Switching control method and switching control device

Abstract

To provide a switching control method and a switching control device in which an arithmetic load of a microcomputer is small and sound vibration is reduced.SOLUTION: A switching control method is provided for controlling a semiconductor switching element 31 for generating a control signal by using a reference wave and a carrier wave to drive a load by the control signal. The switching control method sets a plurality of carrier waves whose combination pattern of a first carrier frequency Fc1 and a second carrier frequency Fc2 is different. With the carrier wave, the first carrier frequency Fc1 and the second carrier frequency Fc2 different from the first carrier frequency Fc1 are alternately combined. Then, at least two carrier waves having a different combination pattern of the carrier frequency are switched in a predetermined control period T of the load, and a control signal is generated by using at least two carrier waves to be switched.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a switching control method and a switching control device. [Background technology]

[0002] Patent Document 1 discloses a control method for a power converter that generates a control signal (PWM signal) based on a carrier wave of a predetermined carrier frequency. In this control method, a control signal is generated using a carrier wave that alternates between two carrier frequencies at predetermined intervals, and the control signal controls a switching device of the power converter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-069213 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control method described in Patent Document 1, harmonics are not dispersed and large ripples occur in specific frequency components, which may increase sound vibrations.

[0005] On the other hand, if three or more carrier frequencies are used to generate a control signal, it is possible to disperse the harmonics, but this increases the computational load on the microcontroller and limits the microcontroller's hardware specifications, which may increase costs.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a switching control method and a switching control device that reduce the calculation load on a microcomputer and that reduce noise and vibration. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a switching control method for generating a control signal using a reference wave and a carrier wave, and controlling a semiconductor switching element that drives a load using the control signal. This switching control method sets a plurality of carrier waves, each of which alternately combines a first carrier frequency and a second carrier frequency different from the first carrier frequency, with different combination patterns of the first carrier frequency and the second carrier frequency. Then, in a predetermined control period of the load, the method switches between at least two carrier waves with different combination patterns of carrier frequencies, and generates a control signal using the at least two switchable carrier waves. [Effects of the Invention]

[0008] According to the present invention, since only two carrier frequencies are used, the calculation load on the microcomputer can be reduced.Furthermore, by setting multiple carrier waves with different combination patterns of two carrier frequencies and switching between carrier waves with different combination patterns of carrier frequencies, harmonics can be dispersed, ripple can be reduced, and sound vibration can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a power conversion system including a switching control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of a switching control device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of a carrier wave in which two carrier frequencies are alternately combined. [Figure 4] FIG. 4 is a diagram showing an example of a carrier wave in which two carrier frequencies are alternately combined. [Figure 5] FIG. 5 is a diagram showing the relationship between the carrier frequency and the control signal in the switching control method of this embodiment. [Figure 6] FIG. 6 is a diagram showing the relationship between the carrier frequency and the control signal in a conventional switching control method. [Figure 7] FIG. 7 is a diagram showing the frequencies of harmonics generated in a conventional switching control method. [Figure 8] FIG. 8 is a diagram showing the frequencies of harmonics generated in the switching control method of this embodiment. [Figure 9] FIG. 9 is a diagram showing the frequency spectrum of a ripple voltage in a conventional switching control method. [Figure 10] FIG. 10 is a diagram showing the frequency spectrum of the ripple voltage in the switching control method according to the present embodiment. [Figure 11] FIG. 11 is a diagram illustrating the relationship between the ratio of the durations of two carrier frequencies and the ripple voltage. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 is a schematic configuration diagram of a power conversion system 100 including a switching control device 10 according to an embodiment of the present invention. The power conversion system 100 is mounted on a vehicle or the like.

[0012] The power conversion system 100 includes a battery 1, a drive motor (load) 2, an inverter 3, a smoothing capacitor 4, and a controller 10 as a switching control device.

[0013] The power conversion system 100 is a system that converts DC power supplied from a battery 1 into AC power and supplies it to a drive motor 2.

[0014] The battery 1 is a DC power supply that supplies electric power to the drive motor 2 via the inverter 3 when the vehicle is driven.

