Power conversion system and air conditioning device

Abstract

Miniaturizing power conversion systems. [Solution] A power conversion system comprising: a plurality of substrates each carrying a power conversion circuit electrically connected to an AC power line at a branch point; a detection unit that collectively detects common mode noise generated by the plurality of power conversion circuits; and a generation unit that generates a cancellation signal to be output to the power line or earth line based on the level of the common mode noise detected by the detection unit, wherein the number of generation units is less than the number of substrates.

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion system and an air conditioning apparatus. [Background technology]

[0002] A noise reduction device for a power converter that converts power based on the on / off switching of switching elements is known. This noise reduction device includes a noise detection circuit that detects a common-mode noise current, and a noise compensation current supply circuit that generates a noise compensation current in the opposite direction to the noise current in response to the noise current detected by the noise detection circuit and supplies this noise compensation current to a line through which the noise current of the power converter flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-266677 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of a power conversion system having a plurality of power conversion circuits for converting electric power, conventional techniques require the same number of noise compensation current supply circuits as the power conversion circuits, making it difficult to reduce the size of the power conversion system.

[0005] An object of the present disclosure is to reduce the size of a power conversion system. [Means for solving the problem]

[0006] The first aspect is a plurality of substrates each having a power conversion circuit mounted thereon, the power conversion circuit being electrically connected to an AC power line at a branch point; a detection unit that collectively detects common mode noises generated by the plurality of power conversion circuits; a generating unit that generates a cancellation signal to be output to the power supply line or the earth line based on the level of the common mode noise detected by the detecting unit, The generating unit is a power conversion system having a number of power conversion systems that is less than the number of the boards.

[0007] According to the first aspect, common-mode noise generated by the power conversion circuits mounted on the plurality of boards is detected collectively, so that a cancellation signal that reduces the common-mode noise can be generated by a number of generators that is fewer than the number of boards. Because the number of generators is fewer than the number of boards, the power conversion system can be made smaller.

[0008] A second aspect is the power conversion system of the first aspect, The power conversion circuit may be a power conversion system including a circuit for driving a motor.

[0009] According to the second aspect, it is possible to reduce common mode noise generated by the circuit for driving the motor.

[0010] The third aspect is A power conversion system including a substrate on which a plurality of power conversion circuits are mounted, the power conversion circuits being electrically connected to an AC power line at a branch point, the power conversion circuit includes a circuit for driving a motor; a detection unit that collectively detects common mode noises generated by the plurality of power conversion circuits; a generating unit that generates a cancellation signal to be output to the power supply line or the earth line based on the level of the common mode noise detected by the detecting unit, The generation unit is a power conversion system having a number of power conversion circuits that is less than the number of the power conversion circuits.

[0011] According to the third aspect, common-mode noise generated by each of the multiple power conversion circuits mounted on the substrate is detected collectively, so that a cancellation signal that reduces the common-mode noise can be generated by a number of generators that is fewer than the number of power conversion circuits. Because the number of generators is fewer than the number of power conversion circuits, the power conversion system can be made smaller. Furthermore, because the power conversion circuits include a circuit for driving a motor, common-mode noise generated by the circuit for driving the motor can be reduced.

[0012] A fourth aspect is the power conversion system of any one of the first to third aspects, The detection unit may be a power conversion system that includes an annular magnetic core through which the power supply line passes on the power supply side of the branch point, and an auxiliary winding wound around the magnetic core, and outputs a voltage according to the level from the auxiliary winding.

[0013] According to the fourth aspect, the detection unit can detect the magnitude of a common-mode noise current (common-mode current) flowing through the power line passing through the magnetic core as a voltage corresponding to the level of the common-mode noise, and the generation unit can generate a cancellation signal that reduces the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0014] A fifth aspect is the power conversion system of the fourth aspect, The power conversion system may be configured such that the generation unit outputs the cancellation signal to the power supply line on a side closer to the power conversion circuit than the magnetic core.

[0015] According to the fifth aspect, the common mode noise can be reduced by the cancellation signal that is output to the power supply line on the power conversion circuit side rather than the position of the magnetic core.

[0016] A sixth aspect is the power conversion system of the fourth aspect, The power conversion system may be configured such that the generating unit is connected to the power supply line on the power conversion circuit side of the magnetic core and outputs the cancellation signal to the earth line.

[0017] According to the sixth aspect, the common mode noise can be reduced by the cancellation signal output to the earth line.

[0018] A seventh aspect is a power conversion system according to any one of the first to third aspects, the power supply line includes a plurality of branch lines branching from the branch point to the plurality of power conversion circuits, The detection unit may be a power conversion system that includes an annular magnetic core through which the plurality of branch lines pass on the power conversion circuit side of the branch point, and an auxiliary winding wound around the magnetic core, and outputs a voltage according to the level from the auxiliary winding.

[0019] According to the seventh aspect, the detection unit can detect the magnitude of a common-mode noise current (common-mode current) flowing through the plurality of branch lines passing through the magnetic core as a voltage corresponding to the level of the common-mode noise, and the generation unit can generate a cancellation signal that reduces the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0020] An eighth aspect is the power conversion system of the seventh aspect, The power conversion system may be configured such that the generation unit outputs the cancellation signal to the branch line on a side closer to the power conversion circuit than the magnetic core.

[0021] According to the eighth aspect, the common mode noise can be reduced by the cancellation signal that is output to the branch line on the power conversion circuit side rather than the position of the magnetic core.

[0022] A ninth aspect is the power conversion system of the seventh aspect, The power conversion system may be configured such that the generating unit is connected to the branch line on the power conversion circuit side of the magnetic core and outputs the cancellation signal to the earth line.

[0023] According to the ninth aspect, the common mode noise can be reduced by the cancellation signal output to the earth line.

[0024] A tenth aspect is a power conversion system according to any one of the first to third aspects, The detection unit may be a power conversion system that includes an impedance element connected between the power supply line and the earth line, and outputs a voltage according to the level by voltage division by the impedance element.

[0025] According to the tenth aspect, the detection unit can detect the magnitude of a common-mode noise voltage (common-mode voltage) occurring in the impedance element as a voltage corresponding to the level of the common-mode noise, and the generation unit can generate a cancellation signal that reduces the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0026] An eleventh aspect is the power conversion system of the tenth aspect, The power conversion system may be configured such that the generation unit outputs the cancellation signal to the power supply line on a side closer to the power conversion circuit than the detection unit.

