A planar transformer

Abstract

The application provides a planar transformer, and relates to the technical field of transformers, which comprises a primary spiral coil and a secondary spiral coil arranged in a stack, wherein each of the primary spiral coil and the secondary spiral coil comprises a plurality of sub-coils connected in series, the magnetic fields generated by each of the sub-coils in the primary spiral coil cancel each other out, and the magnetic fields generated by each of the sub-coils in the secondary spiral coil cancel each other out; the number of each of the sub-coils contained in the primary spiral coil and the secondary spiral coil is even, and the upper and lower sub-coils are distributed in an axial symmetry. The beneficial effect is that the planar transformer is designed in such a manner that the magnetic fields generated by each of the sub-coils in the primary spiral coil cancel each other out, the magnetic fields generated by each of the sub-coils in the secondary spiral coil cancel each other out, and the upper and lower sub-coils of the primary spiral coil and the secondary spiral coil are distributed in an axial symmetry, thereby significantly reducing radiation disturbance and conduction disturbance, and without relying on a metal shielding cover or a filtering circuit.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and more particularly to a planar transformer. Background Technology

[0002] As electronic devices become smaller, higher frequency, and more integrated, planar transformers, with their advantages of small size, light weight, good high-frequency characteristics, and ease of integration with PCBs, are not only widely used in the consumer electronics field, but are also gradually becoming core components for energy transmission in vehicles, ships, and internal combustion engine systems. For example, the on-board charger (OBC) of new energy vehicles, the power module of the ship communication system, and the power supply unit of the internal combustion engine controller all rely on planar transformers to achieve efficient voltage conversion.

[0003] However, the electromagnetic compatibility requirements for these special application scenarios are far higher than those for ordinary consumer electronics. As a medium for energy transmission, transformers generate alternating electromagnetic fields during operation, which can interfere with other electronic devices in the system through radiated and conducted emissions. Specifically, in terms of radiated emissions, high-frequency alternating magnetic fields can directly radiate to surrounding sensitive components (such as wireless communication antennas in vehicles and radio receiver modules in ships), suppressing useful signals and even causing equipment malfunctions (such as the protective shutdown of an internal combustion engine controller due to radiated interference).

[0004] In terms of conducted emission, alternating electromagnetic fields can be conducted through power lines and signal lines to devices such as the ECU of a vehicle, the GPS navigation module of a ship, and the sensor circuit of an internal combustion engine, leading to misinterpretation of control signals, such as distortion of millimeter-wave radar data in vehicle autonomous driving systems, deviation in ship navigation and positioning, and disorder of fuel injection timing in internal combustion engines.

[0005] To regulate such radio interference, the Chinese standard GB / T 18655-2018, "Limits and methods of measurement for radio interference characteristics of vehicles, ships and internal combustion engines for the protection of vehicle-mounted receivers," clearly stipulates that the radiated interference field strength of electronic equipment in vehicles, ships and internal combustion engine systems must be ≤54dBμV / m in the 30MHz-1GHz frequency band (Class 3 limit), and the conducted interference must be ≤79dBμV (voltage method) in the 150kHz-30MHz frequency band. The International Electrotechnical Commission's CISPR series standards (such as CISPR 25 "Limits and methods of measurement for radio interference characteristics of vehicles, ships and internal combustion engines" and CISPR 16 "Specifications for equipment and methods of measurement for radio interference and immunity") further impose stringent requirements on the testing environment and measurement accuracy.

