Power conversion device

Abstract

The present application provides a power conversion device, having: an AC / DC conversion circuit; a first capacitor and a second capacitor, connected in series between a first output terminal and a second output terminal on the output side of the AC / DC conversion circuit; and a conductive body part formed on at least a part of the housing, one end of the first capacitor is electrically connected to the first output terminal, the other end of the first capacitor is electrically connected to the conductive body part, one end of the second capacitor is electrically connected to the second output terminal, the other end of the second capacitor is electrically connected to the conductive body part, the conductive body part is not connected to a reference potential, and is in an open state.

Description

Technical Field

[0001] This invention relates to power conversion devices. Background Technology

[0002] Patent document 1 describes an AC adapter with an LC filter connected to the output side of an AC / DC conversion circuit.

[0003] Furthermore, to achieve higher frequency AC / DC conversion circuits, it is known to use switching elements formed from compound semiconductors such as GaN (gallium nitride). By increasing the frequency of the AC / DC conversion circuit, it is possible to miniaturize the power conversion device.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2009-253994

[0005] However, in Patent Document 1, when the AC / DC conversion circuit is made more frequent, noise caused by switching is generated in the high-frequency band, so there is a possibility that the noise radiated from the power line on the AC side (input side) and the cable on the DC side (output side) cannot be suppressed. Summary of the Invention

[0006] The purpose of this invention is to provide a power conversion device that can suppress noise even at high frequencies.

[0007] One aspect of the present invention is a power conversion device comprising: an AC / DC conversion circuit; a first capacitor and a second capacitor connected in series between a first output terminal and a second output terminal on the output side of the AC / DC conversion circuit; and a conductive portion formed in at least a portion of a housing, wherein one end of the first capacitor is electrically connected to the first output terminal, the other end of the first capacitor is electrically connected to the conductive portion, one end of the second capacitor is electrically connected to the second output terminal, the other end of the second capacitor is electrically connected to the conductive portion, and the conductive portion is not connected to a reference potential and is in an open state.

[0008] The power conversion device according to the present invention can also suppress noise in the high-frequency band. Attached Figure Description

[0009] Figure 1 This is a circuit diagram schematically representing the power conversion device of the first embodiment.

[0010] Figure 2 It is a graph showing the relationship between the noise level and frequency radiated from the power conversion device of the first embodiment.

[0011] Figure 3 This is a graph showing the relationship between the noise level and frequency radiated from the power conversion device of the first comparative example.

[0012] Figure 4 This is a graph showing the relationship between the noise level and frequency of the horizontally polarized waves of the power conversion devices of the second to fourth comparative examples.

[0013] Figure 5 This is a graph showing the relationship between the noise level and frequency of the vertically polarized waves of the power conversion devices of the second to fourth comparative examples.

[0014] Figure 6 This is a perspective view schematically representing the power conversion device of the first embodiment.

[0015] Figure 7 This is a circuit diagram schematically illustrating the power conversion device of the second embodiment. Detailed Implementation

[0016] Hereinafter, embodiments of the power conversion device of the present invention will be described in detail based on the accompanying drawings. However, the present invention is not limited to these embodiments. Each embodiment is illustrative, and of course, partial substitutions or combinations of the structures shown in different embodiments are possible. From the second embodiment onwards, descriptions of matters identical to those in the first embodiment are omitted, and only the differences are described. In particular, the same effects achieved by the same structures are not mentioned sequentially in each embodiment.

[0017] (First Implementation)

[0018] Figure 1 This is a circuit diagram schematically illustrating the power conversion device of the first embodiment. (e.g.) Figure 1 As shown, the power conversion device 1 includes: an AC / DC conversion circuit 10, a first input terminal 11 and a second input terminal 12, a first output terminal 13 and a second output terminal 14, a first capacitor 21 and a second capacitor 22, and a conductive part 51. The power conversion device 1 is, for example, an AC adapter that converts an AC voltage signal input from a power supply 100 into a DC voltage signal and outputs it to an external electronic device (not shown) on the output side.

[0019] The AC / DC conversion circuit 10, for example, has a transistor (GaN-FET) formed of a compound semiconductor such as GaN (gallium nitride) as a switching element. The switching frequency of the GaN-FET is higher than that of a transistor (Si-MOSFET) formed of silicon (silicon). The GaN-FET, used as a power semiconductor, can, for example, switch at a frequency of 1000 kHz or less. As a result, miniaturization of the passive components used in the power conversion device 1 is possible, thereby enabling miniaturization of the power conversion device 1. Furthermore, the material of the switching element of the AC / DC conversion circuit 10 is not limited to GaN, and other materials may also be used.

