Low-loss winding planar transformer for multi-output flyback converter

Abstract

The invention relates to a low-loss winding planar transformer for a multi-output flyback converter. The transformer includes: a magnetic core having a central region; a primary winding extending around the central region; a first secondary winding comprising a first conductor having one or more first turns extending around the central region, where the first conductor has a first width and is arranged to receive electromagnetic flux from the primary winding; and a second secondary winding comprising a second conductor having one or more second turns extending around the central region, where the second conductor has a second width and is arranged to receive electromagnetic flux from the primary winding. In one aspect, the number of the one or more second turns is greater than the number of the one or more first turns and the first width is greater than the second width.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application serial number 18 / 438,140, ​​filed on February 9, 2024, entitled “LOW LOSS WINDING PLANAR TRANSFORMERS FOR MULTI-OUTPUT FLYBACK CONVERTERS”, and claims priority to Chinese provisional patent application number 202311483644.6, filed on November 7, 2023, entitled “LOW LOSS WINDING PLANAR TRANSFORMERS FOR MULTI-OUTPUT FLYBACK CONVERTERS”, which applications are hereby incorporated by reference in their entirety for all purposes. Technical Field

[0003] The described embodiments relate generally to power converters, and more particularly, the present embodiments relate to a low loss winding planar transformer for a multiple output flyback power converter. Background Art

[0004] Electronic devices such as computers, servers, and televisions employ one or more power conversion circuits to convert one form of electrical energy to another form of electrical energy. Some power conversion circuits convert a high (or low) DC voltage to a lower (or higher) DC voltage using a circuit topology called a DC-DC converter. Since many electronic devices are sensitive to the size and efficiency of power converter circuits, new power converters can provide relatively high efficiency and small size for new electronic devices. Summary of the invention

[0005] In some embodiments, a transformer is disclosed. The transformer includes: a magnetic core having a central region; a primary winding extending around the central region; a first secondary winding including a first conductor having one or more first turns extending around the central region, wherein the first conductor has a first width and is arranged to receive electromagnetic flux from the primary winding; and a second secondary winding including a second conductor having one or more second turns extending around the central region, wherein the second conductor has a second width and is arranged to receive electromagnetic flux from the primary winding, wherein the number of the one or more second turns is greater than the number of the one or more first turns and the first width is greater than the second width.

[0006] In some embodiments, the magnetic core defines a winding region that is concentric with the central region and has a predefined width to receive the first secondary winding and the second secondary winding.

[0007] In some embodiments, the predefined width is greater than the second width of the second conductor.

[0008] In some embodiments, the second width is greater than 50% of the predefined width.

[0009] In some embodiments, the second width is greater than 75% of the predefined width.

[0010] In some embodiments, the second width is greater than 90% of the predefined width.

[0011] In some embodiments, the first secondary winding is located on a first layer and the second secondary winding is located on a second layer.

[0012] In some embodiments, the first secondary winding and at least a portion of the second secondary winding are located on the same layer.

[0013] In some embodiments, an inductor is disclosed. The inductor includes: a magnetic core having a central region; and a conductor having a first winding extending around the central region and a second winding extending around the central region, wherein a first width of the conductor in the first winding is greater than a second width of the conductor in the second winding.

[0014] In some embodiments of the inductor, the magnetic core has a predefined width to receive the first winding and the second winding.

[0015] In some embodiments of the inductor, the first winding is an outer winding and the second winding is an inner winding.

[0016] In some embodiments of the inductor, the conductor further includes a third winding extending around the central region and having the first width.

[0017] In some embodiments of the inductor, the second winding is located between the first winding and the third winding.

[0018] In some embodiments of the inductor, the magnetic core defines a winding region that is concentric with the central region and has a predefined width to receive the first winding and the second winding.

[0019] In some embodiments of the inductor, the first width is at least 75% of the predefined width.

[0020] In some embodiments of the inductor, the first width is at least 90% of the predefined width.