[0006] Traditional planar transformers, due to structural design flaws, struggle to consistently meet the aforementioned standards even with passive suppression measures such as metal shielding and filtering circuits. While metal shielding can reduce some radiation, it increases the transformer's size and weight, which is unacceptable given the lightweight design of vehicles and the compact hull layout of ships. Furthermore, the vibration environment of internal combustion engine systems can easily lead to poor contact of the shielding, resulting in a loss of shielding effectiveness. Filtering circuits introduce additional power losses, contradicting the requirements for improved vehicle range, energy conservation in ships, and optimized energy efficiency in internal combustion engine systems. Moreover, under high-frequency conditions (such as when the operating frequency of onboard transformers exceeds 500kHz), the parasitic parameters of the filter capacitors can cause a sharp drop in filtering effectiveness, still posing a risk of exceeding standards. Additionally, when the input is a differential signal commonly used in vehicle and ship systems, the differential signal is prone to conversion to a common-mode signal, further exacerbating conducted and radiated interference.

[0007] Therefore, there is an urgent need for a planar transformer structure that, from a structural design perspective, can actively cancel out conduction and radiation through the magnetic field of the sub-coil to achieve low interference, while also being adaptable to the size, energy efficiency, and reliability requirements of vehicles, ships, and internal combustion engine systems. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides a planar transformer, comprising a primary helical coil and a secondary helical coil stacked together. Both the primary and secondary helical coils include multiple sub-coils connected in series. The magnetic fields generated by each sub-coil in the primary helical coil cancel each other out, and the magnetic fields generated by each sub-coil in the secondary helical coil also cancel each other out. The number of each sub-coil included in the primary and secondary helical coils is even, and the sub-coils in the upper and lower parts of the primary and secondary helical coils are axially symmetrically distributed.

[0009] Preferably, the projections of the center point of the primary spiral coil and the center point of the secondary spiral coil in the stacking direction coincide.

[0010] Preferably, the number of each of the sub-coils forming the primary spiral coil and the secondary spiral coil is equal.

[0011] Preferably, both the primary spiral coil and the secondary spiral coil include at least two sub-coils, forming an alternately arranged first magnetic field region and a second magnetic field region with opposite magnetic field directions, and the magnetic fields of the first magnetic field region and the second magnetic field region cancel each other out.

[0012] Preferably, the winding direction of the sub-coil forming the first magnetic field region is opposite to that of the sub-coil forming the second magnetic field region.

[0013] Preferably, the system also includes a PCB board, wherein the primary spiral coil and the secondary spiral coil are respectively distributed on different copper layers of the PCB board.

[0014] Preferably, the first and last ends of each of the sub-coils connected in series in the primary spiral coil are respectively connected to the positive and negative input voltage terminals of the planar transformer, and the first and last ends of each of the sub-coils connected in series in the secondary spiral coil are respectively connected to the positive and negative output voltage terminals of the planar transformer.

[0015] The above technical solution has the following advantages or beneficial effects:

[0016] 1) By designing the planar transformer so that the magnetic fields generated by each sub-coil in the primary spiral coil cancel each other out, and the magnetic fields generated by each sub-coil in the secondary spiral coil cancel each other out, the magnetic field is actively superimposed and canceled out, which can significantly reduce radiated interference without relying on metal shielding or filtering circuits.

[0017] 2) By designing the planar transformer with the upper and lower sub-coils of the primary and secondary helical coils symmetrically distributed, the differential signal is ensured to have no common-mode conversion, thus eliminating the conduction and radiation problems caused by it from the root, achieving stable transmission of differential signals, and meeting the signal integrity requirements of scenarios such as vehicle CAN bus and differential power supply for ship navigation.

[0018] 3) No additional metal shielding or filtering circuit is required, and there is no loss from additional shielding or filtering components. It is suitable for energy-saving needs in application scenarios such as vehicle range improvement and marine energy. Moreover, there is no risk of poor shielding contact or aging of filtering components, which can meet the reliability requirements of application scenarios such as internal combustion engine systems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the primary helical coil and the secondary helical coil in Embodiment 1 of the present invention;

[0020] Figure 2 This is a schematic diagram of the magnetic field directions of the primary helical coil and the secondary helical coil in Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the primary helical coil and the secondary helical coil in Embodiment 2 of the present invention;

[0022] Figure 4 This is a schematic diagram of the magnetic field directions of the primary helical coil and the secondary helical coil in Embodiment 2 of the present invention;

[0023] Figure 5 This is a schematic diagram of the structure of the primary helical coil and the secondary helical coil in Embodiment 3 of the present invention;

[0024] Figure 6 This is a schematic diagram of the magnetic field directions of the primary and secondary helical coils in Embodiment 3 of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within the scope of the present invention.

