).

In this type of motor drive device, the phase voltage for controlling the corresponding switching element of the inverter circuit with a pulse width modulated drive signal and applying it to the stator windings during the energization period of each stator winding is pulsed.

Moreover, generally the air conditioner provided with the outdoor unit which has a compressor and an outdoor heat exchanger, and the indoor unit which has an indoor heat exchanger is known. Compressors of this kind have a brushless DC motor driven by the motor drive device.

[Patent Document 1]

Japanese Patent Laid-Open No. 2001-37278

However, in the motor drive device, since the switching element of the inverter circuit is controlled by a pulse width modulated drive signal during the energization period, there is a problem that the noise level generated by the inverter circuit is large.

In order to prevent this noise from penetrating into other equipment connected to this power supply via a power supply, there are measures to connect two capacitors in series between the input terminals of the rectifier circuit and ground the two capacitors. If the noise level generated by the signal is large, there is a problem that the leakage current leaking to the ground through this capacitor becomes large.

In addition, the compressor is generally grounded in the compressor container for safety measures. Normally, noise from the inverter circuit flows from the stator windings through the refrigerant or oil in the compressor vessel to the compressor vessel and leaks to the ground as a leakage current. And as the noise level increases, the leakage current also increases. In particular, this leakage current becomes remarkable when the low impedance of the stator winding is achieved. Moreover, when the switching frequency of the switching element of an inverter circuit increases, high frequency noise will increase and leakage current will increase.

Accordingly, an object of the present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a motor drive device, a compressor drive device, and an air conditioner that can reduce noise generation and leakage current caused by an inverter circuit.

1 is a refrigerant circuit diagram showing an air conditioner according to one embodiment of the present invention;

2 is an electric circuit diagram showing a compressor drive device applied to an air conditioner.

FIG. 3 is a block diagram showing a major part of the configuration in the compressor drive device of FIG.

4 is a time chart diagram showing the drive signal to the inverter circuit and the phase voltage of the stator windings.

<Explanation of symbols for the main parts of the drawings>

10: air conditioner

11: outdoor unit

12: indoor unit

16: compressor

16A: Brushless DC Motor

19: outdoor heat exchanger

21: indoor heat exchanger

26: stator

26u, 26v, 26w: stator winding

27: rotor

30: compressor driving device

31: motor drive unit

41a: Step-up converter circuit control unit (voltage adjusting unit)

41b: inverter circuit controller (holding support)

41c: Rotor position detector

41d: RPM detection unit (voltage adjuster)

41e: comparator (voltage adjuster)

41f: target rotation speed generation unit (voltage adjustment unit)

59: step-up converter circuit (voltage adjustment section)

59a: step-down switching element

59b: boosting switching element

60: inverter circuit

60u, 60v, 60w, 60x, 60y, 60z: switching element

In order to solve the said subject, the invention of Claim 1 has an inverter circuit which has a some switching element, and is connected to the stator winding of each phase of a brushless DC motor, and it is within the electricity supply period which energizes the stator winding of each phase. A motor driving apparatus for controlling a phase voltage applied to a stator curve of each phase to control the rotational speed of the rotor to a target rotational speed, wherein the corresponding switching element is kept on during the energization period of the stator winding of each phase. And a voltage adjusting portion for adjusting a DC voltage applied to the inverter circuit so as to detect the rotational speed of the rotor and to make the rotational speed of the rotor the target rotational speed.

The invention according to claim 2 is the motor drive device according to claim 1, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on / off of the step-down switching element to You may adjust a DC voltage.

The invention according to claim 3 is the motor drive device according to claim 1, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element and a step-up switching element, and the step-down switching element and the step-up switching element. The DC voltage may be adjusted by controlling the on / off of.

The invention according to claim 4 includes a compressor having a brushless DC motor, an inverter circuit having a plurality of switching elements and connected to a stator winding of each phase of the brushless DC motor, and energizing the stator winding of each phase. A compressor drive device that controls a phase voltage applied to a stator winding of each phase within an energization period, and controls a rotational speed of a rotor to a target rotational speed, wherein the corresponding switching element is applied during the energization period of the stator winding of each phase. And a holding portion for holding the ON state and a voltage adjusting portion for detecting a rotational speed of the rotor and adjusting a DC voltage applied to the inverter circuit to set the rotational speed of the rotor to a target rotational speed. It is characterized by.

