JP5869207B2 - Circuit component mounting structure and its mounting board - Google Patents

Description

  The present invention relates to a circuit component mounting structure for mounting a power supply device such as a DC / DC converter, in which a large current flows in a power line, and other circuit components on a substrate, and the mounting substrate.

  In supplying electric power from a fuel cell to a load, there is a technique of adjusting a voltage by a power supply device such as a DC / DC converter (see, for example, Patent Document 1). Such a circuit board for mounting circuit components of a DC / DC converter is obtained by arranging a copper foil wiring having a thickness of 35 μm on an insulating resin substrate.

  FIG. 5 shows a circuit of a full bridge type DC / DC converter, and FIG. 6 schematically shows a mounting state of circuit components constituting the DC / DC converter on a mounting board.

  In FIG. 5, the DC / DC converter is an insulating type, and a smoothing capacitor circuit unit 1 including a plurality of smoothing capacitors C1 to C6 connected in parallel to the fuel cell, and the smoothing capacitor circuit unit 1 performs smoothing. A full-bridge circuit unit 2 that converts the converted fuel cell DC output into a pulse voltage by switching operation of the eight FETs Q1-Q8, and a current resonance capacitor circuit unit 3 that includes three current resonance capacitors C7-C9; And a power conversion transformer 4 including a primary coil T11 and a secondary coil T12. A rectifying / smoothing circuit (not shown) is connected to the secondary coil T12 of the power conversion transformer 4.

  In the above circuit, L1 to L5 are power lines, and a thick solid line indicates a power line portion constituted by the bus bars B11 to B16 on the mounting board PB.

  Referring to FIG. 6, in this mounting substrate PB, the thick solid line indicates bus bars B11 to B16 that are conductors having a rectangular solid cross section. Of the smoothing capacitors C1 to C6 constituting the smoothing capacitor circuit unit 1, smoothing capacitors C2, C4, and C6 are interposed in the facing gap between the first and second bus bars B11 and B12. Eight MOSFETs Q1-Q8 of the full bridge circuit unit 2 are interposed between the third, fourth, and fifth bus bars B13, B14, and B15. The illustration of the heat sink is omitted. The common connection portion A of the MOSFETs Q5 and Q6 in FIG. 5 is connected by the wiring W1 in FIG. 6, and one end side B of the primary side coil T11 of the power conversion transformer T1 is connected by the wiring W2, and the primary side coil T11 The other end C is connected to the bus bar B15 via the wiring W3. These wirings can be constituted by a conductive wiring pattern formed by etching the mounting substrate PB or can be constituted by aerial wiring.

JP 2000-36308 A

  In the case of the mounting board PB having the above structure, the power conversion efficiency of the DC / DC converter mounted on the board surface is not good. Therefore, the present inventors repeatedly experimented with various changes in the mounting state of the circuit components on the mounting board PB in order to improve the power conversion efficiency and repeated experiments. Depending on the mounting state, the AC resistance It has been found that this increase in power consumption may have been a decrease in power conversion efficiency.

  The cause of the increase in the AC resistance has been further studied. One of the causes is, for example, from the fuel cell, a large current is generated between the bus bars B13 and B14 constituting the pair of positive and negative power lines L1 and L2. However, there is a loop between the bus bars B13 and B14, and, in addition, circuit components of the power supply device are interposed in the loop, and other than these circuit components are mounted. It was possible to conclude that the conductor such as the copper foil wiring pattern of the substrate PB occupies a relatively large area.

  Therefore, the present invention provides a circuit component mounting structure that can improve the circuit operation efficiency of a circuit component, for example, a power conversion device such as a DC / DC converter, based on the above conclusion. This is a problem to be solved.

  A circuit component mounting structure according to the present invention is a structure in which at least a part of a circuit component is mounted on a substrate using a bus bar as a conductive path, and at least a pair of power lines on the substrate is opposed to at least a pair thereof. It is constituted by a bus bar, and the at least one pair of bus bars are set to face each other while being electrically insulated from each other, and the circuit component is arranged outside at least between the opposite sides of the pair of bus bars. .

