JP2014093926A - Switching power-supply device - Google Patents

Abstract

A printed circuit board on which a switching element for secondary side synchronous rectification of an insulated DC / DC converter circuit is mounted realizes a configuration in which a heat problem due to a large current flows hardly occurs and is highly efficient. It is an object of the present invention to provide a small switching power supply device with good assembly.
Secondary coil conductors 122 and 123 of a transformer 120 are arranged so as to sandwich a primary coil conductor 121, and ends 122a, 122b, 123a and 123b of the secondary coil conductors 122 and 123 are It is electrically connected to the drain terminals D of the secondary side switching elements 131 to 134 via connection wiring patterns 421 to 424 on the printed circuit board 410.
[Selection] Figure 2

Description

  The present invention relates to a switching power supply device having an insulating structure having a transformer.

  As an in-vehicle insulated switching power supply device mounted on an electric vehicle or a hybrid car, for example, an insulated DC / DC converter device for converting a DC voltage level is known. This device performs an operation of stepping down a high voltage supplied from a driving battery represented by a lithium ion battery to a low voltage that is a power supply voltage of an auxiliary electrical component while maintaining insulation.

  In such an insulated DC / DC converter device, a synchronous rectification method using a semiconductor switching element typified by a MOSFET as a secondary rectifying element is generally employed. Since the rectification method is a synchronous rectification method, the efficiency in a high load region is generally improved as compared with the case where a diode is used as a rectification element. Therefore, it is effective in an insulation type DC / DC converter device having a larger output current. It is. Further, by mounting the MOSFET on the metal substrate, the heat generation of the MOSFET due to the large current flowing on the secondary side can be efficiently radiated to some extent.

  As an example of an insulation type switching power supply device that employs a synchronous rectification method, for example, in the insulation type DC-DC converter disclosed in Patent Document 1, the transformer 30 is secondary-wound at a certain height H1 from the bottom surface of the housing 35. The first connection terminal 36 for one end of the line, the second connection terminal 37 for the other end, and the third connection terminal 38 for the intermediate tap are connected between the connection terminal 36 and the connection terminal 37 in the horizontal direction. The terminals 38 are arranged with the terminal 38 interposed therebetween. The choke coil 40 is disposed above the substrate 70, and a connection terminal 42 extending toward the connection terminal 38 from the housing 35 of the transformer 30 is connected to the connection terminal 38. A conductive layer 73 for drain of the substrate 70 is extended in the protruding direction of the first connection terminal 36 from the casing 35 of the transformer 30 in plan view, and a conductive layer 74 for drain is extended in the casing of the transformer 30 in plan view. The second connection terminal 37 extends from the body 35 in the protruding direction. In this insulated DC-DC converter, rectifying MOSFETs 21 to 24 are mounted on a substrate 70 (configured by an electrically insulating layer 72 and conductive layers 73 to 77 on the upper surface of a metal plate 71), and via a bus bar, The secondary winding of the transformer 30 is connected to the substrate 70 to reduce noise.

JP 2011-50160 A

However, in the conventional insulated DC-DC converter shown in Patent Document 1, the MOSFET is mounted on the metal substrate, but it is difficult to configure a control circuit for generating a control signal for the MOSFET on the metal substrate. It is necessary to mount the control circuit on another printed circuit board. For this reason, an extra connector and harness for connecting the control circuit and the MOSFET on the metal substrate are required, which increases costs and decreases vibration resistance. Moreover, since it is a structure that radiates heat through a metal substrate, heat dissipation is inferior compared to a structure that is cooled by being in close contact with the housing via an insulating heat radiating sheet or the like, and the performance of the MOSFET cannot be fully exhibited. There was a problem. In addition, it is necessary to mount an extra connection terminal for the connection between the secondary winding of the transformer and the MOSFET, resulting in an increase in the number of parts, an increase in cost, and a reduction in assembly.

