JP2013118754A - Inverter device and air conditioner equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of increase in size of a DC/DC power source circuit and rising of costs because a drive power source for generating an inverse voltage is required to be provided at each upper arm phase separately of an inverter main circuit, relating to an inverse voltage apply circuit contained in an inverter device, that applies an inverse voltage to a diode connected to a switching element in reverse parallel.SOLUTION: The inverter device includes one or more pairs of an upper arm and a lower arm, each containing an inverter main switch element and a reflow diode connected parallel to the inverter main switch element, and further includes a drive circuit which is connected in series to the reflow diode to control the current that flows to the reflow diode. The drive circuit includes a transformer in which a secondary coil is connected in series to the reflow diode, a DC power source which supplies DC to a primary coil of the transformer, and a transformer driving switch element which controls supply of a current to the primary coil of the transformer. Only a single DC power source is provided to be shared to all pairs of the upper arm and the lower arm.

Description

  The present invention relates to an inverter device that converts a DC voltage into an arbitrary AC voltage, and an air conditioner including the inverter device.

  In conventional inverter devices for single-phase or three-phase AC power supplies, each switching element of the inverter main circuit is configured with a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor: MOS-type field effect transistor). In order to suppress the reverse recovery current flowing in the diode connected in reverse parallel to the switching element when the state changes from the ON state to the OFF state, a reverse voltage application circuit with a dedicated power supply is provided in each upper arm phase of the inverter main circuit. (For example, refer to Patent Document 1).

  In addition, there is an inverter device for mounting an air conditioner using a MOSFET only for the switching element of the lower arm of the inverter main circuit and using an IGBT (Insulated Gate Bipolar Transistor) for the switching element of the upper arm (for example, , See Patent Document 2).

Japanese Patent Laying-Open No. 2006-141167 (FIG. 1) Japanese Unexamined Patent Publication No. 2007-74858 (FIG. 1)

  The reverse voltage application circuit included in the inverter device described in Patent Document 1 applies a reverse voltage to a diode connected in reverse parallel to a switching element. A drive power supply for generating the reverse voltage is used as the inverter main circuit. It was necessary to provide each upper arm individually. For this reason, there has been a problem that the DC / DC power supply circuit becomes large in size and high in cost.

  In addition, since the inverter device described in Patent Document 2 uses both MOSFET and IGBT elements in the inverter main circuit, it can be used during low speed operation (load current is small) such as heating intermediate capacity operation of an air conditioner. In applications where the current consumption is small, such as a refrigerator, there is a problem that the merit of the MOSFET having a smaller conduction loss than the IGBT cannot be fully utilized and the energy saving effect cannot be sufficiently expected.

  The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide an inexpensive DC / DC power supply circuit without providing a separate drive power supply for use in the reverse voltage application circuit. A low-loss inverter device is obtained. Moreover, the 2nd objective of this invention is to obtain the inverter apparatus with a high energy-saving effect suitable for air conditioner mounting.

  The inverter device of the present invention is an inverter device having at least one pair of an upper arm and a lower arm each including an inverter main switch element and a reflux diode connected in parallel to the inverter main switch element. A drive circuit that is connected in series and controls a current flowing through the return diode, the drive circuit including a transformer having a secondary winding connected in series to the return diode, and a primary winding of the transformer; A DC power source for supplying DC power to the wire, and a transformer driving switch element for controlling current supply to the primary winding of the transformer. The DC power source includes all pairs of the upper arm and the lower arm. It is characterized by having only one in common.

  The inverter device of the present invention can suppress the reverse recovery current flowing in the parasitic diode built in the inverter main switch element, which is a MOSFET, so that the loss of the inverter device can be reduced and the DC power source of the drive circuit can be shared. As a result, the cost can be reduced.

1 is a diagram showing a system configuration including an inverter device in Embodiment 1. FIG. The figure explaining the circuit operation | movement of an inverter apparatus. The figure explaining the circuit operation | movement of an inverter apparatus. The figure explaining the circuit operation | movement of an inverter apparatus. The figure explaining the circuit operation | movement of an inverter apparatus. The figure explaining the circuit operation | movement of an inverter apparatus. FIG. 5 shows a configuration of a semiconductor module of an inverter device in Embodiment 2. FIG. 5 shows a configuration of a semiconductor module of an inverter device in Embodiment 3. FIG. 10 shows an example of how the inverter device is mounted on a substrate in the fourth embodiment. The figure which shows the structural example of the outdoor unit of the air conditioner provided with the inverter apparatus of Embodiment 1-4.

