JP5318071B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply having a bus bar structure with high heat dissipation.

  Conventionally, as a switching power supply for dropping a DC voltage to a desired DC voltage, a DC input voltage is converted into a rectangular pulse voltage by a switching element, and the converted rectangular wave voltage is applied to the primary winding of the transformer. There is a switching power supply that obtains a DC voltage by rectifying and smoothing a rectangular wave voltage extracted by a secondary winding with a circuit including a rectifier element, a choke coil, a capacitor, and the like. In particular, switching power supplies mounted on vehicles such as hybrid vehicles and electric vehicles step down the voltage of high-voltage batteries, which reaches several hundred volts, to 14V, which is used as the power system voltage of conventional vehicles, and many electric loads. Power is supplied to the lead battery. Since the electrical load connected to the 14V system reaches hundreds of amperes, heat generation from the transformer is large, and a large current flows through the secondary circuit by stepping down with the transformer, so the heat generation amount at the rectifying element is large. Become. For this reason, it is important to improve the heat dissipation of heat generated by the transformer and the rectifying element and to secure a plurality of heat dissipation paths.

  As one means for solving such problems, a heat dissipating foot is provided on a bus bar constituting the secondary coil of the transformer (hereinafter referred to as a secondary winding bus bar), and between the heat dissipating foot and the metal housing. There has been a technique of radiating heat to a metal casing through an insulating sheet provided on the substrate (Patent Document 1).

JP 2004-303823 A

  However, the switching power supply described in Patent Document 1 is a method in which an external connection terminal that connects a heat-dissipating foot provided on a bus bar for secondary winding and another electrical component is disposed across a hole through which the core passes. Therefore, if the design is performed based only on this method, when the bus bar for secondary winding is cut out from the metal plate (conductive plate), there is a case where the metal plate has to be discarded. If the purpose is to dissipate the heat generated by the transformer, heat dissipation can be ensured by the heat dissipating feet provided on the bus bar for secondary winding, but the transformer and rectifying element are placed close to each other. Because a large amount of heat generated in the rectifying element is transmitted to the bus bar for the secondary winding, radiated from the heat radiation foot of the bus bar for the secondary winding, and also radiated from the rectifying element directly under the rectifying element, There is a problem that heat concentrates directly under the transformer and the rectifying element.

  For this reason, the securing of the heat radiation path is insufficient with only the heat radiation foot provided to radiate heat directly under the transformer. For this reason, in order to solve the problem, it is necessary to secure a heat dissipation path other than the vicinity of the transformer and the rectifying element. However, in the switching power supply described in Patent Document 1, the secondary winding bus bar and the smoothing circuit bus bar are used. Since it is a separate member, it is a screw connection and it cannot be said that sufficient heat dissipation is ensured. Further, since the secondary winding bus bar and the smoothing circuit bus bar are formed of separate members, the number of parts and the number of screws are large, and the assemblability is poor.

  The present invention has been made to solve such a problem, and can efficiently dissipate heat generated in a transformer and a rectifier circuit through which a large current flows, and realize a reduction in the number of components. The purpose is to provide.

The switching power supply according to the present invention includes a transformer that converts an AC voltage applied to both ends of a primary winding from a secondary winding to a different AC voltage and outputs the transformer, and rectifies the AC voltage output from the secondary winding. a rectifier circuit which includes a smoothing circuit for smoothing the ripple voltage waveform obtained by the rectifier circuit, the switching power supply and an output terminal for outputting a DC voltage obtained by the smoothing circuit to the outside, the secondary of the transformer The winding has first and second secondary windings of a center tap transformer that is electrically divided by a center tap, and the switching power supply has fixing and heat dissipation for fixing the main body to a metal housing. includes a foot, said first secondary winding busbar composing the second secondary winding of the transformer, the smoothing circuit smoothing circuit busbar and the fixed and thermally radiative forming the interconnection of the Part is one which is constituted by forming body cut out integrally from the same conductive plate.

