Power tube radiator for reducing common-mode current of switching power supply

Abstract

The invention provides a power tube radiator for reducing common-mode current of a switching power supply, which comprises a power tube radiator body, a power tube and a ferrite magnetic core, radiating fins are uniformly distributed on the end face of one side of the power tube radiator body, an accommodating cavity is arranged on the other side of the power tube radiator body, and the ferrite magnetic core is arranged in the accommodating cavity. The ferrite magnetic core is arranged in the power tube radiator body, the end face of the inner side of the ferrite magnetic core is tightly attached to the power tube radiator body, the end face of the outer side of the ferrite magnetic core is attached to the power tube, and the power tube is connected with the power tube radiator body through a connecting piece. And the heat dissipation capability is enhanced.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to a power tube heat sink for reducing the common-mode current of a switching power supply. Background Art

[0002] Electromagnetic compatibility (EMC) is the ability of devices and systems to operate properly in the expected electromagnetic environment. Electronic devices should not interfere with other devices, nor should they be affected by electromagnetic radiation from other devices. Electromagnetic interference (EMI) is a key issue in switching power supply design.

[0003] The EMI of switching power supplies includes conducted interference and radiated interference. Radiation and conduction are distinguished by the propagation mode of electromagnetic fields. Conducted EMI is caused by the physical contact of conductors, while radiated EMI, on the contrary, is caused by induction (no physical contact of conductors). Conducted emissions can be further classified into common-mode conducted interference and differential-mode conducted interference. Differential-mode conducted interference occurs between two conductors, and common-mode propagation occurs between a set of conductors and the ground. Generally speaking, the power switching semiconductors (MOS-FET / IGBT) of switching power supplies generate a lot of heat. Installing a heat sink is one of the effective measures to solve the heat dissipation of the power supply to keep the power semiconductor within a given temperature range. Since the heat sink is usually installed on the surface of the switching tube, parasitic capacitance is formed between the semiconductor housing and the heat sink. Due to these capacitors, common-mode currents are generated in the switching power supply circuit, so common-mode electromagnetic interference is usually the result of parasitic effects.

[0004] In the switching power supply circuit, the parasitic capacitance of the heat sink provides a path for the common mode current. If the heat sink is grounded, the parasitic capacitance between the metal tube shell of the power switch tube and the heat sink provides a path for the common mode current, and the common mode current returning to the AC power ground line will increase, thereby aggravating the conducted EMI; on the contrary, the ungrounded heat sink, although it cuts off the path of the common mode current and reduces the conducted emission of the common mode current, at the same time the high-frequency switching current will flow to the heat sink, making the heat sink a voltage-excited antenna, increasing the radiated EMI; many studies have shown that the electromagnetic compatibility of the grounded heat sink is better than that of the ungrounded heat sink. Therefore, the heat sink of the power switch tube will always generate electromagnetic interference and may violate the electromagnetic compatibility (EMC) standard. Therefore, the connection between the heat sink and the switch tube is a very important design link involving common mode current noise, radiated interference and cooling effect.

[0005] The harm of conducted interference of switching power supply is generally greater than that of radiated interference, and conducted interference should be suppressed first. At present, the improvement of electromagnetic compatibility mainly adopts signal modulation to reduce conducted EMI or design EMI filters to suppress interference, but these measures increase R&D costs and bring certain complexity to the system. Compared with signal modulation and filter design, there is another method with simpler principle. Using the principle of metal electrostatic shielding, a metal shielding layer (such as copper wire mesh) is added between the switch tube and the radiator. To prevent short circuit, an insulating material with good thermal conductivity is attached to the side of the shielding layer facing the switch tube. In this way, the parasitic capacitance of the switching device to the ground can be reduced, thereby increasing the parasitic impedance of the common mode current propagation path and reducing electromagnetic interference. Compared with the existing technology, this method is simple in principle, does not require additional R&D costs, and can well achieve the purpose of reducing conducted EMI. However, the method of adding a metal shielding layer will also bring greater heat transfer resistance. It is mostly used for water-cooled radiators with better heat dissipation capacity. It may not meet the heat dissipation requirements when used on the fin-type switching power supply power tube radiator. The reduced efficiency or failure of the power tube when the temperature is too high will directly affect the operation of the power supply.