[0027] According to the eleventh aspect, the common mode noise can be reduced by the cancellation signal that is output to the power supply line on the power conversion circuit side rather than the position of the detection unit.

[0028] A twelfth aspect is an air conditioner including the power conversion system of any one of the first to eleventh aspects.

[0029] According to the twelfth aspect, the air conditioner includes the power conversion system of any one of the first to eleventh aspects, and therefore the air conditioner can be made smaller by making the power conversion system smaller. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a block diagram showing a first configuration example of a power conversion system according to a first embodiment. [Figure 2] FIG. 4 is a block diagram showing a second configuration example of the power conversion system according to the first embodiment. [Figure 3] FIG. 4 is a block diagram showing a third configuration example of the power conversion system according to the first embodiment. [Figure 4] FIG. 10 is a block diagram showing a fourth configuration example of the power conversion system according to the first embodiment. [Figure 5] FIG. 10 is a block diagram showing a fifth configuration example of the power conversion system according to the first embodiment. [Figure 6] FIG. 2 is a diagram illustrating a first detailed configuration example of a detection unit and a generation unit according to the first embodiment. [Figure 7] FIG. 4 is a diagram illustrating a second detailed configuration example of the detection unit and generation unit according to the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating a third detailed configuration example of the detection unit and generation unit according to the first embodiment. [Figure 9] FIG. 10 is a block diagram showing a first configuration example of a power conversion system according to a second embodiment. [Figure 10] FIG. 10 is a diagram illustrating a first detailed configuration example of a detection unit and a generation unit according to the second embodiment. [Figure 11] FIG. 10 is a diagram illustrating a second example of the detailed configuration of the detection unit and generation unit according to the second embodiment. [Figure 12] FIG. 10 is a block diagram showing a first configuration example of a power conversion system according to a third embodiment. [Figure 13] FIG. 10 is a block diagram showing a second configuration example of the power conversion system according to the third embodiment. [Figure 14] FIG. 11 is a diagram illustrating a first detailed configuration example of a detection unit and a generation unit according to the third embodiment. [Figure 15] FIG. 10 is a block diagram showing a first configuration example of a power conversion system according to a fourth embodiment. [Figure 16] FIG. 10 is a block diagram showing a second configuration example of a power conversion system according to a fourth embodiment. [Figure 17] FIG. 10 is a block diagram showing a first configuration example of a power conversion system according to a fifth embodiment. [Figure 18] FIG. 10 is a block diagram showing a second configuration example of a power conversion system according to a fifth embodiment. [Figure 19] FIG. 13 is a block diagram showing a third configuration example of a power conversion system according to a fifth embodiment. [Figure 20] FIG. 13 is a block diagram showing a first configuration example of a power conversion system according to a sixth embodiment. [Figure 21] FIG. 13 is a block diagram showing a second configuration example of a power conversion system according to a sixth embodiment. [Figure 22] FIG. 13 is a block diagram showing a third configuration example of a power conversion system according to a sixth embodiment. [Figure 23] FIG. 20 is a diagram illustrating a first detailed configuration example of a detection unit and a generation unit according to the sixth embodiment. [Figure 24] FIG. 20 is a diagram illustrating a second detailed configuration example of the detection unit and generation unit according to the sixth embodiment. [Figure 25] FIG. 10 is a block diagram showing a first modified example of the power conversion system. [Figure 26] FIG. 10 is a diagram illustrating a configuration example of a detection unit according to a first modified example of the power conversion system. [Figure 27] FIG. 10 is a block diagram showing a second modified example of the power conversion system. [Figure 28] FIG. 10 is a block diagram showing a third modified example of the power conversion system. [Figure 29] FIG. 2 is a diagram illustrating an example of a configuration of a power conversion circuit. DETAILED DESCRIPTION OF THE INVENTION

[0031] Several embodiments will be described below.

[0032] Fig. 1 is a block diagram showing a first configuration example of a power conversion system according to the first embodiment. A power conversion system 1A shown in Fig. 1 performs forward conversion or frequency conversion on AC input from a power source 10, and supplies the converted DC or the frequency-converted AC to a plurality of loads (in this example, loads 21 and 22).

[0033] The power supply 10 is an AC power supply that supplies AC power. When the power supply 10 is a three-phase AC power supply, the power supply 10 supplies three-phase AC power to the power conversion system 1A. The power supply 10 is, for example, a commercial power supply.

[0034] When the load 21 or the load 22 is a DC load, the power conversion system 1A has a converter function for converting AC power supplied from the power source 10 into DC power to be supplied to the load 21 or the load 22. In this case, the load 21 or the load 22 operates on the DC power supplied from the power conversion system 1A. An example of a DC load is an electronic circuit. The electronic circuit includes, for example, a control circuit that controls the power conversion circuit 31 or the power conversion circuit 32.

[0035] When the load 21 or the load 22 is an AC load, the power conversion system 1A has an inverter function that converts the frequency of AC power supplied from the power source 10 into AC power to be supplied to the load 21 or the load 22. In this case, the load 21 or the load 22 operates on the AC power supplied from the power conversion system 1A. An example of an AC load is a motor.

[0036] All of the multiple loads may be DC loads or AC loads. Alternatively, one or more of the multiple loads may be DC loads and the remaining one or more may be AC ​​loads. For example, the load 21 may be an AC load and the load 22 may be a DC load, or the load 21 may be a DC load and the load 22 may be an AC load.

[0037] The power conversion system 1A is provided, for example, in a refrigeration device 200 that includes a load 21 and a load 22. The refrigeration device 200 is a refrigeration cycle device that includes a compressor driven by an AC motor, which is an example of the load 21 or the load 22. An example of the refrigeration device 200 is an air conditioner that conditions the air in a target space. Note that the device in which the power conversion system 1A is provided is not limited to the refrigeration device 200, and may be other equipment that requires a power conversion function.

[0038] The load 21 or the load 22 may be a three-phase AC motor. A three-phase AC motor is used as an electric motor that drives a compressor provided in a refrigerant circuit of the refrigeration device 200. The three-phase AC motor is, for example, a concentrated winding motor with 4 poles and 6 slots or 6 poles and 9 slots.

[0039] The power conversion system 1A includes a plurality of substrates 41 and 42, a detection unit 50, and a generation unit 60.

[0040] The plurality of boards 41, 42 each carry a power conversion circuit that is electrically connected to an AC power line 70 at a branch point 80. The boards 41, 42 are circuit boards such as printed circuit boards. The board 41 carries the power conversion circuit 31. The board 42 carries the power conversion circuit 32. The plurality of power conversion circuits 31, 32 are electrically connected to the power source 10 via the power line 70.

