Switching power supply device

Abstract

Provided is a switching power supply device capable of easily suppressing the generation of a noise voltage due to the leakage magnetic flux from a power conversion circuit acting on a lead of a lead-equipped component. The leading end portions of the leads (22a, 22b) of the capacitor element (18) are connected to the printed wiring board (12), and between the leads (22a, 22b), a magnetic flux passage space (24) of a leakage magnetic flux (phi) released from the power conversion circuit (14) is formed. The electromagnetic shielding member (28) is provided with a shielding part (30) having a metal frame body (30a) and a through region (30b) on the inner side of the metal frame body (30a). The shield portion (30) is positioned so that the central axis (40) of the through region (30b) passes through the magnetic flux passing space (24). The leakage magnetic flux [phi] acts on the shield portion (30), a magnetic field in a direction that cancels the leakage magnetic flux [phi] is generated by a current flowing in the circumferential direction of the frame body (30a), and the magnetic flux density of the leakage magnetic flux [phi] passing through the magnetic flux passing space (24) is suppressed.

Description

Technical Field

[0001] The present invention relates to a switching power supply device having a shield portion for suppressing noise caused by leakage magnetic flux released by switching operation. Background Art

[0002] Conventionally, for example, as disclosed in Patent Document 1 proposed by the applicant of the present application, there is a switching power supply device having a structure in which a pair of connection patterns connecting a smoothing capacitor on the output side to an output terminal are three-dimensionally intersected. Usually, the loop formed by the smoothing capacitor and the connection pattern becomes larger, and the leakage magnetic flux from the magnetic parts interlinks in the loop to flow a large induced current, generating a large noise voltage in the connection pattern, etc., which has an adverse effect on an external load, etc. However, according to the structure of the switching power supply device, the above-mentioned induced current can be reduced, and the generation of the noise voltage can be suppressed.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Utility Model Registration No. 3142501 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The structure of Patent Document 1 is a very excellent structure in suppressing the generation of noise voltage due to leakage magnetic flux. However, when the lead wires of the smoothing capacitor are long, the effect of suppressing the generation of noise voltage in the lead wires cannot be expected.

[0008] For example, Figure 6 The conventional switching power supply device 10 shown has a power conversion circuit 14 mounted on a printed wiring board 12, and a capacitor element 18 as a component with leads is mounted near a magnetic component 16 as a component in the power conversion circuit 14. The capacitor element 18 has a cylindrical component body 20 arranged horizontally, and a pair of leads 22a and 22b extend from the end of the component body 20 toward the printed wiring board 12, and the front end portions of the leads 22a and 22b are connected to the wiring pattern of the printed wiring board. The leads 22a and 22b are long in order to mount circuit components (not shown) below the component body 20. By making the leads 22a and 22b long, the component body 20 does not contact the circuit components below. Therefore, a loop is formed by the leads 22a and 22b that stand up from the printed wiring board 12. Hereinafter, the space between the leads 22a and 22b is referred to as the magnetic flux passing space 24.

[0009] The power conversion circuit 14 is a circuit that performs power conversion by switching. The magnetic component 16 is, for example, a switching transformer or a power inductor, and releases leakage magnetic flux when performing switching. Furthermore, the leakage flux A part of the magnetic flux that passes through the capacitor element 18 passes through the space 24, and an induced current flows through the leads 22a and 22b, generating a large noise voltage in the leads 22a and 22b, which may adversely affect the external load, etc. Even if the structure of Patent Document 1 is used, this problem cannot be solved.

[0010] in addition, Figure 6 The capacitor element 18 shown is an aluminum electrolytic capacitor for smoothing, etc., but in the case of a small capacitor element (ceramic capacitor, film capacitor) used for a control circuit or a resistor element with a very small resistance value, the above-mentioned noise voltage is generated when the lead wire is long, and the control circuit may malfunction.

[0011] The present invention has been made in view of the above-mentioned background art, and an object of the present invention is to provide a switching power supply device that can easily suppress the leakage magnetic flux from a power conversion circuit from acting on the leads of a component with leads and generating a noise voltage.

