Power supply unit and image forming apparatus

Abstract

To provide a power supply and an image forming apparatus that can reduce the risk of fire when overvoltage is applied without compromising the design flexibility of the circuit layout. [Solution] A power supply device according to one embodiment of the present invention comprises a circuit board on which circuit components including an electrolytic capacitor having an explosion-proof valve that opens and releases gas when internal pressure rises and a protective element that protects the circuit from overvoltage are mounted, and a shielding member provided between the electrolytic capacitor and the protective element on the circuit board to shield the space between the electrolytic capacitor and the protective element.

Description

Technical Field

[0001] The present invention relates to a power supply device and an image forming apparatus including a circuit board on which an electrolytic capacitor having an explosion-proof valve is mounted.

Background Art

[0002] When a voltage exceeding the rated voltage is applied to an electrolytic capacitor, the pressure inside the electrolytic capacitor rises, and an explosion-proof valve is provided to prevent the case from bursting. Patent Document 1 describes a configuration including a fireproof case attached to an electrolytic capacitor having an explosion-proof valve.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, while maintaining the operable state of the explosion-proof valve, it is necessary for the case to cover the periphery of the explosion-proof valve, resulting in a large occupied space on the circuit board of the electrolytic capacitor including the case and reducing the design freedom of circuit layout.

[0005] In view of the above circumstances, an object of the present invention is to provide a power supply device and an image forming apparatus capable of reducing the possibility of ignition during overvoltage application without impairing the design freedom of circuit layout.

Means for Solving the Problems

[0006] To achieve the above object, a power supply device according to an aspect of the present invention includes a circuit board and a shielding member. The above circuit board includes circuit components that include an electrolytic capacitor having an explosion-proof valve that opens and releases gas when internal pressure rises, and a protective element that protects the circuit from overvoltage. The shielding member is provided between the electrolytic capacitor and the protective element on the circuit board, and shields the space between the electrolytic capacitor and the protective element.

[0007] Between the electrolytic capacitor with an explosion-proof valve mounted on the circuit board and the protective element, a shielding member is provided to shield the electrolytic capacitor and the protective element. This reduces the amount of sparks that may be applied to the protective element when it is damaged by the overvoltage, even if an overvoltage is applied and the explosion-proof valve of the electrolytic capacitor opens, releasing the gaseous electrolyte. Furthermore, since it is not necessary to cover the electrolytic capacitor with a dedicated case, the design flexibility of the circuit layout can be minimized.

[0008] The shielding member may include a first partition plate provided between the electrolytic capacitor and the protective element, parallel to the direction perpendicular to the circuit board, to shield the space between the electrolytic capacitor and the protective element, and a second partition plate connected to the end of the first partition plate opposite to the circuit board, and facing the electrolytic capacitor in a direction perpendicular to the circuit board.

[0009] The circuit board has a first region including the electrolytic capacitor and a second region different from the first region including the protection element. The shielding member may be a shield case that shields the first region from the second region.

[0010] The above-mentioned protective element may be a varistor. [Effects of the Invention]

[0011] As described above, the present invention provides a power supply device and an image forming apparatus that can reduce the possibility of ignition when an overvoltage is applied without impairing the design flexibility of the circuit layout. [Brief explanation of the drawing]

[0012] [Figure 1] This is a top view of a power supply device according to an embodiment of the present invention. [Figure 2] This figure shows the power supply device of the present invention, where (A) is a view from the X-axis direction and (B) is a view from the Y-axis direction. [Figure 3] This diagram shows the positional relationship between the electrolytic capacitor, the protective element, and the shielding member. (A) is a view from the Z-axis direction, and (B) is a view from the X-axis direction. [Figure 4] This diagram shows the explosion-proof valve when it is open; (A) is a view from the Z-axis direction, and (B) is a view from the X-axis direction. [Figure 5] This figure compares the power supply device of the present invention with a conventional power supply device, where (A) is a diagram showing the power supply device of the present invention, and (B) is a diagram showing a conventional power supply device. [Modes for carrying out the invention]

[0013] The embodiments of this technology will be described below with reference to the drawings.