[0041] The power supply line 70 is a path for supplying single-phase or three-phase AC power generated by the power supply 10. When supplying three-phase AC power, the power supply line 70 includes three-phase (S-phase, R-phase, and T-phase) power lines. The power supply line 70 includes multiple branch lines branching from a branch point 80 to multiple power conversion circuits 31, 32. The branch line 71 electrically connects the branch point 80 and the power conversion circuit 31. The branch line 72 electrically connects the branch point 80 and the power conversion circuit 32.

[0042] The multiple power conversion circuits 31, 32 are circuits that perform forward conversion or frequency conversion of AC power input via power supply line 70. Power conversion circuit 31 is an inverter circuit that frequency converts AC power input via branch line 71 into AC power to be supplied to load 21, or a converter circuit that performs forward conversion into DC power to be supplied to load 21. Power conversion circuit 32 is an inverter circuit that frequency converts AC power input via branch line 72 into AC power to be supplied to load 22, or a converter circuit that performs forward conversion into DC power to be supplied to load 22.

[0043] The substrate 41 may further be equipped with one or more power conversion circuits that convert AC input via one or more branch lines further branching off from the branch line 71 into DC or AC. The substrate 42 may further be equipped with one or more power conversion circuits that convert AC input via one or more branch lines further branching off from the branch line 72 into DC or AC.

[0044] Fig. 29 is a diagram showing an example of the configuration of a power conversion circuit. The power conversion circuit 30 shown in Fig. 29 includes a circuit for driving a motor M and is an example of the power conversion circuit 31 or the power conversion circuit 32. The power conversion circuit 30 is an inverter circuit that converts the frequency of three-phase AC power input via the power supply line 70 into three-phase AC power to be supplied to the motor M, which is an example of the load 21 or the load 22. The power conversion circuit 30 includes a converter 102, a DC link 103, and an inverter 104 as circuits for driving the motor M.

[0045] Converter 102 is a circuit that converts AC input via power line 70 into DC, for example, converting three-phase AC into DC. Converter 102 is, for example, a diode bridge circuit in which a plurality of (for example, six) diodes are connected in a bridge configuration. These diodes full-wave rectify the AC voltage input from power line 70 and convert it into a DC voltage. Converter 102 may also be a voltage conversion circuit with a circuit format other than a diode bridge circuit. Converter 102 supplies the converted DC power to inverter 104 via DC link 103.

[0046] The DC link 103 is a portion to which DC output from the converter 102 is supplied. The DC link 103 includes, for example, a pair of DC buses 111 and 112 connecting the converter 102 and the inverter 104, and a capacitor 113 connected between the pair of DC buses 111 and 112. A voltage Vdc of the DC link 103 is a potential difference between the pair of DC buses 111 and 112, and is approximately equal to a DC voltage generated across the capacitor 113. The DC voltage Vdc is input to the inverter 104.

[0047] The inverter 104 is a circuit that converts the DC from the DC link 103 into AC, for example, converting the DC into three-phase AC. The inverter 104 supplies the converted AC power to the motor M. The inverter 104 is, for example, a bridge circuit in which a plurality of (for example, six) switching elements 104a are connected in a bridge shape. The inverter 104 converts the DC power from the DC link 103 into AC power for the motor M by turning on or off the plurality of switching elements 104a in accordance with a command S generated by a control unit (not shown).

[0048] In Fig. 1, the detection unit 50 and the generation unit 60 function as an active noise canceller. The active noise canceller detects common mode noise generated by the power conversion circuit, and outputs a cancellation signal generated based on the level of the detected common mode noise to the power line or the earth line. By outputting the cancellation signal to the power line or the earth line, the common mode noise flowing into the power supply electrically connected to the power line and the earth line is reduced. The cancellation signal is a signal that reduces common mode noise and is also called a compensation signal.

[0049] Common mode noise generated by the power conversion circuit 31 is transmitted through the earth line 91 and the branch line 71 via stray capacitance between the load 21 or the power conversion circuit 31 and the earth line 91. The common mode noise generated by the power conversion circuit 31 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 31. The earth line 91 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0050] Common mode noise generated by the power conversion circuit 32 is transmitted through the earth line 92 and the branch line 72 via stray capacitance between the load 22 or the power conversion circuit 32 and the earth line 92. The common mode noise generated by the power conversion circuit 32 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 32. The earth line 92 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0051] The power conversion system 1A according to the first embodiment includes a detection unit 50 and a generation unit 60 as the active noise canceller according to the first embodiment. The active noise canceller according to the first embodiment detects a common mode noise current Ic (common mode current), and outputs a compensation current Io generated based on the level of the detected common mode current to a power line 70 or an earth line 91. The active noise canceller according to the first embodiment is a current detection / current output type active noise cancellation circuit.

[0052] The common mode noise current Ic (common mode current) is an example of common mode noise generated by the multiple power conversion circuits 31 and 32. The compensation current Io is an example of a cancellation signal generated based on the level of the detected common mode noise.

[0053] The detection unit 50 in the active noise canceller according to the first embodiment detects the common mode noise current Ic flowing in the power line 70 as common mode noise generated by the multiple power conversion circuits 31, 32. The detection unit 50 detects the noise current Ic on the power supply 10 side of the branch point 80. The detection unit 50 collectively detects the common mode noise generated by the multiple power conversion circuits 31, 32 by detecting the noise current Ic flowing in the power line 70 between the power supply 10 and the branch point 80. The detection unit 50 detects the noise current Ic flowing in the power line 70 between the power supply 10 and the branch point 80 using a transformer, for example.

[0054] The generating unit 60 in the active noise canceller according to the first embodiment generates a compensation current Io to be output to the power line 70 or the earth line 91 based on the level of the noise current Ic detected by the detecting unit 50. The generating unit 60 outputs the compensation current Io to the power line 70 on the power conversion circuit 31 side of the detecting unit 50. Alternatively, the generating unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the detecting unit 50, and outputs the compensation current Io to the earth line 91. For example, the generating unit 60 injects the compensation current Io into the power line 70 or the earth line 91 based on the detected noise current Ic so as to reduce common-mode noise flowing in the power supply 10. For example, the generating unit 60 injects the compensation current Io into the power line 70 or the earth line 91 via a capacitor.