[0006] Ferrite cores are very effective in suppressing common-mode conducted interference. They are currently widely used in power lines and signal lines. Usually, ferrite cores are directly placed on the wires between the EMI source and the EMI receiver. When current passes through, magnetic induction is generated in the ferrite core, and the ferrite core acts as an inductor. Since the loss of ferrite materials at high frequencies is large, high-frequency currents can be filtered in ferrites, effectively absorbing noise. Ferrite cores are used in the design of power switch tube heat sinks to reduce the conducted interference of the heat sink. This new design has lower heat transfer resistance than the shielded design, achieving the effect of both heat dissipation of the power tube heat sink and low electromagnetic interference. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a power tube heat sink for reducing the common mode current of a switching power supply in view of the above-mentioned problems, which can reduce the electromagnetic interference caused by the common mode current in the switching tube heat sink and will not have a negative impact on heat dissipation.

[0008] The embodiment of the present application is implemented as follows:

[0009] An embodiment of the present application provides a power tube heat sink for reducing the common mode current of a switching power supply, characterized in that it includes a power tube heat sink body, a power tube and a ferrite core, wherein heat dissipation fins are evenly distributed on one end surface of the power tube heat sink body, and an accommodating cavity is provided on the other side, the ferrite core is arranged in the accommodating cavity, the inner end surface of the ferrite core is in close contact with the power heat sink body, the outer end surface of the ferrite core is in contact with the power tube, and the power tube is connected to the power tube heat sink body through a connector.

[0010] In some optional embodiments, a core isolator is installed between the outer end surface of the ferrite core and the power tube.

[0011] In some optional embodiments, a metal connecting cylinder is provided at the center of the accommodating cavity of the power tube radiator body, and through holes are provided on the ferrite core, the magnetic isolator and the power tube at the positions corresponding to the metal connecting cylinder, and the connecting parts are connected to the metal connecting cylinder through the through holes in turn.

[0012] In some optional embodiments, the metal connecting cylinder is provided with an internal thread, and the connecting piece is a fixing screw, which is threadedly connected to the metal connecting cylinder.

[0013] In some optional embodiments, the accommodating cavity is formed by a metal baffle that is symmetrically arranged on the other side of the power tube radiator.

[0014] In some optional embodiments, the magnetic core isolator is a rectangular metal plate, and a plurality of positioning blocks are provided on an end face of the magnetic isolator corresponding to the power tube, and the plurality of positioning blocks are in contact with the power tube.

[0015] In some optional embodiments, the lateral cross-section of the heat dissipation fin is an isosceles trapezoidal structure, and strip grooves are provided on the heat dissipation fin, and the strip grooves of two adjacent heat dissipation fins are arranged correspondingly.

[0016] In some optional implementation schemes, a plug-in rack connected to the PCB board is provided at the bottom of the power tube radiator body.

[0017] In some optional embodiments, thermal conductive silicone grease is coated between the contact surface between the core isolator and the power tube, a thermal conductive silicon sheet is installed between the contact surface between the core isolator and the ferrite core, and thermal conductive silicone grease is coated on both sides of the thermal conductive silicon sheet.

[0018] In some optional embodiments, the ferrite core is a Mn—Zn soft ferrite core.

[0019] The beneficial effects of the present application are as follows: the present application provides a power tube heat sink for reducing the common-mode current of a switching power supply, the power tube heat sink body is in direct contact with the power tube, the middle ferrite core and isolator are coated with thermal grease to enhance heat dissipation, and the heat sink fins are optimized. The isosceles trapezoidal slotted fins of the designed heat sink have greater heat transfer efficiency than general rectangular heat sink fins, which further enhances the heat dissipation capacity; the characteristics of the ferrite core are used to suppress EMI, and the processing difficulty and use cost are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is an isometric view of an embodiment of the present application;

[0022] Figure 2 An exploded diagram of an embodiment of the present application;

[0023] Figure 3 A side view of a power heat sink according to an embodiment of the present application;

