Miniaturization yields high-frequency transformers based on flat cores

Initiatives will continue toward the adoption of film and chip cores in high-frequency transformers, with nanocrystalline types further down the R&D roadmap.

Mainland China makers of high-frequency transformers keep up miniaturization pursuits, looking to use new types of cores to achieve smaller configurations and follow the future trend in the line. They target adoption in switching power supplies required in smart lighting, smart home and automotive applications.

Upstream developments have led to the use of soft magnetic materials. The resulting cores can be turned into flat, chip or film form, and ensure low loss, wide operating temperature range and reduced cost.

Local suppliers are now focusing on units with flat cores in their R&D and production. They include Beijing V-Young Tech. Development Co. Ltd and Xiamen YKM Electronics Co. Ltd. Some are also working to develop those based on chip kinds.

For applications above 1MHz, the preference is still for film cores as these can help realize thickness of less than 1mm. Only a few mainland manufacturers can offer such variants of high-frequency transformers at present.

Nanomaterials have also come up in the industry. Nanocrystalline cores are said to boost transformer performance because of their high permeability and saturation induction, and low coercivity and core loss. One domestic company that has released such components is King Magnetics. The cores have 1.25T saturation flux density, less than 0.3T remanence at 20kHz, less than 3.4W/kg core loss at 20kHz/0.2T and more than 20,000 permeability at 20kHz.

Interviewed makers have no immediate plans to develop high-frequency transformers based on this. The adoption of this core type, however, will be a trend in coming years.

Demand for high-frequency transformers has been increasing steadily in the past several years, with total sales climbing at an annual rate of 10 to 15 percent. This is forecast to continue, encouraging most manufacturers to bolster production. Xiamen YKM plans to implement a 10 percent rise in output in 2019 and 2020, which will be supported by its recent acquisition of automatic winding and gluing machines, and testing equipment. The line accounts for 25 percent of the company’s shipments.

There are more than 300 suppliers of high-frequency transformers in the mainland, and over two-thirds are locally owned and the rest with investment from Hong Kong and Taiwan. The major homegrown players include Derui and Hang Tung. More are expected to join the line in the years ahead.

All are also involved in the manufacture of other types of transformers, as well as coils and power supplies. Most plan to raise the portion of high-frequency transformers amid rising orders from the domestic and overseas markets. The key export destinations are still Europe, North America and Asia, but many will increase presence in Russia, the Middle East and South America.

The Pearl River Delta and the Yangtze River Delta regions remain the key production bases for the line. In Guangdong province, the main areas are Shenzhen, Dongguan and Zhongshan, while it is Wuxi in Jiangsu and Ningbo in Zhejiang. There are also a number of makers in the central provinces of Sichuan and Shaanxi, respectively in Chengdu and Xi'an cities.

20 to 200kHz transformers lead

The mainstream selection from local suppliers is categorized by operating frequency range, with those types supporting 20 to 50kHz considered relatively high, 50 to 200kHz medium high, 200kHz to 1MHz high and exceeding 1MHz superhigh. All releases use mainly ferrite cores.

The key specifications include 400/200V voltage ratio and 95 percent efficiency. The products are designed to ensure enhanced protection against EMI and have high EMC. These are CE-approved, RoHS-compliant and UL-listed.

At present, transformers in the first two frequency ranges dominate the output of the majority of makers. For MHz applications, air-core transformers are attracting supplier attention. These types require fewer materials and a short production cycle, and are low-cost.

Customization is the general practice, with up to 50 percent of the passive components based on buyers' specifications.

Most manufacturers usually turn to local providers of ferrite cores, coils, bobbins, cases, copper foil tape, copper, wires and glue. They source from Japan, Germany and Taiwan only when required.

The cost of materials and components rose to a certain extent in previous months, pushing prices of high-frequency transformers by 5 to 10 percent. In the near term, both are expected to stabilize.

The products in this gallery have been handpicked by our mainland China-based market analyst for representing current trends in high-frequency transformers from mainland China and Taiwan makers.

Horizontal-mount 1.15mH transformer

Beijing V-Young Tech. Development Co. Ltd markets this horizontal-mount high-frequency transformer, EFD20 model, with 5+5 pins. The unit has 1.15mH inductance, and meets CE, FCC and RoHS requirements.

The minimum order quantity is 100 units. Delivery is within 10 days.

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High-frequency transformer supports 1 to 3,000W

The ER2510 model from Chipsen Electronics Technology Co. Ltd is a high-frequency transformer operating on more than 1kHz. It has 0.5 to 5,000V output voltage, 0.01 to 100A output current and 1 to 3,000W output power. The unit, which meets CQC, RoHS and UL guidelines, operates in -40 to 125 C.

The 500-unit minimum order is delivered within 15 days.

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Transformer for 40kHz applications

The model ER28 transformer from Showwell Group Co. Ltd has 40kHz frequency, 90 to 230V input voltage and 4.5V, 5A output.

The negotiable minimum order has a delivery lead time of 7 days.

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Transformer operates on 20 to 500kHz

This high-frequency transformer from Xiamen YKM Electronics Co. Ltd, EDR42 model, operates on 20 to 500kHz and has a withstand voltage of 4kVAC/min. The 16mm unit with more than 95 percent efficiency uses class B or F insulation, and meets CE and UL guidelines.

The required minimum order of 100 units is delivered within12 days.

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