JP6962152B2 - Shield structure of in-vehicle power conversion device and in-vehicle power conversion device - Google Patents

Description

The present invention relates to a shield structure of an in-vehicle power conversion device and an in-vehicle power conversion device provided with the shield structure.

In recent years, a plug-in hybrid vehicle (PHEV) capable of effectively improving the fuel consumption rate (fuel efficiency) of a vehicle by using an engine and an electric motor in combination has been put into practical use. In addition, an electric vehicle (EV) that uses only an electric motor as a power source and does not emit exhaust gas has also been put into practical use. Such plug-in hybrid vehicles and electric vehicles are equipped with high-voltage batteries (battery modules) in which a plurality of secondary batteries (battery cells) such as lithium-ion batteries are connected in series. In addition, an in-vehicle charger (on-board charger) for charging a high-voltage battery using an external AC power supply (commercial power system) and an in-vehicle charger that steps down the voltage of the high-voltage battery to, for example, 12V and supplies it to in-vehicle electrical components. A DC-DC converter or the like is installed. In the present specification, for example, a voltage of DC60V or higher is referred to as a high voltage.

In such an in-vehicle power converter such as an in-vehicle charger or a DC-DC converter, noise is radiated when converting a voltage, a frequency, or the like due to a switching operation by a switching element such as an FET. Then, the radiated noise is combined with a conductive housing such as an in-vehicle charger, and further, for example, a stray capacitance (parasitic capacitance) formed between the ground connected to the housing and a power supply line or the like is generated. There is a problem that it goes out to the power supply line or the like as conduction noise.

On the other hand, conventionally, a shield has been used in order to reduce noise radiated from electronic components such as switching elements. Here, Patent Document 1 discloses a power supply device including an electromagnetic shield portion configured to cover the periphery of a component such as a switching element that is a source of noise.

More specifically, this power supply device includes a substrate on which heat-generating components such as FETs, diodes, transformers, and coils are mounted, a fixing member for fixing the substrate, and a lid portion attached to the fixing member and covering the substrate. An electromagnetic shield is provided between the lid and the heat generating component. Further, the electromagnetic shield portion is configured to cover the periphery of the component that is a source of noise, such as a switching element, among the heat generating components. According to this power supply device, it is possible to improve heat dissipation of heat-generating components while reducing noise.

Japanese Unexamined Patent Publication No. 2016-119395

Here, when the shield structure of the power supply device described in Patent Document 1 is to be applied to the in-vehicle charger mounted on the above-mentioned plug-in hybrid vehicle or electric vehicle, the electromagnetic shield portion is directly applied. Alternatively, since it is in contact with the lid (housing) via the conductive heat dissipation part, if the electromagnetic shield part having the same potential as the lid (housing) is connected to the ground of the substrate, it can be used as an in-vehicle charger or the like. The noise radiated from the switching element used is coupled to the lid portion (housing) via the electromagnetic shield portion and goes around the lid portion (housing). Therefore, as described above, the noise around the lid (housing) causes stray capacitance (parasitic capacitance) formed between the ground of the substrate connected to the lid (housing) and the power supply line. There is a risk that it will appear on the power supply line as conduction noise. If a shield made of an insulating material such as ferrite is used instead of the conductive electromagnetic shield (that is, when noise radiated from the switching element is shielded by an insulating shield such as ferrite). , The shield needs to be very thick and cannot be a viable solution.

The present invention has been made to solve the above problems, and has a shield structure of an in-vehicle power conversion device capable of further reducing noise of the in-vehicle power conversion device while improving heat dissipation performance, and a shield structure of the in-vehicle power conversion device. An object of the present invention is to provide an in-vehicle power conversion device having the shield structure.

The shield structure of the vehicle-mounted power conversion device according to the present invention is a shield structure of the vehicle-mounted power conversion device mounted on a vehicle, in which a first ground and a second ground insulated from each other are formed, and a switching element is formed. A wiring board on which a power conversion circuit that converts input power (for example, converts voltage and frequency) and outputs it, and a conductive shield member provided so as to cover at least a switching element. The conductive housing that houses the wiring board, the first heat-dissipating member that has insulation between the switching element and the shield member, and the insulation that is interposed between the shield member and the housing. It is provided with a second heat dissipation member having properties, the first ground is electrically connected to the housing, the second ground is electrically connected to the shield member, and is connected to the ground electrode of the switching element. It is characterized by being.