The invention according to claim 5 is the compressor drive device according to claim 4, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on-off of the step-down switching element to adjust the DC voltage. You may also

According to a sixth aspect of the present invention, in the compressor driving apparatus according to the fourth aspect, the voltage adjusting section includes a step-down converter circuit having a step-down switching element and a step-up switching element, and the step-down switching element and the step-up switching element. The on-off voltage may be controlled to adjust the DC voltage.

The invention according to claim 7 includes an outdoor unit having a compressor and an outdoor heat exchanger, and an indoor unit having an indoor heat exchanger, wherein the compressor includes a brushless DC motor, and a plurality of switching elements are provided in the stator windings of each phase of the brushless DC motor. In an air conditioner for connecting an inverter circuit having a control circuit, controlling a phase voltage applied to the stator windings of each phase during the energization period of energizing the stator windings of each phase, and controlling the rotational speed of the rotor to a target rotational speed. A holding part for holding the corresponding switching element in an on state during the energization period of the stator winding of each phase, and for detecting the rotational speed of the rotor and for setting the rotational speed of the rotor to a target rotational speed, And a voltage adjusting unit for adjusting the DC voltage applied to the inverter circuit.

The invention according to claim 8 is the air conditioner according to claim 7, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on-off of the step-down switching element to adjust the DC voltage. You may also

The invention according to claim 9 is the air conditioner according to claim 7, wherein the voltage adjusting section includes a step-down converter circuit having a step-down switching element and a step-up switching element, and the step-down switching element and the step-up switching element. The on-off voltage may be controlled to adjust the DC voltage.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

1 is a refrigerant circuit diagram showing an air conditioner according to an embodiment of the present invention.

As shown in FIG. 1, the air conditioner 10 includes an outdoor unit 11 and an indoor unit 12, and an outdoor refrigerant pipe 14 of the outdoor unit 11 and an indoor refrigerant pipe 15 of the indoor unit 12. It is connected via these connection pipes 24 and 25. FIG.

The outdoor unit 11 is arranged outdoors. The compressor 16 is disposed in the outdoor refrigerant pipe 14, the accumulator 17 is disposed on the suction side of the compressor 16, and the four-way valve 18 is disposed on the discharge side of the compressor 16. The outdoor heat exchanger 19 and the electric expansion valve 22 are arranged one by one on the four-way valve 18 side. The compressor 16 is driven by a brushless DC motor 16A. The outdoor heat exchanger 19 is disposed adjacent to an outdoor fan 20 that blows the air from the outdoor heat exchanger 19 to the outside. This outdoor fan 20 is driven by this outdoor fan motor 20A.

The indoor unit 12 is installed indoors, and the indoor heat exchanger 21 is disposed in the indoor refrigerant pipe 15. In this indoor heat exchanger 21, an indoor fan 23 which blows air from the indoor heat exchanger 21 to the room is arranged adjacently. This indoor fan 23 is driven by an indoor fan motor 23A.

The air conditioner 10 includes an outdoor control device 41 installed in the outdoor unit 11 and an indoor control device 42 provided in the indoor unit 12.

The outdoor control device 41 controls the operating frequency (speed) of the compressor 16, gradually controls the speed of the outdoor fan 20, controls the opening degree of the electric expansion valve 22, and operates. Control to switch the four-way valve 18 in accordance with the mode is performed. In addition, the indoor control device 42 controls the rotation speed of the indoor fan 23.

The remote controller (not shown) on the indoor unit 12 side can be set to either of the cooling operation or the heating operation.

The outdoor control device 41 and the indoor control device 42 are connected by a communication line. The outdoor control device 41 then transmits an instruction of the rotation speed of the indoor fan motor 23A to the indoor control device 42 via this communication line. In addition, the indoor control device 42 transmits control information, such as information of an indoor air conditioning load, information of a set driving mode, and information indicating the rotation speed of the indoor fan motor 23A, to the outdoor control device 41. . The outdoor control device 41 controls the brushless DC motor 16A, the outdoor fan motor 20A, the four-way valve 18 and the electric expansion valve 22 based on the received control information.

When the operation mode is set to the cooling operation, the four-way valve 18 is switched to the cooling side so that the coolant flows like a solid arrow. The refrigerant discharged from the compressor 16 by the operation of the compressor 16 reaches the outdoor heat exchanger 19 via the four-way valve 18, and condenses in the outdoor heat exchanger 19 to condense the electric expansion valve. After depressurizing via 22, it evaporates in the indoor heat exchanger 21 of the indoor unit 12, and cools the room. The refrigerant from the indoor heat exchanger 21 flows to the outdoor unit 11 side and is returned to the compressor 16 via the four-way valve 18 and the accumulator 17 of the outdoor unit 11.

