High power density four-magnetic leg array decoupled magnetic integrated transformer based on active-clamp isolated weinberg

Abstract

The application provides a high-power-density four-magnetic-column array decoupling magnetic integrated transformer based on an active clamping isolation type Weinberg, which comprises a four-magnetic-column array type planar magnetic integrated core, the magnetic core adopts a rectangular array layout without a center magnetic column, and is composed of four equal-section edge magnetic columns and upper and lower rectangular magnetic yokes to form a closed magnetic circuit frame; the four edge magnetic columns are distributed in a square equidistant array, the magnetic columns and the magnetic yokes are integrally formed, and uniform air gaps are formed on the end faces of the magnetic columns; the magnetic integrated transformer is integrated with a push-pull transformer and a flyback transformer, the push-pull transformer has two groups of symmetrical primary and secondary winding groups, the flyback transformer has a primary and secondary winding group, and each winding group is wound on the four-magnetic-column array type planar magnetic integrated core through a PCB winding mode; by setting the number of turns of each winding group and the air gap magnetic resistance of each magnetic column, the push-pull transformer and the flyback transformer are magnetically decoupled on the same magnetic core.

Description

Technical Field

[0001] This invention belongs to the field of transformer technology, and in particular relates to a high power density four-pillar array decoupled magnetic integrated transformer based on active clamp isolation Weinberg. Background Technology

[0002] Isolated Weinberg topologies are widely used in high-power power supply systems due to their advantages such as continuous input and output current and high equivalent operating frequency. However, traditional isolated Weinberg circuits have the following problems: First, the turn-off voltage spikes of the switching transistors caused by transformer leakage inductance affect system reliability; second, the hard-switching operating mode limits the increase in switching frequency, resulting in large magnetic component size and low power density; and third, existing matrix transformer structures make it difficult to achieve decoupling integration of multiple transformers, resulting in low core utilization.

[0003] Existing planar transformer magnetic integration schemes mainly employ EI (Electrical Integrator) or matrix transformers. Magnetic integration and optimization methods using EI transformers are relatively mature, but their power density is lower. Matrix transformers are typically composed of multiple cascaded element transformers. Distributing the main transformer into multiple element transformers reduces the cross-sectional area of ​​the magnetic core, and integrating the element transformers into a single magnetic core using the principle of flux cancellation eliminates the need for redundant magnetic cores. The most common matrix transformer structure is the UI (Unified Integrator-Unit) structure. By distributing a single transformer into two element transformers connected in series, the core cross-sectional area is only half that of a conventional transformer using an EI core. Therefore, matrix transformers have a smaller footprint, and this technology is commonly used in high-power-density DC / DC converters.

[0004] While existing planar magnetic integration schemes improve power density to some extent, they have limitations when integrating multiple transformers. This invention proposes a novel planar magnetic integration structure: a four-pillar array planar magnetic integration. This magnetic integration structure enables the integration of multiple high-power transformers, further reducing the size and weight of magnetic components, and providing a new technical approach for the development of high-power power conversion systems such as high-power-density space power stations and solid-state transformers. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a high-power-density four-pillar array decoupled magnetic integrated transformer based on an active clamp isolation Weinberg type. Its four-pillar magnetic integrated structure adopts a rectangular array layout without a central pillar, consisting of four edge pillars with equal cross-sections and upper and lower rectangular yokes forming a closed magnetic circuit frame. Through a special PCB winding method and magnetic flux cancellation mechanism, complete decoupling of the push-pull transformer and the flyback transformer is achieved. The specific technical solution is as follows:

[0006] A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg, comprising:

[0007] The four-pillar array planar magnetic integrated core adopts a rectangular array layout without a central magnetic pillar, and is composed of four edge magnetic pillars with equal cross-sections and upper and lower rectangular magnetic yokes forming a closed magnetic circuit frame.

[0008] Four edge magnetic pillars are arranged in a square array with equal spacing. The magnetic pillars and the magnetic yoke are integrally formed, and each magnetic pillar has a uniform air gap on its end face.

[0009] The magnetic integrated transformer integrates a push-pull transformer and a flyback transformer. The push-pull transformer has two sets of symmetrical primary and secondary windings, and the flyback transformer has primary and secondary windings. Each winding is wound on the four-column array planar magnetic integrated core via PCB winding.

[0010] By setting the number of turns in each winding and the air gap magnetic resistance of each magnetic column, the push-pull transformer and the flyback transformer can achieve magnetic circuit decoupling on the same magnetic core.

