Planar transformer based on high-voltage silicon carbide device and testing method thereof

Abstract

The invention relates to a planar transformer based on a high-voltage silicon carbide device and a testing method of the planar transformer. The planar transformer comprises a multi-layer printed circuit board and a magnetic core. A mounting hole is formed in the multilayer printed circuit board, the multilayer printed circuit board comprises N copper layers and N-1 insulating medium layers, one insulating medium layer is connected between every two adjacent copper layers, and the other N-2 copper layers except the top copper layer and the bottom copper layer are wound by a circle of winding wire; the winding comprises a primary winding and a secondary winding, the primary winding comprises at least five branches which are connected in parallel, and each branch comprises two layers of winding wires which are connected in series; and two adjacent layers of winding wires in the secondary winding are sequentially connected in series. The planar transformer adopts the multi-layer printed circuit board as the winding, so that the overall size of the planar transformer is small; a circle of winding wire wound on the copper layer is adopted, so that the opposite area between the primary winding and the secondary winding is greatly reduced, the coupling capacitance of the planar transformer is reduced, and the common-mode interference resistance of the planar transformer is improved.

Description

Technical Field

[0001] The present application relates to the technical field of transformers, and in particular to a planar transformer based on a high-voltage silicon carbide device and a testing method thereof. Background Art

[0002] High-voltage silicon carbide (SiC) devices have the characteristics of high blocking voltage, low switching loss, high junction temperature and fast switching. In medium and high voltage power grid applications, they demonstrate converter-level advantages such as high efficiency, high power density and system-level advantages, enabling the converter to have better grid support functions.

[0003] As the basis for the driving circuit to normally drive high-voltage silicon carbide SiC devices, the isolated power supply is required to meet the relevant requirements of safety, stability and driving capability reliability. The main features of the isolated power supply are: First, high isolation withstand voltage. For high-voltage silicon carbide SiC devices, the isolation withstand voltage needs to be designed to be above 15kV, which has very high requirements for insulation materials and transformer structure; second, low coupling capacitance. The high-frequency voltage change rate dv / dt applied at both ends will cause a large common-mode current to pass through the coupling capacitor, thereby affecting the normal operation of the power supply. Therefore, the coupling capacitance needs to be suppressed; third, high power density. Comprehensive consideration is taken from aspects such as circuit topology and transformer structure design to improve the power density of the power supply while meeting the transmission power requirements.

[0004] Based on the insulation method used between the primary and secondary sides of the isolation transformer, isolated power supplies can be primarily categorized into three types. The first type utilizes a magnetically coupled core, such as a toroidal core, which can be encapsulated with silicone gel or epoxy resin. This provides high dielectric strength, but the high dielectric constant of the encapsulating material results in high coupling capacitance. However, to reduce parasitic capacitance to the target value, this may require a larger winding spacing and the distance between the winding and the core, which increases the size of the isolated power supply and makes it difficult to achieve a compact design. The second type utilizes an air core structure. This utilizes air insulation, which, due to its low dielectric constant, easily achieves low coupling capacitance. However, this results in low transformer coupling, high leakage inductance, and low efficiency. Furthermore, a larger gap distance is required to meet insulation requirements, resulting in increased size. The third type utilizes an optocoupler structure, which transmits power via optical fiber. This theoretically eliminates coupling capacitance and achieves higher insulation strength, but its low power rating and low efficiency make it unsuitable for high-power and high-efficiency power supply applications. Summary of the Invention

[0005] The present application provides a planar transformer based on a high-voltage silicon carbide device and a testing method thereof, which are used to solve the technical problems of large coupling capacitance and large size of the transformer of the existing isolated power supply.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] In one aspect, a planar transformer based on a high-voltage silicon carbide device is provided, comprising a multilayer printed circuit board and a magnetic core;

[0008] The copper layer of the multilayer printed circuit board is used as the winding of the planar transformer. The multilayer printed circuit board is provided with a mounting hole connected to the magnetic core. The multilayer printed circuit board includes N copper layers and N-1 insulating dielectric layers. One insulating dielectric layer is connected between two adjacent copper layers. Except for the top and bottom copper layers, the other N-2 copper layers are each wound with one turn of wire.

[0009] The winding includes a primary winding and a secondary winding. The primary winding includes at least 5 branches connected in parallel, and each branch includes 2 layers of windings connected in series. The two adjacent layers of windings in the secondary winding are connected in series in sequence.

[0010] Preferably, two adjacent copper layers are connected via buried vias.

[0011] Preferably, the multilayer printed circuit board includes a first solder resist layer and a second solder resist layer, the first solder resist layer is arranged above the copper layer on the top layer, and the second solder resist layer is arranged below the copper layer on the bottom layer.

[0012] Preferably, the insulating dielectric layer located below the copper layer on the top layer serves as the first insulating dielectric layer, and the insulating dielectric layer located above the copper layer on the bottom layer serves as the eleventh insulating dielectric layer. The thickness of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the thickness of the solder resist layer, and the dielectric strength of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the dielectric strength of the solder resist layer.