According to the shield structure of the vehicle-mounted power conversion device according to the present invention, since the conductive shield member is provided so as to cover the switching element, the noise radiated from the switching element is combined with the shield member. Here, since the shield member is electrically connected to the second ground to which the ground electrode of the switching element is connected, the noise coupled with the shield member is returned to the switching element side via the second ground. On the other hand, since the second ground is insulated from the first ground electrically connected to the housing, the noise coupled with the shield member is transmitted to the housing and the first ground to which the housing is connected. Is prevented. That is, the transmission of noise to the housing is blocked. Since a second heat radiating member having an insulating property is interposed between the shield member and the housing, it is surely prevented that the shield member and the housing are electrically connected. Therefore, even if a stray capacitance (parasitic capacitance) is formed between the first ground connected to the housing and the power supply line or the like, it is possible to prevent noise from going out to the power supply line or the like as conduction noise. Further, a first heat radiating member having an insulating property is interposed between the switching element and the shield member, and a second heat radiating member having an insulating property is interposed between the shield member and the housing. Therefore, the heat generated by the switching element can be transferred to the housing via the first heat radiating member, the shield member, and the second heat radiating member, and high heat radiating property can be exhibited. As a result, it is possible to further reduce the noise (radiation noise and conduction noise) of the in-vehicle power conversion device while improving the heat dissipation performance.

In the shield structure of the vehicle-mounted power conversion device according to the present invention, a first ground and a third ground insulated from the second ground are formed on the wiring board, and the power conversion circuits are primary isolated from each other. It is preferable that the side circuit and the secondary side circuit are provided, the second ground is the ground of the primary side circuit, and the third ground is the ground of the secondary side circuit.

Further, in the shield structure of the in-vehicle power conversion device according to the present invention, it is preferable that the housing is electrically connected to the body ground of the vehicle.

In the shield structure of the vehicle-mounted power conversion device according to the present invention, it is preferable that the power conversion circuit is an AC-DC converter circuit, a DC-DC converter circuit, or a DC-AC converter circuit.

In this case, it is possible to further reduce noise while improving the heat dissipation performance of the AC-DC converter circuit, the DC-DC converter circuit, or the DC-AC converter circuit.

In the shield structure of the vehicle-mounted power conversion device according to the present invention, it is preferable that the power conversion circuit is an inverter circuit.

In this case, it is possible to further reduce noise while improving the heat dissipation performance of the inverter circuit.

The vehicle-mounted power conversion device according to the present invention is characterized by including a shield structure of any of the above-mentioned vehicle-mounted power conversion devices.

According to the shield structure of the in-vehicle power conversion device according to the present invention, since any of the above shield structures is provided, noise (radiation noise and conduction noise) of the in-vehicle power conversion device can be reduced while improving heat dissipation performance. It can be further reduced.

According to the present invention, it is possible to further reduce noise (radiation noise and conduction noise) of an in-vehicle power conversion device while improving heat dissipation performance.

It is a schematic diagram (cross-sectional view) which shows the vehicle-mounted power conversion device according to the embodiment, and the shield structure of the vehicle-mounted power conversion device. It is a block diagram which shows the functional structure of the in-vehicle power conversion apparatus which concerns on embodiment. It is a graph which shows the measurement result of the noise level of each of the shield structure of the vehicle-mounted power conversion device according to the embodiment, and the vehicle-mounted power conversion device (FIG. 4) according to a comparative example. It is a schematic diagram (cross-sectional view) which shows the vehicle-mounted power conversion apparatus (example which does not have a shield member) which concerns on a comparative example.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

First, the vehicle-mounted power conversion device 1 and the shield structure of the vehicle-mounted power conversion device 1 according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view schematically showing an in-vehicle power conversion device 1 and a shield structure of the in-vehicle power conversion device 1. FIG. 2 is a block diagram showing a functional configuration of the in-vehicle power conversion device 1. In the present embodiment, as the vehicle-mounted power conversion device 1, an vehicle-mounted charger mounted on a plug-in hybrid vehicle (PHEV), an electric vehicle (EV), or the like will be described as an example (hereinafter, “vehicle-mounted charging”). It is called "vessel 1").