[0014] Figure 1 is a top view of the power supply device 1 according to an embodiment of the present invention, and Figure 2 is a diagram showing the power supply device 1 of the present invention, where (A) is a view from the X-axis direction and (B) is a view from the Y-axis direction. Figure 3 is a diagram showing the positional relationship between the electrolytic capacitor 200, the protective element 100, and the shielding member 300, where (A) is a view from the Z-axis direction and (B) is a view from the X-axis direction. In each figure, the X-axis, Y-axis, and Z-axis represent three mutually orthogonal axes, but of course, the configuration is not limited to these directions.

[0015] (power supply) The power supply unit 1 according to this embodiment is built into an image forming apparatus (for example, a printer, a multifunction device, etc.) and supplies power from a commercial AC power source (not shown) as DC internal power to the internal devices of the image forming apparatus. The power supply unit 1 includes a circuit board 10 and a shielding member 20.

[0016] (Circuit board) The circuit board 10 includes a protection circuit 11A including a protection element 100, a rectification circuit 11B including an electrolytic capacitor 200, a voltage adjustment circuit 11C including a voltage control element and a switching element, input terminals 13A, output terminals 13B, and other circuit components (see FIGS. 1 and 3(A)).

[0017] Also, as will be described later, the circuit board 10 has a first region 12A including the electrolytic capacitor 200 and a second region 12B including a protection element 100 different from the first region 12A. When viewed from the Z-axis direction, the first region 12A and the second region 12B are formed so that the partitioned regions do not overlap each other. The sizes and shapes of the first region 12A and the second region 12B are not limited to those shown in FIG. 1.

[0018] As shown in FIG. 2(B), the protection element 100 is described as a varistor in this embodiment, but of course it is not limited to this, and for example, it may be a TSV diode. The protection element 100 has a function of suppressing the voltage rise due to an overvoltage when an overvoltage is applied (for example, a surge voltage). The protection element 100 (varistor) has a main body portion 102 in which semiconductor ceramics are sandwiched between two electrodes, and a lead portion 101 that electrically connects the main body portion 102 and the circuit board 10.

[0019] In addition to the protection element 100 described above, the circuit board 10 is equipped with a fuse and a noise filter that suppress the flow of overcurrent as a protection circuit.

[0020] The electrolytic capacitor 200 has a function of smoothing the voltage after being full-wave rectified by a bridge rectification circuit that full-wave rectifies the input voltage. As shown in FIGS. 1 and 2(A), the electrolytic capacitor 200 has a capacitor element (not shown) impregnated with an electrolytic solution, a terminal portion 200A provided on the capacitor element and electrically connected to the circuit board 10, and a case 200B that houses the capacitor element.

[0021] As shown in Figures 1 and 2(A), the case 200B has a bottomed cylindrical shape and includes a cylindrical side portion 201B formed along the Z-axis direction and a bottom portion 202B provided on the side portion 201B opposite to the circuit board 10 and facing the circuit board 10 (parallel to the XY plane).

[0022] The bottom portion 202B has an explosion-proof valve B, which is a recessed groove that is recessed toward the circuit board 10 in the center of the bottom portion 202B when viewed from the Z-axis direction. When a voltage exceeding the rated voltage (overvoltage) is applied to the electrolytic capacitor 200, the capacitor element heats up, the electrolyte gasifies, and the internal pressure of the case 200B rises. The explosion-proof valve B is provided to prevent the case 200B from rupturing due to this rise in internal pressure. In other words, the explosion-proof valve B has the function of opening when the internal pressure rises due to the application of an overvoltage to the electrolytic capacitor 200, and releasing the gas (gasified electrolyte) to the outside.

[0023] In this embodiment, the explosion-proof valve B is provided at the bottom portion 202B, but is not limited to this, and may also be provided at the side portion 201B. In this embodiment, the shape of the explosion-proof valve B was X-shaped, but is not limited to this, and may be Y-shaped, K-shaped, or the like.

[0024] The circuit board 10 is not limited to the configuration described above; it may also be equipped with transformers and other components.

