Switching control device and power conversion device

Abstract

A switching control device (1) is a device that controls a switching operation performed by a switching element (5), and includes: a frequency setting unit (2) that sets at least a first carrier frequency and a second carrier frequency; a phase shift setting unit (3) that sets a phase difference between a first switching square wave determined by the first carrier frequency set by the frequency setting unit (2) and a second switching square wave determined by the second carrier frequency set by the frequency setting unit (2); and a control signal generation unit (4) that controls the switching operation performed by the switching element (5) based on the phase difference set by the phase shift setting unit (3).

Description

Area

[0001] The present disclosure relates to a switching control device that controls a switching operation of a switching element and a power conversion device. background

[0002] In a power conversion device that performs power conversion based on the switching operation of a switching element, when switching is performed at a specific switching frequency, electromagnetic noise with a specific frequency and harmonic components of the frequency are generated. Electromagnetic noise standards are set based on product classification, and countermeasures are required when electromagnetic noise exceeds an upper limit specified in the standards. As a general countermeasure, a noise filter including a noise-reducing component such as a reactor or capacitor may be used. However, in such a case, device size and cost increase are problems.To solve these problems, a power conversion device including a frequency change device that repeatedly outputs a frequency change pattern including a plurality of frequency values ​​and a controller that controls the on / off of a switching element at a switching frequency according to the frequency change pattern output by the frequency change device has been conventionally proposed (see, for example, Patent Literature 1). A power conversion device that sets a period of a frequency change pattern to achieve a noise reduction effect even under different measurement conditions and detection methods has also been proposed (see, for example, Patent Literature 2). List of citationsPatent literature Patent Literature 1: Japanese Patent Application Laid-Open No. 2006-288103 Patent Literature 2: Japanese Patent Application Laid-Open No. 2016-19322 Brief description of the inventionProblem to be solved by the invention

[0003] Conventional power conversion devices reduce electromagnetic noise by using a variety of switching frequencies, but depending on the measurement conditions, sufficient noise reduction cannot be achieved. Therefore, a technique for achieving a noise reduction effect under more diverse measurement conditions is required.

[0004] The present disclosure has been developed in view of the foregoing, and an object thereof is to provide a switching control device capable of obtaining a noise reduction effect under more diverse measurement conditions. Ways to solve the problem

[0005] In order to solve the above-described problem and achieve the object, a switching control device according to the present disclosure is a switching control device that controls a switching operation performed by a switching element, and includes: a frequency setting unit that sets at least a first carrier frequency and a second carrier frequency; a phase shift setting unit that sets a phase difference between a first switching rectangular wave determined by the first carrier frequency set by the frequency setting unit and a second switching rectangular wave determined by the second carrier frequency set by the frequency setting unit; and a control unit that controls the switching operation performed by the switching element based on the phase difference set by the phase shift setting unit. Effects of the invention

[0006] The switching control device according to the present disclosure achieves an effect that it is possible to obtain a noise reduction effect under more diverse measurement conditions. Short description of the drawings Fig. 1 is a diagram illustrating a configuration of a shift control device according to a first embodiment. Fig. 2 is a diagram illustrating an example of a timing waveform of a switching rectangular wave in a control signal output from a control signal generating unit included in the switching control device according to the first embodiment. Fig. 3 is a diagram illustrating an example of a time waveform of a switching square wave in a case where the switching square wave is fixed. Fig. 4 is a diagram illustrating a time waveform of a switching square wave in a case where there is no phase shift, two kinds of carrier frequencies are set, and only the carrier frequency is variable. Fig. 5 is a diagram illustrating a frequency characteristic of electromagnetic noise in a case where the switching control device according to the first embodiment is used and a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed, in comparison with each other. Fig. 6 is a diagram illustrating a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed and a frequency characteristic of electromagnetic noise in the case where only the carrier frequency is variable, in comparison with each other. Fig. 7 is a diagram illustrating a time waveform of a switching square wave. Fig. Figure 8 is a diagram illustrating a phase of a composite vector of two terms determined by switching times of a particular carrier frequency on a complex plane. Fig. Figure 9 is a diagram illustrating a phase of a composite vector of two terms determined by switching times of a different specific carrier frequency on the complex plane. Fig. 10 is a diagram for explaining a spectrum calculation method in the short-time Fourier transform. Fig. 11 is a diagram illustrating a configuration of a power conversion device according to a second embodiment. Fig. 12 is a diagram illustrating a configuration of a power conversion device according to a third embodiment. Fig. 13 is a diagram illustrating an example of a timing waveform of a switching rectangular wave in a control signal output from the control signal generation unit included in a switching control device according to a fourth embodiment. Fig. Figure 14 is a diagram illustrating three phase differences on the complex plane. Fig. 15 is a diagram illustrating an example of a time waveform of a switching rectangular wave in a case where a frequency is variable. Fig. 16 is a diagram illustrating an example of a time waveform of a switching square wave in a case where the frequency is fixed. Fig. 17 is a diagram illustrating a frequency characteristic of electromagnetic noise in a case where the switching control device according to the fourth embodiment is used and a frequency characteristic of electromagnetic noise in a case where the switching rectangular wave is fixed, in comparison with each other. Fig. 18 is a diagram illustrating a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed and a frequency characteristic of electromagnetic noise in a case where only a carrier frequency is variable, in comparison with each other. Fig. 19 is a diagram illustrating a processor in a case where at least part of a frequency setting unit, a phase shift setting unit, and the control signal generation unit included in the switching control device according to the first embodiment is implemented by the processor. Fig. 20 is a diagram illustrating a processing circuit in a case where at least part of the frequency setting unit, the phase shift setting unit, and the control signal generation unit included in the switching control device according to the first embodiment is implemented by the processing circuit. Description of embodiments

