Switch control device and power conversion device

Abstract

A switching control device (1) for controlling a switching operation performed by a switching element (5) is provided with: a frequency setting unit (2) for setting 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 rectangular wave determined on the basis of the first carrier frequency set by the frequency setting unit (2) and a second switching rectangular wave determined on the basis of the second carrier frequency set by the frequency setting unit (2); and a control signal generation unit (4) for controlling the switching operation of the switching element (5) on the basis of the phase difference set by the phase shift setting unit (3).

Description

Technical Field

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

[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 constant switching frequency, electromagnetic noise is generated at a constant frequency and high harmonic components of that frequency. For each product classification, a standard for electromagnetic noise is determined, and countermeasures need to be taken when the electromagnetic noise exceeds the upper limit value of the standard. As a general countermeasure, a noise filter using noise countermeasure components such as a choke coil or a capacitor is considered, but when using this noise filter, the enlargement of the device and the increase in cost become problems. To improve this problem, a power conversion device has been proposed in the past, which includes: 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 the switching element at the switching frequency according to the frequency change pattern output from the frequency change device (for example, refer to Patent Document 1). A power conversion device has also been proposed that sets the period of the frequency change pattern in order to obtain a noise reduction effect under various measurement conditions and detection methods (for example, refer to Patent Document 2).

[0003] Prior Art Documents

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-288103

[0005] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-19322 Summary of the Invention

[0006] Conventional power conversion devices reduce electromagnetic noise by using multiple switching frequencies, but sometimes do not obtain sufficient noise reduction effects depending on the measurement conditions. Therefore, a technology that can obtain noise reduction effects for more diverse measurement conditions is required.

[0007] The present disclosure has been made in view of the above circumstances, and an object thereof is to obtain a switching control device that can obtain a noise reduction effect for more diverse measurement conditions.

[0008] In order to solve the above problems and achieve the object, the switching control device according to the present disclosure is a switching control device that controls the switching operation of 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 according to the first carrier frequency set by the frequency setting unit and a second switching rectangular wave determined according to the second carrier frequency set by the frequency setting unit; and a control unit that controls the switching operation of the switching element according to the phase difference set by the phase shift setting unit.

[0009] The switching control device according to the present disclosure has an effect of being able to obtain a noise reduction effect for more diverse measurement conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing the configuration of the switching control device according to Embodiment 1.

[0011] Figure 2 It is a diagram showing an example of the time waveform of a switching rectangular wave in a control signal output from a control signal generation unit included in the switching control device according to Embodiment 1.

[0012] Figure 3 It is a diagram showing an example of the time waveform of a switching rectangular wave in a case where the switching rectangular wave is fixed.

[0013] Figure 4 It is a diagram showing the time waveform of a switching rectangular wave in a case where two kinds of carrier frequencies are set without phase shift and only the carrier frequency is variable.

[0014] Figure 5 It is a diagram showing a comparison of the frequency characteristics of electromagnetic noise in a case where the switching control device according to Embodiment 1 is used and the frequency characteristics of electromagnetic noise in a case where the switching rectangular wave is fixed.

[0015] Figure 6 It is a diagram showing a comparison of the frequency characteristics of electromagnetic noise in a case where the switching rectangular wave is fixed and the frequency characteristics of electromagnetic noise in a case where only the carrier frequency is variable.

[0016] Figure 7 It is a diagram showing the time waveform of a switching rectangular wave.

[0017] Figure 8 It is a diagram showing the phase of a composite vector of two terms determined according to the switching time of a certain carrier frequency on the complex plane.

[0018] Figure 9It is a diagram showing the phase of the composite vector of two terms determined according to the switching times of another certain carrier frequency on the complex plane.

[0019] Figure 10 It is a diagram for explaining the calculation method of the spectrum in the short-time Fourier transform.

[0020] Figure 11 It is a diagram showing the structure of the power conversion device according to Embodiment 2.

[0021] Figure 12 It is a diagram showing the structure of the power conversion device according to Embodiment 3.

[0022] Figure 13 It is a diagram showing an example of the time waveform of the switching rectangular wave in the control signal output from the control signal generation unit included in the switching control device according to Embodiment 4.

[0023] Figure 14 It is a diagram showing three phase differences on the complex plane.

[0024] Figure 15 It is a diagram showing an example of the time waveform of the switching rectangular wave in the case where the frequency is variable.

[0025] Figure 16 It is a diagram showing an example of the time waveform of the switching rectangular wave in the case where the frequency is fixed.

[0026] Figure 17 It is a diagram showing a comparison of the frequency characteristics of the electromagnetic noise in the case of using the switching control device according to Embodiment 4 and the frequency characteristics of the electromagnetic noise in the case where the switching rectangular wave is fixed.