[0011] The present invention has the following beneficial effects:

[0012] (1) The four-column decoupled magnetic integrated matrix transformer proposed in this invention has for the first time realized the complete decoupling integration of push-pull transformer and flyback transformer on the same magnetic core in isolated Weinberg topology. It breaks through the decoupling bottleneck of multi-transformer integration in conventional matrix transformers, greatly improves the core utilization rate, and significantly reduces the volume and weight of magnetic components. It provides core technical support for improving the power density of high-power power systems such as space power stations and solid-state transformers.

[0013] (2) The proposed active clamp isolation Weinberg topology can effectively suppress voltage spikes in the switching transistors caused by leakage inductance, while achieving zero-voltage turn-on of all switching transistors, significantly reducing switching losses and switching stress, improving the circuit's conversion efficiency and long-term operational reliability, and laying the topological foundation for increasing switching frequency and miniaturizing magnetic components.

[0014] (3) The winding optimization method proposed for the non-sinusoidal current waveform of flyback transformer breaks through the application limitations of traditional winding interleaving technology, effectively reduces eddy current loss caused by high frequency harmonics, and at the same time, through the compromise design of non-complete interleaving structure, it takes into account efficiency, cost and manufacturability, and has stronger engineering adaptability.

[0015] (4) A holistic optimization design method combining core loss and winding loss is proposed. Through parametric modeling and loss scanning, the efficiency of the transformer under given power and volume is optimized.

[0016] (5) A magnetic integration design process suitable for high-power non-resonant converters is proposed, which takes into account the risk of magnetic saturation, the stability of inductor parameters and the uniformity of heat dissipation, and is suitable for high-power application scenarios.

[0017] The overall optimization design method and standardized design process proposed in this invention realize the coordinated optimization of magnetic core, winding and topology, and can quickly complete the design of high power density and high reliability magnetic integrated transformers. It is not only compatible with isolated Weinberg topology, but can also be extended to various multi-transformer power electronic conversion topologies, with a wide range of applications. Attached Figure Description

[0018] Figure 1 It is an active clamp-isolation Weinberg topology;

[0019] Figure 2 Four-column transformer magnetic circuit model;

[0020] Figure 3 Four-column transformer model;

[0021] Figure 4 Magnetomotive force analysis diagram of interleaved parallel and non-interleaved parallel PCB windings;

[0022] Figure 5 Fast Fourier Transform (FFT) analysis of flyback transformer winding current. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0024] Figure 1 shows the active clamp isolation Weinberg topology adapted to four-pillar magnetic integration, where the primary and secondary windings of the flyback transformer are respectively... The two sets of symmetrical primary and secondary windings of the push-pull transformer are respectively... Magnetic integration of flyback and push-pull transformers can also be achieved by changing the winding method of the PCB windings of a four-column transformer. The isolated Weinberg topology contains two transformers with a total of six windings. To push-pull the primary magnetizing inductance of the transformer, This is the primary magnetizing inductance of a flyback transformer (also known as a coupling inductor; for clarity of the topology, it will be referred to as a flyback transformer from now on). To calculate the sum of the leakage inductance of the primary and secondary windings of the push-pull winding, The leakage inductance of the primary and secondary windings of the flyback winding is calculated as the sum of the leakage inductance of the primary winding. For an ideal push-pull transformer ratio, This represents the turns ratio of an ideal flyback transformer.

[0025] In order to enable the integrated transformer to be physically coupled on the same magnetic core while keeping the magnetic circuits uncoupled, it is necessary to analyze the magnetic circuit model of the magnetically integrated structure. Figure 2 This is a magnetic circuit model of an integrated push-pull and flyback transformer structure. For ease of understanding, only the primary winding of the transformer is shown in the figure, and the analysis is based on the premise that the primary and secondary windings of the transformer satisfy ampere-turn balance. (Figure...) These are the first primary windings of the push-pull configuration. Push-pull second primary winding flyback primary winding The number of turns in the primary winding; (m=1,2,3, n=1,2,3) represents the magnetomotive force of each winding. The magnetic reluctance of the air gaps of each edge magnetic column; , , , These represent the magnetic flux of the 1st to 4th edge magnetic pillars, respectively.

[0026] The magnetic flux expressions for each magnetic column can be obtained as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] Since the four element transformers in the four-column matrix transformer are connected in series, the relationship between the transformer's port voltage and the magnetic flux of the columns is as follows:

[0032] ;

[0033] ;

[0034] ;

[0035] The terminal voltage relationship between the two transformers can be obtained as follows:

[0036] ;

[0037] The magnetizing inductance of the three transformers is:

[0038] ;

[0039] ;

[0040] ;

[0041] Figure 2 The multiple transformers integrated in the system are decoupled from each other. This is achieved by changing the number of winding turns N1, N2, and N3 and the air gap reluctance. This allows control of the magnetizing inductance of each transformer. The magnetic integration scheme proposed in this invention can simultaneously decouple and integrate up to three transformers without increasing the magnetic flux density of the magnetic plates. Since the isolated Weinberg circuit contains only two transformers, decoupling of flyback and push-pull circuits can be achieved. However, whether used for integrating additional filter inductors or for other parallel and interleaved magnetic integration of multi-transformer topologies, the multi-transformer integration scheme has high practical value.