[0007] Hereinafter, a switching control device and a power conversion device according to each embodiment will be described in detail with reference to the drawings. First embodiment.

[0008] Fig. 1 is a diagram illustrating a configuration of a switching control device 1 according to a first embodiment. The switching control device 1 is a device that controls a switching operation performed by a switching element 5 and includes a frequency setting unit 2 that sets two types of carrier frequencies f1 and f2 and a frequency change period T, which is a period in which the carrier frequencies change. The switching element 5 is included, for example, in a power conversion circuit included in a power conversion device.

[0009] The switching control device 1 further includes a phase shift adjustment unit 3 that adjusts a phase difference Δφ between a switching square wave determined by the carrier frequency f1 adjusted by the frequency adjustment unit 2 and a switching square wave determined by the carrier frequency f2 adjusted by the frequency adjustment unit 2. With the frequency change period T set by the frequency adjustment unit 2, a period of which is 2π, the phase difference Δφ is defined as a difference between an interval between an on-time and an off-time of the switching square wave determined by the carrier frequency f1 and an interval between an on-time and an off-time of the switching square wave determined by the carrier frequency f2.

[0010] The switching control device 1 further includes a control signal generation unit 4 that generates a control signal for controlling the switching operation performed by the switching element 5 based on the settings made by the frequency adjustment unit 2 and the phase shift adjustment unit 3. The control signal generation unit 4 is an example of a control unit. The frequency adjustment unit 2 adjusts the carrier frequency f1 and the carrier frequency f2, and the phase shift adjustment unit 3 adjusts the phase difference Δφ to reduce the switching noise of the harmonic components when the switching element 5 performs the switching operation.

[0011] In a specific example in the first embodiment, the frequency setting unit 2 sets two types of carrier frequencies f1=15 kHz and f2=30 kHz and sets the frequency change period T=100 μs. In addition, the frequency setting unit 2 sets a duty ratio D=0.5, where the duty ratio is a ratio of the on-time over a switching period. The phase shift setting unit 3 sets a phase shift amount Δφ=0.913 π to reduce the noise of a harmonic component around 460 kHz. The phase shift amount Δφ is the phase difference Δφ described above.That is, the frequency setting unit 2 sets a first carrier frequency f1, a second carrier frequency f2, the frequency change period T and the duty cycle D depending on a harmonic component for which noise suppression is desired, and the phase shift setting unit 3 sets the phase difference Δφ depending on the harmonic component.

[0012] Fig. 2 is a diagram illustrating an example of a timing waveform of a switching rectangular wave in a control signal output from the control signal generating unit 4 included in the switching control device 1 according to the first embodiment. Fig. 2 illustrates a time waveform of a switching rectangular wave in a control signal output from the control signal generating unit 4 in a case where the above-described specific numerical values ​​are set. Fig. 3 is a diagram illustrating an example of a time waveform of a switching square wave in a case where the switching square wave is fixed. Fig. 3 is a diagram for comparison with Fig. 2 and a fixed switching frequency f=20 kHz is used in Fig. 3. The fixed switching frequency f=20 kHz is selected to make the number of switching operations equivalent to the number of switching operations in a case where the two kinds of carrier frequencies in Fig. 2 f1=15 kHz and f2=30 kHz, which makes a switching loss condition comparable. As can be seen by comparing Fig. 2 with Fig. 3, the switching control device 1 outputs from the control signal generation unit 4 to the switching element 5 not a control signal having a rectangular wave in which an on-time is repeatedly generated at a certain interval, but a control signal having a rectangular wave in which on-times, each associated with one of the inverses of two different frequencies, are repeatedly generated. In the specific example in the first embodiment, the two different frequencies are a carrier frequency of 15 kHz and a carrier frequency of 30 kHz. Fig. Figure 4 is a diagram illustrating a time waveform of a switching square wave in a case where there is no phase shift, two types of carrier frequencies f1=15 kHz and f2=30 kHz are set, and only the carrier frequency is variable. In each of the Fig. 2 to 4, the horizontal axis represents time and the vertical axis represents voltage.