In addition, when the operation mode is set to the heating operation, the four-way valve 18 is switched to the heating side, and the coolant flows like a broken arrow. The refrigerant discharged from the compressor 16 by the operation of the compressor 16 reaches the indoor heat exchanger 21 of the indoor unit 12 via the four-way valve 18, and in this indoor heat exchanger 21. It condenses and heats the room. The refrigerant condensed in the indoor heat exchanger (21) is depressurized by the electric expansion valve (22) of the outdoor unit (11), and after evaporating in the outdoor heat exchanger (19), the four-way valve (18) and the accumulator (17). The compressor 16 is returned to the compressor 16 via.

Fig. 2 is an electric circuit diagram showing a compressor drive device applied to the air conditioner in the present embodiment.

The compressor drive device 30 includes a compressor 16 and a motor drive device 31 that drives the brushless DC motor 16A of the compressor 16. The brushless DC motor 16A of the compressor 16 is a three-phase motor having a stator 26 having stator windings 26u, 26v, 26w, and a rotor 27 having a permanent magnet. This brushless DC motor 16A is driven by the motor drive device 31. The brushless DC motor 16A of the compressor 16 is controlled for rotation speed in accordance with the air regulating load. Here, the compressor 16 is grounded with a metallic compressor container, and safety measures such as a short circuit are implemented.

The motor drive device 31 includes power supply terminals 51a and 51b to which an AC power supply 33 is connected, a noise filter circuit 52, a rectifier circuit 53, a step-up and converter unit 54, and a smoothing capacitor. And an output terminal 57u, 57v, 57w to which the inverter unit 56, the brushless DC motor 16A of the compressor 16 are connected, and the control device of the motor drive device 31. The outdoor control device 41 is provided.

The noise filter circuit 52 includes the interline capacitors 52a and 52b and the common mode coil 52c to attenuate the common mode noise, and the line earth capacitors 52d and 52e to attenuate the normal mode noise.

The interline line capacitor 52d and the interline line capacitor 52e are connected in series. The connection point between the line earth capacitor 52d and the line earth capacitor 52e is grounded.

The rectifier circuit 53 converts DC power into AC power. In this rectifier circuit 53, a diode is bridged, and full-wave rectification is performed.

The step-down converter unit 54 includes a step-down converter circuit 59 and a step-down converter circuit control unit 41a (FIG. 3) in the outdoor control device 41. The step-down converter circuit 59 is provided between the rectifier circuit 53 and the smoothing capacitor 55 as shown in FIG. The step-up converter section 54 steps up and down the DC voltage at the output terminal of the rectifier circuit 53.

The step-down converter circuit 59 includes a step-down switching element (eg, IGBT) 59a, a step-up switching element (eg, IGBT) 59b, a first backflow prevention diode 59c, The reactor 59d and the second backflow prevention diode 59e are provided.

Specifically, when the connection relationship between the elements of the step-down converter circuit 59 is explained, one end (collector terminal) of the step-down switching element 59a is connected to one end of the output end of the rectifier circuit 53. The other end (emitter terminal) of the step-down switching element 59a is connected to one end (cathode terminal) of the first backflow prevention diode 59c and one end of the reactor 59d. The other end of the reactor 59d is connected to one end (collector terminal) of the boosting switching element 59b and one end (anode terminal) of the second backflow prevention diode 59e. The other end (cathode terminal) of the second backflow prevention diode 59e is connected to one end of the smoothing capacitor 55. The other end (anode terminal) of the first backflow prevention diode 59c, the other end (emitter terminal) of the boosting switching element 59b includes the other end of the output end of the rectifier circuit 53, and the smoothing capacitor 55 It is connected to the other end of.

In this step-down converter circuit 59, the step-down switching element 59a, the first backflow prevention diode 59c, and the reaction device 59d function as a step-down converter circuit, and the step-up switching element 59b, reaction The device 59d and the second backflow prevention diode 59e function as a boost converter circuit.

The inverter part 56 is equipped with the inverter circuit 60 and the inverter circuit control part 41b (FIG. 3) of the outdoor control apparatus 41. As shown in FIG. The DC voltage stepped up and down by the step-up converter section 54 is applied to the input end of the inverter circuit 60.