[0055] In the active noise canceller according to the first embodiment, common-mode noise generated by the power conversion circuits 31, 32 mounted on each of the multiple boards 41, 42 is collectively detected as noise current Ic by the detection unit 50. This collectively detecting noise current Ic enables the generation of compensation current Io, which is a cancellation signal that reduces the common-mode noise generated by the power conversion circuits 31, 32 mounted on each of the boards 41, 42, by a number of generation units 60 fewer than the number of boards 41, 42. Because the number of generation units 60 is fewer than the number of boards 41, 42, the power conversion system 1A can be made smaller. Furthermore, when at least one of the power conversion circuits 31, 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0056] The active noise canceller according to the first embodiment collectively detects the common mode noise generated by each of the power conversion circuits 31 and 32 using a common detection unit 50. Therefore, the power conversion system according to the first embodiment can be made smaller than a configuration in which the common mode noise generated by the power conversion circuit 31 and the common mode noise generated by the power conversion circuit 32 are detected by separate detection units.

[0057] Fig. 2 is a block diagram showing a second configuration example of the power conversion system according to the first embodiment. In the second configuration example, descriptions of parts common to the first configuration example described above will be omitted. The power conversion system 1B shown in Fig. 2 differs from the power conversion system 1A shown in Fig. 1 in that it includes a substrate 40 on which are mounted a plurality of power conversion circuits (in this example, power conversion circuits 31 and 32) electrically connected to an AC power line 70 at a branch point 80.

[0058] The substrate 40 is a circuit board such as a printed circuit board, and may further include one or more power conversion circuits that convert AC input via one or more branch lines branching off from the branch line 71 or the branch line 72 into DC or AC.

[0059] In the active noise canceller according to the first embodiment, common-mode noise generated by each of the power conversion circuits 31, 32 mounted on the substrate 40 is collectively detected as a noise current Ic by the detection unit 50. This collectively detecting the common-mode noise makes it possible to generate a compensation current Io, which is a cancellation signal that reduces the common-mode noise generated by each of the power conversion circuits 31, 32 mounted on the substrate 40, using a number of generation units 60 that is fewer than the number of power conversion circuits 31, 32. Because the number of generation units 60 is fewer than the number of power conversion circuits 31, 32, the power conversion system 1B can be made smaller. Furthermore, when at least one of the power conversion circuits 31, 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0060] Fig. 3 is a block diagram showing a third configuration example of the power conversion system according to the first embodiment. In the third configuration example, descriptions of parts common to the above-mentioned configuration examples will be omitted. The power conversion system 1C shown in Fig. 3 differs from the power conversion system 1A shown in Fig. 1 in that the generation unit 60 is mounted on a substrate 41.

[0061] FIG. 4 is a block diagram showing a fourth configuration example of the power conversion system according to the first embodiment. In the fourth configuration example, descriptions of parts common to the above-mentioned configuration examples will be omitted. The power conversion system 1D shown in FIG. 4 differs from the power conversion system 1A shown in FIG. 1 in that a branch point 80 is mounted on a board 41. The board 41 may be equipped with the branch point 80 and the generating unit 60. When the power conversion system 1D is mounted in an air conditioner, the board 41 may be an inverter board mounted in an outdoor unit, and the board 42 may be an inverter board mounted in an indoor unit.

[0062] Fig. 5 is a block diagram showing a fifth configuration example of the power conversion system according to the first embodiment. In the fifth configuration example, descriptions of parts common to the above-mentioned configuration examples will be omitted. The power conversion system 1E shown in Fig. 5 differs from the power conversion system 1A shown in Fig. 1 in that a detection unit 50 is mounted on a substrate 41. The substrate 41 may be equipped with the detection unit 50, a branch point 80, and a generation unit 60.

[0063] In the power conversion systems 1C, 1D, and 1E, the substrates 41 and 42 may be integrated together like the substrate 40 of the power conversion system 1B.

[0064] Fig. 6 is a diagram showing a first detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Aa shown in Fig. 6 is applicable to any of the above-mentioned power conversion systems 1A to 1E. Fig. 6 illustrates a configuration in which the generation unit 60 injects the compensation current Io into an injection point 60a on the earth line 91.

[0065] The detector 50 includes an annular magnetic core 51 through which the power line 70 passes on the side closer to the power source 10 than the branch point 80, and an auxiliary winding 52 wound around the magnetic core 51. The detector 50 outputs a voltage Vc from the auxiliary winding 52 that corresponds to the level of common-mode noise generated by the multiple power conversion circuits 31, 32. The detector 50 detects the magnitude of a common-mode noise current Ic (common-mode current) flowing through the power line 70 that passes through the magnetic core 51 as a voltage Vc that corresponds to the level of the common-mode noise. The generator 60 generates a compensation current Io, which is a cancellation signal that reduces the common-mode noise, based on the voltage Vc that corresponds to the level of the common-mode noise.

[0066] The generating unit 60 is connected to the power supply line 70 on the power conversion circuit 31 side of the magnetic core 51, and outputs the compensation current Io to the earth line 91. As a result, the compensation current Io output to the earth line 91 can reduce the noise current Ic generated by the power conversion circuits 31 and 32.

[0067] The noise current Ic includes a common-mode noise current I1 generated by the power conversion circuit 31 and a common-mode noise current I2 generated by the power conversion circuit 32. Based on the detected noise current Ic, the generating unit 60 injects a compensation current Io into the power supply line 70 or the earth line 91 so as to reduce the common-mode noise flowing in the power supply 10.

[0068] Fig. 7 is a diagram showing a second detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Ab shown in Fig. 7 is applicable to any of the above-described power conversion systems 1A to 1E. Fig. 7 illustrates a configuration in which the generation unit 60 injects the compensation current Io into an injection point 60a on the power line 70 on the power conversion circuit 31 side relative to the position of the magnetic core 51.

[0069] The generator 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation current Io to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generator 60 injects the compensation current Io into an injection point 60a on the branch line 71 between the branch point 80 and the power conversion circuit 31. Based on the detected noise current Ic, the generator 60 injects the compensation current Io into the branch line 71 so as to reduce the common mode noise flowing in the power supply 10.

[0070] Fig. 8 is a diagram showing a third detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Ac shown in Fig. 8 is also applicable to any of the above-described power conversion systems 1A to 1E. Fig. 8 illustrates a configuration in which the generation unit 60 injects the compensation current Io into an injection point 60a on the power line 70 on the power conversion circuit 31 side relative to the position of the magnetic core 51.

