Power conversion device, motor drive device, and apparatus using refrigeration cycle

Abstract

A power conversion device (1) that performs power conversion comprises one or more switching devices that are included in at least one power converter among one or more power converters that perform power conversion, a waveform shape alteration unit (340) that can alter the waveform shape of a switching waveform of the switching devices, state quantity detection units (501–505) that detect a state quantity that indicates the operating state of the power conversion device (1), and a waveform shape setting unit (420) that sets the waveform shape of the switching waveform of the switching devices in accordance with the state quantity when the switching waveform of the switching devices is to be altered by the waveform shape alteration unit (340). The switching loss of the switching devices is equal to or greater than the conduction loss of the switching devices.

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device that performs power conversion, a motor drive device, and a refrigeration cycle application device.

[0002] A power conversion device includes one or more power converters that perform power conversion, and each power converter includes one or more switching devices. Hereinafter, for ease of explanation, "switching" will be abbreviated as "SW" where appropriate. A SW device is a semiconductor element that performs SW operation, and is also called a SW element. SW operation refers to the operation of a SW device switching between an OFF state with high resistance and an ON state with low resistance in a short time on the order of ns, μs, or ms.

[0003] The losses in SW devices are divided into SW losses and conduction losses, which are in a trade-off relationship. There is also a trade-off relationship between SW losses and the amount of noise that depends on the SW waveform of the SW device.

[0004] Against the above technical background, Patent Document 1 below discloses a technology for controlling the waveform shape of a SW waveform of a SW device by changing the amplitude of a gate voltage applied to a gate terminal of an FET (Field Effect Transistor).

[0005] Japanese Patent Application Laid-Open No. 2019-165596

[0006] Changing the waveform shape of the SW waveform of the SW device changes the operating point of the SW device, making it possible to arbitrarily manipulate the operating point in a trade-off between SW loss and noise. However, if conduction loss is dominant in the total loss, which is the sum of SW loss and conduction loss, even if the SW loss can be reduced by changing the waveform shape of the SW waveform, the effect on the reduction in total loss is small, and the effect of introducing a function to change the waveform shape of the SW waveform is insufficient.

[0007] The present disclosure has been made in view of the above, and aims to provide a power conversion device that can fully obtain the effect of introducing a function that changes the waveform shape of the SW waveform of a SW device.

[0008] In order to solve the above-mentioned problems and achieve the object, a power conversion apparatus according to the present disclosure is a power conversion apparatus that performs power conversion, and includes one or more SW devices, a waveform shape modification unit, a state quantity detection unit, and a waveform shape setting unit. The one or more SW devices are included in at least one power converter among one or more power converters that perform power conversion. The waveform shape modification unit is capable of modifying the waveform shape of the SW waveform of the SW device without physically switching a gate resistor. The state quantity detection unit detects a state quantity that indicates the operating state of the power conversion apparatus. The waveform shape setting unit sets the waveform shape of the SW waveform of the SW device when the waveform shape modification unit modifies the SW waveform of the SW device according to the state quantity. The SW loss of the SW device is equal to or greater than the conduction loss of the SW device.

[0009] The power conversion device according to the present disclosure has the effect of being able to fully obtain the effect of introducing a function for changing the waveform shape of the SW waveform of the SW device.

[0010] FIG. 5 shows the rectification boost portion of the converter provided in the power conversion apparatus according to the first embodiment.and turn-on voltage. Figure 1 shows an example of the relationship between noise and loss generated in a general SW device. Figure 2 shows an example of the relationship between noise and loss generated in a general SW device. Figure 3 shows an example of the relationship between noise and loss generated in a general SW device. Figure 4 shows an example of the relationship between noise and loss generated in a general SW device. Figure 5 shows an example of the relationship between noise and loss generated in a general SW device. Figure 6 shows an example of the relationship between noise and loss generated in a general SW device. FIG. 3 shows the relationship between gate voltages indicating the rate of rise. FIG. 4 shows an example of the relationship between the basic pulse output by the basic pulse generating unit and the gate current output by the waveform shape changing unit in the power conversion device according to embodiment 1. FIG. 5 shows a flowchart for explaining the operation of changing the waveform shape of the SW waveform of the SW device in the power conversion device according to embodiment 1. FIG. 6 shows an example of the operating state of the SW device in which the effect of introducing the waveform shape changing function adopted in the power conversion device according to embodiment 1 is not obtained. FIG. 7 shows an example of the operating state of the SW device in which the effect of introducing the waveform shape changing function adopted in the power conversion device according to embodiment 1 is obtained. FIG. 8 shows the points to note when introducing the waveform shape changing function according to embodiment 1 in relation to the load conditions of a product equipped with the power conversion device according to embodiment 1. FIG. 9 shows an example of the configuration of a power conversion device according to embodiment 2. FIG. 10 shows an example of the configuration of a power conversion device according to embodiment 3. FIG. 11 shows an example of the configuration of a refrigeration cycle application device according to embodiment 4.

[0011] Hereinafter, a power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] First Embodiment. FIG. 1 is a diagram illustrating an example of the configuration of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts first AC power of a power supply voltage supplied from the commercial power supply 110 into second AC power having a desired amplitude and phase, and supplies the second AC power to the motor 314. In the example of FIG. 1, the commercial power supply 110 is a single-phase AC power supply, but it may also be a three-phase AC power supply. The power conversion device 1 includes state quantity detection units 501 to 505, a converter 130, a capacitor 210, an inverter 310, and a control unit 400. However, as will be described later, the power conversion device 1 does not need to include all of the state quantity detection units 501 to 505. The power conversion device 1 and the motor 314 form a motor drive device 2.

[0013] The state quantity detection unit 501 detects a state quantity that indicates the operating state of the power conversion device 1. The state quantity detection unit 501 detects, for example, the voltage value of the AC power supplied from the commercial power supply 110 to the converter 130, the current value of the AC power supplied from the commercial power supply 110 to the converter 130, etc.

[0014] The converter 130 is a power converter that converts AC power of a power supply voltage supplied from the commercial power supply 110 into DC power. The converter 130 includes rectifying elements 131 to 134, a reactor 135, a SW device 136, a freewheeling diode 137, a diode 138, and a drive circuit 150. The converter 130 has a bridge circuit formed by the rectifying elements 131 to 134, rectifies first AC power of the power supply voltage supplied from the commercial power supply 110, and boosts and outputs the rectified DC power. The drive circuit 150 generates a drive signal for actually driving the SW device 136 based on a basic pulse generated by a basic pulse generating unit 410 of the control unit 400, which will be described later. The SW device 136 may be, for example, an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), or a bipolar transistor, but is not limited to these.

[0015] In the example of FIG. 1 , converter 130 includes rectifier unit 161 of a bridge circuit configured with rectifier elements 131 to 134, and boost unit 162 configured with reactor 135, SW device 136, freewheel diode 137, and diode 138. However, the configuration of converter 130 is not limited to the example of FIG. 1 . FIG. 2 is a first diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 3 is a second diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 4 is a third diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 5 is a fourth diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1. FIG. 6 is a fifth diagram showing the rectifying and boosting portion of converter 130 included in power conversion device 1 according to embodiment 1.