[0027] Figure 18 It is a diagram showing a comparison of the frequency characteristics of the electromagnetic noise in the case where the switching rectangular wave is fixed and the frequency characteristics of the electromagnetic noise in the case where only the carrier frequency is variable.

[0028] Figure 19 It is a diagram of the processor showing the case where at least a 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 Embodiment 1 is implemented by a processor.

[0029] Figure 20 It is a diagram of the processing circuit showing the case where at least a 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 Embodiment 1 is implemented by a processing circuit. Detailed Embodiments

[0030] Hereinafter, based on the drawings, the switching control device and the power conversion device according to the embodiments will be described in detail.

[0031] Embodiment 1.

[0032] Figure 1 FIG. 6 is a diagram showing the structure of the switch control device 1 according to Embodiment 1. The switch control device 1 is a device that controls the switching operation performed by the switch 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 the period of change of the carrier frequency. The switch element 5 is included in, for example, a power conversion circuit included in a power conversion device.

[0033] The switch control device 1 further includes a phase shift setting unit 3 that sets a phase difference Δφ between the switching rectangular wave determined by the carrier frequency f1 set by the frequency setting unit 2 and the switching rectangular wave determined by the carrier frequency f2 set by the frequency setting unit 2. The frequency change period T set by the frequency setting unit 2 is set to one period 2π, and the phase difference Δφ is defined as the difference from the middle time between the on and off times of the switching rectangular wave determined by the carrier frequency f1 to the middle time between the on and off times of the switching rectangular wave determined by the carrier frequency f2.

[0034] The switch control device 1 further includes a control signal generation unit 4 that generates a control signal for controlling the switching operation performed by the switch element 5 according to the settings made by the frequency setting unit 2 and the phase shift setting unit 3. The control signal generation unit 4 is an example of a control unit. The frequency setting unit 2 sets the carrier frequency f1 and the carrier frequency f2, and the phase shift setting unit 3 sets the phase difference Δφ in such a way as to reduce the high-order harmonic component switching noise when the switch element 5 performs a switching operation.

[0035] In a specific example of Embodiment 1, 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, which is the ratio of the on-time in one cycle of the switch. The phase shift setting unit 3 sets a phase shift amount Δφ = 0.913π in such a way as to suppress the noise of the high-order harmonic component around 460 kHz. The phase shift amount Δφ is the above-described phase difference Δφ. That is, the frequency setting unit 2 sets the first carrier frequency f1, the second carrier frequency f2, the frequency change period T, and the duty ratio D corresponding to the high-order harmonic component for which noise is desired to be suppressed, and the phase shift setting unit 3 sets the phase difference Δφ corresponding to the high-order harmonic component.

[0036] Figure 2 FIG. 7 is an example of a time waveform of a switching rectangular wave in the control signal output from the control signal generation unit 4 included in the switch control device 1 according to Embodiment 1.

[0037] Figure 2 Shows the time waveform of the switching rectangular wave in the control signal output from the control signal generation unit 4 when the above specific values are set. Figure 3 Is a diagram showing an example of the time waveform of the switching rectangular wave in the case where the switching rectangular wave is fixed. Figure 3 Is used to Figure 2 Compare, and in Figure 3 A fixed switching frequency f = 20 kHz is used. In order to make the switching loss conditions equivalent so that the number of switching times is equal to that in the case where the two carrier frequencies are f1 = 15 kHz and f2 = 30 kHz in Figure 2 , a fixed switching frequency f = 20 kHz is selected. As can be understood when comparing Figure 2 With Figure 3 , the switching control device 1 does not output a control signal having a rectangular wave with an on-time generated repeatedly at regular intervals from the control signal generation unit 4 to the switching element 5, but outputs a control signal having a rectangular wave with an on-time associated with the reciprocals of two different frequencies generated repeatedly. In the specific example in Embodiment 1, the two different frequencies are the carrier frequencies of 15 kHz and 30 kHz. Figure 4 Is a diagram showing the time waveform of the switching rectangular wave in the case where two carrier frequencies f1 = 15 kHz and f2 = 30 kHz are set without phase shift and only the carrier frequency is variable. In Figures 2 to 4 , the horizontal axis represents time and the vertical axis represents voltage.

[0038] Figure 5 Is a diagram showing a comparison of the frequency characteristics of electromagnetic noise in the case of using the switching control device 1 according to Embodiment 1 and the frequency characteristics of electromagnetic noise in the case where the switching rectangular wave is fixed. Figure 5 Is from Figure 2 And Figure 3 Obtained diagram. Figure 6 Is a diagram showing a comparison of the frequency characteristics of electromagnetic noise in the case where the switching rectangular wave is fixed and the frequency characteristics of electromagnetic noise in the case where only the carrier frequency is variable. Figure 6 Is from Figure 3 And Figure 4 Obtained diagram. In Figure 5 And Figure 6 , the horizontal axis represents frequency and the vertical axis represents noise level. The switching control device 1 outputs a control signal having a rectangular wave with an on-time associated with the reciprocals of two different frequencies generated repeatedly to the switching element 5. In the specific example in Embodiment 1, the two different frequencies are the carrier frequencies of 15 kHz and 30 kHz.

