1 Introduction The development of power electronics technology depends on major power electronic components, such as electronic switching components, rectifier components, and control components. Magnetic components, as one of the supporting components, also have an undeniable impact on power electronics technology. Magnetic components can be categorized according to their functions as follows: (1) Power transformers that perform power transmission, voltage transformation, and insulation isolation, including rectifier transformers, inverter transformers, and switching power supply transformers. (2) Pulse transformers, trigger transformers, and drive transformers that perform control switching, pulse transformation, and insulation isolation. (3) Phase conversion transformers, frequency conversion transformers (ferromagnetic frequency multipliers and frequency dividers), voltage regulators, current regulators, and parameter transformers that perform electrical parameter transformation and stabilization. (4) Filter inductors, noise and spike absorption inductors that suppress ripple, sudden changes, EMI, and noise. (5) Current transformers, voltage transformers, and Hall current and voltage detectors that perform current and voltage signal transformation and detection. For a period of time, magnetic components in power electronics were called special transformers and special inductors to distinguish them from power transformers and power inductors. Later, due to the development of power electronics technology, electronic technology encompassed a wide range of frequencies and power levels, becoming a unified whole including microelectronics, radio electronics, and power electronics. Therefore, magnetic components in power electronics are grouped together with magnetic components in other electronic technologies, and since transformers play a dominant role, they are all referred to as "electronic transformers." Magnetic components in power electronics are a part of electronic transformers. The demands placed on magnetic components by the development of power electronics technology are the driving force behind the development of electronic transformers. The development of electronic transformers, in turn, provides a strong foundation for the development of power electronics technology. Especially in the last decade, new advancements in soft magnetic materials and core structures used in magnetic components have significantly improved their performance, promoting the high-frequency and miniaturization of power electronics technology and solving some key challenges. To ensure the rapid development of both power electronics and electronic transformers in my country, information exchange between the two industries will play a positive role. The editorial department of *International Electronic Transformers* compiled materials to write "New Advances in Magnetic Components in Power Electronics Technology," hoping to strengthen communication and connections with the power electronics industry. We also sincerely invite power electronics experts and workers to share the requirements and information of various magnetic components in power electronics technology through *International Electronic Transformers*, so that electronic transformers developed and manufactured can better meet the requirements of the power electronics industry. 2. New Advances in Soft Magnetic Materials for Magnetic Components Soft magnetic materials used in magnetic components in power electronics technology include silicon steel, soft magnetic ferrites, high-permeability iron-nickel alloys (permalloy), amorphous and nanocrystalline alloys, as well as magnetic powder cores and thin films. The following sections introduce the latest advancements in soft magnetic materials over the past decade. 2.1 Silicon Steel Silicon steel is a commonly used soft magnetic material in low-frequency, high-power magnetic components in power electronics technology. Over the past decade, improvements have been made by adjusting silicon content, reducing thickness, and refining manufacturing processes, resulting in continuously improved performance. Its operating frequency range has expanded from power frequency to 400Hz–10kHz (medium frequency), and even reached 200kHz–315kHz (high frequency). It is used not only in high-power power transformers but also in high-frequency, low-power switching power transformers that prioritize small size and environmental adaptability. Increasing the silicon content in silicon steel from 3% to 6.5% optimizes its performance, increasing permeability, reducing losses, and decreasing the magnetostriction coefficient. However, this increase also reduces the elongation of the silicon steel, making direct production via rolling impossible. In the early 1990s, Japan successfully developed a large-scale production process for 6.5% silicon steel strip using chemical deposition. By 1998, mass production of 0.50–0.05mm thick 6.5% silicon steel with a maximum width of 640mm was possible. In 2001, my country also successfully trial-produced 6.5% silicon steel. It can be widely used as a soft magnetic material in mid-frequency magnetic components ranging from 400Hz to 10kHz. For example, 0.1mm thick 6.5% silicon steel has a