[0071] The generator 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation current Io to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generator 60 injects the compensation current Io into an injection point 60a on the power line 70 between the magnetic core 51 and the branch point 80. Based on the detected noise current Ic, the generator 60 injects the compensation current Io into the power line 70 between the magnetic core 51 and the branch point 80 so as to reduce the common mode noise flowing in the power supply 10.

[0072] 9 is a block diagram showing a first configuration example of a power conversion system according to the second embodiment. In the second embodiment, the same configurations, actions, and effects as those of the first embodiment will not be described by citing the above description.

[0073] The power conversion system 2A according to the second embodiment includes a detection unit 50 and a generation unit 60 as the active noise canceller according to the second embodiment. The active noise canceller according to the second embodiment detects a common mode noise current Ic (common mode current), and outputs a compensation voltage Vo generated based on the level of the detected common mode current to a power line 70. The active noise canceller according to the second embodiment is a current detection / voltage output type active noise cancellation circuit.

[0074] The compensation voltage Vo is an example of a cancellation signal that is generated based on the level of the detected common-mode noise.

[0075] The generation unit 60 in the active noise canceller according to the second embodiment generates a compensation voltage Vo to be output to the power line 70 based on the level of the noise current Ic detected by the detection unit 50. The generation unit 60 outputs the compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the detection unit 50. For example, the generation unit 60 measures a common mode voltage generated in the power line 70 based on the level of the noise current Ic, and applies a compensation voltage Vo having an opposite polarity to the common mode voltage to the power line 70, thereby reducing the noise current Ic. The generation unit 60 applies the compensation voltage Vo to the power line 70 via a transformer, for example.

[0076] In the active noise canceller according to the second embodiment, common-mode noise generated by the power conversion circuits 31, 32 mounted on each of the multiple boards 41, 42 is collectively detected as noise current Ic by the detection unit 50. This collectively detecting noise allows the generation of compensation voltage Vo, which is a cancellation signal that reduces the common-mode noise generated by the power conversion circuits 31, 32 mounted on each of the boards 41, 42, by using a number of generation units 60 fewer than the number of boards 41, 42. Because the number of generation units 60 is fewer than the number of boards 41, 42, the power conversion system 2A can be made smaller. Furthermore, when at least one of the power conversion circuits 31, 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0077] The boards 41 and 42 of the power conversion system 2A may be integrated like the board 40 of the power conversion system 1B. The board 41 of the power conversion system 2A may have an expanded mounting range like the board 41 of the power conversion systems 1C to 1E.

[0078] Fig. 10 is a diagram showing a first detailed configuration example of an active noise canceller (a detection unit 50 and a generation unit 60) according to the second embodiment. A power conversion system 2Aa shown in Fig. 10 is applicable to the above-described power conversion system 2A. Fig. 10 illustrates a configuration in which the generation unit 60 outputs a compensation voltage Vo to a power line 70 between a branch point 80 and a power conversion circuit 31.

[0079] The detector 50 detects the magnitude of a common-mode noise current Ic (common-mode current) flowing through the power line 70 passing through the magnetic core 51 as a voltage Vc corresponding to the level of the common-mode noise. The generator 60 generates a compensation voltage Vo, which is a cancellation signal that reduces the common-mode noise, based on the voltage Vc corresponding to the level of the common-mode noise.

[0080] The generator 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generator 60 outputs the compensation voltage Vo to a branch line 71 between the branch point 80 and the power conversion circuit 31. The generator 60 applies a voltage Vp corresponding to the voltage Vc to the primary winding of the transformer 62. As a result, the compensation voltage Vo, which has a polarity opposite to that of the common-mode voltage generated in the power line 70, is applied to the branch line 71 by the secondary winding of the transformer 62, thereby reducing the noise current Ic flowing into the power supply 10 to approximately zero.

[0081] Fig. 11 is a diagram showing a second detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the second embodiment. The power conversion system 2Ab shown in Fig. 11 is applicable to the above-described power conversion system 2A. Fig. 11 illustrates a configuration in which the generation unit 60 outputs the compensation voltage Vo to the power line 70 between the branch point 80 and the detection unit 50.

[0082] The generator 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generator 60 outputs the compensation voltage Vo to the power line 70 between the branch point 80 and the magnetic core 51. The generator 60 applies a voltage Vp corresponding to the voltage Vc to the primary winding of the transformer 62. As a result, the compensation voltage Vo, which has an opposite polarity to the common mode voltage generated on the power line 70, is applied to the power line 70 by the secondary winding of the transformer 62, thereby reducing the noise current Ic flowing into the power supply 10 to approximately zero.

[0083] 12 is a block diagram showing a first configuration example of a power conversion system according to the third embodiment. In the third embodiment, the same configurations, actions, and effects as those of the above-described embodiments will not be described by citing the above descriptions.

[0084] The power conversion system 3A according to the third embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the third embodiment. The active noise canceller according to the third embodiment detects a common mode noise current Ic (common mode current), and outputs a compensation current Io generated based on the level of the detected common mode current to a power line 70 or an earth line 91. The active noise canceller according to the third embodiment is a current detection / current output type active noise cancellation circuit.

[0085] The detection unit 50 in the active noise canceller according to the third embodiment detects the common mode noise current Ic flowing through the power line 70 as common mode noise generated by the multiple power conversion circuits 31, 32. The detection unit 50 detects the noise current Ic on the power conversion circuit 31, 32 side of the branch point 80. The detection unit 50 detects the noise current Ic, which is the sum of the noise current flowing through the branch line 71 and the noise current flowing through the branch line 72, thereby collectively detecting the common mode noise generated by the multiple power conversion circuits 31, 32. The detection unit 50 detects the noise current Ic flowing through the branch lines 71, 72, for example, using a transformer.

[0086] The generating unit 60 in the active noise canceller according to the third embodiment generates a compensation current Io to be output to the power line 70 or the earth line 91 based on the level of the noise current Ic detected by the detecting unit 50. The generating unit 60 outputs the compensation current Io to the power line 70 on the power source 10 side of the branch point 80. Alternatively, the generating unit 60 is connected to the power line 70 on the power source 10 side of the branch point 80 and outputs the compensation current Io to the earth line 91. The generating unit 60 injects the compensation current Io into the power line 70 or the earth line 91 based on, for example, the detected noise current Ic so as to reduce the common mode noise flowing in the power source 10. The generating unit 60 injects the compensation current Io into the power line 70 or the earth line 91 via a capacitor, for example.