[0039] AsFigure 5 As shown, it can be seen that compared with the case where the carrier frequency is fixed, when two carrier frequencies f1 and f2 are set, the noise is reduced with a certain width in the frequency band of 400 kHz to 600 kHz including 460 kHz. On the other hand, as Figure 6 shown, in the case where the carrier frequency is variable, high harmonic components with locally reduced noise are also observed, but the noise of the high harmonic components near 460 kHz is not reduced, and a sufficient noise reduction effect is not obtained in a certain frequency band width. Generally, the standard upper limit value of electromagnetic noise is specified by a certain frequency band width. Therefore, the method of setting two carrier frequencies f1 and f2, the frequency change period T, and the phase difference Δφ in the switching control device 1 according to Embodiment 1 is effective in the evaluation against the standard upper limit value.

[0040] Δφ = 0.913π in Embodiment 1 is just an example. As shown in the following formula (4), there are multiple solutions for the phase difference that can reduce the noise at 460 kHz. The reduction of the noise at 460 kHz has been described as an example before, but the frequency at which the noise is reduced is not limited to 460 kHz. The switching control device 1 can also reduce the noise in the frequency band where the electromagnetic noise takes the maximum value during circuit resonance, for example.

[0041] In Embodiment 1, the switching rectangular wave is determined by using variable frequency and phase shift under the condition that the duty ratio is fixed. Even if it is interpreted as using variable frequency and variable duty ratio under the condition that the phase is fixed, the same switching rectangular wave as the one determined by using variable frequency and phase shift under the condition that the duty ratio is fixed can be specified.

[0042] The frequency change period T = 1 / f1 + 1 / f2 is determined according to the sum of the reciprocals of each frequency. However, as will be described later, the frequency change period T can also be set shorter than the time width determined by the reciprocal of the resolution frequency band width. The two carrier frequencies can also be determined according to the frequency change period T. The carrier frequency can be determined by considering some or all of the hardware constraints such as the performance of the switching element 5, the loss of passive components, and the thermal upper limit, as well as the constraints of the microcomputer. The carrier frequency can also be comprehensively determined by considering the influence of high harmonics on other frequency bands.

[0043] Hereinafter, a specific method for determining the phase difference Δφ will be described. Figure 7 is a diagram showing the time waveform of the switching rectangular wave. Figure 7 shows the concept of the switching rectangular wave. As shown in the following formula (1), the high harmonic noise component A of the switching rectangular wave can be calculated by the Fourier series expansion of the time waveform f(t) of the switching rectangular wave n . f(t) is only at time t as t1，on from 0 to t 1，off During the period from 0 to t and at time t, 2，on from 0 to t 2，off a function where f(t)=1 during this period and f(t)=0 otherwise. Time t 1，on is the time when the switching rectangular wave turns on according to the carrier frequency f1, and time t 1，off is the time when the switching rectangular wave turns off according to the carrier frequency f1, and time t 2，on is the time when the switching rectangular wave turns on according to the carrier frequency f2, and time t 2，off is the time when the switching rectangular wave turns off according to the carrier frequency f2.

[0044] [Equation 1]

[0045]

[0046] As can be seen from Equation (1), two terms exp{-i×(2πnt 1，on ) / T} and exp{-i×(2πnt 1，off ) / T} determined by the switching times t 1，off and t 1，on of the carrier frequency f1, and two terms exp{-i×(2πnt 2，on ) / T} and exp{-i×(2πnt 2，off ) / T} determined by the switching times t 2，off and t 2，on of the carrier frequency f2 can be used to represent the high - order harmonic noise component A n . By selecting the phase difference in such a way that the absolute value of the sum of these two terms is reduced, the noise can be decreased. Since the coefficients of each term are equal, the phase relationship in the complex plane of each term can be considered. Figure 8 is a diagram showing the phase φ1 of the resultant vector of two terms determined by the switching times t 1，on and t 1，off of the carrier frequency f1 in the complex plane. In Figure 8 , time t 1，on is the reference, and time t 1，on = 0. The relationship between the phase φ1 and each variable is expressed by the following Equation (2). For example, for Equation (1) and Equation (2), the switching control device 1 sets the switching time t 1，on of the carrier frequency f1 as the reference time, that is, time t 1，on = 0.

