JP6433536B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device.

  As a conventional power conversion device, for example, a technique disclosed in Patent Document 1 is known. The power conversion device described in Patent Literature 1 includes an AC / DC converter that performs AC / DC conversion, and a DC / DC converter that is disposed in a subsequent stage and performs DC / DC conversion in which a primary side and a secondary side are insulated by a transformer. And supplies power to a load such as a battery.

  The AC / DC converter and the DC / DC converter each include a switching element such as an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET), and are PWM-controlled by a control circuit.

  In the control circuit, a PWM control unit is provided for each of the AC / DC converter and the DC / DC converter. When the carrier comparison method is adopted as the PWM control method, the PWM control unit compares the carrier frequency calculation unit for calculating the carrier frequency, the pulse having a width corresponding to the output of the duty command value by comparing the duty command value and the carrier frequency. And a comparator for calculating a signal.

  The duty command value is calculated and updated at regular intervals by monitoring the voltage and current in each of the AC / DC converter, the smoothing capacitor for smoothing the DC output of the AC / DC converter, and the DC / DC converter. . Here, the duty command value calculation frequency is generally set to a frequency lower than the drive frequency of the AC / DC converter and the DC / DC converter in order to simplify the calculation process in the control circuit and reduce the load. It is.

International Publication No. 2011/151940

  As described above, the duty command value calculation frequency may be set to a frequency lower than the drive frequency of the AC / DC converter and the DC / DC converter in order to simplify the calculation process in the control circuit and reduce the load. It is common. In that case, in the power conversion device of Patent Document 1, the noise component of the duty command value calculation frequency of each converter and the beat noise component generated by signal interference between the duty command value calculation frequency of each converter and the drive frequency are each There has been a problem that it occurs in a frequency band lower than the drive frequency of the converter and is superimposed on the output signal of the PWM controller.

  Since the switching element of each converter is driven by an output signal on which the noise component is superimposed, the noise component propagates to each converter via the switching element and flows out to the commercial power source side. For example, when the drive frequency of each converter is set to 100 kHz and the duty command value calculation frequency of each converter is set to 30 kHz, the commercial power supply side has 30 kHz, 60 kHz as noise components of the duty command value calculation frequency of each converter. A noise spectrum is generated at 90 kHz, and noise spectra are generated at 10 kHz, 40 kHz, and 70 kHz as beat noise components generated by signal interference between the duty command value calculation frequency and the drive frequency of each converter. In order to reduce the noise component to a level below the limit value defined in the official standard, a noise filter having a cutoff frequency in the several kHz band is connected between the commercial power supply and the AC / DC converter. Is required. Since such a noise filter is large in size and expensive, there has been a problem that an increase in size of the apparatus and a significant increase in cost are inevitable.

  This invention was made in order to solve this subject, and it aims at providing the power converter device which can suppress the noise which generate | occur | produces in the frequency band below the drive frequency of a power converter part. To do.

The present invention includes a power conversion unit having a switching element, and a first PWM control unit that performs PWM control of the switching element, and the first PWM control unit calculates a duty command value for each fixed period. A command value calculation unit; and a PWM signal calculation unit that calculates and outputs a pulse signal having a width corresponding to the duty command value output from the duty command value calculation unit. The switching element of the power converter is driven by a pulse signal, the duty command value calculation frequency of the power converter is set to an integer multiple of the drive frequency of the power converter, and the power converter It is a power converter device comprised from the AC / DC converter which converts DC into a DC voltage .

  According to the power conversion device of the present invention, by setting the duty command value calculation frequency of the power conversion unit to an integer multiple of the drive frequency, it is possible to suppress noise generated in a frequency band equal to or lower than the drive frequency of the power conversion unit.