[0026] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a planar transformer is provided, such as... Figure 1 As shown, the device includes a primary spiral coil 100 and a secondary spiral coil 200 stacked together. Both the primary spiral coil 100 and the secondary spiral coil 200 include multiple sub-coils connected in series. The magnetic fields generated by each sub-coil in the primary spiral coil 100 cancel each other out, and the magnetic fields generated by each sub-coil in the secondary spiral coil 200 also cancel each other out. The number of each sub-coil in the primary spiral coil 100 and the secondary spiral coil 200 is an even number, and the upper and lower sub-coils of the primary spiral coil 100 and the secondary spiral coil 200 are axially symmetrically distributed.

[0027] Specifically, this embodiment also includes a PCB board. The primary spiral coil 100 and the secondary spiral coil 200 are distributed on different copper layers of the PCB board. Based on this, the stacking direction of the primary spiral coil 100 and the secondary spiral coil 200 is the Z-axis direction perpendicular to the PCB board surface. To facilitate a visual view of the winding method and symmetry relationship of each sub-coil, the primary spiral coil 100 and the secondary spiral coil 200 are shown in a flat arrangement in the attached figures. In practical applications, they are stacked. It is understood that the primary spiral coil 100 and the secondary spiral coil 200 in the attached figures are both rectangular spirals, but this is not a limitation. The specific shapes of the primary spiral coil and the secondary spiral coil can also be circular spirals or other arbitrary shapes.

[0028] Furthermore, the projections of the center point of the primary helical coil 100 and the center point of the secondary helical coil 200 in the stacking direction coincide.

[0029] Specifically, in this embodiment, by designing the projections to coincide at the center point, it is ensured that the sub-coils in the primary spiral coil 100 and the secondary spiral coil 200 are symmetrically distributed radially in space. Therefore, when the interference source is on the left or right sides of the coil, the distances between the sub-coils whose magnetic fields cancel each other out and the interference source are the same. That is, the distance from the interference source to each sub-coil of the primary spiral coil 100 and to each sub-coil of the secondary spiral coil 200 are the same, resulting in optimal magnetic field cancellation. Thus, when the transformer starts working, the generated magnetic fields cancel each other out at the location of the interference source, greatly reducing external radiated interference. Even if the interference source is on the upper or lower sides of the coil, and the distances between the sub-coils whose magnetic fields cancel each other out and the interference source are not exactly the same, external radiated interference can still be largely cancelled out. Furthermore, the coincidence of the center point ensures that the overlapping projections of the primary spiral coil 100 and the secondary spiral coil 200 reach 100%, eliminating the need to reserve extra space for offset coils. This further reduces the volume of the planar transformer for the same power, lowering the installation space requirements.

[0030] In a preferred embodiment of the present invention, the winding directions of the sub-coils of the primary helical coil 100 and the secondary helical coil 200, which are aligned in the stacking direction, are the same or opposite. This is not limited here, and the specific configuration can be determined according to the application scenario. The difference lies in that: if the winding directions of the sub-coils of the primary helical coil 100 and the secondary helical coil 200 are the same, then when the first end of the primary helical coil 100 is connected to the positive input voltage terminal of the planar transformer and the last end is connected to the negative input voltage terminal of the planar transformer, the corresponding secondary helical coil 200 is connected to the positive output voltage terminal of the planar transformer and the last end is connected to the negative output voltage terminal of the planar transformer.

