PWM converter and motor drive device

Abstract

This PWM converter comprises: a power conversion circuit comprising a three-phase bridge circuit in which a switching element is provided in each of the high potential side upper arm and low potential side lower arm of each of three phases and converting AC power of a three-phase AC power supply into DC power by turning on and off the switching element; a generation circuit which generates a switching command including an on command for turning on the switching element and an off command having an inverse relationship with the on command and turning off the switching element; and an adjustment circuit which generates a switching command for prohibiting all the three-phase switching elements of the upper arms from being turned on at the same time and prohibiting all the three-phase switching elements of the lower arms from being turned on at the same time.

Description

PWM converter and motor drive device

[0001] The present disclosure relates to a PWM converter and a motor drive device.

[0002] A motor drive device that drives an AC motor includes a converter and an inverter. The converter and inverter are connected via a DC link. The converter converts AC power supplied from an AC power source into DC power and outputs it. The inverter converts this DC power into AC power for driving the motor and outputs it. Converters include diode rectifiers and PWM converters. In a diode rectifier, the DC voltage at the DC link (hereinafter referred to as the "DC link voltage") is lower than the peak value of the AC voltage input from the AC power source. On the other hand, a PWM converter has the advantage of being able to boost the DC link voltage to a desired voltage equal to or higher than the peak value of the AC voltage input from the AC power source. The ratio of the value of the DC voltage output by the PWM converter to the peak value of the AC voltage input from the AC power source (i.e., the value of the DC voltage output by the PWM converter / the peak value of the AC voltage input from the AC power source) is called the "boost ratio."

[0003] JP 2014-064447 A JP 2014-217181 A JP 09-065658 A JP 2007-143229 A

[0004] In a PWM converter, the DC link voltage is boosted to a desired value equal to or greater than the peak value of the AC voltage. Therefore, a PWM converter results in a larger difference between the potential of the power lines in the DC link and the potential of their peripheral circuits than a diode-based rectifier. For this reason, a motor drive device using a PWM converter must have a large insulation distance between the power lines in the DC link and their peripheral circuits, which results in an increase in the size of the motor drive device. Therefore, a technology that can reduce the insulation distance between the power lines in the DC link and their peripheral circuits in a motor drive device using a PWM converter is desired.

[0005] According to one aspect of the present disclosure, the PWM converter includes a three-phase bridge circuit in which switching elements are provided in each of an upper arm on the high potential side and a lower arm on the low potential side of each of the three phases, and the power conversion circuit converts AC power from a three-phase AC power source into DC power and outputs the DC power by turning on and off the switching elements in response to received switching commands; a generation circuit that generates switching commands including an ON command for turning on the switching elements and an OFF command for turning off a switching element that is in an inverted relationship with the ON command; and an adjustment circuit that generates switching commands that prohibit all the switching elements of the three phases of the upper arm from being turned on simultaneously and all the switching elements of the three phases of the lower arm from being turned on simultaneously.

[0006] 2A is a diagram illustrating a PWM converter and a motor drive device according to a first embodiment of the present disclosure; FIG. 2B is a diagram illustrating a case where, in a certain time period, switching commands generated by a generation circuit for all three-phase switching elements of an upper arm are ON commands; FIG. 2C is a diagram illustrating a case where a switching command for one phase of the three-phase switching commands generated by the generation circuit shown in FIG. 2A is inverted by an adjustment circuit; FIG. 3D is a diagram illustrating a case where, in a certain time period, switching commands generated by a generation circuit for all three-phase switching elements of a lower arm are ON commands; FIG. 3E is a diagram illustrating a case where a switching command for one phase of the three-phase switching commands generated by the generation circuit shown in FIG. 3A is inverted by an adjustment circuit; FIG. 3F is a diagram illustrating switching commands generated by a generation circuit and an adjustment circuit; FIG. 3G is a flowchart illustrating a switching command generation process in a PWM converter according to a first embodiment of the present disclosure; FIG. 3H is a diagram illustrating a logic circuit constituting the adjustment circuit according to the first embodiment shown in FIG. 6; FIG. 3I is a diagram illustrating an adjustment circuit according to a second embodiment; FIG. 3J is a diagram illustrating a first logic circuit provided in the adjustment circuit according to the second embodiment shown in FIG. 8; 10 is a diagram illustrating a PWM converter and a motor drive device according to a second embodiment of the present disclosure, and FIG. 11 is a flowchart illustrating a switching command generation process in the PWM converter according to the second embodiment of the present disclosure.

[0007] Hereinafter, embodiments of a PWM converter and a motor drive device will be described with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of those components may be omitted. The scale of the drawings has been changed as appropriate to facilitate understanding.

[0008] In the following description, a converter that converts AC power supplied from a three-phase AC power source into DC power and outputs it is also referred to as a “rectifier,” “rectifier device,” “rectifier circuit,” or “forward converter.” Accordingly, a PWM converter is also referred to as a “PWM rectifier,” “PWM rectifier device,” “PWM rectifier circuit,” or “PWM forward converter.” An inverter that converts DC power into AC power and outputs it is also referred to as an “inverter.” A “DC link” refers to a circuit portion that electrically connects the DC output side of a PWM converter and the DC input side of an inverter. A “DC link” is also referred to as a “DC link section,” “DC link,” “DC link section,” “DC bus,” or “DC intermediate circuit.” A “DC link voltage” refers to the potential difference between the positive potential of the positive power line of the DC link and the negative potential of the negative power line. “Connected” means “electrically connected.” A switching element is “on” means that the switching element is closed and an electric path is formed through the switching element. "Off" of a switching element means that the switching element is opened and the electrical path through the switching element is interrupted. An "on command" means a command to turn on a switching element. An "off command" means a command to turn off a switching element. In the following description, when "a switching command is sent to the control terminal of a switching element," the phrase "to the control terminal" may be omitted and simply expressed as "a switching command is sent to the switching element." An AND gate outputs a low signal when only one input is a high signal or when neither input is a high signal, and outputs a high signal when both inputs are high signals. An OR gate outputs a high signal when one or both inputs are high signals, and outputs a low signal when both inputs are low signals. A NOT gate outputs a low signal when the input is a high signal, and outputs a high signal when the input is a low signal.

[0009] <Configuration of Motor Drive Device According to First Embodiment of Present Disclosure> FIG. 1 is a diagram showing a PWM converter and a motor drive device according to a first embodiment of the present disclosure.

[0010] In the first embodiment of the present disclosure and a second embodiment described below, a case will be described in which a motor 300 is driven by a motor drive device 100 connected to a three-phase AC power supply 200, as an example.

[0011] The three-phase AC power supply 200 is an AC power supply having a Y-connection (star-connection) structure. Examples of the three-phase AC power supply 200 include a three-phase 480V AC power supply, a three-phase 400V AC power supply, a three-phase 200V AC power supply, and a three-phase 600V AC power supply. The three-phase AC power supply 200 may also have a Δ-connection (delta-connection) structure.

[0012] The motor 300 may be either an induction motor or a synchronous motor. Furthermore, the number of phases of the motor 300 is not particularly limited in each embodiment, and may be, for example, three-phase or single-phase. Here, as an example, the motor 300 is a three-phase AC motor. Furthermore, the number of motors 300 is not particularly limited in each embodiment, and may be multiple. Here, as an example, there is one motor 300. Machines in which the motor 300 is provided include, for example, machine tools and robots. The motor 300 is used, for example, as a drive source for the feed shaft or spindle of a machine tool, or the arm of an industrial machine or industrial robot.

