Power conversion device and air conditioner

Abstract

Provides a highly reliable power conversion device, etc. A power conversion device (100) includes: a conversion circuit (10), a smoothing capacitor (20), an inverter circuit (50), an inverter control circuit (61), and an overvoltage protection circuit (40), and also includes: an overvoltage protection control circuit (62) which performs overvoltage protection control to switch the switching element (41) to the on state when the DC voltage of the smoothing capacitor (20) reaches a specified value after the inverter circuit (50) stops. After the overvoltage protection control starts, the inverter control circuit (61) performs winding short-circuit control to turn on one of the upper and lower arms of the inverter circuit (50) in all phases and turn off the other arm in all phases. The winding short-circuit control starts according to a specified state quantity, wherein the specified state quantity is correlated with the cumulative heat generation of the resistive element (42) generated by the overvoltage protection control.

Description

Technical Field

[0001] This disclosure relates to power conversion devices, etc. Background Technology

[0002] Regarding power conversion devices that include inverter circuits, for example, the technology described in Patent Document 1 is known. That is, Patent Document 1 describes a power conversion device having an overvoltage protection circuit, which has a resistor and a semiconductor element connected in series to protect the inverter circuit from overvoltage.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6421882 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The overvoltage protection circuit described in Patent Document 1 has the following advantages: a simple circuit structure and a high degree of freedom in setting the resistance value of the resistive element and the operating conditions of the switching element. However, after the switching action of the inverter circuit stops, regenerative power is generated in the motor. This regenerative power is consumed by the resistive element of the overvoltage protection circuit (electrical energy is converted into heat energy), thus generating heat in the resistive element. If this heat is too large, it may not only shorten the life of the resistive element but also cause thermal effects on surrounding circuit components. Therefore, the technology described in Patent Document 1 has room for improvement in terms of improving the reliability of the power conversion device.

[0008] Therefore, the subject of this disclosure is to provide a highly reliable power conversion device, etc.

[0009] Methods for solving problems

[0010] To address the aforementioned issues, the power conversion device disclosed herein comprises: a conversion circuit that converts an AC voltage applied from an AC power source into a DC voltage; a smoothing capacitor that smooths the DC voltage at the output side of the conversion circuit; an inverter circuit that converts the DC voltage of the smoothing capacitor into an AC voltage and applies the AC voltage to a motor; an inverter control circuit that controls the inverter circuit; and an overvoltage protection circuit having a series connection of a switching element and a resistive element connected in parallel with the smoothing capacitor. Furthermore, the power conversion device also comprises: an overvoltage protection control circuit that, when the DC voltage of the smoothing capacitor reaches a predetermined value after the inverter circuit stops, performs overvoltage protection control by switching the switching element to an on state; the inverter control circuit, after the overvoltage protection control begins, performs winding short-circuit control by fully connecting one phase of the upper arm and the lower arm of the inverter circuit while simultaneously fully disconnecting the other phase; the winding short-circuit control begins according to a predetermined state quantity, wherein the predetermined state quantity is correlated with the cumulative heat generated by the resistive element accompanying the overvoltage protection control.

[0011] Invention Effects

[0012] According to this disclosure, highly reliable power conversion devices, etc., can be provided. Attached Figure Description

[0013] Figure 1 This is a structural diagram of the power conversion device according to the first embodiment.

[0014] Figure 2A This is an explanatory diagram illustrating an example of winding short-circuit control in the power conversion device of the first embodiment.

[0015] Figure 2B This is an explanatory diagram showing another example of winding short-circuit control in the power conversion device of the first embodiment.

[0016] Figure 3 This is a flowchart illustrating the processing of the control unit of the power conversion device according to the first embodiment.

[0017] Figure 4 It is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the first embodiment.

[0018] Figure 5 This is a flowchart illustrating the processing of the control unit of the power conversion device in the second embodiment.

[0019] Figure 6 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the second embodiment.

[0020] Figure 7 This is a flowchart illustrating the processing of the control unit of the power conversion device in the third embodiment.

[0021] Figure 8 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the third embodiment.

[0022] Figure 9 This is a structural diagram of the power conversion device according to the fourth embodiment.

[0023] Figure 10 This is a flowchart illustrating the processing of the control unit of the power conversion device according to the fourth embodiment.

[0024] Figure 11 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the fourth embodiment.

[0025] Figure 12 This is a flowchart illustrating the processing of the control unit of the power conversion device according to the fifth embodiment.

[0026] Figure 13 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the fifth embodiment.

[0027] Figure 14 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the sixth embodiment.

[0028] Figure 15 This is a structural diagram of the power conversion device according to the seventh embodiment.

[0029] Figure 16 This is a structural diagram of the air conditioner according to the eighth embodiment. Detailed Implementation

[0030] First Implementation Method

[0031] <Structure of Power Conversion Device>

[0032] Figure 1 This is a structural diagram of the power conversion device 100 according to the first embodiment.

[0033] Figure 1 The power conversion device 100 shown is a device that converts alternating current supplied from AC power source E1 into direct current, converts the direct current into a specified alternating current, and outputs it to motor M1. Motor M1 can be, for example, a permanent magnet synchronous motor, or other types of motors. Figure 1As shown, the power conversion device 100 includes: a conversion circuit 10, a smoothing capacitor 20, a DC voltage detection unit 30, an overvoltage protection circuit 40, an inverter circuit 50, an inverter control circuit 61, and an overvoltage protection control circuit 62.

[0034] The conversion circuit 10 is a power converter that converts the AC voltage applied from the three-phase AC power supply E1 into a DC voltage (pulsating DC voltage). Figure 1 In the example, the conversion circuit 10 uses a full-wave rectifier circuit with six diodes D1~D6 connected in a bridge configuration. Alternatively, it can replace... Figure 1 The conversion circuit 10 shown uses a switching method. The output side of the conversion circuit 10 is connected to the inverter circuit 50 via the positive DC line K1, and is also connected to the inverter circuit 50 via the negative DC line K2.

[0035] The smoothing capacitor 20 is a component that smooths the DC voltage (pulsating DC voltage) on the output side of the conversion circuit 10 and is connected to a pair of DC lines K1 and K2. Specifically, one end (one lead) of the smoothing capacitor 20 is connected to the positive DC line K1, and the other end (the other lead) is connected to the negative DC line K2. A film capacitor is used, for example, as such a smoothing capacitor 20.

[0036] Generally speaking, film capacitors are smaller in size (volume) compared to large-capacity electrolytic capacitors. Therefore, using film capacitors as smoothing capacitors 20 enables miniaturization of the circuit board (not shown) of the power conversion device 100. Furthermore, film capacitors have the advantage of longer lifespan compared to electrolytic capacitors. Moreover, since an insulating plastic film is used as the dielectric in film capacitors, an electrolyte is not required as in electrolytic capacitors. Therefore, even when the power conversion device 100 is used in high-temperature environments, film capacitors are virtually immune to malfunctions.

[0037] However, when using small-capacity film capacitors considering the unit price per unit capacitance, the voltage of the film capacitor is prone to fluctuations with changes in the stored charge. For example, when the regenerative current of the motor M1 flows directly into the smoothing capacitor 20 after the switching action of the inverter circuit 50 stops, the DC voltage E of the smoothing capacitor 20... dc The voltage rises sharply. Therefore, the DC voltage E of the smoothing capacitor 20 is suppressed by setting up the overvoltage protection circuit 40. dc The rise. In addition, the type of smoothing capacitor 20 is not limited to film capacitors, but can also be other types of capacitors such as electrolytic capacitors.