[0047] [Equation 2]

[0048]

[0049] Figure 9 is a diagram showing the phase φ2 of the composite vector of two terms determined by the switching times t 2，on and t 2，off of the carrier frequency f2 in the complex plane. The relationship between the phase φ2 and each variable is expressed by the following equation (3).

[0050] [Equation 3]

[0051]

[0052] The condition for the high-order harmonic noise component A n to become smaller is that the composite vector of two terms determined by the switching times t 1，on and t 1，off of the carrier frequency f1 cancels out the composite vector of two terms determined by the switching times t 2，on and t 2，off of the carrier frequency f2 in the complex plane. That is, as shown in the following equation (4), it is sufficient that the phase difference between the phase φ1 and the phase φ2 deviates by an odd multiple of π. More generally, as shown in the following equation (5), it is sufficient that the phase difference between the phase φ1 and the phase φ2 is between π / 2 and 3π / 2. k is an integer of 1 or more. That is, in order to reduce the high-order harmonic noise component A n , the switching control device 1 makes the phase φ1 of the composite vector of two terms determined by the switching times t 1，on and t 1， off of the carrier frequency f1 in the complex plane and the phase φ2 of the composite vector of two terms determined by the switching times t 2，on and t 2，off of the carrier frequency f2 in the complex plane become a value as close as possible to an odd multiple of π. In Embodiment 1, in order to reduce the noise at 460 kHz under the frequency change period T = 100 μs, n = 46 is set. In order to reduce the noise in a certain width of the frequency band near 460 kHz, the phase difference Δφ = 0.913π is set, but when it is desired to reduce the noise at 460 kHz in a narrower frequency band, the phase difference Δφ = π can also be set.

[0053] [Equation 4]

[0054] |φ2 - φ1| = (2k - 1)π…(4)

[0055] [Equation 5]

[0056]

[0057] As shown in equations (2) and (3), the terms of π / 2 are included in the phases φ1 and φ2, but when considering the relative phase difference of the phase difference Δφ = |φ1 - φ2|, (t 1，on + t1，off ) / 2 and (t 2，on + t 2，off ) / 2 becomes important. That is, it is only necessary to consider the time difference from the middle time between the on - time and off - time of a certain switching rectangular wave to the middle time between the on - time and off - time of the next switching rectangular wave.

[0058] In Embodiment 1, the phase shift amount is the phase difference Δφ, but the phase shift amount can also be defined by the time difference Δt. For example, in Embodiment 1, if the on - time t 1，on of the carrier frequency f1 becomes the reference time, that is, t 1，on = 0, and then after a time of D / f1 of the duty ratio amount, it switches from the on - state to the off - state, and then makes the on - time of the carrier frequency f2 be 1 / f1+Δt, and after a time of D / f2 of the duty ratio amount from the on - time of f2, it switches from the on - state to the off - state, then each time can be expressed as t 1，on = 0, t 1，off = D / f1, t 2，on = 1 / f1+Δt, t 2，off = 1 / f1+Δt + D / f1. Therefore, according to Equation (2), Equation (3), and Equation (4), Δt can be expressed as in Equation (6) below.

[0059] [Mathematical formula 6]

[0060]

[0061] At this time, in Embodiment 1 with n = 46, k = 61, and D = 0.5, the time difference corresponding to Δφ = 0.913π is Δt = 14.8 μs. Here, the time of t 2，on is shifted, but as long as the relative phase difference can be set, the times of t 1，on , t 1，off , t 2，on and t 2，off can also be shifted arbitrarily. Regarding the switching timing, the on - time t 1，on of the carrier frequency f1 does not have to be set as the reference time. In order to obtain the noise reduction effect, as long as the relative phase difference Δφ can be set.