It is the block diagram which showed the structure of the power converter device which concerns on Embodiment 1 of this invention. It is the block diagram which showed the structure of the PWM control part in the power converter device which concerns on Embodiment 1 of this invention. When the LISN prescribed | regulated by CISPR16-1-2 is connected between the conventional power converter and commercial power supply, it is the figure which showed the noise terminal voltage observed at the both ends of the resistance for noise measurement of LISN. Noise terminal voltage observed at both ends of a LISN noise measurement resistor when a LISN defined by CISPR16-1-2 is connected between the power converter according to Embodiment 1 of the present invention and a commercial power supply FIG.

Embodiment 1 FIG.
Hereinafter, a power converter according to Embodiment 1 of the present invention will be described. 1 is a diagram showing a configuration of a power conversion device according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the power conversion device according to Embodiment 1 is configured with elements that are connected to a commercial power source 1 and supply power to a load 2. However, the power conversion device according to the first embodiment does not necessarily include all elements between the commercial power source 1 and the load 2 shown in FIG.

  An AC / DC converter 100 is connected to the commercial power source 1. Further, a first smoothing capacitor 10 as a link capacitor is connected to the subsequent stage of the AC / DC converter 100.

  As shown in FIG. 1, the AC / DC converter 100 includes a first diode bridge 3, a first reactor 4, a first MOSFET 5 as a semiconductor switching element, and a rectifier diode 6.

  In the AC / DC converter 100, the first diode bridge 3 is connected to the commercial power source 1, and full-wave rectifies the alternating current input from the commercial power source 1. In the first diode bridge 3, a plurality of bridge-connected diodes (not shown) are provided. A first MOSFET 5 is connected in parallel to the first diode bridge 3. A first reactor 4 is connected in series to the positive power line between the first diode bridge 3 and the drain terminal of the first MOSFET 5. The anode terminal of the rectifier diode 6 is connected to the drain terminal of the first MOSFET 5. The positive terminal of the first smoothing capacitor 10 is connected to the cathode terminal of the rectifier diode 6 via the positive power line. Further, the negative terminal of the first smoothing capacitor 10 is connected to the source terminal of the first MOSFET 5 through the negative power line.

  The AC / DC converter 100 is configured in this way and performs AC / DC conversion. Specifically, AC / DC converter 100 converts the AC voltage of commercial power supply 1 into a DC voltage.

  Here, FIG. 1 shows an example in which, in the AC / DC converter 100, a first MOSFET 5 composed of a MOSFET is provided as a semiconductor switching element. However, the present invention is not limited to this, and another semiconductor switching element such as an IGBT may be provided instead of the first MOSFET 5.

  The first smoothing capacitor 10 smoothes the DC output from the AC / DC converter 100. A DC / DC converter 200 is connected to the subsequent stage of the first smoothing capacitor 10, and a load 2 is connected to the subsequent stage.

  The DC / DC converter 200 includes a second MOSFET 11a, a third MOSFET 11b, a fourth MOSFET 11c, a fifth MOSFET 11d, a transformer 12, a second diode bridge 13, a second reactor 14, and a smoothing capacitor 15. Yes.

  In the DC / DC converter 200, the four MOSFETs, that is, the second MOSFET 11a, the third MOSFET 11b, the fourth MOSFET 11c, and the fifth MOSFET 11d constitute a full bridge circuit. That is, the source terminal of the second MOSFET 11a and the drain terminal of the third MOSFET 11b are connected in series, and similarly, the source terminal of the fourth MOSFET 11c and the drain terminal of the fifth MOSFET 11d are connected in series. Further, the drain terminal of the second MOSFET 11a and the drain terminal of the fourth MOSFET 11c are connected, and similarly, the source terminal of the third MOSFET 11b and the source terminal of the fifth MOSFET 11d are connected. The full bridge circuit configured as described above is connected in parallel to the first smoothing capacitor 10 and converts the DC voltage of the first smoothing capacitor 10 into an AC voltage.