[0016] As shown in FIG. 2, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, SW devices 136a and 136b, freewheel diodes 137a and 137b, and rectifier elements 133 and 134. The rectifier / boost unit 163 shown in FIG. 2 is a totem-pole bridgeless circuit. Alternatively, as shown in FIG. 3, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, SW devices 136b and 136d, freewheel diodes 137b and 137d, and rectifier elements 131 and 133. The rectifier / boost unit 163 shown in FIG. 3 is a half-bridgeless circuit. Alternatively, as shown in FIG. 4, the converter 130 may be configured to include a rectifier / boost unit 163 including a reactor 135, SW devices 136a to 136d, and freewheel diodes 137a to 137d. The rectifying / boosting unit 163 shown in FIG. 4 is a full-bridgeless circuit. Alternatively, as shown in FIG. 5, the converter 130 may include a rectifying unit 161 including rectifying elements 131 to 134 and a boosting unit 162 including reactors 135a and 135b, SW devices 136a and 136b, freewheeling diodes 137a and 137b, and diodes 138a and 138b. The boosting unit 162 shown in FIG. 5 is an interleaved circuit. Alternatively, as shown in FIG. 6, the converter 130 may include a rectifying / boosting unit 163 including a reactor 135, a first rectifying circuit including rectifying elements 131 to 134, and a second rectifying circuit including the SW device 136, the freewheeling diode 137, and rectifying elements 131a to 134a. The rectifying and boosting unit 163 shown in Figure 6 is a simple PAM (Pulse Amplitude Modulation) type circuit in which a first rectifying circuit and a second rectifying circuit are connected in parallel, an SW device 136 is connected to the output terminal of the first rectifying circuit, and a capacitor 210 that supplies a second DC voltage to an inverter 310 is connected to the output terminal of the second rectifying circuit.

[0017] As described above, the converter 130 includes a rectifier 161 that converts a first AC voltage supplied from the commercial power supply 110 into a first DC voltage, a booster 162 that boosts the first DC voltage to a second DC voltage greater than the first DC voltage, or a rectifier / booster 163 that rectifies the first AC voltage and boosts it to a second DC voltage having an effective value greater than the effective value of the first AC voltage. Note that, when the commercial power supply 110 is a three-phase AC power supply, the converter 130 includes at least six elements, such as rectifiers and SW devices. In this case, the power conversion device 1 may be a three-phase three-wire power conversion device or a three-phase four-wire power conversion device. In this document, the converter 130 only needs to have a rectification function and does not necessarily need to have a boost function. The following description will be given using the power conversion device 1 having the configuration shown in FIG. 1 as an example.

[0018] Capacitor 210 is connected to the output terminal of converter 130 and smoothes the DC power converted by converter 130. Capacitor 210 is, for example, an electrolytic capacitor or a film capacitor.

[0019] The state quantity detection unit 502 detects a state quantity that indicates the operating state of the power conversion device 1. The state quantity detection unit 502 detects, for example, the voltage value of the DC power supplied from the capacitor 210 to the inverter 310.

[0020] The inverter 310 is a power converter connected to both ends of the capacitor 210. The inverter 310 has SW devices 311a to 311f and freewheeling diodes 312a to 312f. The inverter 310 turns on and off the SW devices 311a to 311f under the control of the control unit 400, converts the power output from the converter 130 and the capacitor 210 into second AC power having a desired amplitude and phase, that is, generates the second AC power, and outputs it to the motor 314. The SW devices 311a to 311f are, for example, IGBTs, MOSFETs, bipolar transistors, etc., but are not limited to these. The circuit configuration of the inverter 310 is not particularly limited and may be a full-bridge circuit, a single-phase bridge circuit, a half-bridge circuit, etc.

[0021] The inverter 310 also includes a waveform shape modification unit 340 that can modify the waveform shapes of the SW waveforms of the SW devices 311a to 311f, and the waveform shape modification unit 340 includes a storage unit 360. The function and operation of the waveform shape modification unit 340 will be described later.

[0022] The state quantity detection unit 503 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 503 detects, for example, a voltage value of the second AC power supplied from the inverter 310 to the motor 314 which is a load, a current value of the second AC power supplied from the inverter 310 to the motor 314 which is a load, etc. The state quantity detection unit 504 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 504 detects, for example, a current value of the DC power supplied from the capacitor 210 to the inverter 310, etc. The state quantity detection unit 505 detects a state quantity indicating the operating state of the power conversion device 1. The state quantity detection unit 505 detects, for example, a current flowing through the SW devices 311b, 311d, 311f, etc.

[0023] The control unit 400 acquires the state quantities detected by the state quantity detection units 501 to 505 from the state quantity detection units 501 to 505, and controls the operations of the converter 130 and the inverter 310 based on the acquired state quantities, specifically, controls the on / off of the SW device 136 of the converter 130, and controls the on / off of the SW devices 311a to 311f of the inverter 310. The control unit 400 includes a basic pulse generation unit 410 and a waveform shape setting unit 420.

[0024] The basic pulse generation unit 410 has a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505 and generates a basic pulse for controlling the operation of the SW device 136 of the converter 130. The basic pulse generation unit 410 also has a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505 and generates a basic pulse for controlling the operation of the SW devices 311a to 311f of the inverter 310. The basic pulse is, for example, a PWM (Pulse Width Modulation) signal having a duty ratio corresponding to the state quantities detected by the state quantity detection units 501 to 505. The basic pulse generation unit 410 outputs a basic pulse for controlling the operation of the SW device 136 of the converter 130 to the converter 130 and outputs a basic pulse for controlling the operation of the SW devices 311a to 311f of the inverter 310 to the waveform shape setting unit 420.

[0025] The waveform shape setting unit 420 sets the waveform shapes of the SW waveforms of the SW devices 311a to 311f when the waveform shape changing unit 340 of the inverter 310 changes the SW waveforms of the SW devices 311a to 311f in accordance with the state quantities detected by the state quantity detection units 501 to 505, and outputs a control signal for reflecting a setting value indicating the set waveform shape. Specifically, when the SW devices 311a to 311f are turned on and off based on the basic pulses for controlling the operation of the SW devices 311a to 311f of the inverter 310 generated by the basic pulse generation unit 410, the waveform shape setting unit 420 controls the magnitude of the drive signals that the waveform shape changing unit 340 of the inverter 310 outputs to the SW devices 311a to 311f to actually drive the SW devices 311a to 311f, and the timing at which the drive signals are output. The waveform shape setting unit 420 outputs a control signal for controlling the operation of the waveform shape changing unit 340 to the waveform shape changing unit 340. In the case where the inverter 310 has a waveform shape modification unit 340 for each of the SW devices 311a to 311f, i.e., six waveform shape modification units 340, the control unit 400 may be configured to have a waveform shape setting unit 420 for each waveform shape modification unit 340, i.e., six waveform shape setting units 420.