[0013] Preferably, the magnetic core installed in the installation hole is wrapped with an insulating element.

[0014] Preferably, an air gap is provided between the insulating element and the multilayer printed circuit board.

[0015] Preferably, the width of the air gap is 0.4 mm, and the width of the multilayer printed circuit board is 1.5 mm.

[0016] Preferably, the magnetic core is a ferrite core; and / or the winding is in a square shape; and / or the distance between the primary winding and the secondary winding is at least 40 mm.

[0017] In another aspect, a method for testing a planar transformer based on a high-voltage silicon carbide device is provided, which is applied to the planar transformer based on the high-voltage silicon carbide device described above, and the testing method comprises the following steps:

[0018] Obtaining a test type and test data corresponding to the test type;

[0019] The planar transformer based on the high-voltage silicon carbide device is tested according to the test data to obtain a test result.

[0020] Preferably, the method for testing a planar transformer based on a high-voltage silicon carbide device includes: if the test type is measuring coupling capacitance, the test data is a scanning frequency of 8 MHz to 10 MHz, and an impedance analysis device is used to test the planar transformer based on the high-voltage silicon carbide device according to the test data, and the test result obtained is the coupling capacitance;

[0021] If the test type is to measure the electric field strength, the test data is that the primary winding of the planar transformer based on the high-voltage silicon carbide device is grounded and a 16kV DC excitation signal is applied to the secondary winding. The planar transformer based on the high-voltage silicon carbide device is simulated and tested according to the test data, and the test result is the maximum electric field strength;

[0022] If the test type is a breakdown voltage test, the test data is continuous step voltage and more than 10 times of 20pC discharge data. The planar transformer based on high-voltage silicon carbide devices is discharged according to the test data, and the test result is the breakdown voltage of the planar transformer based on high-voltage silicon carbide devices.

[0023] The planar transformer based on a high-voltage silicon carbide device and its testing method include a multilayer printed circuit board and a magnetic core; the copper layer of the multilayer printed circuit board is used as the winding of the planar transformer, the multilayer printed circuit board is provided with a mounting hole connected to the magnetic core, the multilayer printed circuit board includes N copper layers and N-1 insulating dielectric layers, an insulating dielectric layer is connected between two adjacent copper layers, and the other N-2 copper layers except the top and bottom copper layers are each wound with one circle of winding; the winding includes a primary winding and a secondary winding, the primary winding includes at least five branches connected in parallel, each branch includes two layers of winding connected in series; the two adjacent layers of winding in the secondary winding are connected in series in sequence.

[0024] It can be seen from the above technical solution that the present application has the following advantages: the planar transformer based on high-voltage silicon carbide devices uses a multi-layer printed circuit board composed of N copper layers and N-1 insulating dielectric layers as the winding of the planar transformer, which reduces the overall size of the planar transformer based on high-voltage silicon carbide devices and increases the overall power density of the isolated power supply; by using a circle of winding wound on the copper layer, the facing area between the primary winding and the secondary winding is greatly reduced, thereby reducing the coupling capacitance of the planar transformer based on high-voltage silicon carbide devices, and improving the anti-common-mode interference capability of the planar transformer based on high-voltage silicon carbide devices, thereby solving the technical problem of large coupling capacitance and large volume of the transformer of the existing isolated power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 This is a front view of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0027] Figure 2 A top view of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0028] Figure 3 This is a schematic structural diagram of the primary winding in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0029] Figure 4 This is a schematic structural diagram of a secondary winding in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0030] Figure 5 This is a schematic cross-sectional view of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0031] Figure 6 This is a schematic structural diagram of a magnetic core in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0032] Figure 7 Schematic diagram of an equivalent capacitance model of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0033] Figure 8 This is a flowchart of the steps of the test method of the planar transformer based on the high-voltage silicon carbide device according to the embodiment of the present application;

[0034] Figure 9 This is a structural diagram of measuring coupling capacitance in a test method for a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0035] Figure 10 This is an electric field intensity distribution diagram for measuring electric field intensity in a test method for a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application;

[0036] Figure 11 This is a statistical chart of the number of discharges in a breakdown voltage test in a test method for a planar transformer based on a high-voltage silicon carbide device as described in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the embodiments of the present application, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections; direct connections, or indirect connections through an intermediate medium; internal connections between two components, or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0040] Patent terms used in this application:

[0041] SiC: The full name is Silicon Carbide, which is the third-generation semiconductor material.

[0042] Electrical clearance: refers to the shortest air distance between two conductive parts or between a conductive part and the grounded casing of the equipment.

[0043] Creepage distance: The shortest path along an insulating surface that prevents leakage current caused by contaminants (such as dust and moisture).

[0044] Coupling capacitance: refers to the parasitic capacitance formed between two conductors or circuits due to the interaction of electric fields.

[0045] FR4 substrate: a composite material laminated by epoxy resin and glass fiber cloth, widely used as an insulating substrate for printed circuit boards.