[0031] If the winding directions of the sub-coils of the primary spiral coil 100 and the secondary spiral coil 200, which are aligned in the stacking direction, are opposite, then when the first end of the primary spiral coil 100 is connected to the positive input voltage terminal of the planar transformer and the last end is connected to the negative input voltage terminal of the planar transformer, the first end of the corresponding secondary spiral coil 200 is connected to the negative output voltage terminal of the planar transformer and the last end is connected to the positive output voltage terminal of the planar transformer.

[0032] The following explanation assumes that the winding directions of the sub-coils of the primary spiral coil 100 and the secondary spiral coil 200, which are aligned in the stacking direction, are opposite. The same principle applies when the winding directions are the same. It is sufficient to ensure that the magnetic fields generated by the sub-coils in the primary spiral coil 100 and the sub-coils in the secondary spiral coil 200 cancel each other out; this will not be elaborated further here. Specifically, taking the primary spiral coil 100 (containing upper primary sub-coil 1 and upper primary sub-coil 2) on the upper layer of the PCB, and the secondary spiral coil 200 (containing lower secondary sub-coil 1 and lower secondary sub-coil 2) on the lower layer as an example, if the upper primary sub-coil 1 is wound clockwise, then the lower secondary sub-coil 1 is wound counterclockwise.

[0033] In a preferred embodiment of the present invention, the number of each sub-coil forming the primary helical coil 100 and the secondary helical coil 200 is equal.

[0034] Specifically, in this embodiment, if the primary spiral coil 100 contains 4 sub-coils and the secondary spiral coil 200 also contains 4 sub-coils, the unpaired sub-coils will radiate independently due to the difference in number. If the primary spiral coil 100 has 6 sub-coils and the secondary spiral coil 200 has 4 sub-coils, the extra 2 primary sub-coils will generate independent magnetic fields, resulting in an increase in the intensity of the radiated disturbance field.

[0035] In a preferred embodiment of the present invention, both the primary spiral coil 100 and the secondary spiral coil 200 include at least two sub-coils to form an alternately arranged first magnetic field region and a second magnetic field region with opposite magnetic field directions, and the magnetic fields of the first magnetic field region and the second magnetic field region cancel each other out.

[0036] In a preferred embodiment of the present invention, the winding direction of the sub-coil forming the first magnetic field region is opposite to that of the sub-coil forming the second magnetic field region.

[0037] Specifically, to satisfy the axially symmetric distribution, both the primary helical coil 100 and the secondary helical coil 200 need to contain 2N sub-coils, and when N is an even number, the winding method of each sub-coil is as follows:

[0038] Example 1

[0039] In this embodiment, N is 2. The primary spiral coil 100 and the secondary spiral coil 200 each contain four sub-coils: primary spiral coil 100 contains primary sub-coil 1, primary sub-coil 2, primary sub-coil 3, and primary sub-coil 4. Figure 1As shown, primary sub-coil 1 is wound in a counterclockwise spiral, primary sub-coil 2 is wound in a clockwise spiral, and since the upper and lower sub-coils of primary spiral coil 100 and secondary spiral coil 200 are axially symmetrically distributed, primary sub-coil 3 is wound in a clockwise spiral, and primary sub-coil 4 is wound in a counterclockwise spiral. That is, primary sub-coil 1 and primary sub-coil 2, and primary sub-coil 3 and primary sub-coil 4 are axially symmetrically distributed about the middle horizontal position of primary sub-coil 2 and primary sub-coil 3, that is, the geometric center axis position of primary spiral coil 100.

[0040] Based on this, primary sub-coil 1 and primary sub-coil 2 have opposite magnetic field directions. According to the right-hand rule, the corresponding magnetic field directions are as follows: Figure 2 As shown, where " "This indicates that the direction of the magnetic field is perpendicular to the paper and facing inwards." "" indicates that the magnetic field direction is perpendicular to the paper and outwards. The left side of the figure corresponds to the magnetic field direction generated by each sub-coil in the primary helical coil 100, and the right side corresponds to the magnetic field direction generated by each sub-coil in the secondary helical coil 200.