[0026] In the example of FIG. 1 , the control unit 400 acquires state quantities detected by the state quantity detection units 501 to 505 from the state quantity detection units 501 to 505 and controls the operation of the converter 130 and the inverter 310 based on the acquired state quantities, but this is not limited to this. The control unit 400 can control the operation of the converter 130 and the inverter 310 based on the state quantities acquired from at least one of the state quantity detection units 501 to 505. In the power conversion device 1, the state quantity detection units 501 to 505 detect, as state quantities, voltages or currents input to each component of the power conversion device 1, voltages or currents output from each component of the power conversion device 1, etc., but the detection targets are not limited to these. The detection targets may be the frequency of the voltage input to or output from each component of the power conversion device 1, the modulation factor of the voltage input to each component of the power conversion device 1, or the voltage or current of the SW devices 311a to 311f. Alternatively, the detection target may be a command value determined by the control unit 400 of the power conversion device 1 .

[0027] Furthermore, the installation positions of the state quantity detection units 501 to 505 are not limited to the example in Figure 1. The power conversion device 1 does not need to have all of the state quantity detection units 501 to 505 arranged as shown in Figure 1. The power conversion device 1 may have the state quantity detection units at any position other than that shown in the figure as long as the state quantities can be detected. The power conversion device 1 may have state quantity detection units at positions where they can detect state quantities such as noise generated by the power conversion device 1, the motor 314, etc., losses generated by the power conversion device 1, the motor 314, etc., and the temperature of each component included in the power conversion device 1, the motor 314, etc.

[0028] Furthermore, since the basic pulse generating unit 410 and the waveform shape setting unit 420 both operate based on the state quantities acquired from the state quantity detecting units 501 to 505, the control unit 400 may combine the functions of the basic pulse generating unit 410 and the waveform shape setting unit 420 into a single configuration.

[0029] The motor 314 is a load connected to the power conversion device 1. The motor 314 is, for example, a compressor motor for driving a compressor. The motor 314 rotates in accordance with the amplitude and phase of the second AC power supplied from the inverter 310 to perform compression. For example, when the compressor is a hermetic compressor, the load torque of the motor 314 driving the compressor can often be considered a constant torque load. The motor 314 may have a Y-connection, a Δ-connection, or a specification that allows switching between the Y-connection and the Δ-connection, with respect to the motor windings (not shown). Furthermore, the load connected to the power conversion device 1, i.e., the inverter 310, is not limited to the motor 314 for driving the compressor and may be a fan motor or the like. Furthermore, the load connected to the power conversion device 1 is not limited to the motor 314 and may be a load other than the motor 314.

[0030] In the first embodiment, the power conversion device 1 can change the waveform shapes of the SW waveforms of the SW devices 311a to 311f of the inverter 310 by the waveform shape setting unit 420 and the waveform shape changing unit 340. Specifically, the power conversion device 1 can change the SW speeds, delay times, etc. of the SW devices 311a to 311f of the inverter 310.

[0031] Fig. 7 is a diagram illustrating an example of a hardware configuration that realizes the control unit 400 included in the power conversion device 1 according to embodiment 1. The above-described functions and later-described functions of the control unit 400 can be realized by a processor 91 and a memory 92 as shown in Fig. 7 .

[0032] The processor 91 is a CPU (Central Processing Unit, also referred to as a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Examples of the memory 92 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). The memory 92 is not limited to these, and may also be a magnetic disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0033] The memory 92 stores a program that executes the functions of the control unit 400. The processor 91 exchanges necessary information via an interface including an analog-to-digital converter and a digital-to-analog converter (not shown), and executes the program stored in the memory 92 to perform required processing. The results of calculations by the processor 91 can be stored in the memory 92.

[0034] FIG. 8 is a diagram showing examples of turn-on joule loss, turn-on current, and turn-on voltage when the SW speed of the SW devices 311a to 311f of the inverter 310 in the power conversion apparatus 1 according to the first embodiment is slowed. FIG. 9 is a diagram showing examples of turn-on joule loss, turn-on current, and turn-on voltage when the SW speed of the SW devices 311a to 311f of the inverter 310 in the power conversion apparatus 1 according to the first embodiment is increased. In FIGS. 8 and 9 , A represents turn-on joule loss, B represents turn-on current, and C represents turn-on voltage. In FIGS. 8 and 9 , the horizontal axis represents time. For example, the turn-on current is the current flowing through the SW device 311a, the turn-on voltage is the voltage applied across the SW device 311a, and the turn-on joule loss is the product of the turn-on current and the turn-on voltage. However, the measurement target is not limited to the SW device 311a, and may be the other SW devices 311b to 311f. 8 and 9 show the differences in characteristics depending on the SW speed of the SW devices 311a to 311f of the inverter 310, and the specific numerical values ​​of "slow" and "fast" SW speeds are not particularly important. As shown in FIGS. 8 and 9, slowing the SW speed reduces noise represented by the peak value of the turn-on current of B, but increases loss represented by the area of ​​the turn-on joule loss of A. Also, as shown in FIGS. 8 and 9, increasing the SW speed increases noise represented by the peak value of the turn-on current of B, but decreases loss represented by the area of ​​the turn-on joule loss of A. In other words, there is a trade-off between the noise and loss generated in the SW devices 311a to 311f.

[0035] 8 and 9, the turn-on joule loss that occurs when the SW devices 311a to 311f are turned on is described, but a loss also occurs when the SW devices 311a to 311f are turned off. This loss is called "turn-off joule loss." In this paper, the turn-on joule loss and turn-off joule loss are collectively called "SW loss."

[0036] In the power conversion device 1, the waveform shape modification unit 340 is configured by a digital gate driver. Alternatively, in the power conversion device 1, the SW devices 311a to 311f of the inverter 310 and the waveform shape modification unit 340 are configured by a digital gate driver module. This allows the power conversion device 1 to change the SW speeds of the SW devices 311a to 311f of the inverter 310 by changing software command values ​​without changing the hardware, and to control the noise and SW loss generated in the SW devices 311a to 311f to desired states.

[0037] 10 is a diagram showing an example of the relationship between noise generated in a typical SW device and SW loss. As described above, there is a trade-off between noise generated in a SW device and SW loss. Therefore, in a typical SW device, as shown in FIG. 10, increasing the SW speed increases noise but decreases SW loss, and slowing the SW speed decreases noise but increases SW loss.

[0038] FIG. 11 is a first diagram illustrating the effect obtained by changing the SW speed of the SW devices 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment. Even if the power conversion device 1 is operating within the noise range specified for the product in which the power conversion device 1 is installed, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and SW loss generated by the SW devices 311a to 311f shifts upward to the upper right as shown in FIG. 11, resulting in an increase in noise. In other words, in the power conversion device 1, the heavier the load, the greater the noise. Therefore, the power conversion device 1 can reduce the noise generated by the SW devices 311a to 311f by slowing down the SW speed of the SW devices 311a to 311f. Similarly, even if the power conversion device 1 is operating within the loss range specified for the product in which the power conversion device 1 is installed, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and SW loss generated in the SW devices 311a to 311f shifts to the upper right as shown in Figure 11, resulting in an increase in SW loss. That is, in the power conversion device 1, the heavier the load, the greater the SW loss. Therefore, the power conversion device 1 can reduce the SW loss generated in the SW devices 311a to 311f by increasing the SW speed of the SW devices 311a to 311f.