[0012] Means used to solve problems

[0013] The present invention is a switching power supply device, comprising: a printed wiring board; a power conversion circuit mounted on the printed wiring board and performing power conversion through switching action; a part in the power conversion circuit or a part other than the power conversion circuit, namely a part with leads having a pair of leads extending in the same direction from the end of the part body; and an electromagnetic shielding component having a shielding portion, wherein the shielding portion is formed in a ring shape, the inner side of which is a through area through which magnetic lines of force can pass, and the shielding portion is formed by a frame of an electrically closed conductor, and the front end portion of the lead of the part with leads is aligned with the wiring pattern of the printed wiring board. The connection is formed by standing up from the printed wiring board, and a magnetic flux passing space is formed between the pair of leads for leakage magnetic flux released from the power conversion circuit. When the electromagnetic shielding component is mounted on the printed wiring board, the shielding portion is positioned so that the leakage magnetic flux can pass through the penetration area, and the leakage magnetic flux passing through the penetration area passes through the magnetic flux passing space. The leakage magnetic flux acts on the shielding portion, and a magnetic field in a direction that cancels out the leakage magnetic flux is generated by flowing a current in the circumferential direction of the frame, and the magnetic flux density of the leakage magnetic flux passing through the magnetic flux passing space is suppressed.

[0014] The shielding portion is positioned so that a plane formed by the frame and the magnetic flux passing space face each other in parallel, and a central axis that is orthogonal to the plane and passes through the center of the penetration region passes through the magnetic flux passing space.

[0015] At least a portion of the frame of the electromagnetic shielding component is formed of a metal plate. Furthermore, the frame of the electromagnetic shielding component may be integrally provided with a mounting portion formed of a metal plate, inserted into the through hole of the printed wiring board and fixed. In addition, the electromagnetic shielding component may be integrally provided with a heat dissipation portion at the end of the shielding portion for dissipating heat from circuit components.

[0016] The frame of the electromagnetic shielding component is partially formed by the wiring pattern of the printed wiring board. Alternatively, the frame of the electromagnetic shielding component may be formed by the wiring pattern of an auxiliary printed wiring board that is separate from the printed wiring board. The auxiliary printed wiring board may also be integrally provided with a mounting portion that is inserted into the through hole of the printed wiring board and fixed. The lead-wired part is, for example, a capacitor element.

[0017] Effects of the Invention

[0018] Since the switching power supply device of the present invention is provided with an electromagnetic shielding component having a shielding portion with a unique structure, when leakage magnetic flux acts on the shielding portion, a magnetic field in a direction that cancels out the leakage magnetic flux is generated by flowing a current in the circumferential direction of the electromagnetic shielding component. As a result, the magnetic flux density of the leakage magnetic flux passing through the magnetic flux passing space is effectively suppressed, and the noise voltage generated in the lead wire can be effectively suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a perspective view showing one embodiment of the switching power supply device of the present invention.

[0020] Figure 2 Yes means Figure 1 Stereoscopic views (a) to (c) of three specific examples of electromagnetic shielding components.

[0021] Figure 3 This is a circuit diagram showing an internal circuit of a prototype of the switching power supply device according to the embodiment and an external connection circuit for an effect confirmation experiment conducted using the prototype.

[0022] Figure 4 The graphs are graphs showing the results of the effect confirmation experiment, graphs (a) to (c) showing the measurement results of the frequency characteristics of the noise terminal voltage of Comparative Examples A and B and the prototype, and graphs (d) to (f) comparing the voltage levels at specific frequencies.

[0023] Figure 5 (a) is a front view showing a modification of the electromagnetic shielding member, and (b) is a perspective view showing another modification.

[0024] Figure 6It is a perspective view showing one form of a conventional switching power supply device. DETAILED DESCRIPTION

[0025] The following is based on Figure 1 to Figure 4 Here, the same components as those of the conventional switching power supply device 10 are denoted by the same reference numerals, and description thereof will be omitted.

[0026] The switching power supply device 26 of this embodiment is as follows Figure 1 As shown, the electromagnetic shielding member 28 is additionally installed to the above-mentioned switching power supply device 10, and the other structures are the same as those of the switching power supply device 10.

[0027] Specifically, the electromagnetic shielding member 28 can be made into Figure 2 (a)~ Figure 2 (c) is a structure like that of (c). Figure 2 The electromagnetic shielding component 28 (1) shown in (a) is the simplest structure that can be made by punching a flat metal plate, and has a shielding part 30 composed of a flat frame 30a closed in a ring shape and a through area 30b on the inner side of the frame 30a. At the lower end of the shielding part 30, an installation part 32 is integrally protruded and inserted into a conductive hole of the printed wiring board 12 and fixed thereto.

[0028] Figure 2 The electromagnetic shielding component 28 (2) shown in (b) is a structure in which a flat metal plate is punched and then the side ends are bent, and has a shielding portion 30 composed of a frame 30a that is closed in a ring shape and slightly bent in an L shape, and a through area 30b inside the frame 30a. At the lower end of the shielding portion 30, a mounting portion 32 that is inserted into a via hole of the printed wiring board 12 and fixed is integrally protruded.

