Power supply device

Abstract

To provide a power supply device having an insulated switching power supply circuit having high conversion efficiency while reducing noise.SOLUTION: A power supply device 1 includes: an insulated switching power supply circuit 100 that includes a primary circuit 110 including a primary coil CL1 of a transformer TR and a secondary circuit 120 including a secondary coil CL2 of the transformer TR, and converts a power supplied to the primary circuit 110 and outputs the converted power from the secondary circuit 120; a first shield 150 that covers the primary circuit 110 and the secondary circuit 120 and is formed of metal; and a housing 200 formed of an insulating material that accommodates the insulated switching power supply circuit 100. The first shield 150 is connected to a secondary-side ground line GL2 which is a ground line of the secondary circuit 120, and is provided between the insulated switching power supply circuit 100 and the housing 200.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device, for example, a power supply device having a flyback type isolated switching power supply circuit. [Background technology]

[0002] Conventionally, a flyback type isolated switching power supply circuit (hereinafter also referred to as a "flyback converter") using a transformer has been known as an isolated switching power supply circuit that converts an input voltage to a desired voltage and outputs it. For example, Patent Document 1 discloses an active clamp type flyback converter (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-037073 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that flyback converters generate noise mainly due to the on / off operation of the switching elements. To prevent electromagnetic interference (EMI) caused by noise emitted by flyback converters, many flyback converters have a snubber circuit. However, the snubber circuit has a resistance component, and a current flowing through the snubber circuit causes a power loss, which leads to a decrease in the conversion efficiency of the flyback converter. To improve the conversion efficiency of a flyback converter, it may be possible to omit a snubber circuit within the flyback converter circuit, but if a snubber circuit is not provided, it is difficult to achieve a noise level that satisfies EMI regulations.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to achieve high conversion efficiency while reducing noise in a power supply device. [Means for solving the problem]

[0006] A power supply device according to a representative embodiment of the present invention comprises an isolated switching power supply circuit including a primary circuit including a primary coil of a transformer and a secondary circuit including a secondary coil of the transformer, converting power supplied to the primary circuit and outputting it from the secondary circuit, a first shield formed of metal and covering the primary circuit and the secondary circuit, and a housing formed of an insulating material that houses the isolated switching power supply circuit, wherein the first shield is connected to a secondary ground wire that is the ground wire of the secondary circuit, and is provided between the isolated switching power supply circuit and the housing. [Effects of the Invention]

[0007] According to the present invention, it is possible to achieve high conversion efficiency while reducing noise in a power supply device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of an isolated switching power supply circuit of a power supply device according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing the appearance of a power supply device having an isolated switching power supply circuit according to an embodiment of the present invention; [Figure 3] 2 is a diagram showing the entire first shield of the power supply device according to the embodiment of the present invention. FIG. [Figure 4] 1 is a diagram showing the appearance of an isolated switching power supply circuit according to an embodiment of the present invention, formed on a circuit board; [Figure 5] 5A and 5B are diagrams showing an example of a method of connecting a first shield and a damper circuit of a power supply device according to an embodiment of the present invention. [Figure 6]6 is an enlarged view showing a connection point between the first shield and the damper circuit in FIG. 5. [Figure 7] 1 is a diagram showing an example of the configuration of a transformer core of an isolated switching power supply circuit according to an embodiment of the present invention; [Figure 8] 8 is a diagram showing the configuration of a second shield formed to cover the transformer core in FIG. 7. FIG. [Figure 9] 1 is a diagram showing an example of the configuration of a ground wire of a transformer core according to an embodiment of the present invention; [Figure 10] 10 is a diagram showing a configuration in which a toroidal core is connected to the ground wire of the transformer core in FIG. 9. FIG. [Figure 11] 1A and 1B are diagrams illustrating an example of a method for connecting a transformer to a circuit board according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1. Overview of the embodiment First, a typical embodiment of the invention disclosed in this application will be outlined. In the following description, for example, reference numerals in the drawings corresponding to components of the invention are written in parentheses.

[0010] [1] A power supply device (1) according to a representative embodiment of the present invention includes an isolated switching power supply circuit (100) that includes a primary circuit (110) including a primary coil (CL1) of a transformer (TR) and a secondary circuit (120) including a secondary coil (CL2) of the transformer (TR), converting power supplied to the primary circuit (110) and outputting it from the secondary circuit (120), a first shield (150) formed of metal that covers the periphery of the primary circuit (110) and the secondary circuit (120), and a housing (200) formed of an insulating material that houses the isolated switching power supply circuit (100), wherein the first shield (150) is connected to a secondary ground line (GL2) that is the ground line of the secondary circuit (120), and is provided between the isolated switching power supply circuit (100) and the housing (200).