[0015] In this embodiment, the drive motor (load) 2 is an AC motor (three-phase AC motor) driven by three phases, UVW, and is driven by AC power supplied from an inverter 3, which will be described later. The drive motor 2 is provided with current sensors that detect the currents of the U, V, and W phases, and angle sensors such as resolvers that detect the rotation angle (neither of which is shown), and the detected values of these sensors are sent to a vehicle controller, which is not shown. In addition, a torque detection unit, not shown, that detects the motor torque of the drive motor 2 is provided near the drive motor 2, and the detected motor torque is sent to a controller 10, which will be described later.

[0016] The inverter 3 is provided between the positive and negative lines of the battery 1, converts DC power supplied from the battery 1 into AC power, and supplies it to the drive motor 2. The inverter 3 is a switching device having a plurality of semiconductor elements (semiconductor switching elements) 31 with a switching function, and the switching elements 31 are operated in response to control signals output from a controller 10 (described later). The DC power output from the battery 1 is converted into AC power in response to the on / off operation of the switching elements 31, and the converted AC power is supplied to the drive motor 2. In this embodiment, the inverter 3 is configured with upper and lower arms in each of three phases, UVW, and includes six switching elements 31 (UP, UN, VP, VN, WP, WN), and drives the drive motor 2 with three phases and six arms. Note that the configurations of the drive motor 2 and the inverter 3 described above are merely examples and are not limited to this embodiment.

[0017] The smoothing capacitor 4 is provided between the positive and negative lines of the battery 1, in parallel with the inverter 3, on the battery 1 side of the inverter 3. The smoothing capacitor 4 smoothes ripples caused by the operation of the switching element 31 in the inverter 3.

[0018] The controller 10 is a switching control device that controls the switching operation of the switching elements 31 of the inverter 3. The controller 10 is configured to be able to execute a predetermined program using a microcomputer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 10 can also be configured using multiple microcomputers.

[0019] A torque command value, which is the torque required for the drive motor 2, and a rotation speed command value are input to the controller 10 from a higher-level device, a vehicle controller (not shown), and the controller 10 generates a reference sine wave (reference wave) based on the torque command value and the rotation speed command value. The controller 10 also compares the reference sine wave with a carrier wave of a predetermined carrier frequency, generates a control signal (PWM signal) as a signal indicating the magnitude relationship between the reference sine wave and a carrier wave of a predetermined carrier frequency, and outputs the control signal to the inverter 3 to control the switching operation of the switching element 31. The torque command value corresponds to the amplitude of the reference sine wave, and the rotation speed command value corresponds to the period of the reference sine wave.

[0020] As described above, the switching control device (controller) 10 generates a control signal (PWM signal) using a reference wave and a carrier wave, and controls the switching element 31 that drives the drive motor 2 using the control signal.

[0021] There is a known technology that generates a control signal using a carrier wave that alternates between two carrier frequencies at predetermined intervals and controls a switching device using the control signal. However, in this case, harmonics are not dispersed, and large ripples occur in specific frequency components. This can increase noise and vibration. For example, as described below, if a control signal is generated by alternately switching between carrier frequencies of 5 kHz and 10 kHz every 200 μsec, a 2.5 kHz harmonic is generated, causing large ripples in the 7.5 kHz frequency component.

[0022] On the other hand, if a control signal is generated using three or more carrier frequencies to prevent noise from concentrating at a specific frequency, the computational load on the microcontroller increases, limiting the microcontroller's hardware specifications. This could result in increased costs. Furthermore, if software is modified to apply a switching control device using three or more carrier frequencies to a conventional vehicle that uses a binary carrier frequency, the software modification becomes more complex because it requires changes to both the carrier frequency and the carrier frequency switching timing. This also could result in increased costs.

[0023] Therefore, the switching control device 10 of this embodiment executes the following carrier frequency spreading control. That is, first, a plurality of carrier waves are set, each of which alternately combines a first carrier frequency Fc1 and a second carrier frequency Fc2 different from the first carrier frequency Fc1, and each of which has a different combination pattern of the first carrier frequency Fc1 and the second carrier frequency Fc2. Then, in a predetermined motor control period T, at least two carrier waves having different combination patterns of carrier frequencies are switched, and a control signal is generated using the at least two carrier waves to be switched, and the switching element 31 is controlled by the control signal.