Inverter circuit 60 is provided with a plurality (six) switching elements (for example, IGBT) 60u, 60v, 60w, 60x, 60y, 60z connected three-phase bridged as shown in FIG. have. The stator windings of the brushless DC motor 16A, in which the switching elements 60u and 60x, the switching elements 60v and 60y, and the switching elements 60w and 60z are paired, respectively, and each connection point is molded and connected. It is connected to (26u, 26v, 26w), respectively.

Then, three phase voltages Vu, Vv and Vw are applied to the stator windings 26u, 26v and 26w of the brushless DC motor 16A. Here, Vu represents the U phase voltage, Vv represents the V phase voltage, and Vw represents the W phase voltage.

In the present embodiment, the inverter unit 56 of the motor drive device 30 drives the brushless DC motor 16A in a 120 degree energized rectangular wave drive system. Therefore, in the phase voltages Vu, Vv, and Vw applied to the stator windings 26u, 26v, and 26w of the brushless DC motor 16A, an energization period of 120 ° electric angle and a non-energization period of 60 ° electric angle are provided. have. In this non-energization period, an induced voltage is generated by the rotation of the rotor 27.

One end of the voltage detection lines 43u, 43v, 43w is connected to the output side of the inverter circuit 60.

As shown in Fig. 3, the outdoor control device 41 is connected to the other end of the voltage detection lines 43u, 43v, 43w in addition to the step-up converter circuit control section 41a and the inverter circuit control section 41b. The rotor position detection part 41c, the rotation speed detection part 41d, the comparison part 41e, and the target rotation speed generation part 41f are provided.

The rotor position detector 41c monitors the voltages of the voltage detection lines 43u, 43v, 43w, and based on the induced voltage generated in the non-energizing period of each voltage detection line 43u, 43v, 43w. (27) The position of FIG. 2 is detected.

The rotation speed detection part 41d detects the rotation speed of the rotor 27 based on the detection result of this rotor position detection part 41c.

The target rotational speed generation unit 41f generates the target rotational speed of the rotor 27 based on the air control load (for example, room temperature or the like).

The comparison unit 41c compares the detected rotational speed with the target rotational speed and transmits the comparison result to the boost converter circuit control unit 41a. Specifically, the deviation is calculated by subtracting the detected rotational speed from the target rotational speed, and the deviation is transmitted to the step-up converter circuit controller 41a.

The step-down converter circuit control section 41a is provided with a step-down switching element drive circuit (not shown) for driving the step-down switching element 59a and the step-up switching element 59b.

The step-up converter circuit control section 41a adjusts the DC voltage applied to the input terminal of the inverter circuit 60 in order to set the rotation speed of the rotor 27 as the target rotation speed.

That is, the step-down converter circuit control section 41a controls the step-down converter circuit 59 based on the comparison result of the received comparison section 41c.

Specifically, the step-up converter circuit control unit 41a performs control to increase the DC voltage applied to the inverter circuit 60 when the deviation received from the comparing unit 41c is a positive value. That is, the step-down converter circuit control section 41a performs control to increase the rotational speed of the rotor 270 by raising the DC voltage applied to the inverter circuit 60. The step-down converter circuit control section 41a compares When the deviation received from the unit 41e is a negative value, control is performed to increase the DC voltage to be applied, that is, the step-up converter circuit control unit 41a lowers the DC voltage applied to the inverter circuit 60 to rotate the rotor. Control to lower the rotation speed of (27) is performed.

Here, the step-down converter circuit controller 41a outputs a pulse width modulation signal to the gate terminal of the step-down switching element 59a when stepping down the DC voltage applied to the input terminal of the step-down converter circuit 59. Switching on and off. At this time, the step-up converter circuit control section 41a performs control to turn off the boosting switching element 59b.

In addition, when boosting the DC voltage applied to the input terminal of the boost converter circuit 59, the boost converter circuit controller 41a outputs a pulse width modulation signal to each gate terminal of the boost switching element 59b. Switching on and off. At this time, the step-down converter circuit control section 41a performs control to turn on the step-down switching element 59a.

The voltage adjusting part which adjusts the DC voltage which these step-up converter part 54, the rotation speed detection part 41d, the comparison part 41e, and the target rotation speed generation part 41f apply to the inverter circuit 60. It is functioning as.

As described above, since the DC voltage applied to the inverter circuit 60 is adjusted by the lower step-down converter circuit 59 under the control of the step-down converter circuit controller 41a, the stator winding 26u is controlled by switching control in the inverter circuit as in the prior art. , 26v, 26w), there is no need to adjust the magnitude of the phase voltage.