[0011] [2] The power supply device (1) described in [1] above may further include a damper circuit (170) including a resistance component (Rd) and a capacitance component (Cd), and the first shield (150) may be connected to the secondary side ground line (GL2) via the damper circuit (170).

[0012] [3] The power supply device (1) described in [1] to [2] above may further include a second shield (160) made of metal that covers at least a part of the first core (CR1) of the transformer (TR) and at least a part of the second core (CR2) of the transformer (TR), and the second shield (160) may be connected to a primary side ground line (GL1) that is a ground line of the primary side circuit (110).

[0013] [4] The power supply device (1) described in [3] above may further include a toroidal core (TOC), and the second shield (160) may be connected to the primary side ground wire (GL1) via the toroidal core (TOC).

[0014] [5] In the power supply device (1) described in [1] to [4] above, the primary side circuit (110) may include an active clamp circuit (140) connected in parallel to the primary side coil (CL1), and the active clamp circuit (140) may include a capacitor (Cac) and a transistor (Tac) connected in series to the capacitor (Cac).

[0015] [6] In the power supply device (1) described in any one of [1] to [5] above, the first shield (150) and the damper circuit (170) may be connected to each other by a rod member (Sd) made of metal.

[0016] [7] The power supply device (1) described in any one of [1] to [6] above may further include a rectifier circuit (130) that rectifies an input AC voltage and inputs the rectified AC voltage to the primary side circuit (110).

[0017] 2. Specific examples of embodiments Specific examples of embodiments of the present invention will be described below with reference to the drawings. In the following description, components common to each embodiment will be given the same reference numerals, and repeated description will be omitted. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from the actual situation. The drawings may also include portions with different dimensional relationships and ratios.

[0018] FIG. 1 is a diagram showing the configuration of an isolated switching power supply circuit of a power supply device according to an embodiment of the present invention.

[0019] The power supply device 1 according to this embodiment is a so-called AC adapter. Specifically, the power supply device 1 includes an isolated switching power supply circuit 100. The isolated switching power supply circuit 100 is a circuit that converts power supplied to the primary side of a transformer TR and outputs the converted power from the secondary side of the transformer TR. As shown in Fig. 1, the isolated switching power supply circuit 100 has a primary side circuit 110 including a primary side coil CL1 of the transformer TR and a secondary side circuit 120 including a secondary side coil CL2 of the transformer TR. The primary side circuit 110 and the secondary side circuit 120 form a DC / DC converter that converts an input DC voltage into a desired DC voltage and outputs it. For example, the primary side circuit 110 and the secondary side circuit 120 form a flyback converter. The isolated switching power supply circuit 100 further includes a rectifier circuit 130. The rectifier circuit 130 rectifies the AC voltage input to the first primary terminal PT1 and the second primary terminal PT2 and inputs the rectified voltage to the primary circuit 110. In other words, the isolated switching power supply circuit 100 constitutes an AC / DC converter that rectifies the AC voltage input to the first primary terminal PT1 and the second primary terminal PT2, converts the rectified voltage into a predetermined DC voltage, and outputs it from the secondary positive terminal STP and the secondary negative terminal STN.

[0020] As described above, the rectifier circuit 130 rectifies the AC voltage input to the first primary-side terminal PT1 and the second primary-side terminal PT2 and inputs the rectified voltage to the primary-side circuit 110. The rectifier circuit 130 includes, for example, a diode bridge circuit Dr in which multiple diodes are bridge-connected, and a capacitor Cr as a so-called smoothing capacitance. The diode bridge circuit Dr has a known circuit configuration, for example, a full-wave rectification type or a half-wave rectification type. In this embodiment, an electrolytic capacitor is used as the capacitor Cr, but this is not limiting. The rectifier circuit 130 rectifies the AC voltage input to the first primary-side terminal PT1 and the second primary-side terminal PT2 using the diode bridge circuit Dr, smooths the rectified voltage using the capacitor Cr, and outputs the rectified voltage between the primary power line PL1 and the primary ground line GL1.