[0046] Partial Discharge Inception Voltage: The lowest voltage at which partial discharge begins to occur in an insulating material or structure. Partial discharge refers to non-penetrating discharge that occurs in a small area when the local electric field strength exceeds the dielectric withstand capacity.

[0047] Breakdown voltage: The critical voltage at which an insulating material completely loses its insulating ability. At this point, the material is destroyed by an arc or electrical breakdown, forming a conductive path.

[0048] The embodiments of the present application provide a planar transformer based on a high-voltage silicon carbide device and a testing method thereof, which solve the technical problems of large coupling capacitance and large size of the transformer of the existing isolated power supply.

[0049] Example 1:

[0050] Figure 1 This is a front view of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application. Figure 2 This is a top view of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application. Figure 3 This is a schematic structural diagram of the primary winding in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application. Figure 4 This is a schematic structural diagram of the secondary winding in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application.

[0051] like Figures 1 to 4 As shown, an embodiment of the present application provides a planar transformer based on a high-voltage silicon carbide device, including a multilayer printed circuit board 10 and a magnetic core 20.

[0052] In the embodiment of the present application, the copper layer of a multilayer printed circuit board 10 serves as the winding of a planar transformer. Mounting holes 11 are provided on the multilayer printed circuit board 10 for connection to a magnetic core 20. The multilayer printed circuit board 10 includes N copper layers and N-1 insulating dielectric layers (FR4). An insulating dielectric layer (FR4) is connected between adjacent copper layers. Except for the top and bottom copper layers, each of the remaining N-2 copper layers is wound with a single turn of wire. The windings include a primary winding 12 and a secondary winding 13.

[0053] It should be noted that the multilayer printed circuit board 10 is selected as an N-layer PCB board structure, and the value of N can be selected as 12. The N copper layers Layer include a first copper layer Layer 1, a second copper layer Layer 2, a third copper layer Layer 3, a fourth copper layer Layer 4, a fifth copper layer Layer 5, a sixth copper layer Layer 6, a seventh copper layer Layer 7, an eighth copper layer Layer 8, a ninth copper layer Layer 9, a tenth copper layer Layer 10, an eleventh copper layer Layer 11, and a twelfth copper layer Layer 12. The N-1 insulating dielectric layer FR4 includes a first insulating dielectric layer, a second insulating dielectric layer, a third insulating dielectric layer, a fourth insulating dielectric layer, a fifth insulating dielectric layer, a sixth insulating dielectric layer, a seventh insulating dielectric layer, an eighth insulating dielectric layer, a ninth insulating dielectric layer, a tenth insulating dielectric layer, and an eleventh insulating dielectric layer. An insulating dielectric layer FR4 is connected between two adjacent copper layers. It can be understood as follows: the first copper layer Layer1 and the second copper layer Layer2 are connected to the first insulating dielectric layer, the second copper layer Layer2 and the third copper layer Layer3 are connected to the second insulating dielectric layer, the third copper layer Layer3 and the fourth copper layer Layer4 are connected to the third insulating dielectric layer, the fourth copper layer Layer4 and the fifth copper layer Layer5 are connected to the fourth insulating dielectric layer, the fifth copper layer Layer5 and the sixth copper layer Layer6 are connected to the fifth insulating dielectric layer, and the sixth copper layer Layer7 is connected to the fifth insulating dielectric layer. ayer6 and the seventh copper layer Layer7 are connected to the sixth insulating dielectric layer, the seventh copper layer Layer7 and the eighth copper layer Layer8 are connected to the seventh insulating dielectric layer, the eighth copper layer Layer8 and the ninth copper layer Layer9 are connected to the eighth insulating dielectric layer, the ninth copper layer Layer9 and the tenth copper layer Layer10 are connected to the ninth insulating dielectric layer, the tenth copper layer Layer10 and the eleventh copper layer Layer11 are connected to the tenth insulating dielectric layer, and the eleventh copper layer Layer11 and the twelfth copper layer Layer12 are connected to the eleventh insulating dielectric layer. Except for the top and bottom copper layers, the other N-2 copper layers are all wound with one turn of wire. This can be understood as follows: the second copper layer Layer2, the third copper layer Layer3, the fourth copper layer Layer4, the fifth copper layer Layer5, the sixth copper layer Layer6, the seventh copper layer Layer7, the eighth copper layer Layer8, the ninth copper layer Layer9, the tenth copper layer Layer10, and the eleventh copper layer Layer11 are all wound with one turn of wire, while the first copper layer Layer1 and the twelfth copper layer Layer12 are not wound with one turn of wire, that is, no winding arrangement is performed. In this embodiment, the insulating dielectric layer can be made of FR4 substrate material. FR4, as a glass fiber reinforced composite material, has good insulation properties and can withstand the high isolation voltage between the primary winding 12 and the secondary winding 13.