[0038] The DC voltage detection unit 30 detects the DC voltage E across the smoothing capacitor 20. dc That is, the DC voltage detection unit 30 detects the DC voltage E between a pair of DC lines K1 and K2. dc For example, the DC voltage E across the smoothing capacitor 20 can be reduced by a series connection of multiple resistive elements (not shown). dc A voltage divider is performed, and the DC voltage E is detected based on the voltage division ratio and the voltage of the specified resistive element. dc The DC voltage detection unit 30 outputs the detected value to the inverter control circuit 61 every moment, and also to the overvoltage protection control circuit 62.

[0039] The overvoltage protection circuit 40 is used to protect the smoothing capacitor 20 from overvoltage and is connected in parallel with the smoothing capacitor 20. For example... Figure 1 As shown, the overvoltage protection circuit 40 has a series connection of a switching element 41 and a resistive element 42. This series connection is connected in parallel with the smoothing capacitor 20. In addition, one end of this series connection is connected to the positive DC line K1, and the other end is connected to the negative DC line K2.

[0040] The switching element 41 is used to switch the flow or interruption of current through the resistive element 42. Such a switching element 41 may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The resistive element 42 is used to dissipate electrical energy associated with the regenerative current of the motor M1 and convert it into heat energy.

[0041] Inverter circuit 50 converts the DC voltage E of smoothing capacitor 20 into DC voltage E. dc The power converter converts the AC voltage to a specified AC voltage and applies that AC voltage to the motor M1. The inverter circuit 50 is configured such that the first branch / second branch / third branch is connected in parallel with the smoothing capacitor 20. The first branch is configured as a pair of switching elements S1 and S2 connected in series (the same applies to the remaining second / third branches). The switching elements S1 to S6, which are components of the first / second / third branches, are, for example, switching elements such as IGBTs and MOSFETs.

[0042] Furthermore, when described from another perspective, the inverter circuit 50 includes: upper arm switching elements S1, S3, and S5 connected to the DC line K1 on the high-potential side; and lower arm switching elements S2, S4, and S6 connected to the DC line K2 on the low-potential side. For example... Figure 1As shown, the connection point between the upper arm switching element S1 and the lower arm switching element S2 of the first branch is connected to the U-phase winding (not shown) of the motor M1 via wiring. Similarly, the connection point between the upper arm switching element S3 and the lower arm switching element S4 of the second branch is connected to the V-phase winding (not shown) of the motor M1 via wiring. The connection point between the upper arm switching element S5 and the lower arm switching element S6 of the third branch is connected to the W-phase winding (not shown) of the motor M1 via wiring.

[0043] Furthermore, in the inverter circuit 50, to prevent damage to the switching elements S1 to S6 caused by commutation, return diodes (not shown) are connected in anti-parallel to each switching element S1 to S6. In addition, if the switching elements S1 to S6 have parasitic diodes, these parasitic diodes function as return diodes; therefore, it is not necessary to provide additional return diodes.

[0044] The inverter control circuit 61 is based on the DC voltage E dc The circuit 61 controls the inverter circuit 50 in a predetermined manner by detecting values, etc. For example, an MCU (Micro Controller Unit) is used as such an inverter control circuit 61. Although not shown, the MCU is configured to include electronic circuitry such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various interfaces. It reads the program stored in the ROM and expands it in the RAM, and the CPU executes various processes.

[0045] The inverter control circuit 61 switches the switching elements S1 to S6 on / off in a predetermined manner according to PWM control, thereby converting the DC voltage of the smoothing capacitor 20 into a three-phase AC voltage. This AC voltage is applied to the U-phase / V-phase / W-phase windings of the motor M1.

[0046] Overvoltage protection control circuit 62 based on DC voltage E dc The detected value is used to control the overvoltage protection circuit 40 in a predetermined manner. Specifically, after the inverter circuit 50 stops, the DC voltage E of the smoothing capacitor 20 is controlled. dc When a specified value is reached, the overvoltage protection control circuit 62 switches the switching element 41 to the ON state. This control is called "overvoltage protection control". Furthermore, the overvoltage protection control circuit 62 can be an analog electronic circuit containing a comparator (not shown), or a microcomputer. Additionally, the inverter control circuit 61 and the overvoltage protection control circuit 62 are collectively referred to as the control unit 60.

[0047] <Regarding DC voltage suppression>

[0048] For example, after the inverter circuit 50 stops, the rotor of the motor M1 temporarily rotates due to inertia. Therefore, the motor M1 functions as a generator, producing regenerative current. When this regenerative current flows directly into the smoothing capacitor 20, the DC voltage E of the smoothing capacitor 20... dc The DC voltage E increases. In particular, when a small-capacity film capacitor is used as the smoothing capacitor 20, the DC voltage E increases with the increase in stored charge. dc The voltage rises sharply. Therefore, in the first embodiment, the DC voltage E is suppressed by providing an overvoltage protection circuit 40. dc The rise in voltage protects the smoothing capacitor 20 from overvoltage.

[0049] Furthermore, as with DC voltage E dc Other methods related to suppression include switching one of the upper and lower arms of inverter circuit 50 on all phases while simultaneously switching the other on all phases off, thus short-circuiting the U-phase / V-phase / W-phase three-phase windings. This control is called "winding short-circuit control." When winding short-circuit control is applied after inverter circuit 50 has stopped, the regenerative current circulates through the switching elements of the upper or lower arm of inverter circuit 50 and the three-phase windings. Therefore, the regenerative current hardly flows from the three-phase windings of motor M1 to the smoothing capacitor 20, thus suppressing the DC voltage E. dc The rise.

[0050] Figure 2A This is an explanatory diagram illustrating an example of winding short-circuit control in a power conversion device 100.

[0051] exist Figure 2A In the example, as winding short-circuit control, inverter control circuit 61 (refer to...) Figure 1 Set the upper arm's switching elements S1, S3, and S5 to the open state, and simultaneously set the lower arm's switching elements S2, S4, and S6 to the closed state. If winding short-circuit control is performed when regenerative current is generated in motor M1 after inverter circuit 50 stops, the regenerative current circulates through the lower arm's switching elements S2, S4, and S6 and the three-phase windings of motor M1.

[0052] Figure 2B This is an explanatory diagram showing another example of winding short-circuit control in the power conversion device 100.

[0053] exist Figure 2B In the example, as winding short-circuit control, inverter control circuit 61 (refer to...) Figure 1Set the upper arm's switching elements S1, S3, and S5 to the ON state, and simultaneously set the lower arm's switching elements S2, S4, and S6 to the OFF state. If winding short-circuit control is performed when regenerative current is generated in motor M1 after inverter circuit 50 stops, the regenerative current circulates through the upper arm's switching elements S1, S3, and S5 and the three-phase windings of motor M1.

[0054] In the following description (including other implementations), a winding short-circuit control is described, such as Figure 2A That would involve setting the upper arm's switching elements S1, S3, and S5 to the off state while simultaneously setting the lower arm's switching elements S2, S4, and S6 to the on state. However, this can also be replaced by, as follows: Figure 2B Control as shown.

[0055] As described above, winding short-circuit control is performed after inverter circuit 50 stops (refer to...). Figure 2A , Figure 2B This can suppress the rise of the DC voltage of the smoothing capacitor 20. However, if winding short-circuit control is started at the same time as the inverter circuit 50 is stopped without special overvoltage protection control, excessive current may flow in the inverter circuit 50 due to the energy accumulated in the three-phase windings of the motor M1 and the electromotive force of the motor M1. In addition, if winding short-circuit control is stopped when the motor M1 is rotating at a high speed without special overvoltage protection control, the regenerative current of the motor M1 flows into the smoothing capacitor 20, therefore, the DC voltage E dc A significant increase.