[0024] Figure 4 This is a schematic structural diagram of a magnetic core isolator according to an embodiment of the present application;

[0025] Figure 5 This is a schematic diagram of the installation of an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0030] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0033] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0034] Some chips or CPU heat sinks use shielding to suppress EMI. The principle of shielding is simple and the effect is good, but it increases the heat transfer resistance and reduces the heat dissipation capacity. This requires cooperation with a heat sink with stronger heat dissipation capacity, such as a water-cooled heat sink and a fan. In many switching power supplies, there is not much limited space. Water-cooled heat sinks and fans occupy a large volume and require a more sophisticated layout of the power supply casing and PCB, so they may not be used. In this case, if only shielding measures are used, the heat of the power tube may have adverse effects. Based on this, the present invention proposes a power tube heat sink that reduces the common-mode current of the switching power supply, such as Figure 1-Figure 3 As shown, it includes a power tube heat sink body 1, a power tube 2 and a ferrite core 3. The heat dissipation fins 4 are evenly distributed on one end surface of the power tube heat sink, and a receiving cavity 5 is provided on the other side. The ferrite core is arranged in the receiving cavity. The inner end surface of the ferrite core is in close contact with the power heat sink body, and the outer end surface of the ferrite core is in contact with the power tube. The power tube is connected to the power tube heat sink body through a connector 6. A core isolator 7 is arranged between the outer end surface of the ferrite core and the power tube. The power tube can be any power switch electronic device that needs heat dissipation.

[0035] A metal connecting cylinder 8 is provided at the center of the accommodating cavity of the power tube heat sink body. Through holes are provided at the positions of the ferrite core, the magnetic isolator and the power tube and the metal connecting cylinder. The connecting parts pass through the through holes in sequence and are connected to the metal connecting cylinder. The metal connecting cylinder is provided with an internal thread, and the connecting parts are fixed screws, which are screwed to the metal connecting cylinder. The aperture of the through hole on the ferrite core is configured to match the outer diameter of the metal connecting cylinder.

[0036] The accommodating cavity is formed by a metal baffle 9 symmetrically arranged on the other side of the power tube radiator body. The material properties of the metal connecting cylinder and the metal baffle are the same as those of other parts of the power tube radiator body, and are all made of metal materials with good thermal conductivity.

[0037] The magnetic core isolator is a rectangular metal plate, and a plurality of positioning blocks 10 are provided on the end surface of the magnetic isolator corresponding to the power tube (see Figure 4 ), a plurality of positioning blocks are in contact with the power tube. The ferrite core is preferably a Mn-Zn soft ferrite core.

[0038] Thermal conductive silicone grease is coated between the contact surface of the magnetic core isolator and the power tube, a thermal conductive silicon sheet is arranged between the contact surface of the magnetic core isolator and the ferrite core, and thermal conductive silicone grease is coated on both sides of the thermal conductive silicon sheet.

[0039] The lateral cross section of the heat dissipation fin is an isosceles trapezoidal structure. The top surface of the heat dissipation fin is provided with a strip groove 11, and the strip grooves on two adjacent heat dissipation fins are arranged correspondingly.

[0040] The bottom of the power tube radiator is provided with a plug-in rack 12 connected to the PCB board (see Figure 5 ), so as to facilitate the fastening connection between the power tube radiator and the PCB board 13.