[0020] The first input terminal 11 and the second input terminal 12 are located on the input side of the AC / DC conversion circuit 10. The first input terminal 11 is connected to the AC / DC conversion circuit 10 via a first input wiring L11. The second input terminal 12 is connected to the AC / DC conversion circuit 10 via a second input wiring L12. A power supply 100 is connected to the first input terminal 11 and the second input terminal 12, and an AC voltage signal is input from the power supply 100 to the first input terminal 11 and the second input terminal 12.

[0021] In this embodiment, the AC / DC conversion circuit 10 is connected to two power supply lines: a first input wiring L11 and a second input wiring L12. The first input wiring L11 is the power supply line on the non-grounded side, also known as the L-phase. The second input wiring L12 is the power supply line on the grounded side, also known as the N-phase. That is, in this embodiment, the AC / DC conversion circuit 10 is not connected to a GND (ground) line.

[0022] The first output terminal 13 and the second output terminal 14 are located on the output side of the AC / DC conversion circuit 10. The first output terminal 13 is connected to the AC / DC conversion circuit 10 via a first output wiring L13. The second output terminal 14 is connected to the AC / DC conversion circuit 10 via a second output wiring L14. An external electronic device is connected to the first output terminal 13 and the second output terminal 14, and a DC voltage signal is output to the external electronic device from the first output terminal 13 and the second output terminal 14.

[0023] A first capacitor 21 and a second capacitor 22 are connected in series between the first output terminal 13 and the second output terminal 14 on the output side of the AC / DC conversion circuit 10. One end of the first capacitor 21 is electrically connected to the first output terminal 13, and the other end of the first capacitor 21 is electrically connected to the conductor portion 51. One end of the second capacitor 22 is electrically connected to the second output terminal 14, and the other end of the second capacitor 22 is connected to the conductor portion 51.

[0024] The first capacitor 21 and the second capacitor 22 are so-called Y capacitors, which are capable of suppressing noise radiated from the first output wiring L13 and the second output wiring L14 on the output side of the AC / DC conversion circuit 10.

[0025] Conductor portion 51 is formed on housing 50 (see reference) Figure 6 At least a portion of the AC / DC conversion circuit 10. The conductive part 51 is formed of a metallic material such as copper. The conductive part 51 may be configured to cover the entire power conversion device 1 or to cover at least a portion of the AC / DC conversion circuit 10.

[0026] In this embodiment, the conductor portion 51 is in an open state where it is not connected to a fixed potential. Specifically, the conductor portion 51 is not connected to the reference potential 101 on the input side, nor is it connected to the ground (reference potential) on the external electronic device side connected to the output side.

[0027] With this structure, no signal path is formed between the conductor portion 51 and the ground (reference potential) on the external electronic device side, returning to the output side via wiring (first output wiring L13 and second output wiring L14). Furthermore, no signal path is formed between the conductor portion 51 and the input side via the reference potential 101 on the input side, returning to the input side via wiring (first input wiring L11 and second input wiring L12). Therefore, common-mode noise generated by the operation of the AC / DC conversion circuit 10 is contained within the AC / DC conversion circuit 10 side by the first capacitor 21, the second capacitor 22, and the conductor portion 51. As a result, the power conversion device 1 can suppress noise radiated from the wiring on the input side and the wiring on the output side of the AC / DC conversion circuit 10.

[0028] Figure 2 It is a graph showing the relationship between the noise level and frequency radiated from the power conversion device of the first embodiment. Figure 3 This is a graph showing the relationship between the noise level and frequency radiated from the power conversion device of the first comparative example. Figure 4 This is a graph showing the relationship between the noise level and frequency of the horizontally polarized waves of the power conversion devices of the second to fourth comparative examples. Figure 5 This is a graph showing the relationship between the noise level and frequency of the vertically polarized waves of the power conversion devices of the second to fourth comparative examples.