[0021] In some embodiments, a method of forming a transformer is disclosed. The method includes: providing a magnetic core having a central region; forming a primary winding extending around the central region; forming a first secondary winding, the first secondary winding including a first conductor having one or more first turns extending around the central region, wherein the first conductor has a first width and is arranged to receive electromagnetic flux from the primary winding; and forming a second secondary winding, the second secondary winding including a second conductor having one or more second turns extending around the central region, wherein the second conductor has a second width and is arranged to receive electromagnetic flux from the primary winding, wherein the number of the one or more second turns is greater than the number of the one or more first turns and the first width is greater than the second width. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A dual output quasi-resonant (QR) flyback converter using a low-loss winding planar transformer according to some embodiments of the present disclosure is shown;

[0023] Figure 2A shows a cross-sectional view of a low winding loss planar transformer with multiple outputs and with a full layer on top according to some embodiments of the present disclosure;

[0024] Figure 2B shows a cross-sectional view of a low winding loss planar transformer with multiple outputs and with a full layer at the bottom according to certain embodiments of the present disclosure;

[0025] Figure 2C shows a low winding loss planar transformer with a top full layer according to some embodiments;

[0026] Figure 2D shows a low winding loss planar transformer with a bottom full layer according to some embodiments;

[0027] Figure 2E shows a low winding loss planar transformer with top and bottom complete layers according to some embodiments;

[0028] Figure 2F shows a planar transformer structure that may also include a structure having a low permeability material according to some embodiments;

[0029] Figure 2G A planar transformer structure according to some embodiments is shown, which may include a structure having distributed gaps in a magnetic core;

[0030] Figure 2H shows a planar transformer structure according to some embodiments;

[0031] Figure 3 shows a graph illustrating a quadrature decomposition of current flowing in a transformer used in a flyback power converter operating in a discontinuous conduction mode according to some embodiments;

[0032] Figure 4 Shown as Figure 2A A graph showing the relationship between the total winding loss as a function of load variation of the disclosed planar transformer;

[0033] Figure 5 Shown as Figure 2A a graph showing the relationship between total winding losses as a function of operating frequency of the disclosed planar transformer;

[0034] Figure 6 shows the eddy currents induced in a conductor by an alternating magnetic field;

[0035] Figure 7 The use of the finite element method (FEM) according to some embodiments is shown. Figure 2A Magnetic field distribution of planar transformer;

[0036] Figure 8 A schematic diagram showing an equivalent magnetic circuit of a distributed air-gap magnetic core structure according to some embodiments;

[0037] Fig. 9 Shows Figure 8 The variation curve of MMF in the core along the dotted lines A1, B1, B2, A2;

[0038] Fig.10 According to some embodiments, Figure 2A Changes in the magnetic field distribution of the planar transformer;

[0039] Fig.11 shows the time domain distribution of winding losses of various planar transformer structures using FEM according to some embodiments;

[0040] Fig.12 A modified sample of the prototype with a 78W dual output QR flyback converter for TV power supply is shown;

[0041] FIG. 13A to FIG. 13D Graphs showing efficiency as a function of load for various embodiments of the disclosed planar transformer with low winding losses at various input voltage levels;

[0042] FIG. 14A to FIG. 14Dshows a cross-sectional view of an inductor having windings of varying widths according to some embodiments; and

[0043] Fig.15 shows the value of FIG. 14A to FIG. 14D A graph of the winding losses of a winding structure. DETAILED DESCRIPTION

[0044] The circuits, structures, and related techniques disclosed herein relate generally to power converters. More specifically, the circuits, devices, and related techniques disclosed herein relate to transformers used in flyback converters. Embodiments of the present disclosure relate to structures and methods for optimizing winding losses in planar transformers used in multi-output flyback converters. The structures, devices, and related techniques disclosed herein can achieve a reduction in winding losses by forming a top and / or bottom of a secondary winding of a planar transformer that extends across the entire width of the winding area of ​​the planar transformer to block stray magnetic flux, thereby improving the efficiency of the power converter. The structures and techniques disclosed herein make it possible to suppress stray magnetic flux in the core window of a multi-output flyback planar transformer, thereby achieving a reduction in relatively high frequency (AC) winding losses.

[0045] In some embodiments, the multi-output flyback power converter can be a dual-output flyback power converter. The dual-output power converter may have a transformer, which may include a primary winding and a secondary winding, wherein the secondary winding may include a first secondary winding and a second secondary winding. In various embodiments, the second secondary winding may have more turns than the first secondary winding, and the first secondary winding may have a greater width than the second secondary winding. In some embodiments, the first secondary winding may have a greater width than 1 / 2 the width of the transformer area so that it blocks stray magnetic flux. This may be counterintuitive because a winding with fewer turns may be narrower than a winding with multiple turns to reduce the DCR of a winding with many turns, but the structures and techniques disclosed herein can significantly reduce AC losses, thereby reducing total losses.