[0021] The primary circuit 110 is formed between a primary power supply line PL1 and a primary ground line GL1. Specifically, as shown in Fig. 1, the primary circuit 110 includes, for example, an active clamp circuit 140, a transistor T1, a primary control circuit CC1, a first core CR1 of a transformer TR, a second core CR2 of the transformer TR, and a primary coil CL1 of the transformer TR.

[0022] The transformer TR includes a primary coil CL1 and a secondary coil CL2. The transformer TR is, for example, an insulating transformer. The transformer TR is not limited to an insulating transformer.

[0023] The primary coil CL1 is connected between the primary power supply line PL1 and the primary ground line GL1. Specifically, one end of the primary coil CL1 is connected to the primary power supply line PL1, and the other end of the primary coil CL1 is connected to the primary ground line GL1 via the transistor T1.

[0024] The transistor T1 is turned on / off based on a control signal S1 from the primary control circuit CC1. For example, the drain electrode of the transistor T1 is connected to the other end of the primary coil CL1. The source electrode of the transistor T1 is connected to the primary ground line GL1. The control signal S1 is input to the gate electrode of the transistor T1 from the primary control circuit CC1.

[0025] In this embodiment, the transistor T1 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), but this is not limiting and other transistors may be used depending on the required switching frequency, withstand voltage specifications, etc. For example, the transistor T1 may be an IGBT (Insulated Gate Bipolar Transistor), a bipolar transistor, or a GaNFET (Gallium Nitride Field Effect Transistor). However, from the viewpoints of low loss and switching speed, it is most preferable to use a GaNFET.

[0026] The active clamp circuit 140 is a circuit that absorbs energy generated from the primary coil CL1 when the transistor T1 is turned off. The active clamp circuit 140 is connected in parallel with the primary coil CL1. For example, the active clamp circuit 140 includes a transistor Tac and a capacitor Cac. In this embodiment, the transistor Tac is a MOSFET, but this is not limiting and other transistors may be used depending on the required switching frequency, withstand voltage specifications, etc. For example, the transistor Tac may be an IGBT, a bipolar transistor, or a GaNFET (Gallium Nitride Field Effect Transistor). However, from the viewpoints of low loss and switching speed, it is most preferable to use a GaNFET.

[0027] For example, one end of a capacitor Cac is connected to a primary power supply line PL1. The drain electrode of a transistor Tac is connected to the other end of the capacitor Cac. The source electrode of the transistor Tac is connected to a primary ground line GL1 via a transistor T1. A control signal Sac is input to the gate electrode of the transistor Tac from a primary control circuit CC1.

[0028] In this embodiment, the capacitor Cac and the transistor Tac are connected in series, but this is not limiting.

[0029] The primary-side control circuit CC1 is a circuit that controls the driving of the transistor T1 and the transistor Tac. The primary-side control circuit CC1 is realized, for example, by an integrated circuit (IC) or a large-scale integrated circuit (LSI). The primary-side control circuit CC1 switches the transistor T1 and the transistor Tac by inputting a control signal S1 to the gate electrode of the transistor T1 and a control signal Sac to the gate electrode of the transistor Tac. For example, the primary-side control circuit CC1 generates the control signals S1 and Sac so that the transistor Tac is in the off state when the transistor T1 is in the on state, and the transistor Tac is in the on state when the transistor T1 is in the off state.

[0030] When the primary control circuit CC1 switches on the transistor T1, energy is transferred to the secondary coil CL2 by electromagnetic induction in the transformer TR. At this time, by switching on the transistor Tac complementary to the transistor T1, the transistor T1 is turned off, and the back electromotive force generated by the primary coil CL1 can be absorbed by the capacitor Cac.

[0031] The secondary circuit 120 is formed between a secondary power supply line PL2 connected to the secondary positive terminal STP and a secondary ground line GL2 connected to the secondary negative terminal STN. Specifically, the secondary circuit 120 includes a capacitor C2, a transistor T2, a secondary control circuit CC2, and a secondary coil CL2 of a transformer TR.

[0032] The secondary coil CL2 is connected between the secondary power supply line PL2 and the secondary ground line GL2. For example, one end of the secondary coil CL2 is connected to the secondary power supply line PL2, and the other end of the secondary coil CL2 is connected to the secondary ground line GL2 via the transistor T2.

[0033] The transistor T2 is turned on / off based on a control signal S2 from the secondary control circuit CC2. For example, the drain electrode of the transistor T2 is connected to the other end of the secondary coil CL2. The source electrode of the transistor T2 is connected to the secondary ground line GL2. The control signal S2 is input to the gate electrode of the transistor T2 from the secondary control circuit CC2.