The in-vehicle charger 1 is mounted on a plug-in hybrid vehicle (PHEV) or an electric vehicle (EV), and is an AC power source (for example, AC200V) supplied from the outside of the vehicle through a pair of AC lines (AC inputs) 71 and 71. Is converted to a desired DC voltage and output from the DC lines (DC output) 73, 73 to charge a high-voltage battery configured by connecting a plurality of secondary batteries (battery cells) such as a lithium ion battery in series. It is a charger to do.

The in-vehicle charger 1 mainly includes a PFC (Power Factor Rectifier) circuit 3 and an isolated DC-DC converter circuit 5. The RFC circuit 3 is a diode bridge (bridge rectifier circuit) that converts (rectifies) AC voltage input from AC lines 71 and 71 into DC voltage by performing full-wave rectification using four rectifying diodes, and In addition to a smoothing capacitor that reduces ripple after rectification, it is equipped with a power factor improvement (PFC) circuit that brings the power factor of the power supply closer to 1.

The isolated DC-DC converter circuit 5 uses a transformer (switching transformer) to perform voltage conversion (DC-DC conversion) of the DC voltage output from the PFC circuit 3. In the isolated DC-DC converter circuit 5, the primary side (input side) circuit 5a and the secondary side (output side) circuit 5b are electrically insulated by this transformer. Therefore, in the isolated DC-DC converter circuit 5, it is possible to cut off conduction noise and prevent electric shock. As the isolated DC-DC converter circuit 5, a known method, for example, a flyback converter or a forward converter can be used. The RFC circuit 3 and the isolated DC-DC converter circuit 5 correspond to the power conversion circuit described in the claims. The DC voltage converted to a desired voltage by the isolated DC-DC converter circuit 5 is output from the DC lines 73 and 73.

The housing 10 of the vehicle-mounted charger 1 is made of a conductive material such as metal, and is formed in a substantially rectangular parallelepiped shape. Here, the housing 10 may be formed of a material having conductivity such as metal, or for example, a thin film having conductivity is attached to a material having no conductivity such as resin. It may be formed by being applied or by applying a conductive coating.

A wiring board 20 and the like are housed inside the housing 10. The wiring board 20 is configured by stacking a plurality of insulating layers on which a wiring pattern (ground pattern (details will be described later), power supply pattern, signal pattern) is formed, for example. The insulating layer is, for example, a rectangular thin plate formed of FR-4 (Flame Retardant Type 4). The wiring pattern is formed from, for example, copper foil.

The wiring board 20 includes, for example, a diode bridge and a smoothing capacitor constituting the above-mentioned PFC circuit 3, and a MOS- constituting an isolated DC-DC converter circuit 5 (primary side circuit 5a and secondary side circuit 5b). Electronic components such as a switching element 25 (hereinafter referred to as "FET 25") such as a FET and a transformer (switching transformer) are mounted. Here, the primary side circuit 5a of the isolated side DC-DC converter circuit 5 includes the FET 25 and the primary side of the transformer. On the other hand, the secondary side circuit 5b includes the secondary side of the transformer and, for example, a choke coil and a capacitor that rectify and smooth the output thereof.

The wiring board 20 is formed with a first ground (pattern) 21, a second ground (pattern) 22, and a third ground (pattern) 23 that are insulated from each other. The first ground 21 is a ground that is electrically connected (conducted) to the housing 10. The second ground 22 is the ground of the PFC circuit 3 described above and the primary side circuit 5a of the isolated DC-DC converter circuit 5. Therefore, the ground electrode (− terminal) of the FET 25 is connected to the second ground 22. The third ground 23 is the ground of the secondary side circuit 5b of the above-mentioned isolated DC-DC converter circuit 5. Here, the housing 10 is connected (conducting) to the body ground (body ground) 75 of the vehicle body by, for example, a bolt or a cable.

A conductive shield member 30 is provided on the wiring board 20 so as to cover the mounted FET 25. The shield member 30 is formed of, for example, a conductive metal foil (copper foil or the like). The shield member 30 is electrically connected (conducted) to the second ground 22.