loss of 5.7w/kg at 400Hz and 1T, while 0.1mm thick 3% silicon steel has a loss of 7.2w/kg. At 10kHz and 0.1T, the loss is 8.3w/kg for 0.1mm thick 6.5% silicon steel and 18w/kg for 0.1mm thick 3% silicon steel. This means that when using them to manufacture mid-frequency power transformers, under the condition of ensuring a certain loss, the working magnetic flux density of 6.5% silicon steel is higher than that of 3% silicon steel, requiring less iron. Furthermore, the magnetostriction coefficient of 6.5% silicon steel is approximately 0.1×10⁻⁶, which is 8 times smaller than that of 3% silicon steel, and can reduce audible noise in the 400Hz–40kHz mid-frequency range, which is sensitive to human hearing. Japan has manufactured a 200KVA 400Hz intermediate frequency power transformer using 0.1mm thick 6.5% silicon steel. The magnetic flux density is 0.5T, the iron content is 250kg, the copper content is 125kg, and the total weight is 420kg, with an audible noise level of 70dB. Using 0.1mm thick 3% silicon steel, the magnetic flux density is 0.3T, the iron content is 320kg, the copper content is 160kg, the total weight is 550kg, and the audible noise level is 80dB. Simultaneously, in 1998, Japan used the same chemical deposition process to produce low-remanence silicon steel with a gradient silicon content distribution. The magnetic flux change ΔB can reach approximately 1.2T, far exceeding the 0.5T of 3% silicon steel, and can be used in high-power pulse transformers. Reducing the thickness of the silicon steel strip can decrease eddy current losses. By the 1990s, the thickness of cold-rolled silicon steel used in high-power 50Hz magnetic components had decreased from 0.35mm to 0.23mm, resulting in a reduction of 0.12–0.15 W/kg in losses at 50Hz and 1.7T. In the early 1990s, a triple recrystallization rolling and processing technology was adopted to produce thin silicon steel with thicknesses of 0.081mm and 0.032mm, overcoming the drawback of decreasing saturation magnetic flux density with thickness, while maintaining a value of 2.03T. At 50Hz and 1.7T, the losses for 0.081mm thick silicon steel were 0.37 W/kg, and for 0.032mm thick silicon steel, they were 0.21 W/kg, a significant decrease compared to the 1.02 W/kg for 0.30mm thick silicon steel. Not only can silicon steel achieve the lowest possible loss levels in 50Hz high-power magnetic components, but its operating frequency can also be extended to over 20kHz. Reports have already emerged of silicon steel being used in high-frequency magnetic components ranging from 200kHz to 315kHz. Since the 1990s, various countries have invested significant resources in researching the domain refinement process for silicon steel. Current achievements include a further reduction of 0.1w/kg loss in 0.23mm thick silicon steel at 50Hz and 1.5T. Japan has finalized mass production for its next-generation energy-saving power transformers, reducing no-load losses by approximately 30%. It is estimated that similar energy-saving effects can be achieved when used in rectifier transformers. my country is currently piloting this domain-refined silicon steel. 2.2 Soft Ferrite Soft ferrite is a commonly used soft magnetic material in medium- and high-frequency, low-power magnetic components in power electronics technology. It features high resistivity, ease of mass production, stable performance, and the ability to be molded into various cores, especially its low cost. However, processing large soft ferrite cores is difficult, and the products are easily broken, limiting their power applications. Soft ferrite has a low saturation magnetic flux density, and its use is rarely seen in the 50Hz–1kHz frequency range. Some believe that soft ferrite toroidal cores, lacking air gaps, will not produce audible noise in the audio frequency range, but this is a misconception. The magnetostriction coefficient of soft ferrite is much greater than that of silicon steel, resulting in significant audible noise in the audio frequency range. In the early 1990s, a detailed study was conducted on the mechanism of loss variation in soft ferrite with frequency. It was found that there is an optimal operating frequency where losses are lowest. There is also a limiting operating frequency; beyond this, losses remain consistently high. Therefore, the fourth-generation soft magnetic ferrite products developed in the 1990s, such as Japan's TDK H7F (PC50) and China's R1.4K, have an optimal operating frequency of 1MHz, a maximum limiting operating frequency of 3MHz, and a performance factor (Bxf) of 25000, meaning that the operating magnetic flux density at 1MHz is 25mT, a significant improvement over the third-generation products of the 1980s. Third-generation products, such as Japan's TDK H7C4 (PC40) and China's R2KB1, have an optimal operating frequency of 300kHz, a maximum limiting operating frequency of 1MHz, and a performance factor of 15000. In recent years, efforts have been made to improve the performance of soft magnetic ferrites by changing additives and processes to refine the powder. However, the degree of powder refinement is limited by the magnetic domain size, making it quite difficult to further increase the operating frequency of soft magnetic ferrites. Therefore, new approaches have been sought, turning to magnetic composite materials and nanomaterials. 