[0056] Therefore, in the first embodiment, overvoltage protection control is performed for a predetermined time when the control unit 60 stops the inverter circuit 50, and then switching to winding short-circuit control (see reference). Figure 2A , Figure 2B Therefore, it is possible to suppress excessive current flowing through the inverter circuit 50, and at the same time suppress DC voltage E. dc The heat generated by the resistor element 42 can be reduced by shortening the time the regenerative current flows through the resistor element 42 (limited to a specified time).

[0057] <Control Department Processing>

[0058] Figure 3 This is a flowchart illustrating the processing of the control unit of the power conversion device (see also appropriate references). Figure 1 ).

[0059] Furthermore, set as in Figure 3When the inverter circuit is "started", a stop command for the switching operation of the inverter circuit 50 is input. For example, when the motor M1 is used as the drive source for the air conditioner compressor, when the stop button on the remote control (not shown) is pressed, a stop command for the switching operation of the inverter circuit 50 is input to the inverter control circuit 61.

[0060] exist Figure 3 In step S101, the control unit 60 stops the switching operation of the PWM-controlled inverter circuit 50 via the inverter control circuit 61. Furthermore, shortly after the switching operation stops, the rotor of the motor M1 rotates due to inertia, thus the motor M1 functions as a generator. This regenerative current flows into the smoothing capacitor 20 via the DC line K1, therefore, the DC voltage E of the smoothing capacitor 20... dc rise.

[0061] In step S102, the control unit 60 determines the DC voltage E of the smoothing capacitor 20. dc Is it above the specified value V1? Here, the specified value V1 is a voltage threshold that serves as the basis for determining whether to switch the overvoltage protection circuit 40 to the on state, and it is preset.

[0062] In step S102, the DC voltage E of the smoothing capacitor 20 is... dc If the value is less than the specified value V1 (S102: No), the control unit 60 repeatedly performs the determination process in step S103. Additionally, in step S102, the DC voltage E of the smoothing capacitor 20... dc If the value V1 is above the specified value (S102: Yes), the processing of the control unit 60 proceeds to step S103.

[0063] In step S103, the control unit 60 performs (starts) overvoltage protection control via the overvoltage protection control circuit 62. That is, the control unit 60 switches the switching element 41 of the overvoltage protection circuit 40 to the ON state. As a result, the regenerative current of the motor M1 flows through the resistive element 42, and thus, regenerative energy is consumed (converted into heat energy) in the resistive element 42. Consequently, the inflow of regenerative current into the smoothing capacitor 20 is suppressed, and therefore, the DC voltage E of the smoothing capacitor 20 can be suppressed. dc The rise.

[0064] Next, in step S104, the control unit 60 determines whether a predetermined time t has elapsed. on That is, the control unit 60 determines whether the elapsed time since the start of the overvoltage protection control has reached the specified time t. on The aforementioned specified time t on It is a time threshold that serves as the criterion for determining whether to initiate winding short-circuit control, and it is preset.

[0065] Furthermore, the longer the elapsed time from the start of the overvoltage protection control, the longer the regenerative energy of the motor M1 is consumed as heat in the resistive element 42, and consequently, the greater the cumulative heat generation of the resistive element 42 (the value obtained by summing the heat generation successively). Therefore, in the first embodiment, the elapsed time from the start of the overvoltage protection control is used as a "prescribed state quantity," which is correlated with the cumulative heat generation of the resistive element 42 generated accompanying the overvoltage protection control.

[0066] In step S104, the elapsed time from the start of the overvoltage protection control has not reached the specified time t. on If (S104: No) the condition is met, the processing of the control unit 60 returns to step S103. In this case, overvoltage protection control continues. Additionally, if the elapsed time from the start of the overvoltage protection control in step S104 reaches a predetermined time t... on In the case of (S104: Yes), the processing of the control unit 60 proceeds to step S105.

[0067] In step S105, the control unit 60 terminates the overvoltage protection control via the overvoltage protection control circuit 62. That is, the control unit 60 switches the switching element 41 of the overvoltage protection circuit 40 to the open state. Consequently, the time for current to flow through the resistive element 42 of the overvoltage protection circuit 40 is limited to a predetermined time t. on Therefore, the heat generated in the resistor element 42 can be reduced. Thus, in addition to suppressing the shortening of the lifespan of the resistor element 42, the thermal impact on surrounding circuit components can also be suppressed.

[0068] Next, in step S106, the control unit 60 performs winding short-circuit control via the inverter control circuit 61. Specifically, after the overvoltage protection control is initiated, the inverter control circuit 61 performs winding short-circuit control that connects one phase of the upper and lower arms of the inverter circuit 50 while simultaneously disconnecting the other phase (see reference). Figure 2A Thus, in the first embodiment, winding short-circuit control is initiated based on the elapsed time (a specified state quantity) from the start of overvoltage protection control.

[0069] By performing, for example, winding short-circuit control, the regenerative current of motor M1 circulates through the switching elements of inverter circuit 50 in the on state and the three-phase windings. Furthermore, the regenerative energy of motor M1 is consumed as work done to overcome the rotational resistance of motor M1. Therefore, during the execution of winding short-circuit control, the regenerative current hardly flows into smoothing capacitor 20.

[0070] After performing step S106, the control unit 60 ends the series of processes (end). Furthermore, the duration of the winding short-circuit control can be preset. This duration, for example, is set to be longer than the time until the rotation of the motor M1 caused by inertia stops.

[0071] Furthermore, the following trend exists: the faster the rotational speed of motor M1, the greater the regenerative current after inverter circuit 50 stops. Therefore, the faster the rotational speed of motor M1 when inverter circuit 50 stops, the longer the specified time t, which is the criterion for whether to start winding short-circuit control, will be for inverter control circuit 61 to determine whether to start winding short-circuit control. on The larger the threshold value (of the specified state quantity), the better. This helps to suppress excessive current flowing through the inverter circuit 50 during winding short-circuit control.

[0072] Figure 4 This is a timing diagram related to overvoltage protection control and winding short-circuit control (also refer to relevant diagrams). Figure 1 ).

[0073] also, Figure 4 The horizontal axis of each time series plot represents time. Additionally, regarding... Figure 4 The vertical axes of the timing diagrams, starting from the top of the paper, sequentially represent the DC voltage E of the smoothing capacitor 20. dc The cumulative heat generated by the resistive element 42, the operation of the switching element 41 of the overvoltage protection circuit 40, the operation of the upper arm switching elements S1, S3, and S5 of the inverter circuit 50, and the operation of the lower arm switching elements S2, S4, and S6.

[0074] exist Figure 4 In the example, after the switching action of the inverter circuit 50 based on PWM control stops ( Figure 3 (S101), from time t1, the voltage of the smoothing capacitor 20 rises sharply. This is because the induced voltage of the motor M1 generates a regenerative current, which flows into the smoothing capacitor 20. Then, at time t2, the DC voltage E of the smoothing capacitor 20... dc The specified value V1 is reached (S102: Yes). In this case, the overvoltage protection control circuit 62 switches the overvoltage protection circuit 40 to the ON state (S103). As a result, the regenerative current of the motor M1 flows through the resistive element 42, thus suppressing the DC voltage E. dc The rise.

[0075] After the overvoltage protection circuit 40 is switched to the ON state, a specified time t has elapsed. on In the case of ( Figure 3In S104: Yes, at time t3, the overvoltage protection control circuit 62 switches the overvoltage protection circuit 40 to the off state (S105). As a result, current does not flow through the overvoltage protection circuit 40, thus suppressing the heating of the resistive element 42.