[0054] In an embodiment of the present application, in the application of a high-voltage power device isolated power supply, for a 10kV SiC device, the planar transformer based on the high-voltage SiC device is required to meet insulation requirements of 15kV and above. Therefore, the primary winding 12 and the secondary winding 13 of the planar transformer based on the high-voltage SiC device are integrated into a multilayer printed circuit board 10 and are separately wound on both sides of the multilayer printed circuit board 10. The electrical clearance of the planar transformer based on the high-voltage SiC device should be at least 60mm, and the creepage distance of the planar transformer based on the high-voltage SiC device should be at least 80mm, so that the planar transformer based on the high-voltage SiC device meets the requirements of electrical standards (such as GB 4943.1 and IEC61800-5-1).

[0055] In an embodiment of the present application, the primary winding includes at least 5 branches connected in parallel, each branch includes 2 layers of windings connected in series; the two adjacent layers of windings in the secondary winding are connected in series in sequence.

[0056] It should be noted that if Figure 3 As shown, at least 5 branches connected in parallel can be understood as follows: the winding wound on the second copper layer Layer2 and the winding wound on the seventh copper layer Layer7 are connected in series to form a first branch, the winding wound on the third copper layer Layer3 and the winding wound on the eighth copper layer Layer8 are connected in series to form a second branch, the winding wound on the fourth copper layer Layer4 and the winding wound on the ninth copper layer Layer9 are connected in series to form a third branch, the winding wound on the fifth copper layer Layer5 and the winding wound on the tenth copper layer Layer10 are connected in series to form a fourth branch, and the winding wound on the fifth copper layer Layer5 and the winding wound on the eleventh copper layer Layer11 are connected in series to form a fifth branch. The first branch, the second branch, the third branch, the fourth branch and the fifth branch are connected in parallel, so that the actual number of turns of the primary winding 12 is 2 turns. Figure 4As shown, the two adjacent layers of windings in the secondary winding are connected in series in sequence, which can be understood as follows: the winding wound on the second copper layer Layer2 is connected in series with the winding wound on the third copper layer Layer3, the winding wound on the third copper layer Layer3 is connected in series with the winding wound on the fourth copper layer Layer4, the winding wound on the fourth copper layer Layer4 is connected in series with the winding wound on the fifth copper layer Layer5, the winding wound on the fifth copper layer Layer5 is connected in series with the winding wound on the sixth copper layer Layer6, and the winding wound on the sixth copper layer Layer6 is connected in series. The secondary winding 13 is connected in series with the winding wound on the seventh copper layer, Layer 7. The winding wound on the seventh copper layer, Layer 7, is connected in series with the winding wound on the eighth copper layer, Layer 8. The winding wound on the eighth copper layer, Layer 8, is connected in series with the winding wound on the ninth copper layer, Layer 9. The winding wound on the ninth copper layer, Layer 9, is connected in series with the winding wound on the tenth copper layer, Layer 10. The winding wound on the tenth copper layer, Layer 10, is connected in series with the winding wound on the eleventh copper layer, Layer 11. This results in the actual number of turns of the secondary winding 13 being 10. In this embodiment, adjacent copper layers, Layers, are connected via buried vias 60. Because the actual number of turns of the primary winding 12 is 2 and the actual number of turns of the secondary winding 13 is 10, the primary current of this planar transformer based on high-voltage silicon carbide devices is 5 times the secondary current, thereby enhancing the current carrying capacity of the primary winding.

[0057] In an embodiment of the present application, the primary winding 12 of the planar transformer based on high-voltage silicon carbide devices is connected to a half-bridge device with an input voltage of 24V, and the secondary winding 13 is connected to a rectifier diode with an output voltage of 30V in a center-tap manner, so the turns ratio is 1:5. In order to increase the excitation inductance and reduce the loss of the isolated power supply, the primary winding 12 is set to 2 turns and the secondary winding 13 is set to 10 turns.

[0058] It should be noted that in order to miniaturize the overall volume of the planar transformer based on high-voltage silicon carbide devices, the width of the primary winding 12 and the secondary winding 13 can be selected as 1.2 mm, the side length of the primary winding 12 and the secondary winding 13 can be selected as 13 mm, and the copper thickness of the primary winding 12 and the secondary winding 13 can be selected as 1 oz.

[0059] In an embodiment of the present application, the planar transformer based on a high-voltage silicon carbide device uses a multilayer printed circuit board composed of N copper layers and N-1 insulating dielectric layers as the winding of the planar transformer, thereby reducing the overall size of the planar transformer based on the high-voltage silicon carbide device and increasing the overall power density of the isolated power supply. The planar transformer based on the high-voltage silicon carbide device uses a single coil of wire wound on the copper layer, which greatly reduces the facing area between the primary winding 12 and the secondary winding 13 of the planar transformer based on the high-voltage silicon carbide device, thereby reducing the coupling capacitance of the planar transformer based on the high-voltage silicon carbide device and improving the anti-common-mode interference capability of the planar transformer based on the high-voltage silicon carbide device.

