Planar transformer temperature rise optimization simulation calculation method

Abstract

The invention provides a planar transformer temperature rise optimization simulation calculation method, which relates to the technical field of magnetic device simulation design, and mainly comprises the following steps: establishing a planar transformer equal ratio 3D model, solving a planar transformer winding impedance matrix, solving primary and secondary side waveform information of a planar transformer under specified working conditions, and solving the loss of the planar transformer. And solving electromagnetic-thermal bidirectional coupling temperature rise of the planar transformer. According to the method, based on excitation-loss-temperature rise coupling solution, the temperature rise of the planar transformer can be quickly and accurately simulated.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic device simulation design, and in particular to a planar transformer temperature rise optimization simulation calculation method. Background Art

[0002] In recent years, my country's aerospace, communications, and new energy sectors have experienced rapid development, and these industries are placing increasing demands on power supply performance. As the core power device in a power supply, the transformer performs functions such as energy transfer, electrical isolation, and impedance matching. The quality of its design directly impacts performance indicators such as the power supply's overall efficiency, stability, and power density. Planar transformers, as third-generation transformers, utilize PCB windings instead of traditional enameled wire, improving inter-winding coupling and power density. Automated PCB winding production also effectively avoids assembly errors associated with traditional manual winding, ensuring consistent product performance.

[0003] However, the design and production of planar transformers currently face many challenges. For example, the high power density characteristic places stricter requirements on the heat dissipation and temperature rise of planar transformers, and there is currently no systematic method to predict the losses and temperature rise of planar transformers under specified operating conditions. Furthermore, the PCB winding production cycle of planar transformers is long, the process is complex, and the cost is high. The physical verification process during the R&D stage consumes a lot of time and financial resources.

[0004] In response to the above problems, many researchers are currently using computer-aided design to provide solutions. China Invention Patent Publication No. CN109241586A discloses a transformer loss solution method based on Ansys Maxwell eddy current field solver. This method uses a simplified transformer model and an electrical steel loss model to simulate and solve the core loss. However, the invention does not involve the solution of winding loss and temperature rise during normal operation of the transformer; China Invention Patent Publication No. CN109255192A discloses a transformer loss solution based on Ansys Maxwell eddy current field solver. Fluent's oil-immersed transformer temperature rise solution method uses core loss and winding loss as inputs to perform a bidirectional temperature field-flow field coupling solution, achieving relatively accurate transformer temperature rise prediction. However, the invention does not detail the solution process for core loss and winding loss. Chinese invention patent publication number CN108388744A discloses a transformer steady-state thermal effect simulation method. This method uses the transformer body power consumption density as the heat load to solve the transformer steady-state temperature rise. This invention initially achieves a one-way electromagnetic-thermal coupling solution for the transformer, but does not consider the impact of factors such as power supply topology, load conditions, and temperature-dependent changes in material properties on the transformer temperature rise solution results.

[0005] In summary, for the temperature rise simulation problem of planar transformers, there is an urgent need to develop an accurate temperature rise simulation method based on the excitation-loss-temperature rise coupling solution.

[0006] The Ansys Workbench 2022R1 platform provides solutions for complex multi-physics field coupling, and its collaborative simulation environment can effectively solve the above problems. In addition, Ansys Workbench 2022R1 comes with a CAD interface module that is compatible with 3D proportional model files in various formats, providing a way to accurately solve the temperature rise and structural optimization of planar transformers. Summary of the Invention

[0007] In view of the above problems, the purpose of the present invention is to provide a planar transformer temperature rise optimization simulation calculation method, which is based on the excitation-loss-temperature rise coupling solution and can quickly and accurately simulate the temperature rise of the planar transformer.