  On the other hand, when a MOSFET is mounted on a printed circuit board, the control signal of the MOSFET can be easily wired using a pattern on the printed circuit board, which causes an increase in cost and a decrease in vibration resistance. Few. In addition, by mounting a MOSFET of a lead type package, the structure can be cooled by being in close contact with the casing via the above-described insulating heat dissipation sheet or the like, and heat dissipation can be improved. However, when a MOSFET is mounted on a printed circuit board, it is necessary to pass a large secondary current through the pattern on the printed circuit board, which may lead to deterioration of the circuit board or burnout due to self-heating of the pattern.

  The present invention has been made to solve the above-described problems, and is because a large current flows in a printed circuit board on which a secondary side synchronous rectification switching element of an insulated DC / DC converter circuit is mounted. An object of the present invention is to provide a small-sized switching power supply device that realizes a configuration that is less likely to cause heat problems, and that has high efficiency and good assemblability.

  In order to solve the above problems, a switching power supply device according to the present invention includes an inverter circuit that converts DC power into AC power, a primary coil conductor, and at least one plate-like secondary coil conductor. And a transformer connected to the output side of the inverter circuit, a rectifier circuit connected to the output side of the transformer, and a printed circuit board on which the inverter circuit and the rectifier circuit are mounted. A wiring pattern for connection for connecting an end of the secondary coil conductor and a terminal of the switching element, a housing for accommodating the transformer and the printed board, and formed on the printed board; A through-hole in which the end of the secondary coil conductor and the terminal of the switching element are provided in the connection wiring pattern It is inserted, and is characterized in that it is implemented by soldering.

  According to the switching power supply device of the present invention, an additional member is used by directly mounting the secondary side coil conductor constituting the low voltage side winding of the transformer on the printed circuit board on which the secondary side switching element is mounted. The transformer and the secondary side rectifier circuit can be electrically connected to each other, reducing the number of components and improving the assemblability, and reducing the distance of current flow on the printed circuit board. It is possible to suppress the heat generation and to improve the reliability of the printed circuit board.

1 is a configuration diagram of a first DC / DC converter circuit applied to a switching power supply device according to Embodiment 1. FIG. FIG. 3 is a top view illustrating a first configuration example of a structure of a connection portion between a transformer and a rectifier circuit included in the DC / DC converter of the switching power supply device according to the first embodiment. It is a figure which shows the cross section of the A-A 'part of FIG. It is a figure which shows the cross section of the B-B 'part of FIG. FIG. 3 is a configuration diagram of a second DC / DC converter circuit applied to the switching power supply device according to the first embodiment. FIG. 6 is a top view showing a second configuration example of a structure of a connection portion between a transformer and a rectifier circuit constituting the DC / DC converter of the switching power supply device according to the first embodiment. FIG. 3 is a configuration diagram of a third DC / DC converter circuit applied to the switching power supply device according to the first embodiment. It is a top view which shows the other structural example of the structure of the connection part of a transformer and a rectifier circuit.

  Hereinafter, a switching power supply device according to an embodiment of the present invention will be described with reference to FIGS.

Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram of a first DC / DC converter applied to the switching power supply device according to the first embodiment, and FIG. 2 shows the DC / DC converter of the switching power supply device according to the first embodiment. It is a top view which shows the 1st structural example of the structure of the connection part of the trans | transformer and rectifier circuit to comprise. 3 and 4 are diagrams showing a cross section taken along line AA ′ and a cross section taken along line BB ′ in FIG. 2, respectively.