  On the primary side of the transformer 12, a connection point between the second MOSFET 11a and the third MOSFET 11b and a connection point between the fourth MOSFET 11c and the fifth MOSFET 11d are connected. A second diode bridge 13 is connected to the secondary side of the transformer 12. In the second diode bridge 13, a plurality of bridge-connected diodes are provided. An output smoothing second reactor 14 and a smoothing capacitor 15 are connected to the output of the second diode bridge 13, and a DC voltage is output to the load 2.

  The DC / DC converter 200 is configured in this way and performs DC / DC conversion. Specifically, the DC / DC converter 200 converts the voltage of the first smoothing capacitor 10 into a secondary side DC voltage insulated by the transformer 12 and outputs it to the load 2.

  Here, FIG. 1 shows an example in which, in the DC / DC converter 200, the second to fifth MOSFETs 11a to 11d formed of MOSFETs are provided as semiconductor switching elements. However, not limited to this case, other semiconductor switching elements such as IGBTs may be provided instead of the second to fifth MOSFETs 11a to 11d.

  Hereinafter, the operation principle of the AC / DC converter 100 and the DC / DC converter 200 will be described.

  First, the operating principle of the AC / DC converter 100 will be briefly described. As described above, the AC / DC converter 100 includes the first diode bridge 3, the first reactor 4, the first MOSFET 5, and the rectifier diode 6. First, when the first MOSFET 5 is turned on, a current flows through the first reactor 4, and energy is accumulated in the first reactor 4. Next, when the MOSFET 5 is turned off, the energy accumulated in the first reactor 4 is transmitted to the first smoothing capacitor 10. At this time, the control of the control circuit 300, which will be described later, is controlled so as to improve the power factor by PWM controlling on / off of the MOSFET 5 so that the input current waveform to the first smoothing capacitor 10 becomes a sine wave. can do.

  Note that the AC / DC converter 100 is not limited to the configuration of FIG. 1, and may be configured of another AC / DC converter circuit that performs power conversion by switching.

  Next, the operating principle of the DC / DC converter 200 will be briefly described. As described above, the DC / DC converter 200 includes the second MOSFET 11a, the third MOSFET 11b, the fourth MOSFET 11c, the fifth MOSFET 11d, the transformer 12, the second diode bridge 13, the second reactor 14, and the smoothing capacitor. 15. First, simultaneous ON of the second MOFET 11a and the fifth MOFET 11d and simultaneous ON of the third MOFET 11b and the fourth MOFET 11c are alternately performed with the same ON time. A signal obtained by these simultaneous ONs is transmitted from the primary side to the secondary side of the DC / DC converter 200 via the transformer 12. Next, based on the signal transmitted to the secondary side of the DC / DC converter 200, the second diode 11a, the third MOSFET 11b, the fourth MOSFET 11c, and the fifth MOSFET 11d are operated according to the operation of the second diode. When each diode (not shown) provided in the bridge 13 is turned on / off, direct current / direct current conversion is performed. The converted DC power is smoothed by the second reactor 14 and the second smoothing capacitor 15 and transmitted to the load 2.

  Note that the DC / DC converter 200 is not limited to the configuration of FIG. 1, and may be configured of another DC / DC converter circuit that performs power conversion by switching.

  PWM control of the AC / DC converter 100 and the DC / DC converter 200 is performed by the control circuit 300. In the control circuit 300, a PWM control unit 301 is provided for each of the first MOSFET 5 of the AC / DC converter 100 and the second to fifth MOSFETs 11a to 11d of the DC / DC converter 200. That is, the control circuit 300 is provided with five PWM control units 301. However, since the second MOFET 11a and the fifth MOFET 11d are simultaneously turned on / off, the PWM controller 301 can be shared. Therefore, a common PWM control unit 301 may be provided for the second MOFET 11a and the fifth MOFET 11d. For the same reason, one common PWM control unit 301 may be provided for the third MOFET 11b and the fourth MOFET 11c. Furthermore, since there is at least one duty command value calculation unit 302 for the AC / DC converter 100 and the DC / DC converter 200, the duty command value calculation unit 302 is provided for the second MOSFET 11a and the fifth MOSFET 11d. Duty command value calculation unit 302 of one common PWM control unit 301 and Duty command value calculation unit 302 of one common PWM control unit 301 provided for the third MOSFET 11b and the fourth MOSFET 11c It is also possible to share. FIG. 2 shows a configuration of PWM control section 301 for PWM control of MOSFETs 5 and 11a to 11d provided in control circuit 300 of the power conversion device according to Embodiment 1 of the present invention.