[0087] Fig. 13 is a block diagram showing a second configuration example of a power conversion system according to the third embodiment. In the second configuration example, descriptions of parts common to the first configuration example described above will be omitted. In the power conversion system 3B shown in Fig. 13, the generation unit 60 outputs the compensation current Io to the power line 70 on the power conversion circuit 31 side relative to the positions of the branch point 80 and the detection unit 50. Alternatively, the generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side relative to the positions of the branch point 80 and the detection unit 50, and outputs the compensation current Io to the earth line 91.

[0088] The boards 41 and 42 of the power conversion systems 3A and 3B may be integrated together like the board 40 of the power conversion system 1B. The board 41 of the power conversion systems 3A and 3B may have an expanded mounting range like the board 41 of the power conversion systems 1C to 1E.

[0089] Fig. 14 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the third embodiment. The configuration of the power conversion system 3Ba shown in Fig. 14 is applicable to the above-mentioned power conversion system 3B. Fig. 14 illustrates a configuration in which the generation unit 60 injects the compensation current Io into an injection point 60a on the earth line 91.

[0090] The detector 50 includes an annular magnetic core 51 through which the plurality of branch lines 71, 72 pass on the power conversion circuits 31, 32 side of the branch point 80, and an auxiliary winding 52 wound around the magnetic core 51. The detector 50 outputs a voltage Vc from the auxiliary winding 52 that corresponds to the level of common-mode noise generated by the plurality of power conversion circuits 31, 32. The detector 50 detects the magnitude of a common-mode noise current Ic (common-mode current) flowing through the plurality of branch lines 71, 72 that pass through the magnetic core 51 as a voltage Vc that corresponds to the level of the common-mode noise. The generator 60 generates a compensation current Io, which is a cancellation signal that reduces the common-mode noise, based on the voltage Vc that corresponds to the level of the common-mode noise.

[0091] The generating unit 60 is connected to the power supply line 70 on the power conversion circuit 31 side of the magnetic core 51, and outputs the compensation current Io to the earth line 91. As a result, the compensation current Io output to the earth line 91 can reduce the noise current Ic generated by the power conversion circuits 31 and 32.

[0092] 15 is a block diagram showing a first configuration example of a power conversion system according to the fourth embodiment. In the fourth embodiment, the same configurations, actions, and effects as those of the above-described embodiments will not be described by citing the above descriptions.

[0093] The power conversion system 4A according to the fourth embodiment includes a detection unit 50 and a generation unit 60 as the active noise canceller according to the fourth embodiment. The active noise canceller according to the fourth embodiment detects a common mode noise current Ic (common mode current), and outputs a compensation voltage Vo generated based on the level of the detected common mode current to a power line 70. The active noise canceller according to the fourth embodiment is a current detection / voltage output type active noise cancellation circuit.

[0094] The generating unit 60 in the active noise canceller according to the fourth embodiment outputs a compensation voltage Vo to the power supply line 70 based on the noise current Ic detected by the detecting unit 50 so as to reduce the common mode noise flowing in the power supply 10. The generating unit 60 outputs the compensation voltage Vo to the power supply line 70 on the power supply 10 side of the detecting unit 50. For example, the generating unit 60 measures a common mode voltage occurring in the power supply line 70 based on the level of the noise current Ic, and applies a compensation voltage Vo having an opposite polarity to the common mode voltage to the power supply line 70, thereby reducing the common mode noise flowing in the power supply 10. The generating unit 60 applies the compensation voltage Vo to the power supply line 70 via a transformer, for example.

[0095] Fig. 16 is a block diagram showing a second configuration example of a power conversion system according to the fourth embodiment. In the second configuration example, descriptions of parts common to the first configuration example described above will be omitted. The power conversion system 4B shown in Fig. 16 differs from the power conversion system 4A shown in Fig. 15 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side relative to the position of the detection unit 50.

[0096] The boards 41 and 42 of the power conversion systems 4A and 4B may be integrated like the board 40 of the power conversion system 1B. The board 41 of the power conversion systems 4A and 4B may have an expanded mounting range like the board 41 of the power conversion systems 1C to 1E.

[0097] 17 is a block diagram showing a first configuration example of a power conversion system according to the fifth embodiment. In the fifth embodiment, the same configurations, actions, and effects as those of the above-described embodiments will not be described by citing the above descriptions.

[0098] A power conversion system 5A according to the fifth embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the fifth embodiment. The active noise canceller according to the fifth embodiment detects a common mode noise voltage Vc (common mode voltage), and outputs a compensation current Io generated based on the level of the detected common mode voltage to a power supply line 70 or an earth line 91. The active noise canceller according to the fifth embodiment is a voltage detection / current output type active noise cancellation circuit.

[0099] The common mode noise voltage Vc (common mode voltage) is an example of common mode noise generated by the plurality of power conversion circuits 31 and 32.

[0100] The detection unit 50 in the active noise canceller according to the fifth embodiment detects the common mode noise voltage Vc generated on the power line 70 as common mode noise generated by the multiple power conversion circuits 31, 32. Because all points on the power line 70 are at approximately the same potential, the detection unit 50 detects the noise voltage Vc at any point on the power line 70. By detecting the noise voltage Vc at any point on the power line 70, the detection unit 50 collectively detects the common mode noise generated by the multiple power conversion circuits 31, 32. The detection unit 50 detects the noise voltage Vc using, for example, impedance elements such as a capacitor and a resistor.

[0101] The generating unit 60 in the active noise canceller according to the fifth embodiment generates a compensation current Io to be output to the power supply line 70 or the earth line 91, based on the level of the noise voltage Vc detected by the detecting unit 50. The generating unit 60 outputs the compensation current Io to the power supply line 70 on the power supply 10 side of the position of the detecting unit 50. Alternatively, the generating unit 60 is connected to the power supply line 70 on the power supply 10 side of the position of the detecting unit 50, and outputs the compensation current Io to the earth line 91.

[0102] Fig. 18 is a block diagram showing a second configuration example of a power conversion system according to the fifth embodiment. In the second configuration example, descriptions of parts common to the above-mentioned first configuration example will be omitted. In a power conversion system 5B shown in Fig. 18, the generation unit 60 outputs a compensation current Io to a power line 70 on the power conversion circuit 31 side relative to the positions of the detection unit 50 and the branch point 80. Alternatively, the generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side relative to the positions of the detection unit 50 and the branch point 80, and outputs the compensation current Io to a ground line 91.