[0013] 1 , a motor drive device 100 according to a first embodiment of the present disclosure includes a PWM converter 1, an inverter 2, a capacitor 3, and a motor control unit 4. Although not shown here, a power line that supplies power for controlling the motor control unit 4 and the switching command circuit 10 and drive circuit 14 in the PWM converter 1 is provided in a system separate from a power line that supplies power from a three-phase AC power supply 200 to a power conversion circuit 11 in the PWM converter 1.

[0014] The PWM converter 1 has a power regeneration function and performs power conversion between AC power on the three-phase AC power supply 200 side and DC power on the DC link, which is the DC side. The configuration and operation of the PWM converter 1 will be described in detail later. An AC reactor, an AC line filter, an electromagnetic contactor, and the like may be provided on the AC input side of the power conversion circuit 11 in the PWM converter 1, but these are not shown here.

[0015] A capacitor 3 is electrically connected to a DC link between the power conversion circuit 11 in the PWM converter 1 and the inverter 2. The capacitor 3 is sometimes referred to as a "smoothing capacitor," a "DC link capacitor," or a "DC link capacitor." The capacitor 3 has the function of suppressing oscillations in the DC output of the power conversion circuit 11 in the PWM converter 1 and the function of storing DC power used by the inverter 2 to generate AC power. Examples of the capacitor 3 include an electrolytic capacitor and a film capacitor. A pre-charging circuit for pre-charging the capacitor 3 may be provided, but is not shown here.

[0016] The motor control unit 4 executes control to drive the motor 300. The motor control unit 4 generates drive commands to control the rotational speed, position, or torque of the rotor of the motor 300 based on the rotational speed of the motor 300 (rotational speed feedback), the current flowing through the windings of the motor 300 (current feedback), a rotational speed command, a torque command, a position command, and an operation program for the motor 300. Note that the configuration of the motor control unit 4 defined here is merely an example, and the configuration of the motor control unit 4 may be defined by including terms such as a position command generator, a torque command generator, a current controller, a position controller, and a torque controller.

[0017] The DC input side of the inverter 2 is connected to the DC output side of the power conversion circuit 11 in the PWM converter 1 via a DC link. The inverter 2 is composed of a three-phase bridge circuit of switching elements and diodes connected in anti-parallel to the switching elements. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. In response to a drive command from the motor control unit 4, the inverter 2 converts DC power in the DC link into AC power for driving the motor and outputs the AC power to the motor 300. As a result, the motor 300 is driven based on the AC power output from the inverter 2. In response to a drive command from the motor control unit 4, the inverter 2 also converts AC power regenerated during deceleration of the motor 300 into DC power and outputs the DC power to the DC link.

[0018] <Configuration of PWM converter according to first embodiment of the present disclosure>

[0019] 1 , a PWM converter 1 according to the first embodiment of the present disclosure includes a power conversion circuit 11, a switching command circuit 10, and a drive circuit 14. The switching command circuit 10 includes a generation circuit 12 and an adjustment circuit 13.

[0020] The power conversion circuit 11 in the PWM converter 1 is a rectifier capable of power regeneration. The power conversion circuit 11 is made up of a three-phase bridge circuit, and a switching element is provided in each of the upper arms on the high potential side and the lower arms on the low potential side of each of the three phases. A diode is connected in antiparallel to each switching element. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. In the illustrated example, for the U phase, a switching element S is provided in the upper arm. UU is provided, and the lower arm is provided with a switching element S UL For the V phase, a switching element S is provided in the upper arm. VU is provided, and the lower arm is provided with a switching element S VL For the W phase, a switching element S is provided in the upper arm. WU is provided, and the lower arm is provided with a switching element S WLis provided.

[0021] The power conversion circuit 11 performs a rectification operation of converting AC power input from the three-phase AC power supply 200 side into DC power and outputting it to the DC link by turning on and off the switching elements based on the switching commands received from the drive circuit 14. The power conversion circuit 11 can also perform a regeneration operation of converting DC power of the DC link into AC power and outputting it to the three-phase AC power supply 200 side by turning on and off the switching elements based on the switching commands received from the drive circuit 14.

[0022] The generation circuit 12 in the switching command circuit 10 generates switching commands for controlling the on / off operation of the switching elements of the power conversion circuit 11 in the PWM converter 1 according to a PWM (Pulse Width Modulation) method. The switching commands include an on command for turning on the switching elements and an off command for turning off the switching elements. For example, the on command may be a high signal and the off command may be a low signal. Alternatively, the on command may be a low signal and the off command may be a high signal. In this way, the on command and the off command have an inverted relationship between a high signal and a low signal.

[0023] The generator 12 compares a variable amplitude, variable frequency sine wave command with a carrier wave of a constant amplitude and constant frequency, and generates an ON command or an OFF command based on the magnitude relationship between the sine wave command and the carrier wave. By changing the sine wave command, the duty ratio (duty cycle) of the ON command and the OFF command can be changed.

[0024] Switching commands are generated separately for the U, V, and W phases. That is, sine wave commands are prepared for each of the U, V, and W phases, and the sine wave commands are compared with the carrier wave for each phase to generate a switching command for each phase. Furthermore, in each phase, the ON and OFF commands for the upper-arm switching elements and the lower-arm switching elements are inverted (high and low signals are inverted). That is, in each phase, when the switching command for the upper-arm switching elements is an ON command, the switching command for the lower-arm switching elements is an OFF command. Furthermore, in each phase, when the switching command for the upper-arm switching elements is an OFF command, the switching command for the lower-arm switching elements is an ON command. However, if the switching commands for both the upper-arm and lower-arm switching elements in each phase are ON commands, a short circuit occurs in that phase. Therefore, when the switching command for the switching element of one arm switches from an ON command to an OFF command, the switching command for the switching element of the other arm switches from an OFF command to an ON command with a delay.

[0025] As described above, although the switching commands are generated for each phase, there are time periods during which the switching commands for all three phases of the upper arm or lower arm are the same (i.e., the switching commands for all three phases of the upper arm are ON commands, or the switching commands for all three phases of the lower arm are ON commands).

[0026] For example, the U-phase switching element S UU , V-phase switching element S VU , W-phase switching element S WU In a time period when all the switching commands for the respective switching elements S are ON commands, the switching elements S are turned ON in accordance with the ON commands. UU , S VU , and S WUSince a three-phase balanced AC voltage is applied to the PWM converter 1 from the three-phase AC power supply 200, all of the three-phase switching elements S UU , S VU , and S WU During the time period when all of these are turned on at the same time, the potential on the positive side power line of the DC link becomes 0 volts. At this time, the voltage of the capacitor 3 (i.e., the DC link voltage) becomes V dc volts, the negative power line of the DC link will have -V dc For the same reason, the three-phase switching element S of the lower arm UL , S VL , and S WL During the time period when all of these are on at the same time, the potential on the positive power line of the DC link is V dc volts, and a potential of 0 volts appears on the negative power line of the DC link. UU , S VU , and S WU The time period when all of the three-phase switching elements S of the lower arm are turned on at the same time. UL , S VL , and S WL During the time period when all of these are on at the same time, the difference between the potential of the power line in the DC link and the potential of its peripheral circuits is V dc It becomes a bolt.