[0060] The present application provides a planar transformer based on a high-voltage silicon carbide device, comprising a multilayer printed circuit board and a magnetic core; the copper layer of the multilayer printed circuit board is used as the winding of the planar transformer, and the multilayer printed circuit board is provided with a mounting hole connected to the magnetic core. The multilayer printed circuit board comprises N copper layers and N-1 insulating dielectric layers, an insulating dielectric layer is connected between two adjacent copper layers, and the other N-2 copper layers except the top and bottom copper layers are each wound with one turn of winding; the winding comprises a primary winding and a secondary winding, the primary winding comprises at least 5 branches connected in parallel, each branch comprises 2 layers of windings connected in series; the adjacent two layers of windings in the secondary winding are connected in series in sequence. The planar transformer based on the high-voltage silicon carbide device uses a multi-layer printed circuit board composed of N copper layers and N-1 insulating dielectric layers as the winding of the planar transformer, which reduces the overall size of the planar transformer based on the high-voltage silicon carbide device and increases the overall power density of the isolated power supply. By using a circle of winding wound on the copper layer, the facing area between the primary winding and the secondary winding is greatly reduced, thereby reducing the coupling capacitance of the planar transformer based on the high-voltage silicon carbide device, improving the anti-common-mode interference capability of the planar transformer based on the high-voltage silicon carbide device, and solving the technical problem of large coupling capacitance and large size of the transformer of the existing isolated power supply.

[0061] like Figure 3 and Figure 4 As shown, in one embodiment of the present application, a multilayer printed circuit board 10 includes a first solder resist layer and a second solder resist layer, a solder resist layer 14 is arranged above the copper layer located on the top layer (i.e., the first copper layer Layer 1), and the solder resist layer 15 on the other side is arranged below the copper layer located on the bottom layer (i.e., the twelfth copper layer Layer 12); the insulating dielectric layer located below the top copper layer serves as the first insulating dielectric layer, and the insulating dielectric layer located above the bottom copper layer serves as the eleventh insulating dielectric layer. The thickness of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the thickness of the solder resist layer, and the dielectric strength of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the dielectric strength of the solder resist layer.

[0062] It should be noted that since the first copper layer Layer 1 and the twelfth copper layer Layer 12 do not have windings (that is, no winding is wrapped), and all copper layers are connected through buried vias 60 rather than through holes, the insulating dielectric layer FR4 between the first copper layer Layer 1 and the second copper layer Layer 2 and the insulating dielectric layer FR4 between the eleventh copper layer Layer 11 and the twelfth copper layer Layer 12 can act as surface insulating media. The thickness and dielectric strength of the insulating dielectric layer FR4 are higher than those of the solder resist layer, which can effectively reduce the risk of the solder resist layer and the insulating dielectric layer FR4 being simultaneously broken down and forming a leakage path on the surface of the multi-layer printed circuit board 10.

[0063] Figure 5 This is a schematic cross-sectional structural diagram of a planar transformer based on a high-voltage silicon carbide device described in an embodiment of the present application.

[0064] like Figure 5 As shown, in one embodiment of the present application, the magnetic core 20 installed in the mounting hole 11 is wrapped with an insulating element 30 ; an air gap 40 is provided between the insulating element 30 and the multilayer printed circuit board 10 .

[0065] It should be noted that the width of the air gap 40 may be 0.4 mm, and the width of the multilayer printed circuit board 10 may be 1.5 mm. In this embodiment, the insulating element 30 may be a polyimide film tape, which is wound around the outer surface of the magnetic core 20 .

[0066] In an embodiment of the present application, the high-voltage silicon carbide device-based planar transformer achieves insulation enhancement at the vertical structural level by not wrapping a single turn of wire around the outermost copper layers (i.e., the first and twelfth copper layers) of the multilayer printed circuit board 10 and connecting two adjacent copper layers via buried vias 60. The three-layer insulation system of the multilayer printed circuit board 10, comprising the insulating dielectric layer, the air gap 40, and the insulating element 30, further enhances the isolation strength of the high-voltage silicon carbide device-based planar transformer. This also enhances the insulation of the high-voltage silicon carbide device-based planar transformer at the horizontal structural level, preventing discharge and breakdown from occurring in the horizontal path from the winding to the magnetic core of the high-voltage silicon carbide device-based planar transformer. This improves the uniformity of the electric field strength distribution of the high-voltage silicon carbide device-based planar transformer and enhances the insulation capability of the high-voltage silicon carbide device-based planar transformer. For example, the breakdown field strength of the FR4 insulating dielectric layer of the planar transformer of the silicon carbide device is 16-20 kV / mm, the breakdown field strength of the air gap 40 is 3 kV / mm, and the breakdown field strength of the insulating element 30 made of polyimide (Arlon 85N material) is 57.1 kV / mm. Therefore, the withstand voltage of the planar transformer of the silicon carbide device from the winding to the magnetic core 20 in the horizontal direction is at least 25 kV, which means that the withstand voltage of the primary winding 12 and the secondary winding 13 in the horizontal direction is at least 50 kV, so that the planar transformer of the silicon carbide device meets the withstand voltage requirements of the isolated power supply.

[0067] Figure 6 This is a schematic structural diagram of the magnetic core in a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application.