  The switching power supply according to the present invention is a formed body in which the formed body is cut out from a flat conductive plate and bent.

According to the switching power supply of the present invention, the secondary winding of the transformer has the first and second secondary windings of the center tap type transformer that is electrically divided by the center tap. A bus bar for secondary winding that constitutes the first and second secondary windings of the transformer, a bus bar for smoothing circuit that constitutes the wiring of the smoothing circuit, provided with fixing and heat dissipating feet for installation and fixing to the metal housing, and Since the fixed and heat radiating foot is formed of a formed body cut out integrally from the same conductive plate, the rectifying element is connected to form the first and second secondary windings of the center tap transformer. It is possible to improve the thermal conductivity and secure the heat dissipation path from the secondary winding bus bar side to the smoothing circuit bus bar side, to efficiently dissipate heat, and to reduce the number of components.

  Further, according to the switching power supply of the present invention, since the formed body is a formed body cut out and bent from the flat conductive plate, the bus bar for the secondary winding of the center tap transformer is formed from the same conductive plate. It can cut out integrally and can improve productivity. Alternatively, a plurality of smoothing circuit bus bars can be cut out integrally from the same conductive plate, and the number of turns of the inductor can be easily increased.

It is a circuit diagram which shows the circuit structure of the switch ignition power supply which can apply this invention. It is a top view which shows the layout of the bus-bar cut out from the electrically conductive board in Embodiment 1 of this invention. FIG. 3 is a plan view showing a bus bar initial formed body that is manufactured by being integrally cut from the same conductive plate in the first embodiment. 3 is a plan view showing a bus bar intermediate formed body produced by being bent in Embodiment 1. FIG. FIG. 3 is a plan view showing a bus bar final formed body manufactured by being bent in the first embodiment. FIG. 3 is a plan view showing a switching power supply using a bus bar final formed body in the first embodiment. It is sectional drawing which shows the AA line cross section of FIG. It is sectional drawing which shows the BB line cross section of FIG. It is a circuit diagram which shows the other circuit structure of the switch ignition power supply which can apply this invention.

Embodiment 1 FIG.
In order to explain the present invention, a center tap type diode rectification method, which is a general circuit method of an insulating switching power supply, is taken as an example. The center tap type diode rectification method is a kind of rectification circuit that can obtain a rectification waveform equivalent to a general full-wave rectification circuit. A circuit diagram of the center tap type diode rectification method is shown in FIG. FIG. 1 is a circuit diagram showing a circuit configuration of a switching power supply to which the present invention can be applied. A DC voltage to the switching power supply is applied to the input terminals 1a and 1b. The DC voltage is higher than the output voltage of the switching power supply. The inverter circuit 2 is composed of a semiconductor element such as a MOSFET, and converts a DC voltage input to the input terminals 1a and 1b into an AC voltage.

  The transformer 12 includes a magnetic core 4, a primary winding 3, an upper secondary winding 5, and a lower secondary winding 6. The primary winding 3, the upper secondary winding 5, and the lower secondary winding 6 are arranged by being wound around a middle leg (shaft core portion) provided on the magnetic core 4. The secondary winding 5 and the lower secondary winding 6 are electromagnetically coupled by the magnetic core 4. An alternating voltage waveform close to a rectangular wave generated by switching the semiconductor element of the inverter circuit 2 is applied to the primary winding 3. The upper secondary winding 5 outputs an AC voltage converted to a different voltage level according to the turn ratio of the transformer 12. The lower secondary winding 6 outputs an AC voltage converted to a different voltage level according to the turns ratio of the transformer 12. The upper secondary winding 5 and the lower secondary winding 6 are connected.