[0027] For example, the DC link voltage output from the PWM converter 1 (with a step-up ratio of, for example, 1.1) to which an AC voltage of 400 volts is input with a Y connection and a neutral point grounded is 622 volts (= 400 volts × √2 × 1.1). As described above, during the time period when all three phase switches of the upper arm or lower arm are on at the same time, the difference in potential with the peripheral circuit is V dcIn this case, the difference between the potential of the power line in the DC link and the potential of its peripheral circuits is 622 volts. On the other hand, the difference between the DC link's voltage to ground output from a diode rectifier to which an AC voltage with a phase voltage of 400 volts is input, i.e., the potential of the peripheral circuits, is 327 volts (= 400 volts × √2 ÷ √3). Thus, even if the same magnitude of phase voltage is input, the difference between the potential of the power line in the DC link and the potential of its peripheral circuits is larger in the PWM converter 1 than in the diode rectifier.

[0028] Therefore, in order to reduce the insulation distance between the power line in the DC link and the peripheral circuit by suppressing the potential of the power line and the peripheral circuit in the DC link, in the first embodiment of the present disclosure and in the second embodiment described later, in addition to the normal switching command, the adjustment circuit 13 controls the switching elements S of all three phases of the upper arm. UU , S VU , and S WU and a switching command for prohibiting all three phase switching elements S of the lower arm from being turned on simultaneously. UL , S VL , and S WL The adjustment circuit 13 generates a switching command that prohibits the two power supplies from being turned on at the same time. The operation of the adjustment circuit 13 will be described in detail later.

[0029] The driving circuit 14 outputs the switching command generated by the adjusting circuit 13 or the switching command generated by the generating circuit 12 to the switching element S UU , S VU , S WU , S UL , S VL , and S WL The "control terminal" corresponds to the "gate terminal" of a MOSFET, IGBT, thyristor, and GTO, and the "base terminal" of a transistor. More details are as follows.

[0030] The drive circuit 14 drives all three phase switching elements S UU , S VU , and S WUIn contrast, during the time period when all the switching commands generated by the generation circuit 12 are ON commands (all three are ON commands), the adjustment circuit 13 outputs the generated switching commands to the switching elements S UU , S VU , S WU , S UL , S VL , and S WL Similarly, the drive circuit 14 transmits the signals to the control terminals of all the three-phase switching elements S UL , S VL , and S WL In contrast, during the time period when all the switching commands generated by the generation circuit 12 are ON commands (all three are ON commands), the adjustment circuit 13 outputs the generated switching commands to the switching elements S UU , S VU , S WU , S UL , S VL , and S WL The signal is sent to the control terminal of the

[0031] The drive circuit 14 also drives all three phase switching elements S UU , S VU , and S WU On the other hand, in a time period in which all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period in which both ON commands and OFF commands are mixed), the driving circuit 14 directly drives the switching elements S UU , S VU , S WU , S UL , S VL , and S WL Similarly, the drive circuit 14 transmits the signals to the switching elements S of all three phases of the lower arm. UL , S VL , and S WL On the other hand, in a time period in which all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period in which both ON commands and OFF commands are mixed), the driving circuit 14 directly drives the switching elements S UU , S VU , S WU , S UL, S VL , and S WL Send to.

[0032] The power conversion circuit 11 performs a rectifying operation or a regenerative operation by turning on and off the switching elements based on a switching command received from the drive circuit 14 .

[0033] <Generation and Transmission of Switching Commands in PWM Converter> The adjustment circuit 13 controls all three phase switching elements S UU , S VU , and S WU and a switching command for prohibiting all three phase switching elements S of the lower arm from being turned on simultaneously. UL , S VL , and S WL More specifically, the adjustment circuit 13 generates a switching command that prohibits all three phase switching elements S of the upper arm from being turned on at the same time. UU , S VU , and S WU In the time period when all the switching commands generated by the generation circuit 12 are ON commands (all three are ON commands), the adjustment circuit 13 generates a switching command that is the inverse of the switching command generated by the generation circuit 12 for the switching elements of one of the three phases for the upper arm and the lower arm. UL , S VL , and S WL During a time period when all the switching commands generated by the generation circuit 12 for the upper arm and the lower arm are ON commands (all three are ON commands), a switching command that is inverted from the switching command generated by the generation circuit 12 is generated for the switching elements of one of the three phases for the upper arm and the lower arm. Note that the phase for which the inverted switching command is generated may be any one of the U phase, V phase, and W phase.

[0034] 2A is a diagram illustrating a case where, in a certain time period, the switching commands generated by the generating circuit for all three-phase switching elements of the upper arm are ON commands, and FIG. 2B is a diagram illustrating a case where the switching command for one phase of the three-phase switching commands generated by the generating circuit shown in FIG. 2A is inverted by the adjusting circuit.

[0035] As shown in FIG. 2A, during a certain time period, the generating circuit 12 generates the switching elements S of all three phases of the upper arm. UU , S VU , and S WU , and generates an ON command for all three-phase switching elements S UL , S VL , and S WL During this time period, the adjustment circuit 13 generates a switching command that is the inverse of the switching command generated by the generation circuit 12 for the switching element of one of the three phases in the upper arm and the lower arm, as shown in FIG. 2B. That is, the adjustment circuit 13 generates an OFF command for the W-phase switching element S of the upper arm. WU and generates an OFF command instead of the ON command for the W-phase switching element S WL In the example shown in FIG. 2B, as an example, the W-phase switching elements S WU and S WL However, the phase to be inverted is not limited to the W phase. UU and S UL The switching commands for the V-phase switching elements S for the upper and lower arms may be reversed. VU and S VL The switching commands for may be inverted.

[0036] Fig. 3A is a diagram illustrating a case where, in a certain time period, the switching commands generated by the generating circuit for all three-phase switching elements of the lower arm are ON commands, and Fig. 3B is a diagram illustrating a case where the switching command for one phase of the three-phase switching commands generated by the generating circuit shown in Fig. 3A is inverted by the adjusting circuit.

[0037] As shown in FIG. 3A, during a certain time period, the generating circuit 12 generates the switching elements S of all three phases of the upper arm. UU , S VU , and S WU and generates an OFF command for all three-phase switching elements S UL , S VL , and S WL During this time period, the adjustment circuit 13 generates a switching command that is the inverse of the switching command generated by the generation circuit 12 for the switching element of one of the three phases in the upper arm and the lower arm, as shown in FIG. 3B. That is, the adjustment circuit 13 generates an ON command for the W-phase switching element S of the upper arm. WU and generates an ON command instead of the OFF command for the W-phase switching element S WL In the example shown in FIG. 3B, as an example, the W-phase switching elements S WU and S WL However, the phase to be inverted is not limited to the W phase. UU and S UL The switching commands for the V-phase switching elements S for the upper and lower arms may be reversed. VU and S VL The switching commands for may be inverted.