  As shown in FIG. 2, the PWM control unit 301 includes a duty command value calculation unit 302 and a PWM signal calculation unit 303. The duty command value calculation unit 302 monitors the voltage and current of the AC / DC converter 100, the voltage of the first smoothing capacitor 10, and the voltage and current of the DC / DC converter 200, and based on those values, The duty command value is calculated and output at regular intervals. The PWM signal calculation unit 303 outputs a pulse signal having a width corresponding to the duty command value. As shown in FIG. 2, the PWM signal calculation unit 303 compares the carrier frequency calculation unit 305 that outputs the carrier frequency (driving frequency) Fa, the output of the duty command value calculation unit 302, and the output of the carrier frequency calculation unit 305. And a comparator 304. The PWM signal calculation unit 303 compares the output of the duty command value calculation unit 302 and the output of the carrier frequency calculation unit 305 by the comparator 304 and outputs a PWM signal. As a result, the pulse signal constituting the PWM signal becomes a pulse signal having a width corresponding to the duty command value from the duty command value calculation unit 302. The output of the comparator 304 is ON when “output of the duty command value calculation unit 302> output of the carrier frequency calculation unit 305”, and “output of the duty command value calculation unit 302 ≦ output of the carrier frequency calculation unit 305”. Will be turned off. The output of the comparator 304 is ON when “the output of the duty command value calculation unit 302 ≧ the output of the carrier frequency calculation unit 305”, “the output of the duty command value calculation unit 302 <the output of the carrier frequency calculation unit 305”. At this time, it may be turned OFF.

  The current and voltage are detected by the following method, and the duty command value calculation unit 302 monitors the detected value. That is, the voltage and current of the AC / DC converter 100 are respectively applied to the input voltage sensor 30a provided at both ends of the commercial power source 1 and the positive power line between the commercial power source 1 and the first diode bridge 3. It is detected by the connected input current sensor 30b. Further, the voltage of the first smoothing capacitor 10 is detected by the first smoothing capacitor voltage sensor 30d provided at both ends of the first smoothing capacitor 10. The voltage and current of the DC / DC converter 200 are respectively the output voltage sensor 30f provided at both ends of the second smoothing capacitor 15, and the positive power between the second smoothing capacitor 15 and the load 2. It is detected by an output current sensor 30g connected to the line.

  The duty command value calculation frequency Fc output from the duty command value calculation unit 302 to the PWM signal calculation unit 303 is set to n times the carrier frequency Fa (Fc = n × Fa, n is an integer), and PWM The output of the signal calculation unit 303 is input to the gates of the first to fifth MOSFETs 5, 11a to 11d. Hereinafter, the output of the PWM signal calculation unit 303 is referred to as drive signals 30c and 30e from the control circuit 300.

  Note that, by setting the duty command value calculation frequency Fc of the AC / DC converter 100 and the DC / DC converter 200 to the same value, the calculation process in the control circuit 300 can be simplified and the load can be reduced. In that case, for example, the duty command value calculation frequency Fc of the AC / DC converter 100 and the DC / DC converter 200 may be set to the same value as the duty command value calculation frequency of the AC / DC converter 100.

  Further, the control circuit 300 is configured by, for example, a single-chip IC (Integrated Circuit) capable of parallel processing such as a Field-Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), or the like, thereby further calculating frequency. And the number of parts can be reduced.

