A magnetic integrated converter for fixed switching frequency resonant conversion
By employing a UI-type magnetic core and a multi-layer PCB structure in the LLC DCX converter, with staggered windings and a GND layer, a highly integrated magnetic converter is achieved, solving the problem of low integration, improving power density, and reducing losses.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2025-11-18
- Publication Date
- 2026-07-21
AI Technical Summary
Existing LLC DCX converters have low integration density in magnetic integration, resulting in large converter area, low power density, and especially output losses exceeding input losses.
It adopts a UI-type magnetic core and a multi-layer PCB board structure, with the primary and secondary windings arranged alternately and a GND layer set between the winding layers to realize a highly integrated magnetic converter. The secondary winding is rectangular and the primary winding has 4 turns. Electrical connection is achieved through blind holes and vias. It integrates primary transistors, resonant capacitors, input capacitors and driver chips.
It significantly reduces converter area, increases power density, reduces losses, and achieves higher integration and power density, making it suitable for applications with high power density requirements.
Smart Images
Figure CN121483826B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of converter technology, specifically relating to a magnetic integrated converter for fixed switching frequency resonant conversion. Background Technology
[0002] Series resonant converters (LLCs) offer advantages such as high efficiency and simple control, making them widely used in data centers, energy storage, and photovoltaics. One application of LLC converters involves a fixed switching frequency, ensuring the LLC always operates at its resonant point to fully leverage its efficiency advantages. This is used in fixed-ratio scenarios and is known as a DC transformer (DCX). In many converter applications, space for power module installation is limited, thus requiring high power density in LLC DCX converter modules. PCB planar transformers use the copper layers of a PCB instead of the Litz wires of traditional wire-wound transformers, offering advantages such as lower height and higher integration, enabling higher power density. An LLC DCX based on a PCB planar transformer consists of magnetic components and other components. The magnetic components refer to the planar transformer itself, while other components include primary-side transistors, output capacitors, resonant capacitors, synchronous rectifier transistors, and driver chips.
[0003] To improve the power density of LLC DCX, existing technologies have focused on the research and application of magnetic integration based on PCB planar transformers. Magnetic integration refers to integrating magnetic components onto the transformer, primarily achieved through: 1) using PCB planar windings; and 2) integrating other components onto the magnetic components. In existing magnetic integration methods, the output capacitor and synchronous rectifier transistor (SR) are integrated onto the transformer, reducing the converter's projected area and thus increasing power density.
[0004] However, in existing technologies, because traditional PCB windings are stacked vertically, the PCB surface layer is either the primary winding or the secondary winding. Since primary windings can only be connected to primary windings, and secondary windings can only be connected to secondary windings, when the surface layer of a PCB planar transformer is the primary winding, primary windings (including primary transistors, resonant capacitors, input capacitors, etc.) must be integrated onto the transformer. Similarly, when the surface layer of a PCB planar transformer is the secondary winding, secondary windings (including synchronous rectifier transistors, output capacitors, etc.) must be integrated onto the transformer.
[0005] Since LLC DCX converters are generally buck converters, the output current is greater than the input current. This results in greater end-point losses at the output (secondary side) than at the input (primary side) (end-point losses refer to the losses at the connection points between the windings and devices). Integrating devices onto the transformer not only increases power density but also reduces losses. Therefore, secondary-side devices are typically integrated onto the transformer to further reduce end-point losses. In traditional magnetic integration schemes, primary-side transistors, resonant capacitors, input capacitors, and driver chips cannot be integrated onto the windings, leading to low converter integration.
[0006] Therefore, a magnetic integrated converter with higher integration, smaller converter area, and higher power density is needed to solve the above-mentioned technical problems. Summary of the Invention
[0007] This invention provides the following technical solution: a magnetic integrated converter for fixed switching frequency resonant conversion, comprising: a magnetic core and a PCB board, wherein the magnetic core is a UI-type magnetic core and the PCB board is a multilayer board; the PCB board comprises, from top to bottom, a first secondary winding layer, a first primary winding layer, a first GND layer, a second GND layer, a second primary winding layer, and a second secondary winding layer; the first secondary winding layer and the second secondary winding layer are rectangular, the first GND layer and the second GND layer are closed annular, the first primary winding layer and the second primary winding layer are rectangular and have core post through holes; the first secondary winding layer and the second secondary winding layer are located between the core posts of the magnetic core, the annular first GND layer and the second GND layer are sleeved outside the core posts of the magnetic core, and the core post through holes of the first primary winding layer and the second primary winding layer are respectively sleeved on the core posts of the magnetic core.