[0038] 4 is a diagram illustrating switching commands generated by the generation circuit and the adjustment circuit. In the example shown in FIG. 4, the phase for which the switching command is inverted by the adjustment circuit 13 is the W phase. In addition, the ON command is a high (H) signal, and the OFF command is a low (L) signal. In FIG. 4, from the top, the drive circuit 14 drives the W phase switching element S of the lower arm. WL , a switching command (indicated by "OUT" in the figure) to be sent to the W-phase switching element S WL a switching command (indicated by "W" in the figure) for the V-phase switching element S of the lower arm generated by the generating circuit 12; VL a switching command (indicated by "V" in the figure) for the U-phase switching element S of the lower arm generated by the generating circuit 12; UL 10 shows a switching command (indicated by "U" in the figure) for the

[0039] As shown in FIG. 4, in the time period from time t1 to time t2, the time period from time t3 to time t4, and the time period from time t5 to time t6, all the switching elements S of the three phases of the lower arm are turned on. UL , S VL , and S WL During these time periods, the adjustment circuit 13 controls the W-phase switching element S WL The drive circuit 14 generates an ON command instead of the OFF command for the W-phase switching element S WL The adjustment circuit 13 transmits the ON command generated by the adjustment circuit 13 to the

[0040] On the other hand, in the time period from time 0 to time t1, the time period from time t2 to time t3, and the time period from time t4 to time t5, all the switching elements S of the three phases of the lower arm are turned on. UL , S VL , and S WL During these time periods, the switching command generated by the generating circuit 12 is not an ON command at the same time. WLThe switching command generated by the generating circuit 12 is sent to the

[0041] FIG. 5 is a flowchart showing a switching command generation process in the PWM converter according to the first embodiment of the present disclosure.

[0042] In step S101, the generation circuit 12 generates, according to the PWM method, switching commands for controlling the on / off operation of the switching elements of the power conversion circuit 11 in the PWM converter 1. The switching commands are generated separately for the U-phase, V-phase, and W-phase. In each phase, the on / off states of the switching commands for the upper-arm switching elements and the lower-arm switching elements are reversed.

[0043] In step S102, the adjustment circuit 13 adjusts the switching elements S of all three phases of the upper arm. UU , S VU , and S WU Whether the switching commands generated by the generating circuit 12 for all three phases are ON commands (ON commands for all three phases) and whether the switching commands for all three phases of the lower arm are ON commands or not UL , S VL , and S WL It is determined whether or not all of the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands).

[0044] If it is determined in step S102 that the switching commands generated by generation circuit 12 for all three-phase switching elements of the upper arm or lower arm are all ON commands (all three are ON commands), then in step S103, adjustment circuit 13 generates, for the switching elements of one of the three phases of the upper arm and lower arm, a switching command that is the inverse of the switching command generated by generation circuit 12. After processing in step S103, the process proceeds to step S104.

[0045] In step S104, the driving circuit 14 outputs the switching command generated by the adjustment circuit 13 or the switching command generated by the generation circuit 12 to the switching element S UU , SVU , S WU , S UL , S VL , and S WL More specifically, if it is determined in step S102 that the switching commands generated by the generation circuit 12 for all three-phase switching elements for the upper arm or the lower arm are all ON commands (all three are ON commands), the drive circuit 14 transmits the switching commands generated by the adjustment circuit 13 to the control terminals of the switching elements S UU , S VU , S WU , S UL , S VL , and S WL If it is not determined in step S102 that the switching commands generated by the generation circuit 12 for all three-phase switching elements of the upper arm or the lower arm are all ON commands (all three are ON commands), the drive circuit 14 transmits the switching commands generated by the generation circuit 12 in step S101 to the control terminals of the switching elements S UU , S VU , S WU , S UL , S VL , and S WL The signal is sent to the control terminal of the

[0046] After the process of step S104, the process returns to step S101. The processes of steps S101 to S104 are repeatedly executed at a predetermined cycle.

[0047] <Configuration of Adjustment Circuit> Several configurations of the adjustment circuit 13 are listed below. The configurations listed here are applicable to the first embodiment and the second embodiment described below.

[0048] Fig. 6 is a diagram illustrating a regulator circuit according to the first embodiment. Fig. 7 is a diagram illustrating a logic circuit constituting the regulator circuit according to the first embodiment shown in Fig. 6. In Figs. 6 and 7, as an example, all three phase switching elements S UU , S VU , and S WUThe time period in which all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), and the time period in which all the switching elements S of the three phases of the lower arm are ON commands UL , S VL , and S WL In a time period in which all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the W-phase switching elements S WU and S WL 6, the driving circuit 14 is not shown.

[0049] The adjustment circuit 13 according to the first embodiment includes a logic circuit 130 .

[0050] The U-phase switching command generated by the generating circuit 12 is transmitted to the upper arm switching element S of the U-phase via the driving circuit 14. UU and the lower arm switching element S UL In the U phase, the upper arm switching element S UU and the switching command for the lower arm switching element S UL Since the on / off is reversed with respect to the switching command for the upper arm switching element S UU A NOT gate 61 that performs a logical NOT operation is provided on the signal line to the U-phase switching command generator 12. The U-phase switching command generated by the generator 12 is also transmitted to a logic circuit 130 in the adjustment circuit 13.

[0051] The V-phase switching command generated by the generating circuit 12 is transmitted to the V-phase upper arm switching element S via the driving circuit 14. VU and the lower arm switching element S VL In the V phase, the upper arm switching element S VU and the switching command for the lower arm switching element S VL Since the on / off is reversed with respect to the switching command for the upper arm switching element S VUA NOT gate 62 that performs a logical NOT operation is provided on the signal line to the V-phase switching command generator 12. The V-phase switching command generated by the generator 12 is also sent to a logic circuit 130 in the adjustment circuit 13.

[0052] The W-phase switching command generated by the generating circuit 12 is sent to the logic circuit 130 in the adjusting circuit 13 .

[0053] 7, the logic circuit 130 includes a first NOT gate 21, a second NOT gate 22, a first AND gate 23, a second AND gate 24, a third AND gate 25, and an OR gate 26. The first NOT gate 21 and the second NOT gate 22 are logical negation (NOT) gates. The first AND gate 23, the second AND gate 24, and the third AND gate 25 are logical product (AND) gates. The OR gate 26 is a logical sum (OR) gate.

[0054] The first NOT gate 21 receives the U-phase switching command generated by the generation circuit 12. The output terminal of the first NOT gate 21 is connected to the input terminals of the first AND gate 23 and the second AND gate 24.

[0055] The second NOT gate 22 receives the V-phase switching command generated by the generation circuit 12. The output terminal of the second NOT gate 22 is connected to the input terminals of the first AND gate 23 and the third AND gate 25.

[0056] The W-phase switching command generated by the generating circuit 12 is input to a second AND gate 24 and a third AND gate 25. In the W-phase, the upper arm switching element S WU and the switching command for the lower arm switching element S WL Since the on / off is reversed with respect to the switching command for the upper arm switching element S WU A NOT gate 63 for performing a logical NOT operation is provided on the signal line to

[0057] The output terminals of the first AND gate 23, the second AND gate 24, and the third AND gate 25 are connected to the input terminals of an OR gate 26. The output of the OR gate 26 is connected to the upper arm switching element S of the W phase by the drive circuit 14. WU and the lower arm switching element S WL will be sent to.