Embodiment 1.
The configuration and operation of the inverter device in the first embodiment will be described with reference to the drawings. FIG. 1 shows a system configuration including the inverter device of the present embodiment. Since this system includes a converter device and an inverter device, the configuration of the converter device will be described first. The converter device 1 first converts a power signal from the AC power source 2 into a DC voltage by the reactor 3, the rectifier circuit 4 formed of a diode bridge, and smoothing capacitors 5a and 5b. The switch element 6 is a semiconductor switching element such as a transistor, and is connected between one signal line of the AC power supply 2 and an interconnection point between the two smoothing capacitors 5a and 5b, and performs rectification operations of full-wave rectification and voltage doubler rectification. Switch modes. The reactor 3 is for improving the power factor at the time of AC / DC conversion. In addition, a power supply short circuit composed of a diode bridge 7 and a switch element 8 (for example, an IGBT element) is provided between the reactor 3 and one output side of the AC power supply 2. This power supply short circuit is used for PAM converter operation (PAM: Pulse Amplitude Modulation). Since the configuration of the converter device described here is well known, detailed description of the operation is omitted. Note that the configuration of the converter device is not limited to this, and may be one using another known method or configuration (for example, Japanese Patent Application Laid-Open No. 2011-115007).

  Next, the configuration of the inverter device of this system will be described. The inverter device includes an inverter main circuit 9, an inverter control unit 10, and a resistor 11 for detecting bus current of the inverter device, and converts a DC voltage generated between both ends of the smoothing capacitors 5a and 5b into a three-phase AC voltage. Then, the motor 12 is driven. The inverter control unit 10 detects the bus current of the inverter device flowing through the resistor 11 and controls the inverter main circuit 9 based on an operation command signal (not shown).

  The inverter main circuit 9 has a three-phase (U, V, W) configuration with a pair of upper and lower arms corresponding to each phase of U, V, and W. In addition, since the circuit of each phase is the same structure, it demonstrates collectively. First, the circuit configuration of the upper arm will be described. In the upper arm circuit, the switch elements 13 (U, V, W, which are composed of MOSFETs as the inverter main switch elements) are suffixed with subscripts a, b, c corresponding to the phases of U, V, W. In this case, a subscript is omitted as appropriate), and a diode 14 that is a return diode of the switch element 13 and a drive circuit 15 that controls the current flowing through the diode 14 are connected in series to the switch element 13 in parallel. It has a configuration. As the diode 14, a diode having a reverse recovery time shorter than the reverse recovery time of a diode (parasitic diode: not shown) due to the parasitic capacitance of the switch element 13 which is a MOSFET is used.

  The drive circuit 15 includes a transformer 19 whose secondary winding is connected in series with a diode 14 that is a freewheeling diode, a DC power supply 22 that supplies DC to the primary winding of the transformer 19, The switch element 21 is a transformer drive switch element that controls current supply to the secondary winding, and a bypass path diode 20 described later. The switch element 21 is a semiconductor switching element such as a transistor.

  The circuit of the lower arm is basically the same as the circuit of the upper arm, and a structure in which a diode 17 and a drive circuit 18 are connected in series is connected in parallel to a switch element 16 composed of a MOSFET which is an inverter main switch element. is there. Here, the switch element 16, the diode 17 and the drive circuit 18 correspond to the switch element 13, the diode 14 and the drive circuit 15 of the upper arm, respectively.

  The DC power supply 22 may be provided individually for each of the phases and the total of six drive circuits 15 for each arm, but here, only one power supply is provided in common for all pairs of the upper arm and the lower arm, The drive circuit 15 is configured to share this power supply. In this case, the ground terminal (GND) of the DC power supply 22 can be shared with the GND terminal of the inverter main circuit. The diode 20 regenerates the energy stored in the primary side winding of the transformer 19 to the DC power source 22 and forms a bypass path for resetting the magnetic flux generated in the winding.

  The inverter control unit 10 performs on / off control of the switch element 13 in the upper arm and the switch element 21 in each drive circuit 15 included in the inverter main circuit 9, the corresponding switch element in the lower arm, and the switch element in the drive circuit. The desired AC voltage is applied to the motor 12 by performing on / off control.

  Next, the operation of the inverter main circuit 9 will be described with reference to FIGS. FIG. 2 shows an excerpt of the upper arm and lower arm circuits for one phase of the inverter main circuit 9 in FIG. The same parts as those shown in FIG. 1 are denoted by the same reference numerals, and the parasitic diode 23 built in the switch element 13 and the parasitic diode 24 built in the switch element 16 are clearly shown for convenience of explanation of the operation.