[0008] The technical solution adopted by the present invention to achieve its invention object is a planar transformer temperature rise optimization simulation calculation method, comprising the following steps:

[0009] S1. According to the actual size of the planar transformer, a proportional 3D model of the planar transformer is parametrically established in the 3D modeling software;

[0010] S2. Use the eddy current field solver in Maxwell to solve the impedance matrix of the planar transformer at each operating frequency point;

[0011] S3. Build a main power module circuit model in Twin Builder, import the impedance matrix obtained in step S2 as a reduced-order model of the planar transformer into the main power module circuit model, and solve the steady-state excitation waveform information of the primary and secondary sides of the planar transformer under specified working conditions;

[0012] S4. After importing the 3D model and completing the material definition, the obtained steady-state excitation waveform information is set as the primary-secondary excitation, and the planar transformer steady-state loss is solved in the Maxwell eddy current field solver.

[0013] S5. Import the solved steady-state loss results into icepak as thermal excitation. At the same time, add feedback iteration settings to perform electromagnetic-thermal bidirectional coupling solution to obtain the temperature distribution cloud map of the planar transformer during steady-state operation.

[0014] Furthermore, the parameterized dimensions of the planar transformer in step S1 include winding width, height, spacing, and substrate thickness.

[0015] Furthermore, the operating frequency points in step S2 include actual operating frequency points of the planar transformer.

[0016] Furthermore, the designated operating condition in step S3 is a series-parallel resonant operating condition.

[0017] Furthermore, before importing the 3D model and completing the material definition in step S4, the temperature dependency of the material properties is also set.

[0018] Furthermore, the temperature dependency is defined by one of three methods: compiling a function expression, importing a data set, and inputting quadratic equation coefficients.

[0019] Furthermore, the steady-state loss in step S4 includes the core loss and winding loss of the planar transformer during steady-state operation.

[0020] Furthermore, the specific steps of step S5 are:

[0021] S5.1. Transfer the 3D model to Icepak and set the material-related thermal properties for thermal simulation.

[0022] S5.2. Manually mesh the planar transformer using a multi-level meshing method.

[0023] S5.3. Set appropriate boundary conditions based on the actual working environment of the planar transformer, enable the thermal radiation model, and set the fluid flow pattern and gravity direction.

[0024] S5.4. Import the planar transformer steady-state loss obtained in step 4 into Icepak as a thermal load. At the same time, check the temperature feedback option, set the appropriate maximum number of temperature feedback iterations and iteration increment, perform electromagnetic-thermal bidirectional coupling solution, and obtain the temperature distribution cloud map of the planar transformer during steady-state operation.

[0025] Furthermore, after step S5, a physical test and verification of the planar transformer is also carried out. The specific steps are: making a physical planar transformer, applying the steady-state excitation waveform voltage solved in step S3 to the primary and secondary sides of the physical planar transformer as voltage excitation, using a thermocouple to record the temperature of the specified point, and comparing the measured data with the simulation results to verify the feasibility of the simulation method.

[0026] The beneficial effects of the present invention are:

[0027] The planar transformer structure is optimized using parametric modeling, which greatly shortens the modeling cycle.

[0028] Using a reduced-order planar transformer model in Twin Builder to solve the primary and secondary side excitation waveforms, this significantly shortens solution time, reduces memory usage, and improves solution efficiency compared to traditional Maxwell and Twin Builder co-simulation.

[0029] By building a power module circuit, you can obtain the current and voltage waveforms of the primary and secondary sides of a planar transformer, accurately solving for core and winding losses under any specified operating conditions. Using Twin Builder to build the power module circuit, you can set the parasitic parameters of electronic components such as MOSFETs and diodes, as well as the load conditions and operating frequency. This simulates the primary and secondary current and voltage waveforms of the planar transformer under actual operating conditions and uses this information as winding excitation to accurately solve for losses.

