DE102011016320B4 - Switching power supply - Google Patents

Abstract

A switching power supply, comprising: a transformer (12) which converts an AC voltage applied to the two ends of a primary winding (3) into different AC voltages for output via secondary windings (5, 6), a rectifier circuit which converts the voltage from the secondary windings (5, 6 ) output AC voltages, a smoothing circuit that smooths a superimposed AC voltage waveform obtained by the rectifier circuit, and an output terminal (11) from which a DC voltage obtained by the smoothing circuit is output to the outside, the switching power supply comprising: bus bars for the secondary windings (21, 22), which form the secondary windings (5, 6) of the transformer (12), and bus bars for the smoothing circuit (26, 27), which form the circuit of the smoothing circuit, in which the bus bars for the secondary windings (21, 22) of the transformer (12). a first secondary winding (5) and a second secondary winding (6) of a center tap transformer, which are electrically divided by a center tap, the bus bars for the secondary windings (21, 22) and the bus bars for the smoothing circuit (26 , 27) are constructed by a formed body cut out entirely from the same conductive plate (32), characterized in that the switching power supply further has fastening and heat-dissipating leg sections (33) which are for arranging and fastening the body of the busbars to a metal housing of the switching power supply ,wherein the fastening and heat-dissipating leg portions (33), formed by the formed body and together with the bus bars for the secondary windings (21, 22) and the bus bars for the smoothing circuit (26, 27), are integrally cut out of the same conductive plate (32). .

Description

FIELD OF THE INVENTION

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

STATE OF THE ART

So far, a switching power supply that reduces a DC voltage to a desired DC voltage is a switching power supply in which a DC voltage is converted to a rectangular wave pulse voltage by rectifier elements. The converted square wave voltage is applied to a primary winding of a transformer, and a square wave voltage taken across a secondary winding of the transformer is rectified and smoothed by a circuit composed of rectifier elements, a reactor, a capacitor and the like. Consequently, the desired DC voltage is obtained. In addition, a switching power supply, mounted on vehicles such as a hybrid car or an electric car, transforms a voltage of a high-voltage battery that reaches several hundred volts down to 14 volts, which is used as a supply voltage in conventional cars and supplies many electrical consumers and lead batteries. The electrical load connected to a 14 volt system reaches more than a hundred amperes, due to which the heat generation of the transformer is high and a high current flows in a secondary sub-circuit due to step-down through the transformer and consequently the amount of heat generation in the rectifier elements is large . For this reason, it is an important measure to improve the heat dissipation characteristics for the heat generated in the transformer and the rectifier elements and to ensure a variety of heat dissipation paths.

As a means of solving such a problem, there is a technique in which heat dissipating leg portions are provided as bus bars (hereinafter referred to as bus bars for secondary windings) constituting secondary sub-coils of a transformer, and heat is provided between the heat dissipating leg portions and the metal case Insulation tracks are led to a metal housing JP 2004 - 303 823 A .

However, this is in JP 2004 - 303 823 A disclosed switching power supply is the result of a method in which the heat dissipating leg portions provided as bus bars for the secondary windings and external connection terminals for connecting other electrical components are arranged while a core passes through sandwich-shaped hole portions. Thus, when the design is made based only on this method, there is a case where the excess machining allowance of the metal plate increases when the bus bars for the secondary windings are cut out of a metal plate (conductive plate). Further, when the only objective is to dissipate the heat generated by the transformer, the heat dissipation properties can be ensured by the heat dissipating leg portions provided in the bus bars for the secondary windings. However, in the case where the transformer is disposed near the rectifier elements, a large amount of heat generated by the rectifier elements is transferred to the bus bars for the secondary windings, and the heat is dissipated from the heat dissipating leg portions of the bus bars for the secondary windings. In addition, the heat from the rectifier elements is dissipated directly below the rectifier elements. This creates the problem that the heat is concentrated directly under the transformer and rectifier elements.