[0013] Fig. 5 is a diagram illustrating a frequency characteristic of electromagnetic noise in a case where the switching control device 1 according to the first embodiment is used and a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed, in comparison with each other. Fig. 5 is a representation consisting of the Fig. 2 and Fig. 3 is obtained. Fig. 6 is a diagram illustrating a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed and a frequency characteristic of electromagnetic noise in the case where only the carrier frequency is variable, in comparison with each other. Fig. 6 is a representation of the Fig. 3 and Fig. 4 is obtained. In each of the Fig. 5 and Fig. In FIG. 6, the horizontal axis represents the frequency, and the vertical axis represents the noise level. The switching control device 1 outputs to the switching element 5 a control signal comprising a square wave in which on-times associated with each of the inverses of two different frequencies are repeatedly generated. In the specific example in the first embodiment, the two different frequencies are a carrier frequency of 15 kHz and a carrier frequency of 30 kHz.

[0014] It can be seen that, as in Fig. 5 illustrates that the noise in a certain range in a band from 400 kHz to 600 kHz, including 460 kHz, is reduced in the case where the two types of carrier frequencies f1 and f2 are set, compared to the case where the carrier frequency is fixed. On the other hand, as shown in Fig. As illustrated in FIG. 6, in the case where the carrier frequency is variable, a harmonic component in which the noise is locally reduced is also observed, but the noise of a harmonic component around 460 kHz is not reduced, and a sufficient noise reduction effect is not obtained with a certain bandwidth. Since an upper limit in electromagnetic noise standards is generally defined in a certain bandwidth, a method in which the switching control device 1 according to the first embodiment sets the two kinds of carrier frequencies f1 and f2, the frequency change period T, and the phase difference Δφ is effective in judging the upper limit in the standards.

[0015] Δφ=0.913π of the first embodiment is merely an example, and there are a variety of phase difference solutions that can reduce noise at 460 kHz, which will be expressed in formula (4) and described later. Although the noise reduction at 460 kHz was described as an example, the frequency at which the noise is reduced is not limited to 460 kHz. For example, the switching control device 1 can reduce noise in a band where electromagnetic noise has a maximum value at a circular resonance.

[0016] In the first embodiment, a switching square wave is determined by using a variable frequency and a phase shift under a condition that a duty ratio is fixed. Even if it is interpreted that a variable frequency and a variable duty ratio are used under a condition that a phase is fixed, it is possible to define a switching square wave similar to the switching square wave determined using the variable frequency and the phase shift under the condition that the duty ratio is fixed.

[0017] The frequency change period T=1 / f1+1 / f2 is determined from the sum of the inverses of the respective frequencies, but as described later, the frequency change period T can be set to be shorter than a time width determined by an inverse of a resolution bandwidth. The two types of carrier frequencies can be determined from the frequency change period T. The carrier frequencies can be determined by considering some or all of the hardware limitations, such as the performance of the switching element 5, the loss of a passive component, and an upper limit for heat, and limitations of a microcomputer, or can be determined comprehensively by considering the influence of a harmonic on a band of a different order.

[0018] A specific method for determining the phase difference Δφ is described below. Fig. 7 is a diagram illustrating a time waveform of a switching square wave. Fig. Figure 7 illustrates the concept of a switching square wave. A harmonic noise component A n The switching square wave can be calculated by Fourier series expansion of a time waveform f(t) of the switching square wave, as expressed by the following formula (1). f(t) is a function where f(t) = 1 only when the time t between t 1,on and t 1,off and if the time t between t 2,on and t 2,off and f(t)=0 otherwise. Time t 1,on is a time at which the switching square wave is switched on by the carrier frequency f1, time t 1,off is a time at which the switching square wave is switched off by the carrier frequency f1, time t 2,on is a time at which the switching square wave is switched on by the carrier frequency f2, and time t 2,offis a time at which the switching square wave is switched off by the carrier frequency f2. Formula 1: An=1T∫−T / 2T / 2f(t)e−i2nntTdt=i2πn(e−i2πnt1,offT−e−i2πnt1,onT+e−i2πnt2,offT−e−i2πnt2,onT) f(t)={1(t1,on≤t≤t1,off, t2,on≤t≤t2,off)0 (otherwise)

[0019] From formula (1) it can be seen that the harmonic noise component A n using two terms exp{-i×(2πnt 1,off ) / T} and exp{-i×(2πnt 1,on ) / T}, which is determined by the switching times t 1,on and t 1,off the carrier frequency f1, and two terms exp{-i× (2πnt 2,off ) / T} and exp{-ix (2πnt 2,on ) / T}, which is determined by the switching times t 2,on and t 2,offThe noise can be expressed as a function of the carrier frequency f2. The noise can be reduced by selecting the phase difference so that the absolute value of the sum of the two terms is reduced. Since the coefficients of the respective terms are equal, it is sufficient to consider a phase relationship between the respective terms on a complex plane. Fig. Figure 8 is a diagram illustrating a phase φ1 of a composite vector of two terms separated by switching times t 1,on and t 1,off the carrier frequency f1 on the complex plane. In Fig. 8 is the time t 1,on a reference and the time t 1,on =0. A relationship between the phase φ1 and each variable is expressed by the following formula (2). For example, the switching control device 1 sets the switching time t 1,on the carrier frequency f1 as a reference time, that is time t 1,on =0, for formulas (1) and (2). Formula 2: ϕ1=−πnt1,onT+π2−πnt1,offT