  It is preferable that the pair of bus bars are opposed to each other with a space that is small enough to reduce the number of conductors interposed therebetween. The pair of bus bars can be opposed to each other with an electrical insulating material interposed therebetween. The pair of bus bars is preferably a bus bar that has a difference in height between positive and negative voltages. The bus bar is preferably made of a low-resistance material having conductivity. For the bus bar, for example, copper, silver, gold, platinum, aluminum, tin, lead, nickel, and alloys thereof are preferably used. The shape of the bus bar is preferably a conductor having a rectangular solid cross section, but is not limited thereto. It is preferable that no circuit parts be interposed between the pair of bus bars as much as possible. It is preferable that the facing interval between the pair of bus bars is such that a circuit component or a conductor cannot be interposed, or a region where the intervening region can be as small as possible is narrow. An example of the conductive wiring pattern is a pattern formed by etching a copper foil on a mounting board.

  The circuit component is preferably a circuit component of a power supply device such as a DC / DC converter that processes an input voltage by a switching element, but is not necessarily limited thereto. The input voltage is preferably an input voltage from a fuel cell, but is not necessarily limited thereto. The said conductor contains the copper foil wiring pattern of a mounting board, etc.

  A mounting board according to the present invention includes the circuit component mounting structure described above.

  According to the circuit component mounting structure of the present invention, on the substrate, when at least a pair of opposing power lines having a difference in voltage is configured with a pair of opposing bus bars, the pair of bus bars are not looped. The opposing gap between the pair of bus bars facing each other is narrowed so that the area where circuit components, conductors, etc. can exist in the gap is set as narrow as possible, and the circuit components are arranged outside the opposing gaps of these bus bars. Since it is a possible structure, for example, when a power supply device is arranged on a mounting substrate, an increase in AC resistance in the power supply device can be suppressed, and the power conversion efficiency of the power supply device can be improved.

FIG. 1 is a circuit diagram of a DC / DC converter according to an embodiment of the present invention, in which a power line composed of bus bars is indicated by a thick solid line on a mounting board. FIG. 2 is a plan view showing a mounting state on the circuit board surface of the circuit component mounting board of the DC / DC converter of FIG. FIG. 3 is an oblique view of the mounting state. FIG. 4 shows an example in which the embodiment of the present invention is applied to another general circuit. FIG. 5 is a circuit diagram of a DC / DC converter according to a conventional example, in which a power line composed of bus bars is indicated by a thick solid line on a mounting board. FIG. 6 is a plan view showing a mounting state of the DC / DC converter circuit component mounting board of FIG. 5 on the board surface.

  Hereinafter, a circuit component mounting structure for a power supply device according to an embodiment of the present invention will be described with reference to FIGS. This power supply device is applied to a DC / DC converter. FIG. 1 is a circuit diagram of a DC / DC converter, which is the same circuit as FIG. 4. In FIG. 1, among the power lines of the DC / DC converter, a power line composed of bus bars is indicated by a thick solid line. . FIG. 2 is a plan view of the circuit component mounting board of the DC / DC converter of FIG. 1, and FIG. 3 is a view of the mounting board in a state where the circuit components are mounted as viewed from an oblique direction.

  First, referring to FIG. 1, between the pair of first and second power lines L1 and L2, six smoothing capacitors C1 to C6 constituting the smoothing capacitor circuit unit 1 are connected in parallel. Similarly, between the pair of first and second power lines L1, L2, eight MOSFETs Q1-Q8 constituting the full bridge circuit unit 2 are connected. Specifically, the parallel connection set of MOSFETs Q1 and Q2 and the parallel connection set of MOSFETs Q3 and Q4 are connected in series, and the parallel connection set of MOSFETs Q5 and Q6 and the parallel connection set of MOSFETs Q7 and Q8 are set in series, respectively. The first and second power lines L1 and L2 are connected to each other.