For this reason, it is insufficient to ensure the heat dissipation paths only through the heat dissipating leg portions provided for dissipating the heat directly under the transformer. Thus, to solve the problem, it is necessary to ensure a heat dissipation path to an area other than the vicinity of the transformer and rectifier elements. In the in the JP 2004 - 303823 However, in the switching power supply disclosed, the bus bars for the secondary windings are different parts than the bus bars for a smoothing circuit. Consequently, the two bus bars are connected by screws and it cannot therefore be said that sufficient heat dissipation properties can be guaranteed. Furthermore, the switching power supply is designed such that the bus bars for the secondary windings are different parts than the bus bars for the smoothing circuit, and thereby there are a large number of components and screws and the workability during assembly is low.

The JP 2007 - 97 390 A discloses features that fall under the preamble of claim 1. The JP 2000 - 14 149 A , JP 2010 - 28,930 A , JP 2004 - 296 913 A and JP 2002 - 281 758 A form further state of the art.

PRESENTATION OF THE INVENTION

The present invention has been carried out to solve the above problems, and thus, an object of the present invention is to provide a switching power supply capable of efficiently dissipating heat generated by a transformer and a rectifier circuit through which a large current flows and which a reduction in the number of components is achieved.

A switching power supply according to the present invention has the features of claim 1.

According to the switching power supply of the present invention, improvement in thermal conductivity and ensuring the heat dissipation path can be achieved from the side of the bus bars for the secondary windings connected to rectifier elements to the side of the bus bars for the smoothing circuit, heat dissipation can be efficiently achieved and a reduction in the Number of components can be achieved.

Further, in a switching power supply according to the present invention, the formed body is a formed body cut from a conductive plate which has a tabular shape and is folded.

According to the switching power supply of the present invention, the formed body is cut out of the tabular conductive plate and folded, and the bus bars for the secondary windings of a center tap transformer can be cut out in one piece from the same conductive plate, whereby productivity can be improved. Alternatively, a plurality of bus bars for the smoothing circuit can be integrally cut out of the same conductive plate, and the number of turns of an induction coil can thus be easily multiplied.

The foregoing and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

• 1 is a circuit diagram showing a circuit arrangement of a switching power supply applicable to the present invention;
• 2 Fig. 10 is a plan view showing a layout of bus bars cut from a conductive plate of Embodiment 1 of the present invention;
• 3 Fig. 10 is a plan view showing a preformed body of the bus bars manufactured by integrally cutting from the same conductive plate of Embodiment 1;
• 4 Fig. 10 is a plan view showing an intermediate formed body of the bus bars of Embodiment 1 made by folding;
• 5 Fig. 10 is a plan view showing a fully formed body of the bus bars of Embodiment 1 made by folding;
• 6 Fig. 10 is a plan view showing a switching power supply using the fully formed body of the bus bars of Embodiment 1;
• 7 is a sectional view showing a cross section along line AA in 6 shows;
• 8th is a sectional view showing a cross section along line BB in 6 shows; and
• 9 is a circuit diagram showing another circuit arrangement of a switching power supply applicable to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

In order to explain the present invention, a center-tap diode rectifier system, which is a general circuit system of an isolated switching power supply, is given as an example. The center-tap diode rectifier system is a type of rectifier circuit that can obtain a rectified waveform equivalent to a general all-wave rectifier circuit. A circuit diagram of a center tap diode rectifier system is in 1 shown. 1 is a circuit diagram showing a circuit arrangement of a switching power supply applicable to the present invention. A DC voltage on the switching power supply is applied to the input poles 1a, 1b. A higher voltage than the output voltage of the switching power supply is applied as a direct voltage. An inverter circuit 2 is composed of semiconductor elements such as metal-oxide-semiconductor field effect transistors (MOSFETs), and the DC voltage supplied to the input poles 1a, 1b is converted into an AC voltage.

A transformer 12 is composed of a magnetic material 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 around a middle leg (axial core section). represents in the magnetic material core 4, wound. The primary winding 3, the upper secondary winding 5 and the lower secondary winding 6 are electromagnetically coupled via the magnetic material core 4. An AC waveform, similar to a square wave, generated by switching the semiconductor elements of the inverter circuit 2, is applied to the primary winding 3. An alternating voltage, converted to a different voltage level according to the turns ratio of the transformer 12, is output to the upper secondary winding 5. An alternating voltage converted into a different voltage level according to the turns ratio of the transformer 12 is output to the lower secondary winding 6. The upper secondary winding 5 is connected to the lower secondary winding 6.