[0039] When the load state of the motor 314 changes from a light load to a heavy load, the waveform shape setting unit 420 changes the waveform shapes of the SW waveforms of the SW devices 311a to 311f so as to reduce SW losses generated in the SW devices 311a to 311f while ensuring that noise generated in the SW devices 311a to 311f satisfies specified requirements. Alternatively, when the load state of the motor 314 changes from a light load to a heavy load, the waveform shape setting unit 420 changes the waveform shapes of the SW waveforms of the SW devices 311a to 311f so as to reduce noise generated in the SW devices 311a to 311f while ensuring that losses generated in the SW devices 311a to 311f satisfy specified requirements.

[0040] 12 is a second diagram illustrating the effect obtained by changing the SW speeds of the SW devices 311a to 311f of the inverter 310 in the power conversion device 1 according to the first embodiment. The power conversion device 1, specifically the waveform shape modification unit 340, divides, for example, the turn-on period or the turn-off period in one SW operation of the SW devices 311a to 311f into two or more periods, and modifies the amplitude of the gate current or gate voltage for the SW devices 311a to 311f to different magnitudes in each of the divided periods. By optimizing the SW waveforms of the SW devices 311a to 311f as shown in FIG. 12, the power conversion device 1 can obtain characteristics of noise and SW loss generated by the SW devices 311a to 311f that could not be obtained with a typical SW device such as that shown in FIG. 10.

[0041] Next, the configuration of the waveform shape modification unit 340 will be described. Here, for simplicity of explanation, as an example, a case will be described in which the waveform shape modification unit 340 is capable of modifying the waveform shape of the SW waveform of one SW device 311a. Fig. 13 is a diagram showing an example of the configuration of the waveform shape modification unit 340 provided in the inverter 310 of the power conversion device 1 according to the first embodiment. Fig. 13 is also a diagram showing an example of the configuration of one digital gate driver module formed by the waveform shape modification unit 340 and the SW device 311a.

[0042] 1, the waveform shape modification unit 340 is included in the inverter 310, which is a power converter including the SW device 311a. The waveform shape modification unit 340 includes n P-channel MOSFETs (PMOSs) as turn-on transistors, n PreDrivers for operating the n PMOSs, n N-channel MOSFETs (NMOSs) as turn-off transistors, and n PreDrivers for operating the n NMOSs.

[0043] The waveform shape changing unit 340 is connected to a control power supply Vdd and a ground GND. The waveform shape changing unit 340 changes the number of PMOS or NMOS to be operated based on a control signal from the waveform shape setting unit 420, thereby changing the gate current I, which is a drive signal to be output to the SW device 311a, during each of the turn-on period and the turn-off period. Ｇ The amplitude value of the signal can be changed in n ways to adjust the SW speed of the SW device 311a.

[0044] The waveform shape changing unit 340 increases the number of PMOS or NMOS to be operated, and the gate current I output to the SW device 311a Ｇ The absolute value of the gate current I can be increased, and the SW speed of the SW device 311a can be increased. In addition, the waveform shape changing unit 340 can adjust the SW speed of the SW device 311a more precisely as the number of PMOS and NMOS included therein increases. Ｇ The faster the response of the increase or decrease of the gate current I Ｇ The control signal to the waveform shape modification unit 340 may be an analog signal or a digital signal as long as it can change the number of PMOS or NMOS to be operated by the waveform shape modification unit 340.

[0045] 13 shows that there are m parallel control signals to the waveform shape modification unit 340, but this is just an example and the number of control signals is not limited to m. The number of control signals may be any number that can indicate whether each PMOS and each NMOS is operational or not, or it may be one if it is an analog signal that indicates a voltage or the like.

[0046] FIG. 14 shows the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the SW device 311a. Ｇ 15 is a first diagram showing the relationship between the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the SW device 311a. Ｇ14 and 15, the waveform shape changing unit 340 changes the gate current I Ｇ The larger the gate voltage V Ｇ 14 and 15, the waveform shape changing unit 340 can increase the rise time of the output gate current I Ｇ The smaller the gate voltage V Ｇ 11, the power conversion device 1 can output a gate current I when it is desired to reduce noise generated in the SW device 311a. Ｇ When it is desired to reduce the SW speed by decreasing the value of the gate current I Ｇ The SW speed can be increased by increasing the gate current I Ｇ and gate voltage V Ｇ The waveform of the gate current I is an ideal example, and in reality, as shown in FIGS. Ｇ It takes time for the current to reach a constant value.

[0047] FIG. 16 shows the gate current I output by the waveform shape modification unit 340 in the power conversion device 1 according to the first embodiment. Ｇ and the gate voltage V, which indicates the rise speed of the SW device 311a. Ｇ 16, the waveform shape changing unit 340 divides the turn-on period and changes the gate current I Ｇ That is, the waveform shape changing unit 340 can change the magnitude of the gate current I Ｇ This allows the power conversion device 1 to finely adjust the magnitude of the gate current I Ｇ 12, it is possible to perform control so as to reduce the loss generated in the SW device 311a while reducing the noise generated in the SW device 311a.

[0048] Although the turn-on period of the SW device 311a has been described as an example in FIGS. 14 to 16, the same applies to the turn-off period of the SW device 311a.

[0049] FIG. 17 shows the basic pulse output by the basic pulse generating unit 410 and the gate current I output by the waveform shape changing unit 340 in the power conversion device 1 according to the first embodiment. Ｇ 17 is a diagram illustrating an example of the relationship between |Ig2| and |Ig1|. In FIG. 17, |Ig2|>|Ig1|. The waveform shape changing unit 340 changes the gate current I Ｇ The period during which the current Ig2 having the larger amplitude is output is divided, and the gate current I Ｇ Then, the gate current I of the current Ig1 with the next smallest amplitude is output. Ｇ Alternatively, the gate current I of the current Ig1 with the small amplitude may be output first. Ｇ After outputting the gate current I of the current Ig2 with the next largest amplitude, Ｇ Similarly, the waveform shape changing section 340 may output the gate current I Ｇ The period during which the current with the largest amplitude is output is divided, and first, the gate current I Ｇ Then, the gate current I of the next smallest amplitude current -Ig1 is output. Ｇ Alternatively, the gate current I of the current −Ig1 with a small amplitude may be output first. Ｇ After outputting the next largest current, the gate current Ig2 Ｇ may be output.

[0050] As described above, the waveform shape changing unit 340 divides at least one of the turn-on period and the turn-off period of the SW device 311a into two or more periods based on the control signal output from the waveform shape setting unit 420, and determines the gate current I for the SW device 311a in each divided period. Ｇ The waveform shape changing section 340 includes a plurality of transistors, and by changing the number of transistors to be operated, the amplitude of the gate current I Ｇ The amplitude of can be changed.