  Between the third and fifth power lines L3 and L5, three current resonance capacitors C7 to C9 constituting the current resonance capacitor circuit unit 3 are connected in parallel. A primary coil T11 of the power conversion transformer T1 is connected between the fourth and fifth power lines L4 and L5.

  The configuration on the mounting substrate PB will be described with reference to FIGS. On the mounting substrate PB, the first and second power lines L1 and L2 are in a state of being rectangular in cross section, standing in a state of being electrically insulated from each other in the vertical direction on the mounting substrate PB, that is, at a predetermined interval. The first and second bus bars B1 and B2 are thin. The standing height of the first and second bus bars B1 and B2 from the board surface of the mounting board PB is substantially equal to the arrangement height of the smoothing capacitors C1 to C6 from the board surface. The first power line L1 has a higher voltage than the second power line L2, and the first bus bar B1 can be referred to as a high voltage bus bar, and the second bus bar B2 can be referred to as a low voltage bus bar. The first and second bus bars B1 and B2 are bus bars each having an L shape in plan view with the short portions B1a and B2a and the long portions B1b and B2b, and the short portions B1a and B2a are not shown. A positive terminal and a negative terminal of the fuel cell are connected to each other, and their longitudinal portions B1b and B2b face each other in parallel with a narrow space or gap as a space for maintaining insulation. The distance between the opposing gaps is determined by the applied potential difference with respect to the first and second bus bars B1 and B2. If the potential difference is small, the opposing gap can be made narrower accordingly. Also, three smoothing capacitors C1, C3, C5 and MOSFET Q1 are provided outside the gaps between the longitudinal portions B1b, B2b of the first and second bus bars B1, B2 and outside the gaps between the longitudinal portions B1b, B2b. , Q2, Q5, Q6, and three smoothing capacitors C2, C4, C6 and MOSFETs Q3, Q4, Q7, Q8 are arranged side by side on the other side outside the gap. Therefore, no conductor exists between the first and second bus bars B1 and B2. In addition, if an insulator is interposed in the opposing gap between the longitudinal portions B1b and B2b of the first and second bus bars B1 and B2, it is not necessary to interpose a space in the opposing gap between the longitudinal portions B1b and B2b. MOSFETs Q1, Q2, Q5, and Q6 are attached to the heat sink HS1, and MOSFETs Q3, Q4, Q7, and Q8 are attached to the heat sink HS2.

  The third power line L3 includes a third bus bar B3 having a rectangular cross section and a thin wall thickness. The third bus bar B3 is a bus bar in which a pair of parallel portions B3a and B3b are T-shaped in plan view, and the fourth power line L4 is configured by a fourth bus bar B4 having a rectangular cross section and a thin wall thickness. The fourth bus bar B4 is a bus bar that is L-shaped in plan view with a short portion B4a and a long portion B4b. The fifth power line L5 includes a fifth bus bar B5 having a rectangular cross section and a thin wall thickness. The fifth bus bar B5 is a bus bar that is L-shaped in plan view with a short portion B5a and a long portion B5b. The height of each of the bus bars B3-B5 from the board surface of the mounting board PB is the mounting height of each of the MOSFETs Q1-Q8 from the mounting board PB, and the mounting height of the current resonance capacitors C7-C9 from the mounting board PB. In the embodiment, the circuit components have substantially the same height as the first and second bus bars B1 and B2, but the present invention is limited to these height relationships. It is not a thing.

  The long portion B3a of the third bus bar B3 is disposed opposite to the short portion B4a in a state of being electrically insulated from each other with a narrow gap parallel to the long portion B2b of the second bus bar B2. One end side of the primary coil T11 of the power conversion transformer T1 is connected. One parallel portion B3a of the third bus bar B3 is disposed opposite to the longitudinal portion B1b of the first bus bar B1 with a narrow gap therebetween and in an electrically insulated state from each other, and the other orthogonal portion B3b is The fifth bus bar B5 is disposed in parallel with the longitudinal portion B5b of the fifth bus bar B5, and three current resonance capacitors C7 to C9 are juxtaposed therebetween.