  The rectifying elements 7 a and 7 b rectify the AC voltage output from the upper secondary winding 5 and the lower secondary winding 6. In the example of FIG. 1, a diode module in which the anode terminals of the rectifying elements 7a and 7b are connected to a metal casing is used. Reference numeral 8 denotes a ground terminal connected to the metal casing of the switching power supply. In the example of FIG. 1, a metal casing is used as the ground of the secondary circuit. The inductor 9 smoothes the ripple voltage waveform rectified by the rectifying elements 7a and 7b. The capacitor 10 smoothes the ripple voltage waveform rectified by the rectifying elements 7a and 7b. The inductor 9 and the capacitor 10 constitute a smoothing circuit. A DC voltage obtained by the smoothing circuit is output from the output terminal 11 to the outside of the switching power supply. In the example of FIG. 1, since the ground of the secondary side circuit is set to the same potential as the metal casing, the output voltage is output between the output terminal 11 and the metal casing.

  FIG. 2 is a plan view showing a layout of bus bars cut out from one rectangular conductive plate (metal plate) in the first embodiment. FIG. 2 includes a secondary winding bus bar, a smoothing circuit bus bar, an output terminal connection bus bar, an output terminal, a fixing and heat dissipation foot, and a fixing foot, which are integrally arranged. According to the layout, the bus bar is cut out integrally from the same conductive plate, and the bus bar initial formed body is manufactured. The bus bar initial formed body 17 cut out is shown in FIG.

  In the bus bar initial forming body 17 that is cut out, the secondary winding bus bar 21 corresponds to the upper secondary winding 5 of the center tap transformer 12 in the circuit diagram (of FIG. 1), and is constituted by one turn of the bus bar. ing. The bus bar terminal 25a formed integrally with the secondary winding bus bar 21 (in FIG. 2, the position thereof is indicated by a broken line frame, the same applies hereinafter) is the cathode of the diode module corresponding to the rectifying element 7a in the circuit diagram. Connected to the terminal. The secondary winding bus bar 22 corresponds to the lower secondary winding 6 of the center tap transformer 12 in the circuit diagram, and is constituted by one turn of the bus bar. The bus bar terminal 25b formed integrally with the secondary winding bus bar 22 is connected to the cathode terminal of the diode module corresponding to the rectifying element 7b in the circuit diagram.

  The bus bar initial forming body 17 is bent by 90 ° at the bent portions 23a and 23b, and the secondary winding bus bar 22 is superimposed on the back side of the secondary winding bus bar 21 so as to coincide with the paper surface in a vertical projection manner. The secondary windings 5 and 6 of the center tap type transformer 12 in the circuit diagram are configured. FIG. 4 shows the bus bar intermediate formed body 18 produced by bending and bending the bent portions 23a and 23b. Reference numerals 24a and 24b denote through-holes through which the middle legs (axial centers) of the magnetic core 4 of the transformer 12 pass.

  3 and 4, the smoothing circuit bus bars 26 and 27 together correspond to the inductor 9 in the circuit diagram, and the winding of the smoothing choke coil is constituted by two turns of the bus bar. In FIG. 4, the bus bar intermediate formed body 18 is bent by 90 ° at the bent portions 28a and 28b, and the smoothing circuit bus bar 27 is superimposed on the front side of the smoothing circuit bus bar 26 so as to coincide with the paper surface in a vertical projection manner. The inductor 9 in the circuit diagram is configured. FIG. 5 shows the bus bar final formed body 19 that is manufactured by being bent and bent at the bent portions 28a and 28b. Reference numerals 29a and 29b denote through-holes through which the middle legs (axial centers) of the magnetic core 44 (FIG. 6), which is a component of the smoothing choke coil, pass.

  The bus bar forming body is cut out integrally from the same conductive plate, but is not necessarily bent. That is, if the bus bar for secondary winding 21, the bus bar for smoothing circuit 27, and the bus bar for connecting the bus bar are not required to be bent. However, when the bus bar initial formed body 17 is bent at the bent portions 23a and 23b to obtain the bus bar intermediate formed body 18, and further bent at the bent portions 28b and 28a, the bus bar final formed body 19 is obtained. The bus bars 21 and 22 for the secondary winding of the center tap transformer can be cut out integrally from the same conductive plate, and the productivity can be improved. Further, a plurality of smoothing circuit bus bars 26 and 27 can be cut out integrally from the same conductive plate, and the number of turns of the inductor 9 can be easily made plural.