[0058] The logical formula in the logic circuit 130 shown in Fig. 7 can be expressed as Equation 1. In Equation 1, the U-phase switching command output from the generation circuit 12 is represented as U, the V-phase switching command is represented as V, and the W-phase switching command is represented as W. The W-phase switching command output from the logic circuit 130 is represented as OUT. The commands U, V, and W, which are obtained by logical negation (NOT) calculation, have a bar above each character.

[0059]

[0060] According to the logical formula of Equation 1, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 are all ON commands (high signals), the W-phase switching command OUT output from the logic circuit 130 is an OFF command (low signal). Furthermore, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 are all OFF commands (low signals), the W-phase switching command OUT output from the logic circuit 130 is an ON command (high signal). Furthermore, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 include at least one ON command (high signal) and at least one OFF command (low signal), the W-phase switching command OUT output from the logic circuit 130 is the same command as the W-phase switching command W generated by the generation circuit 12.

[0061] Therefore, by providing the adjustment circuit 13 according to the first embodiment in the switching command circuit 10, all the switching elements S of the three phases of the upper arm can be UU , S VU , and S WUThe time period in which all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), and the time period in which all the switching elements S of the three phases of the lower arm are ON commands UL , S VL , and S WL In a time period in which all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the W-phase switching elements S WU and S WL In addition, the switching commands for all three phase switching elements S UU , S VU , and S WU In the case where all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period including both ON commands and OFF commands), and in the case where all three phases of the switching elements S UL , S VL , and S WL On the other hand, in a time period in which all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period including both ON commands and OFF commands), the switching commands generated by the generating circuit 12 are directly applied to the switching element S UU , S VU , S WU , S UL , S VL , and S WL will be sent to.

[0062] Fig. 8 is a diagram illustrating a regulator circuit according to a second embodiment. Fig. 9A is a diagram illustrating a first logic circuit provided in the regulator circuit according to the second embodiment shown in Fig. 8. Fig. 9B is a diagram illustrating a second logic circuit provided in the regulator circuit according to the second embodiment shown in Fig. 8. In Figs. 8, 9A, and 9B, as an example, all three phase switching elements S UU , S VU , and S WU In contrast, in a time period when all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the U-phase switching elements S UU and SUL The switching command for all three phase switching elements S UL , S VL , and S WL On the other hand, in a time period when all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the V-phase switching elements S VU and S VL 8, the driving circuit 14 is not shown.

[0063] The adjustment circuit 13 according to the first embodiment includes a first logic circuit 131 and a second logic circuit 132 .

[0064] The U-phase switching command generated by the generating circuit 12 is transmitted to the first logic circuit 131 and the second logic circuit 132 in the adjusting circuit 13. In the U-phase, the upper arm switching element S UU and the switching command for the lower arm switching element S UL Since the on / off is reversed with respect to the switching command for the upper arm switching element S UU A NOT gate 71 for performing a logical NOT operation is provided on the signal line to

[0065] The V-phase switching command generated by the generating circuit 12 is transmitted to the first logic circuit 131 and the second logic circuit 132 in the adjusting circuit 13. In the V-phase, the upper arm switching element S VU and the switching command for the lower arm switching element S VL Since the on / off is reversed with respect to the switching command for the upper arm switching element S VU A NOT gate 72 for performing a logical NOT operation is provided on the signal line to

[0066] The W-phase switching command generated by the generating circuit 12 is transmitted to the upper arm switching element S of the W-phase via the driving circuit 14. WU and the lower arm switching element S WL In the W phase, the upper arm switching element SWU and the switching command for the lower arm switching element S WL Since the on / off is reversed with respect to the switching command for the upper arm switching element S WU A NOT gate 73 that performs a logical negation (NOT) operation is provided on the signal line to the W-phase switching command generator 12. The W-phase switching command generated by the generator 12 is also transmitted to a first logic circuit 131 and a second logic circuit 132 in the adjustment circuit 13.

[0067] The first logic circuit 131 controls the U-phase switching element S UU and S UL 9A, the first logic circuit 131 includes a fourth AND gate 31, a third NOT gate 32, and a fifth AND gate 33. The third NOT gate 32 is a logical negation (NOT) gate. The fourth AND gate 31 and the fifth AND gate 33 are logical product (AND) gates.

[0068] The fourth AND gate 31 receives the U-phase switching command, V-phase switching command, and W-phase switching command generated by the generation circuit 12. The output terminal of the fourth AND gate 31 is connected to the input terminal of the third NOT gate 32. The output terminal of the third NOT gate 32 is connected to the input of the fifth AND gate 33. The U-phase switching command generated by the generation circuit 12 is also input to the fifth AND gate 33. The output of the fifth AND gate 33 is used by the drive circuit 14 to drive the upper arm switching element S of the U-phase. UU and the lower arm switching element S UL will be sent to.

[0069] 9A can be expressed as Equation 2. In Equation 2, the U-phase switching command output from the generation circuit 12 is represented as U, the V-phase switching command is represented as V, and the W-phase switching command is represented as W. The U-phase switching command output from the first logic circuit 131 is represented as OUT. The commands U, V, and W, which are obtained by logical negation (NOT) calculation, have a bar above each character.

[0070]

[0071] According to the logical formula of Equation 2, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 are all ON commands (high signals), the U-phase switching command OUT output from the first logic circuit 131 is an OFF command (low signal). Furthermore, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 include at least one ON command (high signal) and at least one OFF command (low signal), the U-phase switching command OUT output from the first logic circuit 131 is the same command as the U-phase switching command U generated by the generation circuit 12.

[0072] The second logic circuit 132 controls the V-phase switching element S VU and S VL 9B , the second logic circuit 132 includes a fourth NOT gate 41, a fifth NOT gate 42, a sixth NOT gate 43, a sixth AND gate 44, a seventh NOT gate 45, a seventh AND gate 46, and an eighth NOT gate 47. The fourth NOT gate 41, the fifth NOT gate 42, the sixth NOT gate 43, the seventh NOT gate 45, and the eighth NOT gate 47 are logical negation (NOT) logic gates. The sixth AND gate 44 and the seventh AND gate 46 are logical product (AND) logic gates.

[0073] The fourth NOT gate 41 receives the U-phase switching command generated by the generation circuit 12. The output terminal of the fourth NOT gate 41 is connected to the input terminal of the sixth AND gate 44.

[0074] The V-phase switching command generated by the generation circuit 12 is input to the fifth NOT gate 42. The output terminal of the fifth NOT gate 42 is connected to the input terminals of the sixth AND gate 44 and the seventh AND gate.

[0075] The sixth NOT gate 43 receives the W-phase switching command generated by the generation circuit 12. The output terminal of the sixth NOT gate 43 is connected to the input terminal of the sixth AND gate 44.

[0076] The output terminal of the sixth AND gate 44 is connected to the input terminal of a seventh NOT gate 45. The output terminal of the seventh NOT gate 45 is connected to the input terminal of a seventh AND gate 46.

[0077] The output terminal of the seventh AND gate 46 is connected to the input terminal of the eighth NOT gate 47. The output of the eighth NOT gate 47 is connected to the V-phase upper arm switching element S WU and the lower arm switching element S WL will be sent to.