[0046] In some embodiments, the inductor may have windings with varying widths, with the outer winding extending across a majority of the inductor area to block stray magnetic flux. In various embodiments, a multi-output power converter may use switches based on gallium nitride (GaN) and / or silicon carbide (SiC) so that the power converter can operate at a relatively high operating frequency compared to power converters using silicon-based switches. Various inventive embodiments are described herein, including methods, processes, systems, apparatus, etc.

[0047] Several exemplary embodiments will now be described with respect to the accompanying drawings forming part thereof. The subsequent description only provides embodiments and is not intended to limit the scope, applicability or configuration of the present disclosure. On the contrary, the subsequent description of the embodiments will provide an enabling description for implementing one or more embodiments for those skilled in the art. It should be understood that various changes can be made in the functions and arrangements of the elements without departing from the spirit and scope of the present disclosure. In the following description, for the purpose of illustration, specific details are set forth in order to provide a thorough understanding of certain inventive embodiments. However, it is apparent that various embodiments can be practiced without these specific details. The drawings and descriptions are not intended to be restrictive. The words "example" or "exemplary" are used herein to mean "used as an example, instance or illustration". Any embodiment or design described herein as "exemplary" or "example" is not necessarily to be interpreted as being preferred or advantageous over other embodiments or designs.

[0048] In the current method, a multi-output flyback converter (MOFC) may use closed-loop feedback control only for the main output, while the auxiliary output may lack feedback regulation. Due to component non-idealities, such as the voltage drop on the secondary diode and the changes in the transformer winding resistance and leakage inductance, the MOFC may exhibit cross-regulation operation. In the current method, the power converter circuit may use a planar transformer with a compact structure, which may result in a reduced spacing between the windings and between the windings and the magnetic core. The reduced spacing may degrade the skin effect and the proximity effect, resulting in increased winding losses. In the current method, the planar transformer used in the flyback converter may use a ferrite material as the core. The intensity of the diffuse magnetic flux may increase as the distance from the gap decreases. In addition, there may be a significant magnetic potential difference between the upper yoke and the lower yoke of the core, resulting in the generation of stray magnetic flux in the core window. These leakage magnetic fluxes may pass through the windings, resulting in increased winding losses.

[0049] Embodiments of the present disclosure can suppress stray magnetic flux in MOFC planar transformers. In some embodiments, air gaps can be formed in the core, which can concentrate the magnetic potential at the ends of the gap, thereby generating diffuse magnetic flux within the core window. The technology disclosed herein provides methods for analyzing losses associated with windings in MOFC planar transformers, together with methods for planar transformer winding formation and optimization.

[0050] Figure 1A dual output quasi-resonant (QR) flyback converter using a low-loss winding planar transformer according to some embodiments of the present disclosure is shown. In the illustrated embodiment, the QR flyback converter 100 may include a first output terminal 110, a second output terminal 114, and a third output terminal 116. The QR flyback converter 100 may generate a first output voltage Vo1 and a first output current Io1 between the first output terminal 110 and the second output terminal 114. In addition, the QR flyback converter 100 may generate a second output voltage Vo2 and a second output current Io2 between the first output terminal 110 and the third output terminal 116, respectively. In some embodiments, for example, Vo1=12V and Vo2=120V, while Io1=2.5A and Io2=0.4A. Other suitable voltages for the first output voltage and the second output voltage may be used, and other suitable first load currents and second load currents may be used. The QR flyback converter 100 may be coupled to an input power supply 120. The input power supply 120 may have a value of, for example, 90V to 264V, however other suitable voltage values ​​may be used. The QR flyback converter 100 may include a transformer 102. The transformer 102 may have a primary winding 108, a first secondary winding 104, and a second secondary winding 106. The primary winding 108 may have a number of turns (e.g., Np=14), the first secondary winding may have a number of turns (e.g., Ns1=1), and the second secondary winding may have a number of turns (e.g., Ns2=9). The first output voltage Vo1 and the second output voltage Vo2 may be connected through a shared winding, which may result in an actual turns ratio of 14:1:10.