[0024] In this way, multiple carrier waves with different combination patterns of the binary carrier frequencies Fc1 and Fc2 are set, and carrier waves with different combination patterns of carrier frequencies are switched between, which disperses harmonics and reduces ripples, thereby reducing sound vibrations.

[0025] Furthermore, since only two carrier frequencies Fc1 and Fc2 are used, the calculation load on the microcomputer can be reduced compared to when three or more carrier frequencies are used.

[0026] Furthermore, when the switching control device 10 of this embodiment is applied to a conventional vehicle that uses a binary carrier frequency, it is only necessary to change the combination pattern of the binary carrier frequencies, which makes it easy to modify the software and reduces costs.

[0027] The switching control device (controller) 10 of this embodiment and the carrier frequency spreading control (switching control) executed by the switching control device 10 will be described in detail below.

[0028] 2 is a block diagram showing details of the switching control device (controller) 10. As shown in FIG. 2, the controller 10 includes a carrier wave setting unit 101, a control signal generating unit 102, and a driving unit 103.

[0029] The carrier wave setting unit 101 sets binary carrier frequencies Fc1 and Fc2 and sets multiple carrier waves with different combination patterns of the binary carrier frequencies Fc1 and Fc2. The carrier wave setting unit 101 first sets a first carrier frequency Fc1 and a second carrier frequency Fc2 that is different from the first carrier frequency Fc1. Next, multiple carrier waves are set that combine the first carrier frequency Fc1 and the second carrier frequency Fc2 and have different combination patterns of the first carrier frequency Fc1 and the second carrier frequency Fc2. For example, first, as the first carrier wave, a carrier wave (carrier wave with a frequency ratio of 1:1) is set that combines the wave duration of the first carrier frequency Fc1 and the wave duration of the second carrier frequency Fc2 shown in FIG. 3 as a combination of both frequencies. Next, as the second carrier wave, a carrier wave (carrier waves with a frequency ratio of 2:1) is set, in which the duration of the wave at the first carrier frequency Fc1 shown in Fig. 4 is 2t and the duration of the wave at the second carrier frequency Fc2 is t. The multiple carrier waves set by the carrier wave setting unit 101 are output to the control signal generating unit 102.

[0030] The control signal generating unit 102 compares a reference sine wave (reference wave) generated based on a torque command value and a rotation speed command value with the carrier wave, and generates a control signal (PWM signal). In a normal state where the torque and modulation rate of the drive motor 2 do not exceed their reference values, the control signal generating unit 102 generates a control signal using a carrier wave of one of the first carrier frequency Fc1 and the second carrier frequency Fc2. In this case, of the two carrier frequencies Fc1 and Fc2, a carrier wave of a frequency lower than the heat generation limit frequency (e.g., 7.5 kHz) of the semiconductor module used in the power conversion system 100 is used. This suppresses heat generation in the semiconductor module and improves the efficiency of the semiconductor module. The reference values of the torque and modulation rate of the drive motor 2 can be set to torque and modulation rate values that may generate noise that is noticeable to vehicle occupants, for example.

[0031] On the other hand, when the torque and modulation rate of the drive motor 2 exceed the reference values, the control signal generator 102 generates a control signal (PWM signal) for the switching element 31 by switching between multiple carrier waves set by the carrier wave setting unit 101 at a predetermined motor control period T. For example, at the predetermined motor control period T, a carrier wave with a frequency ratio of 1:1 and a carrier wave with a frequency ratio of 2:1 are alternately switched to generate a control signal as shown in FIG. 5 using a reference sine wave (reference wave) and a carrier wave generated based on the torque command value and rotation speed command value of the drive motor 2. In this way, by switching between two carrier waves with different frequency ratios to generate a control signal, harmonics are dispersed and ripples are reduced. Note that the predetermined motor control period T is, for example, the period of the reference wave. In FIG. 5, the motor control period T is set to 1000 μsec, the first carrier frequency Fc1 is set to 5 kHz, the second carrier frequency Fc2 is set to 10 kHz, and the minimum duration t of the carrier frequency is set to 200 μsec. As shown in Figure 5, when a carrier wave with a frequency ratio of 1:1 is used, one pulse is applied at 5 kHz and two pulses are applied at 10 kHz. When a carrier wave with a frequency ratio of 2:1 is used, two pulses are applied at 5 kHz and two pulses are applied at 10 kHz.

