JP2009254118A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter capable of reducing electromagnetic noise to be radiated. <P>SOLUTION: A DC-DC converter module 1a is equipped with a case plate 2 formed of a conductor; a transformer TR equipped with a secondary winding W1 and W2 having an intermediate tap T0, a first terminal T1, and a second terminal T2 and fixed to the case plate 2; an inductor L connected between the intermediate tap T0 and the case plate 2 and held between the case plate 2 and the transformer TR; a capacitor C equipped with a capacitor first terminal TC1 and a capacitor second terminal TC2 connected to the case plate 2; a diode D1 with one end connected to a first terminal T1 and the other end connected to the capacitor first terminal TC1; and a diode D2 with one end connected to a second terminal T2 and the other end connected to the capacitor first terminal TC1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter capable of reducing radiated electromagnetic noise.

  FIG. 12 shows a circuit diagram of the DC-DC converter 101 according to Patent Document 1. As shown in FIG. The DC-DC converter 101 includes a full-wave rectifier circuit and a choke input type smoothing circuit on the secondary side. The secondary winding N102 of the transformer T100 is divided by the center tap 102 into first and second windings N102a and N102b. First and second diodes D101 and D102 for constituting a full-wave rectifier circuit are connected to one end and the other end of the secondary winding N102, respectively. The smoothing circuit includes a choke coil L100 and a capacitor C100, and is configured as a choke input type. That is, the input end of the choke coil L100 is connected to the cathodes of the first and second diodes D101 and D102, and the smoothing capacitor C100 is connected between the output end of the choke coil L100 and the center tap 102. The output terminals 103 and 104 are connected to both terminals of the smoothing capacitor C100.

  When an upward voltage is induced in the secondary winding N102, a current loop is formed by the first winding N102a, the first diode D101, the choke coil L100, and the capacitor C100. When a downward voltage is induced in the secondary winding N102, a current loop is formed by the second winding N102b, the second diode D102, the choke coil L100, and the capacitor C100.

JP-A-7-123718

  Electromagnetic noise is radiated from the current loop of the DC-DC converter 101. When the area of the current loop is large, the radiated electromagnetic noise also increases. Therefore, in order to reduce the electromagnetic noise, it is necessary to reduce the area of the current loop. However, the conventional DC-DC converter 101 shown in FIG. 12 does not disclose an actual structure for reducing the area of the current loop when an actual DC-DC converter module is configured from a circuit diagram. It is.

  The present invention has been made to solve at least one of the problems of the prior art, and an object thereof is to provide a power conversion device capable of reducing radiated electromagnetic noise.

  To achieve the above object, a power converter according to claim 1 is a secondary winding having a conductor case plate, an intermediate terminal, a secondary winding first terminal, and a secondary winding second terminal. A transformer fixed to the case plate, connected between the intermediate terminal and the case plate, an inductor sandwiched between the case plate and the transformer, a capacitor element first terminal, and a capacitance connected to the case plate A capacitive element comprising an element second terminal, a first rectifier element having one end connected to the secondary winding first terminal and the other end connected to the capacitive element first terminal, and one end secondary to the secondary winding. And a second rectifier element having the other end connected to the capacitor element first terminal.

  In the power converter, a first current loop is formed that returns from the case plate to the case plate via the inductor, the transformer, the first rectifying element, and the capacitive element. In the power converter, a second current loop is formed from the case plate to the case plate 2 via the inductor, the transformer, the second rectifying element, and the capacitive element. Electromagnetic noise is radiated from these first and second current loops. In order to reduce electromagnetic noise, it is necessary to reduce the area of the current loop.

  The power converter according to claim 1 has a structure in which the inductor is sandwiched between the case plate and the transformer. With this structure, the inductor is positioned on the shortest path connecting the transformer and the case plate with a straight line. Therefore, the connection path between the transformer and the inductor can be minimized. Moreover, in the power converter device which concerns on Claim 1, it has a structure where an inductor is directly fixed on a case board. With this structure, the connection path between the inductor and the case plate can be minimized.

  As described above, since the path from the transformer TR to the case plate via the inductor L can be minimized, the area of the current loop can be reduced. As a result, radiated electromagnetic noise can be reduced.

  A power converter according to claim 2 is the power converter according to claim 1, wherein the case plate includes a recess, and the inductor is installed in the recess.