[0029] Figure 3 The power conversion device of the first comparative example shown differs from the first embodiment in that it does not include a first capacitor 21 and a second capacitor 22. Figure 4 and Figure 5The difference between the power conversion devices shown in the second to fourth comparative examples is that the first capacitor 21 and the second capacitor 22 are not provided on the output side, but a noise countermeasure unit is provided on the input side. Specifically, the second comparative example provides a common-mode choke coil as a noise countermeasure unit on the input side. The third comparative example, in addition to providing a common-mode choke coil as a noise countermeasure unit on the input side, also provides a so-called X capacitor and an inductor. The fourth comparative example, in addition to providing a common-mode choke coil, an X capacitor, and an inductor as noise countermeasure units on the input side, also provides an X capacitor and a common-mode choke coil.

[0030] like Figure 2 As shown in Figure 1, it can be seen that the power conversion device of the first embodiment and Figure 3 Compared to the first comparative example shown in Figure 2, the noise level can be suppressed. Specifically, the power conversion device of the first embodiment can more effectively reduce the noise level in the frequency band of 30MHz and above and 200MHz and below.

[0031] like Figure 4 and Figure 5 As shown, in the power conversion devices of the second to fourth comparative examples, by providing a noise countermeasure unit on the input side, it is possible to reduce the noise level within a specified frequency band (e.g., around 80MHz). If for... Figure 4 and Figure 5 The charts 3 and 4 shown are Figure 2 By comparing the diagrams shown in Figure 1, it can be seen that the power conversion device 1 of the first embodiment can effectively reduce the noise level over a wider frequency band. That is, it is shown that the power conversion device 1 of the first embodiment can effectively suppress the noise transmitted from the AC / DC conversion circuit 10 to the first output terminal 13 and the second output terminal 14 by providing the first capacitor 21 and the second capacitor 22 on the output side.

[0032] In this way, even when the switching elements of the AC / DC conversion circuit 10 operate at high frequencies, the power conversion device 1 of the first embodiment can suppress the radiation of high-frequency band noise (e.g., frequencies above 30 MHz and below 200 MHz) from the wiring on the input side and the wiring on the output side.

[0033] Figure 6 This is a perspective view schematically illustrating the power conversion device of the first embodiment. (e.g.) Figure 6 As shown, an AC / DC conversion circuit 10 with a switching element 18, a first input terminal 11, a second input terminal 12, a first capacitor 21, and a second capacitor 22 are mounted on a substrate 20. The substrate 20 is a flat insulating substrate, such as a printed circuit board like epoxy glass, a ceramic substrate like an alumina substrate, or a flexible substrate like polyimide.

[0034] Power cables 103 are connected to the first input terminal 11 and the second input terminal 12. Additionally, power cables 103 are connected to the first output terminal 13 and the second output terminal 14 of the substrate 20. Figure 6 (Shown omitted) An output connector 30 is connected. The output connector 30 is an interface circuit for connecting to external electronic devices.

[0035] exist Figure 6 An output connector 30 is disposed between the first capacitor 21 and the second capacitor 22 and the AC / DC conversion circuit 10. The positions of the first capacitor 21 and the second capacitor 22 are not limited to this and can be appropriately varied. For example, the first capacitor 21 and the second capacitor 22 may also be disposed between the AC / DC conversion circuit 10 and the output connector 30. The first capacitor 21 and the second capacitor 22 are respectively connected to the AC / DC conversion circuit 10 via wiring formed on the substrate 20. Furthermore, the first capacitor 21 and the second capacitor 22 are connected to the conductive part 51 via conductive lines.

[0036] The conductive portion 51 is formed as the housing 50 of the power conversion device 1. The conductive portion 51 is cylindrical and is configured to at least cover the periphery of the AC / DC conversion circuit 10. Alternatively, the conductive portion 51 may be box-shaped and configured to cover the entire power conversion device 1. In addition, the area and arrangement of the conductive portion 51 may be appropriately varied according to the noise frequency band. Furthermore, the conductive portion 51 may also be formed, for example, by adhering to the inner surface of the resin housing 50.

[0037] As described above, the power conversion device 1 of this embodiment includes: an AC / DC conversion circuit 10, a first capacitor 21 and a second capacitor 22 connected in series between a first output terminal 13 and a second output terminal 14 on the output side of the AC / DC conversion circuit 10, and a conductive portion 51 formed in at least a portion of the housing 50. One end of the first capacitor 21 is electrically connected to the first output terminal 13, and the other end of the first capacitor 21 is electrically connected to the conductive portion 51. One end of the second capacitor 22 is electrically connected to the second output terminal 14, and the other end of the second capacitor 22 is electrically connected to the conductive portion 51. The conductive portion 51 is not connected to the reference potential 101 and is in an open state.