[0042] The above analysis shows that applying the magnetic integration structure to the magnetic integration scheme of the isolated Weinberg topology can achieve decoupling in all working states. Figure 3 (a) is a three-dimensional model of a four-pillar transformer. The magnetic core is made of PC47 power ferrite material. The four edge magnetic pillars are arranged in a square array with equal spacing. The height of the magnetic pillars is 17mm. The upper and lower magnetic yokes are rectangular plates of equal thickness. The magnetic pillars and magnetic yokes are integrally formed. Each magnetic pillar has a uniform air gap of 0.35mm at its end face. Figure 3 (b) is a three-dimensional magnetoresistive model, whose equivalent magnetoresistive network consists of four edge magnetic pillars with air gap magnetoresistive properties, and the magnetic flux satisfies:

[0043] ;

[0044] The windings of a power electronic transformer mainly consist of a copper sheet (PCB), Litz wire, and round conductors. The magnetomotive force distribution of the PCB windings is related to the winding arrangement. Winding arrangements are divided into interleaved and non-interleaved arrangements, as shown below. Figure 4 As shown in (a) and (b). Figure 4 (a) is an interleaved parallel winding structure with a layer sequence of PSPSPSPS, where the primary winding and secondary winding are arranged alternately. Figure 4 (b) is a non-interleaved parallel winding structure with a layer sequence of PPPPSSSS, where all primary windings are concentrated in the upper half and all secondary windings are concentrated in the lower half.

[0045] Depend on Figure 4 As can be seen from the magnetomotive force distribution curve, the peak value of the magnetomotive force of the staggered winding arrangement is only 1 / 4 of that of the non-staggered arrangement, and the magnetomotive force distribution is more uniform. Therefore, the AC resistance of the winding is smaller and the eddy current loss is lower.

[0046] In power planar transformers, PCB windings are often connected in multiple parallel layers to reduce losses. Figure 4 The diagram illustrates different arrangements of the primary and secondary windings connected in parallel. As can be seen, the interleaved winding arrangement provides a more uniform magnetomotive force distribution and a lower magnetomotive force ratio compared to the non-interleaved structure. Therefore, the AC resistance of the interleaved winding structure is also lower. Once the transformer winding arrangement and the AC resistance parameters of the PCB windings are determined, the transformer winding losses can be quickly calculated.

[0047] The magnetomotive force distribution of PCB windings is related to the winding arrangement. Winding arrangements are divided into interleaved and non-interleaved arrangements, such as... Figure 4 As shown. In power planar transformers, to reduce losses, the PCB windings are often connected in multiple parallel layers. Figure 4 The diagram illustrates different arrangements of the primary and secondary windings connected in parallel. It is evident that the interleaved winding arrangement results in a more uniform magnetomotive force distribution and a lower magnetomotive force ratio compared to the non-interleaved structure. Consequently, the AC resistance of the interleaved winding structure is also lower.

[0048] However, current analyses of reducing AC resistance through winding interleaving techniques are based on the condition that the primary and secondary windings of the transformer operate simultaneously. Due to the operating characteristics of flyback circuits, the primary and secondary windings of a flyback transformer do not operate simultaneously. In an isolated Weinberg topology, the operating frequency of the flyback transformer is twice that of an active switch. Therefore, reducing winding losses at high frequencies is crucial. Since the winding current determines the magnetic field distribution near the winding, it is necessary to analyze the current components of the transformer at various frequencies. Fast Fourier Transform (FFT) can be used to analyze the typical winding current waveforms of the primary and secondary windings of a flyback transformer operating in continuous current mode, identifying their current components at various frequencies.