[0078] The logical expression in the second logic circuit 132 shown in FIG. 9B can be expressed as in Expression 3. In Expression 3, the U-phase switching command output from the generation circuit 12 is represented as U, the V-phase switching command is represented as V, and the W-phase switching command is represented as W. The W-phase switching command output from the logic circuit 130 is represented as OUT. The commands U, V, and W, which are obtained by logical negation (NOT) calculation, have a bar above each character.

[0079]

[0080] According to the logical formula of Equation 3, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 are all OFF commands (low signals), the V-phase switching command OUT output from the second logic circuit 132 is an ON command (high signal). Furthermore, when the U-phase switching command U, the V-phase switching command V, and the W-phase switching command W generated by the generation circuit 12 include at least one ON command (high signal) and at least one OFF command (low signal), the U-phase switching command OUT output from the first logic circuit 131 is the same command as the V-phase switching command V generated by the generation circuit 12.

[0081] Therefore, by providing the adjustment circuit 13 according to the second embodiment in the switching command circuit 10, all the switching elements S of the three phases of the upper arm can be UU , S VU , and S WU In contrast, in a time period when all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the U-phase switching elements S UU and S UL In addition, the switching commands for all three phase switching elements S UL , S VL , and S WL On the other hand, in a time period when all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the V-phase switching elements S VU and S VL In addition, the switching commands for all three phase switching elements S UU , S VU , and S WU In the case where all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period including both ON commands and OFF commands), and in the case where all three phases of the switching elements S UL , S VL , and S WL On the other hand, in a time period in which all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period including both ON commands and OFF commands), the switching commands generated by the generating circuit 12 are directly applied to the switching element S UU , S VU , S WU , S UL , S VL , and S WL will be sent to.

[0082] <Configuration of a Motor Drive Device According to a Second Embodiment of the Present Disclosure> Fig. 10 is a diagram showing a PWM converter and a motor drive device according to a second embodiment of the present disclosure. The second embodiment of the present disclosure is a configuration in which, when the neutral point potential of three-phase AC power supply 200 is less than a predetermined threshold in the first embodiment described with reference to Figs. 1 to 9, all three phase switching elements S for the upper arm are turned on. UU , S VU , and S WU and a switching command for prohibiting all three phase switching elements S of the lower arm from being turned on simultaneously. UL , S VL , and S WL The threshold value is set to determine whether the neutral point potential of the three-phase AC power supply 200 is approximately 0 volts. The threshold value is set to, for example, several millivolts to 10 volts, but may be any other value. If all the switching elements of the three phases of the upper arm or the lower arm are simultaneously turned on when the neutral point potential of the three-phase AC power supply 200 is near 0 volts, the difference between the potential of the power line in the DC link and the potential of its peripheral circuits becomes very large. Therefore, in the second embodiment of the present disclosure, a switching command is generated to prohibit the switching elements of the upper arm or the lower arm from being simultaneously turned on when the neutral point potential of the three-phase AC power supply 200 is near 0 volts.

[0083] As shown in FIG. 10 , a motor drive device 100 according to the second embodiment of the present disclosure includes a PWM converter 1, an inverter 2, a capacitor 3, and a motor control unit 4.

[0084] The inverter 2, the capacitor 3, the motor control unit 4, the three-phase AC power supply 200, and the motor 300 are as described in the first embodiment.

[0085] <Configuration and Operation of PWM Converter According to Second Embodiment of the Present Disclosure>

[0086] As shown in FIG. 10 , the PWM converter 1 according to the second embodiment of the present disclosure includes a power conversion circuit 11 , a switching command circuit 10 , a drive circuit 14 , and a detection circuit 15 .

[0087] The detection circuit 15 detects the neutral point potential of the three-phase AC power supply 200. Data relating to the detected value of the neutral point potential is sent to the adjustment circuit 13.

[0088] The power conversion circuit 11 is as described in the first embodiment.

[0089] The switching command circuit 10 includes a generating circuit 12 and an adjusting circuit 13. An example of the configuration of the logic circuit in the adjusting circuit 13 is as described in the first embodiment.

[0090] The generating circuit 12 is as described in the first embodiment.

[0091] In the second embodiment, when the neutral point potential detected by the detection circuit 15 is less than a predetermined threshold, the adjustment circuit 13 controls all the switching elements S of the three phases of the upper arm. UU , S VU , and S WU and a switching command for prohibiting all three phase switching elements S of the lower arm from being turned on simultaneously. UL , S VL , and S WL The threshold value is set to determine whether the neutral point potential of the three-phase AC power supply 200 is approximately 0 volts. The threshold value is set to, for example, a few millivolts to 10 volts, but may be any other value.

[0092] During a time period when the neutral point potential detected by the detection circuit 15 is less than a predetermined threshold and the switching commands generated by the generation circuit for all the switching elements of the three phases of the upper arm or the lower arm are all ON commands, the adjustment circuit 13 generates a switching command that is the inverse of the switching command generated by the generation circuit 12 for the switching element of one of the three phases of the upper arm or the lower arm. More details are as follows.

[0093] The adjustment circuit 13 detects that the neutral point potential detected by the detection circuit 15 is less than a predetermined threshold value and that all three phase switching elements SUU , S VU , and S WU During the time period when all the switching commands generated by the generation circuit 12 are ON commands (all three are ON commands), an OFF command is generated instead of the ON command for the switching element of one of the three phases of the upper arm, and an ON command is generated instead of an OFF command for the switching element of that phase of the lower arm.

[0094] The adjustment circuit 13 detects that the neutral point potential detected by the detection circuit 15 is less than a predetermined threshold value and that all the three-phase switching elements S of the lower arm are in a UL , S VL , and S WL During the time period when all the switching commands generated by the generation circuit 12 are ON commands (all three are ON commands), an OFF command is generated instead of the ON command for the switching element of one of the three phases of the lower arm, and an ON command is generated instead of an OFF command for the switching element of that phase of the upper arm.

[0095] The drive circuit 14 is configured to detect the neutral point potential detected by the detection circuit 15 as being less than a predetermined threshold value and all three phase switching elements S UU , S VU , and S WU The time period in which all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), and the time period in which all the switching elements S of the three phases of the lower arm are ON commands UL , S VL , and S WL On the other hand, during a time period when all the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands), the adjusting circuit 13 transmits the generated switching command to the switching element.

[0096] Further, the drive circuit 14 drives all three phase switching elements S of the upper arm during the time period when the neutral point potential detected by the detection circuit 15 is not less than a predetermined threshold. UU , S VU , and S WUIn the time period when all three switching commands generated by the generating circuit 12 are not ON commands (i.e., the time period when ON commands and OFF commands are mixed), and in the time period when all three switching elements S UL , S VL , and S WL On the other hand, in a time period in which all three switching commands generated by the generating circuit 12 are not ON commands (i.e., a time period in which ON commands and OFF commands are mixed), the driving circuit 14 directly drives the switching elements S UU , S VU , S WU , S UL , S VL , and S WL Send to.

[0097] FIG. 5 is a flowchart showing a switching command generation process in the PWM converter according to the first embodiment of the present disclosure.

[0098] The detection circuit 15 constantly detects the neutral point potential of the three-phase AC power supply 200 , and data relating to the detected value of the neutral point potential is sent to the adjustment circuit 13 .