  First, the circuit configuration of a first DC / DC converter applied to the switching power supply according to Embodiment 1 will be described with reference to FIG. The DC / DC converter circuit includes input terminals 210 and 220 to which high-voltage direct-current power is input and primary-side switching elements 101, 102, 103, and 104. The DC / DC converter circuit converts the DC voltage input to the input terminals 210 and 220. Inverter circuit 100 for converting to AC voltage, input capacitor 170 provided on the input side of inverter circuit 100 and absorbing an AC component generated by the operation of inverter circuit 100, and resonant coil provided on the output side of inverter circuit 100 110 and the primary side switching elements 101, 102, 103, and 104 are connected in parallel, respectively, and cause a resonance operation with the resonance coil 110 and serve to suppress the switching loss of the primary side switching elements 101, 102, 103, and 104. Resonant capacitors 201, 202, 203, 2 4, a primary side coil conductor (high voltage side winding) 121 connected in series with the resonance coil 110, a secondary side coil conductor (low voltage side winding) 122 magnetically coupled to the primary side coil conductor 121, and A rectifier circuit 130 configured to convert an alternating voltage generated in the secondary side coil conductors 122 and 123 into a direct current voltage, which includes a transformer 120 composed of 123 and MOSFETs 131, 132, 133, and 134 serving as secondary side switching elements; A smoothing circuit 150 including a center tap 124 that is a connection point of the secondary coil conductors 122 and 123, a smoothing coil 160 that smoothes a DC voltage including an AC component at the center tap 124, and an output capacitor 180, and a smoothing circuit 150 Output terminals 310 and 320 for taking out a flat DC voltage output from. Here, the negative terminal 320 on the output side is not clearly provided, but the GND connection portions 141, 142, and 143 and the case 140 shown in FIG. .

  This DC / DC converter device receives high voltages from about 100 V to about 600 V supplied from a high-voltage battery mounted on the vehicle at the input terminals 210 and 220, and is a power supply voltage for in-vehicle accessory system components from the output terminals 310 and 320. A voltage of about 12V to 16V is output.

  FIG. 2 is a top view showing a structure of a connection portion between the transformer and the rectifier circuit constituting the DC / DC converter circuit shown in FIG. 3 and 4 are cross-sectional views taken along lines A-A ′ and B-B ′ of FIG. 2, respectively. Next, with reference to FIGS. 2 to 4, a specific structure of a connection portion between the transformer 120 and the rectifier circuit 130 in the DC / DC converter circuit of the first embodiment will be described. 2 to 4, the inverter circuit 100, the smoothing circuit 150, and some members or some of the members are omitted.

The primary coil conductor 121 of the transformer 120 is provided with a through-hole 127 that penetrates a middle leg 125a of an E-type core 125, which will be described later. It is wound around a resin bobbin 128 provided to rotate, and an end 121a of the primary coil conductor 121 extends from the bobbin 128 and is mounted on the printed circuit board 410 (inverter circuit 100 ( (Not shown)).

  The plate-like secondary side coil conductors 122 and 123 constitute a low voltage side winding of the transformer 120. The secondary side coil conductors 122 and 123 are formed by stamping a metal thin plate by press working, and are used for electrical connection with a coil portion arranged to wind around the middle leg 125a of the E-type core 125. It consists of end portions 122a, 122b, 123a, 123b, and 124. The secondary side coil conductor 122 is arranged on the upper side of the primary side coil conductor 121, and the secondary side coil conductor 123 is arranged on the lower side of the primary side coil conductor 121. Of the end portions 122a, 122b, 123a, 123b, 124 of the secondary coil conductors 122, 123, the end portions 122a, 122b, 122b, 122b, 124, which are connected to the secondary side switching elements (MOSFETs) 131, 132, 133, 134, 123a and 123b are punched so as to have a shape narrower than that of the coil portion, and are appropriately bent. Connection wiring patterns 421, 422, 423, and 424 on the printed circuit board 410 are respectively provided. In the description of the embodiment, although it is on the lower surface of the printed circuit board 410, it is shown on the upper surface side for the sake of convenience in FIG. 2) and is electrically connected to the secondary side switching elements 131, 132, 133, and 134 via It is connected. Further, the secondary coil conductors 122 and 123 are mechanically connected to the printed circuit board 410 at intermediate portions between the coil portions and the end portions 122a, 122b, 123a, and 123b by fastening members 531 and 532 such as rivets, respectively. Fastened and fixed.