[0049] The FFT analysis results are as follows: Figure 5 As shown. Figure 5 (a) is the FFT spectrum of the primary current of the flyback transformer. Figure 5 (b) shows the primary and secondary current waveforms of a common flyback transformer. From... Figure 5 As shown in (b) and (d), the primary and secondary winding currents of a flyback transformer contain both DC and AC components, and the harmonic components at each frequency are out of phase. The magnetomotive force generated by the AC components at each frequency can be canceled out by the primary winding interleaving technique, avoiding the accumulation of magnetomotive force at the upper and lower edges of the winding. Therefore, the winding interleaving technique can also effectively reduce the eddy current losses of the flyback transformer windings. The DC component of the current, however, does not cause AC losses. Figure 5(c) is the FFT spectrum of the secondary current of the flyback transformer. The analysis results show that the primary and secondary winding currents of the flyback transformer both contain DC components and abundant AC harmonic components. The fundamental component accounts for about 63.7% of the amplitude, the second harmonic component accounts for about 21.2%, and the proportion of the third and higher harmonics gradually decreases. Moreover, the phases of the primary and secondary harmonic currents at the same frequency are completely opposite.

[0050] Compared to the non-interleaved PPP-SSSS structure, the interleaved PSSP-PSSP and SSPP-SSPP structures reduce winding losses by 41.7% and 37.1%, respectively. The fully interleaved structure only reduces losses by 7.4% compared to the partially interleaved structure, showing little efficiency improvement. Since the processing cost and design difficulty of an 8-layer PCB are far higher than those of a double-layer board, and heat dissipation is also more challenging, this invention, as a trade-off between cost and efficiency, uses a partially interleaved structure composed of multiple double-layer boards, which is easier to design and process, instead of the fully interleaved 8-layer board solution.

[0051] The novel four-column structure retains the low-height advantage of array structures while decoupling and integrating multiple power transformers, thus improving the power density and core utilization of the transformers. Therefore, the four-column transformer has significant advantages in power density and efficiency compared to existing planar magnetic integration solutions.

Claims

1. A high-power-density four-column array decoupled magnetic integrated transformer based on active clamp isolation Weinberg, characterized in that, include: The four-pillar array planar magnetic integrated core adopts a rectangular array layout without a central magnetic pillar, and is composed of four edge magnetic pillars with equal cross-sections and upper and lower rectangular magnetic yokes forming a closed magnetic circuit frame. Four edge magnetic pillars are arranged in a square array with equal spacing. The magnetic pillars and the magnetic yoke are integrally formed, and each magnetic pillar has a uniform air gap on its end face. The magnetic integrated transformer integrates a push-pull transformer and a flyback transformer. The push-pull transformer has two sets of symmetrical primary and secondary windings, and the flyback transformer has primary and secondary windings. Each winding is wound on the four-column array planar magnetic integrated core via PCB winding. By setting the number of turns in each winding and the air gap magnetic resistance of each magnetic column, the push-pull transformer and the flyback transformer can achieve magnetic circuit decoupling on the same magnetic core.

2. The high power density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, In the active clamp isolation Weinberg topology, the primary and secondary windings of the flyback transformer are P3 and S3, respectively, and the two sets of symmetrical primary and secondary windings of the push-pull transformer are P1 and S1 and P2 and S2, respectively.

3. The high power density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, In the magnetic circuit model of the four-pillar array planar magnetic integrated core, the magnetic flux of each edge pillar is: , , , And the magnetic flux satisfies .

4. The high power density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, The magnetic integrated transformer can decouple and integrate up to three transformers simultaneously. The excitation inductance of each transformer is controlled by changing the number of turns N1 of the push-pull first primary winding, the number of turns N2 of the push-pull second primary winding, the number of turns N3 of the flyback primary winding, and the air gap reluctance.

5. A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, The magnetic core is made of PC47 power ferrite material.

6. A high-power-density four-column array decoupled magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 5, characterized in that, The magnetic column is 17mm high, and the upper and lower magnetic yokes are rectangular flat plates of equal thickness.

7. A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 6, characterized in that, Each magnetic post has a uniform air gap of 0.35mm on its end face.

8. A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, The PCB windings are composed of multiple double-layer boards forming a non-completely interleaved structure.

9. A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg, as described in claim 8, is characterized in that... The layer sequence of the incompletely interleaved structure is that the primary winding is concentrated in the upper half and the secondary winding is concentrated in the lower half, or a PSSP-PSSP or SSPP-SSPP structure is adopted.

10. A high-power-density four-column array decoupling magnetic integrated transformer based on active clamp isolation Weinberg as described in claim 1, characterized in that, The magnetic flux expressions for each magnetic column are as follows: ； ； ； ； in, The magnetic reluctance of the air gaps between each edge magnetic column is given. , , For the magnetomotive force of each winding; The relationship between the transformer's port voltage and the magnetic flux of the magnetic core is as follows: ； ； ； The terminal voltage relationship of the transformer is as follows: ； The magnetizing inductance of the three transformers is: ； ； ； in, , , These are the first primary windings of the push-pull configuration. Push-pull second primary winding flyback primary winding The number of turns in the primary winding.

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