[0099] In step S201, the generation circuit 12 generates, according to the PWM method, switching commands for controlling the on / off operation of the switching elements of the power conversion circuit 11 in the PWM converter 1. The switching commands are generated separately for the U-phase, V-phase, and W-phase. In each phase, the on / off states of the switching commands for the upper-arm switching elements and the lower-arm switching elements are reversed.

[0100] In step S202, the adjustment circuit 13 determines whether the neutral point potential detected by the detection circuit 15 is less than a predetermined threshold value.

[0101] If it is not determined in step S202 that the neutral point potential is less than the threshold value, the process proceeds to step S205.

[0102] If it is determined in step S202 that the neutral point potential is less than the threshold value, the process proceeds to step S203.

[0103] In step S203, the adjustment circuit 13 adjusts the switching elements S of all three phases of the upper arm. UU , S VU , and S WU Whether the switching commands generated by the generating circuit 12 for all three phases are ON commands (ON commands for all three phases) and whether the switching commands for all three phases of the lower arm are ON commands or not UL , S VL , and S WL It is determined whether or not all of the switching commands generated by the generating circuit 12 are ON commands (all three are ON commands).

[0104] If it is determined in step S203 that the switching commands generated by generation circuit 12 for all three-phase switching elements of the upper arm or lower arm are all ON commands (all three are ON commands), then in step S204, adjustment circuit 13 generates, for the switching elements of one of the three phases of the upper arm and lower arm, a switching command that is the inverse of the switching command generated by generation circuit 12. After processing in step S204, the process proceeds to step S205.

[0105] In step S205, the driving circuit 14 outputs the switching command generated by the adjustment circuit 13 or the switching command generated by the generation circuit 12 to the switching element S UU , S VU , S WU , S UL , S VL , and S WL More specifically, if it is determined in step S203 that the switching commands generated by the generation circuit 12 for all three-phase switching elements for the upper arm or the lower arm are all ON commands (all three are ON commands), the drive circuit 14 transmits the switching commands generated by the adjustment circuit 13 to the control terminals of the switching elements S UU , S VU , S WU , S UL , S VL , and S WLIf it is not determined in step S204 that the switching commands generated by the generation circuit 12 for all three-phase switching elements of the upper arm or the lower arm are all ON commands (all three are ON commands), the drive circuit 14 transmits the switching commands generated by the generation circuit 12 in step S101 to the control terminals of the switching elements S UU , S VU , S WU , S UL , S VL , and S WL If it is not determined in step S202 that the neutral point potential is less than the threshold value, the drive circuit 14 transmits the switching command generated by the generation circuit 12 in step S101 to the control terminal of the switching element S. UU , S VU , S WU , S UL , S VL , and S WL The signal is sent to the control terminal of the

[0106] After the process of step S205, the process returns to step S201. The processes of steps S201 to S205 are repeatedly executed at a predetermined cycle.

[0107] <Processor and Memory> The motor drive device 100 includes at least one processor, which is an arithmetic processing device. Examples of arithmetic processing devices include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device includes a switching command circuit 10, a drive circuit 14, a detection circuit 15, a motor control unit 4, and other processing units. Each of these units in the arithmetic processing device is a functional module implemented by a program executed on the processor. For example, if the switching command circuit 10, the drive circuit 14, the detection circuit 15, the motor control unit 4, and other processing units are implemented in a program format, the functions of each unit can be realized by operating the arithmetic processing device in accordance with the program. The programs for executing the processes in the switching command circuit 10, the drive circuit 14, the detection circuit 15, the motor control unit 4, and other processing units may be provided in the form of a computer-readable recording medium, such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the switching command circuit 10, the drive circuit 14, the detection circuit 15, the motor control unit 4, and other processing units may be implemented as semiconductor integrated circuits on which programs for implementing the functions of each unit are written. The switching command circuit 10 may also be configured as a combination of an analog circuit and a processing unit.

[0108] The motor drive device 100 also includes at least one memory serving as a storage device. The memory includes the switching command circuit 10, the drive circuit 14, the detection circuit 15, the motor control unit 4, and various storage units within other processing units. Examples of the memory include electrically erasable and recordable nonvolatile memory such as EEPROM (registered trademark), or high-speed read / write random access memory such as DRAM or SRAM. The storage unit may also have a configuration such as an HDD (hard disk drive) or SSD (solid state drive). The memory stores programs for operating the switching command circuit 10, the drive circuit 14, the detection circuit 15, the motor control unit 4, and other processing units. The memory also stores switching commands generated by the generation circuit 12, switching commands generated by the adjustment circuit 13, threshold values ​​used in the adjustment circuit 13, and data related to the neutral point potential of the three-phase AC power supply 200 detected by the detection circuit 15. The memory also stores various programs and data related to the PWM converter 1. The memory stores various programs and various data related to the inverter 2. The memory stores various programs and various data related to the motor drive device 100.

[0109] Advantages of the Embodiments of the Present Disclosure According to the first and second embodiments of the present disclosure, in a motor drive device using a PWM converter, it is possible to reduce the insulation distance between the power line in the DC link and its peripheral circuitry. Even when the same phase voltage is input, the difference between the potential of the power line in the DC link and the potential of its peripheral circuitry is larger in a PWM converter than in a diode-based rectifier. In particular, in a PWM converter, the difference between the potential of the power line in the DC link and the potential of its peripheral circuitry becomes very large during a period when all three switching elements of the upper arm or lower arm are simultaneously turned on. According to the first and second embodiments of the present disclosure, by generating a switching command that prohibits all three switching elements of the upper arm or lower arm from simultaneously turning on, the difference between the potential of the power line in the DC link and the potential of its peripheral circuitry is reduced. This reduces the insulation distance between the power line in the DC link and its peripheral circuitry, thereby enabling the motor drive device to be miniaturized.

[0110] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments and individual variations described above. Various additions, substitutions, modifications, partial deletions, etc. are possible for these embodiments and variations within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. These embodiments and variations can also be implemented in combination. For example, in the above-described embodiments and variations, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments and variations.

[0111] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above-described embodiment and modifications.