2.3 High-permeability iron-nickel alloys (permalloy) High-permeability alloys are characterized by high permeability, low loss, and strong environmental adaptability, but their disadvantage is their high price. It has significant advantages in the use of magnetic components for signal detection in power electronics technology. It is also widely used in military products with stringent environmental requirements. To reduce costs, a low-nickel Ni38Cr8Fe alloy was developed in 1992, achieving the performance of a high-nickel Ni80Mo5 alloy, with an initial permeability of 1–3 × 10⁶ at 0.4 A/m. Starting in 1996, foreign companies such as the German Vacuum Smelting Company developed initial permeabilities of 2–3 × 10⁶, sparking a surge in demand for improved permeability. China has also developed corresponding products, the 1J77A and 1J851A alloys. These not only have high permeability, improving the accuracy and sensitivity of magnetic components, but also exhibit low losses; a 0.02 mm thick alloy has a loss of 28 W/kg at 0.5T 20 kHz, and has been used in a 20 kHz 1 KVA power transformer. High-permeability alloys can be rolled into ultra-thin strips less than 0.02 mm thick. The production process is relatively simple and the cost is relatively low; alloy strips as thin as 0.005 mm are now possible. A 0.005 mm thick Ni80Mo5 alloy strip has a loss of 0.392 W/kg at 0.1T 1MHz and 23.1 W/kg at 10MHz, making it suitable for power transformers and saturated inductors (magnetic amplifiers) above 1MHz. This breaks the old notion that high-permeability alloys can only be used in magnetic components below 20kHz. Its cost is also lower than ultra-thin silicon steel strips, amorphous alloys, and nano-alloys, making it competitive in the market. 2.4 Amorphous and Nanocrystalline Alloys Amorphous alloys, developed since the late 1960s, and nanocrystalline alloys, developed from amorphous alloys since the late 1980s, have become research hotspots for soft magnetic materials used in power electronics components in the past decade, achieving significant progress not only in materials and processes but also in applications. The following are some prominent examples. The application of iron-based amorphous alloys in low-frequency, high-power magnetic components has reached a peak. In power transformers, the number of units increased from less than 10,000 in the early 1990s to over one million by the late 1990s. Besides power transformers, there are also applications in rectifier transformers, inverter transformers, and filtrate transformers. In 1999, comparative experimental results on the effects of high-order harmonics on the losses of iron-based amorphous alloys and silicon steel were reported. In power transformers with a distortion of 5%, the loss of silicon steel cores increased to 106%, while the loss of amorphous alloy cores increased to 123%. In rectifier transformers with a distortion of 75%, the loss of amorphous alloy cores increased to 160%, yet they could still operate; the loss of silicon steel cores increased to over 300%, causing severe overheating and requiring cooling measures. This demonstrates that iron-based amorphous alloys are more suitable than silicon steel for use in low-frequency, high-power magnetic components in power electronics. Currently, transformers made with iron-based amorphous alloy cores generally have a capacity below 630KVA, with the largest reaching 2500KVA. After nearly a decade of effort, the operating magnetic flux density has increased from 1.25T to 1.35–1.40T. The fill factor has increased from 0.70 to 0.85. The price of strip material has decreased from 600% to 150% of that of silicon steel. The price of magnetic cores has reached approximately 26 yuan/kg, approaching the price of wound silicon steel cores. No-load losses are reduced by 60%–80% compared to silicon steel. It is projected that within the next decade, iron-based amorphous alloys will gradually expand their application in magnetic components in power electronics technology, reaching a market share of approximately 30%. Currently, the thickness of iron-based amorphous alloys is 25–40 μm, with a fill factor of approximately 0.85. Since 1995, FiSiB-based iron-based amorphous alloys with thicknesses of 150–250 μm and bulk amorphous alloys have been developed, which can increase the fill factor to 0.95, reaching the current level of silicon steel cores. Bulk amorphous alloys can be used in very low frequency magnetic components to reduce losses. Since 1990, Japan has vigorously pursued research on FeMB-based (M can be Zr, Hf, or Ta) amorphous alloys and FeZrNbBCu-based nanocrystalline alloys, commercially known as "Nanoperm". Its losses are lower than FeSiB-based iron-based amorphous alloys, with a loss of approximately 0.14 W/kg at 1.4 T and 50 Hz. The saturation magnetic flux density is increased to 1.70 T, and the magnetostriction coefficient decreases to below 0.3 × 10⁶, making it a relatively ideal soft magnetic material for low-frequency, high-power applications to date. Japan has collaborated with industry, academia, and research institutions to develop a prototype low-frequency, high-power transformer, with