In addition, since only two elements are provided as the main noise source, the step-down switching element 59a and the step-up switching element 59b, the noise can be reduced.

Next, the operation of the inverter unit 56 based on the inverter circuit control unit 41b will be described.

The inverter circuit control part 41b is provided with the switching element drive circuit which is not shown in figure which drives the switching elements 60u, 60v, 60w, 60x, 60y, 60z.

As shown in the time chart of FIG. 4, the inverter circuit controller 41b has drive signals u1, v1, w1, u2, v2 at each gate terminal of the switching elements 60u, 60v, 60w, 60x, 60y, 60z. , w2) respectively.

The drive signals u1, v1, w1, u2, v2, w2 are high-level signals of 120 ° electric angle (hereinafter referred to as "H level signal") and low-level signals of 240 ° electric angle (hereinafter, "L". Level signal ”is repeated periodically.

Then, the H level signal of the drive signal v1 output to the switching elements 60u, 60v, 60w is output by being delayed by 120 degrees from the H level signal of the drive signal u1, and the H level signal of the drive signal w1 is output. Is delayed by 120 ° from the H level signal of the drive signal u1, and the H level signal is output.

The H level signal of the drive signal v2 output to the switching elements 60x, 60y, 60z is output by being delayed by 120 degrees from the H level signal of the drive signal u2, and the H level signal of the drive signal w2 is output. Is delayed by 120 degrees from the H level signal of the drive signal u2, and the level signal is output.

The H level signal of the drive signal u1 and the H level signal of the drive signal u2 are output at an electric angle of 60 °. Similarly, the H level signal of the drive signal v1 and the H level signal of the drive signal v2 are output at an electrical angle of 60 °. The H level signal of the drive signal w1 and the H level signal of the drive signal w2 are output at an electric angle of 60 degrees.

The operation of the switching elements 60u and 60x will be described below. Here, since the switching elements 60V, 60w, 60y, 60z also operate in the same manner as the switching elements 60u, 60x, the description of the operation of the switching elements 60v, 60w, 60y, 60z is omitted.

When the switching element 60u receives the H level signal x1 of the drive signal u1, the switching element 60u is turned on and the phase voltage Vu becomes the positive voltage y1. When the switching element 60x inputs the H level signal x2 of the drive signal u2, the switching element 60x turns on and the phase voltage Vu becomes the negative voltage y2. In addition, when the drive signals u1 and u2 are L level signals, the switching elements 60u and 60x are off.

The phase voltage Vu is supplied with an electrical current of 120 degrees for a positive voltage, an electrical current of 60 degrees for an electrical angle, an electrical current of 120 degrees for a negative voltage, and a voltage of 60 degrees of an electrical angle. Repeat the whole period. In addition, the phase voltages Vu, Vv, and Vw are shifted from each other by 120 degrees.

In this manner, the inverter unit 56 does not set the magnitude of the phase voltage by the drive signal that has been pulse-modulated in the energizing period as in the prior art, and stator windings 26u, 26v, 26w). That is, the inverter circuit control part 41b of the inverter part 56 controls the inverter circuit 60 so that a corresponding switching element may turn on during the energization period of the stator windings 26u, 26v, 26w.

Thereby, since the operation | movement which turns off the switching element of the inverter circuit 60 is reduced, heat generation by this inverter circuit 60 can be reduced. In addition, since the operation of turning off the switching element of the inverter circuit 60 is reduced, it is possible to reduce the generation of noise by the inverter circuit 60.

During the energization period, switching elements 60u, 60v, 60w for applying a positive voltage to the stator windings 26u, 26v, 26w, and switching elements for applying a negative voltage to the stator windings 26u, 26v, 26w. Since (60x, 60y, 60z) is kept in the on state, heat generation can be effectively reduced and generation of noise can be effectively reduced.

In addition, since the occurrence of noise of the inverter circuit 60 is suppressed, the leakage current leaking to the ground via the compressor 16 and the leakage current leaking to the ground via the line earth capacitors 52d and 52e are reduced. Therefore, the low impedance of the stator windings 26u, 26v, 26w can be achieved.

In addition, since the inverter circuit 60 does not switch during the energization period, high frequency noise can be suppressed and leakage current can be reduced more effectively.

In addition, although the low voltage is applied to the stator windings 26u, 26v, 26w at the start of the compressor 16, a pulsed high voltage is not applied to the stator winding as in the prior art. Therefore, excessive inrush current to the switching element of the inverter circuit 60 caused by applying a pulsed voltage to the stator winding can be avoided. This protects the inverter circuit 60 against inrush current.