[0041] When the power switch device is working, its voltage and current will change constantly, and the lost energy will be converted into heat, which is one of the main heat sources of the switching power supply; in addition, each time the power switch tube switches, these jumping voltages will charge and discharge the parasitic capacitance, thereby forming a common mode current and causing conduction interference. In order to optimize the heat dissipation effect, the power tube is directly connected to the heat sink and the core isolator. The isosceles trapezoidal cross-section slotted heat sink fins used have a stronger heat dissipation effect than the rectangular cross-section heat sink. The core isolator is also a metal with good thermal conductivity (such as aluminum), which plays the role of a heat sink. The heat of the power tube is transferred to the heat sink and the core isolator through heat conduction. In order to prevent the power tube and the isolator from short-circuiting, a layer of thermally conductive insulating material (thermal conductive silicone grease) will be applied between them, which also reduces the heat transfer resistance. In addition to heat conduction, the thermally conductive silicon wafer between the ferrite core and the core isolator also acts as a gasket to reduce stress. The Mn-Zn soft ferrite core is embedded with the heat sink through the metal connecting cylinder of the heat sink. The common mode current generated by the power tube will pass through the metal connecting cylinder. Since the impedance of the ferrite material is large in the high frequency band, the common mode current will be reduced, which will suppress electromagnetic interference. Different ferrite materials have different optimal suppression frequency ranges, which is related to the magnetic permeability of the material. The higher the magnetic permeability of the material, the lower the optimal attenuation frequency. Mn-Zn ferrite is more suitable for use in frequency occasions below 30MHz, which is in line with the operating frequency of the power switch tube. In order to prevent the ferrite core from moving on the metal connecting cylinder of the heat sink, causing damage or colliding with other components, the power tube heat sink body is provided with a metal baffle to form a housing cavity to fix the ferrite core.

[0042] The above is only a preferred embodiment of the present intellectual achievement, but the present intellectual achievement should not be limited to the contents disclosed in the embodiment and the accompanying drawings. All equivalents or modifications completed without departing from the spirit disclosed in the present invention fall within the scope of protection of the present invention.

Claims

1. A power tube heat sink for reducing common mode current of a switching power supply, characterized in that: The invention comprises a power tube radiator body, a power tube and a ferrite core. The end surface of one side of the power tube radiator body is evenly distributed with heat dissipation fins, and the other side is provided with a receiving cavity. The ferrite core is arranged in the receiving cavity. The inner end surface of the ferrite core is in close contact with the power radiator body, and the outer end surface of the ferrite core is in contact with the power tube. The power tube is connected to the power tube radiator body through a connector.

2. A power tube heat sink for reducing common mode current of a switching power supply according to claim 1, characterized in that: A core isolator is arranged between the outer end surface of the ferrite core and the power tube.

3. A power tube heat sink for reducing common mode current of a switching power supply according to claim 2, characterized in that: A metal connecting cylinder is provided at the center of the accommodating cavity of the power tube radiator body, through holes are provided at the positions of the ferrite core, magnetic isolator and power tube and the metal connecting cylinder, and the connecting parts are connected to the metal connecting cylinder through the through holes in turn.

4. A power tube heat sink for reducing common mode current of a switching power supply according to claim 3, characterized in that: The metal connecting cylinder is provided with an internal thread, and the connecting piece is a fixing screw, which is threadedly connected to the metal connecting cylinder.

5. A power tube heat sink for reducing common mode current of a switching power supply according to claim 3 or 4, characterized in that: The accommodating cavity is formed by a metal baffle which is symmetrically arranged on the other side of the power tube radiator body.

6. A power tube heat sink for reducing common mode current of a switching power supply according to claim 2 or 4, characterized in that: The magnetic core isolator is a rectangular metal plate. A plurality of positioning blocks are arranged on the end surface of one side of the magnetic isolator corresponding to the power tube, and the plurality of positioning blocks are in contact with the power tube.

7. A power tube heat sink for reducing common mode current of a switching power supply according to claim 6, characterized in that: The lateral cross section of the heat dissipation fin is an isosceles trapezoidal structure. The heat dissipation fin is provided with a strip groove, and the strip grooves of two adjacent heat dissipation fins are arranged correspondingly.

8. The power tube heat sink for reducing common mode current of a switching power supply according to claim 7, characterized in that: The bottom of the power tube radiator body is provided with a plug-in rack connected to the PCB board.

9. A power tube heat sink for reducing common mode current of a switching power supply according to claim 6 or 8, characterized in that: Thermal conductive silicone grease is coated between the contact surface of the magnetic core isolator and the power tube, a thermal conductive silicon sheet is arranged between the contact surface of the magnetic core isolator and the ferrite core, and thermal conductive silicone grease is coated on both sides of the thermal conductive silicon sheet.

10. The power tube heat sink for reducing common mode current of a switching power supply according to claim 9, characterized in that: The ferrite core is a Mn-Zn soft ferrite core.

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