[0029] Figure 2 The electromagnetic shielding member 28 (3) shown in (c) is a structure in which the side end of the shielding portion 30 of the electromagnetic shielding member 28 (2) is extended in a U shape to provide a heat dissipation portion 34. The heat dissipation portion 34 clamps the portion of the heat-generating component 36 (or the heat-generating circuit module) covered with the silicon heat dissipation cap 38 from both sides, and plays a role in dissipating the heat of the heat-generating component 36 (or the heat-generating circuit module).

[0030] The electromagnetic shielding member 28 is as follows Figure 1 As shown, it is mounted on the printed wiring board 12, the shielding portion 30 is arranged near the leads 22a, 22b of the capacitor element 18, the plane formed by the frame 30a and the magnetic flux passing space 24 are parallel to each other and are positioned in such a way that the central axis 40, which is an axis orthogonal to the above-mentioned plane and passes through the center of the through-area 30b, passes through the approximate center of the magnetic flux passing space 24.

[0031] The electromagnetic shielding member 28 functions to prevent leakage magnetic flux from the magnetic component 16. When the shield 30 passes through the through region 30b inside the frame 30a, an eddy current flows in the circumferential direction of the frame 30a. The magnetic field in the direction of canceling the magnetic field, the magnetic flux facing the frame 30a passes through the leakage magnetic flux of the space 24 The magnetic flux density is suppressed, and the noise voltage generated in the leads 22a and 22b can be effectively suppressed.

[0032] In order to confirm the effect of the electromagnetic shielding member 28, the inventors produced a prototype 26x of the switching power supply device 26 of the present invention and conducted a test using Figure 3 The measurement circuit shown is an experiment for measuring the noise level (noise terminal voltage) fed back from the prototype 26x to the input power supply 42 side.

[0033] The internal circuit of the prototype 26x is configured as follows: the AC input voltage output from the input power supply 42 is received by the noise filter 44, rectified and smoothed by the rectifier element 46 and the capacitor element 18, and input to the power conversion circuit 14 (DC-DC converter) that performs switching operations. The magnetic component 16 and the capacitor element 18 are leakage magnetic flux released from the magnetic component 16. A portion of the magnetic flux that easily passes through the capacitor element 18 passes through the space 24. Figure 1 As shown, the electromagnetic shield member 28 is arranged near the lead wires 22a and 22b of the capacitor element 24. The shield portion 30 is positioned so that the central axis 40 of the penetrating region 30b passes through the substantially center of the magnetic flux passing space 24.

[0034] The connection between the prototype 26x of the switching power supply device 26 and the measuring circuit is as follows: Figure 3 As shown, a simulated power supply network 48 for impedance matching is inserted between the input power supply 42 and the input terminal of the prototype 26x, and a load 50 consuming a predetermined amount of power is connected to the output terminal of the prototype 26x. Next, a spectrum analyzer 52 is connected to the simulated power supply network 48 to measure the frequency characteristics of the noise terminal voltage.

[0035] For comparison, the electromagnetic shielding component 28 of the prototype 26x was changed to produce a switching power supply device in which the shielding portion 30 was removed from the electromagnetic shielding component 28 [Comparison Example (A)], and a switching power supply device in which the through-area 30b of the shielding portion 30 was eliminated and formed into a simple flat plate [Comparison Example (B)], and the same measurements were performed.

[0036] Figure 4 (a)~ Figure 4(c) is the frequency characteristic of the noise terminal voltage measured by the spectrum analyzer 52 for the comparative example (A), the comparative example (B), and the prototype 26x. Figure 4 The sample 26x shown in (c) has the best characteristics. Furthermore, if we observe the peak voltage level of the noise terminal voltage near 210kHz, we can see that Figure 4 As shown in (d), the voltage level of the comparative example (A) is 72.1dBμV, the comparative example (B) is 65.7dBμV, and the voltage level of the prototype 26x (C) is 54.9dBμV. In addition, if we observe the voltage level of the peak value of the noise terminal voltage near 650kHz, we can see that Figure 4 As shown in (e), the voltage level of the comparative example (A) is 62.6dBμV, the voltage level of the comparative example (B) is 54.8dBμV, and the voltage level of the prototype 26x (C) is 44.9dBμV. Furthermore, if we observe the voltage level of the peak value of the noise terminal voltage near 2MHz, we can see that Figure 4 As shown in (f), the voltage level of the comparative example (A) is 61.6 dBμV, the voltage level of the comparative example (B) is 52.7 dBμV, and the voltage level of the prototype 26x (C) is 47.7 dBμV. The voltage level of the prototype 26x (C) is the lowest.