[0062] Next, the relationship between various detection methods and the noise reduction effect will be described. As detection methods, there are peak detection, quasi - peak detection, and average detection. In particular, regarding peak detection where the conditions for obtaining noise reduction are strict, the calculation method of the spectrum is described, and it is shown that through the present disclosure, the noise reduction effect can be widely obtained corresponding to various measurement conditions. Figure 10This is a diagram for explaining the calculation method of the spectrum in the short-time Fourier transform. In the short-time Fourier transform used in an EMI (ElectroMagnetic Interference) receiver or the like, for a time waveform obtained at a certain measurement time, a window function is used to cut out a part of the interval of the time waveform, and a fast Fourier transform (FFT: Fast Fourier Transform) is performed to obtain the spectrum in that interval. By shifting little by little the interval cut out using the window function, multiple spectra are obtained. The result of extracting the peak value of each of the multiple spectra is the spectrum obtained by peak detection, and the result of calculating the average value is the spectrum obtained by average value detection. When the spectral shapes of the multiple spectra obtained by shifting little by little the interval cut out using the window function are significantly different, referring to the peak values of each of the multiple spectra, it is difficult to obtain a noise reduction effect in peak detection. Therefore, as shown in Patent Document 2, the following method has also been proposed: by making the change period of the frequency shorter than the window function width Tw, the difference in the spectral shapes obtained in each interval is reduced, and a noise reduction effect is obtained in peak detection. However, as shown in Embodiment 1, when there are few switching pulses entering one window function, sometimes a sufficient noise reduction effect cannot be obtained. In the switching control device 1 related to Embodiment 1, by combining frequency variation and phase shift, the noise in specific-order higher harmonic components is suppressed, and even in the situation where noise reduction is difficult as described above, a noise reduction effect can be effectively obtained. Further, the frequency setting unit 2 sets two carrier frequencies f1 and f2 corresponding to specific-order higher harmonic components and a frequency change period T as the period of the carrier frequency change, the phase shift setting unit 3 sets the phase difference Δφ between the switching rectangular wave determined by the carrier frequency f1 set by the frequency setting unit 2 and the switching rectangular wave determined by the carrier frequency f2 set by the frequency setting unit 2, and the control signal generation unit 4 outputs a control signal for controlling the switching operation performed by the switching element 5 according to the settings by the frequency setting unit 2 and the phase shift setting unit 3. Therefore, even in the situation where noise reduction is difficult, the switching control device 1 can effectively suppress the noise in specific-order higher harmonic components.

[0063] The window function width Tw is determined by the reciprocal of the resolution bandwidth (RBW), and takes various values according to the standard and frequency band of interest. Representative values of the resolution bandwidth include 200 Hz, 1 kHz, 9 kHz, 10 kHz, 120 kHz, 1 MHz, etc. In particular, in the frequency band of 526 kHz to 1620 kHz of the AM (Amplitude Modulation) radio band where the problem of electromagnetic noise becomes significant, 9 kHz and 10 kHz are specified as the resolution bandwidths.

[0064] In Embodiment 1, T = 100 μs. Therefore, the window function width Tw determined by the reciprocal of RBW = 9 kHz is 111 μs, or the window function width Tw determined by the reciprocal of RBW = 10 kHz is 100 μs or less. Thus, a sufficient noise reduction effect can also be obtained in peak detection with RBW = 9 kHz and RBW = 10 kHz.

[0065] As the carrier frequency of a general inverter, an arbitrary frequency in the range of several kHz to about 20 kHz is often used, and an arbitrary frequency in a wide range of several kHz to several MHz is used in a DC-DC (Direct Current - Direct Current) converter.

[0066] As described above, in the switching control device 1 according to Embodiment 1, the frequency setting unit 2 sets two carrier frequencies f1 and f2, the phase shift setting unit 3 sets the phase difference Δφ between the switching rectangular wave determined by the carrier frequency f1 set by the frequency setting unit 2 and the switching rectangular wave determined by the carrier frequency f2 set by the frequency setting unit 2, and the control signal generation unit 4 outputs a control signal for controlling the switching operation performed by the switching element 5 according to the settings by the frequency setting unit 2 and the phase shift setting unit 3. Therefore, in the method of Embodiment 1, a noise reduction effect can also be obtained in average value detection.

[0067] As a representative detection method other than peak detection and average value detection, there is also quasi-peak detection in which a time constant circuit is added to peak detection. In the method of Embodiment 1, the repetition period of the switch is sufficiently fast with respect to the time constant, so a spectrum approximately the same as that of peak detection can be obtained, and the same effect as that obtained in peak detection can also be obtained in quasi-peak detection.

[0068] Even for a device using a measurement method other than the short-time Fourier transform, such as a tuning scan type spectrum analyzer, it is possible to expect the same effect as the above-mentioned effect.

[0069] Complex calculations are required to determine the phase shift amount, and it is difficult to obtain the effects achieved by the switching control device 1 according to the first embodiment simply by combining the conventional variable frequency and phase shift.

[0070] As described above, the switching control device 1 according to the first embodiment includes: a frequency setting unit 2 that sets two carrier frequencies f1 and f2; a phase shift setting unit 3 that sets a phase difference Δφ between a switching rectangular wave determined by the carrier frequency f1 set by the frequency setting unit 2 and a switching rectangular wave determined by the carrier frequency f2 set by the frequency setting unit 2; and a control signal generation unit 4 that generates a control signal for controlling the switching operation of the switching element 5 according to the settings performed by the frequency setting unit 2 and the phase shift setting unit 3. In the switching control device 1, the frequency setting unit 2 sets the carrier frequency f1 and the carrier frequency f2, and the phase shift setting unit 3 sets the phase difference Δφ in such a manner as to reduce the switching noise of the high-order harmonic components when the switching element 5 performs the switching operation. Therefore, the switching control device 1 can obtain a noise reduction effect for more diverse measurement conditions. Further, the switching control device 1 can more effectively reduce the noise of the high-order harmonic components at a specific number of times by changing the carrier frequency and the phase.