mass production expected in 2003 and 2005. In 1998, the United States developed a FeCoZrBCu-based amorphous alloy, commercially known as "Hitperm," with a saturation magnetic flux density as high as 2.0 T and relatively low losses. It can replace current iron-cobalt-vanadium alloys in low-frequency, high-power magnetic components requiring small size and weight. The past decade has seen fierce competition between amorphous and nanocrystalline alloys and soft magnetic ferrites for the high-frequency magnetic component market in power electronics, particularly in the high-frequency range above 100kHz. Due to improved processes and the addition of elements, cobalt-based amorphous and iron-based nanocrystalline alloys have been able to produce thin strips smaller than 20μm. Cobalt-based amorphous alloy strips exhibit losses of 0.1–0.4 W/kg at 0.1T and 1MHz. Nanoperm-type nanocrystalline alloy strips show losses of approximately 1.15 W/g at 0.2T and 1MHz, the lowest reported level to date. Thus, in the 500kHz–1MHz range, the operating magnetic flux density can reach 0.2–0.1T, while soft magnetic ferrites only require 0.05–0.025T, reducing losses, size, and weight of mid-to-high-frequency magnetic components compared to soft magnetic ferrites. 2.5 Magnetic Powder Cores Magnetic powder cores are typically toroidal, formed by pressing a mixture of soft magnetic metal powder and insulating material. Because the soft magnetic powder is surrounded by insulating material, forming a dispersed air gap, it increases resistivity, reduces high-frequency eddy current loss, and has anti-saturation properties, making it mainly used as the magnetic core of inductors in power electronics technology. Besides ferromagnetic powder cores, iron-nickel-molybdenum powder cores, and iron-silicon-aluminum powder cores, amorphous and nanocrystalline powder cores began to be researched in the mid-1990s. The effective permeability measured at 10kHz is 20–800, wider and with a higher maximum value than other current powder cores. Under 0.1T, 20kHz conditions, the loss is 10–25 W/cm³, lower than existing powder cores, which can reduce heat generation and temperature rise. 2.6 Thin Films The development of power electronics technology to frequencies above 1MHz can greatly reduce the size and weight of power electronic devices. This makes them suitable for portable communication devices (mobile phones) and personal computers. According to a Japanese electronics magazine, these two types of information transmission and processing devices are currently the main users of high-frequency switching power supplies. However, in the 1MHz to 100MHz, and even 1000MHz range, the losses of existing soft magnetic materials increase rapidly, the processing technology becomes increasingly difficult, and the cost rises. Therefore, as a branch of nanomaterials, magnetic thin films have been developed since 1987 to meet the demands of technological development. Since measuring losses at 1MHz is difficult, permeability is used as the main parameter representing the performance of thin films. In 1998, Japan produced FeNiCo crystalline alloy thin films with a saturation magnetic flux density of 1.8–2.2T using electroplating, achieving a permeability of 1650–2200 at 10MHz, suitable for use in 10MHz magnetic components. Later, FeNi and FeNiMo crystalline alloy thin films were developed, exhibiting higher resistivity and suitable for use in 10MHz–30MHz magnetic components. Amorphous alloy thin films were reported in the early 1990s, using CoZr thin films as magnetic cores to fabricate power transformers, filter inductors, and pulse-width modulation saturable inductors to form 1MHz switching power supplies. Later improved CoZrRe thin films achieved a permeability of 3000 at 10MHz and a loss of 1.2 W/cm³ at 0.1T and 1MHz, only about 1/6 that of soft magnetic ferrites, and have been successfully used in 32MHz switching power supplies. It is worth noting that thin films are nanomaterials, and their performance is significantly improved compared to amorphous alloy thin strips. For example, the saturation flux of cobalt-based amorphous alloy thin strips is 0.6–0.8T, while that of cobalt-based amorphous thin films can reach 1.6T. Since the thickness of thin films is generally less than 5μm, nanocrystals are easily formed, therefore, more nanocrystalline thin films were developed in the 1990s than amorphous thin films. Among them, FeMc (or CoMc) nanocrystalline thin films, commercially known as "Nanomax," are widely used as magnetic head materials. With a Bs of 1.48–1.72T and a permeability of 670–6500 at 1MHz, they can be used in switching power supplies at around 1MHz. Nanoperm-type nanocrystalline FeZrB thin films maintain a permeability greater than 1000 at 50MHz, making them suitable for use in 10MHz–50MHz power supplies. Nitriding can improve resistivity while maintaining relatively high permeability at high frequencies. In 1994, South Korea successfully developed FeHfCn thin films achieving a permeability of 7800 at 1MHz and maintaining around 1000 at 100MHz, pushing the operating frequency up to 100MHz. Reducing the film thickness can further decrease eddy current losses, and several or even a dozen magnetic films can be bonded together to