[0034] In this embodiment, the transistor T2 is a MOSFET, but this is not limiting and other transistors may be used depending on the required switching frequency, withstand voltage specifications, etc. For example, the transistor T2 may be an IGBT, a bipolar transistor, or a GaNFET (Gallium Nitride Field Effect Transistor). However, from the viewpoints of low loss and switching speed, it is most preferable to use a MOSFET.

[0035] The capacitor C2 is an element that stores energy generated from the secondary coil CL2 when the transistor T2 is turned off. The capacitor C2 is, for example, an electrolytic capacitor. For example, one end of the capacitor C2 is connected to the secondary power supply line PL2, and the other end of the capacitor C2 is connected to the secondary ground line GL2.

[0036] The secondary-side control circuit CC2 is a circuit that controls the driving of the transistor T2 and is configured, for example, by an integrated circuit (IC) or a large-scale integrated circuit (LSI). The input voltage input to the primary side of the transformer TR induces a voltage on the secondary side of the transformer TR that corresponds to the turns ratio of the primary coil CL1 and the secondary coil CL2. The secondary control circuit CC2 generates a control signal S2 and inputs it to the gate electrode of the transistor T2 to switch the transistor T2. This on / off operation of the transistor T2 causes energy generated by the primary coil CL1 to be stored in the capacitor C2. At this time, the secondary control circuit CC2 generates the control signal S2 so that the voltage of the secondary power line PL2 becomes a predetermined value. For example, the secondary control circuit CC2 generates the control signal S2 so that the voltage obtained by dividing the voltage of the secondary power line PL2 matches a reference voltage. It is preferable that the voltage for driving the secondary control circuit CC2 be supplied from the output voltage of the secondary circuit 120 (secondary power supply line PL2) rather than from the auxiliary winding of the transformer TR.

[0037] The isolated switching power supply circuit 100 having the rectifier circuit 130, primary side circuit 110, and secondary side circuit 120 described above converts the AC voltage input to the primary side first terminal PT1 and the primary side second terminal PT2 into a DC voltage according to the turn ratio of the primary side coil CL1 and the secondary side coil CL2, and outputs it from the secondary side positive terminal STP and the secondary side negative terminal STN.

[0038] The power supply device 1 according to this embodiment includes, in addition to the above-described isolated switching power supply circuit 100, a first shield 150, a second shield 160, and a damper circuit 170. The first shield 150, the second shield 160, and the damper circuit 170 will be described in detail below with reference to Figures 2 to 11. In this embodiment, for the sake of convenience, the surface on which the transformer TR of the isolated switching power supply circuit 100 is placed is defined as the XZ plane, and the directions of the XYZ axes based on the XZ plane are defined as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.

[0039] FIG. 2 is a diagram showing the appearance of a power supply device having an isolated switching power supply circuit according to an embodiment. FIG. 3 is a diagram showing the appearance of the first shield of the power supply device 1 according to the embodiment. FIG. 4 is a diagram showing the appearance of an isolated switching power supply circuit formed on a circuit board. FIG. 5 is a diagram showing an example of a method of connecting the first shield and the damper circuit in the power supply device. FIG. 6 is an enlarged view showing the connection point between the first shield and the damper circuit in FIG.

[0040] As shown in Figures 2 to 6, the power supply device 1 is realized by accommodating an isolated switching power supply circuit 100, a first shield 150, a second shield 160, and a damper circuit 170 within a housing 200. The housing 200 is made of an insulating material, such as polycarbonate. As shown in Fig. 4, the isolated switching power supply circuit 100 is realized by mounting the above-mentioned transformer TR, transistor T1, etc. on a circuit board such as a printed circuit board.

[0041] The first shield 150 is made of metal (e.g., a metal mainly composed of copper or aluminum). As shown in FIGS. 3 and 5 , the first shield 150 is formed to cover the periphery of the primary side circuit 110 and the secondary side circuit 120. Note that the first shield 150 does not need to completely cover the periphery of the primary side circuit 110 and the secondary side circuit 120 as long as it can achieve the purpose of reducing the noise level that reaches the surroundings due to noise generated by the isolated switching power supply circuit 100. For example, the first shield 150 may have holes at any position to facilitate connection to other components. For example, the first shield 150 has holes formed around the primary side first terminal PT1 and the primary side second terminal PT2 to improve the ease of handling of the primary side first terminal PT1 and the primary side second terminal PT2.