  By installing the inductor in the recess, the current loop existing in the vicinity of the inductor is covered with the case plate. Since the case plate is made of a conductor and provides a shielding effect, electromagnetic noise radiated from the current loop portion covered with the case plate is blocked. Thereby, electromagnetic noise radiated from the current loop can be reduced.

  A power converter according to claim 3 is the power converter according to claim 1 or 2, further comprising a conductor sandwiched between an inductor and a transformer.

  A conductor is provided between the inductor and the transformer. And since a shield effect is acquired by a conductor, the magnetic coupling of a transformer and an inductor can be made small. Thereby, the mutual influence between a transformer and an inductor can be made small.

  According to a fourth aspect of the present invention, there is provided the power conversion device according to any one of the first to third aspects, wherein the inductor includes a magnetic core for inductor having a substantially U-shaped cross section and a bus bar, and the magnetic for inductor. A through hole for the bus bar is formed by contacting the opening surface side of the core with the transformer magnetic core of the transformer.

  The bus bar passes through a through hole formed by the magnetic core for inductor and the magnetic core for transformer, so that the inductor is formed. That is, a part of the inductor is constituted by the transformer magnetic core. Thereby, in the inductor magnetic core, the core member on the surface in contact with the transformer magnetic core can be omitted, so that the inductor magnetic core can be reduced in size.

  The power conversion device according to claim 5 is the power conversion device according to claim 1, wherein the power conversion device has a wiring pattern formed on a metal substrate via an insulating layer, and is fixed to the case plate. It has a metal base substrate, and the capacitor element second terminal is fixed to the metal base substrate and is connected to the case plate through the metal base substrate.

  In order to reduce the area of the current loop, it is necessary to shorten the current path between the case plate and the case plate (the path of current returning from the case plate to the flow case plate). In the power conversion device according to the fifth aspect, the connection path from the capacitor element second terminal to the case plate is formed so as to penetrate the metal base substrate. Therefore, wiring for connecting to the case plate extending from the capacitor element second terminal to the end of the metal base substrate becomes unnecessary, and the current path between the case plate and the case plate can be shortened.

  ADVANTAGE OF THE INVENTION According to this invention, the power converter device which can reduce the electromagnetic noise radiated can be provided.

  Hereinafter, a first embodiment of a DC-DC converter according to the present invention will be described in detail based on FIGS. 1 to 7 with reference to the drawings. FIG. 1 shows a circuit diagram of a DC-DC converter 1 according to the first embodiment. FIG. 1 shows the secondary side of the transformer TR. Secondary windings W1 and W2 are connected to the secondary side of the transformer TR via an intermediate tap T0. One end of the inductor L is connected to the intermediate tap T0, and the other end is grounded. The anode terminal of the diode D1 is connected to the first terminal T1 of the secondary winding W1, and the cathode terminal is connected to the capacitor first terminal TC1. The anode terminal of the diode D2 is connected to the second terminal T2 of the secondary winding W2, and the cathode terminal is connected to the capacitor first terminal TC1. The capacitor first terminal TC1 is connected to the output terminal Tout, and the capacitor second terminal TC2 is grounded. In this way, the inductor L is directly grounded, thereby preventing the potential of the inductor L from floating. In addition, since the capacitor C is directly grounded, the potential of the capacitor C is prevented from floating.

  2 to 4 show a DC-DC converter module 1a corresponding to the circuit diagram of FIG. 2 is a top view of the DC-DC converter module 1a, FIG. 3 is a side view, and FIG. 4 is a front view from the direction of arrow A (see FIGS. 2 and 3). An inductor L, a transformer TR, and a metal base substrate 3 are fixed on a heat radiating case plate 2 made of a metal conductor. The case plate 2 acts as a ground. The shape of the case plate 2 is not limited to a plate shape, and may be various shapes such as a box shape. An inductor L is fixed on the case plate 2, and a transformer TR is fixed on the inductor L. Therefore, the inductor L is sandwiched between the case plate 2 and the transformer TR.