form multilayer films. For example, [FeHfC/Fe] multilayer films increase the permeability from 4310 to 6000 at 1MHz and maintain this level up to 100MHz, exhibiting a considerably high permeability. Multilayer films composed of alternating magnetic and non-magnetic films have even higher resistivity and can operate at frequencies exceeding 100MHz. For example, the [CoFeB/SiO2] multilayer thin film developed in Japan in 1999 has a permeability of 300-450 μm at 800 MHz. It has been used as a core to fabricate GH2-level inductors, with inductance more than 20% higher than similar air-core inductors. Currently, microfabrication methods are used to disperse Fe or Co and their alloys into non-magnetic materials to form nanoparticle thin films. Internationally, this is called composite magnetic nanomaterials, and it is a major research topic in magnetic materials. For example, FeHfO particle thin films have a permeability of 700-1400 μm at 100 MHz, and remain at 100-500 μm at 100 MHz, with a resistivity of 410-1100 μm. They are now used in mobile phone power supplies. 3. New Developments in Core Structures for Magnetic Components 3.1 Core Structures for High-Capacity Low-Frequency Magnetic Components To reduce leakage flux and losses, since the late 1980s, there have been several new developments in wound core structures for high-capacity low-frequency magnetic components. Firstly, the R-type magnetic core structure has been widely used in low-frequency applications, leading to the development of R-type transformers. Capacities range from 10VA to 630VA. They can be used as control transformers, power transformers, and even general power transformers. The characteristics of R-type magnetic cores are their nearly circular cross-section; the frame can be toroidal or rectangular. Due to low magnetic leakage, R-type magnetic cores made of silicon steel have lower excitation current and losses approximately 30% lower than cores made of laminations or sheared sheets. The disadvantages are that cutting and winding silicon steel strips requires specialized equipment. Annealing large R-type magnetic cores is difficult to master. Coil winding also requires specialized equipment, and only one coil can be wound at a time, resulting in low efficiency in mass production. Therefore, in the production of small transformers below 100VA, when the annual production volume reaches over 100,000 units, there is a growing trend towards using laminations instead of R-type magnetic cores. This allows for the simultaneous winding of 8 to 16 coils, significantly improving production efficiency, eliminating the need for specialized equipment, and reducing costs. Secondly, a lap-type magnetic core structure emerged. Unlike wound cores, which are not continuously wound but rather composed of dozens of overlapping layers, the overlapping portions are evenly distributed on the upper or lower part of the core's frame. This allows the coils to be wound individually or in batches, similar to lamination cores. Single-phase transformers use one frame for the lap-type core, while three-phase transformers use four frames (two large frames and two small frames) for the lap-type core. During assembly, the overlapping layers can be gradually opened, the coil inserted, and then gradually closed again. This type of lap-type core was first used in amorphous alloy transformers and later also in silicon steel transformers. Capacities range from 5KVA to 2500KVA, primarily used as power transformers, but also as power transformers in power electronic devices. Furthermore, the spatial arrangement of wound cores has also seen new variations. Besides the planar arrangement of three frames (two small frames and one large frame) and four frames (two large frames and two small frames), there are also three-dimensional arrangements such as triangular three-frame and radial three-frame structures. The triangular three-frame arrangement features three identical cores, making the core easier to process and heat-treat. However, the winding requires a specialized frame, which doesn't fully utilize the enclosed cross-section. This arrangement results in less material weight and lower losses. However, it increases the average turn length of the coil, leading to increased copper losses. The radial three-frame arrangement is suitable for saturated reactors, reducing the average turn length and resistance of the control winding and decreasing the control time constant. It is also suitable for magnetic third harmonics used in transformer inter-turn testing equipment. It offers significant advantages over parallel or three-frame core arrangements, reducing both copper usage and copper losses. 