[0042] The first shield 150 is provided between the isolated switching power supply circuit 100 mounted on a circuit board and the housing 200. Specifically, as shown in Figures 2 and 3, the first shield 150 is formed to cover the periphery of the isolated switching power supply circuit 100 including the primary side circuit 110 and the secondary side circuit 120, and the periphery of the first shield 150 is covered by the housing 200 made of an insulating material.

[0043] The first shield 150 is connected to a secondary ground wire GL2, which is a ground wire of the secondary circuit 120. Preferably, the first shield 150 is connected to the secondary ground wire GL2 via a damper circuit 170. Specifically, as shown in FIGS. 5 and 6, the first shield 150 is connected to the secondary ground wire GL2 of the secondary circuit 120 via the damper circuit 170.

[0044] 6, the damper circuit 170 includes a resistor Rd and a capacitor Cd. The damper circuit 170 is connected in series to the first shield 150. Specifically, one end of the capacitor Cd is connected to the first shield 150, and the other end is connected to one end of the resistor Rd. The other end of the resistor Rd is connected to the secondary-side ground line GL2.

[0045] The first shield 150 and the damper circuit 170 are connected to each other by a rod member Sd made of metal. For example, when the main surface of a circuit board on which the damper circuit 170 is formed and one surface of the first shield 150 are spaced apart from each other, the rod member Sd is provided to connect the main surface of the circuit board and the one surface of the first shield 150 to each other. Specifically, as shown in FIG. 6 , one end of the rod member Sd is connected to a wiring pattern connected to one end of a capacitor Cd on the main surface of the circuit board, and the other end of the rod member Sd is connected to the one surface of the first shield 150. For example, the rod member Sd and the first shield 150 are connected by soldering.

[0046] 6 shows a case in which the rod member Sd is arranged so that the direction in which the rod member Sd extends is approximately perpendicular to the main surface of the circuit board and the one surface of the first shield 150, but this is not limiting. For example, the rod member Sd may be arranged obliquely with respect to the main surface of the circuit board and the first shield 150. Furthermore, the rod member Sd is not limited to being linear, and a portion of the rod member Sd may be bent. The length of the rod member Sd in the extension direction can be any length as long as there is a distance that ensures insulation between the first shield 150 and the damper circuit 170.

[0047] Next, the second shield 160 will be described in detail with reference to FIGS.

[0048] FIG. 7 is a diagram showing an example of the configuration of a transformer core of an isolated switching power supply circuit according to an embodiment of the present invention. FIG. 8 is a diagram showing the configuration of a second shield formed so as to cover the transformer core in FIG. FIG. 9 is a diagram showing an example of the configuration of the ground wire of the transformer core according to the embodiment of the present invention. FIG. 10 is a diagram showing a configuration in which a toroidal core is connected to the ground line of the transformer core in FIG. FIG. 11 is a diagram showing an example of a method for connecting the transformer according to the embodiment of the present invention to a circuit board.

[0049] The second shield 160 is made of metal (e.g., a metal containing copper or aluminum as a main component). The second shield 160 is formed so as to cover at least a portion of the first core CR1 of the transformer TR and at least a portion of the second core CR2 of the transformer TR. Specifically, as shown in FIGS. 7 and 8, the second shield 160 is formed so as to cover at least a portion of the first core CR1 of the transformer TR and at least a portion of the second core CR2 of the transformer TR in order to reduce the level of noise generated from the transformer TR that reaches the surroundings. However, as long as the second shield 160 can achieve the purpose of reducing the level of noise generated from the transformer TR that reaches the surroundings, it is not necessary for the second shield 160 to completely cover the periphery of the first core CR1 and the second core CR2.

[0050] For example, as shown in FIGS. 8 to 11, consider a case where the transformer TR has a structure in which a first core CR1 and a second core CR2 are stacked in the Y-axis direction, and is mounted with the negative surface of the transformer TR in contact with a circuit board. In this case, as shown in FIGS. 8 to 11, a second shield 160 is formed to cover at least a portion of the surface of the transformer TR opposite the circuit board (the positive side of the Y-axis direction). The second shield 160 is also formed to cover at least a portion of the surface of the transformer TR parallel to the Y-axis direction. In this case, as shown in FIGS. 8 to 11, the positive surface of the transformer TR in the Y-axis direction and the surface of the transformer TR parallel to the Y-axis direction may be continuously covered by the second shield 160 made of a single metal thin film. Note that the second shield 160 may be formed to cover the entire transformer TR.