[0068] like Figure 1 、 Figure 2 and Figure 6 As shown, in one embodiment of the present application, the magnetic core 20 is a ferrite core; and / or the winding is in a square shape; and / or the distance between the primary winding and the secondary winding is at least 40 mm.

[0069] It should be noted that the core structure is as follows Figure 6 As shown, the magnetic core 20 has a "U"-shaped structure and uses the UI61 series DMR95 ferrite core. The high-frequency characteristics and saturation flux density of the magnetic core 20 are more compatible with the fast switching frequency of the silicon carbide SiC device. Figure 6 As shown, the dimensions of the magnetic core 20 are: total length A=61mm, C=8mm, width D=8mm, I=8mm, height E=10mm, F=18mm. The primary winding 12 and the secondary winding 13 both adopt a square structure.

[0070] Figure 7Schematic diagram of the equivalent capacitance model of a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application.

[0071] like Figure 7 As shown, in the embodiment of the present application, the three-part capacitor of the planar transformer based on the high-voltage silicon carbide device constitutes the total coupling capacitor. The first part of the capacitor is the capacitor C between the primary winding and the secondary winding. PS The second part of the capacitance is the capacitance C between the primary winding and the magnetic core. PC The third part of the capacitor is the capacitance C between the secondary winding and the magnetic core. SC The three nodes C, P, and S represent the core, primary winding, and secondary winding, respectively. Therefore, the total coupling capacitance of the planar transformer based on high-voltage silicon carbide devices is expressed as:

[0072]

[0073] Where C coupling is the total coupling capacitance. According to the total coupling capacitance expression, reduce C PS 、C PC 、C SC Any of these three capacitors can reduce the total coupling capacitance of the planar transformer based on high-voltage silicon carbide devices, thereby improving the anti-common-mode interference capability of the planar transformer based on high-voltage silicon carbide devices. The general capacitance calculation formula is: , is the dielectric constant of the medium, S is the facing area of the two objects, and d is the distance between the two objects. Therefore, the capacitance can be reduced by reducing the facing area, increasing the distance, or using a medium with a smaller dielectric constant. The planar transformer based on the high-voltage silicon carbide device uses a multi-layer printed circuit board as a flat winding. Compared with the traditional wound transformer, the planar transformer based on the high-voltage silicon carbide device has a smaller winding area, thereby reducing the coupling capacitance of the planar transformer based on the high-voltage silicon carbide device. In this embodiment, the facing area of the primary winding and the secondary winding of the planar transformer based on the high-voltage silicon carbide device is very small (about 4.55mm 2 ), and the distance between the primary winding and the secondary winding is large (40mm). Under the action of the insulating medium layer FR4 with a relative dielectric constant of 4.4, C PS It is about 0.0044pF, which can be ignored. As for the capacitance between the winding and the magnetic core 20, a single-layer single-turn winding structure is adopted in which each copper layer is wound with one turn of wire as the planar transformer based on the high-voltage silicon carbide device, so that the winding has a smaller area facing the magnetic core. For example: in the horizontal direction, it is necessary to consider the area of the magnetic core 20 with N-2 layers of copper layers wound with one turn of wire. Since the side length of each copper layer wound with one turn of wire is 13mm and the copper thickness of each copper layer wound with one turn of wire is 1oz, the area of the winding is about 18.2mm2 For a single-layer double-turn winding structure, there are 5 layers of winding. Therefore, in the horizontal direction, the area of the winding relative to the core is halved compared to the single-layer single-turn winding structure, which is about 9.1mm. 2 In the vertical direction, the area of the core for one circle of the second and eleventh copper layers needs to be considered. Since the width of one circle of the wire wrapped around each copper layer is 1.2 mm, the area of the winding is approximately 124.8 mm. 2 The total area of the single-layer single-turn winding structure facing the magnetic core is about 143mm 2 The area of the core for the 1st and 5th layers (4 turns) must be considered. This area is at least twice that of a single-layer, single-turn winding structure, approximately 249.6 mm. 2 Therefore, the total area of the single-layer double-turn winding structure facing the magnetic core is about 258.7mm 2 .

[0074] In the embodiment of the present application, the single-layer single-turn winding structure of the planar transformer based on the high-voltage silicon carbide device has more winding layers, but can significantly reduce the area of the winding to the magnetic core, thereby reducing the coupling capacitance of the planar transformer. The length, width and height of the planar transformer based on the high-voltage silicon carbide device are 146.05mm, 25.4mm and 25.908mm respectively, and the volume is about 96.11cm 3 The power of the planar transformer based on high-voltage silicon carbide devices is 20W, and the power density of the planar transformer based on high-voltage silicon carbide devices is about 0.21W / cm 3 .