[0020] Fig. Figure 9 is a diagram illustrating a phase φ2 of a composite vector of two terms separated by switching times t 2,on and t 2,off the carrier frequency f2 on the complex plane. A relationship between the phase φ2 and each variable is expressed by the following formula (3). Formula 3: ϕ2=−πnt2,onT+π2−πnt2,offT

[0021] A condition where the harmonic noise component A n decreases, is that the composite vector of two terms determined by the switching times t 1,on and t 1,off the carrier frequency f1, and the composite vector of two terms determined by the switching times t 2,on and t 2,offthe carrier frequency f2 cancel each other out on the complex plane. That is, as expressed by the following formula (4), it is sufficient that a phase difference between the phase φ1 and the phase φ2 is shifted by an odd multiple of π. In a broader sense, it is sufficient that the phase difference between the phase φ1 and the phase φ2 is between π / 2 and 3π / 2, as expressed by the following formula (5). k is an integer of 1 or more. That is, in order to compensate for the harmonic noise component A n , the switching control device 1 approximates the phase difference between the phase φ1 of the composite vector of the two terms determined by the switching times t 1,on and t 1,off the carrier frequency f1 on the complex plane, and the phase φ2 of the composite vector of the two terms determined by the switching times t 2,on and t 2,offthe carrier frequency f2 on the complex plane, to a value as close as possible to an odd multiple of π. In the first embodiment, n=46 is set to reduce the noise at 460 kHz in the frequency change period T=100 µs. Although the phase difference Δφ=0.913 π is set to reduce the noise in a band with a certain range around 460 kHz, the phase difference Δφ=0.913 π may be set in a case where it is desired to reduce the noise at 460 kHz in a narrower band. Formula 4: |ϕ2−ϕ1|=(2k−1)π Formula 5: π2+2kπ<|ϕ2−ϕ1|<3π2+2kπ

[0022] As expressed by formulas (2) and (3), the phase φ1 and the phase φ2 involve a term of π / 2, however, in a case where a relative phase difference of the phase difference Δφ=|φ1-φ2| is considered, (t 1,on +t 1,off ) / 2 and (t 2,on+t 2,off ) / 2 is important. That is, it is sufficient to consider a time difference between an interval between an on-time and an off-time of a certain switching square wave and an interval between an on-time and an off-time of the next switching square wave.

[0023] In the first embodiment, a phase shift amount is the phase difference Δφ, however, the phase shift amount may be defined by a time difference Δt. For example, assume that in the first embodiment, the on-time t 1,on the carrier frequency f1 is set as the reference time, that is, t 1,on=0, then an on-state is switched to an off-state after the time D / f1 corresponding to the duty cycle has elapsed, then the on-time of the carrier frequency f2 is set to 1 / f1+Δt and the on-state is switched to the off-state after the time D / f2 corresponding to the duty cycle has elapsed from the on-time of f2, the respective times can be written as t 1,on =0, t 1,off =D / f1, t 2,on =1 / f1+Δt and t 2,off =1 / f1+Δt+D / f1. Therefore, from formulas (2), (3), and (4), Δt can be expressed as the following formula (6). Formula 6: Δt=2k−12nT−2−Df1−Df2

[0024] At this time, when n=46, k=61 and D=0.5 in the first embodiment, a time difference corresponding to Δφ=0.913 π is Δt=14.8 µs. Here, the time t 2,on shifted, however, any of the times t 1,on , t 1,off , t 2,on and t 2,offas long as a relative phase difference can be set. Regarding the switching time, the time t 1,on the carrier frequency f1 does not need to be set as the reference time, and it is sufficient that the relative phase difference Δφ can be adjusted to obtain the noise reduction effect.

[0025] Next, a relationship between various detection methods and a noise reduction effect is described. The detection methods include peak detection, quasi-peak detection, and average detection. A spectrum calculation method related specifically to peak detection with severe conditions for achieving noise reduction is explicitly presented, and it is described that the noise reduction effect can be widely achieved depending on various measurement conditions by the present disclosure. Fig. 10 is a diagram for explaining a spectrum calculation method in short-time Fourier transform. In short-time Fourier transform used in an electromagnetic interference (EMI) receiver or the like, with respect to a time waveform acquired at a certain measurement time, a portion of the time waveform is cut out by a window function and subjected to a fast Fourier transform (FFT) to thereby acquire a spectrum in the portion. Portions to be cut out by the window function as described above are shifted one by one to acquire a plurality of spectra.A peak value of each of the plurality of spectra is extracted, which is a spectrum obtained by peak detection, and an average value thereof is calculated, which is a spectrum obtained by average detection. In a case where the spectral shapes of the plurality of spectra acquired by shifting the portions to be cut out by the window function gradually differ greatly from each other, the peak value of each of the plurality of spectra is referred to, making it difficult to achieve the noise reduction effect in peak detection.Therefore, a method is also proposed in which a frequency change period is made shorter than a window function width Tw, thereby reducing a difference in the spectral shapes obtained in each section, and thus obtaining the noise reduction effect in peak detection, as described in Patent Literature 2. However, as described in the first embodiment, the noise reduction effect cannot be sufficiently obtained if fewer switching pulses enter a window function. The switching control device 1 according to the first embodiment reduces the noise in a harmonic component of a specific order by combining a variable frequency and a phase shift, and can effectively obtain the noise reduction effect even in a situation where noise reduction is difficult, as described above.In a broader sense, the frequency setting unit 2 sets the two kinds of carrier frequencies f1 and f2 and the frequency change period T, that is,a period in which the carrier frequencies change depending on the harmonic component of the specific order, the phase shift setting unit 3 sets the phase difference Δφ between the switching square wave determined by the carrier frequency f1 set by the frequency setting unit 2 and the switching square wave determined by the carrier frequency f2 set by the frequency setting unit 2, and the control signal generation unit 4 outputs the control signal for controlling the switching operation performed by the switching element 5 based on the settings made by the frequency setting unit 2 and the phase shift setting unit 3, so that the switching control device 1 can effectively reduce noise in the harmonic component of the specific order even in the situation where noise reduction is difficult.

