Isolated DC/DC converter by Alps Alpine Develops is based on magnetic material

Based on Alps Alpine’s magnetic material, Li-qualloy sup, the Isolated TriMagiC converter has been developed to explore possibilities for small, high conversion efficiency power without increasing operating frequency.

The Li-qualloy sup material replaces ferrite magnetic components in trans-formers and resonant coils. In a circuit, the material operates in on/on and on/off mode simultaneously to enable both high peak conversion efficiency of 96.8 per cent and a compact size. The total size of magnetic components comes to one third that of existing methods, even with high output power of 3.3kW, says Alps Alpine. The high output power ensures compatibility with the high power requirement for autonomous driving and in-vehicle entertainment systems and the compact size and high conversion efficiency contribute to space efficiency and reduced power consumption in electric vehicles (EVs). Samples are to be made available for evaluating performance of components by April 2022.

Home appliances and other electronics use different types of electricity (AC or DC) and voltages depending on what is best for the function they are performing. They therefore need to convert electrical power in a manner suited to the application and purpose. Nearly all electronic devices run off a direct current so DC/DC converters play a vital role in converting the supplied DC power voltage into an optimal DC voltage that varies with the application. Heat generation during power conversion results in power loss, so improving power conversion efficiency to reduce that power loss leads to energy efficiency.

For EVs, lithium-ion (Li-Ion) batteries are the dominant type of main battery. They employ a direct current with a high voltage of around 400V, while electronic devices drawing from that power supply, including navigation systems, headlights and power windows, run off low voltage DC of around 12V. The voltage conversion is performed by an automotive DC/DC converter, or auxiliary converter.

For EVs to become more widely adopted, the batteries will require larger capacities while the vehicles themselves must be light and have efficient power conversion for longer driving range. They must also serve increased power demands from automated driving systems and in-vehicle entertainment systems. 

For safety reasons, automotive DC/DC converters are generally isolated types to prevent electric shock. Existing isolated DC/DC converters are broadly categorised as either on/off type converters with low output power and compact with a small number of parts, or they are on/on type converters with high output power but more parts and therefore larger dimensions, explains Alps Alpine. In automotive applications, on/on type converters have been used since large loads demand high output power (at least 1kW). These on/on converters however need higher operating frequencies to enable compact dimensions and the problem of diminishing power conversion efficiency.

The Isolated TriMagiC Converter circuit technology contains three magnetic components: two transformers and a resonant coil for zero voltage switching (ZVS). With current input from a bridge circuit, the two transformers repeatedly alternate between on/on and on/off operations. The transformers simultaneously output and store energy from the input side during both on/on and on/off operations, and flux density increases around half as much as with an ordinary on/off type converter, says the company. The storing operation eliminates the need for a smoothing coil. The high saturation flux density of Liqualloy allows for smaller magnetic components and therefore a more compact circuit. Changes in flux density are smaller, too, enabling high output power and high conversion efficiency, adds Alps Alpine.

Reference boards (pictured) are being prepared for release March and April 2022.

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