3.2 Low-Height Core Structures In the mid-1990s, the rapid development of portable communication devices (such as mobile phones) and computers (such as personal computers) required magnetic components with heights below 20mm, leading to a series of low-height core structures. The first generation of low-height core structures used planar transformers and inductors. Toroidal cores with a height reduced to less than 20mm, while maintaining the same cross-section, can be made of soft magnetic ferrite, high-permeability permalloy, or amorphous/nanocrystalline alloys. E-shaped cores, after reducing height, come in two forms: one with the cross-section unchanged, maintaining a large window for easy winding and heat dissipation; the other with an increased cross-section and a reduced window. This allows for a reduction in the number of turns, enabling the windings to be manufactured using copper foil and reducing surface-effects. Planar transformers and inductors already in production range from 50 kHz to 2.5 MHz, using high-permeability, low-loss ferrite cores. Capacities range from 5W to 20KW. Capacities vary depending on the operating frequency. For each core size, there is a maximum capacity operating frequency range, which should be considered during use. The second generation of low-height magnetic core structures consists of surface-mount transformers and inductors. Due to advancements in surface-mount technology, even lower-height surface-mount transformers and inductors have emerged. These low-height cores are also divided into wound and multilayer types. Wound-type surface-mount transformers and inductors use smaller cores to wind coils. Multilayer chip transformers and inductors are made by stacking several layers of magnetic, conductive, and insulating materials. Both types of chip transformers and inductors are mass-produced, with annual outputs exceeding hundreds of millions of units. The third generation of low-height magnetic core structures consists of thin-film transformers and inductors. They are manufactured using microfabrication technology similar to semiconductor integration. The core material uses various thin-film magnetic cores, and the conductive and insulating materials of the coils are also made from various thin-film materials. The height is less than 5mm, with some reaching 1mm, allowing them to be directly installed in various cards with a thickness of 1.5–2mm. 3.3 Composite Core Structure Composite core structures have two types. The first type uses the same magnetic material to make two or more parts, which are then assembled to form a single core. One purpose is to ensure that the performance of the cores tends to be at the same level or within a specified range after matching. In some cases, one part has no air gap, while another part has an air gap, to meet the performance requirements of the magnetic components at various stages. The second type uses different materials (including magnetic and non-magnetic materials) to create two or more parts, which are then assembled into a magnetic core to obtain various required magnetic and electrical properties. Strictly speaking, a magnetic powder core is this type of composite magnetic core structure. It is made by mixing iron powder, permalloy powder, iron-silicon-aluminum powder, amorphous alloy powder, and insulating binder, and then pressing them into a magnetic core to obtain different permeabilities and different constant magnetic properties. Currently, there is a growing trend of dispersively embedding nanoscale magnetic particles in insulators to obtain high-permeability, high-resistivity composite magnetic core structures, which can be used in magnetic components operating at frequencies from tens of MHz to GHz. This composite magnetic core structure and composite magnetic material have become a hot topic in the development and research of high-frequency magnetic components, attracting widespread attention and potentially replacing soft ferrite as the mainstream high-frequency magnetic material and core structure. 3.4 Integrated Magnetic Core Structure Integrated magnetic cores have two meanings. The first meaning, expressed by CuK when proposing integrated magnetic cores, refers to a single magnetic core integrating the functions of two or more magnetic cores (such as transformers and inductors). Figure 6 illustrates this, showing a transformer core on one side and an inductor core on the other, both integrated onto a single core. With the development of high-frequency switching power supplies, the first type of integrated core structure has evolved into various varieties and is now practically applied. The second type integrates several or more cores together, along with semiconductor components and resistors/capacitors, forming a core-centric integrated circuit, such as a monolithic switching power supply. This type is not significantly different from general integrated circuits, except that integrated circuits include magnetic components not found in general integrated circuits. 3.5 Vertical Core Structure The vertical core structure, also called orthogonal core structure, consists of two C-shaped core halves, but instead of being directly connected, one half is rotated 90 degrees before being connected. A control winding is wound on the 90-degree rotated half, and current is passed through it to control the inductance of the other half of the core. Using this vertical core structure, AC voltage regulators, inverters, and DC high-frequency switching power supplies have been developed. Sony Corporation of Japan has developed various high-frequency switching power supplies for televisions using this vertical magnetic core structure, achieving relatively ideal performance at a lower price. 