[0051] In the embodiment shown, a 6-layer printed circuit board (PCB) can be used to form the winding, and the secondary winding can be arranged on the top and bottom layers. Other numbers of PCB layers can be used. In the current method, the winding DC loss can be minimized, so the cross-sectional area (S) of the secondary winding can satisfy equation (1):

[0052]

[0053] Figure 2A 1 shows a cross-sectional view of a low winding loss planar transformer with multiple outputs that can be used in a QR flyback converter 100 according to some embodiments of the present disclosure. Figure 2AAs shown, the planar transformer 200 may include a magnetic core 214, an air gap 238, a primary winding 202, a first secondary winding 204a and a second secondary winding 204b, and an auxiliary winding 212. The planar transformer 200 may also include an air gap avoidance portion 206, a first safety distance 208, and a second safety distance 210. The air gap avoidance portion 206 may be a gap distance between the second secondary winding 204b and the core 214 at a proximal position. The second safety distance 210 may be a distance between the second secondary winding 204b and the core 214 at a distal position. The first safety distance 208 may be a distance between the first secondary winding 204a and the core 214. In the illustrated embodiment, the planar transformer 200 may include a 6-layer printed circuit board (PCB) winding, wherein the secondary winding is arranged on a top layer and a bottom layer. The core of the transformer may also be referred to as a magnetic core.

[0054] The primary winding 202 may include, for example, 14 turns, however, other suitable numbers of primary windings may also be used. The first secondary winding 204a (WS1) may include, for example, 1 turn that may be shared between the first output voltage Vo1 and the second output voltage Vo2, and the second secondary winding 204b may include, for example, 9 turns (WS2 to WS3). 10 ). Other suitable numbers of turns may be used for the first secondary winding and the second secondary winding. In various embodiments, the second secondary winding may have more turns than the first secondary winding, and the first secondary winding may have a greater width than the second secondary winding. The winding ws2 may be disposed away from the core 214 by the air gap avoidance portion 206, and the winding ws 10 The core 214 may be disposed away from the core 214 by a second safety distance 210. In the illustrated embodiment, the winding may be disposed relatively close to the core to utilize the core window volume while ensuring compliance with national safety regulations. Sufficient clearance may be provided on the side close to the air gap. In the illustrated embodiment, the transformer 102 may include a first secondary winding 104a (ws1) disposed in the uppermost layer of the winding, while the second secondary windings 104b (ws2 to ws10) may be evenly distributed in the lowermost layer.

[0055] Figure 2B A cross-sectional view of a low winding loss planar transformer with multiple outputs that may be used in a QR flyback converter 100 according to certain embodiments of the present disclosure is shown. Figure 2B A planar transformer 250 is shown that is similar to the planar transformer 200 , except that Ws1 with a complete layer is disposed at the bottom of the transformer and ws2 - ws10 are disposed at the top of the transformer.

[0056] Figure 2CA low winding loss planar transformer with a top complete layer according to some embodiments is shown. The planar transformer shown may include a first core 242 and a second core 244, respectively. The planar transformer shown may also include winding sections 246a and 246b, where the top layer of the winding is a complete conductor. The planar transformer shown may have a window with an air gap 248. Although the illustrated embodiment shows a single air gap core structure, the winding structures and techniques disclosed herein can be used for all magnetic core transformer structures.

[0057] Figure 2D A low winding loss planar transformer with a bottom full layer is shown according to some embodiments. Figure 2D The planar transformer shown is similar to Figure 2C A planar transformer is shown, except that the bottom layer in the windings is a complete layer.

[0058] Figure 2E A low winding loss planar transformer with top and bottom complete layers is shown according to some embodiments. Figure 2E The planar transformer shown is similar to Figure 2C The planar transformer shown in FIG. 1 is different in that the top and bottom layers in the winding are complete layers. The planar transformer structures disclosed herein may include structures having a single gap in the magnetic core. The planar transformer structures disclosed herein may also include structures having low permeability materials, such as Figure 2F In addition, the planar transformer structure disclosed herein may include a structure having distributed gaps in the magnetic core, such as Figure 2G to Figure 2H shown.

[0059] The techniques disclosed herein enable the design and formation of a planar transformer 200 with reduced winding losses. When a conductor is subjected to an alternating magnetic field, the magnetic field may induce eddy currents in the conductor, which may result in the generation of a magnetic field opposite to the external magnetic field, thereby hindering the flow of eddy currents in the conductor. The generated magnetic field may be determined by the conductivity of the conductor and the frequency of the alternating magnetic field. Therefore, placing copper on the surface of the winding may hinder the magnetic flux through the winding. The techniques disclosed herein may be used to form low winding loss transformers of any core shape (such as, but not limited to, EIR, EI, U, or C-shaped cores) and any number of winding layers in a planar transformer.