[0051] Furthermore, the waveform shape changing unit 340 changes the gate current I Ｇ The waveform shape changing unit 340 can change the SW waveform to a different waveform shape for each SW cycle of the SW device 311a during operation of the power conversion device 1. In this case, the waveform shape setting unit 420 can change the set value of the waveform shape of the SW waveform of the SW device 311a at the same cycle as the SW cycle of the SW device 311a. The waveform shape setting unit 420 may also change the set value of the waveform shape of the SW waveform of the SW device 311a at a cycle that is a positive integer multiple of the SW cycle of the SW device 311a.

[0052] 13 is merely an example and is not intended to be limiting. In this manner, the waveform shape modification unit 340 can more precisely adjust the SW speed of the SW device 311a by digital control using a plurality of MOS transistors, compared to analog control that physically switches gate resistors as described in Patent Document 1. Furthermore, the waveform shape modification unit 340 may use transistors other than MOS transistors for its internal transistors.

[0053] In the above example, the waveform shape changing unit 340 changes the number of PMOS or NMOS to be operated in accordance with the acquired control signal, and generates a gate current I Ｇ to the SW device 311a, but is not limited to this. Ｇ The output pattern, i.e., waveform shape, of the gate current I is stored in advance, and the output pattern, i.e., waveform shape, corresponding to the acquired control signal is Ｇ The waveform shape changing unit 340 may output a previously acquired control signal and a gate current I Ｇ The output pattern, i.e., waveform shape, of the gate current I is stored, and when the same control signal is acquired, the stored output pattern, i.e., waveform shape is used. Ｇ The waveform shape changing section 340 may output the gate current IＧ By storing the output pattern, i.e., waveform shape, of the gate current I Ｇ This reduces the processing load when outputting.

[0054] In the example of FIG. 13, the waveform shape changing unit 340 outputs the gate current I Ｇ The waveform shape changing unit 340 adjusts the SW speed of the SW device 311a by changing the gate voltage V Ｇ and the gate voltage V Ｇ By changing the value of the SW waveform of the SW device 311a, the SW speed of the SW device 311a can be adjusted and the waveform shape of the SW waveform of the SW device 311a can be changed.

[0055] In this way, the waveform shape changing unit 340 divides at least one of the turn-on period and the turn-off period of the SW device 311a into two or more periods based on the control signal output from the waveform shape setting unit 420, and sets the gate voltage V Ｇ The waveform shape changing section 340 includes a plurality of transistors, and by changing the number of transistors to be operated based on the control signal output from the waveform shape setting section 420, the amplitude of the gate voltage V Ｇ The amplitude of can be changed.

[0056] 18 is a flowchart illustrating an operation for changing the waveform shape of the SW waveforms of the SW devices 311a to 311f in the power conversion device 1 according to the first embodiment. In the power conversion device 1, the basic pulse generation unit 410 generates a basic pulse for driving the SW devices 311a to 311f of the inverter 310 based on the state quantities acquired from the state quantity detection units 501 to 505 (step S1). As described above, in the control unit 400, the basic pulse generation unit 410 generates a basic pulse based on the state quantities acquired from the state quantity detection units 501 to 505, and determines the timings for turning on and off the SW devices 311a to 311f. The basic pulse generation unit 410 outputs the generated basic pulse to the waveform shape setting unit 420.

[0057] The waveform shape setting unit 420 sets a waveform shape for changing the waveform shape of the SW waveform of the SW devices 311a to 311f of the inverter 310, based on the basic pulse obtained from the basic pulse generating unit 410 and the state quantities obtained from the state quantity detecting units 501 to 505. In this way, in the control unit 400, the waveform shape setting unit 420 sets the waveform shapes of the SW waveforms at the timings for turning on and turning off the SW devices 311a to 311f determined by the basic pulse generating unit 410, based on the state quantities obtained from the state quantity detecting units 501 to 505. The waveform shape setting unit 420 outputs a control signal to the waveform shape changing unit 340, which can change the magnitude and output timing of the drive signal in accordance with the set waveform shape, i.e., the set value of the waveform shape (step S2).

[0058] The waveform shape changing unit 340 changes the gate current I Ｇ The waveform shape of the gate current I after the waveform shape change is performed is changed based on the control signal obtained from the waveform shape setting unit 420 (step S3). Ｇ are output to the SW devices 311a to 311f of the inverter 310.

[0059] Next, a description will be given of the main parts of the embodiment 1. In the following description, the function for changing the waveform shape of the SW waveform will be referred to as the "waveform shape changing function."

[0060] Fig. 19 is a diagram showing an example of an operating state of a SW device in which the effect of introducing the waveform shape modification function employed in the power conversion device 1 according to embodiment 1 is not obtained. Also, Fig. 20 is a diagram showing an example of an operating state of a SW device in which the effect of introducing the waveform shape modification function employed in the power conversion device 1 according to embodiment 1 is obtained. Note that in Figs. 19 and 20, the heights of the bar graphs representing the loss and the amount of noise do not mean strict values, but are shown so that the magnitude relationship of each loss and amount of noise can be compared between operating states.

[0061] FIG. 19 shows three operating states of a certain SW device A. The operating state (a1) on the left shows the magnitude relationship between SW loss, conduction loss, and noise when SW device A is operated under reference conditions. In operating state (a1), the relationship SW loss < conduction loss is shown. The operating state (a2) in the center shows the operating state when the SW waveform for SW device A is set to the steepest, and the operating state (a3) ​​on the right shows the operating state when the SW waveform for SW device A is set to the gentlest. Here, the case where the SW waveform is set to the steepest assumes the case where the functionality of the waveform shape modification unit 340 is fully utilized. For example, in the configuration of the waveform shape modification unit 340 shown in FIG. 13, this corresponds to the case where all n PMOS or NMOS transistors are used. Furthermore, the case where the SW waveform is set to the gentlest assumes the case where the functionality of the waveform shape modification unit 340 is fully utilized. For example, in the configuration of the waveform shape modifying section 340 shown in FIG. 13, this corresponds to the case where either one of n PMOS or NMOS is used.

[0062] In the case of SW device A having the characteristics shown in FIG. 19, the effect on the reduction in total loss, which is the sum of SW loss and conduction loss, is small, and it can be seen that the effect of introducing the waveform shape modification function is not sufficient.

[0063] Next, the operating states of FIG. 20 will be described. On the left side of FIG. 20, the operating state (a1) shown on the left side of FIG. 19 is shown as a reference for comparison. Furthermore, the three operating states (b1) to (b3) shown from the center to the right side of FIG. 20 are operating states when SW device B, which is different from SW device A, is operated. The operating state (b1) shown on the left side of the center is the operating state when SW device B is driven under the same conditions as on the left side, the operating state (b2) shown on the right side of the center is the operating state when the SW waveform for SW device B is made the steepest, and the operating state (b3) shown on the right side is the operating state when the SW waveform for SW device B is made the gentlest.

[0064] When SW device B having the characteristics shown in FIG. 20 is used, the SW loss changes significantly between when the SW waveform is set to the steepest and when the SW waveform is set to the gentlest. Therefore, by using SW device B and implementing the waveform shape modification function described in embodiment 1, it is possible to fully obtain the benefits of implementing the waveform shape modification function. Furthermore, when SW device B having the characteristics shown in FIG. 20 is used, it is possible to reduce the amount of noise while maintaining the total loss of SW loss and conduction loss at the same level, as can be seen from a comparison between the bar graph (a1) on the left side of FIG. 20 and the bar graph (b1) on the center left side. Therefore, it can be seen that using SW device B also provides a noise reduction effect.