4. New Advances in the Performance of Magnetic Components 4.1 High Reliability Magnetic components consist of a magnetic core, wires (copper), insulating materials, and structural materials. They have no moving or easily damaged parts and are generally considered highly reliable. In recent years, there has been a new understanding of reliability. High reliability has two meanings. The first meaning is the ability to operate under specified working conditions. Specified normal working conditions include both general and special working conditions. Therefore, magnetic components used in special fields must undergo special environmental tests, including nuclear radiation tests, ultra-high temperature tests, and ultra-low temperature tests. The second meaning is the ability to operate under specified working conditions until the end of their service life. The main factor affecting service life is the insulating material. For many magnetic components operating at high frequencies and high temperatures, it is advisable to use insulating materials with high temperature resistance ratings, such as Class C Nomex and its products. This not only ensures service life but also reduces size, making it a feasible option considering all factors. Although the reliability of magnetic components is widely recognized, recent advancements in reliability understanding over the past decade have elevated their reliability to new levels. These components can now be used in special environments, guarantee a sufficient service life (typically 20 years), and require virtually no maintenance during their lifespan. This further emphasizes the high reliability of magnetic components. 4.2 High Efficiency Many electronic devices have placed higher demands on efficiency in recent years. Besides ensuring high efficiency under rated operating conditions, high efficiency must also be guaranteed in standby mode. Standby mode is generally defined as one-tenth of the load under rated conditions. In this near-empty state, the losses of magnetic components account for a large proportion; therefore, high efficiency performance of magnetic components is even more crucial. The efficiency of electronic devices in standby mode is 90%, of which the efficiency of magnetic components must exceed 95%. Otherwise, considering other losses, the efficiency of electronic devices in standby mode cannot be guaranteed to reach 90%. The main factor affecting the efficiency of magnetic components in standby mode is iron loss. Methods to improve efficiency include using low-loss magnetic materials and improving heat treatment processes. Therefore, loss at a certain operating frequency and operating magnetic flux density has become a major indicator for evaluating magnetic materials. [b]4.3 Low Noise[/b] In recent years, with increasing emphasis on environmental protection, low electromagnetic noise has become an important performance indicator for magnetic components. Magnetic components operating in the audio range also require low audible noise. The main factor generating electromagnetic noise in magnetic components is the magnetostrictive effect of magnetic materials. Therefore, in some application areas, using hollow components or piezoelectric ceramic components instead of magnetic materials can significantly reduce noise. The main method for reducing electromagnetic noise is to adopt various shielding measures, which have made significant progress in the past decade. On the other hand, many magnetic components are used to absorb electromagnetic interference from electronic equipment, thus bringing corresponding market opportunities to magnetic components and promoting their development. 4.4 Low Cost As part of electronic products, magnetic components are also commodities and cannot avoid the market's pursuit of low cost. In the past decade, with the gradual clarification of the domestic market understanding, products that only pursue high functionality while ignoring cost have increasingly lost their market and vitality. Now, the emphasis is on pursuing low cost while ensuring "appropriate" functional indicators. Sometimes, low cost even becomes a decisive performance indicator. Why do high-permeability alloy strips still have a place in high-frequency magnetic components? Why do soft magnetic ferrites firmly occupy the market for mid-to-high-frequency magnetic components? Why do small power transformers no longer use R-type magnetic core structures but instead revert to E-type magnetic core structures? Why have magnetic powder cores been rapidly adopted in inductors in recent years? These are all determined by low cost. Products that pursue perfection and excessively high performance indicators without considering the principle of low cost will sooner or later be punished by the market. There have been too many such lessons in the past decade. Many "energy-saving but not cost-effective" products have been slow to be accepted by users. Therefore, it is hoped that everyone understands this point: only new magnetic materials, new magnetic core structures, and new performance characteristics that meet the market's demand for higher performance-price ratios can be considered new advancements in magnetic components. This is the starting point for those engaged in the development and research of magnetic components.