JP3259576B2 - Assembly structure of rectifier for switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembling structure of a rectifier (diode module) used in a switching power supply having a large current capacity.

[0002]

2. Description of the Related Art As is well known, a switching power supply includes a rectifying unit on the input side, a switching element such as an IGBT, a transformer, a rectifying unit connected to a secondary side (output side) of the transformer, a smoothing circuit, and the like. I have. FIG. 3 shows a secondary circuit of such a switching power supply. In the figure, reference numeral 1 denotes a rectifying unit (portion surrounded by a dotted line), 2 denotes a transformer, 3 denotes a smoothing choke coil, and 4 denotes a smoothing capacitor. The rectifying unit 1 has diodes 5, 6 and 5,
6 and a noise reduction capacitor 7, 8 connected in parallel with the diode 6, and a noise reduction bead core 9 interposed in series with the diodes 5, 6.

In a large-capacity (for example, current capacity 100 A class) power switching power supply, the rectifier 1
Is configured as a diode module in which a plurality of diodes are connected in parallel, and a large loss occurs when the diodes are energized. In order to remove the generated heat, the diode module is connected to a radiator (for example, a radiating fin). ), And the diode module is wired directly to the bus bar for use in flowing a large current.

FIG. 4 shows an example of an assembling structure of a diode module used in a conventional power switching power supply. In the figure, reference numeral 10 denotes an aluminum heat radiator, on which a bus bar (copper flat plate) 12 and diodes 5 and 6 are superposed on the heat radiator 10 via an insulating sheet 11 with their cathode electrode surfaces facing downward. , And is fixed to the heat radiator 10 with the screw 13. The capacitors 7 and 8 with leads are arranged so as to straddle the upper surfaces of the packages of the diodes 5 and 6 so as to shorten the lead wiring length and reduce the wiring inductance as much as possible, and are soldered between the anode and cathode electrodes of the diodes. Further, after inserting the bead core 9 in the middle of the lead wire 14 connected to and pulled out from the anode electrodes of the diodes 5 and 6, the tip of the lead wire 14 is soldered to bus bars 15 and 16 disposed above the diodes. are doing.

[0005]

The above-described conventional diode module assembly structure has the following problems. That is, in FIG.
The heat generated due to the loss of 6 includes heat radiation from the package surface, but most of the heat is transferred from the anode and cathode electrodes to an external metal part. In this case, part of the heat from the cathode electrode surface side is transferred to the bus bar 12 because the bus bar 12 is interposed in the heat transfer path between the cathode bar and the heat radiator 10. On the other hand, the heat from the anode electrode is transmitted through the lead wire 14 to the bus bars 15 and 16, and locally heats the bead core 9 on the way. For this purpose, 1) the transformer 2 and the choke coil 3 (see FIG. 2) connected in front of the bus bars 12, 15, and 16 are greatly affected by the heat transmitted from the diodes 5 and 6, and the temperature rise is large. Become.

2) Since the heat generation of the diodes 5 and 6 rapidly changes with the start / stop of the switching power supply or a large load change, the lead wires 14 and the bus bars 15 and
In some cases, solder peeling may occur at the soldered portion with the lead 16, or a trouble may occur in which a bead core (made of ferrite) inserted into the lead wire 14 is broken by a thermal stress.

3) In particular, the capacitors 7 and 8 with leads are provided with diodes 5 and 5 so as to keep the wiring inductance low.
Because it is necessary to perform soldering by making it almost adhered to 6,
Workability at the time of assembly becomes extremely poor. The present invention has been made in view of the above points, and has as its object to provide an assembly structure of a rectifying unit for a switching power supply, which solves the above-described problems and has excellent effects on heat dissipation of a rectifier and assemblability. Is to do.

[0008]

In order to achieve the above object, in the assembly structure according to the present invention, a surface mount type rectifying element, a capacitor for reducing noise, and an external terminal connected to a bus bar are provided as a metal as a heat sink. Assume that it is arranged on a base printed wiring board, soldered and mounted on its conductor pattern, and a radiator is directly attached to the metal base printed wiring board.

In the above structure, the external connection terminal also serving as an interconnecting lead of the rectifying element is constituted by a self-supporting terminal plate, and the leg of the terminal plate is soldered to the metal base printed wiring board. It is also preferable to form a protruding lead piece that rises upward from the location corresponding to each rectifier element and connects to the bus bar with respect to the terminal plate of the external connection terminal. There is also a configuration in which a bead core is inserted and set.

[0010]

In the above construction, the metal-based printed wiring board is based on a metal substrate such as aluminum, on which a conductor pattern is formed via a thin insulating layer. The rectifying element (diode), the capacitor chip, and the leg of the external terminal are soldered.

Therefore, the metal base printed wiring board having high heat conductivity functions as a heat sink, and the heat generated by the rectifying element and the heat transferred from the rectifying element to the external terminal are transferred to the bus bar before the metal base printed wiring board. The heat is efficiently transferred to the radiator through the wiring board, and the heat is radiated out of the system from here. This makes it difficult for the heat generated by the rectifier to be transmitted to the transformer, choke coil, and the like of the switching power supply via the bus bar.