  FIG. 2 shows that both the upper arm switch element 13 and the lower arm switch element 16 are in the OFF state under the control of the inverter control unit 10, and the regenerative current flows from the motor 12 side to the inverter main circuit 9 side in the regenerative mode. It shows the state. In addition, it is assumed that the switch element 21 of the upper arm drive circuit 15 is also set to the OFF state under the control of the inverter control unit 10. For this reason, the regenerative current flows to the positive side of the smoothing capacitor 5a via the parasitic diode 23 of the switch element 13 of the upper arm.

  Next, when the regenerative current flows in this way, the switch element 21 of the upper arm drive circuit 15 is switched from OFF to ON. As a result, a current from the DC power source 22 flows in the primary side winding of the transformer 19, so that a voltage is induced in the secondary side winding of the transformer 19. Therefore, a reverse bias is applied to the parasitic diode 23, and the regenerative current flowing in the parasitic diode 23 can be commutated to the secondary winding of the transformer 19 and the path of the diode 14. FIG. 3 shows a state during the commutation operation after the switch element 21 is turned on, and shows a state where the regenerative current is shunted to the parasitic diode 23 and the transformer 19 side. When commutation is completed, the regenerative current flows only in the path of the secondary winding of the transformer 19 and the diode 14 (FIG. 4).

  Next, the switch element 16 of the lower arm is turned on at the timing when commutation is completed. Then, the regenerative current from the motor 12 side flows to the switch element 16 of the lower arm, and a reverse recovery current flows to the diode 14 only for a short time immediately after the switch element 16 is turned on (FIG. 5). When the reverse recovery operation of the diode 14 is completed, only the current from the motor 12 side flows through the switch element 16 of the lower arm (FIG. 6).

  When the switch element 21 is switched from the on state to the off state after the reverse recovery operation is completed, the energy stored in the primary side winding of the transformer 19 is regenerated to the DC power source 22 via the diode 20, so that the magnetism of the transformer 19 Saturation can be prevented.

  As described above, in the first embodiment, when the on / off state of the switch element 13 of the inverter main circuit 9 is switched by the control of the inverter control unit 10, the parasitic element built in the switch element 13 configured by the MOSFET is used. The reverse recovery current flowing through the diode 23 can be suppressed. On the other hand, since the diodes 14 and 17 on the commutation side use a diode having a shorter reverse recovery time than the parasitic diode 23, the loss in the diode can be reduced, and the total loss of the inverter device can be reduced.

  In addition, since the drive circuit 15 applies the voltage via the transformer 19, the DC power supply 22 on the primary side of the transformer 19 can be constituted by a power supply circuit shared by all three phases. Can be configured with an inexpensive DC / DC power supply circuit.

  Further, by configuring all the DC power sources 22 on the primary side of the transformer with a common power source, the GND of the DC power source 22 and the GND of the inverter main circuit 9 can be made common. For this reason, since the control signal from the inverter control part 10 can be transmitted to the drive circuit 15 without passing through an insulation circuit, the circuit scale can be reduced.

  Furthermore, by using a wide band gap semiconductor made of silicon carbide (SiC), gallium nitride (GaN) -based material or diamond having good reverse recovery characteristics for the diode 14, the total loss of the inverter device can be further reduced. Inverter device with high energy saving effect can be obtained.

  In the above description, the drive circuit 15 is individually provided for the upper arm and lower arm switch elements. However, for the lower arm, only one drive circuit 15 is provided for the U, V, and W phases. It is also possible to use both.

  In the above description, the diodes 14 and 17 are connected to the cathodes of the parasitic diodes 23 and 24. However, the diodes 14 and 17 may be connected to the anodes of the parasitic diodes 23 and 24. It goes without saying that the same effect can be obtained by the circuit operation.

  In particular, when the upper arm diode 14 is connected to the anode side of the parasitic diode 23, the upper arm transformer 19 can be used as a single transformer without providing it for each phase. . As a result, only one upper arm drive circuit 15 needs to be provided, so that the board space can be saved and the cost can be reduced.

Embodiment 2.
FIG. 7 is a diagram illustrating an internal circuit of a semiconductor module in which a part of the inverter device described in the first embodiment is incorporated. The semiconductor module 25 is a transfer mold type power semiconductor module, which is a switching element 13a, 13b, 13c in the upper arm of the inverter main circuit 9, a switching element 16a, 16b, 16c in the lower arm, and a diode that is a return diode. 14a, 14b, 14c, 17a, 17b, 17c are built in corresponding to each switch element (13a, 13b, 13c, 16a, 16b, 16c). The control ICs 26a, 26b, and 26c for driving the gate signals of the upper arm switch elements (13a, 13b, and 13c) and the control IC 27 for driving the gate signals of the lower arm switch elements (16a, 16b, and 16c) are provided. Built-in.