  As shown in FIG. 4, the inductor L has a configuration in which the bus bar 12 penetrates a substantially core-shaped magnetic core. The wiring 11 drawn from the intermediate tap T0 (not shown) inside the transformer TR through the lead-out port 16 and one end of the bus bar 12 drawn out from the inductor L through the lead-out port 17 are connected by the connecting portion 15. The As shown in FIGS. 2 and 3, the other end of the bus bar 12 is connected to the case plate 2 by a pin 14. Thus, by connecting the inductor L directly to the case plate 2, the potential of the inductor L can be prevented from floating, and the inductor L can be connected to the case plate 2 with low impedance.

  The metal base substrate 3 has a structure in which an insulating layer is formed on a metal substrate and wiring patterns 31 to 34 are formed on the insulating layer. The first terminal T1 of the wiring 21 drawn from the secondary winding W1 of the transformer TR is fixed to the wiring pattern 31 by soldering. The anode terminal TA1 of the diode D1 is fixed to the wiring pattern 31 by soldering. Similarly, the second terminal T2 of the wiring 22 drawn out from the secondary winding W2 of the transformer TR is fixed to the wiring pattern 32 by soldering. The anode terminal TA2 of the diode D2 is fixed to the wiring pattern 32 by soldering. Cathode terminals (not shown) formed on the back surfaces of the diodes D1 and D2 are fixed to the wiring pattern 33 by soldering. The capacitor first terminal TC1 of the capacitor C is fixed to the wiring pattern 33 by soldering. An output terminal Tout is formed so as to be connected to the wiring pattern 33. The capacitor second terminal TC2 of the capacitor C is fixed to the wiring pattern 34 by soldering. The wiring pattern 34 is connected to the case plate 2 by an earth point 24 that penetrates the metal base substrate 3.

The operation will be described. The electromagnetic noise (magnetic flux) radiated from the DC-DC converter is obtained by the following equation (1).
Φ = BS Formula (1)
Here, Φ is the magnetic flux, B is the magnetic flux density, and S is the area of the current loop. When electromagnetic noise is radiated, a voltage is induced in another electric wire, and a ripple component is generated in the other electric wire. Therefore, it is necessary to reduce the electromagnetic noise. In order to reduce the electromagnetic noise, it is understood that the magnetic flux Φ should be reduced in the equation (1), so that the area S of the current loop needs to be reduced.

  In the DC-DC converter 1 of FIG. 1, it is considered to reduce the area S of the current loop. In the DC-DC converter 1, when an upward voltage is induced in the secondary windings W1 and W2, from the ground to the ground via the inductor L, the intermediate tap T0, the secondary winding W1, the diode D1, and the capacitor C. A returning first current loop is formed. Further, in the DC-DC converter 1, when a downward voltage is induced in the secondary windings W1 and W2, the ground is passed from the ground through the inductor L, the intermediate tap T0, the secondary winding W2, the diode D2, and the capacitor C. A second current loop returning to is formed. The areas of these first and second current loops are the area S1 of the shaded portion shown in FIG. In order to reduce the area S1, the path from the transformer TR to the ground via the inductor L is shortened, the path from the transformer TR to the ground via the diode D1 and the capacitor C is shortened, and the diode from the transformer TR to the diode. It can be seen that at least one of shortening the path to the ground via D2 and the capacitor C needs to be performed.

  Next, in the DC-DC converter module 1a shown in FIGS. 6 and 7, it is considered to reduce the area S of the current loop. In the DC-DC converter module 1a, from the case plate 2, the pin 14, the inductor L (bus bar 12), the wiring 11, the transformer TR, the wiring 21, the wiring pattern 31, the diode D1, the wiring pattern 33, the capacitor C, the wiring pattern 34, A first current loop is formed that returns to the case plate 2 via the ground point 24. Further, in the DC-DC converter module 1a, from the case plate 2, the pin 14, the inductor L (bus bar 12), the wiring 11, the transformer TR, the wiring 22, the wiring pattern 32, the diode D2, the wiring pattern 33, the capacitor C, and the wiring pattern 34. A second current loop returning to the case plate 2 through the ground point 24 is formed. The areas of these first and second current loops are the hatched area S2 shown in FIGS.

  Here, in the DC-DC converter module 1a, attention is paid to a path from the transformer TR to the inductor L via the wiring 11. The DC-DC converter module 1a has a structure in which the inductor L is sandwiched between the case plate 2 and the transformer TR. With this structure, as shown in FIG. 4, the lead-out port 17 of the bus bar 12 of the inductor L is positioned on the shortest path P1 connecting the lead-out port 16 of the wiring 11 of the transformer TR and the case plate 2 with a straight line. . Therefore, the connection path between the transformer TR and the inductor L formed by the wiring 11 and the bus bar 12 can be minimized.