[0025] (Shielding material) As shown in Figures 1 and 2, the shielding member 20 is a shielding case for attenuating electromagnetic waves and noise inside electronic equipment, and is provided between the electrolytic capacitor 200 and the protective element 100 on the circuit board 10. It includes a first partition plate 20A parallel to the Z-axis direction that shields the space between the electrolytic capacitor 200 and the protective element 100, a second partition plate 20B connected to the end of the first partition plate 20A opposite to the circuit board 10 and facing the electrolytic capacitor 200 and the circuit board 10 in a direction perpendicular to the circuit board 10 (Z-axis direction), a third partition plate (not shown) provided on the second partition plate 20B at a position facing the first partition plate 20A in the Y-axis direction, and a plurality of fourth partition plates 20C provided on the second partition plate 20B so as to face each other in the X-axis direction. In this embodiment, the fourth partition plate 20C has a plurality of insertion portions 201C through which insertion holes A for inserting fasteners are provided. A support base (not shown) is provided to support the shielding member 20 at a position opposite to the multiple insertion portions 201C in the Z-axis direction, thereby fixing the shielding member 20 to the support base. Of course, this is not the only option, and the shielding member 20 may also be fixed on the circuit board 10.

[0026] In this embodiment, the shielding member 20 is made of aluminum, copper, steel, etc., but is not limited to these materials.

[0027] As shown in Figure 1, the shielding member 20 is formed to cover the first region 12A described above, thereby shielding the first region 12A from the second region 12B described above. In other words, as shown in Figures 1 and 2, the electrolytic capacitor 200 is provided to be housed in the shielding member 20, and the protective element 100 is provided to be positioned outside the shielding member 20.

[0028] As shown in Figures 1 to 3, the first partition plate 20A has a shielding portion 21A that shields the space between the electrolytic capacitor 200 and the protective element 100. In other words, the shielding portion 21A divides the space W connecting the maximum outer shape (periphery) of the electrolytic capacitor 200 and the maximum outer shape (periphery) of the protective element 100 into multiple spaces (the electrolytic capacitor 200 side and the protective element 100 side). In other words, the first partition plate 20A is shaped so that the electrolytic capacitor 200 is not visible from the protective element 100 (and vice versa). Here, "not visible" means that when a straight line is drawn connecting any point on the maximum outer shape of the protective element 100 and any point on the maximum outer shape of the electrolytic capacitor 200, the shielding portion 21A is located on that straight line.

[0029] In other words, as shown in Figure 3(A), the shielding portion 21A is provided so as to block the lines L1 and L2, which connect the maximum outer dimensions of the electrolytic capacitor 200 and the maximum outer dimensions of the protection element 100 when viewed from the Z-axis direction (direction perpendicular to the circuit board 10), in the Y-axis direction (a part of the shielding portion 21A is located outside the space W formed in the Y-axis direction at a position overlapping with the shielding portion 21A when viewed from the Z-axis direction). Also, as shown in Figure 3(B), the shielding portion 21A is provided so as to block the lines L3 and L4, which connect the maximum outer dimensions of the electrolytic capacitor 200 and the maximum outer dimensions of the protection element 100 when viewed from the X-axis direction (a part of the shielding portion 21A is located outside the Z-axis direction of the space W formed in the Z-axis direction at a position overlapping with the shielding portion 21A when viewed from the X-axis direction).

[0030] In this embodiment, the maximum external dimensions of the electrolytic capacitor 200 are based on the external dimensions of the case 200B, but are not limited to this, and may include the terminal portion 200A. Also in this embodiment, the maximum external dimensions of the protective element 100 are based on the external dimensions of the main body portion 102, but are not limited to this, and may include the lead portion 101.

[0031] (Effects of the present invention) Figure 4 shows the explosion-proof valve B when it is open, with (A) being a view from the Z-axis direction and (B) being a view from the X-axis direction. Figure 5 is a comparison of the power supply device 1 of the present invention with a conventional power supply device 1', with (A) showing the power supply device 1 of the present invention and (B) showing the conventional power supply device 1'.

[0032] As shown in Figures 4 and 5(A), in this embodiment, a shielding member 20 (shielding portion 21A) is provided between the electrolytic capacitor 200 and the protection element 100 to shield the electrolytic capacitor 200 and the protection element 100. This makes it possible to suppress the application of sparks H, which are generated when the protection element 100 is damaged due to an overvoltage, to the gas G (gasified electrolyte) released when an overvoltage is applied and the explosion-proof valve B of the electrolytic capacitor 200 opens.