[0037] Comparison of the measurement results of Comparative Example (A) and Comparative Example (B) shows that a certain shielding effect can be obtained simply by providing the shielding portion 30 composed of a simple plate. This is considered to be because an eddy current flows through the shielding portion 30, generating a leakage magnetic flux that passes through the space 24 and the magnetic flux that is about to pass through the capacitor element 18. The magnetic field in the direction of cancellation is used to suppress the leakage magnetic flux passing through the magnetic flux passing space 24 to a certain extent. The magnetic flux density is increased and the noise terminal voltage is reduced.

[0038] Comparing the measurement results of the comparative example (B) and the trial product 26x, it can be seen that the shielding effect is further improved by providing the through area 30b on the shielding part 30. Since the comparative example (B) does not have the through area 30b, the eddy current flowing in the shielding part 30 is small, and it is difficult to effectively generate a magnetic field in a canceling direction. In contrast, the trial product 26x provides the through area 30b in the shielding part 30, and the central axis 40 of the through area 30b is positioned in such a way that the magnetic flux passing through the capacitor element 18 passes through the space 24, so the eddy current is restricted to flow along the circumferential direction of the frame 30a, so that the leakage magnetic flux is generated in the shielding part 30. The magnetic field in the direction of cancelling the leakage magnetic flux through the space 24 The magnetic flux density is effectively suppressed. As a result, it can be expected that the noise terminal voltage is greatly reduced.

[0039] In addition, the trial product 26x Figure 1 As shown, from the one closer to the magnetic part 16, the order of arrangement is the magnetic part 16, the shielding part 30, and the magnetic flux passing space 24. However, when the order is changed to the magnetic part 16, the magnetic flux passing space 24, and the shielding part 30, approximately the same effect can be obtained by the same principle as above.

[0040] As described above, the switching power supply device 26 includes the electromagnetic shield member 28 having the shield portion 30 having a unique structure. The shield portion 30 is composed of a metal frame 30a and a through region 30b inside the metal frame 30a. Acting on the shield 30, an eddy current flows in the circumferential direction of the frame 30a, generating a leakage magnetic flux The magnetic field in the direction of canceling each other can effectively act on the magnetic flux passing space 24. As a result, the leakage magnetic flux passing through the magnetic flux passing space 24 The magnetic flux density is effectively suppressed, and the problem of noise voltage generated in the leads 22a and 22b can be easily solved.

[0041] In addition, the switching power supply device of the present invention is not limited to the above-mentioned embodiment. For example, Figure 2 (a)~ Figure 2 The structures of the electromagnetic shielding members 28 ( 1 ) to 28 ( 3 ) shown in (c) are only preferred examples and can be appropriately changed in accordance with the structure of an actual power supply device.

[0042] The shielding part of the electromagnetic shielding component only needs to be composed of a frame of a conductor electrically closed in a ring shape and a through-area inside thereof, and is not limited to the structure of the above-mentioned shielding part 30. For example, the shape of the frame and the through-area can also be changed to a shape other than a square. In addition, the "through-area" of the present invention includes not only a space where no physical components exist as in the above-mentioned embodiment, but also an area where there are insulating components through which magnetic lines of force can pass. This is because insulating components are equivalent to air for electromagnetic waves and have almost no effect on the performance of the shielding part.

[0043] In addition, electromagnetic shielding components can be made into Figure 5 The electromagnetic shielding component 28 (4) shown in (a) is configured as the structure. The shielding portion 30 of the electromagnetic shielding component 28 (4) is provided with a U-shaped metal component 54 partially open in the circumferential direction, and the two ends of the U-shaped metal component 54 are connected to the wiring pattern 56 of the printed wiring board 12 to be short-circuited. In this embodiment, the frame 30a is formed by the U-shaped metal component 54 and the wiring pattern 56, and the through area 30b is formed inside. Even if the structure is changed to such a structure, substantially the same effect can be obtained.

[0044] In addition, electromagnetic shielding components can also be made Figure 5 The electromagnetic shielding component 28 (5) is structured as shown in (b). The electromagnetic shielding component 28 (5) is formed using an auxiliary printed wiring board 58 that is separate from the printed wiring board 12. The substrate 58a of the printed wiring board 58 is an insulating material such as glass epoxy resin or phenolic paper. In addition, the shielding portion 30 is formed by a wiring pattern arranged in a ring shape to form a frame 30a, and the inner side of the wiring pattern becomes a through area 30b. In the case of the electromagnetic shielding component 28 (5), the through area 30b is formed by the substrate 58a, but since the substrate 58a is an insulating material, the magnetic lines of force can pass through, and there is almost no effect on the shielding performance. Even if it is changed to such a structure, it can also obtain a roughly equivalent effect.