Rectifier elements 7a, 7b rectify the alternating voltages, each output by the upper secondary winding 5 and the lower secondary winding 6. The example from 1 is a diode module in which an anode terminal of each of the rectifier elements 7a, 7b is connected to a metal case. Reference number 8 denotes a ground connected to the metal housing of the switching power supply. In the example from 1 the metal housing is used as ground for a secondary branch circuit. An induction coil 9 smoothes a superimposed AC voltage waveform rectified by the rectifier elements 7a, 7b. A capacitor 10 smoothes the superimposed AC voltage waveform rectified by the rectifier elements. The inductor 9 and the capacitor 10 constitute a smoothing circuit. A DC voltage obtained by the smoothing circuit is output to the outside of the switching power supply via the output terminal 11. The grounding of the secondary branch circuit in the example 1 randomly has the same potential as the metal case. Consequently, the output voltage is output between the output terminal 11 and the metal case.

2 is a plan view showing a layout of bus bars cut from a sheet of a rectangular conductive plate (metal plate) of Embodiment 1. In 2 bus bars for the secondary windings, bus bars for the smoothing circuit, a bus bar for connecting the output terminal, the output terminal, fastening and heat-dissipating leg sections and fastening legs are included and arranged in one piece. In accordance with the layout, the bus bars are integrally cut out from a sheet of the same conductive plate, so that a preformed body of the bus bars 17 is manufactured. The cut out preformed body of the busbars 17 is in 3 shown.

In the cut out preformed body of the bus bars 17 in the circuit diagram in 1 A bus bar for the secondary winding 21 corresponds to the upper secondary winding 5 of the center tap transformer 12 and is designed by one turn of the bus bar. A bus bar terminal 25a formed integrally with the bus bar for the secondary winding 21 (its corresponding position is indicated by a dashed frame in 2 shown; (hereinafter, corresponding positions are shown in the same way) is connected to a cathode terminal of the diode module, corresponding to the rectification element 7a in the circuit diagram. A bus bar for the secondary winding 22 corresponds to the lower secondary winding 6 of the center tap transformer 12 in the circuit diagram and is designed by one turn of the bus bar. A busbar connection 25b, formed in one piece with the busbar for the secondary winding 22, is connected in the circuit diagram to a cathode connection of the diode module, corresponding to the rectifier element 7b in the circuit diagram.

The preformed body of the bus bars 17 is folded by 90° at each of the bending portions 23a, 23b, and the bus bar for the secondary winding 22 is coincidently overlapped with the back of the secondary winding 21 in a manner projected perpendicular to the blade portion to form the secondary windings 5, 6 in the Circuit diagram of the center tap transformer 12 to form. 4 shows an intermediate formed body of the bus bars 18 made by folding at the bending portions 23a, 23b and overlapping. Reference numerals 24a, 24b indicate through holes where the middle leg (axial core portion) of the magnetic material core 4 of the transformer 12 passes.

In 3 and 4 Both bus bars for the smoothing circuit 26, 27 are combined to correspond to the induction coil in the circuit diagram, and one winding of a smoothing reactor is constructed of two turns of the bus bars. In 4 The intermediate body of the bus bars 18 is folded by 90° at each of the bending portions 28a and 28b. The smoothing circuit bus bar 27 is made to overlap in accordance with the opposite side of the smoothing circuit bus bar 26 in a manner projected perpendicular to the side portion to form the induction coil 9 of the circuit diagram. 5 shows a fully formed body of the bus bars 19, which is made by folding at the bending portions 28a and 28b and by overlapping. The reference numbers 29a, 29b are through holes through which a central leg (axial core portion) of a magnetic material core 44 ( 6 ), which is a partial element of the smoothing throttle, passes through.

The formed body of the bus bars is integrally cut from the same conductive plate, but is not necessarily folded. That is, when the secondary winding bus bar 21, the smoothing circuit bus bar 27 and their connecting bus bars are provided, the bending operation is not required. However, when the preformed body of the bus bars 17 is folded at the bending portions 23a, 23b to obtain the intermediately formed body of the bus bars 18, and the intermediately formed body of the bus bars 18 is further folded at the bending portions 28b, 28a to form the finished body of the busbars 18 To obtain bus bars 19, the bus bars for the secondary windings 21, 22 of the center-tap transformer can be integrally cut from the same conductive plate, thereby improving productivity. Further, a plurality of bus bars for the smoothing circuit 26, 27 can be integrally cut out of the same conductive plate, and the number of turns of the induction coil 9 can be easily multiplied.