  The cathode of the upper arm diode 14 is connected to the cathode of the upper arm parasitic diode 23, and the cathode of the lower arm diode 17 is connected to the cathode of the lower arm parasitic diode 24.

  A control signal from the inverter control unit 10 is connected to the input terminals IN <b> 1 to IN <b> 6 of the semiconductor module 25. The connection terminal P is connected to the positive DC bus of the inverter main circuit 9, and the connection terminals NU, NV, NW are all connected to the negative DC bus of the inverter main circuit 9. The connection terminals U, V, W are connected to the U, V, W phase terminals of the motor 12, respectively. The positive side of the transformer secondary side terminal of the drive circuit 15 corresponding to each switch element (13a, 13b, 13c, 21a, 21b, 21c) is connected to the connection terminals A1 to A6. The negative side of the transformer secondary terminal of the drive circuit 15 is connected to the U, V, and W terminals corresponding to each phase for the upper arm drive circuit 15 and NU, corresponding to each phase for the lower arm drive circuit 15. Connected to NV and NW terminals.

  In the second embodiment, by incorporating a part of the inverter device in a single semiconductor module, the wiring inductance between elements can be greatly reduced, and the circuit can be operated stably. Also, by incorporating the commutation diode in the semiconductor module, it is possible to dissipate heat with the same heat sink all at once with other switch elements, reducing the total mounting area of the components, Space saving can be realized.

Embodiment 3.
FIG. 8 is a diagram showing another configuration example of the semiconductor module incorporating a part of the inverter device described in the first embodiment. Note that components that are the same as or correspond to the components shown in FIG. 7 are denoted by the same reference numerals, and differences from the second embodiment will be mainly described.

  In the semiconductor module 28 of the third embodiment, the upper arm diodes 14a, 14b, and 14c are connected to the anode side of the parasitic diodes 23a, 23b, and 23c, respectively. The cathodes of the diodes 14a, 14b, and 14c are connected in common to serve as the connection terminal A1 as an external terminal of the semiconductor module 23. On the other hand, the lower arm diodes 17a, 17b, and 17c are connected to the cathode sides of the parasitic diodes 24a, 24b, and 24c, respectively, and the anodes of the diodes 17a, 17b, and 17c are connected in common to form the connection terminal A2 outside the semiconductor module 28. It is a terminal.

  One drive circuit 15 for the upper arm is connected to the outside of the semiconductor module 28 via the connection terminal P and the connection terminal A1 of the semiconductor module 28, and the drive circuit for the lower arm is connected via the connection terminal A2 and the connection terminal NW. The inverter main circuit 9 can be configured by connecting one 18. For this reason, since it is only necessary to provide one drive circuit for each arm in the inverter main circuit 9, the mounting area of components can be reduced in total, and the space saving of the board can be realized.

Embodiment 4.
A mounting example of the inverter device described in the first to third embodiments on a substrate will be described with reference to FIG. 9A and FIG.

  The hybrid IC 29 includes a drive circuit 15 excluding the transformer 19 and a drive circuit 18 similarly excluding the transformer portion. The transformer 30 corresponds to the transformer in the drive circuits 15 and 18. The transformer 30 is mounted on the surface of the hybrid IC 29. The power module 31 is the semiconductor module 25 or the semiconductor module 28 described in the second and third embodiments, and includes six switch elements (13a, 13b, 13c, 16a, 16b, 16c) included in the inverter main circuit 9. Built-in control ICs (26a, 26b, 26c, 27) for controlling six diodes (14a, 14b, 14c, 17a, 17b, 17c) and switch elements (13a, 13b, 13c, 16a, 16b, 16c) doing.

  A heat sink 32 for heat dissipation is fixed to the surface of the power module 31 with screws 33. The hybrid IC 29 and the power module 31 are mounted on the printed circuit board 34. The hybrid IC 29 is mounted on one mounting surface of the printed circuit board 34, and the power module 31 is mounted on the board mounting surface opposite to the surface on which the hybrid IC 29 is mounted. Has been implemented.

  Further, the mounting is performed such that the direction of ventilation with respect to the heat sink 32 and the longitudinal direction of the hybrid IC 29 are substantially parallel. By adopting such a mounting form, a part of the wind sent to dissipate the power module 31 can be shunted in the longitudinal direction of the hybrid IC 29, and the slight heat generated from the transformer 30 can also be dissipated. . For this reason, it is not necessary to prepare a separate heat dissipating component for the transformer 30, and the entire inverter device can be efficiently dissipated with one air source.