[0112] (Supplementary Note 1) A PWM converter comprising: a power conversion circuit including a three-phase bridge circuit in which switching elements are provided in each of an upper arm on the high potential side and a lower arm on the low potential side of each of the three phases, the power conversion circuit converting AC power from a three-phase AC power source into DC power and outputting the DC power by causing the switching elements to perform on / off operations in response to received switching commands; a generation circuit generating switching commands including an on command for performing on operations on the switching elements and an off command for performing off operations on switching elements that have an inverted relationship with the on command; and an adjustment circuit generating switching commands that prohibit all switching elements of the three phases of the upper arm from being simultaneously turned on and all switching elements of the three phases of the lower arm from being simultaneously turned on. (Supplementary Note 2) The PWM converter according to Supplementary Note 1, further comprising: a drive circuit that transmits the switching commands generated by the adjustment circuit to the switching elements during a time period in which all switching commands generated by the generation circuit for all switching elements of the three phases of the upper arm or the lower arm are on commands, and that transmits the switching commands generated by the generation circuit to the switching elements during other time periods. (Supplementary Note 3) The PWM converter according to Supplementary Note 2, wherein, in a time period when the switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm or the lower arm are all on commands, the adjustment circuit generates a switching command that is inverted from the switching command generated by the generation circuit for the switching elements of one of the three phases of the upper arm and the lower arm. (Supplementary Note 4) The PWM converter according to Supplementary Note 3, wherein, in a time period when the switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm are all on commands, the adjustment circuit generates an off command for the switching elements of one of the three phases of the upper arm instead of the on command, and in a time period when the switching commands generated by the generation circuit for the switching elements of all three phases of the lower arm are all on commands, the adjustment circuit generates an off command for the switching elements of one of the three phases of the lower arm instead of the on command.(Supplementary Note 5) The PWM converter according to Supplementary Note 4, wherein the adjustment circuit generates an ON command for the switching element of one phase of the lower arm in a time period when all of the switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm are ON commands, and generates an ON command for the switching element of one phase of the upper arm in a time period when all of the switching commands generated by the generation circuit for the switching elements of all three phases of the lower arm are ON commands. (Supplementary Note 6) The PWM converter according to Supplementary Note 2, further comprising a detection circuit that detects a neutral point potential of the three-phase AC power supply, wherein in a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold and all of the switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm or the lower arm are ON commands, the adjustment circuit generates a switching command that is inverted from the switching command generated by the generation circuit for the switching elements of one of the three phases of the upper arm and the lower arm. (Supplementary Note 7) A PWM converter according to Supplementary Note 6, wherein the adjustment circuit generates an off command for the switching element of one of the three phases of the upper arm in place of the on command during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and all switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm are on commands, and generates an off command for the switching element of one of the three phases of the lower arm in place of the on command during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and all switching commands generated by the generation circuit for the switching elements of all three phases of the lower arm are on commands.(Supplementary Note 8) A PWM converter according to Supplementary Note 7, wherein the adjustment circuit generates an ON command for a switching element of one phase of the lower arm in a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold and the switching commands generated by the generation circuit for all switching elements of three phases of the upper arm are ON commands, and generates an ON command for a switching element of one phase of the upper arm in a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold and the switching commands generated by the generation circuit for all switching elements of three phases of the lower arm are ON commands. (Supplementary Note 9) A motor drive device comprising: the PWM converter according to any one of Supplementary Notes 1 to 8; a capacitor provided in a DC link that is a DC side of the PWM converter; an inverter connected to the PWM converter via the DC link, and configured to convert DC power supplied from the DC link into AC power for driving the motor and output the AC power; and a motor control unit that executes control to drive the motor.

[0113] REFERENCE SIGNS LIST 1 PWM converter 2 Inverter 3 Capacitor 4 Motor control unit 10 Switching command circuit 11 Power conversion circuit 12 Generation circuit 13 Adjustment circuit 14 Drive circuit 15 Detection circuit 21 First NOT gate 22 Second NOT gate 23 First AND gate 24 Second AND gate 25 Third AND gate 26 OR gate 31 Fourth AND gate 31 32 Third NOT gate 33 Fifth AND gate 41 Fourth NOT gate 42 Fifth NOT gate 43 Sixth NOT gate 44 Sixth AND gate 45 Seventh NOT gate 46 Seventh AND gate 47 Eighth NOT gate 61, 62, 63, 71, 72, 73 NOT gate 100 Motor drive device 130 Logic circuit 131 First logic circuit 132 Second logic circuit 200 Three-phase AC power supply 300 Motor S UL Lower arm U-phase switching element S UUUpper arm U-phase switching element S VL Lower arm V-phase switching element S VU Upper arm V-phase switching element S WL Lower arm W-phase switching element S WU Upper arm W-phase switching element

Claims

1. A PWM converter comprising: a power conversion circuit consisting of a three-phase bridge circuit in which switching elements are provided in each of the upper arms on the high potential side and the lower arms on the low potential side of each of the three phases, and which converts AC power from a three-phase AC power source into DC power and outputs it by turning the switching elements on and off in response to received switching commands; a generation circuit which generates switching commands including an on command for turning on the switching elements and an off command for turning off the switching elements that are in an inverted relationship with the on command; and an adjustment circuit which generates switching commands that prohibit all three phase switching elements for the upper arm from being turned on simultaneously and all three phase switching elements for the lower arm from being turned on simultaneously.

2. A PWM converter as described in claim 1, further comprising a drive circuit that transmits the switching commands generated by the adjustment circuit to the switching elements during a time period when all of the switching commands generated by the generation circuit for the switching elements of all three phases of the upper arm or the lower arm are on commands, and transmits the switching commands generated by the generation circuit to the switching elements during other time periods.

3. A PWM converter as described in claim 2, wherein, during a time period when the switching commands generated by the generation circuit for all three-phase switching elements of the upper arm or the lower arm are all ON commands, the adjustment circuit generates a switching command for one of the three-phase switching elements of the upper arm and the lower arm that is the inverse of the switching command generated by the generation circuit.

4. A PWM converter as described in claim 3, wherein the adjustment circuit generates an off command for a switching element of one of the three phases of the upper arm in place of an on command during a time period when the switching commands generated by the generation circuit for all three phases of the upper arm are on commands, and generates an off command for a switching element of one of the three phases of the lower arm in place of an on command during a time period when the switching commands generated by the generation circuit for all three phases of the lower arm are on commands.

5. A PWM converter as described in claim 4, wherein the adjustment circuit generates an on command for the one-phase switching element of the lower arm during a time period when the switching commands generated by the generation circuit for all three-phase switching elements of the upper arm are all on commands, and generates an on command for the one-phase switching element of the upper arm during a time period when the switching commands generated by the generation circuit for all three-phase switching elements of the lower arm are all on commands.

6. The PWM converter according to claim 2, further comprising a detection circuit for detecting a neutral point potential of the three-phase AC power supply, wherein during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and the switching commands generated by the generation circuit for all three-phase switching elements in the upper arm or the lower arm are all on commands, the adjustment circuit generates a switching command for one of the three phase switching elements in the upper arm or the lower arm that is the inverse of the switching command generated by the generation circuit.

7. A PWM converter as described in claim 6, wherein the adjustment circuit generates an OFF command instead of an ON command for a switching element of one of the three phases in the upper arm during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and the switching commands generated by the generation circuit for all three phases of the upper arm are ON commands, and generates an OFF command instead of an ON command for a switching element of one of the three phases in the lower arm during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and the switching commands generated by the generation circuit for all three phases of the lower arm are ON commands.

8. A PWM converter as described in claim 7, wherein the adjustment circuit generates an on command for the one-phase switching element of the lower arm during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and the switching commands generated by the generation circuit for all three-phase switching elements of the upper arm are all on commands, and generates an on command for the one-phase switching element of the upper arm during a time period when the neutral point potential detected by the detection circuit is less than a predetermined threshold value and the switching commands generated by the generation circuit for all three-phase switching elements of the lower arm are all on commands.

9. A motor drive device comprising: a PWM converter according to any one of claims 1 to 8; a capacitor provided in a DC link that is the DC side of said PWM converter; an inverter connected to said PWM converter via said DC link, which converts DC power supplied from said DC link into AC power for driving a motor and outputs the AC power; and a motor control unit which executes control to drive said motor.

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