[0041] The magnetic field of primary coil 1 is perpendicular to the plane of the paper and faces outwards; this can be defined as the first magnetic field region. The magnetic field of primary sub-coil 2 is perpendicular to the plane of the paper and faces inwards; this can be defined as the second magnetic field region. Both coils have the same number of turns, and their magnetic fields cancel each other out.

[0042] Similarly, primary sub-coil 3 and primary sub-coil 4 have opposite magnetic field directions, based on the right-hand rule, such as Figure 2 As shown, the magnetic field direction of the primary coil 3 is perpendicular to the paper and faces inward, which can be defined as the first magnetic field region. The magnetic field direction of the primary sub-coil 4 is perpendicular to the paper and faces outward, which can be defined as the second magnetic field region. Both have the same number of turns, and their magnetic fields cancel each other out.

[0043] For the secondary helical coil 200, the winding direction of each corresponding sub-coil is opposite to that of the corresponding sub-coil of the primary helical coil 100, such as... Figure 1 As shown, in the primary helical coil 100, primary sub-coil 1 is wound counterclockwise, primary sub-coil 2 is wound clockwise, primary sub-coil 3 is wound clockwise, and primary sub-coil 4 is wound counterclockwise. Similarly, in the secondary helical coil 200, secondary sub-coil 1 is wound clockwise, secondary sub-coil 2 is wound counterclockwise, secondary sub-coil 3 is wound counterclockwise, and secondary sub-coil 4 is wound clockwise. The corresponding magnetic field directions are as follows: Figure 2 As shown on the right, it can be seen that magnetic fields in different directions cancel each other out.

[0044] It is understood that this embodiment only shows the winding pattern of primary sub-coil 1 being counterclockwise spiral, primary sub-coil 2 being clockwise spiral, primary sub-coil 3 being clockwise spiral, and primary sub-coil 4 being counterclockwise spiral. When N is 2, the winding patterns of primary sub-coil 1 to primary sub-coil 4 can also be other permutations and combinations, such as the winding patterns of primary sub-coil 1 to primary sub-coil 4 being clockwise spiral, primary sub-coil 2 being counterclockwise spiral, primary sub-coil 3 being counterclockwise spiral, and primary sub-coil 4 being clockwise spiral.

[0045] Furthermore, when N takes the value of other even numbers, the winding method of the corresponding sub-coil follows the same principle, which will not be elaborated here.

[0046] In the primary spiral coil 100 and the secondary spiral coil 200, each contains 2N sub-coils. When N is an odd number greater than 1, the number of turns of at least one sub-coil is proportional to the number of turns of the adjacent sub-coil, so that the magnetic fields of the first magnetic field region and the second magnetic field region cancel each other out.

[0047] Examples of winding methods for each sub-coil are as follows:

[0048] Example 2

[0049] In this embodiment, N is 3. The primary spiral coil 100 and the secondary spiral coil 200 each contain six sub-coils: primary spiral coil 100 contains primary sub-coil 1, primary sub-coil 2, primary sub-coil 3, primary sub-coil 4, primary sub-coil 5, and primary sub-coil 6. Figure 3 As shown, primary sub-coil 1 is wound in a counterclockwise spiral, primary sub-coil 2 and primary sub-coil 3 are wound in a clockwise spiral, and since the upper and lower parts of the primary spiral coil and the secondary spiral coil are axially symmetrically distributed, primary sub-coil 4 and primary sub-coil 5 are wound in a clockwise spiral, and primary sub-coil 6 is wound in a counterclockwise spiral. That is, primary sub-coil 1, primary sub-coil 2 and primary sub-coil 3 are axially symmetrically distributed with primary sub-coil 4, primary sub-coil 5 and primary sub-coil 6 about the middle horizontal position of primary sub-coil 3 and primary sub-coil 4.