  Hereinafter, in order to clarify the effect of the power conversion device according to Embodiment 1 of the present invention, with respect to noise generated from the conventional power conversion device, the drive frequency of the AC / DC converter is 100 kHz, and the drive frequency of the DC / DC converter is Will be described in detail by taking as an example a case in which 100 kHz is set, the duty command value calculation frequency of the AC / DC converter is set to 30 kHz, and the duty command value calculation frequency of the DC / DC converter is set to 30 kHz.

  Since the drive frequency and duty command value calculation frequency of each converter are the same value, the noise component of the drive frequency of each converter, the noise component of the duty command value calculation frequency of each converter, and the duty command value calculation of each converter Beat noise components generated by signal interference between the frequency and the drive frequency are all generated in the same frequency band. The noise component flowing out to the commercial power supply side is larger in the AC / DC converter directly connected to the commercial power supply, and the effect when the power conversion device according to Embodiment 1 of the present invention is applied is significant. Hereinafter, description will be given focusing on only the AC / DC converter.

  First, according to FIG. 2, in the conventional power converter, the carrier frequency Fa and the duty command value calculation frequency Fc are Fa = 100 kHz and Fc = 30 kHz (≠ n × Fa). Among the noise components included in the output signal of the PWM signal calculation unit 303 of the AC / DC converter, the noise of the drive frequency of the AC / DC converter with respect to the noise component and the beat noise component of the duty command value calculation frequency of the AC / DC converter The largest component. Therefore, the noise component that propagates to the AC / DC converter and flows out to the commercial power source has the largest drive frequency component of the AC / DC converter. Further, since the noise component of the driving frequency of the AC / DC converter has a relationship of “fundamental wave Fa1> second harmonic wave Fa2> third harmonic wave Fa3”, the duty command value calculation frequency of the AC / DC converter and the AC / DC converter The beat noise due to the difference from the driving frequency of the DC converter has the largest component due to the difference from the fundamental frequency Fa1 of the driving frequency of the AC / DC converter. Therefore, in the following, beat noise (Fb1) due to the difference between the fundamental wave Fc1, the second harmonic Fc2, the third harmonic Fc3 of the duty command value calculation frequency of the AC / DC converter and the fundamental wave of the drive frequency of the AC / DC converter Description will be made by paying attention to (= | Fa1-Fc1 |), Fb2 (= | Fa1-Fc2 |), and Fb3 (= | Fa1-Fc3 |)).

  FIG. 3 is observed at both ends of a LISN noise measurement resistor when a LISN (Lline Impedance Stabilization Network) defined by CISPR16-1-2 is connected between the conventional power converter and the commercial power source 1. The noise terminal voltage is shown. In FIG. 3, the respective symbols are as follows.

Fa1: Fundamental wave of driving frequency of AC / DC converter Fa2: Second harmonic of driving frequency of AC / DC converter Fa3: Third harmonic of driving frequency of AC / DC converter Fa4: Driving frequency of AC / DC converter 4th harmonic Fa5: 5th harmonic of the drive frequency of the AC / DC converter Fa6: 6th harmonic of the drive frequency of the AC / DC converter Fc1: Fundamental wave of the duty command value calculation frequency of the AC / DC converter Fc2: AC / Second harmonic of duty command value calculation frequency of DC / DC converter Fc3: Third harmonic of duty command value calculation frequency of AC / DC converter Fb1: Fundamental wave of duty command value calculation frequency of AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
First beat noise Fb2: Second harmonic of duty command value calculation frequency of AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
Second beat noise Fb3: The third harmonic of the duty command value calculation frequency of the AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
Third beat noise

  Also, the broken line in FIG. 3 is the limit value of the conduction noise level of CISPR11 (5th edition; 2010) defined by the International Special Committee on Radio Interference (CISPR). In this case, the fundamental wave Fc1, the second harmonic Fc2, and the third harmonic Fc3 of the duty command value calculation frequency of the AC / DC converter are Fc1 = 30 kHz, Fc2 = 60 kHz, Fc3 = 90 kHz, and the noise spectrum is at each frequency. Occur. The first beat noise Fb1, the second beat noise Fb2, and the third beat noise Fb3 due to the difference between the duty command value calculation frequency of the AC / DC converter and the fundamental wave Fa1 of the drive frequency of the AC / DC converter are: The following equations (4), (5), and (6) are obtained, respectively, and a noise spectrum is generated at each frequency in the same manner as noise caused by the control frequency.