[0045] In addition, the material of the frame of the shielding part can be any conductive material such as metal, and can be appropriately selected from aluminum, copper, brass, phosphor bronze, iron, etc., which are widely used as shielding boxes, etc., and can obtain roughly the same effect. In addition, the type and use of the lead-wired parts as the object of electromagnetic shielding are not particularly limited. In addition to the above-mentioned capacitor elements for smoothing, small capacitor elements used in control circuits, resistor elements with very small resistance values, etc. can also be used as the object. In particular, when the main impedance (impedance of the part other than the lead wire) of the high-frequency band is very low, excellent effects can be obtained.

[0046] Description of symbols

[0047] 10, 26 Switching power supply device

[0048] 12 Printed wiring board

[0049] 14 Power conversion circuit

[0050] 18 Capacitor elements (parts with leads)

[0051] 20 parts body

[0052] 22a, 22b lead wire

[0053] 24 Magnetic flux through space

[0054] 26x Prototype

[0055] 28, 28(1) to 28(5) Electromagnetic shielding components

[0056] 30 Shielding

[0057] 30a Frame

[0058] 30b Through area

[0059] 32 Installation

[0060] 34 Heat dissipation

[0061] 36 Heating parts

[0062] 38 Heatsink Cap

[0063] 40 Center axis

[0064] 42 Input power

[0065] 44 Noise Filter

[0066] 46 Rectifier element

[0067] 48 Analog Power Circuit Network

[0068] 50 Load

[0069] 52 Spectrum Analyzer

[0070] 54U type metal parts (frame)

[0071] 56 Wiring pattern (frame)

[0072] 58 Auxiliary printed wiring board

[0073] 58a Substrate

[0074] Leakage flux

Claims

1. A switching power supply device, characterized in that: The invention comprises: a printed wiring board; a power conversion circuit mounted on the printed wiring board and performing power conversion by switching action; a part in the power conversion circuit or a part other than the power conversion circuit, namely a part with leads having a pair of leads extending in the same direction from the end of the part body; and an electromagnetic shielding component having a shielding portion, the shielding portion being formed in a ring shape, the inner side of which is a through area through which magnetic lines of force can pass, and being formed by a frame of an electrically closed conductive body, The lead of the leaded component has its tip portion connected to the wiring pattern of the printed wiring board and rises from the printed wiring board. A magnetic flux passage space for leakage magnetic flux released from the power conversion circuit is provided between the pair of leads. In a state where the electromagnetic shielding member is mounted on the printed wiring board, the shielding portion is positioned so that the leakage magnetic flux can pass through the penetration region and the leakage magnetic flux that has passed through the penetration region passes through the magnetic flux passing space. The leakage magnetic flux acts on the shield portion, and a current flows in the circumferential direction of the frame, thereby generating a magnetic field in a direction that cancels out the leakage magnetic flux, and the magnetic flux density of the leakage magnetic flux passing through the magnetic flux passing space is suppressed.

2. The switching power supply device according to claim 1, characterized in that: The shielding portion is positioned so that a plane formed by the frame and the magnetic flux passing space face each other in parallel, and a central axis that is orthogonal to the plane and passes through the center of the penetration region passes through the magnetic flux passing space.

3. The switching power supply device according to claim 1 or 2, characterized in that: At least a part of the frame of the electromagnetic shielding member is formed of a metal plate.

4. The switching power supply device according to claim 3, characterized in that: The frame of the electromagnetic shielding member is provided with an integrally protruding mounting portion which is formed of a metal plate and is inserted into and fixed to the via hole of the printed wiring board.

5. The switching power supply device according to claim 4, characterized in that: The electromagnetic shield member is integrally provided with a heat dissipation portion for dissipating heat from circuit components at an end portion of the shield portion.

6. The switching power supply device according to claim 1 or 2, characterized in that: The frame of the electromagnetic shielding member is partially formed by a wiring pattern of the printed wiring board.

7. The switching power supply device according to claim 1 or 2, characterized in that: The frame of the electromagnetic shielding member is formed by a wiring pattern of an auxiliary printed wiring board that is separate from the printed wiring board.

8. The switching power supply device according to claim 7, characterized in that: The auxiliary printed wiring board is integrally provided with a mounting portion protruding therefrom and inserted into a via hole of the printed wiring board to be fixed thereto.

9. The switching power supply device according to claim 1 or 2, characterized in that: The above-mentioned part with leads is a capacitor element.

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