[0008] The first and second secondary winding layers are respectively equipped with an output capacitor and a synchronous rectifier transistor, while the first and second primary winding layers are respectively equipped with an input capacitor, a primary transistor, and a resonant capacitor. The first secondary winding layer is electrically connected to the first GND layer, and the second secondary winding layer is electrically connected to the second GND layer, thus forming a circuit on the secondary side of the transformer; the first primary winding layer is electrically connected to the second primary winding layer, thus connecting the two primary winding layers in series.
[0009] Preferably, the first primary winding layer and the second primary winding layer are further provided with a synchronous rectification drive chip and a primary driving chip, respectively.
[0010] More preferably, the primary-side driving chip is located next to the primary-side transistor, and the synchronous rectification driving chip is located next to the synchronous rectification transistor.
[0011] Preferably, both the first primary winding layer and the second primary winding layer are provided with blind holes, and the primary transistor and resonant capacitor are electrically connected to the primary winding through the blind holes.
[0012] Preferably, the first secondary winding layer, the first primary winding layer, the first GND layer, the second GND layer, the second primary winding layer, and the second secondary winding layer are all provided with vias, which are located in the same position and are used for electrical connection between the layers.
[0013] Preferably, the primary winding of the converter has 4 turns and the secondary winding has 1 turn.
[0014] The beneficial effects of this invention are: This invention significantly reduces the converter area and thus increases the converter's power density by using a more highly integrated magnetic converter. The transformer surface winding area of this invention provides space for the placement of devices (including power devices, driver chips, resonant capacitors, etc.), whereas in traditional integrated schemes, the entire surface of the transformer winding area is covered by the winding, forcing the primary-side power devices, driver chips, and resonant capacitors to be placed outside the winding area, which occupies additional space. A smaller footprint translates to higher power density; therefore, this invention achieves higher power density. With the same winding area, this invention achieves higher integration and a smaller total converter footprint. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the device arrangement of a magnetic integrated converter for fixed switching frequency resonant conversion according to the present invention; Figure 2 This is a diagram of the winding structure of the present invention; Figure 3 This is a schematic diagram of the area where the device can be arranged according to the present invention; Figure 4 This is a measured waveform diagram of the present invention; Figure 5 The flowchart shows the implementation of the DC-DC converter control method, which compares the effects of the present invention with those of the prior art; where a is the prior art converter and b is the converter of the present invention.
[0016] In the diagram: 1. Magnetic core; 2. PCB board; 3. First secondary winding layer; 4. First primary winding layer; 5. First GND layer; 6. Second GND layer; 7. Second primary winding layer; 8. Second secondary winding layer; 9. Output capacitor; 10. Synchronous rectifier transistor; 11. Input capacitor; 12. Primary transistor; 13. Resonant capacitor; 14. Synchronous rectifier driver chip; 15. Primary driver chip. Detailed Implementation
[0017] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0018] like Figures 1-5 As shown, the magnetic integrated converter proposed in this embodiment is as follows: Figure 1 As shown, compared to traditional magnetic integration technology which only integrates the synchronous rectifier transistor and output capacitor onto the transformer, the proposed magnetic integration technology integrates the primary-side transistor, resonant capacitor, input capacitor, and driver chip onto the transformer.
[0019] Figure 1 An LLC DCX converter based on the planar transformer magnetic integration technology proposed in this patent is demonstrated. The area within the red dashed line represents the transformer region of PCB board 2, where the primary transistor 12, input capacitor 11, resonant capacitor 13, synchronous rectifier transistor 10, output capacitor 9, and driver chip are all integrated onto the transformer. The magnetic core 1 of the planar transformer is a UI-type magnetic core, characterized by… Figure 1 The horizontal cross-section of the transformer has two circular interfaces. The primary-side transistor 12 and input capacitor 11 are placed on the left side of the transformer. The resonant capacitor 13 is placed on the right side of the transformer. The synchronous rectifier transistor 10 and output capacitor 9 are placed between the two core pillars of the UI core 1, located on the upper and lower sides respectively. The primary-side driver chip 15 and the synchronous rectifier driver chip 14 are located next to the primary-side transistor 12 and the synchronous rectifier transistor 10, respectively.
[0020] like Figure 2 As shown. In this embodiment, the PCB board 2 has a total of 6 winding layers. Layers 1 and 6 are the secondary windings, which are rectangular in shape and have the synchronous rectifier transistor 10 and output capacitor 9 placed on them. Layers 3 and 4 are GND layers, which are closed loops connected to the secondary windings via vias, forming a circuit on the secondary side of the transformer. Layers 2 and 5 are the primary windings, connected by vias. The vias connect the two primary windings in series. The primary winding has 4 turns, and the secondary winding has 1 turn, resulting in a transformer turns ratio of 4:1. The secondary winding is rectangular, and the GND layer is a closed loop. The rectangular primary winding and the vias connecting the layers optimize the spatial layout and improve magnetic coupling efficiency.
