Small, low-profile transformers dominate recent releases

Years of miniaturization have turned bulky and heavy electronic transformers into lightweight components with a small footprint and a slim profile, matching trends in circuits that continue to grow in density. Widely used in LED lighting, power supplies, consumer electronics, and medical, communications and industrial applications, today's compact transformers also offer better performance, with designs emphasizing low noise and loss, and high efficiency and reliability.

Xi'an Kanghong, for example, has chip-type piezoceramic units, which range in thickness from 1.5 to 2.5mm and are generally used in consumer electronics, lighting and office automation applications. At Shaanxi FKS, there are surface-mount pulse transformers with a 1.98mm profile.

In recent years, product launches from China have included R-core, flat and surface-mounted transformers, which manufacturers will continue pursuing in order to keep up with industry trends. Integrated variants with magnetic thin films, on the other hand, remain on the R&D roadmap for now.

R-core units have a rectangular core with a round cross section, and two separate bobbins for the primary and secondary windings. Because of this structure, which allows uniformly spaced and therefore balanced winding, leakage flux and exciting current are minimal, resulting in lower losses and better efficiency compared to toroidal and EI designs. The configuration also ensures complete isolation for greater safety, and offers flexibility in mounting, which can be in flat or vertical position or sideways. These transformers suit displays, audio products, and office and medical equipment. Electronic transformer specialist Shanghai Hexin is one of the companies in China offering this type of component.

With an inherent low profile, flat-type transformers differ in that they have a modular block holding small square cores and integrating a single-turn secondary winding. This design ensures low core loss and that leakage inductance associated with multiple turns is reduced. Chinese manufacturers such as Shenzhen Belta offer this kind of transformer for use in TVs, lighting and small switching power supplies.

Still relatively uncommon are integrated transformers with thin-film magnetic cores made using standardCMOS manufacturing technology. In a paper published by Columbia University's Bioelectronic Systems Laboratory in 2016, such components have "the highest known volume inductance density of any published result for a monolithic transformer, and are available in commercial CMOS, making them a viable technology option for the design of fully integrated switched-mode DC-DC converters."

But what is widely available in China are SMD transformers, including pot cores or round, RM, EP, E, EI, EEM, EFD, U, UI and ER shapes, for small electronic products.

R&D efforts are also underway further upstream in China's transformer manufacturing industry chain.

One such project being undertaken by Mianyang Kaiyuan focuses on the development of high-performance soft magnetic materials for medium- and high-grade transformers. The company has invested $22.35 million in building an 86,710sqm facility scheduled to start mass production in December 2022. Target annual output is 10,000 tons of the material and 20 million transformers. The supplier currently churns out manganese and zinc soft magnetic ferrites, and high-conductivity soft ferrite core elements.

Market drivers

China's transformer sector is forecast to regain a pre-pandemic growth pace of 5 to 10 percent in exports over the next one or two years. In 2020, shipments to overseas markets reached 2.86 billion units or just a 0.3 percent increase YoY, according to customs statistics.

Suppliers interviewed by Global Sources Electronic Components have an optimistic outlook, banking on higher demand as a result of a wider adoption of 5G, Internet of Things, solar energy and smart living technologies.

Some that were not greatly affected by the pandemic have pushed on with production expansion. Pingyuan Yamaxi New Energy Technology Co. Ltd constructed a 10,000sqm cleanroom manufacturing facility with three production lines to boost its capacity.

China has thousands of suppliers and is a major source of transformers. In addition to homegrown manufacturers, including major companies such as Chint and Jiangsu Huapeng, international players are part of this pool, including Siemens, ABB, Delta, Dee Van, Toshiba and Leader Electronics.

The same suppliers also offer related products such as chokes, filters and power supplies, with transformers representing between 30 and 90 percent of their shipments.

More than 30 percent of these companies are in Guangdong and 16 percent in Zhejiang, according to Chinese consulting firm Newsijie. Jiangsu and Shanghai are also key production hubs, and there are suppliers in Shandong province on the eastern coast of China.

Products by frequency range

High-frequency applications are considered hot in this product category, which is why Chinese companies are set to continue developing small and low-loss transformers.

Transformers that operate at low frequencies such as 50 and 60Hz are widely available, and those at 20Hz to 20kHz. Units in the 400Hz to 1kHz, 20kHz to 100kHz and above-100kHz ranges can also be sourced.

By application, there are power, audio and pulse transformers as well as units specifically designed for switching power supplies and communications products, and special-purpose kinds.

Companies highlight their capability to handle custom specifications, orders based on which account for 30 to 60 percent of their shipments.

All ensure their products meet quality and safety requirements and have CE, RoHS, TÜV and UL approval.

Components and materials, including ferrite cores, copper wires, copper foils, bobbins and tapes, come from domestic or foreign suppliers, depending on buyers' requests. Their costs increased in 2020, but in order to stay competitive the majority of Chinese manufacturers did not adjust product prices. Others, unable to absorb the added pressure of a higher labor outlay, opted to raise their quotes by as much as 10 percent.

The situation may normalize in the coming months. If so, this will lead to more stable costs.

SMD transformer with 350µH OCL

This low-profile SMD transformer from Dragon Well Electronics Co. Ltd, the M2416AG, has 350µH minimum open-circuit inductance at 100kHz, 100mV with 8mA DC bias, and 0.5µH maximum leakage inductance at 100kHz, 0.1V.

Operating temperature is 0 to 70 C. The unit, with a 1:1 turns ratio, is compatible with 10/100/1000 Base-TX PoE transceivers and conforms to IEEE 802.3 standards.

The minimum order is 1,000 units. Delivery takes seven days.

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High-frequency transformer

For switching power supplies, fax machines, TVs and monitors, G-Chen Enterprise Co. Ltd's EFDS_5595163 high-frequency transformer has high inductance, and low distributed capacitance, leakage and power consumption.

Order quantity is negotiable. Lead time is 21 days.

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Double-wound power transformer

With an EE core structure, this PY160216A double-wound power transformer from Hangzhou Assem Technology Co. Ltd suits high-frequency industrial applications. It is RoHS-compliant.

The 1,000-unit minimum order requirement has a lead time of 15 days.

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UL-listed transformer

Pingyuan Yamaxi New Energy Technology Co. Ltd offers this B-5704 transformer that has wide voltage and frequency ranges, high efficiency, and low temperature rise and power consumption. The unit meets CB, CE, CQC, UL and VDE requirements.

An order of at least 5,000 units is required. This has a 15-day lead time.

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