Further, the conductor pattern of the metal-based printed wiring board has a much smaller inductance component when a high-frequency current is applied than a lead wire, and therefore, the noise reduction capacitor connected in parallel with the rectifying element must be connected to the rectifying element. The effect of wiring inductance is small even if soldered to a slightly distant position, and by arranging the rectifier and the capacitor apart, the work of assembling parts including soldering becomes easy and the wiring of external terminals By forming the plate into a self-supporting shape, reflow soldering can be performed without using a holding jig or the like, and assembling workability is greatly improved.

Further, since the terminal board itself is soldered to a metal base printed wiring board having high heat conductivity,
If a bead core is attached to this terminal plate, the thermal stress applied to the bead core at the time of starting / stopping the switching power supply and a large load change is reduced, and troubles such as cracks can be safely avoided.

[0014]

FIG. 1 (a) shows a configuration of an embodiment of the present invention.
This will be described with reference to (b) and FIG. In the drawings of the embodiment, the same components corresponding to FIGS. 3 and 4 are denoted by the same reference numerals. First, in FIGS. 1 (a) and 1 (b), reference numeral 17 denotes a metal-based printed wiring board, and a conductor pattern (not shown) formed on the upper surface thereof includes a diode (rectifying element) and a noise reducing capacitor. As a pair, four surface-mounted diodes 5 and 6 and four capacitors 7 and 8 are grouped and soldered and mounted. An external terminal 18 common to the cathode electrodes of the diodes 5 and 6 is provided at one end of the metal base printed wiring board 17 so as to surround the periphery of the diodes 5 and 6 which are further divided into four. Two terminal boards 19 serving as external terminals are mounted by soldering.

The terminal plate 19 is formed by forming a copper plate into a U-shape. An L-shaped leg 19a formed on the lower edge of the terminal plate 19 is formed on a metal base printed wiring board 17 in a self-standing manner, and is superposed on a conductor pattern. Each of the bead cores 9 is inserted and set one by one into a lead piece portion 19b formed so as to protrude upward from the upper edge of the terminal plate 19 in correspondence with the arrangement of the individual diodes 5 and 6, respectively. The circuit of the rectifier 1 (diode module) shown in FIG. 2 is configured. Note that the terminal board 19 is
By forming it in a letter shape, the wiring space can be reduced, and the external size of the metal base printed wiring board 17 can be reduced.

The heat radiator 10 is directly heat-conductively attached to the metal base side of the metal base printed wiring board 17 and the bus bar 12 is screwed to the external terminal 18. The bus bars 15 and 16 are soldered to the lead pieces 19b protruding from each other, thereby interconnecting the transformer (secondary coil) 2 of the switching power supply and the choke coil 3 as shown in FIG. ing.

[0017]

According to the present invention, the following effects can be obtained. 1) According to the configuration of claim 1, the heat generated by the rectifying element (diode) is efficiently transmitted to the radiator through the metal base printed wiring board having high heat conductivity and is dissipated, so that peripheral components such as a capacitor and a bead core, and The thermal effect on the transformer, choke coil, and the like of the switching power supply connected via the bus bar can be reduced, the mounting work of the capacitor is easy, and the wiring inductance is suppressed low, so that the noise suppressing effect can be sufficiently exhibited.

2) By adopting the configuration of claim 2, when the terminal plate is mounted on the metal base printed wiring board, soldering can be performed without the need for a holding jig or the like. 3) Further, by adopting the configuration of claim 3, the bead core made of ferrite, which is vulnerable to thermal stress, can be safely protected.

[Brief description of the drawings]

1A and 1B are assembly configuration diagrams of a diode module according to an embodiment of the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a side view.

FIG. 2 is a plan view showing a connection state between the diode module of FIG. 1 and a transformer and a choke coil of a switching power supply.

FIG. 3 is a circuit configuration diagram of a transformer secondary side of a switching power supply to which the present invention is applied;

FIG. 4 is an assembly configuration diagram of a conventional diode module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier part (diode module) 2 Transformer 3 Choke coil 5, 6 Diode 7, 8 Capacitor 9 Bead core 10 Heat radiator 12, 15, 16 Bus bar 17 Metal base printed wiring board 18 External terminal 19 Terminal board 19a Leg bus bar 19b Lead piece

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 25/18 H02M 3/28

Claims (3)

(57) [Claims] 1. An assembling structure of a rectifier connected to a transformer secondary side of a switching power supply circuit, wherein a surface mount type rectifier, a noise reducing capacitor, and an external terminal connected to a bus bar are metal as a heat sink. An assembling structure of a rectifier for a switching power supply, wherein the rectifier is arranged on a base printed wiring board, soldered and mounted on its conductor pattern, and a heat radiator is directly attached to the metal base printed wiring board. 2. An assembling structure according to claim 1, wherein the external connection terminal also serving as an interconnecting lead of the rectifying element is constituted by a self-standing terminal plate, and the leg of the terminal plate is a metal base printed wiring board. An assembly structure of a rectifier for a switching power supply, wherein the rectifier is connected by soldering. 3. The assembling structure according to claim 2, wherein a protruding lead piece portion which rises upward from a portion corresponding to each rectifying element to the terminal plate of the external connection terminal and is connected to the bus bar is formed. An assembling structure of a rectifying unit for a switching power supply, wherein a bead core for noise reduction is inserted and set here.