[0050] Based on this, for the upper half of the primary helical coil 100, primary sub-coil 2 and primary sub-coil 3 have the same magnetic field direction. According to the right-hand rule, their magnetic field direction is perpendicular to the paper and inwards, and this can be defined as the first magnetic field region. Primary sub-coil 1 has the opposite magnetic field direction to primary sub-coil 2 and primary sub-coil 3. According to the right-hand rule, its magnetic field direction is perpendicular to the paper and outwards, and this can be defined as the second magnetic field region.

[0051] visible, Figure 4In the process, primary sub-coil 2 and primary sub-coil 3 have the same magnetic field direction. Furthermore, since primary sub-coil 2 and primary sub-coil 3 respectively generate the first magnetic field region and primary sub-coil 1 generates the second magnetic field region, the magnetic fields of the first magnetic field region and the second magnetic field region cannot cancel each other out when the number of winding turns is the same. At this time, it is necessary to increase the number of winding turns of primary sub-coil 1. For example, if the number of turns of primary sub-coil 2 and primary sub-coil 3 is n, then the number of winding turns of primary sub-coil 1 is 2n, so as to achieve mutual cancellation of the magnetic fields of the first magnetic field region and the second magnetic field region.

[0052] Similarly, for the lower half of the primary helical coil 100, the number of turns of the primary sub-coil 4 is also increased accordingly, so that the magnetic field region generated by the primary sub-coil 4 can cancel out the magnetic field regions generated by the primary sub-coil 5 and the primary sub-coil 6. The corresponding magnetic field directions are as follows: Figure 4 As shown.

[0053] For the secondary helical coil 200, the winding direction of each corresponding sub-coil is opposite to that of the corresponding sub-coil of the primary helical coil 100, such as... Figure 3 As shown, the primary sub-coil 100 is wound counterclockwise, primary sub-coil 2 is wound clockwise, primary sub-coil 3 is wound clockwise, primary sub-coil 4 is wound clockwise, primary sub-coil 5 is wound clockwise, and primary sub-coil 6 is wound counterclockwise. Similarly, the secondary sub-coil 200 has the following secondary sub-coil winding patterns: secondary sub-coil 1 is wound clockwise, secondary sub-coil 2 is wound counterclockwise, secondary sub-coil 3 is wound counterclockwise, secondary sub-coil 4 is wound counterclockwise, secondary sub-coil 5 is wound counterclockwise, and secondary sub-coil 6 is wound clockwise. The corresponding magnetic field directions are as follows: Figure 4 As shown on the right, it can be seen that magnetic fields in different directions cancel each other out.

[0054] Example 3

[0055] In this embodiment, N is 3. The primary spiral coil 100 and the secondary spiral coil 200 each contain six sub-coils: the primary spiral coil contains primary sub-coil 1, primary sub-coil 2, primary sub-coil 3, primary sub-coil 4, primary sub-coil 5, and primary sub-coil 6. Wherein, as... Figure 5 As shown, primary sub-coil 1 is wound in a counter-clockwise spiral, primary sub-coil 2 in a clockwise spiral, and primary sub-coil 3 in a counter-clockwise spiral. The winding patterns of primary sub-coils 4, 5, and 6 should be axially symmetrical with those of primary sub-coils 1, 2, and 3. The corresponding magnetic field directions are as follows: Figure 6 As shown.

[0056] For the upper half of the primary helical coil 100, Figure 5 In the diagram, primary sub-coil 1 and primary sub-coil 3 have the same magnetic field direction. Based on the right-hand rule, their magnetic field direction is perpendicular to the paper and faces outwards, and this region can be defined as the first magnetic field region. Primary sub-coil 2 has the opposite magnetic field direction to primary sub-coil 1 and primary sub-coil 3. Based on the right-hand rule, its magnetic field direction is perpendicular to the paper and faces inwards, and this region can be defined as the second magnetic field region.