[0076] exist Figure 4 In the example, at the moment t3 when the overvoltage protection circuit 40 is switched to the open state, the winding short-circuit control based on the inverter control circuit 61 begins. Figure 3 (S106). Specifically, the inverter control circuit 61 disconnects all phases of the upper arm's switching elements S1, S3, and S5, while simultaneously connecting all phases of the lower arm's switching elements S2, S4, and S6 (see S106). Figure 2A As a result, the regenerative current of motor M1 circulates through the switched elements S2, S4, and S6 in the on state, as well as the three-phase windings. Therefore, during the execution of winding short-circuit control, the regenerative current hardly flows into the smoothing capacitor 20.

[0077] In addition, although Figure 1 The diagram is omitted, but the smoothing capacitor 20 is connected in parallel with the discharge resistor. Therefore, during the execution of winding short-circuit control, current flows from the smoothing capacitor 20 through the discharge resistor. As a result, the DC voltage E of the smoothing capacitor 20... dc Continuing to decrease.

[0078] <Effect>

[0079] According to the first embodiment, after the inverter circuit 50 stops, the DC voltage E of the smoothing capacitor 20 is... dc When the specified value V1 is reached, overvoltage protection control is executed. Therefore, even when a small-capacity film capacitor is used as the smoothing capacitor 20, the DC voltage E can be suppressed. dc The regenerative current of the motor M1 becomes too high. In addition, there is no need to install a detector to detect the current flowing through the resistive element 42, thus reducing the manufacturing cost of the power conversion device 100.

[0080] In addition, a specified time t has elapsed since the start of the overvoltage protection control. on By initiating short-circuit control of the windings, heat generated in the resistive element 42 of the overvoltage protection circuit 40 can be reduced. Therefore, the distance between the resistive element 42 and surrounding circuit components can be shortened during the design phase of the power conversion device 100, thereby alleviating limitations on the circuit pattern and enabling miniaturization of the circuit board.

[0081] Furthermore, since winding short-circuit control does not need to start simultaneously with the shutdown of inverter circuit 50, excessive current flow through inverter circuit 50 can be suppressed. Therefore, according to the first embodiment, a highly reliable power conversion device 100 can be provided.

[0082] Second Implementation Method

[0083] The second embodiment differs from the first embodiment in that it initiates winding short-circuit control based on the amount of DC voltage drop after the overvoltage protection control begins. Furthermore, regarding other structures (such as the structure of the power conversion device 100), please refer to... Figure 1 This is the same as the first embodiment. Therefore, the parts that differ from the first embodiment will be described, and the repeated parts will be omitted.

[0084] Figure 5 This is a flowchart illustrating the processing of the control unit of the power conversion device in the second embodiment (see also the flowchart). Figure 1 ).

[0085] also, Figure 5 Steps S101-S103, S105, and S106 are the same as in the first embodiment (see reference). Figure 3 As explained in [the previous section], that is, after the control unit 60 stops the switching operation of the inverter circuit 50 (S101), the DC voltage E [is then adjusted / adjusts]. dc If the value V1 is above the specified value (S102: Yes), overvoltage protection control is performed (S103).

[0086] Next, in step S204, the control unit 60 determines the DC voltage E. dc Is the decrease in amount equal to the specified value E? ON That is, the control unit 60 determines the DC voltage E after the overvoltage protection control starts. dc If the change peaks and then declines, is the amount of decline from the peak the specified value E? ON The above. The specified value E. ON It is a threshold value of the voltage drop (absolute value) that serves as the basis for determining whether to initiate winding short-circuit control, and it is preset.

[0087] In addition, the following trend exists: the DC voltage E when overvoltage protection control is executed... dc The greater the drop in voltage, the greater the cumulative heat generation of the resistive element 42. Therefore, in the second embodiment, a state quantity is used as a "prescribed state quantity" that is correlated with the cumulative heat generation of the resistive element 42 accompanying overvoltage protection control. That is, the "prescribed state quantity" is the drop in voltage E after the overvoltage protection control begins. dcWhen a change in a value rises, reaches a peak, and then declines, the amount of decline from the peak value.

[0088] In step S204, the DC voltage E dc The decrease is less than the specified value E ON In the case of (S204: No), the processing of the control unit 60 returns to step S103. In this case, overvoltage protection control continues. Additionally, in step S204, the DC voltage E... dc The decrease is the specified value E ON In the above case (S204: Yes), the control unit 60 proceeds to step S105. Then, the control unit 60 ends the overvoltage protection control (S105) and executes the winding short-circuit control (S106). Thus, based on the DC voltage E after the overvoltage protection control starts... dc When the decrease in the value (specified state value) is detected, short-circuit control of the winding is initiated.

[0089] Furthermore, the faster the motor M1 rotates when the inverter circuit 50 is stopped, the more the inverter control circuit 61 sets the predetermined value E, which serves as the criterion for determining whether to initiate winding short-circuit control. ON The larger the threshold value (of the specified state quantity), the better. This helps to suppress excessive current flow through the inverter circuit 50.

[0090] Figure 6 This is a timing diagram related to overvoltage protection control and winding short-circuit control (also refer to relevant diagrams). Figure 1 ).

[0091] In addition, regarding Figure 6 The horizontal / vertical axes of each time series plot are related to... Figure 4 The same as in [the previous text], therefore the explanation is omitted. Figure 6 In the example, DC voltage E dc When the change transitions from rising to a peak E0 and then falling, the amount of decrease from the peak E0 reaches the specified value E at time t3. ON ( Figure 5 S204: Yes). In this case, the control unit 60 ends the overvoltage protection control (S105) and executes the winding short-circuit control (S106). As a result, current does not flow through the overvoltage protection circuit 40, and therefore, the DC voltage E can be suppressed. dc The increase in resistance can simultaneously reduce the cumulative heat generation of resistive element 42.

[0092] <Effect>

[0093] According to the second embodiment, at DC voltage E dc The decrease reached the specified value E ON The winding short-circuit control begins at this time. Additionally, the greater the heat generated by the resistive element 42, the higher the DC voltage E. dcThe decreasing amount of the winding also tends to be larger, so it is possible to start winding short-circuit control at the appropriate time.

[0094] Third Implementation Method

[0095] The third embodiment differs from the first embodiment in that it initiates winding short-circuit control based on the cumulative value of the DC voltage drop after the overvoltage protection control begins. Furthermore, regarding other structures (such as the structure of the power conversion device 100), please refer to... Figure 1 This is the same as the first embodiment. Therefore, the parts that differ from the first embodiment will be described, and the repeated parts will be omitted.

[0096] Figure 7 This is a flowchart illustrating the processing of the control unit of the power conversion device in the third embodiment (see also the flowchart). Figure 1 ).

[0097] also, Figure 7 Steps S101-S103, S105, and S106 are the same as in the first embodiment (see reference). Figure 3 As explained in [the previous section], that is, after the control unit 60 stops the switching operation of the inverter circuit 50 (S101), the DC voltage E [is then adjusted / adjusts]. dc If the voltage reaches or exceeds the specified value V1 (S102: Yes), overvoltage protection control is executed (S103).

[0098] Next, in step S304, the control unit 60 determines the DC voltage E. dc Is the cumulative value of the decrease (the value obtained by summing the values ​​of each successive decrease) equal to the specified value E? dec That is, the control unit 60 determines the DC voltage E after the overvoltage protection control starts. dc When the change peaks and then declines, is the cumulative decrease from the peak value E equal to the specified value E? dec The above. The specified value E. dec It is a threshold value of the cumulative voltage drop (absolute value) that serves as the basis for determining whether to initiate winding short-circuit control, and it is preset.