[0032] The control signal generated in the control signal generating unit 102 is output to the driving unit 103 .

[0033] The drive unit 103 outputs the control signal generated by the control signal generation unit 102 to the inverter 3 to drive the switching elements 31. In this way, the switching operation of each switching element 31 is controlled.

[0034] As described above, the switching control device (controller) 10 generates control signals while switching between carrier waves having different combination patterns of carrier frequencies, and controls the switching element 31 of the inverter 3 by the generated control signals.

[0035] The above-described configuration of the switching control device (controller) 10 is merely an example and is not necessarily limited to this. That is, the switching control device 10 may have any internal detailed configuration as long as it sets multiple carrier waves with different combination patterns of binary carrier frequencies Fc1 and Fc2, switches between the multiple carrier waves to generate control signals, and controls the switching device (inverter) 2 using the control signals.

[0036] Fig. 6 is a diagram showing the relationship between carrier frequencies and control signals when a control signal is generated using a carrier wave in which two carrier frequencies are alternately switched at predetermined intervals (a conventional example), and Fig. 7 is a diagram showing the frequencies of harmonics generated in the conventional example. In Fig. 6, the first carrier frequency Fc1 is 5 kHz, the second carrier frequency Fc2 is 10 kHz, and the minimum duration t of the carrier frequencies is 200 μsec.

[0037] As shown in Figure 6, in the conventional example, the duration of both the first carrier frequency Fc1 and the second carrier frequency Fc2 is t (200 μsec), resulting in a repeating carrier wave with a frequency ratio of 1:1. Therefore, the switching period of the carrier wave combining the first carrier frequency Fc1 and the second carrier frequency Fc2 is 2t (400 μsec). As a result, the frequency component of the control signal in the conventional example is only 2.5 kHz (1 / 400 μsec), and as shown in Figure 7, harmonics are generated at frequencies that are integer multiples of 2.5 kHz. As such, in the conventional example, since the frequency component of the control signal is only 2.5 kHz, large ripples are generated at specific frequency components.

[0038] 8 is a diagram showing the frequencies of harmonics generated in the frequency spreading control (switching control) of this embodiment. As described above, this embodiment alternates between a carrier wave with a frequency ratio of 1:1, in which the duration of the wave at the first carrier frequency Fc1 and the duration of the wave at the second carrier frequency Fc2 are both t (200 μsec), and a carrier wave with a frequency ratio of 2:1, in which the duration of the wave at the first carrier frequency Fc1 is 2t (400 μsec) and the duration of the wave at the second carrier frequency Fc2 is t (200 μsec) (FIG. 5). Therefore, the switching period of the carrier wave combining the first carrier frequency Fc1 and the second carrier frequency Fc2 is 2t (400 μsec) for the carrier wave with a frequency ratio of 1:1, 3t (600 μsec) for the carrier wave with a frequency ratio of 2:1, and 5t (1000 μsec) for the carrier wave combining the carrier wave with a frequency ratio of 1:1 and the carrier wave with a frequency ratio of 2:1. Therefore, the frequency components of the control signal are dispersed to 2.5 kHz (1 / 400 μsec), 1.67 kHz (1 / 600 μsec), and 1.0 kHz (1 / 1000 μsec), and harmonics are generated at integer multiples of these frequencies, as shown in FIG.

[0039] In this way, by using multiple carrier waves with different ratios of duration between the first carrier frequency Fc1 and the second carrier frequency Fc2, it is possible to disperse the harmonics generated from the carrier wave of the first carrier frequency Fc1 and the harmonics generated from the carrier wave of the second carrier frequency Fc2, thereby reducing ripple.

[0040] Fig. 9 shows the frequency spectrum of the ripple voltage generated in a conventional switching control method. Meanwhile, Fig. 10 shows the frequency spectrum of the ripple voltage generated in the switching control method (spread spectrum control) of this embodiment. The vertical axis of Figs. 9 and 10 represents the magnitude of the ripple voltage, and the horizontal axis represents the frequency. Region R in Figs. 9 and 10 is the audible region. Note that the magnitude of the ripple voltage can vary depending on the torque and rotation speed of the drive motor 2, but these conditions are set to be the same in Figs. 9 and 10.