Fb1 = | Fa1-Fc1 | = | 100 kHz-30 kHz | = 70 kHz (4)
Fb2 = | Fa1-Fc2 | = | 100 kHz-60 kHz | = 40 kHz (5)
Fb3 = | Fa1-Fc3 | = | 100 kHz-90 kHz | = 10 kHz (6)

  From the above, the noise component of the duty command value calculation frequency of the AC / DC converter and the beat noise component due to the difference between the duty command value calculation frequency of the AC / DC converter and the drive frequency of the AC / DC converter are driven by the AC / DC converter. A plurality of occurrences occur in the tens of kHz band below the frequency. In this case, in order to make the noise level below the limit value, it is necessary to connect a large noise filter having a cut-off frequency of 10 kHz or less. Therefore, an increase in the size of the noise filter and a significant increase in cost are inevitable.

  Next, based on the noise generated from the conventional power converter shown in FIG. 3, in the power converter according to Embodiment 1 of the present invention, the drive frequency of the AC / DC converter 100 is 100 kHz, and the DC / DC converter The noise suppression effect when the drive frequency of 200 is set to 100 kHz, the duty command value calculation frequency of the AC / DC converter 100 is set to 200 kHz, and the duty command value calculation frequency of the DC / DC converter 200 is set to 200 kHz will be described. In the following, as in the case of the conventional power converter, focusing only on the AC / DC converter, the fundamental wave Fc, the second harmonic Fc2, the third harmonic Fc3 of the duty command value calculation frequency of the AC / DC converter, Paying attention to beat noise (Fb1 (= | Fa1-Fc1 |), Fb2 (= | Fa1-Fc2 |), Fb3 (= | Fa1-Fc3 |)) due to the difference in the fundamental frequency of the driving frequency of the AC / DC converter explain.

  FIG. 4 shows observations at both ends of a LISN noise measurement resistor when a LISN (Lline Impedance Stabilization Network) defined by CISPR16-1-2 is connected between the power converter according to the present invention and the commercial power source 1. The noise terminal voltage is shown. In FIG. 4, the respective symbols are as follows.

Fa1: Fundamental wave of driving frequency of AC / DC converter Fa2: Second harmonic of driving frequency of AC / DC converter Fa3: Third harmonic of driving frequency of AC / DC converter Fa4: Driving frequency of AC / DC converter 4th harmonic Fa5: 5th harmonic of the drive frequency of the AC / DC converter Fa6: 6th harmonic of the drive frequency of the AC / DC converter Fc1: Fundamental wave of the duty command value calculation frequency of the AC / DC converter Fc2: AC / Second harmonic of duty command value calculation frequency of DC / DC converter Fc3: Third harmonic of duty command value calculation frequency of AC / DC converter Fb1: Fundamental wave of duty command value calculation frequency of AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
First beat noise Fb2: Second harmonic of duty command value calculation frequency of AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
Second beat noise Fb3: The third harmonic of the duty command value calculation frequency of the AC / DC converter
Due to the difference between the driving frequency of the AC / DC converter and the fundamental wave Fa1
Third beat noise