[0099] Furthermore, the following trend exists: the DC voltage E during the execution of overvoltage protection control... dc The greater the cumulative decrease in voltage, the greater the cumulative heat generation of the resistive element 42. Therefore, in the third embodiment, a state quantity is used as a "prescribed state quantity" that is correlated with the cumulative heat generation of the resistive element 42 accompanying overvoltage protection control. That is, the cumulative decrease in voltage is used as a "prescribed state quantity": the cumulative value of the DC voltage E after the overvoltage protection control starts. dcThe cumulative value of the decrease from the peak when the change from rising to peak turns to falling.

[0100] In step S304, the DC voltage E dc The cumulative value of the decrease is less than the specified value E dec In the case of (S304: No), the processing of the control unit 60 proceeds to step S305.

[0101] In step S305, the control unit 60 determines the DC voltage E dc Is it below the specified value V2? Furthermore, the specified value V2 is a threshold voltage that serves as the basis for determining whether to interrupt overvoltage protection control, and it is preset to a value lower than the aforementioned specified value V1.

[0102] In step S305, the DC voltage E dc If the value V2 is higher than the specified value (S305: No), the control unit 60 repeatedly performs the determination process in step S305. Additionally, in step S305, the DC voltage E... dc If the value V2 is below the specified value (S305: Yes), the control unit 60 returns to step S102. Thus, the control unit 60 adjusts the DC voltage E... dc The overvoltage protection circuit 40 is alternately switched on (S103) and off (S306).

[0103] In addition, in step S304, the DC voltage E dc The cumulative value of the decrease is the specified value E. dec In the above case (S304: Yes), the control unit 60 proceeds to step S105. In this case, since the prescribed amount of regenerative energy has been consumed by the resistor element 42, there is no need to worry about excessive current flowing through the inverter circuit 50 even if winding short-circuit control is started.

[0104] Then, the control unit 60 terminates the overvoltage protection control (S105) and executes the winding short-circuit control (S106). Thus, in the third embodiment, the inverter control circuit 61 adjusts the DC voltage E after the overvoltage protection control stops. dc The cumulative value of the decrease initiates winding short-circuit control. Furthermore, regarding the DC voltage E... dc The cumulative value of the decrease can be reset when the winding short-circuit control begins.

[0105] in addition, Figure 7 The flowchart shown is an example and is not limited to it. For example, it can be based on the DC voltage E. dc Based on the comparison results with the specified values ​​V1 and V2, the control unit 60 alternately and repeatedly switches the overvoltage protection circuit 40 on and off, and simultaneously, repeatedly checks the DC voltage E.dc The cumulative value of the decrease and the specified value E dec The comparison. Then, at DC voltage E dc The cumulative value of the decrease becomes the specified value E. dec In the above situations, the control unit 60 can execute steps S105 and S106 as an interrupt handler. Such a process achieves the same effect.

[0106] Alternatively, the faster the motor M1 rotates when the inverter circuit 50 is stopped, the more the inverter control circuit 61 sets a predetermined value E, which serves as the criterion for determining whether to initiate winding short-circuit control. dec The larger the threshold value (of the specified state quantity), the better. This helps to suppress excessive current flow through the inverter circuit 50.

[0107] Additionally, the DC voltage E can be maintained even during the execution of winding short-circuit control. dc If the specified value V1 is reached again (i.e., even if the start condition for overvoltage protection control is met again), the control unit 60 will not start overvoltage protection control. This suppresses the increase in the cumulative heat generated by the resistive element 42.

[0108] Figure 8 This is a timing diagram related to overvoltage protection control and winding short-circuit control (also refer to relevant diagrams). Figure 1 ).

[0109] also, Figure 8 The vertical axis of the second timing diagram from the top of the paper represents the DC voltage E. dc The cumulative value of the decrease. Regarding Figure 8 The remaining vertical axis of the time series diagram, due to its relation to... Figure 4 The same as in [the previous text], therefore the explanation is omitted.

[0110] exist Figure 8 In the example, with the shutdown of inverter circuit 50, the DC voltage E at time t2... dc Reaching the specified value V1 ( Figure 7 S102: Yes), therefore, the overvoltage protection circuit 40 is switched to the ON state (S103). At the subsequent time t3, the DC voltage E dc The voltage drops to the specified value V2 (S305: Yes), therefore, the overvoltage protection circuit 40 temporarily switches to the off state (S306). Furthermore, at time t3, the DC voltage E... dc The cumulative value of the decrease did not reach the specified value E. dec (S304: No), therefore, winding short-circuit control is not started yet.

[0111] exist Figure 8 After time t3, the DC voltage E dcThe DC voltage E rises again at time t4 due to the regenerative energy of motor M1. dc Reaching the specified value V1 ( Figure 7 S102: Yes), therefore, the overvoltage protection circuit 40 switches to the ON state again (S103). At the subsequent time t5, the DC voltage E dc The cumulative value of the decrease reaches the specified value E dec (S304: Yes), therefore, the control unit 60 switches the overvoltage protection circuit 40 to the off state (S105) and starts winding short-circuit control (S106).

[0112] <Effect>

[0113] According to the third embodiment, at DC voltage E dc The cumulative value of the decrease reaches the specified value E dec The timing for initiating winding short-circuit control is as follows. Here, the following trend exists: DC voltage E dc The greater the cumulative decrease in energy, the greater the cumulative heat generation of the resistive element 42, and the smaller the unconsumed regenerative energy. Therefore, according to the third embodiment, winding short-circuit control can be initiated at a more suitable time than in the second embodiment.

[0114] Fourth Implementation Method

[0115] The fourth embodiment differs from the first embodiment in that: the power conversion device 100A (refer to...) Figure 9 It has a current detector 70 (refer to) Figure 9 Furthermore, the fourth embodiment differs from the first embodiment in that winding short-circuit control begins when the detection value of the current detector 70 reaches a predetermined value. Otherwise, the other structures are the same as in the first embodiment. Therefore, the parts that differ from the first embodiment will be described, and repeated descriptions will be omitted.

[0116] Figure 9 This is a structural diagram of the power conversion device 100A according to the fourth embodiment.

[0117] Figure 9 The power conversion device 100A shown, except for the first embodiment (see reference 100A), Figure 1 In addition to the structures described herein, a current detector 70 is also included. The current detector 70 detects the current flowing through the resistive element 42 and is connected in series with the resistive element 42 and the switching element 41. Such a current detector 70 may be, for example, a shunt resistor or a current sensor. The detection value of the current detector 70 at any given time is output to the control unit 60.

[0118] Figure 10 This is a flowchart illustrating the processing of the control unit of the power conversion device (see also appropriate references). Figure 9 ).

[0119] also, Figure 10 Steps S101-S103, S105, and S106 are the same as in the first embodiment (see reference). Figure 3 As explained in [the previous section], that is, after the control unit 60 stops the switching operation of the inverter circuit 50 (S101), the DC voltage E [is then adjusted / adjusts]. dc If the value V1 is above the specified value (S102: Yes), overvoltage protection control is performed (S103).

[0120] Next, in step S404, the control unit 60 determines whether the current detection value I (the detection value of the current detector 70) is a predetermined value I. ON That is, the control unit 60 determines whether the magnitude of the current flowing through the resistive element 42 after the overvoltage protection control starts reaches the predetermined value I. ON The above. The aforementioned specified value I. ON It is a current threshold that serves as the criterion for determining whether to initiate winding short-circuit control, and it is preset.