[0041] As mentioned above, in the conventional example using a carrier wave that repeats carrier frequencies of 5 kHz and 10 kHz at a frequency ratio of 1:1, harmonics are generated at frequencies that are integer multiples of 2.5 kHz. In this case, as shown in Figure 9, a large ripple occurs at the harmonic frequency component of 7.5 kHz.

[0042] On the other hand, in this embodiment, which uses a carrier wave that switches between carrier frequencies of 5 kHz and 10 kHz at a frequency ratio of 2:1 instead of 1:1, harmonics generated from the 5 kHz carrier wave and harmonics generated from the 10 kHz carrier wave are dispersed. That is, harmonics are generated at frequencies that are integer multiples of 2.5 kHz, 1.67 kHz, and 1.0 kHz. Because the harmonics are dispersed in this manner, in this embodiment, the ripple at the 7.5 kHz harmonic frequency component is reduced compared to the conventional example, as shown in FIG. 10.

[0043] When a carrier wave that alternates between carrier frequencies of 5 kHz and 10 kHz at a frequency ratio of 1:1 is used (conventional example), the average frequency is 7.5 kHz. On the other hand, when a carrier wave that switches between carrier frequencies of 5 kHz and 10 kHz from a frequency ratio of 1:1 to a frequency ratio of 2:1 is used (this embodiment), the average frequency is 7 kHz. Therefore, for example, if the frequency that is the heat generation limit of the semiconductor module used in power conversion system 100 is 7.5 kHz, this embodiment can suppress the average frequency to a value lower than the heat generation limit frequency of the semiconductor module.

[0044] As described above, in this embodiment, harmonics are dispersed and large ripples are prevented from occurring in specific frequency components, thereby reducing sound vibrations.

[0045] The specific values of the motor control period T, the first carrier frequency Fc1, the second carrier frequency Fc2, and the minimum duration t of the carrier frequency used above are merely examples and are not limited to these.

[0046] Furthermore, in this embodiment, an example has been described in which 7.5 kHz ripple is reduced using a carrier wave whose frequency ratio is switched from 1:1 to 2:1, but the frequency components of the reduced ripple and the degree of reduction will vary by changing the frequency ratio of the multiple carrier waves set in the switching control device 10. The frequencies at which noise generated in a vehicle inverter or the like is likely to propagate to vehicle occupants vary depending on the vehicle, so the switching control device 10 (carrier wave setting unit 101 and control signal generating unit 102) sets the frequency ratios of the multiple carrier waves based on the frequency characteristics of the vehicle. This makes it possible to efficiently reduce noise at frequencies that are likely to propagate, improving occupant comfort.

[0047] Figure 11 shows the relationship between the ratio of the durations of the two carrier frequencies Fc1 and Fc2 (frequency ratio) and the ripple voltage. It also shows the simulation results of the frequency spectrum of the ripple voltage when the frequency ratio is varied. The vertical axis of Figure 11 represents the magnitude of the ripple voltage, and the horizontal axis represents the frequency. Figure 11 (a) shows the simulation results when the frequency ratio is repeatedly changed to 1:1. Figure 11 (b) shows the simulation results when the frequency ratio is switched between 1:1 and 2:1, (c) shows the simulation results when the frequency ratio is switched between 1:1 and 3:1, (d) shows the simulation results when the frequency ratio is switched between 3:1 and 1:2, and (e) shows the simulation results when the frequency ratio is switched between 2:1 and 1:2. In Figure 11, the first carrier frequency Fc1 is 5 kHz, the second carrier frequency Fc2 is 10 kHz, and the minimum duration t of the carrier frequency is 200 μsec.

[0048] As shown in FIG. 11, when the frequency ratio is repeatedly set to 1:1 (a), large ripples occur at frequencies such as 2.5 kHz and 7.5 kHz. On the other hand, when the frequency ratio is switched between 1:1 and 2:1 (b), when the frequency ratio is switched between 1:1 and 3:1 (c), when the frequency ratio is switched between 3:1 and 2:1 (d), and when the frequency ratio is switched between 2:1 and 1:2 (e), the 7.5 kHz ripple is reduced. Also, as shown in FIG. 11, the frequency and magnitude of the ripple voltage vary depending on the frequency ratio and its switching pattern. That is, the frequency components of the ripple that are reduced and the degree of reduction vary depending on the frequency ratio and its switching pattern. Therefore, as described above, the switching control device 10 sets the frequency ratios of multiple carrier waves based on the vehicle's frequency characteristics so as to efficiently reduce ripples at desired frequencies.

