JP4300717B2 - DC-DC converter and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC-DC converter and a manufacturing method thereof.
[0002]
[Prior art]
In an electric vehicle including a hybrid vehicle, a dual power supply system in which power is supplied to a traveling motor from a high-voltage main battery and power is supplied to various auxiliary machines from a low-voltage auxiliary battery is advantageous in various respects. Even in a normal internal combustion locomotive, there is a tendency to mount a two-battery power supply system in which both a high-voltage main battery and a low-voltage load power supply auxiliary battery are mounted due to various factors. In this dual power supply type vehicle power supply system, it is a reasonable choice in various ways to reduce the capacity of the auxiliary battery and transmit power from the main battery to the auxiliary battery through the step-down DC-DC converter device.
[0003]
This step-down DC-DC converter device includes an inverter that forms a single-phase AC voltage from an input DC voltage, a transformer that steps down the single-phase AC voltage, a rectifier that rectifies the output voltage of the transformer, and smoothes the rectified voltage. The choke coil and the smoothing circuit are generally composed of a smoothing capacitor. However, the secondary coil of the step-down transformer is usually provided with an intermediate terminal, and the rectification unit is usually constructed by a single-phase full-wave rectification method.
[0004]
The DC-DC converter needs to have a large output current in order to cover at least all of the low-voltage load supply power of the vehicle. Therefore, each coil of the transformer and the choke coil and the wiring portion connected to each of these coils are bus bars, It is composed of a long plate-like conductor piece.
[0005]
The specific structure of the high-power DC-DC converter is usually as follows.
[0006]
First, the semiconductor elements, rectifiers, transformers, and choke coil cores that constitute the switching elements of the inverter are in good contact with the surface of the metal heat dissipation plate for heat dissipation. A controller for control and other small current circuit elements are mounted on a printed board fixed to a heat radiating plate. Transformers and choke coils are formed by bending the bus bar into a ring shape, and the bus bar coil is resin-molded for electrical insulation between the turns of each coil and external insulation. Do. The bus bar connecting the main electrodes of each coil, rectifier and switching element is wired so as not to touch the printed circuit board and the controller and other small current circuit elements on the printed circuit board, and connected to the terminals of the coil, switching element and rectifier.
[0007]
An example of a conventional DC-DC converter is shown in FIG. However, the bus bar is not shown.
[0008]
[Problems to be solved by the invention]
However, the above-described large current DC-DC converter has a problem that the manufacturing process is complicated and the operation is not easy.
[0009]
In addition, the bus bar temperature increases due to its own heat generation and heat received from the connected coil or semiconductor element. However, in the sealed circuit case, the heat dissipation of the bus bar to the air is small, and the bus bar temperature The rise caused a problem that other circuit elements were adversely affected.
[0010]
The present invention has been made in view of the above problems, and an object thereof is to provide a DC-DC converter that is easy to manufacture and excellent in heat dissipation and a manufacturing method thereof.
[0011]
[Means for Solving the Problems]
The DC-DC converter according to claim 1 has a metal plate-like heat dissipation plate, an inverter having a plurality of switching elements for converting input DC power into AC power, a primary coil and a secondary coil wound around a core. A transformer for converting the voltage of the AC power,
A rectifier that rectifies the output power of the transformer, a choke coil that has a coil wound around a core and smoothes the output power of the rectifier, a control unit that controls the switching element, a pair of output terminals of the inverter, and the In a DC-DC converter including a primary side bus bar for individually connecting both ends of a primary coil, and a secondary side bus bar for connecting the secondary coil and the rectifier or the choke coil,
A resin plate made of a resin molded product surrounding most of each of the coils and the both bus bars, and the bottom surface of the resin plate is fixed to the heat dissipation plate in close contact with the surface of the heat dissipation plate; Is characterized in that the heat of each coil and both bus bars is radiated to the heat radiating plate by solid heat transfer .
[0012]
That is, in this configuration, most parts of the bus bar as a large current wiring member of the DC-DC converter and the bus bar coil of the transformer and choke coil are surrounded by a resin plate which is a resin molded product made of a resin molded product. It is characterized in that each coil and each bus bar are integrated into a bus bar subassembly by covering.
[0013]
With the above configuration, the mutual positional relationship between each bus bar and each coil is determined in advance, so that the installation work at a predetermined site and the interconnection work between them become simple, and their connection parts are loosened due to vibration or the like. It is also easy to electrically insulate them from other circuit components. Further, since the bus bar is in close contact with the heat radiating plate through the resin plate, the bus bar can be radiated to the heat radiating plate by solid heat transfer, and the cooling property of the bus bar can be improved.