[0030] The influence of material temperature characteristics on the temperature rise solution is taken into account. In this invention, the temperature correlation of material properties is set. The core loss and winding loss are used as thermal loads to solve the temperature rise of the planar transformer. The temperature rise solution is then returned to the loss solution module. Since temperature changes will affect the material properties, the system will perform a secondary iterative solution for the loss and temperature rise. The above steps are iterated repeatedly until the solution converges or the number of iterations reaches the upper limit set by the user, and an accurate solution for the temperature rise of the planar transformer based on electromagnetic-thermal bidirectional coupling is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a method according to an embodiment of the present invention;

[0032] Figure 2 3D model of a planar transformer according to an embodiment of the present invention and exploded views of different stacking methods;

[0033] Figure 3 The power module circuit model built in Twin Builder in the embodiment of the present invention;

[0034] Figure 4 The simulation results of the steady-state waveforms of the primary and secondary winding currents and voltages in the embodiment of the present invention are as follows;

[0035] Figure 5 The results of solving the core loss and winding loss of the embodiment of the present invention are as follows;

[0036] Figure 6 This is a temperature distribution cloud diagram of a planar transformer according to an embodiment of the present invention;

[0037] Figure 7 The figure is a comparison chart of the simulation results and the actual test results of the embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Figure 1 A specific implementation of the planar transformer temperature rise optimization simulation calculation method of the present invention is shown, including the following steps:

[0040] S1. Establish a proportional three-dimensional model of the planar transformer: that is, according to the actual size of the planar transformer, establish a proportional 3D model of the planar transformer parameterized in the three-dimensional modeling software; the parameterized dimensions include winding width, height, spacing and substrate thickness; the multilayer board can be assembled in different stacking methods to obtain 3D model files of different planar transformer structural schemes. In this embodiment, the planar transformer core is a flat core; the PCB primary and secondary windings each have 9 turns, the winding width is 2 to 5mm, the height is 35 to 210μm, and the substrate thickness is 200 to 400μm; there are three stacking methods, from top to bottom, they are PPPSSSC, PPSPSSC, and PPSPSSC, where P is the primary winding, S is the secondary winding, and C is the connecting layer winding. The three stacking models are as follows Figure 2 shown.

[0041] S2. Solve the winding impedance matrix: Add the Maxwell 3D submodule in Workbench, select the eddy current field solver as the solution type, import the model and assign material properties, set the primary and secondary sides to sinusoidal excitation for swept frequency solution, and obtain the impedance matrix of the planar transformer at each operating frequency point; the swept frequency solution setting includes the operating frequency band of the planar transformer. In this embodiment, the primary side of the transformer is applied with a sinusoidal wave excitation with an amplitude of 1A, a frequency of 50kHz to 250kHz, and a step size of 10kHz. The secondary side is set to short circuit for swept frequency solution.

[0042] S3. Solve the waveform information of the primary and secondary sides of the planar transformer under specified working conditions: Add the TwinBuilder submodule in Workbench, set the solution mode to transient solution, and build the following in Twin Builder: Figure 3 The main power module circuit model of the full-bridge LLC converter shown in FIG is used. The impedance matrix obtained in step S2 is imported into the main power module circuit model as the reduced-order model of the planar transformer. An appropriate solution step size and solution time are set to solve the primary and secondary windings of the planar transformer under the series-parallel resonant working condition. The primary and secondary steady-state excitation waveforms, i.e., the waveform information of the current and voltage, are solved, as shown in FIG. Figure 4 shown.

[0043] S4. Planar transformer loss solution: Add a new Maxwell 3D submodule in Workbench, select the eddy current field solver as the solution type, set the temperature dependence of the material properties, and define the temperature dependence by compiling a function expression, importing a data set, or entering a quadratic equation coefficient. After importing the model and completing the material definition, set the steady-state excitation waveform information obtained in step S3 as the primary-secondary side excitation, and solve the planar transformer steady-state loss in the Maxwell eddy current field solver as follows: Figure 5 shown.

[0044] S5. Solve the electromagnetic-thermal bidirectional coupled temperature rise of the planar transformer: Add the Icepak submodule in Workbench, select the steady-state solver as the solution type, and solve the temperature rise of the planar transformer. The specific solution steps are as follows:

[0045] S5.1. Transfer the 3D model to Icepak and set the material-related thermal properties for thermal simulation.

[0046] S5.2. Manually mesh the planar transformer using a multi-level meshing method.