[0026] The window function width Tw is determined by the inverse of the resolution bandwidth (RBW) and takes on different values ​​depending on the standard or band of interest. Representative values ​​of the resolution bandwidth include 200 Hz, 1 kHz, 9 kHz, 10 kHz, 120 kHz, and 1 MHz. Specifically, the resolution bandwidth ranges from 526 kHz to 1620 kHz, which is an amplitude modulation (AM) radio band where there is a significant problem of electromagnetic noise. 9 kHz or 10 kHz is defined as the resolution bandwidth.

[0027] In the first embodiment, since T=100 µs, the window function width Tw determined by the inverse of RBW=9 kHz is 111 µs, or the window function width Tw determined by the inverse of RBW=10 kHz is 100 µs or less, so that a sufficient noise reduction effect can be obtained even in the peak detection with RBW=9 kHz and RBW=10 kHz.

[0028] General inverters often use any of carrier frequencies from several kHz to about 20 kHz, and direct current-to-direct current (DC-DC) converters use any of carrier frequencies with a wide range of values ​​from several kHz to several MHz.

[0029] As described above, in the switching control device 1 according to the first embodiment, the frequency adjustment unit 2 adjusts the two types of carrier frequencies f1 and f2, the phase shift adjustment unit 3 adjusts the phase difference Δφ between the switching square wave determined by the carrier frequency f1 adjusted by the frequency adjustment unit 2 and the switching square wave determined by the carrier frequency f2 adjusted by the frequency adjustment unit 2, and the control signal generation unit 4 outputs the control signal for controlling the switching operation performed by the switching element 5 based on the adjustments performed by the frequency adjustment unit 2 and the phase shift adjustment unit 3. Therefore, in the method of the first embodiment, the noise reduction effect can be obtained even in the average detection.

[0030] As a representative detection method other than peak detection and average detection, there is quasi-peak detection, in which a time-constant switching is added to peak detection. In the method of the first embodiment, since a repetition period of switching is sufficiently fast with respect to the time constant, a spectrum substantially similar to that obtained in peak detection is obtained, and an effect similar to that obtained in peak detection is also obtained in quasi-peak detection.

[0031] Even with an instrument using a measurement technique other than the short-time Fourier transform, such as a time-sweep tuned spectrum analyzer, it is possible to expect it to achieve an effect similar to that described above.

[0032] The determination of the phase shift amount requires a complicated calculation, and it is difficult to achieve the effect achieved by the switching control device 1 according to the first embodiment only by simply combining a conventional variable frequency and a conventional phase shift.

[0033] As described above, the switching control device 1 according to the first embodiment includes the frequency setting unit 2 that sets the two kinds of carrier frequencies f1 and f2, the phase shift setting unit 3 that sets the phase difference Δφ between the switching square wave determined by the carrier frequency f1 set by the frequency setting unit 2 and the switching square wave determined by the carrier frequency f2 set by the frequency setting unit 2, and the control signal generation unit 4 that outputs the control signal for controlling the switching operation performed by the switching element 5 based on the settings performed by the frequency setting unit 2 and the phase shift setting unit 3.In the switching control device 1, the frequency adjustment unit 2 adjusts the carrier frequency f1 and the carrier frequency f2, and the phase shift adjustment unit 3 adjusts the phase difference Δφ to reduce the switching noise of the harmonic component when the switching element 5 performs the switching operation. Therefore, the switching control device 1 can achieve a noise reduction effect under a wider range of measurement conditions. Consequently, the switching control device 1 can more effectively reduce the noise in the harmonic component of a specific order by changing the carrier frequencies and phase. Second embodiment.

[0034] Fig. 11 is a diagram illustrating a configuration of a power conversion device 10 according to a second embodiment. The power conversion device 10 includes the switching control device 1 according to the first embodiment and a boost converter circuit 11 connected to a DC power supply 12 and a load 13. The boost converter circuit 11 is an example of a power conversion circuit and includes a reactor 14, a switching element 15, a diode 16, and a smoothing capacitor 17.