  The magnetic core 125 forms a magnetic path of the transformer 120. In the present embodiment, the core of the transformer 120 is configured by combining the E-type core 125 and the I-type core 126 (see FIGS. 3 and 4). Further, the E-type core 125 is pressed against the casing 140 together with the I-type core 126 by a spring member (not shown) and fixed.

  MOSFETs 131, 132, 133, and 134 that are secondary side switching elements are connected to the secondary side coil conductors 122 and 123 to constitute a rectifier circuit 130. The drain terminals D of the MOSFETs 131, 132, 133, and 134 are soldered by a flow soldering in the through holes 421a, 422a, 423a, and 424a of the connection wiring patterns 421, 422, 423, and 424 provided on the printed circuit board 410. 512a, 513a, and 514a, and the end portions 122a, 122b, 123a, and 123b of the secondary coil conductors 122 and 123 are connected to the through holes 421b, 422b, and 423b of the connection wiring patterns 421, 422, 423, and 424, respectively. , 424b are joined by soldering 511b, 512b, 513b, 514b by flow soldering, whereby the end portions 122a, 122b, 123a, 123b of the secondary coil conductors 122, 123 and the MOSFETs 131, 132, 133, 134 dress A down terminal D is electrically connected. Further, the MOSFETs 131, 132, 133, and 134 are pressed and fixed to the housing 140 via the insulating heat radiation sheet 610 by spring members (not shown), so that the MOSFETs 131, 132, 133, and 134 are fixed mechanically and thermally. Further, it is coupled to the housing 140. Further, the MOSFET 131, 132, 133, 134 source terminal S is electrically connected to the housing 140 at GND connection locations 141, 142 by a metal conductor (not shown).

  The housing 140 accommodates the MOSFETs 131, 132, 133, and 134 of the switching power supply device, the E-type core 125 of the transformer 120, the I-type core 126, and the printed circuit board 410. The accommodated members are mechanically fixed to the housing 140 by spring members or screws, respectively.

The printed circuit board 410 includes an inverter circuit 100 (not shown), a connection wiring pattern (not shown) for a control signal input to the control terminal G of the MOSFETs 131, 132, 133, and 134, and the MOSFET 131. , 132, 133, and 134 are formed with connection wiring patterns 421, 422, 423, and 424 for connecting the secondary side coil conductors 122 and 123 to the drain terminal D. Further, the printed circuit board 410 is fixed to the housing 140 by screwing points (not shown).

  As shown in the cross-sectional view of FIG. 3, the terminal D of the MOSFET 132 (131) and the end 122b (122a) of the upper secondary coil conductor 122 penetrate the connection wiring pattern 422 (421) on the printed circuit board 410. The holes 422a and 422b (421a and 421b) are inserted, soldered, and connected. As shown in the enlarged view of the circled portion in FIG. 3, the solder 512a (511a) of the drain terminal D of the MOSFET 132 (131) and the solder 512b (511b) of the end 122b (122a) of the secondary coil conductor 122 are shown. ) Is preferably connected (formed integrally), and both soldered portions are as close as possible to each other, and the connecting wiring pattern 422 (421) connecting the two soldered portions is It is desirable not to apply solder resist. Similarly, as shown in the sectional view of FIG. 4, the drain terminal D of the MOSFET 133 (134) and the end 123 a (123 b) of the lower secondary coil conductor 123 are connected to the connection wiring pattern 423 on the printed circuit board 410. Inserted into the through holes 423a and 423b (424a and 424b) of (424), soldered, and connected. Similarly, it is better not to apply a solder resist to the connection wiring pattern 423 (424). Here, the connection wiring pattern and the solder are described as being formed on the lower surface (back surface) of the printed circuit board 410, but may be formed on the upper surface (front surface) or both surfaces.