[0060] Figure 3A graph showing the orthogonal decomposition of the current flowing in a transformer used in a flyback power converter operating in discontinuous conduction mode (DCM) according to some embodiments is shown. The current flowing through the primary winding and the secondary winding of a single-output flyback converter operating in DCM can be mathematically divided into two orthogonal current components. Specifically, the orthogonal ip_L(t) and ip_TX(t) and is_L(t) and is_TX(t). ip_L(t) and is_L(t) are called inductor components because their phase relationship is the same as the inductor current. Similarly, ip_TX(t) and is_TX(t) may have the same phase relationship as the transformer current, so they are called transformer components. The sum of the winding losses generated by these two components is equal to the total winding losses. By applying a frequency domain analysis method for high-frequency winding losses, the periodic current i(t) can be decomposed using Fourier decomposition as follows:

[0061]

[0062] Idc refers to the DC component of i(t), while Iac_n represents the amplitude of the nth harmonic component of i(t). Under the excitation of i(t), the total winding loss is the sum of the losses caused by each individual harmonic component of i(t). This relationship can be expressed as:

[0063]

[0064] Variable P WindingLoss_Total , P WindingLoss_DC and P WindingLoss_AC (n) represent the total winding loss, the winding loss caused by the DC component of i(t), and the winding loss caused by the nth harmonic component of i(t), respectively. When analyzing the winding loss of a single-output flyback converter by frequency domain analysis, it should be noted that ip_L(t), is_L(t) and ip_TX(t), is_TX(t) can be orthogonal. Therefore, the harmonic components derived from their Fourier decomposition are also orthogonal. The total winding loss is the sum of the individual winding losses caused by each harmonic component and can be expressed as follows:

[0065] P WindingLossTotal =PL WindinfLossTotal +P Tx_windmgLoss_Total

[0066] P L_WindingLoss_Total and P Tx_WindingLoss_Total Represents the winding loss under the excitation of ip_L(t), is_L(t) and ip_TX(t), is_TX(t).

[0067] Figure 4A graph showing the relationship between total winding losses as a function of load variation is shown. Specifically, Figure 4 The relationship between the total winding losses of a planar transformer as a function of its load variation for an exemplary 78W single output flyback converter operating in discontinuous conduction mode (DCM) is shown. Figure 4 As can be seen from the figure, as the load increases, P L_WindingLoss_Total Dominate.

[0068] Figure 5 A graph showing the relationship between total winding losses as a function of operating frequency is shown. Figure 5 The graph in Figure 1 is an example 78W single output flyback converter planar transformer. Figure 5 It can be seen that as the frequency increases, P L_WindingLoss_Total Dominate.

[0069] In the case of a quasi-resonant (QR) flyback converter operating in DCM mode, the main contributor to the total winding losses is the eddy current losses generated by the inductor current. Therefore, optimizing the transformer winding design for a single-output QR flyback converter may focus on mitigating the winding eddy current losses.

[0070] For MOFC, while the current flowing through the transformer primary winding may be similar to that of a single output configuration, the current flowing through each secondary branch is different due to changes in the turns ratio and output branch impedance. However, when converting the secondary current of the MOFC to the primary side, the sum of these currents is equal to that of a single output flyback converter. In some embodiments, the design and formation of the transformer windings in a multi-output QR flyback converter can be addressed by mitigating winding eddy current losses caused by the inductive current component.

[0071] Figure 6 The eddy currents induced in the conductor by the alternating magnetic field are shown. These eddy currents can cause a magnetic field to be generated that is opposite to the external magnetic field, thereby hindering the eddy currents from flowing through the conductor. The magnitude of the magnetic field generated by the eddy currents can be determined by the conductivity of the conductor and the frequency of the alternating magnetic field. In some embodiments, placing a conductor (such as but not limited to copper) on the surface of the winding can hinder the magnetic flux through the winding.

[0072] Figure 7 FIG. 2 shows the magnetic field distribution of a planar transformer 200 using a finite element method (FEM) according to some embodiments. Figure 7 As shown, the stray magnetic flux across the winding can be significantly reduced.