[0033] In other words, as shown in Figures 4(A) and (B), even if the explosion-proof valve B opens and gas G is released, the shielding member 20 that shields the electrolytic capacitor 200 and the protective element 100 prevents the gas G from flowing to the protective element 100. This is because, in the case of Figure 4(A), even if gas G is released, the space W connecting the maximum outer diameter (bottom 202B) of the electrolytic capacitor 200 and the maximum outer diameter of the protective element 100 is partitioned by the shielding member 20 in the Y-axis direction when viewed from the Z-axis direction, and in the case of Figure 4(B), even if gas G is released, the space W' connecting the explosion-proof valve B of the electrolytic capacitor 200 and the maximum outer diameter of the protective element 100 is partitioned by the shielding member 20 in the Z-axis direction when viewed from the X-axis direction, so that gas G cannot travel directly (by the shortest distance) to the protective element 100. As a result, the only way for gas G to reach the protective element 100 is to bypass the shielding member 20, so that sparks H are not applied to the gas G.

[0034] Furthermore, as shown in Figure 5(B), in the conventional power supply unit 1', the protection element 100 and the electrolytic capacitor 200 were housed within the shielding member 20'. Therefore, if an overvoltage was applied and gas G was released from the electrolytic capacitor 200, there was a risk of it being applied to sparks generated in the protection element 100. However, in this embodiment, the shielding member 20 has a second partition plate 20B which is connected to the end of the first partition plate 20A opposite to the circuit board 10 and faces the electrolytic capacitor 20 in the Z-axis direction.

[0035] As a result, as shown in Figure 5(A), it is possible to suppress the flow of gas G released from the bottom 202B to the protective element 100. In other words, the first partition plate 20A and the second partition plate 20B can block the flow of gas G released from the explosion-proof valve B of the electrolytic capacitor 200 to the protective element 100, thereby suppressing the application of sparks H to the gas G.

[0036] Furthermore, in this embodiment, since a shielding case is used for the shielding member 20, there is no need to manufacture a new cover to cover the electrolytic capacitor 200. Therefore, the possibility of ignition when an overvoltage is applied can be reduced at a lower cost without compromising the design flexibility of the circuit layout.

[0037] In this embodiment, the shielding member 20 was a shielding case, but of course, it is not limited to this. The configuration may also consist of only the shielding portion 21A being provided on the circuit board 10, or the electrolytic capacitor 200 may be covered with an L-shaped plate.

[0038] Furthermore, in this embodiment, although the protective element 100 is installed outside the shielding member 20 which acts as a shielding case, it is connected to the regulator mounted on the circuit board 10 via a noise filter, thus reducing the impact on EMC. [Explanation of Symbols]

[0039] 1...Power supply device 10... Circuit board 20... Shielding member 20A...First partition plate 20B...Second partition 100…Protective element 200… Electrolytic capacitors G...gas H...Spark

Claims

1. A circuit board equipped with circuit components including an electrolytic capacitor having an explosion-proof valve that opens and releases gas when internal pressure rises, and a protective element that protects the circuit from overvoltage, A shielding member is provided between the electrolytic capacitor and the protective element on the circuit board, and shields the space between the electrolytic capacitor and the protective element. A power supply device equipped with the following.

2. A power supply device according to claim 1, The shielding member includes a first partition plate provided between the electrolytic capacitor and the protective element, parallel to the circuit board in a direction perpendicular to the circuit board, to shield the space between the electrolytic capacitor and the protective element, and a second partition plate connected to the end of the first partition plate opposite to the circuit board, and facing the electrolytic capacitor in a direction perpendicular to the circuit board. power supply.

3. A power supply device according to claim 1, The circuit board has a first region including the electrolytic capacitor and a second region different from the first region including the protective element. The shielding member is a shield case that shields the first region from the second region. power supply.

4. A power supply device according to claim 1, The aforementioned protective element is a varistor. power supply.

5. An image forming apparatus comprising a power supply device according to any one of claims 1 to 4.

Images