  The broken line in FIG. 4 is the limit value of the conduction noise level of CISPR11 (5th edition; 2010) defined by the International Special Committee on Radio Interference (CISPR), as in FIG. In this case, the fundamental wave Fc1, the second harmonic Fc2, and the third harmonic Fc3 of the duty command value calculation frequency are Fc1 = 200 kHz, Fc2 = 400 kHz, and Fc3 = 600 kHz, respectively, and the driving frequency of the AC / DC converter is 2 It overlaps with the second harmonic Fa2, the fourth harmonic Fa4, and the sixth harmonic Fa6. Here, since the level of the noise component of the drive frequency of the AC / DC converter is more dominant than the noise component of the duty command value calculation frequency of the AC / DC converter, the AC / DC converter even if the frequencies overlap. The noise level hardly increases more than the noise component of the driving frequency. The first beat noise Fb1, the second beat noise Fb2, and the third beat noise Fb3 due to the difference between the duty command value calculation frequency of the AC / DC converter and the fundamental wave Fa1 of the drive frequency of the AC / DC converter are: The following equations (1), (2), and (3) are obtained, and the fundamental frequency Fa1 (= 100 kHz), the third harmonic Fa3 (= 300 kHz), and the fifth harmonic Fa5 ( = 500 kHz).

Fb1 = | Fa1-Fc1 | = | 100 kHz-200 kHz | = 100 kHz (1)
Fb2 = | Fa1-Fc2 | = | 100 kHz-400 kHz | = 300 kHz (2)
Fb3 = | Fa1-Fc3 | = | 100 kHz-600 kHz | = 500 kHz (3)

  Similar to the noise component of the duty command value calculation frequency of the AC / DC converter, the beat noise component due to the difference between the duty command value calculation frequency of the AC / DC converter and the fundamental wave Fa1 of the drive frequency of the AC / DC converter is Since the level of the noise component of the driving frequency of the DC converter is larger and more dominant, the noise level hardly increases more than the noise component of the driving frequency of the AC / DC converter even if the frequencies overlap.

  From the above, the noise component of the duty command value calculation frequency of the AC / DC converter and the beat noise component due to the difference between the duty command value calculation frequency of the AC / DC converter and the drive frequency of the AC / DC converter are the AC / DC converter. The noise component and the frequency of the driving frequency overlap, and noise that has conventionally been generated in the tens of kHz band below the driving frequency of the AC / DC converter is completely suppressed. In this case, if a small noise filter having a cut-off frequency is connected in the vicinity of 100 kHz, the noise level can be reduced below the limit value. Therefore, it is possible to reduce the size and cost of the noise filter.

  In the above description of the first embodiment, the duty command value calculation frequency of the AC / DC converter 100 is twice the drive frequency of the AC / DC converter 100, but the duty command value calculation of the AC / DC converter 100 is performed. The frequency and the drive frequency of the AC / DC converter 100 may be the same.

  As described above, the power conversion device according to the first embodiment includes the AC / DC converter 100 as the power conversion unit having the first MOSFET 5 as the switching element, and the first PWM that performs PWM control on the first MODFET 5. And a control unit 301. Further, the first PWM control unit 301 includes a duty command value calculation unit 302 that calculates the duty command value at regular intervals, and a pulse signal having a width corresponding to the duty command value output from the duty command value calculation unit 302. The first MOSFET 5 of the AC / DC converter 100 is driven by the drive signal 30c configured by the pulse signal of the PWM signal calculation unit 303. Further, the duty command value calculation frequency Fc of the AC / DC converter 100 is set to an integer n times the drive frequency Fa of the AC / DC converter 100. Thus, the noise component of the duty command value calculation frequency Fc of the AC / DC converter 100 and the beat noise component due to the difference between the duty command value calculation frequency Fc of the AC / DC converter 100 and the drive frequency Fa of the AC / DC converter 100 The frequency overlaps with the noise component of the drive frequency Fa of the AC / DC converter 100. As a result, it is possible to completely suppress noise and beat noise that have conventionally been generated in the tens of kHz band below the drive frequency of the AC / DC converter 100.