[0071] Embodiment 2.

[0072] Figure 11 FIG. is a diagram showing the structure of a power conversion device 10 according to the second embodiment. The power conversion device 10 includes the switching control device 1 according to the first embodiment and a boost chopper circuit 11 connected to a DC power supply 12 and a load 13. The boost chopper 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.

[0073] The switching element 15 performs a switching operation at a timing according to the control signal output from the control signal generation unit 4 included in the switching control device 1. The boost chopper circuit 11 boosts the voltage of the input power from the DC power supply 12 and supplies the output power of a desired voltage to the load 13. As the switching element 15, a semiconductor switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) having a diode 16 connected in anti-parallel is used.

[0074] The power conversion device 10 changes the duty ratio corresponding to the state of the load 13 in order to obtain a desired voltage. Therefore, it is necessary to change the phase shift amount in accordance with the duty ratio. The phase shift amount can be calculated sequentially in accordance with the control state, or can be determined based on a previously calculated table.

[0075] The power conversion circuit may also be a DC-DC converter other than the boost chopper circuit 11, for example, a buck chopper circuit.

[0076] Embodiment 3.

[0077] Figure 12 FIG. is a diagram showing the structure of the power conversion device 20 according to Embodiment 3. The power conversion device 20 includes the switch control device 1 according to Embodiment 1 and an inverter circuit 21 connected to the DC power supply 22 and the load 23. The inverter circuit 21 is an example of a power conversion circuit and includes a switching element 24.

[0078] The switching element 24 performs a switching operation at a timing in accordance with a control signal output from the control signal generation unit 4 included in the switch control device 1. The inverter circuit 21 boosts the voltage of the input power from the DC power supply 22 and supplies desired AC output power to the load 23. As the switching element 24, a semiconductor switching element such as a MOSFET or an IGBT having an antiparallel-connected diode is used.

[0079] The inverter circuit 21 needs to change the phase shift amount in accordance with pulse width modulation control for obtaining a desired output voltage of the inverter. The phase shift amount can be calculated sequentially in accordance with the control state, or can be determined based on a previously calculated table.

[0080] The power conversion circuit may also be a circuit formed by combining a converter and an inverter in parallel or in series.

[0081] In addition, the switching control device 1 according to Embodiment 1 may also be the following switching control device 1. That is, the frequency setting unit 2 may set at least two carrier frequencies, and the phase shift setting unit 3 may set the phase difference between the switching rectangular wave determined by the first carrier frequency and the switching rectangular wave determined by the second carrier frequency among the two carrier frequencies set by the frequency setting unit 2. The phase shift setting unit 3 may also set the phase difference between the switching rectangular wave determined by the first carrier frequency and the switching rectangular wave determined by the second carrier frequency among the two carrier frequencies with adjacent values set by the frequency setting unit 2. The frequency setting unit 2 may also set m carrier frequencies and a frequency change period. m is an integer of 2 or more. The control signal generation unit 4 may also generate a switching waveform in the control signal by changing the m carrier frequencies with a frequency change period T. In the frequency change period T, when the phase calculated from the moment t i，on at which the switching rectangular wave becomes ON according to the i-th frequency fi among the m carrier frequencies and the moment t i，off at which the switching rectangular wave becomes OFF according to the i-th frequency fi i is set as φ i , the phase shift setting unit 3 may also set the phase difference such that the absolute value of the phase difference between the phase φ i+1 and the phase φ i is π / m or more and 3π / m or less. i is an integer of 1 or more. The phase φ i may also be defined by the formula φ i，on =πnt i，off / T + πnt i / T. n represents an integer of 1 or more and the order of the high-order harmonic component for which noise reduction is desired. The phase difference between the phase φ i+1 and the phase φ may also be 2π / m.

[0082] Embodiment 4.

[0083] In Embodiment 1, the frequency setting unit 2 sets two carrier frequencies f1 and f2 and a frequency change period T as the period of the carrier frequency change. As described above, the frequency setting unit 2 may also set m carrier frequencies and a frequency change period T as the period of the carrier frequency change. m is an integer of 2 or more. In Embodiment 4, a switching control device in the case where m is 3 will be described. The switching control device according to Embodiment 4 has a frequency setting unit 2, a phase shift setting unit 3, and a control signal generation unit 4 in the same manner as the switching control device 1 according to Embodiment 1. In Embodiment 4, the differences from Embodiment 1 will be mainly described. In Embodiment 2 and Embodiment 3, the switching control device 1 according to Embodiment 1 may also be replaced with the switching control device according to Embodiment 4.

[0084] The values of the parameters in Embodiment 4 are as follows.