[0014]
According to a second aspect of the present invention, in the DC-DC converter according to the first aspect, each turn of each coil is formed by a bare bus bar, and the resin plate functions as an electrical insulating material between the turns. It is characterized by that.
[0015]
That is, according to this configuration, the primary coil, the secondary coil, and the choke coil of the transformer are surrounded by the same resin plate by resin insert molding, and their mutual arrangement is determined.
[0016]
In this way, the adjacent turns of each coil can be electrically insulated well and the mutual positional relationship between the coil of the transformer and the coil of the choke coil can be set precisely. And installation work becomes very easy. Further, by fixing the resin plate to the heat radiating plate, the core of the transformer and the core of the choke coil can be satisfactorily adhered and fixed to the heat radiating plate.
[0017]
According to a third aspect of the present invention, in the DC-DC converter according to the first aspect, since the bus bar is formed of the same conductor piece as the coil, the number of parts and the number of connection steps can be reduced.
[0018]
According to a fourth aspect of the present invention, in the DC-DC converter according to any one of the first to third aspects, the core further includes a base portion whose bottom surface is in close contact with the surface of the heat radiating plate, and a core through the resin plate from the base portion Since it consists of a lower core part having a plurality of pillars protruding through the hole and an upper core part that is in contact with the top surface of each pillar part and constitutes a closed magnetic circuit together with the lower core part, By simply inserting the column of the core through the core through-hole of the resin plate and fixing the resin plate to the heat radiating plate, the fixing of the core and the close contact with the heat radiating plate can be satisfactorily realized.
[0019]
According to a fifth aspect of the present invention, in the DC-DC converter according to the fourth aspect, the resin plate is integrated with a thin plate-like circuit mounting board portion on which the control portion and the small current circuit component are mounted on the upper surface. Since it is supported so as to be separable, the support structure of the circuit mounting board portion is simplified, and the alignment and connection work between the bus bar and the wiring of the circuit mounting board portion is facilitated. Conventionally, a printed board, that is, a circuit mounting board portion and a bus bar are supported on a case so as to be electrically insulated. Further, if a conductive foil is attached to the surface of the resin plate, the resin plate itself can also serve as the circuit mounting board portion, and the overall structure and mounting work can be further simplified.
[0020]
According to a sixth aspect of the present invention, in the DC-DC converter according to the fifth aspect, the upper surface of the circuit mounting board portion is formed flat with respect to the upper surface of the other portion of the resin plate. Circuit elements can be easily mounted on the top surface of the resin plate.
[0021]
According to a seventh aspect of the present invention, in the method for manufacturing a DC-DC converter according to any one of the first to sixth aspects, the coils, the choke coil, and the bus bars are insert-molded and embedded in the resin plate. Therefore, the manufacturing process can be simplified.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of a step-down DC-DC converter device for a two-battery mounted vehicle using the DC-DC converter of the present invention will be described with reference to the following examples.
[0023]
[Example 1]
The step-down DC-DC converter device of this embodiment will be described below with reference to the circuit diagram shown in FIG.
(Circuit configuration)
1 is a DC-DC converter, V1 is a high voltage battery, and V2 is a low voltage battery.
[0024]
In the DC-DC converter 1, 2 is an inverter, 3 is a transformer, 41 and 42 are a pair of diodes (rectifiers) forming a rectifier, 5 is a smoothing choke coil, 6 is a smoothing capacitor, and 7 is a controller.
[0025]
The transformer 3 has a ferrite core 30, a primary coil 31, a first secondary coil 32, and a second secondary coil 33. One end of the secondary coils 32 and 33 is grounded, and the other end is connected to the choke coil 5 through the diodes 41 and 42.
[0026]
The high-voltage AC voltage output from the inverter 2 is stepped down by the transformer 3. The secondary coils 32 and 33 alternately output half-wave rectified voltages to the low-voltage battery V <b> 2 through the diodes 41 and 42 and the choke coil 5 every different half-wave periods. The controller 7 compares the voltage of the low-voltage battery V2 with a reference voltage, and based on the comparison result, increases or decreases the PWM duty ratio of the four switching elements (MOSFETs or IGBTs) 21 to 24 of the inverter 2, and sends the AC power Feedback control. Since this type of DC-DC converter is well known, further explanation is omitted, and the features of this embodiment will be described below.
[0027]
The coils 31 to 33 of the transformer 3 and the coil 52 of the choke coil 5 are configured by winding a bus bar. The choke coil 5 is configured by winding a coil 52 around a ferrite core 51.