[0057] Furthermore, since primary sub-coil 1 and primary sub-coil 3 respectively generate the first magnetic field region, and primary sub-coil 2 generates the second magnetic field region, the magnetic fields of the first magnetic field region and the second magnetic field region cannot cancel each other out when the number of winding turns is the same. At this time, it is necessary to increase the number of winding turns of primary sub-coil 2. For example, if the number of turns of primary sub-coil 1 and primary sub-coil 3 is n, then the number of winding turns of primary sub-coil 2 is 2n, so as to achieve mutual cancellation of the magnetic fields of the first magnetic field region and the second magnetic field region.

[0058] For the secondary helical coil 200, the winding direction of each corresponding sub-coil is opposite to that of the corresponding sub-coil of the primary helical coil 100, such as... Figure 5 As shown. The corresponding magnetic field direction is as follows. Figure 6 As shown on the right, it can be seen that magnetic fields in different directions cancel each other out.

[0059] It is understood that only two arrangements of the spiral winding methods of primary sub-coils 1 to 6 are shown in Embodiments 2 and 3 above. Other arrangements can also be used, such as the coil winding methods of primary sub-coils 1 to 6 being counterclockwise spiral winding, counterclockwise spiral winding, clockwise spiral winding, clockwise spiral winding, counterclockwise spiral winding, and counterclockwise spiral winding in sequence. The coil winding methods of primary sub-coils 1 to 6 can also be clockwise spiral winding, clockwise spiral winding, counterclockwise spiral winding, counterclockwise spiral winding, clockwise spiral winding, and so on, as long as the magnetic field cancellation and structural symmetry are satisfied. Further details are omitted here.

[0060] In a preferred embodiment of the present invention, the first and last ends of each sub-coil connected in series in the primary spiral coil are respectively connected to the positive and negative terminals of the input voltage of the planar transformer, and the first and last ends of each sub-coil connected in series in the secondary spiral coil are respectively connected to the positive and negative terminals of the output voltage of the planar transformer.

[0061] Specifically, the tail end of primary sub-coil 1 (the end furthest from the input pin) is connected to the head end of primary sub-coil 2 (the end closest to the input pin), the tail end of primary sub-coil 2 is connected to the head end of primary sub-coil 3, and so on, forming a series circuit; the starting point of this series circuit, i.e. the head end of primary sub-coil 1, is used as the positive input voltage terminal of the planar transformer, and the ending point, i.e. the tail end of primary sub-coil 4, is used as the negative input voltage terminal.

[0062] Similarly, the sub-coils connected in series in the secondary helical coil adopt a completely symmetrical, end-to-end connection structure with the primary coil: the end of secondary sub-coil 1 is connected to the beginning of secondary sub-coil 2, the end of secondary sub-coil 2 is connected to the beginning of secondary sub-coil 3, and so on, forming a series circuit. When the winding directions of the sub-coils of the primary helical coil 100 and the secondary helical coil 200 are the same when aligned in the stacking direction, the starting point of the series circuit, i.e., the beginning of secondary sub-coil 1, serves as the positive terminal of the output voltage, and the ending point, i.e., the end of secondary sub-coil 4, serves as the negative terminal of the output voltage. When the winding directions of the sub-coils of the primary helical coil 100 and the secondary helical coil 200 are opposite when aligned in the stacking direction, the starting point of the series circuit, i.e., the beginning of secondary sub-coil 1, serves as the negative terminal of the output voltage, and the ending point, i.e., the end of secondary sub-coil 4, serves as the positive terminal of the output voltage.

[0063] Since both the primary and secondary spiral coils contain an even number of sub-coils, and are symmetrically distributed vertically, the positive and negative terminals of the input voltage and the output voltage can be arbitrarily interchanged. For example, if there are 4 sub-coils, the positive terminal of the input voltage can be connected to the tail end of the primary sub-coil 4 and the negative terminal to the head end of the primary sub-coil 1. The positive terminal of the output voltage can be connected to the tail end of the secondary sub-coil 4 and the negative terminal to the head end of the secondary sub-coil 1.