[0073] Figure 8Schematic diagram showing an equivalent magnetic circuit of a distributed air gap core structure according to some embodiments. In the embodiment shown, the air gaps in the center column and the side column can be made to have the same size. Figure 8 As can be seen in FIG. 1 , the concentrated magnetomotive force (MMF) in the air gap of the center column can be evenly distributed to the air gaps in the center column and the side columns. In various embodiments, Figure 8 The schematic diagram shown may represent a planar transformer 200 .

[0074] Fig. 9 Shows Figure 8 The MMF in the core changes along the direction of the dotted lines A1, B1, B2, A2. In the illustrated embodiment, the distributed air gap can significantly reduce the magnetic potential difference between the upper and lower back plates compared to the conventional core structure using only a central core column with an air gap. The stray magnetic flux in the core window (Φa_2~Φa_n) represents the magnetic potential difference between the upper and lower back plates divided by the magnetic resistance (Ra_2~Ra_n) in the core window. Fig. 9 It can be seen from FIG. 2 that the stray magnetic flux of the planar transformer 200 can be significantly reduced.

[0075] Fig.10 FIG. 2 shows a change in magnetic field distribution of a planar transformer 200 according to some embodiments. Fig.10 As shown, the stray magnetic flux in the core window can be reduced by adopting a distributed air gap structure. It can also be seen that the improved winding structure of the planar transformer 200 is effective when using a distributed air gap structure.

[0076] Fig.11 The time domain distribution of winding losses of various planar transformer structures using FEM according to some embodiments is shown. Graph 1102 shows the time domain distribution of winding losses of the current method, graph 1104 shows the time domain distribution of winding losses of the disclosed planar transformer 200, and graph 1106 shows the time domain distribution of winding losses of the disclosed planar transformer 250. Table 1 lists the average values ​​of winding losses for various structural combinations. Fig.11 As shown in Table 1, using the current method for core structure, the disclosed embodiment of the winding structure can reduce the winding loss by 0.827 W ​​compared to the current solution. This is a significant reduction in winding loss. Further, using the distributed air gap core structure, the average winding loss of the disclosed embodiment of the winding structure can be 1.07 W, which is 0.18 W lower than 1.25 W of the current method.

[0077] Table I. Average values ​​of winding losses

[0078]

[0079] Compared to using the current method, when using the example of the embodiment according to the distributed air gap core structure, the average winding loss of the unmodified winding structure is reduced by 1.165W. This reduction can be attributed to the distributed air gap structure being able to reduce the stray magnetic flux and diffuse magnetic flux in the core. In addition, when using the distributed air gap structure, the example of the winding structure according to the embodiment reduces the winding loss by 0.518W, and this reduction can be achieved by using the technology disclosed herein to enable the fringe field of the air gap to be suppressed. By subtracting 0.518W from 1.165W, it is found that the example with the distributed air gap core structure according to the embodiment can suppress the stray magnetic flux by 0.647W. Therefore, the example with the improved winding structure and the distributed air gap core structure according to the embodiment can significantly reduce the stray magnetic flux.

[0080] Example :

[0081] Various examples of the present disclosure are provided below.As used hereinafter, any reference to a series of examples should be understood as a separate reference to each of these examples.

[0082] Fig.12 A modified sample of a prototype with a 78W dual output QR flyback converter for a TV power supply is shown. The modified sample using the winding structure of the embodiment of the present disclosure produced a 1.2% increase in the overall efficiency of the power converter and a significant reduction in the temperature of the planar transformer compared to the winding structure used by the current method. Due to the requirements of high stability and low cost for the TV power supply, Schottky diodes and high-efficiency diodes are used as output diodes for 12V and 120V, respectively. Aluminum electrolytic capacitors are selected as output filter capacitors. The prototype utilizes NV9580 as the main control switch of the QR flyback converter. NV9580 integrates an analog controller and a GaN switch into a compact QFN5x6 semiconductor package, thereby enabling NV9580 to simplify the complexity of the control loop and allow the QR flyback converter to operate efficiently at frequencies in the range of hundreds of kHz.