[0047] S5.3. Set appropriate boundary conditions based on the actual working environment of the planar transformer, set the ambient temperature to 20°C, enable the thermal radiation model, and set the fluid flow pattern and gravity direction.

[0048] S5.4. Import the planar transformer steady-state loss obtained in step 4 into Icepak as a thermal load. At the same time, check the temperature feedback option, set the appropriate maximum number of iterations and iteration increments for temperature feedback solution, perform electromagnetic-thermal bidirectional coupling solution, and obtain the temperature distribution cloud diagram of the planar transformer during steady-state operation as shown below. Figure 6 shown.

[0049] S6. Conduct physical test and verification of the planar transformer. The specific steps are: make a physical planar transformer, give the steady-state excitation waveform voltage obtained in step S3 to the primary and secondary sides of the physical planar transformer as voltage excitation, wait until the planar transformer works stably, use a thermocouple to record the temperature of the specified point, and compare the measured data with the simulation results. The comparison results are as follows: Figure 7 The measured data and simulation results are shown in the following table:

[0050]

[0051] As can be seen from the table, in this embodiment, the error between the temperature rise results of each test point and the simulation results is less than 8%, which verifies the feasibility of the present invention.

Claims

1. A planar transformer temperature rise optimization simulation calculation method, characterized in that: The steps include: S1. According to the actual size of the planar transformer, a proportional 3D model of the planar transformer is parametrically established in the 3D modeling software; S2. Use the eddy current field solver in Maxwell to solve the impedance matrix of the planar transformer at each operating frequency point; S3. Build a main power module circuit model in Twin Builder, import the impedance matrix obtained in step S2 as a reduced-order model of the planar transformer into the main power module circuit model, and solve the steady-state excitation waveform information of the primary and secondary sides of the planar transformer under specified working conditions; S4. After importing the 3D model and completing the material definition, the obtained steady-state excitation waveform information is set as the primary-secondary side excitation, and the steady-state loss of the planar transformer is solved in the Maxwell eddy current field solver; S5. Import the solved steady-state loss results into icepak as thermal excitation. At the same time, add feedback iteration settings to perform electromagnetic-thermal bidirectional coupling solution to obtain the temperature distribution cloud map of the planar transformer during steady-state operation.

2. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: The parameterized dimensions of the planar transformer in step S1 include winding width, height, spacing, and substrate thickness.

3. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: The operating frequency points mentioned in step S2 include actual operating frequency points of the planar transformer.

4. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: The designated operating condition in step S3 is a series-parallel resonant operating condition.

5. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: Before importing the 3D model and completing the material definition in step S4, the temperature dependency of the material properties should also be set.

6. The planar transformer temperature rise optimization simulation calculation method according to claim 5, characterized in that: The temperature dependence is defined by one of three methods: compiling a function expression, importing a data set, or inputting quadratic equation coefficients.

7. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: The steady-state loss in step S4 includes the core loss and winding loss of the planar transformer during steady-state operation.

8. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: The specific steps of step S5 are: S5.

1. Transfer the 3D model to Icepak and set the material-related thermal properties for thermal simulation. S5.

2. Manually mesh the planar transformer using a multi-level meshing method. S5.

3. Set appropriate boundary conditions based on the actual working environment of the planar transformer, enable the thermal radiation model, and set the fluid flow pattern and gravity direction. S5.

4. Import the planar transformer steady-state loss obtained in step 4 into Icepak as a thermal load. At the same time, check the temperature feedback option, set the appropriate maximum number of temperature feedback iterations and iteration increment, perform electromagnetic-thermal bidirectional coupling solution, and obtain the temperature distribution cloud map of the planar transformer during steady-state operation.

9. The planar transformer temperature rise optimization simulation calculation method according to claim 1, characterized in that: After step S5, a physical test and verification of the planar transformer is also carried out. The specific steps are: making a physical planar transformer, applying the steady-state excitation waveform voltage solved in step S3 to the primary and secondary sides of the physical planar transformer as voltage excitation, using a thermocouple to record the temperature of the specified point, and comparing the measured data with the simulation results to verify the feasibility of the simulation method.

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