[0075] In an embodiment of the present application, the planar transformer based on a high-voltage silicon carbide device uses a multi-layer printed circuit board to reduce the area of the winding facing the magnetic core, greatly reducing the coupling capacitance and improving the common-mode suppression capability. The planar transformer based on a high-voltage silicon carbide device is wound with a single-layer single-turn winding structure on the outermost copper layer of the multi-layer printed circuit board. Compared with the single-layer multi-turn layout, it can further reduce the area of the winding facing the magnetic core, thereby reducing the coupling capacitance. The planar transformer based on a high-voltage silicon carbide device is wound with a single-layer winding on the top copper layer and the bottom copper layer of the multi-layer printed circuit board. The two adjacent copper layers are electrically connected through buried vias 60, avoiding the use of through-holes to connect to the bottom copper layer and the bottom copper layer, so as to increase the creepage distance of the planar transformer based on a high-voltage silicon carbide device and improve the insulation performance of the planar transformer based on a high-voltage silicon carbide device.

[0076] It should be noted that this planar transformer based on high-voltage silicon carbide devices utilizes a U-shaped DMR95 core structure encapsulated with FR4 dielectric layers and polyimide insulating tape. Combined with a single-layer, single-turn primary and secondary winding design, this effectively reduces the winding's facing area and reduces coupling capacitance to 1.29pF. A single-turn winding design with no twisting between the top and bottom copper layers, combined with spacing design, ensures a creepage distance of 94mm and a clearance of 68mm. This planar transformer based on high-voltage silicon carbide devices offers several times the performance of traditional solutions, combining high insulation reliability with compactness. It provides a highly efficient, high-insulation, and low-common-mode isolation solution for high-voltage power device drive circuits.

[0077] Example 2:

[0078] Figure 8 This is a flowchart of the steps of the testing method of the planar transformer based on the high-voltage silicon carbide device described in an embodiment of the present application.

[0079] like Figure 8 As shown, an embodiment of the present application provides a test method for a planar transformer based on a high-voltage silicon carbide device, which is applied to the above-mentioned planar transformer based on a high-voltage silicon carbide device. The test method includes the following steps:

[0080] S1. Obtain the test type and the test data corresponding to the test type;

[0081] S2. Test the planar transformer based on the high-voltage silicon carbide device according to the test data to obtain test results.

[0082] It should be noted that the content of the planar transformer based on the high-voltage silicon carbide device in the second embodiment has been described in the first embodiment, and the content of the planar transformer based on the high-voltage silicon carbide device will not be repeated in this embodiment.

[0083] Figure 9 This is a structural diagram of measuring coupling capacitance in a test method for a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application. Figure 10 This is an electric field intensity distribution diagram for measuring electric field intensity in the test method for a planar transformer based on a high-voltage silicon carbide device according to an embodiment of the present application. Figure 11 This is a statistical chart of the number of discharges in a breakdown voltage test in a test method for a planar transformer based on a high-voltage silicon carbide device as described in an embodiment of the present application.

[0084] like Figure 9 As shown, in an embodiment of the present application, if the test type is to measure the coupling capacitance, the test data is a scanning frequency of 8MHz~10MHz, and an impedance analysis device is used to test the planar transformer based on the high-voltage silicon carbide device according to the test data, and the test result is the coupling capacitance.

[0085] It should be noted that the impedance analysis equipment can be an impedance analyzer. The coupling capacitance of the planar transformer based on the high-voltage silicon carbide device was measured using the impedance analyzer E4490A, with the sweep frequency set to 8MHz~10MHz. The test results are as follows: Figure 9 As shown in the figure, the measured coupling capacitance is about 1.29pF. The extremely low coupling capacitance of the planar transformer based on high-voltage silicon carbide devices indicates that it has excellent common-mode suppression capability.

[0086] like Figure 10 As shown, in an embodiment of the present application, if the test type is to measure the electric field strength, the test data is that the primary winding of the planar transformer based on the high-voltage silicon carbide device is grounded and a 16kV DC excitation signal is applied to the secondary winding. The planar transformer based on the high-voltage silicon carbide device is simulated and tested according to the test data, and the test result is the maximum electric field strength.

[0087] It should be noted that based on electromagnetic simulation analysis, a finite element simulation of a planar transformer based on a high-voltage silicon carbide device was performed. The primary winding was grounded and a 16kV DC excitation signal was applied to the secondary winding. The simulation results are as follows: Figure 10 As shown in Figure 1, the maximum electric field strength of the planar transformer based on high-voltage silicon carbide devices is 8.331 kV / mm, which is lower than the dielectric strength of the insulating medium layer (16~20 kV / mm).

[0088] like Figure 11 As shown, in an embodiment of the present application, if the test type is a breakdown voltage test, the test data is continuous step voltage and more than 10 times of 20pC discharge data. According to the test data, a discharge test is performed on the planar transformer based on the high-voltage silicon carbide device, and the test result is the breakdown voltage of the planar transformer based on the high-voltage silicon carbide device.