[0049] Furthermore, the average frequency of the carrier waves varies depending on the frequency ratio and its switching pattern. For example, when three or more carrier frequencies are used, if a high frequency is selected, the average frequency becomes high, which may exceed the heat generation limit of the semiconductor module used in the power conversion system 100. In contrast, in this embodiment, the frequency ratio of the multiple carrier waves can be set so that the average frequency of the carrier waves is lower than the frequency that is the heat generation limit of the semiconductor module used in the power conversion system 100. In other words, even if one of the binary carrier frequencies Fc1, Fc2 is relatively high, adjusting the frequency ratio can make the average frequency lower than the frequency that is the heat generation limit of the semiconductor module. This suppresses heat generation in the semiconductor module and improves the efficiency of the semiconductor module.

[0050] According to the switching control device 10 of the above embodiment, the following effects can be obtained.

[0051] The switching control device 10 sets multiple carrier waves, each of which alternates between a first carrier frequency Fc1 and a second carrier frequency Fc2 different from the first carrier frequency Fc1, with different combination patterns of the first carrier frequency Fc1 and the second carrier frequency Fc2. Then, at a predetermined motor control period T, the device switches between two carrier waves with different carrier frequency combination patterns and generates a control signal using the two switchable carrier waves. In this way, multiple carrier waves with different combination patterns of binary carrier frequencies Fc1 and Fc2 are set, and switching between two carrier waves with different carrier frequency combination patterns disperses harmonics. This reduces ripple and acoustic vibration. Furthermore, because only binary carrier frequencies Fc1 and Fc2 are used, the computational load on the microcomputer can be reduced compared to when three or more carrier frequencies are used. In other words, a switching control method and a switching control device can be provided that reduce the computational load on the microcomputer and reduce acoustic vibration.

[0052] Furthermore, since only two carrier frequencies Fc1 and Fc2 are used, the switching control device 10 (of this embodiment) can be applied to conventional vehicles that use two carrier frequencies simply by changing the carrier frequency combination pattern. This makes it easier to modify the software when applying it to conventional vehicles, reducing costs.

[0053] The switching control device 10 is configured with a plurality of carrier waves, each having a different ratio (frequency ratio) of duration between the first carrier frequency Fc1 and the second carrier frequency Fc2, and generates a control signal by switching between two carrier waves with different frequency ratios. Generating a control signal by switching between two carrier waves with different frequency ratios in this way disperses harmonics and reduces ripple. Furthermore, using only two carrier frequencies Fc1 and Fc2 reduces the computational load on the microcomputer. In other words, it is possible to provide a switching control method and a switching control device that reduces the computational load on the microcomputer and reduces noise and vibration.

[0054] Furthermore, because the control signal is generated by switching between two carrier waves with different duration ratios (frequency ratios) between the binary carrier frequencies Fc1 and Fc2, even if one of the carrier frequencies is relatively high, adjusting the frequency ratio makes it possible to make the average frequency lower than the frequency that is the heat generation limit of the semiconductor module. This makes it possible to suppress heat generation in the semiconductor module and improve the efficiency of the semiconductor module.

[0055] In a normal state where the torque and modulation rate of the drive motor (load) 2 are below reference values, the switching control device 10 generates a control signal using a carrier wave with only one of the first carrier frequency Fc1 and the second carrier frequency Fc2. On the other hand, when the torque and modulation rate of the drive motor (load) 2 exceed the reference values, the switching control device 10 switches between two carrier waves with different carrier frequency combination patterns at a predetermined motor (load) control period T and generates a control signal using the two carrier waves that are switched. In this way, only when the torque and modulation rate of the drive motor (load) 2 exceed the reference values, i.e., when noise increases, the switching control device 10 generates a control signal using the two carrier waves that are switched, thereby reducing ripple. In addition, in a normal state, the switching control device 10 generates a control signal using only one carrier wave. This reduces the computational load of the microcomputer. Furthermore, in a normal state, the switching control device 10 uses a carrier wave with a frequency lower than the heat generation limit frequency of the semiconductor module used in the system, thereby suppressing heat generation in the semiconductor module. This improves the efficiency of the semiconductor module.