[0064] When the input voltage polarity is reversed, the current direction in the primary spiral coil circuit reverses, that is, it changes from primary sub-coil 1→4 to primary sub-coil 4→1. The magnetic field direction generated by each sub-coil reverses synchronously, and the original "×" perpendicular to the paper and pointing inwards becomes an outward "×". “”, the original Chaowai The "×" is changed to an inward-facing "×". Furthermore, because the sub-coils are symmetrically distributed along their upper and lower axes, and the winding directions of the symmetrical sub-coils are opposite, even after the current direction is reversed, the magnetic fields of the symmetrical sub-coils remain opposite in direction and equal in amplitude. The principle of polarity exchange for the secondary spiral coil is completely consistent with that of the primary coil, and the amplitude and phase of the output voltage are unaffected. It is evident that regardless of the current direction, the reverse-wound symmetrical sub-coils can always form a pair of opposite magnetic fields, ensuring a stable cancellation effect. This provides great convenience for installation and maintenance in practical applications, avoiding the risk of coil burnout or equipment failure caused by reversing the positive and negative terminals of a traditional transformer. If the positive and negative terminals are mistakenly reversed during on-site maintenance, the transformer will not be damaged, and the magnetic field cancellation effect will be consistent with the normal connection, preventing equipment downtime due to maintenance errors, improving system reliability, and also avoiding the generation of common-mode signals that lead to conducted radiation.

[0065] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A planar transformer, characterized by The primary spiral coil and the secondary spiral coil are arranged in a stack, each of the primary spiral coil and the secondary spiral coil comprises a plurality of sub-coils connected in series, the magnetic fields generated by each of the sub-coils in the primary spiral coil cancel each other out, and the magnetic fields generated by each of the sub-coils in the secondary spiral coil cancel each other out; The number of each of the sub-coils included in the primary spiral coil and the secondary spiral coil is an even number greater than 2, and the sub-coils in the upper and lower parts of the primary spiral coil are distributed in axial symmetry along a middle horizontal plane perpendicular to the stacking direction, and the sub-coils in the upper and lower parts of the secondary spiral coil are distributed in axial symmetry along a middle horizontal plane perpendicular to the stacking direction; The sub-coils in the upper half of the primary spiral coil form first magnetic field regions and second magnetic field regions arranged alternately and having opposite magnetic field directions, and the magnetic fields of the first magnetic field regions and the second magnetic field regions cancel each other out; The sub-coils in the upper half of the secondary spiral coil form first magnetic field regions and second magnetic field regions arranged alternately and having opposite magnetic field directions, and the magnetic fields of the first magnetic field regions and the second magnetic field regions cancel each other out; The sub-coils in the lower half of the primary spiral coil form first magnetic field regions and second magnetic field regions arranged alternately and having opposite magnetic field directions, and the magnetic fields of the first magnetic field regions and the second magnetic field regions cancel each other out; The sub-coils in the lower half of the secondary spiral coil form first magnetic field regions and second magnetic field regions arranged alternately and having opposite magnetic field directions, and the magnetic fields of the first magnetic field regions and the second magnetic field regions cancel each other out.

2. The planar transformer according to claim 1, characterized in that The projections of the center points of the primary spiral coil and the secondary spiral coil on the stacking direction coincide.

3. The planar transformer according to claim 1, characterized in that, The number of each of the sub-coils forming the primary spiral coil and the secondary spiral coil is equal.

4. The planar transformer of claim 1, wherein, The winding directions of the sub-coils forming the first magnetic field regions and the sub-coils forming the second magnetic field regions are opposite.

5. The planar transformer of claim 1, wherein, A PCB board is further included, and the primary spiral coil and the secondary spiral coil are respectively distributed on different copper layers of the PCB board.

6. The planar transformer of claim 1, wherein, The first and last ends of each of the sub-coils connected in series in the primary spiral coil are respectively connected to the positive and negative poles of an input voltage of a planar transformer, and the first and last ends of each of the sub-coils connected in series in the secondary spiral coil are respectively connected to the positive and negative poles of an output voltage of the planar transformer.

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