[0051] The second shield 160 is connected to the primary ground line GL1, which is the ground line of the primary circuit 110. Preferably, the second shield 160 is connected to the primary ground line GL1 via a toroidal core TOC. Here, the toroidal core TOC is made of a ferromagnetic material and is formed in a cylindrical shape. For example, the toroidal core TOC is formed in an annular shape. 10 and 11, for example, a wiring PGW connecting the second shield 160 and the primary ground wire GL1 is inserted into the toroidal core TOC, thereby connecting the second shield 160 to the primary ground wire GL1 via the toroidal core TOC. The wiring PGW may be wound around the toroidal core TOC. Since the first core CR1 and the second core CR2 of the transformer TR are included in the primary circuit 110, the secondary coil CL2 of the transformer TR included in the secondary circuit 120 is formed as a flying wire using a three-phase insulated wire to ensure an insulation distance from the primary circuit 110.

[0052] As described above, the power supply device 1 according to this embodiment includes an isolated switching power supply circuit 100 that includes a primary side circuit 110 including a primary side coil CL1 of a transformer TR and a secondary side circuit 120 including a secondary side coil CL2 of the transformer TR, and that converts power supplied to the primary side circuit 110 and outputs it from the secondary side circuit 120, a first shield 150 that covers the periphery of the primary side circuit 110 and the secondary side circuit 120 and is made of metal, and a housing 200 that is made of an insulating material and that houses the isolated switching power supply circuit 100, and the first shield 150 is connected to a secondary side ground wire GL2 that is the ground wire of the secondary side circuit 120, and is provided between the isolated switching power supply circuit 100 and the housing 200.

[0053] This allows the first shield 150 to reduce noise generated in the primary side circuit 110 and the secondary side circuit 120. Furthermore, by connecting the first shield 150 to the secondary side ground wire GL2, noise can be further reduced. Furthermore, this allows noise to be suppressed without providing a snubber circuit that includes a resistive component, making it possible to further reduce power loss compared to power supply devices that have conventional snubber circuits. Therefore, the power supply device 1 according to this embodiment can achieve high conversion efficiency while reducing noise.

[0054] The power supply device 1 further includes a damper circuit 170 including a resistance component Rd and a capacitance component Cd, and the first shield 150 is connected to the secondary-side ground line GL2 via the damper circuit 170.

[0055] This allows noise generated from the isolated switching power supply circuit 100 and transmitted to the first shield 150 to be attenuated by the resistor Rd and capacitor Cd of the damper circuit 170. In other words, by providing the damper circuit 170, the effect of reducing noise generated from the isolated switching power supply circuit 100 can be further enhanced.

[0056] The power supply device 1 also includes a second shield 160 made of metal that covers at least a portion of the first core CR1 of the transformer TR and at least a portion of the second core CR2 of the transformer TR, and the second shield 160 is connected to the primary side ground wire GL1, which is the ground wire of the primary side circuit 110.

[0057] This allows the second shield 160 to reduce noise generated due to magnetostriction and magnetic flux leakage of the transformer TR. In other words, the provision of the second shield 160 reduces noise generated in the transformer TR. Connecting the second shield 160 to the primary-side grounding wire GL1 has the effect of reducing magnetic flux leakage at the mating surface between the first core CR1 of the transformer TR and the second core CR2 of the transformer TR. Furthermore, the potential of the shield is stabilized and does not float, thereby reducing radiated noise.

[0058] The power supply device 1 further includes a toroidal core TOC, and the second shield 160 is connected to the primary ground line GL1 via the toroidal core TOC.

[0059] This allows the toroidal core TOC to attenuate noise generated from the transformer TR and transmitted to the second shield 160. In other words, the inclusion of the toroidal core TOC can further enhance the effect of reducing noise generated from the isolated switched-mode power supply circuit 100.

[0060] In addition, the power supply device 1 has a primary side circuit 110 that includes an active clamp circuit 140 connected in parallel to the primary side coil CL1, and the active clamp circuit 140 includes a capacitor Cac and a transistor Tac that is connected in series with the capacitor Cac.