[0103] Fig. 19 is a block diagram showing a third configuration example of a power conversion system according to the fifth embodiment. In the third configuration example, descriptions of parts common to the above-mentioned configuration examples will be omitted. The power conversion system 5C shown in Fig. 19 differs from the power conversion system 5B shown in Fig. 18 in that the detection unit 50 detects the noise voltage Vc on the power conversion circuit 31 side rather than the position of the branch point 80.

[0104] The boards 41 and 42 of the power conversion systems 5A, 5B, and 5C may be integrated like the board 40 of the power conversion system 1B. The board 41 of the power conversion systems 5A, 5B, and 5C may have an expanded mounting range like the board 41 of the power conversion systems 1C to 1E.

[0105] 20 is a block diagram showing a first configuration example of a power conversion system according to the sixth embodiment. In the sixth embodiment, the same configurations, actions, and effects as those of the above-described embodiments will not be described by citing the above descriptions.

[0106] A power conversion system 6A according to the sixth embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the sixth embodiment. The active noise canceller according to the sixth embodiment detects a common mode noise voltage Vc (common mode voltage), and outputs a compensation voltage Vo generated based on the level of the detected common mode voltage to a power line 70. The active noise canceller according to the sixth embodiment is a voltage detection / voltage output type active noise cancellation circuit.

[0107] The generation unit 60 in the active noise canceller according to the sixth embodiment generates a compensation voltage Vo to be output to the power supply line 70, based on the level of the noise voltage Vc detected by the detection unit 50. The generation unit 60 outputs the compensation voltage Vo to the power supply line 70 on the power supply 10 side of the position of the detection unit 50.

[0108] Fig. 21 is a block diagram showing a second configuration example of a power conversion system according to the sixth embodiment. In the second configuration example, descriptions of parts common to the above-mentioned first configuration example will be omitted. The power conversion system 6B shown in Fig. 21 differs from the power conversion system 6A shown in Fig. 20 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side relative to the position of the detection unit 50.

[0109] Fig. 22 is a block diagram showing a third configuration example of a power conversion system according to the sixth embodiment. In the third configuration example, descriptions of parts common to the above-mentioned configuration examples will be omitted. The power conversion system 6C shown in Fig. 22 differs from the power conversion system 6B shown in Fig. 21 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side relative to the position of the detection unit 50.

[0110] The boards 41 and 42 of the power conversion systems 6A, 6B, and 6C may be integrated like the board 40 of the power conversion system 1B. The board 41 of the power conversion systems 6A, 6B, and 6C may have an expanded mounting range like the board 41 of the power conversion systems 1C to 1E.

[0111] Fig. 23 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the sixth embodiment. The configuration of the power conversion system 6Ba shown in Fig. 23 is applicable to the above-mentioned power conversion system 6B. Fig. 23 illustrates a configuration in which the generation unit 60 applies the compensation voltage Vo to the branch line 71 between the branch point 80 and the power conversion circuit 31.

[0112] The detection unit 50 includes a plurality of impedance elements 53, 54 connected in series between the power supply line 70 and the earth line 91. The impedance elements 53, 54 are capacitors. The detection unit 50 outputs a voltage Vc from the impedance element 54 according to the level of common-mode noise generated by the plurality of power conversion circuits 31, 32 by voltage division using the impedance elements 53, 54. The detection unit 50 detects the magnitude of the common-mode noise voltage Vc (common-mode voltage) generated in the impedance element 54 as a voltage Vc according to the level of the common-mode noise. Then, the generation unit 60 generates a compensation voltage Vo, which is a cancellation signal that reduces the common-mode noise, based on the voltage Vc according to the level of the common-mode noise.

[0113] The generating unit 60 outputs the compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the detecting unit 50. As a result, the compensation voltage Vo output to the power line 70 can reduce the noise voltage Vc generated by the power conversion circuits 31 and 32.

[0114] Fig. 24 is a diagram showing a second detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the sixth embodiment. The configuration of the power conversion system 6Ca shown in Fig. 24 is applicable to the above-mentioned power conversion system 6C. Fig. 24 illustrates a configuration in which the generation unit 60 applies the compensation voltage Vo to the branch line 71 between the detection unit 50 and the power conversion circuit 31.

[0115] The generating unit 60 outputs the compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the detecting unit 50. As a result, the compensation voltage Vo output to the power line 70 can reduce the noise voltage Vc generated by the power conversion circuits 31 and 32.

[0116] FIG. 25 is a block diagram showing a first modified example of a power conversion system. In the first modified example, the description of the same configuration, action, and effect as those of the above-described embodiments will be omitted by citing the above description. In the power conversion systems according to the above-described embodiments, the number of detection units 50 and generation units 60 is the same. However, as in a power conversion system 7A shown in FIG. 25, the number of detection units 50 may be less than the number of generation units 60.

[0117] The power conversion system 7A includes a plurality of substrates 41, 42, and 43, a detection unit 50, and generation units 60A and 60B.

[0118] The substrate 43 is mounted with a power conversion circuit 33 electrically connected to an AC power line 70 at a branch point 80. The power conversion circuit 33 is electrically connected to a power source 10 via the power line 70. The power line 70 includes a branch line 73 that branches from the branch point 80 to the power conversion circuit 33. The branch line 73 electrically connects the branch point 80 and the power conversion circuit 33. The power conversion circuit 33 is a circuit that performs forward conversion or frequency conversion on the AC input via the power line 70 and supplies the converted power to the load 23. The substrate 43 may further be mounted with one or more power conversion circuits that convert the AC input via one or more branch lines further branching from the branch line 73 into DC or AC.

[0119] Common mode noise generated by the power conversion circuit 33 is transmitted through the earth line 93 and the branch line 73 via stray capacitance between the load 23 or the power conversion circuit 33 and the earth line 93. The common mode noise generated by the power conversion circuit 33 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 33. The earth line 93 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0120] The detection unit 50 according to the first modification detects the common mode noise current Ic flowing through the power line 70 as common mode noise generated by the multiple power conversion circuits 31, 32, and 33. The detection unit 50 detects the noise current Ic on the power conversion circuit 31, 32, and 33 side of the branch point 80. The detection unit 50 detects the noise current Ic, which is a sum of the noise current flowing through the branch line 71, the noise current flowing through the branch line 72, and the noise current flowing through the branch line 73, thereby collectively detecting the common mode noise generated by the multiple power conversion circuits 31, 32, and 33. The detection unit 50 detects the noise current Ic flowing through the branch lines 71, 72, and 73 using a transformer, for example.