[0121] Furthermore, there is a trend that the greater the current flowing through the resistor element 42 during overvoltage protection control, the greater the cumulative heat generated by the resistor element 42. Therefore, in the fourth embodiment, the magnitude of the current flowing through the resistor element 42 after the overvoltage protection control begins is used as a "prescribed state quantity," which is correlated with the cumulative heat generated by the resistor element 42 accompanying the overvoltage protection control.

[0122] In step S404, the current detection value I is less than the specified value I. ON If the condition is not met (S404: No), the processing of the control unit 60 returns to step S103. In this case, overvoltage protection control continues. Additionally, in step S404, the current detection value I is the predetermined value I. ON In the above case (S404: Yes), the processing of the control unit 60 proceeds to step S105. Then, the control unit 60 ends the overvoltage protection control (S105) and executes the winding short-circuit control (S106). Thus, the winding short-circuit control begins based on the magnitude of the current flowing through the resistive element 42 after the overvoltage protection control starts (a predetermined state quantity).

[0123] Furthermore, the faster the rotational speed of the motor M1 when the inverter circuit 50 is stopped, the more the inverter control circuit 61 sets a predetermined value I, which serves as the criterion for determining whether to initiate winding short-circuit control. ON The larger the threshold value (of the specified state quantity), the better. This helps to suppress excessive current flow through the inverter circuit 50.

[0124] Figure 11This is a timing diagram related to overvoltage protection control and winding short-circuit control of power conversion devices (also refer to relevant diagrams). Figure 9 ).

[0125] also, Figure 11 The vertical axis of the second timing diagram from the top of the paper represents the current detection value in current detector 70. Regarding... Figure 11 The remaining vertical axis of the time series diagram, due to its relation to... Figure 4 The same as in [the previous text], therefore the explanation is omitted.

[0126] exist Figure 11 In the example, the current detected value of current detector 70 reaches the specified value I at time t3. ON ( Figure 10 S404: Yes). In this case, the overvoltage protection control circuit 62 switches the overvoltage protection circuit 40 to the open state (S105). Therefore, current does not flow through the overvoltage protection circuit 40, thus suppressing the heating of the resistive element 42. Figure 10 In the example, winding short-circuit control begins at moment t3 when the overvoltage protection circuit 40 is switched to the open state (S106). This allows the suppression of DC voltage E. dc The rise in energy consumption can simultaneously consume the regenerative energy of motor M1.

[0127] <Effect>

[0128] According to the fourth embodiment, when the detected value of the current flowing through the resistive element 42 reaches a predetermined value I... ON The winding short-circuit control is initiated at the appropriate time. In addition, since there is a tendency for the heat generated by the resistor element 42 to increase as the current flowing through it increases, the winding short-circuit control can be initiated at the appropriate time.

[0129] Fifth Implementation Method

[0130] The difference between the fifth and fourth embodiments is that: according to the flow through the resistive element 42 (refer to...) Figure 9 The accumulated value of the current is used to initiate winding short-circuit control. Furthermore, regarding other structures (such as the structure of the power conversion device 100A, please refer to...), Figure 9 This is the same as the fourth embodiment. Therefore, the parts that differ from the fourth embodiment will be described, and the descriptions of repeated parts will be omitted.

[0131] Figure 12 This is a flowchart illustrating the processing of the control unit of the power conversion device in the fifth embodiment (see also, as appropriate). Figure 9 ).

[0132] also, Figure 12 Steps S101-S103, S105, and S106 are the same as in the first embodiment (see reference). Figure 3 As explained in [the previous section], that is, after the control unit 60 stops the switching operation of the inverter circuit 50 (S101), the DC voltage E [is then adjusted / adjusts]. dc If the value V1 is above the specified value (S102: Yes), overvoltage protection control is performed (S103).

[0133] Next, in step S504, the control unit 60 determines whether the cumulative value of the current detection value I (the value obtained by summing up successive times) is the predetermined value I. dec That is, the control unit 60 determines whether the cumulative value of the current flowing through the resistive element 42 after the overvoltage protection control starts is the specified value I. dec The above. The aforementioned specified value I. dec The threshold value of the accumulated current, which serves as the criterion for determining whether to initiate winding short-circuit control, is preset.

[0134] Furthermore, there is a trend that the greater the cumulative value of the current flowing through the resistor element 42 during overvoltage protection control, the greater the cumulative heat generation of the resistor element 42. Therefore, in the fifth embodiment, the cumulative value of the current flowing through the resistor element 42 after the overvoltage protection control begins is used as a "prescribed state quantity," which is correlated with the cumulative heat generation of the resistor element 42 accompanying the overvoltage protection control.

[0135] After processing in step S504, the control unit 60 ends the overvoltage protection control (S105) and executes the winding short-circuit control (S106). Thus, the winding short-circuit control begins based on the accumulated value (prescribed state value) of the current flowing through the resistive element 42 after the overvoltage protection control begins. Furthermore, the accumulated value of the current flowing through the resistive element 42 can also be reset when the winding short-circuit control begins.

[0136] Alternatively, the faster the motor M1 rotates when the inverter circuit 50 is stopped, the more the inverter control circuit 61 sets a predetermined value I, which serves as the criterion for determining whether to initiate winding short-circuit control. dec The larger the threshold value (of the specified state quantity), the better. This helps to suppress excessive current flow through the inverter circuit 50.

[0137] Figure 13 This is a timing diagram related to overvoltage protection control and winding short-circuit control (also refer to relevant diagrams). Figure 9 ).

[0138] also, Figure 13 The vertical axis of the third timing diagram from the top of the paper represents the cumulative value of the current detected in current detector 70. Regarding... Figure 13 The remaining vertical axis of the time series diagram, due to its relation to... Figure 11 The same as in [the previous text], therefore the explanation is omitted.

[0139] exist Figure 13 In the example, during the period when the overvoltage protection circuit 40 is in the ON state (times t2~t3), current flows through the current detector 70. Therefore, the current detection value at every moment is greater than zero, resulting in a monotonically increasing cumulative current detection value. Then, when the cumulative current detection value reaches the predetermined value I... dec In the case of ( Figure 12 S504: Yes), at time t3, the overvoltage protection circuit 40 is switched to the open state (S105), and winding short-circuit control is started (S106).

[0140] <Effect>

[0141] According to the fifth embodiment, when the cumulative value of the current detection value reaches a predetermined value I... dec The timing for initiating winding short-circuit control is as follows. Here, the following trend exists: the larger the cumulative value of the current detection, the greater the cumulative heat generation of the resistive element 42, and the smaller the unconsumed regenerative energy. Therefore, according to the fifth embodiment, winding short-circuit control can be initiated at a more suitable time than in the fourth embodiment.

[0142] The Sixth Implementation Method

[0143] The sixth embodiment differs from the first embodiment in that winding short-circuit control begins before the overvoltage protection control ends. Furthermore, regarding other structures (such as the structure of the power conversion device 100), please refer to... Figure 1 This is the same as the first embodiment. Therefore, the parts that differ from the first embodiment will be described, and the descriptions of repeated parts will be omitted.

[0144] Figure 14 This is a timing diagram related to overvoltage protection control and winding short-circuit control of the power conversion device in the sixth embodiment (also refer to as appropriate). Figure 1 ).

[0145] In addition, regarding Figure 14 The horizontal / vertical axes of each time series plot, and Figure 4 The same applies as in [the previous text], therefore, the explanation is omitted.

[0146] exist Figure 14 In the example, in the DC voltage E dc At time t2, when the specified value V1 is reached, the overvoltage protection circuit 40 is switched on. During the period from time t2 to t4 (i.e., the specified time t... ON During this period, the overvoltage protection circuit 40 remains in the ON state. On the other hand, the switching elements S2, S4, and S6 of the lower arm are switched to the ON state at time t3. That is, winding short-circuit control begins at time t3, before the end of the overvoltage protection control (time t4).