[0028]
81 is a primary side bus bar, and 82 is a secondary side bus bar. The primary bus bar 81 includes bus bars 811 to 814. The bus bar 811 connects one end of the primary coil 31 and the bus bar 813, the bus bar 813 is connected to the connection point (AC output terminal) of the pair of switching elements 23 and 24, and the bus bar 812 is connected to the other end of the primary coil 31 and the bus bar 813. The bus bar 814 is connected to the connection point (AC output terminal) of the pair of switching elements 21 and 22. The bus bars 811 and 812 are configured by extending the primary coil 31.
[0029]
The secondary bus bar 82 includes bus bars 821 to 826. The bus bar 821 connects one end of the secondary coil 32 and the anode of the diode 41, and the bus bar 822 connects one end of the secondary coil 33 and the anode of the diode 42. The bus bar 823 is connected to the base plate 51. The other ends of the bus bars 824 and 825 having one end connected to the cathodes of the diodes 41 and 42 are connected to a bus bar 824 formed by extending the coil 52 of the choke coil 5.
[0030]
Reference numeral 8 denotes a resin plate that surrounds and fixes each of the bus bars and the coils 31 to 33 and 52 described above.
[0031]
The resin plate 8 has openings (holes) 81 to 84. The hole 81 is a hole through which the core 32 of the transformer 3 passes, the diodes 41 and 42 are disposed in the holes 82 and 83, and the hole 84 is a hole through which the core 51 of the choke coil 5 passes.
[0032]
Therefore, the coils 31 to 33 and 52 formed by winding the bus bar and the bus bars 811 to 814 and 821 to 826 together with the resin plate 8 which surrounds most of them constitute a part named one bus bar subassembly. ing.
[0033]
Both ends of the bus bar 814 protrude from the resin plate 8 and are connected to the main electrodes of the switching elements 21 and 22. A front end portion of the bus bar 823 protrudes from the resin plate 8 and is connected to a heat radiating plate 9 made of an aluminum plate, which will be described later. A bus bar 827 formed by extending one end of the coil 52 protrudes from the resin plate 8 and is connected to the smoothing capacitor 6.
[0034]
Ends on the output side of the bus bars 821 and 822 protrude into the holes 82 and 83 and are connected to the anodes of the diodes 41 and 42. One end portions of the bus bars 824 and 825 protrude into the holes 82 and 83 and are connected to the cathodes of the diodes 41 and 42.
[0035]
A longitudinal section of this DC-DC converter is shown in FIG.
[0036]
The lower surface of the resin plate 8 is in close contact with the upper surface of the heat radiating plate 9 made of aluminum. Each bus bar is disposed as close to the lower surface of the resin plate 8 as possible inside the resin plate 8 so as to improve heat dissipation from each bus bar to the heat radiating plate 9.
[0037]
As shown in FIG. 2, the core 30 of the transformer 3 is formed by bonding a lower core portion 301 having an E-shaped cross section and an upper core portion 302. The lower core portion 301 includes a bottom plate portion that is seated in a shallow concave portion of the heat radiating plate 9 and three support column portions that protrude upward from the bottom plate portion. A primary coil 31 and two secondary coils 32 and 33 formed by winding a bus bar are wound around the central support column. Note that the turns of the primary coil 31 and the two secondary coils 32 and 33 are arranged at a predetermined interval from each other, and the resin of the resin plate 8 is filled between the turns. Illustration is omitted.
[0038]
FIG. 3 shows the vicinity of the coil 31 to 33 built-in portion of the transformer 3 of the resin plate 8. 81a, 81b, and 81c are holes through which the above-mentioned three support portions of the E-shaped lower core portion 301 penetrate vertically, and these holes 81a, 81b, and 81c constitute the core through-hole 81 shown in FIG. ing.
[0039]
As shown in FIG. 2, the core 51 of the choke coil 5 is also formed by bonding a lower core 511 having an E-shaped cross section and an upper core portion 512. The lower core portion 511 includes a bottom plate portion that is seated in a shallow concave portion of the heat radiating plate 9 and three support column portions that protrude upward from the bottom plate portion. A coil 52 formed by winding a bus bar is wound around the center column. Like the transformer 3, the turns of the coil 52 are arranged at a predetermined interval from each other, and the resin of the resin plate 8 is filled between the turns, but detailed illustration thereof is omitted in FIG. FIG. 4 shows the vicinity of the choke coil 5 built-in portion of the resin plate 8.