[0085] n = 33

[0086] T = 100 μs

[0087] f1 = 20 kHz

[0088] f2 = 30 kHz

[0089] f3 = 60 kHz

[0090] φ1 = 0.75π

[0091] φ2 = 1.69π

[0092] φ3 = 0.05π

[0093] Δφ 12 = φ2 - φ1 = 0.94π

[0094] Δφ 23 = φ3 - φ2 = -1.64π = 0.36π

[0095] Δφ 31 = φ1 - φ3 = 0.7π

[0096] Among the above parameters, n, T, f1, f2, φ1, and φ2 are the parameters described in Embodiment 1. f3 represents a third carrier frequency different from f1 and f2. φ3 represents the phase of the combined vector of two terms determined by the switching times t 3，on and t 3，off of the carrier frequency f3 on the complex plane. The time t 3，on is the time when the switching rectangular wave becomes on according to the carrier frequency f3, and the time t 3，off is the time when the switching rectangular wave becomes off according to the carrier frequency f3. Δφ 12 is the phase difference between φ2 and φ1, Δφ 23 is the phase difference between φ3 and φ2, Δφ 31 is the phase difference between φ1 and φ3. The phase difference is defined in the range of 0 or more and 2π or less.

[0097] In Embodiment 4, the high - order harmonic noise component A of the switching rectangular wave n is represented by the following formula (7). The relationship between the phase φ3 and each variable is represented by the following formula (8). Δφ ij is represented by the following formula (9). In formula (9), i and j are each any one of 1, 2, and 3, and i is different from j. In the case where Δφ ij does not exist in the range of 0 or more and 2π or less, so that Δφ ijThe method exists in the range of 0 or more and 2π or less, and Δφ ij is replaced with Δφ ij +2π or Δφ ij -2π.

[0098] [Mathematical formula 7]

[0099]

[0100] [Mathematical formula 8]

[0101]

[0102] [Mathematical formula 9]

[0103] △φ ij =φ j -φ i …(9)

[0104] The switching control device according to Embodiment 4 sets the phase difference Δφ 12 , Δφ 23 and Δφ 31 to satisfy the following formula (10) respectively, so as to reduce the noise of the nth harmonic component. 12 The phase difference Δφ 23 and the phase difference Δφ 31 are set, thereby reducing the noise of the nth harmonic component.

[0105] [Mathematical formula 10]

[0106]

[0107] Figure 13 is a diagram showing an example of the time waveform of the switching rectangular wave in the control signal output from the control signal generation unit 4 of the switching control device according to Embodiment 4. Figure 13 It is also a diagram for explaining the three phase differences of Δφ 12 , Δφ 23 and Δφ 31 . Figure 14 is a diagram showing the three phase differences of Δφ 12 , Δφ 23 and Δφ 31 in the complex plane. Figure 15 is a diagram showing an example of the time waveform of the switching rectangular wave when the frequency is variable. Figure 16 is a diagram showing an example of the time waveform of the switching rectangular wave when the frequency is fixed. In Figure 13 , Figure 15 and Figure 16 , the horizontal axis represents time and the vertical axis represents voltage. In Figure 16In this case, 30 kHz is used as the fixed switching frequency. In order to make the conditions of switching losses equivalent by setting the number of switching times to be equal to that at the three carrier frequencies of Figure 13 30 kHz, which is a fixed switching frequency, is selected.

[0108] Figure 17 FIG. is a diagram showing a comparison between the frequency characteristics of electromagnetic noise in the case of using the switching control device according to Embodiment 4 and the frequency characteristics of electromagnetic noise in the case where the switching rectangular wave is fixed. Figure 18 FIG. is a diagram showing a comparison between the frequency characteristics of electromagnetic noise in the case where the switching rectangular wave is fixed and the frequency characteristics of electromagnetic noise in the case where only the carrier frequency is variable.

[0109] As shown in Figure 17 , it can be seen that compared with the case where the frequency is fixed, in Embodiment 4, the noise is reduced with a certain width in the frequency band of 310 kHz to 400 kHz including 330 kHz. On the other hand, as shown in Figure 18 , in the case where the frequency is variable, the harmonic component of 330 kHz is larger than that in Embodiment 4. The method of Embodiment 4 is also effective in reducing the noise of harmonic components of specific orders.

[0110] Figure 19 FIG. is a diagram of the processor 97 showing a case where at least a part of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 included in the switching control device 1 according to Embodiment 1 is implemented by the processor 97. That is, the functions of at least a part of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 of Embodiment 1 can also be implemented by the processor 97 that executes the program stored in the memory 98. The processor 97 is a CPU (Central Processing Unit, central processing unit), a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor, digital signal processor). In Figure 19 , the memory 98 is also shown.