  Furthermore, the power conversion device according to the first embodiment includes a DC / DC converter 200 as a second power conversion unit having second to fifth MOSFETs 11a to 11d as switching elements, and a DC / DC converter 200. And a second PWM control unit 301 that performs PWM control of the switching element. The second PWM control unit 301 includes a second duty command value computing unit 302 that computes the duty command value at regular intervals, and a width corresponding to the duty command value output from the second duty command value computing unit 302. And a second PWM signal calculation unit 303 that calculates and outputs a pulse signal having. The switching element of the DC / DC converter 200 is driven by the drive signal 30e configured from the pulse signal of the second PWM signal calculation unit 303. The duty command value calculation frequency Fc of the DC / DC converter 200 is set to an integer n times the driving frequency Fa of the DC / DC converter 200. Thus, the noise component of the duty command value calculation frequency Fc of the DC / DC converter 200 and the beat noise component due to the difference between the duty command value calculation frequency Fc of the DC / DC converter 200 and the drive frequency Fa of the DC / DC converter 200 The frequency overlaps with the noise component of the driving frequency Fa of the DC / DC converter 200. As a result, it is possible to completely suppress noise and beat noise that have conventionally been generated in the tens of kHz band below the drive frequency of the DC / DC converter 200.

  DESCRIPTION OF SYMBOLS 1 Commercial power supply, 2 loads, 3 1st diode bridge, 4 1st reactor, 5 1st MOSFET, 6 rectifier diode, 10 1st smoothing capacitor, 11a 2nd MOSFET, 11b 3rd MOSFET, 11c 4th MOSFET, 11d 5th MOSFET, 12 transformer, 13 2nd diode bridge, 14 2nd reactor, 15 2nd smoothing capacitor, 30a input voltage sensor, 30b input current sensor, 30c to first MOSFET Drive signal, 30d first smoothing capacitor voltage sensor, 30e drive signal to second to fifth MOSFETs, 30f output voltage sensor, 30g output current sensor, 100 AC / DC converter, 200 DC / DC converter, 300 control circuit .

Claims (9)

A power converter having a switching element;
A first PWM control unit that performs PWM control of the switching element,
The first PWM control unit includes:
A duty command value calculation unit for calculating a duty command value at regular intervals;
A PWM signal calculation unit that calculates and outputs a pulse signal having a width corresponding to the duty command value output from the duty command value calculation unit;
The switching element of the power conversion unit is driven by the pulse signal of the PWM signal calculation unit,
The duty command value calculation frequency of the power converter is set to an integer multiple of the drive frequency of the power converter ,
The power conversion unit is composed of an AC / DC converter that converts an AC voltage into a DC voltage.
Power conversion device. The integer is 1,
The duty command value calculation frequency of the power converter is the same as the drive frequency of the power converter.
The power conversion device according to claim 1. The first PWM control unit is composed of a one-chip IC capable of parallel processing.
The power converter according to claim 1 or 2. A second power converter having a switching element;
The second power conversion unit is connected to the AC / DC converter, and includes a DC / DC converter that performs DC / DC conversion on a DC voltage output from the AC / DC converter.
The power converter according to any one of claims 1 to 3 . A second PWM control unit that PWM-controls the switching element of the second power conversion unit configured by the DC / DC converter;
The second PWM controller is
A second duty command value computing unit for computing the duty command value at regular intervals;
A second PWM signal calculation unit that calculates and outputs a pulse signal having a width corresponding to the duty command value output from the second duty command value calculation unit;
The switching element of the second power converter is driven by the pulse signal of the second PWM signal calculator.
The power conversion device according to claim 4 . The duty command value calculation frequency of the DC / DC converter is set to an integral multiple of the drive frequency of the DC / DC converter.
The power conversion device according to claim 5 . The integer is 1,
The duty command value calculation frequency of the DC / DC converter is the same as the drive frequency of the DC / DC converter.
The power conversion device according to claim 6 . The duty command value calculation frequency of the AC / DC converter is the same as the duty command value calculation frequency of the DC / DC converter.
The power converter according to any one of claims 5 to 7 . The second PWM control unit is composed of a one-chip IC capable of parallel processing.
The power converter according to any one of claims 5 to 8 .

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