[0065] In a SW device, for example, increasing the chip area increases the input capacitance and parasitic capacitance. Therefore, when compared under the same operating conditions, the larger the chip area, the greater the SW loss. Therefore, if a SW device is designed using the chip area as a parameter, a SW device B with the characteristics shown in FIG. 20 can be obtained. Note that the chip area described here is an example of a design parameter, and SW device B may be designed using other parameters related to the magnitude of SW loss, or SW device B may be designed using both the chip area and other parameters.

[0066] 21 is a diagram showing considerations when introducing the waveform shape changing function according to embodiment 1 in relation to the load conditions of a product equipped with the power conversion device 1 according to embodiment 1. An air conditioner is assumed as a product equipped with the power conversion device 1, but the product is not limited to an air conditioner.

[0067] The left side of Figure 21 shows bar graphs of SW loss, conduction loss, and noise when the load condition of a product equipped with the power conversion device 1 is an intermediate load, while the right side of Figure 21 shows bar graphs of SW loss, conduction loss, and noise when the load condition of a product equipped with the power conversion device 1 is a rated load. For simplicity of explanation, the rated load in Figure 21 assumes a state in which the product equipped with the power conversion device 1 is operating near the rated power. If the product equipped with the power conversion device 1 is an air conditioner, the load conditions called cooling rated and heating rated correspond to the rated load. Furthermore, the intermediate load in Figure 21 assumes a state in which the product equipped with the power conversion device 1 is operating near half the rated power. If the product equipped with the power conversion device 1 is an air conditioner, the load conditions called cooling intermediate and heating intermediate correspond to the intermediate load.

[0068] 21, the upper part shows the operating state when the waveform shape modification unit 340 makes the SW waveform the steepest, and the lower part shows the operating state when the waveform shape modification unit 340 makes the SW waveform the gentlest. The term "steepest SW waveform" does not necessarily mean that the function of the waveform shape modification unit 340 is maximized to make the SW waveform the steepest, but rather means that the SW waveform is the steepest within the range in which the function of the waveform shape modification unit 340 is limited to match the load conditions. Similarly, the term "gentlest SW waveform" does not necessarily mean that the function of the waveform shape modification unit 340 is minimized to make the SW waveform the gentlest, but rather means that the SW waveform is the gentlest within the range in which the function of the waveform shape modification unit 340 is limited to match the load conditions.

[0069] 21 , the numerical values ​​shown on the left or right of each bar graph represent the approximate magnitudes of the SW loss, conduction loss, and noise amount, expressed as a ratio, with the upper left bar graph's magnitude being set to a reference value of 1. Using these ratios clarifies the design guidelines for SW device B and the design guidelines for waveform shape modification unit 340 used in embodiment 1. For example, if the configuration of waveform shape modification unit 340 is determined first, SW device B can be designed so that the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform steepest is equal to or greater than the conduction loss of the SW device. Conversely, if the design of SW device B is determined first, the configuration of waveform shape modification unit 340 can be determined so that the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform steepest is equal to or greater than the conduction loss of the SW device. Designing SW device B and waveform shape modification unit 340 according to these guidelines makes it possible to fully realize the benefits of introducing a waveform shape modification function to the SW device.

[0070] Furthermore, for example, if the configuration of waveform shape modification unit 340 is determined first, SW device B can be designed so that the difference between the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform most gentle and the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform most steep is equal to or greater than the conduction loss of the SW device. Conversely, if the design of SW device B is determined first, the configuration of waveform shape modification unit 340 can be determined so that the difference between the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform most gentle and the SW loss of SW device B when the waveform shape modification unit 340 makes the SW waveform most steep is equal to or greater than the conduction loss of the SW device. Designing SW device B and waveform shape modification unit 340 according to these guidelines makes it possible to fully obtain the benefits of introducing a waveform shape modification function to the SW devices.

[0071] The operating state at the bottom left of Fig. 21 has a smaller amount of noise but a larger SW loss than the operating state at the top left of Fig. 21. When the load condition of a product incorporating the power conversion device 1 is an intermediate load, emphasis is placed on efficiency. For this reason, the waveform shape setting unit 420 emphasizes efficiency and sets the SW waveform to be as steep as possible. In particular, when a product incorporating the power conversion device 1 is operating at half the rated power, the waveform shape setting unit 420 sets the SW waveform to be as steep as possible.

[0072] Furthermore, when the load condition of a product equipped with the power conversion device 1 is changed from an intermediate load to a rated load, the operating state transitions from the upper left to the upper right in FIG. 21 . The operating state in the upper right of FIG. 21 has a larger amount of noise than the operating state in the lower right of FIG. 21 , and depending on the amount of noise, it may become an unacceptable operating state. Therefore, when the load condition of a product equipped with the power conversion device 1 is a rated load, the waveform shape setting unit 420 sets the SW waveform so that its shape becomes gentler until the amount of noise falls within an allowable range. Furthermore, when a product equipped with the power conversion device 1 is operated at rated power, the waveform shape setting unit 420 may set the SW waveform so that its shape becomes steepest within the allowable range of noise. This setting enables operation within the specified allowable range of noise while suppressing an increase in SW loss. Furthermore, when a product equipped with the power conversion device 1 is operated at rated power, the waveform shape setting unit 420 may set the SW waveform so that its shape becomes gentlest. This setting maximizes the suppression of noise generation.

[0073] As described above, the power conversion apparatus according to the first embodiment includes a waveform shape modification unit that can modify the waveform shape of the SW waveform of the SW device without physically switching the gate resistor, a state quantity detection unit that detects a state quantity indicating the operating state of the power conversion apparatus, and a waveform shape setting unit that sets the waveform shape of the SW waveform of the SW device when the waveform shape modification unit modifies the SW waveform of the SW device in accordance with the state quantity. Among the one or more power converters that perform power conversion, one or more SW devices included in an inverter are configured so that, when the SW device is operating, SW loss is equal to or greater than conduction loss. By using a power conversion apparatus configured in this manner, the functions of the waveform shape setting unit and the waveform shape modification unit can increase the SW loss control range, thereby enabling the full benefit of introducing a waveform shape modification function for the SW device.

[0074] Embodiment 2. In the first embodiment, a case has been described in which the waveform shape of the SW waveform of the SW devices 311a to 311f of the inverter 310 is changed in the power conversion device 1. In the second embodiment, a case has been described in which the waveform shape of the SW waveform of the SW device 136 of the converter 130 is changed in the power conversion device 1. In the second embodiment, the SW device 136 of the converter 130 is configured to have the characteristics shown in Fig. 20, and the waveform shape change function described in the first embodiment is applied to the converter 130.

[0075] 22 is a diagram showing an example of the configuration of a power conversion device 1 according to embodiment 2. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage of a power supply voltage supplied from the commercial power supply 110, which is an AC power supply, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. The power conversion device 1 includes a state quantity detection unit 501, a converter 130, a capacitor 210, a state quantity detection unit 502, an inverter 310, a state quantity detection unit 503, a state quantity detection unit 504, a state quantity detection unit 505, and a control unit 400. The power conversion device 1 and the motor 314 form a motor drive device 2.