In 5 Reference numeral 30 denotes an output terminal from which the DC voltage obtained by the smoothing circuit is output to the outside of the switching power supply. Reference numeral 31 denotes a bus bar for connecting the output terminal and connects the bus bar for the smoothing circuit 27 to the output terminal 30. In 2 32 denotes a sheet of continuously conductive plate made of, for example, copper or aluminum. In Embodiment 1, the format of the conductive plate 32 is a rectangle, which comes into external contact with the secondary winding bus bar 21, the secondary winding bus bar 22, the output terminal 30 of the bus bar for connecting the output terminal 31, respectively. Fixing and heat dissipating leg portions 33a to 33d are disposed in the rectangular conductive plate 32 and are formed via integral cutting from the conductive plate 32. The fixing and heat dissipating leg portions 33a to 33d are arranged in the rectangular conductive plate 32. Thus, the excess processing allowance of the conductive plate can be reduced. The fixing and heat dissipating leg portions 33a, 33b are respectively provided on the side of the bus bar terminals 25a, 25b (terminals for connecting the rectifier elements 7a, 7b) of the bus bars for the secondary windings 21, 22 in the vicinity of the rectifier elements. This allows a large amount of heat generated in the rectifier elements 7a, 7b to be efficiently dissipated.

The fixing and heat dissipating leg portion 33c is disposed between the secondary winding bus bar 22 and the smoothing circuit bus bar 26. This enables improved heat dissipation properties. The fixing and heat dissipating leg portion 33d is disposed on the output terminal 30 side of the bus bar for the smoothing circuit 27. This allows the heat dissipation properties to be improved. In order to aid in attaching the attaching and heat dissipating leg portions 33a to 33d to a metal housing 48 ( 7 , 8th ) to ensure isolation between them, an intervening Sheet 49 ( 8th ) manufactured with heat-dissipating and insulating properties. Reference numerals 34a to 34d are fastening legs that perform a fastening function. As described in Embodiment 1, it is constructed such that the fixing legs 34a, 34b and the fixing legs 34d, 34c are secured by the same screw 50 ( 8th ) can be attached if they are as in the fully formed body of the busbars 19 in 5 shown folded. Accordingly, the number of screws is reduced and the workability in assembling can be improved.

As in 2 until 5 As shown, the formed body, which includes the bus bars for the secondary windings, the bus bars for the smoothing circuit, the bus bar for connecting the output terminal and the output terminal and is integrally cut from the same conductive plate, can achieve an improvement in thermal conductivity and ensure the heat dissipation path. from the side of the bus bars for the secondary windings, near and connected to the rectifier elements, to the side of the bus bars for the smoothing circuit, as well as a reduction in the number of components and an improvement in the workability in assembling. Furthermore, the same effect can be achieved in a formed body integrally cut together with the fastening and heat dissipating leg portions from the same conductive plate.

Arbitrarily, in Embodiment 1, the bus bars for the secondary windings are 21, 22, the bus bars for the smoothing circuit are 26, 27, the output terminal is 30 and the bus bar for connecting the output terminal 31 is formed by the formed body integrally cut from the same conductive plate. However, in 2 the same effects can be achieved even if only the right-hand bus bar for the secondary winding 22 and the left-hand bus bar for the smoothing circuit 26 are in one piece. Furthermore, regardless of whether or not the bus bars for the smoothing circuit 26, 27 are provided, at least the bus bars for the secondary windings and the bus bar for connecting the output terminal, including the output terminal, may be constructed by a formed body integrally cut from the same conductive plate. The formed body thus constructed can achieve an improvement in thermal conductivity and ensuring the heat dissipation path from the side of the bus bars for the secondary windings connected to and near the rectifier elements to the side of the bus bar for connecting the output terminal, as well as a reduction in the number of components and an improvement in workability during assembly.