[0035] The switching element 15 performs a switching operation in a timed manner according to a control signal output from the control signal generation unit 4 included in the switching control device 1. The boost converter circuit 11 boosts a voltage of input power from the DC power supply 12 and supplies output power of a desired voltage to the load 13. A semiconductor switching element, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT), in which the diode 16 is connected in antiparallel, is used as the switching element 15.

[0036] Since the power conversion device 10 changes a duty cycle depending on the state of the load 13 to achieve a desired voltage, a phase shift amount must also be changed in accordance with the duty cycle. The phase shift amount can be calculated sequentially in accordance with a control state or can be determined based on a pre-calculated table.

[0037] The power conversion circuit may be a different DC / DC converter than the boost converter circuit 11, for example a buck converter circuit. Third embodiment.

[0038] Fig. 12 is a diagram illustrating a configuration of a power conversion device 20 according to a third embodiment. The power conversion device 20 includes the switching control device 1 according to the first embodiment and an inverter circuit 21 connected to a DC power supply 22 and a load 23. The inverter circuit 21 is an example of a power conversion circuit and includes switching elements 24.

[0039] Each switching element 24 performs a switching operation at a timed interval according to a control signal output from the control signal generation unit 4 included in the switching control device 1. The inverter circuit 21 boosts a voltage of input power from the DC power supply 22 and supplies the desired AC output power to the load 23. A semiconductor switching element such as a MOSFET or an IGBT with a diode connected in antiparallel is used as the switching element 24.

[0040] The inverter circuit 21 must also change the phase shift amount in accordance with the pulse width modulation control to achieve a desired inverter output voltage. The phase shift amount can be calculated sequentially according to a control condition or can be determined based on a pre-calculated table.

[0041] The power conversion circuit may be a circuit in which a converter and an inverter are combined in parallel or in series.

[0042] Note that the switching control device 1 according to the first embodiment may be the following switching control device 1. That is, the frequency setting unit 2 may set at least two types of carrier frequencies, and the phase shift setting unit 3 may adjust a phase difference between a switching square wave determined by a first carrier frequency of the two carrier frequencies set by the frequency setting unit 2 and a switching square wave determined by a second carrier frequency thereof.The phase shift adjustment unit 3 can adjust a phase difference between a switching square wave determined by the first carrier frequency of the two carrier frequencies adjusted by the frequency adjustment unit 2, the two carrier frequencies having values ​​adjacent to each other, and a switching square wave determined by the second carrier frequency thereof. The frequency adjustment unit 2 can set m kinds of carrier frequencies and a frequency change period. m is an integer of 2 or more. The control signal generation unit 4 can generate a switching waveform in a control signal by transferring m kinds of carrier frequencies in the frequency change period T. In a case where a phase with φ. i where the phase is based on time t i,on , when a switching square wave is switched on by an i-th frequency fi among the m kinds of carrier frequencies, and time ti,off when the switching square wave is switched off by the i-th frequency fi in the frequency change period T, the phase shift setting unit 3 may set the phase difference such that an absolute value of a phase difference between a phase φ i and a phase φ i+1 π / m or more and 3π / m or less. i is an integer of 1 or more. The phase φ i can be expressed by a formula of φ i =πnt i,on / T+πnt i,off / T. n is an integer of 1 or more and represents the order of a harmonic component for which noise reduction is desired. The phase difference between the phase φ i and the phase φ i+1 can be 2π / m. Fourth embodiment.

[0043] In the first embodiment, the frequency setting unit 2 sets the two types of carrier frequencies f1 and f2 and the frequency change period T, which is a period in which the carrier frequencies change. As described above, the frequency setting unit 2 can set the m types of carrier frequencies and the frequency change period T, which is a period in which the carrier frequencies change. m is an integer of 2 or more. In a fourth embodiment, a switching control device in a case where m is 3 will be described. The switching control device according to the fourth embodiment includes the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4, similarly to the switching control device 1 according to the first embodiment. In the fourth embodiment, differences from the first embodiment will be mainly described.In the second and third embodiments, the shift control device 1 according to the first embodiment may be replaced by the shift control device according to the fourth embodiment.

[0044] Values ​​of parameters in the fourth embodiment are as follows. n=33 T=100 μs f1=20 kHz f2=30 kHz f3=60 kHz φ1=0.75π φ2=1.69π φ3=0.05π Δφ12=φ2−φ1=0.94π Δφ23=φ3−φ2=−1.64π=0.36π Δφ31=φ1−φ3=0.7π

[0045] In the above parameters, n, T, f1, f2, φ1, and φ2 are those described in the first embodiment. f3 represents a third carrier frequency different from f1 and f2. φ3 represents a phase of a composite vector of two terms determined by the switching times t. 3,on and t 3,offthe carrier frequency f3 on the complex plane. Time t 3,an is a time at which a switching square wave is switched on by the carrier frequency f3, and time t 3,off is a time at which the switching square wave is switched off by the carrier frequency f3. Δφ 12 is a phase difference between φ2 and φ1, Δφ 23 is a phase difference between φ3 and φ2 and Δφ 31 is a phase difference between φ1 and φ3. The phase difference is defined in a range from 0 to 2 π.