[0056] In the switching control device 10, the ratio of the duration of the first carrier frequency Fc1 to the duration of the second carrier frequency Fc2 is set based on the frequency characteristics of the vehicle, thereby efficiently reducing noise at frequencies that are easily propagated, improving passenger comfort.

[0057] In this embodiment, the control target of the switching control device 10 is the inverter 3, which is a switching device that converts DC to AC, but this is not limited to this. For example, the control target may be a switching device that converts DC to DC, such as a DC-DC converter.

[0058] Furthermore, in this embodiment, the torque of the drive motor 2 is detected by the torque detection unit, but this is not limitative, and the torque of the drive motor 2 may be determined from the current value of the drive motor 2 or the like.

[0059] Furthermore, in this embodiment, a control signal is generated by switching between two carrier waves with different carrier frequency combination patterns, but the number of carrier waves that can be switched is not limited to two. For example, a control signal may be generated by switching between carrier waves with a frequency ratio of 1:1, carrier waves with a frequency ratio of 2:1, and carrier waves with a frequency ratio of 3:1 in that order. In other words, a control signal may be generated by switching between three or more carrier waves.

[0060] In addition, in this embodiment, when the torque and modulation rate of the drive motor 2 exceed the reference values, the frequency spread control is executed to generate a control signal while switching between multiple carrier waves, but the conditions for starting the frequency spread control are not necessarily limited to this. In other words, the conditions for executing the frequency spread control can be set arbitrarily.

[0061] Furthermore, as in this embodiment, it is preferable to set the frequency ratio of the binary carrier frequencies Fc1 and Fc2 for the multiple carrier waves based on the frequency characteristics of the vehicle, but this is not necessarily limited to this. If the frequency ratio of the binary carrier frequencies Fc1 and Fc2 is set so that harmonics are dispersed, ripples are reduced compared to conventional examples, and sound vibrations are reduced.

[0062] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0063] 1, battery, 2, drive motor (load), 3, inverter, 10, switching control device (controller), 31, switching element (semiconductor element, semiconductor switching element).

Claims

1. A switching control method for generating a control signal using a reference wave and a carrier wave, and controlling a semiconductor switching element that drives a load using the control signal, comprising: a plurality of carrier waves each having a first carrier frequency and a second carrier frequency different from the first carrier frequency, the plurality of carrier waves having different combination patterns of the first carrier frequency and the second carrier frequency; In a predetermined control period of the load, switching between at least two of the carrier waves having different combination patterns of carrier frequencies, and generating the control signal using the at least two carrier waves to be switched; a ratio of durations of the first carrier frequency and the second carrier frequency of the plurality of carrier waves is set based on frequency characteristics of a vehicle; Switching control method.

2. 2. The switching control method according to claim 1, The plurality of carrier waves each have a different ratio of duration of the first carrier frequency to the second carrier frequency. Switching control method.

3. 3. The switching control method according to claim 1 or 2, In a normal state in which the torque and modulation rate of the load are equal to or less than reference values, the control signal is generated using a carrier wave having only one of the first carrier frequency and the second carrier frequency; When the torque and modulation rate of the load exceed the reference values, at least two of the carrier waves having different combination patterns of carrier frequencies are switched in a predetermined control period of the load, and the control signal is generated using the at least two carrier waves that are switched. Switching control method.

4. A switching control device that controls a semiconductor switching element that drives a load using a control signal generated by using a reference wave and a carrier wave, a carrier wave setting unit that sets a plurality of carrier waves in which a first carrier frequency and a second carrier frequency different from the first carrier frequency are alternately combined, and in which the combination patterns of the first carrier frequency and the second carrier frequency are different; a control signal generating unit that switches between at least two carrier waves having different combination patterns of carrier frequencies in a predetermined motor control period and generates the control signal using the at least two carrier waves that are switched; a driver that controls the switching operation of the semiconductor switching element using the control signal; the carrier wave setting unit and the control signal generating unit set a ratio of durations of the first carrier frequency and the second carrier frequency based on frequency characteristics of a vehicle in setting the plurality of carrier waves; Switching control device.

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