  In FIG. 5, 30 is an output terminal, which outputs the DC voltage obtained by the smoothing circuit to the outside of the switching power supply. An output terminal connection bus bar 31 connects the smoothing circuit bus bar 27 and the output terminal 30. In FIG. 2, reference numeral 32 denotes an unbroken conductive plate made of, for example, copper or aluminum. In the first embodiment, the size of the conductive plate 32 is a rectangle circumscribing the output terminal 30 of the secondary winding bus bar 21, the secondary winding bus bar 22, and the output terminal connection bus bar 31. The fixing / radiating legs 33a to 33d are disposed in the rectangular conductive plate 32, and are formed by being cut out integrally from the conductive plate 32. Since the fixing and heat radiating feet 33a to 33d are arranged in the rectangular conductive plate 32, it is possible to reduce the disposal cost of the conductive plate. The fixing / radiating feet 33a and 33b are provided on the bus bar terminals 25a and 25b (rectifying element 7a and 7b connecting terminals) side of the secondary winding bus bars 21 and 22, respectively, that is, in the vicinity of the rectifying element. . Thereby, a large amount of heat generated in the rectifying elements 7a and 7b can be efficiently radiated.

  The fixed and heat radiating foot 33c is provided between the secondary winding bus bar 22 and the smoothing circuit bus bar 26. Thereby, the improvement of heat dissipation is realizable. The fixing / radiating foot 33 d is provided on the output circuit 30 side of the smoothing circuit bus bar 27. Thereby, the improvement of heat dissipation is realizable. In securing the fixing and heat dissipating feet 33a to 33d to the metal housing 48 (FIGS. 7 and 8), a sheet 49 (FIG. 8) having both heat dissipation and insulation is secured in order to ensure insulation therebetween. Interpose each. Reference numerals 34a to 34d denote fixing legs that perform a fixing function. When folded as shown in the bus bar final formed body 19 in FIG. 5 as in the first embodiment, the fixing legs 34a and 34b and the fixing legs 34d and 34c are the same. By adopting a structure that can be fixed with the screw 50 (FIG. 8), the number of screws can be reduced and the assemblability can be improved.

  As shown in FIG. 2 to FIG. 5, a secondary winding bus bar, a smoothing circuit bus bar, an output terminal connection bus bar, and an output terminal are included, and the formed body integrally cut from the same conductive plate is rectified. Improves thermal conductivity and secures a heat dissipation path from the secondary winding busbar side, which has a rectifying element connected to the element, to the smoothing circuit busbar side, reducing the number of components and improving assembly Can be realized. Further, the same effect as described above can be realized even in the formed body in which both the fixing and heat dissipating feet are integrally cut from the same conductive plate.

  In the first embodiment, the secondary winding bus bars 21 and 22, the smoothing circuit bus bars 26 and 27, the output terminal 30, and the output terminal connection bus bar 31 are integrally cut from the same conductive plate. In FIG. 2, even if only the right secondary winding bus bar 22 and the left smoothing circuit bus bar 26 are integrated, the same effect as described above can be realized. Further, regardless of whether or not the smoothing circuit bus bars 26 and 27 are present, a formed body obtained by integrally cutting at least the secondary winding bus bar and the output terminal connecting bus bar having the output terminal from the same conductive plate. It is possible to realize the improvement of thermal conductivity and the securing of the heat dissipation path from the secondary winding bus bar side connected to the rectifying element and having the rectifying element in the vicinity to the output terminal connecting bus bar side. It is possible to reduce the number of parts and improve assembly.