[0089] It should be noted that the isolation capability of the planar transformer based on high-voltage silicon carbide devices was further verified by using a DC voltage test platform, and the partial discharge inception voltage was determined by using more than 10 discharges of 20pC or more over three consecutive voltage steps as the standard. Figure 11 As shown in the data, when the DC test voltage was 15.5kV DC, the discharge exceeded 20pC 13 times; when the DC test voltage was 16kV DC and 16.5kV DC, the discharge exceeded 20pC 33 times and 48 times, respectively. Therefore, the partial discharge inception voltage of this planar winding transformer was determined to be 15.5kV DC. When the voltage rose to 19.5kV DC, breakdown occurred along the surface of the multilayer printed circuit board between the test point with the high-voltage fixture and the magnetic core, indicating a breakdown voltage of 19.5kV DC. These results demonstrate that this planar transformer based on high-voltage silicon carbide devices has excellent insulation performance.

[0090] For example, a computer program may be divided into one or more modules / units, one or more of which are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0091] Terminal devices can be computing devices such as desktop computers, laptops, PDAs, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will appreciate that this does not constitute a limitation on terminal devices and may include more or fewer components than shown, or a combination of certain components, or different components. For example, terminal devices may also include input / output devices, network access devices, buses, and the like.

[0092] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0093] Memory can be an internal storage unit of a terminal device, such as a hard drive or memory. It can also be an external storage device, such as a plug-in hard drive, a SmartMedia Card (SMC), a Secure Digital (SD) card, or a flash memory card. Furthermore, memory can include both internal and external storage units. Memory is used to store computer programs and other programs and data required by the terminal device. Memory can also be used to temporarily store data that has been output or is about to be output.

[0094] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0095] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0096] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0097] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0098] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0099] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A planar transformer based on a high voltage silicon carbide device, characterized in that: including a multi-layer printed circuit board and a magnetic core; The copper layer of the multilayer printed circuit board is used as the winding of the planar transformer. The multilayer printed circuit board is provided with a mounting hole connected to the magnetic core. The multilayer printed circuit board includes N copper layers and N-1 insulating dielectric layers. One insulating dielectric layer is connected between two adjacent copper layers. Except for the top and bottom copper layers, the other N-2 copper layers are each wound with one turn of wire. The winding includes a primary winding and a secondary winding. The primary winding includes at least 5 branches connected in parallel, and each branch includes 2 layers of windings connected in series. The two adjacent layers of windings in the secondary winding are connected in series in sequence.

2. The planar transformer based on a high-voltage silicon carbide device according to claim 1, characterized in that: The two adjacent copper layers are connected via buried vias.

3. The planar transformer based on a high-voltage silicon carbide device according to claim 1 or 2, characterized in that: The multi-layer printed circuit board includes a first solder resist layer and a second solder resist layer, wherein the first solder resist layer is arranged above the copper layer located on the top layer, and the second solder resist layer is arranged below the copper layer located on the bottom layer.

4. The planar transformer based on a high-voltage silicon carbide device according to claim 3, characterized in that: The insulating dielectric layer located below the copper layer on the top layer serves as the first insulating dielectric layer, and the insulating dielectric layer located above the copper layer on the bottom layer serves as the eleventh insulating dielectric layer. The thicknesses of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the thickness of the solder resist layer, and the dielectric strengths of the first insulating dielectric layer and the eleventh insulating dielectric layer are both higher than the dielectric strength of the solder resist layer.

5. The planar transformer based on a high-voltage silicon carbide device according to claim 1 or 2, characterized in that: The magnetic core installed in the installation hole is wrapped with an insulating element.

6. The planar transformer based on a high-voltage silicon carbide device according to claim 5, characterized in that: An air gap is provided between the insulating element and the multilayer printed circuit board.

7. The planar transformer based on a high-voltage silicon carbide device according to claim 6, characterized in that: The width of the air gap is 0.4 mm, and the width of the multilayer printed circuit board is 1.5 mm.

8. The planar transformer based on a high voltage silicon carbide device according to claim 1 or 2, characterized in that: The magnetic core is a ferrite core; and / or the winding is in a square shape; and / or the distance between the primary winding and the secondary winding is at least 40 mm.

9. A method for testing a planar transformer based on a high-voltage silicon carbide device, applied to the planar transformer based on a high-voltage silicon carbide device according to any one of claims 1 to 8, characterized in that: The test method includes the following steps: Obtaining a test type and test data corresponding to the test type; The planar transformer based on the high-voltage silicon carbide device is tested according to the test data to obtain a test result.

10. The method for testing a planar transformer based on a high-voltage silicon carbide device according to claim 9, wherein: include: If the test type is measuring coupling capacitance, the test data is a scanning frequency of 8 MHz to 10 MHz, and an impedance analysis device is used to test the planar transformer based on the high-voltage silicon carbide device according to the test data, and the test result obtained is coupling capacitance; If the test type is to measure the electric field strength, the test data is that the primary winding of the planar transformer based on the high-voltage silicon carbide device is grounded and a 16kV DC excitation signal is applied to the secondary winding. The planar transformer based on the high-voltage silicon carbide device is simulated and tested according to the test data, and the test result is the maximum electric field strength; If the test type is a breakdown voltage test, the test data is continuous step voltage and more than 10 times of 20pC discharge data. The planar transformer based on high-voltage silicon carbide devices is discharged according to the test data, and the test result is the breakdown voltage of the planar transformer based on high-voltage silicon carbide devices.

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