  In the above-described embodiment, the example in which the center tap 124, which is the interconnection point between the secondary coil conductors 122 and 123, is used as the output terminal and connected to the smoothing coil 160 has been described. However, the second DC shown in FIG. As in the case of the DC / DC converter circuit, the center tap 124 is connected to the GND 144 of the housing 140 and connects the source terminals S of the secondary side switching elements 131, 132, 133, and 134 to the smoothing coils 160a and 160b. There may be. Even in that case, the effect of the present invention is also effective.

  In the above embodiment, the example in which the low-voltage side winding of the transformer 120 is configured by the two secondary coil conductors 122 and 123 has been described. However, in the case of having only one secondary coil conductor. For example, as shown in FIG. 6, the end of the secondary coil conductor connected to the secondary side switching elements 131, 132, 133, and 134 with the secondary side winding being 0.5 turns each. 122a, 122b, 123a, 123b may be configured such that a center tap 124 is provided at the midpoint of the coil portion on the opposite side across the transformer cores 125, 126. Alternatively, as shown in FIG. 7, a current doubler circuit configuration in which the drain terminals D of the secondary side switching elements 131, 132, 133 and 134 and the smoothing coils 160 a and 160 b are electrically connected without having a center tap. It can also be applied to. Even in that case, the effect of the present invention is also effective.

  In the above embodiment, an example in which two secondary switching elements 131, 132, 133, and 134 are connected to two ends of one secondary coil conductor 122 has been described. The number of secondary-side switching elements connected varies depending on the required output current specification. In this case, as shown in FIG. 8, the ends 700a to 700c of the secondary coil conductor 700 are individually provided for each of the terminals 801d to 803d of the secondary switching elements 801 to 803 to be connected. It is desirable.

Moreover, although the said embodiment demonstrated the example which comprised the primary side coil conductor 121 by winding a conducting wire with respect to resin-made bobbins 128, even if it comprises the primary side coil conductor 121 by another method, Good. For example, even when the primary side coil conductor 121 is configured by a wiring pattern on a printed circuit board provided separately from the printed circuit board 410, the effect of the present invention is also effective.

  Thus, in the present embodiment, the secondary coil conductors 122 and 123 are electrically connected to the connection wiring patterns 421, 422, 423, and 424 of the printed circuit board 410 by soldering, and these connection wiring patterns 421 are connected. , 422, 423, 424 and the secondary side semiconductor switching elements 131, 132, 133, 134 are connected to the secondary side coil conductors 122, 123 and the secondary side semiconductor switching without adding any members. Since the connection with the elements 131, 132, 133, and 134 can be realized, the number of parts can be reduced and the assemblability can be improved.

  The secondary coil conductors 122 and 123 include the same number of end portions 122a, 122b, 123a, and 123b as the drain terminals D of the MOSFETs 131, 132, 133, and 134 of the connected secondary semiconductor switching elements. And the drain terminal D of each MOSFET are connected via the connection wiring patterns 421, 422, 423, and 424 on the printed circuit board 410, respectively, so that the secondary coil conductors 122 and 123 and the secondary side are connected. The length of the connection wiring patterns 421, 422, 423, and 424 on the printed circuit board 410 that connects the semiconductor switching elements 131, 132, 133, and 134 can be minimized, and the amount of heat generated in the connection wiring patterns can be reduced. Can be reduced.

  Further, the end portions 122a, 122b, 123a, 123b of the secondary coil conductors 122, 123 and the terminals of the MOSFETs 131, 132, 133, 134 connected to these end portions are connected to the wiring patterns 421, 422 for connection. The heat generation amount in the connection wiring patterns 421, 422, 423, and 424 is further reduced by being inserted into two through holes provided in the regions 423 and 424, and connected by integrally formed solder. be able to.