A first heat radiating member 41 having an insulating property, for example, formed in a sheet shape, is interposed between the FET 25 and the shield member 30. Similarly, a second heat radiating member 42, which has an insulating property and is formed in a sheet shape, is interposed between the shield member 30 and the housing 10. Therefore, the heat generated by the switching operation of the FET 25 is transmitted from the FET 25 to the housing 10 via the first heat radiating member 41, the shield member 30, and the second heat radiating member 42, and is radiated from the housing 10 to the outside.

With the above-described configuration, the conductive shield member 30 is provided so as to cover the FET 25, so that the noise radiated from the FET 25 is combined with the shield member 30. Here, since the shield member 30 is electrically connected (conducted) to the second ground 22 to which the ground electrode of the FET 25 is connected, the noise coupled with the shield member 30 is transmitted to the FET 25 via the second ground 22. Returned to the side. On the other hand, since the second ground 22 is insulated from the first ground 21 that is electrically connected to the housing 10, noise combined with the shield member 30 causes the housing 10 and the housing 10 to be connected. It is prevented from being transmitted to the first ground 21. That is, the transmission of noise to the housing 10 and the first ground 21 is cut off. Since the second heat radiating member 42 having an insulating property is interposed between the shield member 30 and the housing 10, it is surely prevented that the shield member 30 and the housing 10 are electrically connected. Therefore, even if stray capacitance (parasitic capacitance) is formed between the first ground 21 connected to the housing 10 and the AC lines 71, 71, etc., noise is emitted to the AC lines 71, 71, etc. as conduction noise. It is prevented from going on.

Therefore, in order to confirm the noise reduction effect of the shield structure of the in-vehicle charger 1 according to the present embodiment, the conduction emission of the AC line was measured in the measurement system based on CISPR11. Subsequently, the noise reduction effect of the shield structure of the vehicle-mounted charger 1 according to the present embodiment will be described with reference to FIGS. 3 and 4 by showing the measurement results. FIG. 4 is a cross-sectional view schematically showing an in-vehicle power conversion device (example without a shield member 30) according to a comparative example. Here, as a comparative example, as shown in FIG. 4, an in-vehicle charger not provided with the shield member 30 is used, and the difference in noise level depending on the presence or absence of the shield member 30 (including the difference in the connected ground), that is, The shielding effect of the shield member 30 was evaluated.

FIG. 3 is a graph showing the measurement results of the conduction emissions of the shield structure of the vehicle-mounted charger 1 according to the embodiment and the vehicle-mounted charger without the shield member 30 according to the comparative example shown in FIG. .. The graph of FIG. 3 shows the noise levels of the AC lines 71 and 71. The horizontal axis of this graph is frequency (MHz), and the vertical axis is noise level (dBμV).

As shown in FIG. 3, according to the shield structure of the vehicle-mounted charger 1 according to the present embodiment, the noise level is the total measurement frequency as compared with the vehicle-mounted charger without the shield member 30 according to the comparative example. It was confirmed that the decrease was about 10 (dBμV) in the region.

Here, in the vehicle-mounted charger (vehicle-mounted charger without the shield member 30) according to the comparative example shown in FIG. 4, when noise is radiated due to the switching operation of the FET 25, the radiated noise is generated. It is transmitted to the housing 10 via a stray capacitance (parasitic capacitance) formed between the housing 10 and the housing 10. The noise transmitted to the housing 10 is conducted from the housing 10 to the first ground 21 of the wiring board 20. Then, the noise conducted to the first ground 21 is conducted to the AC lines 71 and 71 via the stray capacitance (parasitic capacitance) formed between the first ground 21 and the AC lines (power supply lines) 71 and 71. It is thought that it will be done.