[0046] In the fourth embodiment, the harmonic noise component A n of the switching square wave is expressed by the following formula (7). A relationship between the phase φ3 and each variable is expressed by the following formula (8). Δφ ijis expressed by the following formula (9). In formula (9), each of i and j is any one of 1, 2, and 3, and i is different from j. In a case where Δφ ij is not present in the range from 0 to 2π, Δφ ij by Δφ ij +2π or Δφ ij -2π, so that Δφ ij in the range from 0 to 2π. Formula 7: An=1T∫−T / 2T / 2ƒ(t)e−2πntTdt=i2πn(e−i2πnt1,offT−e−i2πnt1,onT+e−i2πnt2, offT−e−i2πnt2,onT+e−i2πnt3,offT−e−i2πnt3,onT)ƒ(t)={1(t1,on≤t≤t1,off, t2,on≤t≤t2,off, t3,on≤t≤t3,off, )0(otherwise) Formula 8: ϕ3=πnt3,onT+π2−πnt3,offT Formula 9: Δϕij=ϕj−ϕi

[0047] The switching control device according to the fourth embodiment can reduce the noise of an n-th order harmonic component by reducing the phase difference Δφ 12 , the phase difference Δφ 23 and the phase difference Δφ 31be adjusted so that each of Δφ 12 , Δφ 23 and Δφ 31 corresponds to the following formula (10). Formula 10: π3<Δϕij<π

[0048] Fig. 13 is a diagram illustrating an example of a timing waveform of a switching rectangular wave in a control signal output from the control signal generating unit 4 included in the switching control device according to the fourth embodiment. Fig. 13 is also a diagram explaining the three phase differences of Δφ 12 , Δφ 23 and Δφ 31 . Fig. Figure 14 is a diagram showing the three phase differences of Δφ 12 , Δφ 23 and Δφ 31 illustrated at the complex level. Fig. 15 is a diagram illustrating an example of a time waveform of a switching rectangular wave in a case where a frequency is variable. Fig. Figure 16 is a diagram illustrating an example of a time waveform of a switching square wave in a case where the frequency is fixed. In each of the Fig. 13, Fig. 15 and Fig. 16 the horizontal axis represents time and the vertical axis represents voltage. In Fig. 16, 30 kHz is used as a fixed switching frequency. The fixed switching frequency of 30 kHz is selected to make the number of switching operations equivalent to the number of switching operations by the three types of carrier frequencies in Fig. 13, making a switching loss condition comparable.

[0049] Fig. 17 is a diagram illustrating a frequency characteristic of electromagnetic noise in a case where the switching control device according to the fourth embodiment is used and a frequency characteristic of electromagnetic noise in a case where the switching rectangular wave is fixed, in comparison with each other. Fig. 18 is a diagram illustrating a frequency characteristic of electromagnetic noise in the case where the switching rectangular wave is fixed and a frequency characteristic of electromagnetic noise in a case where only a carrier frequency is variable, in comparison with each other.

[0050] It can be seen that, as in Fig. 17 illustrates that the noise in a certain range in a band from 310 kHz to 400 kHz, including 330 kHz, is reduced in the fourth embodiment, compared to the case where the frequency is fixed. On the other hand, as shown in Fig. As illustrated in Figure 18, in the case where a frequency is variable, a harmonic component of 330 kHz is larger than that in the fourth embodiment. The method of the fourth embodiment is also effective in a case where the noise of a harmonic component of a specific order is reduced.

[0051] Fig. 19 is a diagram illustrating a processor 97 in a case where at least part of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 included in the switching control device 1 according to the first embodiment is implemented by the processor 97. That is, at least part of the functions of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment can be implemented by the processor 97 executing a program stored in a memory 98. The processor 97 is a central processing unit (CPU), a processing system, a computing system, a microprocessor, or a digital signal processor (DSP). Fig. 19 also illustrates memory 98.

[0052] In a case where at least part of the functions of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment are implemented by the processor 97, the at least part of the functions are implemented by a combination of the processor 97 and the software, firmware, or software and firmware. The software or firmware is described as a program and stored in the memory 98. By reading and executing the program stored in the memory 98, the processor 97 implements at least part of the functions of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment.

[0053] In a case where at least part of the functions of the frequency adjusting unit 2, the phase shift adjusting unit 3, and the control signal generating unit 4 of the first embodiment are implemented by the processor 97, the switching control device 1 includes the memory 98 for storing programs with which at least part of the steps performed by the frequency adjusting unit 2, the phase shift adjusting unit 3, and the control signal generating unit 4 are executed as a result. It can also be said that the programs stored in the memory 98 cause a computer to execute at least part of an operation or method performed by the frequency adjusting unit 2, the phase shift adjusting unit 3, and the control signal generating unit 4 of the first embodiment.