  In the above configuration, in the present embodiment, on the mounting substrate PB, for example, the gap between the first and second bus bars B1 and B2 is set narrow, so that the circuit component is included. Since there is no conductor including a wiring pattern such as a copper foil of the mounting board PB or the area where it is present is narrow, an increase in AC resistance is greatly suppressed, resulting in improved power conversion efficiency. It was.

  More specifically, according to a study by the present inventors, a pair of bus bars are in a loop shape, and when current flows in a loop shape in these bus bars, a magnetic field is generated around the bus bars. If circuit parts, conductors, and the like are interposed between a pair of bus bars facing each other, these act as an AC resistance increasing factor, thereby reducing the power conversion efficiency.

  On the other hand, in this embodiment, a pair of bus bars are in a loop shape, and current flows in the bus bars in a loop shape to generate a magnetic field around the bus bars. The interval is extremely small, and there are no circuit parts or conductors between the facing parts, or the amount of intervention is negligible, reducing the above-mentioned conventional factors of increasing AC resistance, thereby reducing the power conversion efficiency. Is thought to improve.

  In the embodiment, the power supply device is used. However, an example applied to another general circuit will be described with reference to FIG. 4. FIG. 4A shows elements such as capacitors EX and EY between the power lines LX and LY. Is connected. 4 (b) shows an equivalent circuit of FIG. 4 (a), which is an electrically similar circuit to FIG. 4 (a), but capacitors EX and EY are provided between the power lines LX and LY in the drawing. It is not done. In FIG. 4C, bus bars BX and BY corresponding to the power lines LX and LY are erected on the mounting substrate PB, and capacitors EX and EY are respectively provided on one side and the other side between the opposite sides of the bus bars BX and BY. Are arranged and electrically connected to the bus bars BX and BY as indicated by dotted lines. In FIG. 4D, capacitors EX and EY are arranged only on one side outside between the opposing bus bars BX and BY, and are electrically connected to the bus bars BX and BY, respectively, as indicated by dotted lines. . In the above configuration, the distance d between the bus bars BX and BY is made as narrow as possible. When the facing distance d is narrowed, it becomes difficult for a conductor to intervene between the facing bus bars BX and BY, and the power conversion efficiency can be further increased. The height H1 from the substrate surface of the bus bars BX and BY and the height H2 from the substrate surface of the capacitors EX and EY may be arbitrary height relationships, and one of them is not necessarily high. Absent. In addition, it is preferable that a conductor such as a copper foil wiring pattern of the mounting board PB is not interposed between the bus bars BX and BY, if possible.

DESCRIPTION OF SYMBOLS 1 Smoothing capacitor circuit part 2 Full bridge circuit part 3 Current resonance capacitor circuit part 4 Power conversion transformer part L1-L5 Power line B1-B5 Bus bar

Claims (4)

A structure in which at least a part of a circuit component is mounted on a substrate as a bus bar as a conductive path,
At least a pair of power lines is constituted by at least a pair of bus bars facing the whole or a part on the substrate,
The at least one pair of bus bars are set to face each other while being electrically insulated from each other so as to suppress an increase in AC resistance as compared with the case where circuit components are arranged between the at least one pair of bus bars . The circuit component is disposed on the substrate outside between at least a pair of the bus bars; and
The at least one pair of bus bars is made of a conductor having a rectangular solid cross section, and is erected on the substrate.
A circuit component mounting structure characterized by that.   The structure according to claim 1, wherein the pair of bus bars is constituted by bus bars having a high and low voltage difference from each other.   The structure according to claim 1, wherein the circuit component is a circuit component for a power supply device that processes an input voltage by a switching element.   A mounting board comprising the circuit component mounting structure according to any one of claims 1 to 3.

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