6 Fig. 10 is a plan view showing a switching power supply assembled by using the finished body of the bus bar 19 in Embodiment 1. 7 is a sectional view along line AA 6 . 8th is a sectional view along line BB 6 . A bending operation is performed on the preformed body of the bus bar 17 ( 3 ) executed to the intermediately formed body of the bus bar 18 ( 4 ) and bending work is performed on the intermediately formed body of the bus bar 18 to form the fully formed body of the bus bar 19 ( 5 ) to create. The fully formed body of the bus bar 19 is combined with magnetic material cores 42, 44, rectifier elements 43 and a capacitor 45. Accordingly, the secondary sub-circuit of the switching power supply is formed.

A primary secondary winding 41 in 6 , 7 and 8th corresponds to the primary winding 3 of the transformer 12 in the circuit diagram in 1 . A primary subwinding 41 is a coil having terminals 41a, 41b, the coil 41d being formed into an annular and flat shape in such a manner that wire is wound to have a through hole 41 at the center ( 7 ). The inner diameter and the outer diameter of the annular flat coil 41d are approximately the same as those of the bus bars for the secondary auxiliary windings 21, 22. In the finished body of the bus bar 19, the primary auxiliary winding 41 serving as the annular flat coil 41 is manufactured, to intervene between the curved bus bars for the secondary auxiliary windings 21, 22. Thus, an arrangement is created in which the through hole 41c of the primary auxiliary winding 41 coincides with the through holes 24a, 24b of the bus bars for the secondary auxiliary windings 21, 22.

The magnetic core 42 corresponds to the magnetic core 4 of the transformer 12 and has outer leg portions at both ends and an inner columnar middle leg (axial core portion) 42a at its center. The middle leg (axial core portion) 42a passes through the through holes 24a, 24b of the bus bars for the secondary sub-windings 21, 22 and the through hole 41c of the primary sub-winding 41. The rectifier elements 43 correspond to the rectifier elements 7a, 7b in the circuit diagram and rectify the alternating voltages obtained via the secondary windings 5, 6 of the transformer 12. The bus bar terminal 25a of the secondary winding bus bar 21 and the bus bar terminal 25b of the secondary sub winding bus bar 22 are connected to the rectifier elements 7a, 7b, respectively. The rectifier elements 43 are each the diode module in which the anode terminal is constructed to be electrically connected to the metal housing (shown in 1 ) to be connected. The reference number 51 indicates in 7 and 8th an insulator.

The magnetic material core 44 constitutes the choke coil for the smoothing circuit and has outer leg portions at both ends and an inner columnar middle leg (axial core portion) at its center. The middle leg (axial core portion) passes through the through holes 29a, 29b of the bus bars for the smoothing circuit 26, 27. The smoothing capacitor 45 corresponds to the capacitor 10 in the circuit diagram and its connection 46 is connected to the end output of the choke coil. A terminal 47 electrically connects the smoothing capacitor 45 to the ground of the secondary subcircuit, that is, to the metal housing. The DC voltage obtained by the smoothing circuit is output to the outside of the switching power supply via the output terminal 30. In addition to the above-mentioned description, reference numerals 33a to 33d double the mounting legs that attach magnetic components such as the transformer and the reactor to the metal case and the heat dissipating leg portions that dissipate the heat generated by the secondary subcircuit to the metal case. In addition to the above-mentioned description, 34a to 34d identify fastening legs that contain magnetic components Attach the components such as the transformer and the choke coil. The finished body of the bus bars to which the bending work has been applied, such as the fixing legs 34a, 34b and the fixing legs 34d, 34c, is constructed so that the fixing legs can be fixed by the same screw. Consequently, the number of screws is reduced and the workability in assembling can be improved.