FIG. 6 is a plan view showing the switching power source assembled using the bus bar final formed body 19 in the first embodiment. 7 is a cross-sectional view showing a cross section taken along line AA of FIG. 8 is a cross-sectional view showing a cross section taken along line BB of FIG. The bus bar initial formed body 17 (FIG. 3) is bent to form the bus bar intermediate formed body 18 (FIG. 4), and further bent to form the bus bar final formed body 19 (FIG. 5). A secondary circuit of the switching power supply is configured by combining the magnetic cores 42 and 44, the rectifying element 43, and the smoothing capacitor 45 with the bus bar final formed body 19.

  6, 7 and 8, the primary winding 41 corresponds to the primary winding 3 of the transformer 12 in the circuit diagram (of FIG. 1). The primary side winding 41 has terminals 41a and 41b of a coil 41d formed by winding an electric wire so as to have a through hole 41c (FIG. 7) in the center and having an annular flat plate shape. The inner and outer diameters of the annular flat plate coil 41d are substantially the same as those of the secondary winding bus bars 21 and 22. The primary winding 41, which is an annular flat plate coil 41d, is interposed between the bent secondary winding bus bars 21 and 22 in the bus bar final formed body 19, and the through hole 41c of the primary winding 41 and The through-holes 24a and 24b of the secondary winding bus bars 21 and 22 are arranged to coincide with each other.

  The magnetic core 42 corresponds to the magnetic core 4 of the transformer 12, and has outer leg portions at both ends and cylindrical middle legs (axial center portions) 42a at the inner center thereof. The middle leg (axial center portion) 42 a passes through the through holes 24 a and 24 b of the secondary side winding bus bars 21 and 22 and the through hole 41 c of the primary side winding 41. The rectifying element 43 corresponds to the rectifying elements 7 a and 7 b in the circuit diagram, and rectifies the AC voltage obtained by the secondary windings 5 and 6 of the transformer 12. A bus bar terminal 25a of the secondary winding bus bar 21 and a bus bar terminal 25b of the secondary winding bus bar 22 are connected to the rectifying elements 7a and 7b, respectively. The rectifying element 43 is a diode module having a structure (shown in FIG. 1) in which its anode terminal is electrically connected to a metal casing. 7 and 8, 51 is an insulator.

  The magnetic core 44 constitutes a choke coil for a smoothing circuit, and has outer leg portions at both ends and a cylindrical middle leg (axial center portion) at the inner center. The middle leg (axial center) passes through the through holes 29a, 29b of the smooth circuit bus bars 26, 27. The smoothing capacitor 45 corresponds to the capacitor 10 in the circuit diagram, and its terminal 46 is connected to the output terminal of the choke coil. The terminal 47 electrically connects the smoothing capacitor 45 to the ground of the secondary circuit, that is, the metal casing. The output terminal 30 outputs the DC voltage obtained by the smoothing circuit to the outside of the switching power supply. In addition to the above description, 33a to 33d include a fixed foot for fixing a magnetic component such as a transformer and a choke coil to the metal housing, and a heat radiation foot for radiating heat generated in the secondary circuit to the metal housing. Also serves as. Reference numerals 34a to 34d denote fixing feet for fixing magnetic parts such as a transformer and a choke coil in addition to the above description. In the bent bus bar final formed body, it is possible to reduce the number of screws and improve the assemblability by adopting a structure that can be fixed with the same screw as the fixed feet 34a and 34b and the fixed feet 34d and 34c. it can.

  As described above, it is possible to improve the thermal conductivity and secure the heat dissipation path from the secondary winding bus bar side to which the rectifying element is connected to the smoothing circuit bus bar and the output terminal connecting bus bar side, and to generate heat. Heat can be efficiently radiated to the metal housing side. In addition, even for a secondary winding bus bar that is connected to a rectifying element and has a rectifying element in the vicinity, heat dissipation by the heat dissipation foot of the secondary winding bus bar and heat dissipation immediately below the rectifying element of the rectifying element In addition, since there is a heat radiation path to the smoothing circuit bus bar and the output terminal connection bus bar side, heat can be radiated efficiently, and concentration of heat directly under the transformer and the rectifying element can be prevented. Furthermore, by devising the position of the fixed foot provided with a heat dissipation function, it is possible to reduce the metal plate disposal while realizing improved heat dissipation. Furthermore, since it is formed of a formed body that is integrally cut from the same conductive plate, it is possible to achieve a reduction in the number of parts, a reduction in the number of screws, and an improvement in assembly. In the first embodiment, the center tap diode rectification method is taken as an example. However, the present invention is not limited to this, and other rectification methods such as a current doubler rectification method shown in FIG. 9 may be used. In the figure, the same reference numerals indicate the same or corresponding parts, and 9a and 9b are inductors.