[0076] The power conversion device 1 of the second embodiment shown in FIG. 22 is configured by removing the waveform shape modification unit 340 from the inverter 310 and adding a drive circuit 350 to the power conversion device 1 of the first embodiment shown in FIG. 1 , and removing the drive circuit 150 from the converter 130 and adding a waveform shape modification unit 140 to the converter 130. The waveform shape modification unit 140 also includes a storage unit 160. Furthermore, the power conversion device 1 of the second embodiment shown in FIG. 22 has output destinations of the basic pulse generation unit 410 and the waveform shape setting unit 420 changed from those of the power conversion device 1 of the first embodiment shown in FIG. 1. Specifically, the basic pulse generation unit 410 outputs a basic pulse for controlling the operation of the SW device 136 of the converter 130 to the waveform shape setting unit 420, and outputs a basic pulse for controlling the operation of the SW devices 311a to 311f of the inverter 310 to the inverter 310.

[0077] In the inverter 310, the drive circuit 350 generates drive signals for actually driving the SW devices 311a to 311f based on the basic pulses generated by the basic pulse generating section 410 of the control section 400.

[0078] The waveform shape setting unit 420 sets the waveform shape of the SW waveform of the SW device 136 when the waveform shape changing unit 140 of the converter 130 changes the SW waveform of the SW device 136, according to the state quantities detected by the state quantity detection units 501 to 505. Furthermore, the waveform shape setting unit 420 generates a waveform shape change signal including information instructing a change to the set waveform shape and transmits it to the waveform shape changing unit 140. Specifically, when the SW device 136 is turned on and off based on the basic pulse for controlling the operation of the SW device 136 of the converter 130 generated by the basic pulse generation unit 410, the waveform shape setting unit 420 controls the magnitude of the drive signal that the waveform shape changing unit 140 of the converter 130 outputs to the SW device 136 to actually drive the SW device 136, and the timing at which the drive signal is output.

[0079] The waveform shape modification section 140 receives a waveform shape modification signal transmitted from the waveform shape setting section 420. As described above, the waveform shape modification signal includes information instructing a change to the waveform shape set by the waveform shape setting section 420. The storage section 160 also stores information that contributes to modifying the waveform shape of the SW waveform of the SW device 136 and information instructing a change to a waveform shape that can be instructed by the waveform shape setting section 420, in association with each other.

[0080] The waveform shape modification unit 140 modifies the waveform shape of the SW waveform of the SW device 136 based on the received waveform shape modification signal. Specifically, the waveform shape modification unit 140 reads from the storage unit 160 the contents of the items instructed by the instruction information included in the waveform shape modification signal, and modifies the waveform shape of the SW waveform using the read information. The waveform shape modification unit 140 can modify the waveform shape of the SW waveform of the SW device 136 without physically switching the gate resistor.

[0081] The waveform shape modification unit 140 is capable of outputting two or more waveform shapes as the waveform shape of the SW waveform of the SW device 136. As shown in FIG. 22 , the waveform shape modification unit 140 is included in the converter 130, which is a power converter including the SW device 136. The configuration of the waveform shape modification unit 140 is the same as the configuration of the waveform shape modification unit 340 of the first embodiment shown in FIG. 13 or 15 . That is, the waveform shape modification unit 140 and the SW device 136 are configured by one digital gate driver module. Similarly to the waveform shape modification unit 340, the waveform shape modification unit 140 also outputs the gate current I to the SW device 136 as a drive signal. Ｇ Instead, the gate voltage V output to the SW device 136 Ｇ may be adjusted.

[0082] As described above, in the power conversion apparatus according to the second embodiment, the converter has the functions of the power conversion apparatus according to the first embodiment, and one or more SW devices provided in the converter are configured so that the SW loss is equal to or greater than the conduction loss when the SW device is operating. By using a power conversion apparatus configured in this manner, the control range of the SW loss can be increased by the functions of the waveform shape setting unit and the waveform shape changing unit, and therefore it is possible to fully obtain the effect of introducing the waveform shape changing function into the SW device.

[0083] Embodiment 3. In the first embodiment, a case was described in which the waveform shape of the SW waveform of the SW devices 311a to 311f of the inverter 310 is changed in the power conversion device 1. In the second embodiment, a case was described in which the waveform shape of the SW waveform of the SW device 136 of the converter 130 is changed in the power conversion device 1. In the third embodiment, a case is described in which the set values ​​of the waveform shapes of the SW waveforms of the SW devices 311a to 311f of the inverter 310 and the set value of the waveform shape of the SW device 136 of the converter 130 are changed in the power conversion device 1. That is, in the third embodiment, the SW devices 311a to 311f of the inverter 310 and the SW device 136 of the converter 130 are configured to have the characteristics shown in FIG. 20 , and the waveform shape change function described in the first embodiment is applied to the inverter 310 and the converter 130.

[0084] 23 is a diagram showing an example of the configuration of a power conversion device 1 according to embodiment 3. The power conversion device 1 is connected to a commercial power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage of the power supply voltage supplied from the commercial power supply 110, which is an AC power supply, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. The power conversion device 1 includes a state quantity detection unit 501, a converter 130, a capacitor 210, a state quantity detection unit 502, an inverter 310, a state quantity detection unit 503, a state quantity detection unit 504, a state quantity detection unit 505, and a control unit 400. The power conversion device 1 and the motor 314 form a motor drive device 2.

[0085] The power conversion device 1 of the third embodiment shown in Fig. 23 is configured by removing the drive circuit 150 from the converter 130 and adding a waveform shape changing unit 140 to the power conversion device 1 of the first embodiment shown in Fig. 1. Furthermore, the power conversion device 1 of the third embodiment shown in Fig. 23 has output destinations of the basic pulse generation unit 410 and the waveform shape setting unit 420 changed from those of the power conversion device 1 of the first embodiment shown in Fig. 1. Specifically, the basic pulse generation unit 410 outputs a basic pulse for controlling the operation of the SW devices 311a to 311f of the inverter 310 to the waveform shape setting unit 420, and outputs a basic pulse for controlling the operation of the SW device 136 of the converter 130 to the waveform shape setting unit 420.

[0086] In the present embodiment, the waveform shape setting unit 420 performs the operation described in the first embodiment as well as the operation described in the second embodiment. Furthermore, in the present embodiment, the waveform shape modification unit 340 performs the same operation as that described in the first embodiment, and the waveform shape modification unit 140 performs the same operation as that described in the second embodiment. As a result, the power conversion device 1 performs the same operation as in the first embodiment, thereby being able to change the waveform shapes of the SW waveforms of the SW devices 311a to 311f of the inverter 310 by the waveform shape setting unit 420 and the waveform shape modification unit 340. Furthermore, the power conversion device 1 performs the same operation as in the second embodiment, thereby being able to change the waveform shape of the SW waveform of the SW device 136 of the converter 130 by the waveform shape setting unit 420 and the waveform shape modification unit 140.