[0021] During the winding fabrication process, high-precision PCB manufacturing technology is employed to ensure the dimensional and positional accuracy of each winding layer, thereby guaranteeing the stable and reliable electrical performance of the transformer. Furthermore, the insulation treatment between windings is also crucial, utilizing high-temperature and high-voltage resistant insulation materials to ensure that no breakdown occurs between windings under high-temperature and high-voltage environments, thus guaranteeing the safe operation of the converter.
[0022] In addition to the winding structure, this embodiment also emphasizes the layout and heat dissipation design of the components. Heat-generating components such as the primary-side transistor 12 and resonant capacitor 13 are rationally arranged around the transformer for easy heat dissipation. Simultaneously, efficient heat dissipation structures, such as heat sinks and fans, are employed to ensure that the converter maintains a stable temperature under prolonged high-load operation, extending its service life.
[0023] In practical applications, the magnetically integrated converter of this embodiment exhibits significant advantages. Its highly integrated design results in a smaller and lighter converter, facilitating installation and maintenance. Simultaneously, its high power density allows the converter to output greater power within the same volume, meeting the needs of applications with high power density requirements. Furthermore, the converter possesses excellent dynamic response characteristics and steady-state accuracy, ensuring the stability and accuracy of the output voltage and current.
[0024] Because the secondary winding is rectangular, it does not occupy the entire surface area of the secondary transformer. A portion of the transformer surface can be directly connected to the primary windings of layers 2 and 5. Specifically, primary transistor 12 is connected to the primary winding via a blind via, and resonant capacitor 5 is also connected to the primary winding via a blind via. Figure 4 The waveforms of the LLC DCX converter are shown, indicating that the converter is working normally.
[0025] In summary, this invention significantly reduces the converter area by using a more integrated magnetic converter, thereby increasing the converter's power density.
[0026] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A magnetically integrated converter for fixed-switching-frequency resonant conversion, characterized in that, include: Magnetic core (1) and PCB board (2), wherein the magnetic core (1) is a UI type magnetic core and the PCB board (2) is a multilayer board; The PCB board (2) includes, from top to bottom, the following layers in sequence: a first secondary winding layer (3), a first primary winding layer (4), a first GND layer (5), a second GND layer (6), a second primary winding layer (7), and a second secondary winding layer (8); the first secondary winding layer (3) and the second secondary winding layer (8) are rectangular, the first GND layer (5) and the second GND layer (6) are closed rings, the first primary winding layer (4) and the second primary winding layer (7) are rectangular and have core column through holes; the first secondary winding layer (3) and the second secondary winding layer (8) are located between the core columns of the magnetic core (1), the rings of the first GND layer (5) and the second GND layer (6) are sleeved outside the core columns of the magnetic core (1), and the core column through holes of the first primary winding layer (4) and the second primary winding layer (7) are respectively sleeved on the core columns of the magnetic core (1); The first secondary winding layer (3) and the second secondary winding layer (8) are provided with an output capacitor (9) and a synchronous rectifier transistor (10), and the first primary winding layer (4) and the second primary winding layer (7) are provided with an input capacitor (11), a primary transistor (12) and a resonant capacitor (13). The first secondary winding layer (3) is electrically connected to the first GND layer (5), and the second secondary winding layer (8) is electrically connected to the second GND layer (6); the first primary winding layer (4) is electrically connected to the second primary winding layer (7). Both the first primary winding layer (4) and the second primary winding layer (7) are provided with blind holes, and the primary transistor (12) and the resonant capacitor (13) are electrically connected to the primary winding through the blind holes; The first secondary winding layer (3), the first primary winding layer (4), the first GND layer (5), the second GND layer (6), the second primary winding layer (7), and the second secondary winding layer (8) are all provided with vias. The vias are in the same position and are used for electrical connection between the layers.
2. The magnetic integrated converter for fixed switching frequency resonant conversion according to claim 1, characterized in that, Both the first primary winding layer (4) and the second primary winding layer (7) are provided with a synchronous rectification drive chip (14) and a primary driving chip (15).
3. A magnetic integrated converter for fixed switching frequency resonant conversion according to claim 2, characterized in that, The primary-side driving chip (15) is located next to the primary-side transistor (12), and the synchronous rectification driving chip (14) is located next to the synchronous rectification transistor (10).
4. A magnetic integrated converter for fixed switching frequency resonant conversion according to claim 1, characterized in that, The primary winding of the converter has 4 turns, and the secondary winding has 1 turn.