On the other hand, according to the shield structure of the vehicle-mounted charger 1 according to the present embodiment, since the conductive shield member 30 is provided so as to cover the FET 25, the noise radiated from the FET 25 is combined with the shield member 30. do. Here, since the shield member 30 is electrically connected (conducted) to the second ground 22 to which the ground electrode of the FET 25 is connected, the noise coupled with the shield member 30 is transmitted to the FET 25 via the second ground 22. Returned to the side. On the other hand, since the second ground 22 is insulated from the first ground 21 that is electrically connected to the housing 10, noise combined with the shield member 30 causes the housing 10 and the housing 10 to be connected. It is prevented from being transmitted to the first ground 21. That is, the transmission of noise to the housing 10 and the first ground 21 is cut off. Since the second heat radiating member 42 having an insulating property is interposed between the shield member 30 and the housing 10, it is surely prevented that the shield member 30 and the housing 10 are electrically connected to each other. .. Therefore, even if stray capacitance (parasitic capacitance) is formed between the first ground 21 connected to the housing 10 and the AC lines 71, 71 (power supply line), the noise is the conduction noise of the AC line 71, It is prevented from going out to 71 and so on. As a result, as described above, the noise level can be reduced by about 10 (dBμV) in the entire measurement frequency range.

Further, according to the present embodiment, the first heat radiating member 41 having an insulating property is interposed between the FET 25 and the shield member 30, and the shield member 30 and the housing 10 have an insulating property. 2 A heat radiating member 42 is interposed. Therefore, the heat generated by the FET 25 can be transferred to the housing 10 via the first heat radiating member 41, the shield member 30, and the second heat radiating member 42, and the heat radiating property (effect) can be enhanced.

As a result of the above, according to the present embodiment, it is possible to further reduce the noise (radiation noise and conduction noise) of the in-vehicle charger 1 while improving the heat dissipation performance.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiment, the present invention has been described by taking the case where the present invention is applied to the in-vehicle charger 1 (AC-DC converter) as an example. It can also be applied to a power conversion circuit that converts a frequency or the like and outputs it, for example, a DC-DC converter that converts a high voltage to 12V, a DC-AC converter, an inverter circuit (motor driver circuit), or the like.

In the above embodiment, the shield member 30 covers the FET 25, but the shield member 30 may cover the FET 25 and other electronic components that emit noise. Similarly, the first heat radiating member 41 may be interposed between these other electronic components and the shield member 30 in addition to the FET 25.

In the above embodiment, the MOS-FET is used as the switching element, but the switching element used is not limited to the MOS-FET, and for example, an IGBT may be used according to the requirements and the like.

1 Car charger (car power converter)
3 RFC circuit 5 Insulated DC-DC converter circuit 5a Primary side circuit 5b Secondary side circuit 10 Housing 20 Wiring board 21 1st ground 22 2nd ground 23 3rd ground 25 FET (switching element)
30 Shield member 41 First heat dissipation member 42 Second heat dissipation member 71 AC line (AC input)
73 DC line (DC output)
75 Body ground (body ground)

Claims (6)

It is a shield structure of the in-vehicle power conversion device mounted on the vehicle.
A wiring board on which a first ground and a second ground that are isolated from each other are formed, and a power conversion circuit that includes a switching element and converts input power and outputs it is mounted.
A conductive shield member provided so as to cover at least the switching element, and
A conductive housing for accommodating the wiring board and
A first heat radiating member having an insulating property, which is interposed between the switching element and the shield member,
A second heat radiating member having an insulating property, which is interposed between the shield member and the housing, is provided.
The first ground is electrically connected to the housing and is connected to the housing.
The shield structure of an in-vehicle power conversion device, wherein the second ground is electrically connected to the shield member and is also connected to the ground electrode of the switching element. A third ground insulated from the first ground and the second ground is formed on the wiring board.
The power conversion circuit has a primary side circuit and a secondary side circuit that are isolated from each other.
The second ground is the ground of the primary side circuit, and is
The shield structure of an in-vehicle power conversion device according to claim 1, wherein the third ground is a ground of the secondary circuit. The shield structure of an in-vehicle power conversion device according to claim 1 or 2, wherein the housing is electrically connected to the body ground of the vehicle. The vehicle-mounted power conversion device according to any one of claims 1 to 3, wherein the power conversion circuit is an AC-DC converter circuit, a DC-DC converter circuit, or a DC-AC converter circuit. Shield structure. The shield structure of an in-vehicle power conversion device according to any one of claims 1 to 3, wherein the power conversion circuit is an inverter circuit. An in-vehicle power conversion device comprising the shield structure of the in-vehicle power conversion device according to any one of claims 1 to 5.

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