[0087] In this embodiment, the power conversion device 1 can also perform control such that at a certain timing, one of the waveform shape modification units 140, 340 changes the waveform shape of the SW waveform of the SW device, while the other does not change the waveform shape of the SW waveform of the SW device. In this embodiment, the SW devices whose SW waveforms are modified by the waveform shape modification units 140, 340 of the power conversion device 1 are one or more SW devices included in at least one of the one or more power converters that perform power conversion in the power conversion device 1.

[0088] As described above, in the power conversion apparatus according to the third embodiment, the inverter and converter have the functions of the power conversion apparatus according to the first embodiment, and one or more SW devices provided in the inverter and converter are configured so that when the SW device operates, the SW loss is equal to or greater than the conduction loss. By using a power conversion apparatus configured in this manner, the control range of the SW loss can be increased by the functions of the waveform shape setting unit and the waveform shape changing unit, and therefore it is possible to fully obtain the effect of introducing the waveform shape changing function into the SW device.

[0089] Fourth Embodiment Fig. 24 is a diagram showing a configuration example of a refrigeration cycle-applied apparatus 900 according to a fourth embodiment. The refrigeration cycle-applied apparatus 900 according to the fourth embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied apparatus 900 according to the fourth embodiment can also include the power conversion device 1 described in the second and third embodiments. The refrigeration cycle-applied apparatus 900 according to the fourth embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 24, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0090] The refrigeration cycle application equipment 900 includes a compressor 315 incorporating the motor 314 in embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0091] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant and a motor 314 that operates the compression mechanism 904 are provided.

[0092] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is variably controlled in speed.

[0093] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 904.

[0094] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0095] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0096] Even if the refrigeration cycle equipment 900 is operating within a specified noise range, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and loss generated by the SW devices 311a to 311f, etc., shifts to the upper right as shown in Figure 10, resulting in an increase in noise. Therefore, the refrigeration cycle equipment 900 can reduce the noise generated by the SW devices 311a to 311f, etc., by slowing down the switching speeds of the SW devices 311a to 311f, etc. Similarly, even if the refrigeration cycle equipment 900 is operating within a specified loss range, when the load state of the motor 314 changes from a light load to a heavy load, the curve showing the characteristics of the noise and loss generated by the SW devices 311a to 311f, etc., shifts to the upper right as shown in Figure 10, resulting in an increase in loss. Therefore, the refrigeration cycle applied equipment 900 can reduce losses occurring in the SW devices 311a to 311f and the like by increasing the SW speed of the SW devices 311a to 311f and the like.

[0097] In the power conversion device 1 included in the refrigeration cycle device 900, the digital gate driver module, which is composed of the waveform shape changing unit 340 and the SW devices 311a to 311f included in the inverter 310, generates a large surge voltage and a lot of electromagnetic noise when the SW speed is fast. If the refrigeration cycle device 900 uses a flammable refrigerant, there is a possibility that the refrigerant may leak and burn due to discharge caused by electromagnetic noise. Therefore, the refrigeration cycle device 900 sets the SW speed of the digital gate driver module included in the power conversion device 1 according to the flammability of the refrigerant used in the refrigeration cycle device 900. For example, the refrigeration cycle device 900 slows the SW speed of the digital gate driver module included in the power conversion device 1 the more flammable the refrigerant used in the refrigeration cycle device 900 is. By slowing the SW speed of the digital gate driver module, the refrigeration cycle device 900 can reduce surge voltage and suppress discharge caused by electromagnetic noise, thereby preventing combustion even if the refrigerant leaks from the refrigeration cycle device 900.

[0098] The refrigerant used in the refrigeration cycle application equipment 900 is, for example, any one of R1234yf, R1234ze(E), R1243zf, HFO1123, HFO1132(E), R1132a, CF3I, and R290 as a single refrigerant, or a mixed refrigerant containing at least two of these refrigerants.

[0099] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0100] 1 Power conversion device, 2 Motor drive device, 91 Processor, 92 Memory, 110 Commercial power supply, 130 Converter, 131 to 134, 131a to 134a Rectifying element, 135, 135a, 135b Reactor, 136, 136a to 136d, 311a to 311f SW device, 137, 137a to 137d, 312a to 312f Freewheeling diode, 138, 138a, 138b Diode, 140, 340 Waveform shape change unit, 150, 350 Drive circuit, 161 Rectifying unit, 162 Boost unit, 163 Rectifying boost unit, 210 Capacitor, 310 Inverter, 314 Motor, 315 Compressor, 400 Control unit, 410 Basic pulse generation unit, 420 Waveform shape setting unit, 501 to 505 state quantity detection units, 900 refrigeration cycle application equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping, GND ground.

Claims

1. A power conversion device that performs power conversion, comprising: one or more switching devices included in at least one of one or more power converters that perform power conversion; a waveform shape changing unit that is capable of changing the waveform shape of a switching waveform of the switching device without physically switching a gate resistor; a state quantity detection unit that detects a state quantity that indicates an operating state of the power conversion device; and a waveform shape setting unit that sets the waveform shape of the switching waveform of the switching device when the waveform shape changing unit changes the switching waveform of the switching device in accordance with the state quantity, wherein a switching loss of the switching device is equal to or greater than a conduction loss of the switching device.

2. The power conversion device according to claim 1, wherein a switching loss of said switching device when said waveform shape changing section changes the waveform shape of said switching waveform to its steepest is equal to or greater than a conduction loss of said switching device.

3. A power conversion device as described in claim 1 or 2, wherein a difference between a switching loss of the switching device when the waveform shape modification section changes the waveform shape of the switching waveform to its gentlest and a switching loss of the switching device when the waveform shape modification section changes the waveform shape of the switching waveform to its steepest is equal to or greater than a conduction loss of the switching device.

4. A power conversion device as claimed in any one of claims 1 to 3, wherein the waveform shape setting unit sets the waveform shape of the switching waveform to be steepest when a product incorporating the power conversion device is operated at half the rated power, and the waveform shape setting unit sets the waveform shape of the switching waveform to be gentlest when a product incorporating the power conversion device is operated at the rated power.

5. A power conversion device as claimed in any one of claims 1 to 3, wherein the waveform shape setting unit sets the waveform shape of the switching waveform to be the steepest when a product incorporating the power conversion device is operated at half the rated power, and the waveform shape setting unit sets the waveform shape of the switching waveform to be the steepest within an allowable noise level range when a product incorporating the power conversion device is operated at rated power.

6. A power conversion device as claimed in any one of claims 1 to 5, wherein the waveform shape changing section has a plurality of transistors mounted for driving the switching device, and is configured to be able to change the waveform shape of the switching waveform of the switching device by changing the number of the plurality of transistors that are operated.

7. A motor drive device comprising a power conversion device according to any one of claims 1 to 6.

8. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 6.

9. The refrigeration cycle equipment according to claim 8, wherein the refrigerant used in the refrigeration cycle equipment is any one of R1234yf, R1234ze(E), R1243zf, HFO1123, HFO1132(E), R1132a, CF3I and R290, or a mixed refrigerant containing at least two of the above refrigerants.

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