  In the DC-DC converter module 1a, attention is paid to a path from the inductor L to the case plate 2 (ground) via the pin 14. The DC-DC converter module 1 a has a structure in which the inductor L is directly fixed on the case plate 2. Therefore, with this structure, the connection path between the inductor L and the case plate 2 formed by the bus bar 12 and the pin 14 can be minimized.

  As described above, since the path from the transformer TR to the case plate 2 via the inductor L can be minimized, the area S2 of the current loop can be reduced.

  Further, in the DC-DC converter module 1a, since the inductor L is sandwiched between the case plate 2 and the transformer TR, the bus bar 12 is wired when viewed from the upper surface side of the DC-DC converter module 1a as shown in FIG. The structure may be located between the wiring 21 and the wiring 21. With this structure, in a current loop formed by a path from the transformer TR to the case plate 2 via the diode D1 and the capacitor C and a path from the transformer TR to the case plate 2 via the diode D2 and the capacitor C, A current path (bus bar 12, pin 14) between the inductor L and the case plate 2 can be included. As described above, the area S2 of the current loop can be reduced.

  The effect of the earth point 24 will be described. In order to reduce the area S2 of the current loop, it is necessary to shorten the current path between the ground and the ground (that is, between the case plate 2 and the case plate 2). In the DC-DC converter module 1 a according to the present invention, the wiring pattern 34 and the case plate 2 are connected through the metal base substrate 3 by the earth point 24. Then, the wiring 35 (dotted line portion) for extending from the wiring pattern 33 to the end of the metal base substrate 3 and connecting to the case plate 2 as shown in FIG. 6 becomes unnecessary. Therefore, since the current path between the case plate 2 and the case plate 2 can be shortened by the amount that the wiring 35 is unnecessary, the area S2 of the current loop can be reduced.

  As described above in detail, according to the DC-DC converter module 1a according to the first embodiment, the area S2 of the current loop can be reduced. Therefore, it is possible to reduce radiated electromagnetic noise. Further, by reducing the electromagnetic noise itself, it is possible to eliminate the need for a filter for eliminating the influence of the electromagnetic noise provided in the other electric wires, so that the cost can be reduced.

  A DC-DC converter module 1b according to a second embodiment of the present invention will be described with reference to FIGS. 8 is a top view, FIG. 9 is a side view taken along the line BB (see FIGS. 8 and 10), and FIG. 10 is a front view taken along the line CC (see FIGS. 8 and 9). A recess 40 is formed in the case plate 2b made of a metal conductor. The recess 40 is formed by, for example, pressing. An inductor L is installed and fixed in the recess 40. A metal plate 41 is fixed on the inductor L. The metal plate 41 is larger than the opening of the recess 40, and the recess 40 is closed by the metal plate 41. Further, the metal plate 41 is provided with a hole 42 through which the wiring 11 and the bus bar 12 are passed. A transformer TR is installed and fixed on the metal plate 41. Since other configurations are the same as those of the DC-DC converter module 1a according to the first embodiment, a detailed description thereof is omitted here.

  The operation will be described. In the DC-DC converter module 1b, the inductor L, the diode D1, the capacitor C, the first current loop returning from the case plate 2b to the case plate 2b, and the inductor L, the diode D2, the capacitor C, the case plate from the case plate 2b. A second current loop returning to 2b is formed. In the DC-DC converter module 1 b, the inductor L and the current loop existing in the vicinity of the inductor L are covered with the recess 40 and the metal plate 41. Since the case plate 2 and the metal plate 41 are made of a conductor and a shielding effect is obtained, electromagnetic noise radiated from the current loop portion covered with the case plate 2 and the metal plate 41 is blocked. Therefore, as the area S2b of the shaded portion shown in FIG. 9, the area of the current loop that generates electromagnetic noise is reduced, so that the electromagnetic noise radiated from the DC-DC converter module 1b can be reduced.

  Further, the DC-DC converter module 1b has a configuration in which the metal plate 41 is sandwiched between the inductor L and the transformer TR. Since the shield effect is obtained by the metal plate 41, the magnetic coupling between the transformer TR and the inductor L can be reduced. Thereby, the mutual influence between transformer TR-inductor L can be made small.