Embodiment 5.
FIG. 10 is a diagram illustrating a configuration example inside the outdoor unit of the air conditioner including the inverter device according to any of Embodiments 1 to 4. In FIG. 10, the outdoor unit 35 includes an air blower 36 for the indoor unit, an inverter device 37, and a compressor 38 for compressing the refrigerant, and constitutes an air conditioner together with an indoor unit (not shown).

  The inverter device 37 is the inverter device described in the first to fourth embodiments, is attached to the upper part in the outdoor unit 35, and controls a motor in the compressor 38, a motor for the blower fan 36, and the like. . In FIG. 10, since the concept of the overview is shown, wiring and the like are not shown, but the inverter device 37 is connected to the compressor 38 and the blower fan 36 and the like by wiring and the like. The configuration and operation of inverter device 37 are the same as those of the inverter device described in the first to fourth embodiments. For this reason, the loss reduction effect by using the commutation diode with a short reverse recovery time is obtained, and the main switch element in the inverter device is configured by MOSFETs in both the upper arm and the lower arm. In the case of low rotation operation (load current is small) such as heating intermediate capacity operation, it is possible to use the advantage of less conduction loss of the MOSFET and to obtain an air conditioner with more energy saving effect.

  As described above, according to the present embodiment, since the inverter device according to the first to fourth embodiments is applied to an air conditioner, the generated heat is efficiently dissipated with a low loss and a large amount. An increase in size and cost when the capacity is increased can be suppressed, and a cheaper and more reliable air conditioner can be obtained.

DESCRIPTION OF SYMBOLS 1 Converter apparatus 2 AC power source 3 Reactor 4 Rectifier circuit 5 Smoothing capacitor 6, 8, 13, 16, 21 Switch element 7 Diode bridge 9 Inverter main circuit 10 Inverter control part 11 Resistance 12 Motor 14, 17, 20 Diode 15, 18 drive Circuit 19 Transformer 22 DC power supply 23, 24 Parasitic diode 25, 28 Semiconductor module 26, 27 Control IC
29 Hybrid IC
30 Transformer 31 Power module 32 Heat sink 33 Screw 34 Printed circuit board 35 Outdoor unit 36 Blower fan 37 Inverter device 38 Compressor

Claims (9)

An inverter device having a pair of upper and lower arms each including an inverter main switch element and a reflux diode connected in parallel to the inverter main switch element,
A drive circuit that is connected in series to the reflux diode and that controls the current flowing through the reflux diode,
The drive circuit includes a transformer having a secondary winding connected in series to the return diode;
A DC power source for supplying DC to the primary winding of the transformer, and a transformer driving switch element for controlling current supply to the primary winding of the transformer,
The inverter apparatus according to claim 1, wherein only one DC power source is provided in common for all pairs of an upper arm and a lower arm.   2. The inverter device according to claim 1, wherein the inverter main switch element is a MOSFET, and the freewheeling diode is a diode having a shorter reverse recovery time than a parasitic diode of the inverter main switch element.   The inverter device according to claim 2, wherein a cathode of the reflux diode is connected to a cathode of the parasitic diode. An anode of the reflux diode of the upper arm is connected to an anode of the parasitic diode;
The inverter device according to claim 2, wherein a cathode of the reflux diode of the lower arm is connected to a cathode of the parasitic diode.   The inverter device according to claim 1, wherein the reflux diode is formed of a wide gap semiconductor element.   6. The inverter device according to claim 5, wherein the wide band gap semiconductor is silicon carbide (SiC), gallium nitride (GaN) -based material, or diamond.   The inverter apparatus according to claim 1, wherein the inverter main switch element and the reflux diode are mounted by a single semiconductor module. A hybrid IC including the drive circuit excluding the transformer is mounted on one mounting surface of the substrate, and the semiconductor module is mounted on the other mounting surface of the substrate,
The transformer is mounted on the surface of the hybrid IC,
A heat sink is mounted on the surface of the semiconductor module for heat dissipation of the semiconductor module,
The inverter device according to claim 7, wherein the hybrid IC and the semiconductor module are mounted on the substrate so that a ventilation direction of the heat sink and a longitudinal direction of the hybrid IC are substantially parallel to each other.   The air conditioner characterized by driving the motor of the compressor or the motor of the fan for ventilation built in the outdoor unit by the inverter apparatus in any one of Claims 1-8.

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