1a, 1b Input terminal 2 Inverter circuit 3 Primary winding 4 Magnetic cores 5, 6 Secondary winding 7a, 7b Rectifier 8 Ground terminal 9, 9a, 9b Inductor 10 Capacitor 11 Output terminal 12 Transformer

17 Bus bar initial formed body 18 Bus bar intermediate formed body 19 Bus bar final formed body 21, 22 Bus bar for secondary winding 23a, 23b Bending portion 24a, 24b Through hole 25a, 25b Bus bar terminal 26, 27 Smoothing circuit bus bar 28a, 28b Bending Portions 29a, 29b Through-hole 30 Output terminal 31 Output terminal connection bus bar 32 Conductive plates 33a, 33b, 33c, 33d Fixing and heat dissipation feet 34a, 34b, 34c, 34d Fixing feet

41 Primary winding 41a, 41b Terminal 41c Through hole 41d Toroidal disk coil 42 Magnetic core 43 Rectifier element 44 Magnetic core 45 Smoothing capacitor 46, 47 Terminal 48 Metal housing 49 Sheet 50 Screw 51 Insulator

Claims (9)

A transformer that converts the alternating voltage applied across the primary winding from the secondary winding to a different alternating voltage and outputs it;
A rectifier circuit for rectifying the AC voltage output from the secondary winding;
A smoothing circuit for smoothing a ripple voltage waveform obtained by the rectifier circuit;
In a switching power supply comprising an output terminal that outputs the DC voltage obtained by the smoothing circuit to the outside,
The secondary winding of the transformer has first and second secondary windings of a center tap transformer that is electrically divided by a center tap,
The switching power supply includes a fixing and heat dissipation foot for fixing the main body to the metal housing,
The first secondary winding busbar composing the second secondary winding of the transformer, a smoothing circuit busbar and the fixed and radiating legs constituting the wiring of the smoothing circuit, integrally from the same conductive plate A switching power supply characterized in that the switching power supply is formed of a formed body cut out into two. The switching power supply according to claim 1, wherein the fixing / radiating foot is disposed between the bus bar for secondary winding and the bus bar for smoothing circuit. 2. The switching power supply according to claim 1, wherein the fixing / radiating foot is disposed on a rectifying element connecting bus bar terminal side of the secondary winding bus bar.   The switching power supply according to claim 1, wherein the smoothing circuit bus bar includes an inductor constituting the smoothing circuit. Further comprising an output terminal connection bus bar for connecting the smoothing circuit bus bar and the output terminal thereof, the output terminal and the output terminal connection bus bar together with the secondary winding bus bar and the smoothing circuit bus bar, the switching power supply according to any one of claims 1 to 4, characterized in that it is constituted by a formed body which is cut integrally from the same of the conductive plate. 6. The switching power supply according to claim 1 , wherein the formed body is a formed body cut out and bent from a flat conductive plate. The switching power supply according to claim 1, wherein the fixing / radiating foot is disposed on the output terminal side of the smoothing circuit bus bar. 6. The switching power supply according to claim 5, wherein the fixing / radiating foot is disposed between the smoothing circuit bus bar and the output terminal connecting bus bar. Same of the secondary winding busbar to the conductive plate, the smoothing circuit busbar, and when placing the said output terminal, said fixed and radiating foot to their circumscribed rectangle is located The switching power supply according to claim 1 .

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