  As described in detail above, according to the DC-DC converter module 1b according to the second embodiment, it is possible to reduce radiated electromagnetic noise by shielding a part of the current loop. Further, by reducing the magnetic coupling between the transformer TR and the inductor L, the mutual influence between the transformer TR and the inductor L can be reduced.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications can be made without departing from the spirit of the present invention. In the DC-DC converter module 1a according to the first embodiment, the inductor L includes a magnetic core having a substantially square cross section. However, the present invention is not limited to this configuration. The inductor L may include an inductor magnetic core 51 having a substantially U-shaped cross section as shown in FIG. 11A is a side view of the transformer TR and the inductor L, and FIG. 11B is a front view. The inductor magnetic core 51 has a substantially U-shaped cross section. The transformer magnetic core 50 has a rectangular cross section. A through-hole 52 is formed by joining the U-shaped opening surface side of the inductor magnetic core 51 to the center of the lower surface of the transformer magnetic core 50. The inductor L is configured by the bus bar 12 passing through the through hole 52. That is, a part of the inductor L is configured by the lower surface portion of the transformer magnetic core 50.

  Thereby, in the inductor magnetic core 51, the core member on the surface joined to the transformer magnetic core 50 can be omitted, so that the height H of the inductor magnetic core 51 can be reduced. Therefore, the inductor magnetic core 51 can be reduced in size.

  The intermediate tap T0 is an example of an intermediate terminal, the first terminal T1 is an example of a secondary winding first terminal, the second terminal T2 is an example of a secondary winding second terminal, and the capacitor first terminal TC1 is a capacitance element first. An example of one terminal, a capacitor second terminal TC2 is an example of a capacitor element second terminal, a capacitor C is an example of a capacitor element, a diode D1 is an example of a first rectifier element, a diode D2 is an example of a second rectifier element, and a metal plate 41 Is an example of a conductor.

Circuit diagram of DC-DC converter 1 (part 1) Top view of DC-DC converter module 1a (No. 1) Side view of DC-DC converter module 1a (No. 1) Front view of DC-DC converter module 1a (No. 1) Circuit diagram of DC-DC converter 1 (part 2) Top view of DC-DC converter module 1a (2) Side view of DC-DC converter module 1a (part 2) Top view of DC-DC converter module 1b Side view of DC-DC converter module 1b Front view of DC-DC converter module 1b The figure which shows the magnetic core 51 for inductors Circuit diagram of conventional DC-DC converter 101

Explanation of symbols

2 Case plate 3 Metal base substrate 12 Bus bar 31, 32, 33, 34 Wiring pattern 40 Recess 41 Metal plate 50 Magnetic core for transformer 51 Magnetic core for inductor 52 Through hole T0 Middle tap T1 First terminal T2 Second terminals W1, W2 Secondary winding TR Transformer L Inductor TC1 Capacitor first terminal TC2 Capacitor second terminal C Capacitors D1, D2 Diode

Claims (5)

A conductor case plate;
A transformer comprising a secondary winding having an intermediate terminal, a secondary winding first terminal and a secondary winding second terminal, and fixed to the case plate;
An inductor connected between the intermediate terminal and the case plate, and sandwiched between the case plate and the transformer;
A capacitive element comprising a capacitive element first terminal and a capacitive element second terminal connected to the case plate;
A first rectifier element having one end connected to the secondary winding first terminal and the other end connected to the capacitor element first terminal;
And a second rectifying element having one end connected to the second terminal of the secondary winding and the other end connected to the first terminal of the capacitive element. The case plate includes a recess,
The power converter according to claim 1, wherein the inductor is installed in the recess.   The power converter according to claim 1, further comprising a conductor sandwiched between the inductor and the transformer. The inductor includes a magnetic core for an inductor having a substantially U-shaped cross section and a bus bar,
4. The power converter according to claim 1, wherein a through hole for the bus bar is formed by contacting an opening surface side of the inductor magnetic core with a transformer magnetic core of the transformer. 5. A wiring pattern formed on the metal substrate through an insulating layer, and comprising a metal base substrate fixed to the case plate,
5. The power conversion device according to claim 1, wherein the capacitor element second terminal is fixed to the metal base substrate and is connected to the case plate through the metal base substrate. 6. .

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