[0083] FIG. 13A to FIG. 13D Graphs showing the efficiency as a function of load for various embodiments of the disclosed planar transformer with low winding losses at various input voltage levels. Graph 1302 shows the results for the disclosed planar transformer with improved winding structure (with distributed air gap structure), graph 1304 shows the results for the current approach with distributed air gap structure, graph 1306 shows the results for the disclosed planar transformer with improved winding structure (without distributed air gap structure), and graph 1308 shows the results for the current approach without distributed air gap structure. Fig.13A The results for an input voltage of 90Vac are shown, Fig. 13B The results for an input voltage of 115Vac are shown. Fig. 13C The results are shown for an input voltage of 230Vac, and Fig.13D Results are shown for an input voltage of 264Vac. The results show that when used with current methods for core structure, embodiments of the disclosed winding structure produce a 1.2% increase in the overall efficiency of the power converter compared to the current method. When a planar transformer uses a distributed air gap core structure according to an embodiment of the present disclosure, it can increase the overall power converter efficiency by 0.3%.

[0084] also, FIG. 13A to FIG. 13D The example thermal steady-state distribution of shows that the planar transformer according to the embodiments of the present disclosure can significantly reduce the thermal steady-state temperature of the power converter. For example, a temperature reduction of 30-50°C can be achieved compared to the current method. In various embodiments, a temperature reduction of 27°C can be achieved compared to the current method.

[0085] FIG. 14A to FIG. 14D A cross-sectional view of an inductor with windings of varying widths according to some embodiments is shown. In the embodiment shown, the inductor may have windings with varying widths, where the outer winding extends across a large portion of the inductor area to block stray magnetic flux. In the embodiment shown, the planar transformer may include a 6-layer PCB wound "EE" type planar inductor. The planar inductor shown may have similar parameters, except for its winding structure. Fig.14D A magnetic core 1402 is shown that can have a central region 1404, and a conductor 1408 having a first winding 1410 extending around the central region 1404 and a second winding 1412 extending around the central region 1404. A first width of the conductor 1408 in the first winding can be greater than a second width of the conductor in the second winding. The magnetic core can also include an air gap 1406.

[0086] Fig.15 shows the value of FIG. 14A to FIG. 14D Graph 1502 shows the winding loss of the winding structure. Fig.14A The winding losses of the structure as a function of frequency. Graph 1504 shows Fig. 14B The winding losses of the structure as a function of frequency. Graph 1506 shows Fig. 14C The winding losses of the structure as a function of frequency. Graph 1508 shows Fig.14D Winding losses as a function of frequency for the structure in FIG. FIG. 14A to FIG. 14D The stray flux suppression effect of the inductor structure leads to a reduction in winding losses. Fig.14DIn the case of the inductor structure of FIG. 1 , the winding loss is reduced by more than 30% compared to the current method. In addition, as the operating frequency increases, the reduction in winding loss also increases.

[0087] Although the disclosed structures and techniques are described and illustrated herein with respect to some specific configurations of multi-output power converters, embodiments of the present disclosure are suitable for use with other configurations of power converters. For example, multi-output converters are not limited to only two outputs, but also include three, four or more outputs. Multi-output converters are not limited to only flyback converters, but also include ACF, AHB and LLC converters, etc.

[0088] In the foregoing description, embodiments of the present disclosure have been described with reference to many specific details, which may vary with specific implementation. Therefore, the description and drawings should be considered illustrative rather than restrictive. The only and exclusive indication of the scope of the present disclosure, and what the applicant wishes to be the scope of the present disclosure, is the literal and equivalent scope of the claims published in this application, which adopt the specific form published by these claims, including any subsequent revisions. The specific details of a particular embodiment may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure.

[0089] In addition, spatially relative terms (such as "bottom" or "top", etc.) can be used to describe the relationship of one element and / or feature to another element and / or feature, for example, as shown in the figures. It should be understood that spatially relative terms are intended to cover different orientations of the device in use and / or operation other than the orientation depicted in the figures. For example, if the device in the figure is turned over, the element described as the "bottom" surface can then be oriented "above" other elements or features. The device can be oriented in other ways (e.g., rotated 90° or in other orientations) and can be interpreted accordingly by the spatially relative descriptors used herein.

[0090] As used herein, the terms "and", "or", and "and / or" may include multiple meanings, which are also expected to depend at least in part on the context in which the terms are used. Generally, "or", if used in an associative list (such as A, B, or C), is intended to mean A, B, and C (used in an inclusive sense here) as well as A, B, or C (used in an exclusive sense here). In addition, as used herein, the term "one or more" may be used to describe any feature, structure, or characteristic in the singular or may be used to describe a certain combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and the claimed subject matter is not limited to this example. In addition, the term "at least one", if used in an associative list (such as A, B, or C), may be interpreted to mean any combination of A, B, and / or C, such as A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc.