[0061] In this configuration, by switching the transistor Tac complementary to the transistor T1, the back electromotive force generated by the primary coil CL1 can be absorbed by the capacitor Cac when the transistor T1 is turned off. Furthermore, the energy absorbed by the capacitor Cac is released to the secondary side via the transformer TR, thereby achieving high conversion efficiency.

[0062] In the power supply device 1, the first shield 150 and the damper circuit 170 are connected to each other by a rod member Sd made of metal.

[0063] This allows the length of the rod member Sd in the extension direction to be set arbitrarily within a range that allows for a distance that ensures insulation between the first shield 150 and the damper circuit 170. In other words, by connecting the first shield 150 and the damper circuit 170 to each other by the rod member Sd, the degree of freedom in designing the isolated switching power supply circuit 100 and the power supply device 1 can be increased.

[0064] The power supply device 1 further includes a rectifier circuit 130 that rectifies the input AC voltage and inputs the rectified AC voltage to the primary side circuit 110.

[0065] This makes it possible to realize an AC adapter that has high conversion efficiency while reducing noise.

[0066] <<Extension of Embodiment>> The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0067] For example, although the above embodiments have been described with reference to a flyback-type isolated switching power supply circuit, the present invention is not limited to this and can also be applied to a forward-type isolated switching power supply circuit.

[0068] Furthermore, in the above embodiment, the case where the isolated switching power supply circuit 100 is an AC / DC converter has been exemplified, but the present invention is not limited to this. For example, the isolated switching power supply circuit 100 may function as a DC / DC converter without providing the rectifier circuit 130. That is, the isolated switching power supply circuit 100 may be a DC / DC converter that converts a DC voltage input to the primary-side first terminal PT1 and the primary-side second terminal PT2 into a DC voltage of a predetermined magnitude using the primary-side circuit 110 and the secondary-side circuit 120, and outputs the DC voltage from the secondary-side positive terminal STP and the secondary-side negative terminal STN. [Explanation of symbols]

[0069] 1...power supply device, 100...isolated switching power supply circuit, 110...primary side circuit, 120...secondary side circuit, 130...rectifier circuit, 140...active clamp circuit, 150...first shield, 160...second shield, 170...damper circuit, 200...casing, Cac...capacitor, Cr...capacitor, C2...capacitor, Cd...capacitor, CC1...primary side control circuit, CC2...secondary side control circuit, CL1...primary side coil, CL2...secondary side coil, CR1...first core, CR2...second core, Dr...rectifier circuit Diode, GL1...primary ground wire, GL2...secondary ground wire, PGND...primary ground point, PGW...wiring, PL1...primary power line, PL2...secondary power line, PT1...primary terminal 1, PT2...primary terminal 2, Rd...resistor, S1...control signal, S2...control signal, Sac...control signal, Sd...rod member, SGND...secondary ground point, STP...secondary positive terminal, STN...secondary negative terminal, Tac...transistor, T1...transistor, T2...transistor, TOC...toroidal core, TR...transformer

Claims

1. an isolated switching power supply circuit including a primary circuit including a primary coil of a transformer and a secondary circuit including a secondary coil of the transformer, which converts power supplied to the primary circuit and outputs the converted power from the secondary circuit; a first shield that covers the primary circuit and the secondary circuit and is made of metal; a housing made of an insulating material that houses the isolated switching power supply circuit, The first shield is connected to a secondary-side ground line, which is a ground line of the secondary-side circuit, and is provided between the isolated switching power supply circuit and the housing. power supply.

2. 2. The power supply device according to claim 1, further comprising a damper circuit including a resistance component and a capacitance component; The first shield is connected to the secondary-side ground line via the damper circuit. power supply.

3. 3. The power supply device according to claim 2, a second shield that covers at least a portion of the first core of the transformer and at least a portion of the second core of the transformer and is made of metal; The second shield is connected to a primary side ground line, which is a ground line of the primary side circuit. power supply.

4. 4. The power supply device according to claim 3, Further comprising a toroidal core, The second shield is connected to the primary ground line via the toroidal core. power supply.

5. 2. The power supply device according to claim 1, the primary circuit includes an active clamp circuit connected in parallel to the primary coil; The active clamp circuit includes a capacitor and a transistor connected in series with the capacitor. power supply.

6. 3. The power supply device according to claim 2, The first shield and the damper circuit are connected to each other by a rod member made of metal. power supply.

7. 7. The power supply device according to claim 1, The inverter further includes a rectifier circuit that rectifies the input AC voltage and inputs the rectified AC voltage to the primary side circuit. power supply.

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