[0040]
Although not shown in FIGS. 1 and 2, a printed circuit board is disposed above the heat radiating plate 9 other than the resin plate 8, and an IC and other small circuit components forming the control unit 7 are mounted on the printed circuit board. Has been.
[0041]
(Modification)
The variant shown in FIG. In this embodiment, in FIG. 1, the diodes 41 and 42 are arranged in the opposite direction of energization. The resin plate 8 surrounds the coils 31 to 33, the coil 52 and each bus bar, and the bottom surface of the resin plate 8 is The point of being in close contact with the upper surface of the heat radiating plate 9 is the same as in the first embodiment. According to this aspect, the structure of the secondary bus bar can be simplified.
[0042]
The bus bar subassembly including the resin plate 8 is formed by resin insert molding and fastened to the heat radiating plate 9 with screws.
[0043]
[Example 2]
A second embodiment will be described below with reference to FIG. FIG. 6 is a longitudinal sectional view showing the vicinity of the choke coil of the resin plate 8.
[0044]
The feature of this embodiment is that the resin plate 8 described in the first embodiment has a thin wiring board portion 8b parallel to the upper surface of the heat radiating plate 9 from the side edge of the thick main portion 8a surrounding the bus bar and the coil. It is in. That is, in this embodiment, the resin plate 8 also serves as a conventional printed board.
[0045]
In the wiring board portion 8b, lead holes for inserting the lead terminals of the circuit components 10 and 11 are formed during insert molding, and the lead terminals of the circuit components 10 and 11 are inserted and soldered.
[0046]
An integrated conductor pattern obtained by patterning a copper foil is attached to the upper surface or the lower surface of the wiring substrate portion 8b. After the attachment, a connecting portion of the conductor pattern is cut out by punching together with the wiring substrate portion 8b. A necessary number of conductor patterns are arranged in a necessary shape.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a step-down DC-DC converter device for a vehicle according to a first embodiment.
FIG. 2 is a longitudinal sectional view of FIG.
FIG. 3 is a partial plan view of FIG. 2;
4 is a longitudinal sectional view of FIG. 1. FIG.
FIG. 5 is a circuit diagram showing a modification of FIG. 1;
6 is a longitudinal sectional view showing Example 2. FIG.
FIG. 7 is a schematic perspective view showing a conventional DC-DC converter.
[Explanation of symbols]
2 Inverter 3 Transformer 41, 42 Diode (rectifier)
5 Choke coil

Claims (7)

Metal plate-like heat dissipation plate,
An inverter having a plurality of switching elements that convert input DC power into AC power;
A transformer having a primary coil and a secondary coil wound around a core to convert the voltage of the AC power;
A rectifier for rectifying the output power of the transformer;
A choke coil having a coil wound around a core to smooth the output power of the rectifier;
A control unit for controlling the switching element;
A primary bus bar for individually connecting a pair of output terminals of the inverter and both ends of the primary coil; and
A secondary bus bar connecting the secondary coil and the rectifier or the choke coil;
In a DC-DC converter comprising:
A resin plate made of a resin molded product surrounding most of each of the coils and the bus bars,
The bottom surface of the resin plate is fixed to the heat radiating plate in close contact with the surface of the heat radiating plate. DC-DC converter characterized. The DC-DC converter according to claim 1, wherein
Each turn of each coil is formed of a bare bus bar, and the resin plate functions as an electrical insulating material between the turns. The DC-DC converter according to claim 1, wherein
The bus bar is formed of the same conductor piece as the coil, and is a DC-DC converter. The DC-DC converter according to any one of claims 1 to 3,
The core is
A lower core portion having a base portion whose bottom surface is in close contact with the surface of the heat dissipating plate, and a plurality of pillar portions protruding from the base portion through the core through hole of the resin plate;
An upper core part that constitutes a closed magnetic circuit together with the lower core part in contact with the top surface of each column part;
A DC-DC converter characterized by comprising: The DC-DC converter according to claim 4, wherein
2. The DC-DC converter according to claim 1, wherein the resin plate supports a thin plate-like circuit mounting board portion on which the control unit and the small current circuit component are mounted on an upper surface thereof in an integrated or separable manner. The DC-DC converter according to claim 5, wherein
The DC-DC converter according to claim 1, wherein the upper surface of the circuit mounting board portion is formed flat with respect to the upper surface of the other part of the resin plate. In the manufacturing method of the DC-DC converter in any one of Claims 1 thru | or 6,
The method of manufacturing a DC-DC converter, wherein the two coils, the choke coil, and the two bus bars are insert-molded and embedded in the resin plate.

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