[0091] References throughout this specification to "one example," "example," "some examples," or "exemplary implementations" mean that a particular feature, structure, or characteristic described in conjunction with a feature and / or example may be included in at least one feature and / or example of the claimed subject matter. Thus, the phrases "in one example," "example," "some examples," "in some implementations," or other similar phrases appearing throughout this specification do not necessarily all refer to the same feature, example, and / or limitation. Furthermore, particular features, structures, or characteristics may be combined into one or more examples and / or features.

[0092] In the foregoing detailed description, numerous specific details have been set forth to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will appreciate that the claimed subject matter may be practiced without these specific details. In other cases, methods and apparatus known to those of ordinary skill in the art have not been described in detail in order to avoid obscuring the claimed subject matter. Therefore, it is intended that the claimed subject matter is not limited to the specific examples disclosed, but that such claimed subject matter may also include all aspects falling within the scope of the appended claims and their equivalents.

[0093] Those skilled in the art will appreciate that other modifications may be made to the apparatus and methods of the present disclosure to achieve various applications of the method and system for an enhanced area getter architecture for wafer level vacuum packaging of uncooled focal plane arrays without departing from the scope of the present disclosure.

[0094] The examples and embodiments described herein are for exemplary purposes only. Various modifications or changes thereto will be apparent to those skilled in the art. These modifications or changes will be included within the spirit and scope of the present application and within the scope of the appended claims.

Claims

1. A transformer, comprising: a magnetic core having a central region; a primary winding extending around the central region; a first secondary winding comprising a first conductor having one or more first turns extending around the central region, wherein the first conductor has a first width and is arranged to receive electromagnetic flux from the primary winding; and A second secondary winding comprising a second conductor having one or more second turns extending around the central region, wherein the second conductor has a second width and is arranged to receive electromagnetic flux from the primary winding, wherein the number of the one or more second turns is greater than the number of the one or more first turns and the first width is greater than the second width. 2 . The transformer of claim 1 , wherein the magnetic core defines a winding region that is concentric with the central region and has a predefined width to receive the first secondary winding and the second secondary winding. The transformer of claim 2 , wherein the predefined width is greater than the second width of the second conductor. The transformer of claim 2 , wherein the second width is greater than 50% of the predefined width. The transformer of claim 2 , wherein the second width is greater than 75% of the predefined width. The transformer of claim 2 , wherein the second width is greater than 90% of the predefined width.

7. The transformer of claim 1, wherein the first secondary winding is located on a first layer and the second secondary winding is located on a second layer.

8. The transformer of claim 1, wherein at least a portion of the first secondary winding and the second secondary winding are located on a same layer.

9. An inductor comprising: a magnetic core having a central region; and A conductor has a first winding extending around the central region and a second winding extending around the central region, wherein a first width of the conductor in the first winding is greater than a second width of the conductor in the second winding. 10 . The inductor of claim 9 , wherein the magnetic core has a predefined width to receive the first winding and the second winding.

11. The inductor of claim 9, wherein the first winding is an outer winding and the second winding is an inner winding. 12 . The inductor of claim 9 , wherein the conductor further comprises a third winding extending around the central region and having the first width.

13. The inductor of claim 9, wherein the second winding is located between the first winding and the third winding.

14. The inductor of claim 9, wherein the magnetic core defines a winding region concentric with the central region and having a predefined width to receive the first winding and the second winding.

15. The inductor of claim 10, wherein the first width is at least 75% of the predefined width.

16. The inductor of claim 10, wherein the first width is at least 90% of the predefined width.

17. A method of forming a transformer, the method comprising: providing a magnetic core having a central region; forming a primary winding extending around the central region; forming a first secondary winding comprising a first conductor having one or more first turns extending around the central region, wherein the first conductor has a first width and is arranged to receive electromagnetic flux from the primary winding; as well as A second secondary winding is formed, the second secondary winding comprising a second conductor having one or more second turns extending around the central region, wherein the second conductor has a second width and is arranged to receive electromagnetic flux from the primary winding, wherein the number of the one or more second turns is greater than the number of the one or more first turns and the first width is greater than the second width.

18. The method of claim 17, wherein the magnetic core defines a winding region concentric with the central region and having a predefined width to receive the first secondary winding and the second secondary winding. The method of claim 18 , wherein the predefined width is greater than the second width of the second conductor.

20. The method of claim 18, wherein the second width is greater than 50% of the predefined width.

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