As described above, improving the thermal conductivity and ensuring the heat dissipation paths can be achieved from the side of the bus bars for the secondary windings connected to the rectifier elements to the side of the bus bars for the smoothing circuit and the bus bar for connecting the output terminal, and achieve efficient heat dissipation the side of the metal housing is done. Furthermore, even in the case that the bus bars for the secondary windings are connected to the rectifier elements and the rectifier elements are in their vicinity, there are the heat dissipation paths to the side of the bus bars for the smoothing circuit and the bus bar for connecting the output terminal, in addition to the heat dissipation means the heat-dissipating leg sections of the busbars for the secondary windings and the heat dissipation directly under the rectifier elements. This enables efficient heat dissipation and prevents the concentration of heat directly below the transformer and rectifier elements. Furthermore, the arrangement of the fixing legs is designed with the heat dissipation function, so that accordingly the excess processing allowance of the metal plate can be reduced while improving the heat dissipation properties. Furthermore, the structure is manufactured via the formed body integrally cut from the same conductive plate, and thereby the reduction in the number of components, the reduction in the number of screws and the improvement in the workability in assembling can be achieved. The center-tap diode rectifier system of Embodiment 1 is given as an arbitrary example, but the circuit is not limited thereby; for example, other rectifier systems such as an in 9 Current doubling rectifier system shown permitted. In addition, the same reference numerals in the figures indicate identical or equivalent parts. The reference numbers 9a, 9b identify induction coils.

Although the preferred embodiments of the present invention have been shown and described, it is to be understood that this disclosure is for purposes of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

Claims (10)

A switching power supply, comprising: a transformer (12) which converts an AC voltage applied to the two ends of a primary winding (3) into different AC voltages for output via secondary windings (5, 6), a rectifier circuit which converts the voltage from the secondary windings (5, 6 ) output AC voltages, a smoothing circuit that smoothes a superimposed AC voltage waveform obtained by the rectifier circuit, and an output terminal (11) from which a DC voltage obtained by the smoothing circuit is output to the outside, the switching power supply comprising: bus bars for the secondary windings (21, 22) , which form the secondary windings (5, 6) of the transformer (12), and bus bars for the smoothing circuit (26, 27), which form the circuit of the smoothing circuit, in which the bus bars for the secondary windings (21, 22) of the transformer (12 ) consist of a first secondary winding (5) and a second secondary winding (6) of a center tap transformer, which are electrically divided by a center tap, the bus bars for the secondary windings (21, 22) and the bus bars for the smoothing circuit (26, 27) are constructed by a formed body cut out entirely from the same conductive plate (32), characterized in that the switching power supply further has fastening and heat-dissipating leg sections (33) which are used to arrange and fasten the body of the busbars to a metal housing of the Switching power supply, the fastening and heat-dissipating leg sections (33), formed by the formed body and together with the bus bars for the secondary windings (21, 22) and the bus bars for the smoothing circuit (26, 27) being made entirely from the same conductive plate (32) are cut out. Switching power supply according to Claim 1 , in which the fastening and heat-dissipating leg sections (33) between the bus bar for the secondary windings (21, 22) and the bus bar nen for the smoothing circuit (26, 27) are arranged. Switching power supply according to Claim 1 , in which the fastening and heat-dissipating leg sections (33) are arranged on the side of a busbar connection for connecting rectifier elements of the busbars for the secondary windings (21, 22). Switching power supply according to Claim 1 , in which the bus bars for the smoothing circuit (26, 27) include an induction coil (9) forming the smoothing circuit. Switching power supply according to one of the Claims 1 until 4 , in which the formed body is cut out of the conductive plate (32) which is folded. Switching power supply according to one of the Claims 1 until 4 , further comprising a bus bar for connecting the output terminal (31) in the switching power supply, the bus bar for connecting the output terminal (31) connecting the bus bars for the smoothing circuit (26, 27) to the output terminal (30), the output terminal (30) and the bus bar for connecting the output terminal (31) together with the bus bars for the secondary windings (21, 22) and the bus bars for the smoothing circuit (26, 27) are integrally designed cut out of the same conductive plate (32) over the formed body. Switching power supply according to Claim 6 , in which the formed body is cut out of the conductive plate (32) which is folded. Switching power supply according to Claim 6 , in which the fastening and heat-dissipating leg sections (33) are arranged on the side of the output connection (30) of the bus bars for the smoothing circuit (26, 27). Switching power supply according to Claim 6 , in which the fastening and heat-dissipating leg sections (33) are arranged between the bus bars for the smoothing circuit (26, 27) and the bus bar for connecting the output terminal (31). switching power supply Claim 6 , wherein when the bus bars for the secondary windings (21, 22), the bus bars for the smoothing circuit (26, 27) and the output terminal (30) are arranged in the same tabular conductive plate (32), the fastening and heat-dissipating leg portions (33) are arranged in a rectangle that comes into external contact with them.

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