[0147] <Effect>

[0148] According to the sixth embodiment, winding short-circuit control begins before the overvoltage protection control ends; therefore, the execution times of overvoltage protection control and winding short-circuit control partially overlap. This allows for faster processing of the DC voltage E of the smoothing capacitor 20. dc The rate of decrease.

[0149] The Seventh Implementation Method

[0150] The difference between the seventh embodiment and the first embodiment lies in the overvoltage protection circuit 40B (see reference). Figure 15 The structure is the same as in the first embodiment, while the other structures are the same. Therefore, the parts that differ from the first embodiment will be described, and the descriptions of repeated parts will be omitted.

[0151] Figure 15 This is a structural diagram of the power conversion device 100B according to the seventh embodiment.

[0152] like Figure 15 As shown, the overvoltage protection circuit 40B of the power conversion device 100B has a first parallel connection consisting of a resistor 42, a capacitor 43, and a diode 44 connected in parallel. Furthermore, the overvoltage protection circuit 40B has a second parallel connection consisting of a switch 41, a resistor 45, and a diode 46 connected in parallel. The first and second parallel connections are connected in series. One end of this series connection is connected to the positive DC line K1, and the other end is connected to the negative DC line K2.

[0153] Figure 15 The capacitor 43 shown is a component that stores charge when the switching element 41 is in the ON state, and is connected in parallel with the resistive element 42, etc. An electrolytic capacitor is used as such a capacitor 43, for example. Furthermore, Figure 15 The circuit structure shown is also included in the overvoltage protection circuit 40B, which has a series connection of switching element 41 and resistive element 42.

[0154] Diodes 44 and 46 are elements used to form current paths when a reverse voltage is applied to the switching element 41. The cathode of diode 44 is connected to the positive DC line K1, and the anode is connected to the negative DC line K2 via a second parallel connector. The anode of diode 46 is connected to the negative DC line K2, and the cathode is connected to the positive DC line K1 via a first parallel connector. Resistor 45 is a high-impedance resistor used to stabilize the voltage applied to the switching element 41.

[0155] <Effect>

[0156] According to the seventh embodiment, when the switching element 41 is switched to the ON state, the power stored in the capacitor 43 is consumed by the resistive element 42. Therefore, in addition to suppressing abrupt changes in the current flowing through the resistive element 42, it is also possible to suppress the temperature rise of the resistive element 42. Furthermore, by providing diodes 44 and 46, a current path can be formed when a reverse voltage is applied to the switching element 41.

[0157] The Eighth Implementation Method

[0158] In the eighth embodiment, the power conversion device 100 having the structure described in the first embodiment (see reference) Figure 1 Air conditioner W1 (refer to) Figure 16 The following will be explained. Furthermore, the structure and processing of the power conversion device 100 are the same as in the first embodiment, therefore, their description is omitted.

[0159] Figure 16 This is a structural diagram of the air conditioner W1 according to the eighth embodiment.

[0160] also, Figure 16 The solid arrow indicates the flow of refrigerant in the heating cycle.

[0161] in addition, Figure 16 The dashed arrows indicate the flow of refrigerant in the refrigeration cycle.

[0162] Air conditioner W1 is a device that performs air conditioning operations such as cooling and heating. For example... Figure 16 As shown, the air conditioner W1, installed in the outdoor unit U1, includes: a compressor 91, an outdoor heat exchanger 92, an outdoor fan 93, an expansion valve 94, and a four-way valve 95. Additionally, the air conditioner W1, installed in the indoor unit U2, includes an indoor heat exchanger 96 and an indoor fan 97.

[0163] In addition, although Figure 16 The illustrations are omitted, but the air conditioner W1 has a power conversion device 100 with the same structure as in the first embodiment (see reference). Figure 1 The power conversion device 100 is installed on the circuit board of the outdoor unit U1 (not shown).

[0164] Compressor 91 is a device that compresses a low-temperature, low-pressure gaseous refrigerant and sprays it out as a high-temperature, high-pressure gaseous refrigerant. Furthermore, although in Figure 16 The diagram is omitted, but the receiver for refrigerant gas-liquid separation is connected to the suction side of the compressor 91. Furthermore, the electric motor M1, which drives the compressor 91, is connected to the power conversion device 100 (see reference 100). Figure 1 Inverter circuit 50 (refer to) Figure 1 Connect to the output side of the device.

[0165] The outdoor heat exchanger 92 is a heat exchanger that exchanges heat between the refrigerant flowing in its heat transfer tubes and the outside air supplied from the outdoor fan 93. The outdoor fan 93 is a fan that supplies outside air to the outdoor heat exchanger 92. The outdoor fan 93 has an outdoor fan motor 93a as a drive source and is located near the outdoor heat exchanger 92.

[0166] Expansion valve 94 is a valve that reduces the pressure of the refrigerant after it has condensed in the "condenser" (one of the outdoor heat exchanger 92 and the indoor heat exchanger 96). The refrigerant reduced by the pressure of expansion valve 94 is then directed to the "evaporator" (the other of the outdoor heat exchanger 92 and the indoor heat exchanger 96).

[0167] The indoor heat exchanger 96 is a heat exchanger that exchanges heat between the refrigerant flowing in its heat transfer tubes (not shown) and the indoor air (air in the air-conditioned room) supplied from the indoor fan 97.

[0168] The indoor fan 97 is a fan that delivers indoor air into the indoor heat exchanger 96. The indoor fan 97 has an indoor fan motor 97a as a drive source and is located near the indoor heat exchanger 96.

[0169] The four-way valve 95 is a valve that switches the refrigerant flow path according to the operating mode of the air conditioner W1. For example, during cooling operation (refer to...). Figure 16 (The dashed arrow indicates that the refrigerant circulates sequentially through compressor 91, outdoor heat exchanger 92 (condenser), expansion valve 94, and indoor heat exchanger 96 (evaporator). Additionally, during heating operation (see...),... Figure 16 (Solid arrows indicate the refrigerant's circulation path). The refrigerant circulates sequentially through the compressor 91, indoor heat exchanger 96 (condenser), expansion valve 94, and outdoor heat exchanger 92 (evaporator). Air that has exchanged heat with the refrigerant circulating in the indoor heat exchanger 96 is blown from the indoor unit U2 into the air-conditioned room.

[0170] <Effect>

[0171] According to the eighth embodiment, the air conditioner W1 has a power conversion device 100 with the same structure as the first embodiment (see reference). Figure 1 Therefore, the reliability of air conditioner W1 is improved.

[0172] Variations

[0173] The power conversion devices 100, 100A, 100B and air conditioner W1 of this disclosure have been described above in various embodiments, but are not limited to these descriptions and various modifications can be made.

[0174] For example, in the first embodiment (see reference) Figure 4 The description in the document outlines the scenario where winding short-circuit control begins at the point when overvoltage protection control ends, but it is not limited to this. That is, winding short-circuit control can also begin after a predetermined time has elapsed since the end of overvoltage protection control. Furthermore, the second to fifth embodiments are essentially the same.

[0175] Furthermore, in each embodiment, the overvoltage protection control circuit 62 (refer to...) Figure 1 The case described is composed of an analog electronic circuit containing a comparator or a microcomputer, but is not limited thereto. For example, the overvoltage protection control circuit 62 can also be constructed by combining the specified analog electronic circuit and microcomputer.