[0054] The memory 98 is, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM) or an electrically erasable programmable read-only memory (EEPROM (registered trademark)), a magnetic disk, a flexible disk, an optical disk, a compact disc, a MiniDisc, a digital versatile disc (DVD), or the like.

[0055] Fig.20 is a diagram illustrating a processing circuit 99 in a case where at least part of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 included in the switching control device 1 according to the first embodiment is implemented by the processing circuit 99. That is, at least part of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment can be implemented by the processing circuit 99.

[0056] Processing circuitry 99 is dedicated hardware. Processing circuitry 99 may be, for example, a single circuit, a multi-chip circuit, a programmed processor, a programmed parallel processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof.

[0057] A part of the frequency setting unit 2, the phase shift setting unit 3 and the control signal generation unit 4 of the first embodiment may be implemented by dedicated hardware separated from the rest of the frequency setting unit 2, the phase shift setting unit 3 and the control signal generation unit 4.

[0058] Regarding a plurality of functions of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment, part of the plurality of functions can be implemented by software or firmware, and the remainder of the plurality of functions can be implemented by dedicated hardware. Thus, the plurality of functions of the frequency adjustment unit 2, the phase shift adjustment unit 3, and the control signal generation unit 4 of the first embodiment can be implemented by hardware, software, firmware, or a combination thereof.

[0059] At least part of the functions of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generating unit 4 included in the switching control device according to the fourth embodiment can also be implemented by a processor executing a program stored in a memory or by a processing circuit.

[0060] The configurations described in the above embodiments are merely examples and can be combined with other known technologies, and part of the configurations can be omitted or modified without departing from the essence of the matter. List of reference symbols

[0061] 1 switching control device; 2 Frequency adjustment unit; 3-phase shift adjustment unit; 4 Control signal generating unit; 5, 15, 24 Switching element; 10, 20 Power conversion device; 11 Boost converter circuit; 12, 22 DC power supply; 13, 23 load; 14 reactor; 16 diode; 17 smoothing capacitor; 21 inverter circuit; 97 Processor; 98 Memory; 99 Processing circuit. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2006-288103

[0002] JP 2016-19322

[0002]

Claims

[1] A shift control device that controls a shift operation performed by a shift element, the shift control device comprising: a frequency setting unit for setting at least a first carrier frequency and a second carrier frequency; a phase shift setting unit for setting a phase difference between a first switching square wave determined by the first carrier frequency set by the frequency setting unit and a second switching square wave determined by the second carrier frequency set by the frequency setting unit; and a control unit for controlling the switching operation performed by the switching element based on the phase difference set by the phase shift setting unit. [2] The switching control device according to claim 1, wherein the phase shift adjusting unit adjusts the phase difference to reduce the switching noise of a harmonic component generated by the switching operation. [3] A shift control device according to claim 2, wherein the frequency setting unit sets a first carrier frequency, a second carrier frequency, a frequency change period and a duty cycle depending on the harmonic component and the phase shift adjustment unit adjusts the phase difference depending on the harmonic component. [4] A shift control device according to claim 2, wherein the control unit is a control signal generating unit that generates a control signal for controlling a switching operation performed by the switching element based on settings performed by the frequency setting unit and the phase shift setting unit, and the frequency setting unit sets at least the first carrier frequency and the second carrier frequency to reduce the switching noise of a harmonic component generated by the switching operation. [5] A shift control device according to claim 4, wherein the frequency setting unit sets m types of carrier frequencies and a frequency change period, the control signal generating unit generates a switching waveform in the control signal by transferring the m kinds of carrier frequencies in the frequency change period, and m is an integer of 2 or more. [6] A shift control device according to claim 5, wherein in a case where a phase is defined by φ i is characterized by the phase based on time t i,on , when a switching square wave is switched on by an i-th frequency fi among the m kinds of carrier frequencies, and time t i,off when a switching square wave is switched off by the i-th frequency fi in the frequency change period, the phase shift adjusting unit adjusts the phase difference such that an absolute value of a phase difference between a phase φ i and a phase φ i+1 becomes π / m or more and 3 π / m or less, and i is an integer of 1 or more. [7] A shift control device according to claim 6, wherein the phase φ i by a formula of φ i =πnt i,on / T+πnt i,off / T is defined, n is an integer of 1 or more and represents an order of a harmonic component for which noise reduction is desired, and T denotes the frequency change period. [8] A switching control device according to claim 6 or 7, wherein a phase difference between the phase φ i and the phase φ i+1 2π / m. [9] Switch control device according to one of claims 5 to 8, wherein which is m 2 . [10] A switching control device according to any one of claims 5 to 9, wherein the frequency change period is shorter than a time width determined by an inverse of a resolution bandwidth. [11] The switching control device according to claim 10, wherein the resolution bandwidth is any one of 200 Hz, 1 kHz, 9 kHz, 10 kHz, 120 kHz and 1 MHz. [12] Power conversion device comprising: the shift control device according to one of claims 1 to 11; and a power conversion circuit including a switching element.

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