[0121] 26 is a diagram showing a configuration example of a detector according to a first modified example of the power conversion system. The detector 50 includes an annular magnetic core 51 through which branch wires 71, 72, and 73 pass, and a plurality of auxiliary windings 52a and 52b wound around the magnetic core 51. The detector 50a outputs a voltage generated by the auxiliary winding 52a to the generator 60A. The detector 50b outputs a voltage generated by the auxiliary winding 52b to the generator 60B.

[0122] 25 , the generator 60A generates a compensation current Io that reduces common-mode noise generated by the multiple power conversion circuits 31, 32, and 33 based on the voltage generated by the auxiliary winding 52a of the detector 50. The generator 60A injects the generated compensation current Io into the branch line 71 or the earth line 91. The generator 60B generates a compensation current Io that reduces common-mode noise generated by the multiple power conversion circuits 31, 32, and 33 based on the voltage generated by the auxiliary winding 52b of the detector 50. The generator 60B injects the generated compensation current Io into the branch line 72 or the earth line 92.

[0123] FIG. 27 is a block diagram showing a second modified example of a power conversion system. In the second modified example, the description of the same configuration, operation, and effects as those of the above-described embodiments will be omitted by citing the above description. In the power conversion systems according to the above-described embodiments, the detector 50 collectively detects common mode noise generated by all power conversion circuits electrically connected to the branch point 80. However, as in a power conversion system 7B shown in FIG. 27, the detector 50 may collectively detect common mode noise generated by some of the power conversion circuits among all the power conversion circuits electrically connected to the branch point 80.

[0124] 27, the detection unit 50 collectively detects common mode noise generated by some of the power conversion circuits 31, 32 among all the power conversion circuits 31, 32, 33 electrically connected to the branch point 80. The power conversion system 7B includes a noise filter 11 (for example, a common mode choke coil) provided on the branch line 73, and the noise filter 11 reduces the common mode noise generated by the power conversion circuit 33.

[0125] FIG. 28 is a block diagram showing a third modified example of a power conversion system. In the third modified example, the same configurations, actions, and effects as those of the above-described embodiments will not be described by citing the above descriptions. In the power conversion systems according to the above-described embodiments, the power line 70 has one branch point. However, as in a power conversion system 7C shown in FIG. 28, the power line 70 may have multiple branch points.

[0126] The power conversion system 7C includes a plurality of boards 41, 42, 43, and 44, a detection unit 50, and a generation unit 60. The board 44, the power conversion circuit 34, the load 24, the branch line 74, and the earth line 94 have been described above and will not be described further below. The plurality of boards 41, 42, 43, and 44 are equipped with power conversion circuits 31, 32, 33, and 34 that are electrically connected to an AC power line 70 at a branch point 81. The plurality of boards 41 and 42 are equipped with power conversion circuits 31 and 32 that are electrically connected to the AC power line 70 at a branch point 80. The plurality of boards 43 and 44 are equipped with power conversion circuits 33 and 34 that are electrically connected to the AC power line 70 at a branch point 82.

[0127] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. [Explanation of symbols]

[0128] 1A,1B,1C,1D,1E,2A,3A,3B,4A,4B,5A,5B,5C,6A,6B,6C,7A,7B,7C Power conversion system 10 Power supply 11 Noise Filter 21, 22, 23, 24 Load 30, 31, 32, 33, 34 Power conversion circuit 40, 41, 42, 43, 44 Board 50 Detector 51 Magnetic Core 52 Auxiliary Winding 53,54 Impedance elements 60 Generation part 60a Injection Point 61 Generation circuit 62 Trans 70 Power line 71, 72, 73, 74 Branch lines 80, 81, 82 Junction 90 grand 91, 92, 93, 94 Earth wire 200 Refrigeration equipment

Claims

1. a plurality of substrates (41, 42, 43, 44) on which power conversion circuits (31, 32, 33, 34) are mounted, the power conversion circuits being electrically connected to an AC power line (70) at a branch point (80); a detection unit (50) for collectively detecting common mode noises generated by the plurality of power conversion circuits; a generation unit (60) that generates a cancellation signal to be output to the power supply line or the earth line (91) based on the level of the common mode noise detected by the detection unit, A power conversion system, wherein the number of generating units is less than the number of substrates.

2. The power conversion system of claim 1 , wherein the power conversion circuitry includes circuitry for driving a motor.

3. A power conversion system including a substrate (40) on which a plurality of power conversion circuits (31, 32) are mounted, the power conversion circuits being electrically connected to an AC power line (70) at a branch point (80), the power conversion circuit includes a circuit for driving a motor; a detection unit (50) for collectively detecting common mode noises generated by the plurality of power conversion circuits; a generating unit (60) that generates a cancellation signal to be output to the power supply line or the earth line based on the level of the common mode noise detected by the detecting unit, A power conversion system, wherein the number of the generation units is less than the number of the power conversion circuits.

4. 4. The power conversion system according to claim 1, wherein the detection unit includes an annular magnetic core (51) through which the power supply line passes on a side closer to the power supply than the branch point, and an auxiliary winding (52) wound around the magnetic core, and outputs a voltage according to the level from the auxiliary winding.

5. The power conversion system according to claim 4 , wherein the generation unit outputs the cancellation signal to the power supply line on a side closer to the power conversion circuit than the magnetic core.

6. The power conversion system according to claim 4 , wherein the generating unit is connected to the power supply line on a side closer to the power conversion circuit than the magnetic core, and outputs the cancellation signal to the earth line.

7. the power supply line includes a plurality of branch lines (71, 72) branching from the branch point to a plurality of the power conversion circuits, 4. The power conversion system according to claim 1, wherein the detection unit includes an annular magnetic core (51) through which the plurality of branch lines pass on the power conversion circuit side of the branch point, and an auxiliary winding (52) wound around the magnetic core, and outputs a voltage according to the level from the auxiliary winding.

8. The power conversion system according to claim 7 , wherein the generation unit outputs the cancellation signal to the branch line on a side closer to the power conversion circuit than the magnetic core.

9. The power conversion system according to claim 7 , wherein the generating unit is connected to the branch line on a side closer to the power conversion circuit than the magnetic core, and outputs the cancellation signal to the earth line.

10. 4. The power conversion system according to claim 1, wherein the detection unit includes an impedance element (53, 54) connected between the power supply line and the earth line, and outputs a voltage according to the level by voltage division by the impedance element.

11. The power conversion system according to claim 10 , wherein the generation unit outputs the cancellation signal to the power supply line on a side closer to the power conversion circuit than the detection unit.

12. An air conditioner comprising the power conversion system according to any one of claims 1 to 3.

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