  In addition, since the secondary coil conductors 122 and 123 are mechanically fixed to the printed circuit board 410 by fastening members 531 and 532, the secondary coil conductors 122 and 123 are directly connected to the housing 140. Compared with the case of mechanically fixing, it is possible to reduce the stress applied to the solder at the connection portion between the secondary coil conductors 122 and 123 and the second printed circuit board 420 due to an error during assembly, and solder cracks The occurrence of problems such as these can be reduced.

  The secondary coil conductors 122 and 123 are formed by stamping a thin metal plate by press working, but may be formed by an etching method or the like.

  Thus, according to the switching power supply device according to the first embodiment, the secondary coil conductor constituting the low voltage side winding of the transformer is directly mounted on the printed circuit board on which the secondary switching element is mounted. Thus, the transformer and the secondary rectifier circuit can be electrically connected without using an additional member, so that the number of parts can be reduced and the assemblability can be improved. By making the end of the secondary coil conductor thinner than the coil portion, even when the end of the secondary coil conductor is arranged in the immediate vicinity of the terminal of the secondary switching element, other wiring patterns of the secondary switching element Therefore, the terminal of the secondary side switching element and the end of the secondary side coil conductor can be arranged closer to each other without impairing the current capacity of the coil. By shortening the distance flowing on lint substrate current to suppress heat generation of printed circuit board, the effect can be expected that it is possible to improve the reliability of the printed circuit board. In addition, the end of the secondary coil conductor mounted on the printed circuit board is thinner than the coil part, so that the current capacity of the coil is not impaired, and solder defects due to the heat dissipation effect of the coil conductor are eliminated during soldering by flow. The effect that it can suppress can be expected.

  Note that the present invention is not limited to the above-described embodiment, and the embodiment can be appropriately modified and omitted within the scope of the invention.

  Moreover, in the figure, the same code | symbol shows the same or an equivalent part.

  100 inverter circuit, 120 transformer, 121 primary coil conductor, 122, 123 secondary coil conductor, 122a, 122b, 123a, 123b end of secondary coil conductor, 125a, 125b E type core, 126 I type core, 128 resin bobbin, 130 rectifier circuit, 131, 132, 133, 134 secondary side semiconductor switching element (MOSFET), 140 housing, 410 printed circuit board, 421, 422, 423, 424 connection wiring pattern, 531, 532 fastening Member, 610 Insulating heat dissipation sheet.

Claims (7)

An inverter circuit that converts DC power to AC power;
A transformer configured with a primary coil conductor and at least one plate-like secondary coil conductor, and connected to the output side of the inverter circuit;
A rectifier circuit configured by a plurality of switching elements and connected to the output side of the transformer,
A printed circuit board on which the inverter circuit and the rectifier circuit are mounted;
A wiring pattern for connection that is formed on the printed circuit board and connects an end of the secondary coil conductor and a terminal of the switching element,
A housing for accommodating the transformer and the printed circuit board;
An end portion of the secondary coil conductor and a terminal of the switching element are inserted into a through hole provided in the connection wiring pattern and mounted by soldering.   2. The switching power supply device according to claim 1, wherein an end of the secondary coil conductor is formed to be narrower than a coil portion of the secondary coil conductor.   The switching power supply according to claim 1 or 2, wherein an end of the secondary coil conductor is branched according to the number of terminals of the switching element to be connected.   The solder material at the end of the secondary coil conductor and the solder material at the terminal of the switching element are integrally formed on the connection wiring pattern. The switching power supply device according to any one of the above.   5. The switching power supply device according to claim 1, wherein the secondary coil conductor is mechanically fastened and fixed to the printed circuit board by a fastening member. 6.   The switching power supply device according to claim 5, wherein the switching power supply device is fastened and fixed at an intermediate portion between a coil portion and an end portion of the secondary side coil conductor. The secondary coil conductor is composed of two coil conductors, and the primary coil conductor is sandwiched between the two coil conductors. The switching power supply device according to Item 1.

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