[0038] Therefore, even when the switching elements of the AC / DC conversion circuit 10 use GaN and the AC / DC conversion circuit 10 operates at high frequency, the common-mode noise generated by the operation of the AC / DC conversion circuit 10 is contained within the AC / DC conversion circuit 10 by the first capacitor 21, the second capacitor 22, and the conductor portion 51. As a result, the power conversion device 1 is able to suppress noise radiated from the wiring on the input side and the wiring on the output side of the AC / DC conversion circuit 10, even at high frequencies.

[0039] (Second Implementation)

[0040] Figure 7 This is a circuit diagram schematically illustrating the power conversion device according to the second embodiment. In the second embodiment, the difference from the first embodiment lies in the fact that a common-mode choke coil 40 is also provided on the output side of the AC / DC conversion circuit 10.

[0041] Specifically, such as Figure 7 As shown, in the power conversion device 1A of the second embodiment, a common mode choke coil 40 is disposed between the AC / DC conversion circuit 10 and the first capacitor 21 and the second capacitor 22.

[0042] The common-mode choke coil 40 has a first inductor 41 and a second inductor 42 that are magnetically coupled to each other. That is, mutual inductance is formed between the first inductor 41 and the second inductor 42.

[0043] One end of the first inductor 41 is connected to the AC / DC conversion circuit 10. The other end of the first inductor 41 is electrically connected to the first capacitor 21 and the first output terminal 13. One end of the second inductor 42 is connected to the AC / DC conversion circuit 10. The other end of the second inductor 42 is electrically connected to the second capacitor 22 and the second output terminal 14.

[0044] The common-mode choke coil 40 can have any structure, but preferably, the first inductor 41 and the second inductor 42 are integrally formed. Integral, for example, means having the coils forming the first inductor 41 and the coils forming the second inductor 42 wound on a common magnetic core (e.g., a ferrite core) made of a magnetic material. However, it is not limited to an integral form; the common-mode choke coil 40 can be any structure that magnetically couples the inductors. The inductors of the common-mode choke coil 40 can be formed on separately divided magnetic cores or can be composed of planar coils.

[0045] With this structure, the power conversion device 1A of the second embodiment can suppress common-mode noise transmitted in the first output wiring L13 and the second output wiring L14.

[0046] Furthermore, the above-described embodiments are for the purpose of easily understanding the content of the present invention and are not intended to limit the interpretation of the present invention. The present invention can be modified / improved without departing from its spirit, and its equivalents are also included in the present invention.

[0047] Explanation of reference numerals in the attached figures

[0048] 1, 1A…Power conversion device; 10…AC / DC conversion circuit; 11…First input terminal; 12…Second input terminal; 13…First output terminal; 14…Second output terminal; 18…Switching element; 20…Substrate; 21…First capacitor; 22…Second capacitor; 30…Output connector; 40…Common mode choke coil; 41…First inductor; 42…Second inductor; 50…Housing; 51…Conductor part; 100…Power supply; 101…Reference potential; 103…Power cable; L11…First input wiring; L12…Second input wiring; L13…First output wiring; L14…Second output wiring.

Claims

1. A power conversion device, comprising: AC / DC conversion circuit; A first capacitor and a second capacitor are connected in series between the first output terminal and the second output terminal on the output side of the aforementioned AC / DC conversion circuit; and The conductive portion is formed in at least a portion of the housing of the aforementioned power conversion device. One end of the first capacitor is electrically connected to the first output terminal, and the other end of the first capacitor is electrically connected to the conductive part. One end of the second capacitor is electrically connected to the second output terminal, and the other end of the second capacitor is electrically connected to the conductive part. The aforementioned conductive part is not connected to the reference potential and is in an open state.

2. The power conversion device according to claim 1, wherein, A common-mode choke coil is provided between the AC / DC conversion circuit and the first capacitor and the second capacitor.

3. The power conversion device according to claim 1 or 2, wherein, The aforementioned conductive portion is configured to cover the area surrounding the aforementioned AC / DC conversion circuit.

4. The power conversion device according to claim 1 or 2, wherein, The above AC / DC conversion circuit has a first input wiring on the non-grounded side and a second input wiring on the grounded side.

5. The power conversion device according to claim 3, wherein, The above AC / DC conversion circuit has a first input wiring on the non-grounded side and a second input wiring on the grounded side.

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