[0111] When at least a part of the functions of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1 are implemented by the processor 97, at least a part of the functions are implemented by the processor 97, and software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory 98. The processor 97 realizes at least a part of the functions of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1 by reading and executing the program stored in the memory 98.

[0112] When at least part of the functions of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1 are implemented by the processor 97, the switch control device 1 has a memory 98 for storing a program which, as a result, executes at least part of the steps executed by the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4. The program stored in the memory 98 can also be said to be a program that causes a computer to execute at least part of the processes or methods executed by the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1.

[0113] The memory 98 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (registered trademark in Japan) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a floppy disk, an optical disk, a high-density disk, a mini disk, or a DVD (Digital Versatile Disk).

[0114] Figure 20 FIG. shows a processing circuit 99 in the case where at least part of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 included in the switch control device 1 according to Embodiment 1 are implemented by the processing circuit 99. That is, at least part of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1 can also be implemented by the processing circuit 99.

[0115] The processing circuit 99 is dedicated hardware. The processing circuit 99 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0116] Part of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4 in Embodiment 1 can also be implemented by dedicated hardware different from the remaining parts of the frequency setting unit 2, the phase shift setting unit 3, and the control signal generation unit 4.

[0117] Regarding the multiple functions of the frequency setting unit 2, phase shift setting unit 3, and control signal generation unit 4 in Embodiment 1, a part of the multiple functions can also be implemented by software or firmware, and the remaining part of the multiple functions can be implemented by dedicated hardware. In this way, the multiple functions of the frequency setting unit 2, phase shift setting unit 3, and control signal generation unit 4 in Embodiment 1 can be implemented by hardware, software, firmware, or a combination thereof.

[0118] Regarding the switch control device according to Embodiment 4, at least a part of the functions of the frequency setting unit 2, phase shift setting unit 3, and control signal generation unit 4 can be implemented either by a processor that executes a program stored in a memory or by a processing circuit.

[0119] The structures shown in the above embodiments are merely examples, and can also be combined with other known technologies, and parts of the structures can also be omitted or changed without departing from the gist.

[0120] Description of reference symbols

[0121] 1: Switch control device; 2: Frequency setting unit; 3: Phase shift setting unit; 4: Control signal generation unit; 5, 15, 24: Switching element; 10, 20: Power conversion device; 11: Boost chopper 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.

Claims

1. A switch control device that controls the switching operation performed by a switching element, characterized in that, Comprising: 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 based on the first carrier frequency set by the frequency setting unit and a second switching rectangular wave determined based on the second carrier frequency set by the frequency setting unit; and a control unit that controls the switching operation performed by the switching element according to the phase difference set by the phase shift setting unit.

2. The switching control device according to claim 1, wherein the phase shift setting unit sets the phase difference in order to reduce switching noise of high-order harmonic components generated due to the switching operation.

3. The switching 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 ratio corresponding to the high-order harmonic components, and the phase shift setting unit sets the phase difference corresponding to the high-order harmonic components.

4. The switching control device according to claim 2, wherein the control unit is a control signal generation unit that generates a control signal for controlling the switching operation performed by the switching element according to the settings performed by the frequency setting unit and the phase shift setting unit, and the frequency setting unit sets the at least first carrier frequency and second carrier frequency in order to reduce switching noise of high-order harmonic components generated due to the switching operation.

5. The switching control device according to claim 4, wherein the frequency setting unit sets m types of carrier frequencies and a frequency change period, and the control signal generation unit generates a switching waveform in the control signal by changing the m types of carrier frequencies with the frequency change period, where m is an integer of 2 or more.

6. The switching control device according to claim 5, wherein During the frequency change period, at the time t when it becomes on based on the switching rectangular wave according to the i-th frequency fi among the m carrier frequencies i，on and the time t when the switching rectangular wave becomes off according to the i-th frequency fi i，off the calculated phase is set to φ i in the case of The phase shift setting unit sets the phase difference such that the absolute value of the phase difference between the phase φ i and the phase φ i+1 is equal to or greater than π / m and equal to or less than 3π / m. i is an integer of 1 or more.

7. The switching control device according to claim 6, wherein Use φ i = πnt i，on / T + πnt i，off / T to define the phase φ i , n represents an integer of 1 or more and is the order of the high-order harmonic component for which noise reduction is desired, and T represents the frequency change period.

8. The switching control device according to claim 6 or 7, wherein The phase φ i and the phase φ i+1 have a phase difference of 2π / m.

9. The switching control device according to any one of claims 5 to 8, wherein the m is 2.

10. The switching control device according to any one of claims 5 to 9, wherein the frequency change period is shorter than the time width determined by the reciprocal of the 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. A power conversion device, characterized in that, Comprising: the switching control device according to any one of claims 1 to 11; and a power conversion circuit including a switching element.

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