In the step-up / down converter circuit 59, the step-up switching element 59b, the reaction device 59d, and the second backflow prevention diode 59e functioning as the step-up converter circuit can function as a high frequency suppression circuit. When suppressing the high frequency current, the boosting switching element 59b may be controlled by a pulse width modulated signal.

As described above, according to the present embodiment, the inverter circuit controller 41b maintains the corresponding switching element of the inverter circuit 60 in the on state during the energization period of the stator windings 26u, 26v, and 26w of each phase. The occurrence of noise and leakage current by the circuit 60 can be reduced.

As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.

For example, although the above-mentioned embodiment demonstrated the case where the compressor drive device 30 is applied to the air conditioner 10, it is not limited to this, For example, even if it applies to a refrigerator, a showcase, a washing machine, etc. good.

In addition, although the above-mentioned embodiment demonstrated the case where the position of a rotor is detected based on an induced voltage without using a hall element, you may detect the position of a rotor directly using a hall element.

In addition, in the above embodiment, the case where the motor drive device includes the step-down converter circuit has been described, but the motor drive device may include the step-down converter circuit having a step-down switching element instead of the step-down converter circuit. . If a boost is necessary, a double voltage circuit may be provided at the output terminal of the rectifier circuit, and the voltage may be boosted in advance in the double voltage circuit, and the DC voltage applied to the inverter circuit may be adjusted by stepping down in the step-down converter circuit.

According to the present invention, generation of noise and leakage current by the inverter circuit can be reduced.

Claims (9)

An inverter circuit having a plurality of switching elements and connected to the stator windings of each phase of a brushless DC motor, and controlling a phase voltage applied to the stator windings of each phase within an energization period for energizing the stator windings of each phase, In the motor drive device for controlling the rotational speed of the rotor to the target rotational speed, A holding part for holding the corresponding switching element in an on state during the energization period of the stator winding of each phase; And a voltage adjusting unit for adjusting a DC voltage applied to the inverter circuit so as to detect the rotational speed of the rotor and make the rotational speed of the rotor the target rotational speed. The motor driving apparatus according to claim 1, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on / off of the step-down switching element to adjust the DC voltage. The voltage regulator of claim 1, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element and a step-up switching element, and control the on / off of the step-down switching element and the step-up switching element to control the DC voltage. Motor drive device, characterized in that for adjusting. A compressor having a brushless DC motor, a circuit of an inverter having a plurality of switching elements, and connected to a stator winding of each phase of the brushless DC motor, wherein the respective energization periods are energized to the stator windings of each phase. A compressor driving apparatus for controlling a phase voltage applied to a stator winding of a phase and controlling a rotational speed of the rotor to a target rotational speed, A holding part for holding the corresponding switching element in an on state during the energization period of the stator winding of each phase; And a voltage adjusting unit for adjusting a DC voltage applied to the inverter circuit so as to detect the rotational speed of the rotor and set the rotational speed of the rotor to a target rotational speed. 5. The compressor driving apparatus according to claim 4, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on / off of the step-down switching element to adjust the DC voltage. The voltage regulator of claim 4, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element and a step-up switching element, and control the on / off of the step-down switching element and the step-up switching element to control the DC voltage. Compressor drive device characterized in that the adjustment. An outdoor unit having a compressor and an outdoor heat exchanger, and an indoor unit having an indoor heat exchanger, wherein the compressor is provided with a brushless DC motor, and an inverter circuit having a plurality of switching elements is connected to the stator windings of each phase of the brushless DC motor. In the air conditioner for controlling the phase voltage to be applied to the stator windings of each phase in the energization period of energizing the stator windings of each phase, to control the rotational speed of the rotor to the target rotational speed, A holding portion for holding the corresponding switching element in an on state during the energization period of the stator winding of each phase; And a voltage adjusting unit for adjusting a DC voltage applied to the inverter circuit so as to detect the rotational speed of the rotor and make the rotational speed of the rotor the target rotational speed. The air conditioner according to claim 7, wherein the voltage adjusting unit includes a step-down converter circuit having a step-down switching element, and controls the on / off of the step-down switching element to adjust the DC voltage. The voltage adjusting part of claim 7, wherein the voltage adjusting part includes a step-up / down converter circuit having a step-down switching element and a step-up switching element, and control the on / off of the step-down switching element and the step-up switching element to control the DC voltage. Air conditioning device, characterized in that for adjusting.