[0176] Additionally, the overvoltage protection circuits 40 and 40B described in each embodiment (see reference) Figure 1 , Figure 15 The structure shown is just one example and is not limited to it. That is, any circuit that has the function of protecting the smoothing capacitor 20 from overvoltage can also have other structures.

[0177] Additionally, in each embodiment, the AC power supply E1 (refer to...) Figure 1 The example provided describes the use of a three-phase AC power supply, but it is not limited to this; a single-phase AC power supply can also be used.

[0178] Furthermore, in each embodiment, for DC lines K1 and K2 (refer to...) Figure 1 The structure without a specially designed reactor has been described, but it is not limited to this. That is, a reactor may be provided on at least one of the DC lines K1 and K2. For example, in the positive DC line K1, a reactor may be provided between the connection point of the DC line K1 and the smoothing capacitor 20 and the switching circuit 10 (the same applies to the reactor of the negative DC line K2).

[0179] Additionally, in each embodiment, the smoothing capacitor 20 (refer to...) Figure 1 The description only covers the case where the number of capacitors is one, but it is not limited to this. That is, a smoothing capacitor can also be formed by connecting multiple capacitors in series, parallel, or series-parallel. In this case, "the DC voltage of the smoothing capacitor" refers to the voltage across the smoothing capacitor (the DC voltage between DC lines K1 and K2) when the capacitances of the multiple capacitors described above are combined and considered as a single smoothing capacitor. Furthermore, the same applies to the second to seventh embodiments.

[0180] Furthermore, in the seventh embodiment, the overvoltage protection circuit 40B (refer to...) Figure 15The structure described herein includes a first parallel connection of resistive element 42, capacitor 43, and diode 44, and a second parallel connection of switching element 41, resistive element 45, and diode 46, but is not limited thereto. That is, it may also be configured such that the switching element 41 is connected in series with the parallel connection of resistive element 42 and capacitor 43, and the remaining elements are omitted appropriately.

[0181] Furthermore, the various embodiments can be appropriately combined. For example, one of the first to fifth embodiments can be combined with the sixth embodiment (see [reference]). Figure 14 The combination of these components initiates winding short-circuit control before the overvoltage protection control ends.

[0182] Alternatively, one of the first to sixth embodiments can be combined with the seventh embodiment (see reference). Figure 15 This combination is used as an overvoltage protection circuit 40B. Figure 15 The structure shown.

[0183] Alternatively, one of the first to seventh embodiments can be combined with the eighth embodiment (see reference). Figure 16 The combination of the inverter circuit 50 and the motor M1 connected to the inverter circuit 50 is used as the driving source for the compressor of the air conditioner.

[0184] Additionally, in the eighth embodiment (see...) Figure 16 In the power conversion device 100 (refer to) Figure 1 The structure connecting the compressor 91 to the electric motor M1 has been described, but is not limited thereto. For example, it could also be an outdoor fan motor 93a (see [reference]). Figure 16 Alternatively, the motor M1 of the compressor 91 can be connected to the power conversion device 100, and the outdoor fan motor 93a can also be connected to the power conversion device 100.

[0185] Additionally, in the eighth embodiment (see...) Figure 16 The structure of the air conditioner W1 with a four-way valve 95 is described in the document, but it is not limited to this. That is, the four-way valve 85 can also be omitted appropriately, and the air conditioner can be set up as a dedicated air conditioner for cooling or heating.

[0186] Additionally, the eighth embodiment (see Figure 16 In addition to room air conditioning, it can also be applied to various air conditioning units such as commercial air conditioners and multi-split air conditioners for buildings. Furthermore, the eighth embodiment can also be applied to other equipment such as water heaters, refrigerators, and air conditioning hot water systems.

[0187] Furthermore, the various embodiments are described in detail for ease of understanding and explanation of this disclosure, and this disclosure is not necessarily limited to having all the structures described. In addition, for some structures in each embodiment, other structures may be added, deleted, or replaced.

[0188] In addition, the above-mentioned mechanisms and structures only show the parts deemed necessary for the description and may not show all the mechanisms and structures on the product.

[0189] Symbol Explanation

[0190] 10. Conversion Circuit

[0191] 20 smoothing capacitor

[0192] 30 DC Voltage Detection Unit

[0193] 40, 40B Overvoltage Protection Circuit

[0194] 41 Switching elements

[0195] 42 Resistor element

[0196] 43 Capacitors

[0197] 50 Inverter Circuit

[0198] 60 Control Department

[0199] 61 Inverter Control Circuit

[0200] 62 Overvoltage Protection Control Circuit

[0201] 91 Compressor

[0202] 92 Outdoor heat exchanger

[0203] 93 Outdoor Fan

[0204] 94 Expansion Valve

[0205] 95 Four-way valve

[0206] 96 Indoor heat exchanger

[0207] 97 Indoor Fan

[0208] 100, 100A, 100B Power Conversion Devices

[0209] E1 AC power supply

[0210] M1 motor

[0211] S1, S3, S5 Switching Elements (Upper Arm)

[0212] S2, S4, S6 Switching Elements (Lower Arm)

[0213] W1 Air conditioner.

Claims

1. A power conversion device, characterized in that, have: A conversion circuit that converts the AC voltage applied from an AC power source into a DC voltage; A smoothing capacitor smooths the DC voltage on the output side of the conversion circuit; An inverter circuit that converts the DC voltage of the smoothing capacitor into an AC voltage and applies the AC voltage to the motor; An inverter control circuit that controls the inverter circuit; as well as An overvoltage protection circuit has a series connection of a switching element and a resistive element, which are connected in parallel with the smoothing capacitor. Furthermore, the power conversion device also includes an overvoltage protection control circuit, which, when the DC voltage of the smoothing capacitor reaches a predetermined value after the inverter circuit stops, performs overvoltage protection control to switch the switching element to the ON state. After the overvoltage protection control is initiated, the inverter control circuit performs a winding short-circuit control that connects all phases of one of the upper and lower arms of the inverter circuit while simultaneously disconnecting all phases of the other arm. The winding short-circuit control is initiated based on a specified state quantity, wherein the specified state quantity is correlated with the cumulative heat generated by the resistive element accompanying the overvoltage protection control.

2. The power conversion device according to claim 1, characterized in that, The specified state quantity is the elapsed time from the start of the overvoltage protection control.

3. The power conversion device according to claim 1, characterized in that, The specified state quantity is: after the overvoltage protection control starts, when the change in DC voltage changes from rising to a peak and then to falling, the amount of decrease from the peak value.

4. The power conversion device according to claim 1, characterized in that, The specified state quantity is: after the overvoltage protection control starts, when the change in DC voltage changes from rising to a peak and then to falling, the cumulative value of the decrease from the peak value.

5. The power conversion device according to claim 1, characterized in that, The specified state quantity is the magnitude of the current flowing through the resistive element after the overvoltage protection control is initiated.

6. The power conversion device according to claim 1, characterized in that, The specified state quantity is the cumulative value of the current flowing through the resistive element after the overvoltage protection control starts.

7. The power conversion device according to any one of claims 1 to 6, characterized in that, The faster the motor rotates when the inverter control circuit stops, the larger the threshold of the specified state quantity, which serves as the criterion for determining whether to start the winding short-circuit control, becomes.

8. The power conversion device according to any one of claims 1 to 6, characterized in that, Before the overvoltage protection control ends, the winding short-circuit control begins.

9. The power conversion device according to any one of claims 1 to 6, characterized in that, The overvoltage protection circuit includes a capacitor connected in parallel with the resistive element.

10. An air conditioner, characterized in that, have: The power conversion device according to any one of claims 1 to 6, Furthermore, the air conditioner also includes: a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger. The electric motor is the driving source for the compressor.

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