GaN switch cuts adaptor size in new way

October 30, 2020 //By Nick Flaherty
GaN switch cuts adaptor size in new way
The MinE-CAP is a system-in-package (SIP) GaN switch that reduces the size of the capacitor bank in power adaptors up to 75W

Power Integrations has developed a GaN-based switch that can dramatically cut the size of a power adaptor. This could lead to USB converters small enough to fit into wall sockets.

The MinE-CAP is multiple devices, including a gallium nitride (GaN) switch, in a package that manages the high and low voltage lines separately. This allows for lower voltage bulk electrolytic capacitor banks, slashing the size of power adaptors in the 25W to 75W by 40 percent.

“We see more demand for fast charging and larger batteries,” said Chris Lee, product marketing director at Power Integrations. “For example, Oppo ships with 65W charger that was previously used to power a laptop. The increasingly complex protocol is increasing the component count and complexity of the charger.”

“Electrolytic capacitors are physically large, occupy a significant fraction of the internal volume and often constrain form factor options – particularly minimum thickness – of adapter designs” said Lee. “The MinE-CAP IC allows the designer to use predominantly low voltage rated capacitors for a large portion of the energy storage, which shrinks the volume of those components linearly with voltage.”

This compares to reducing the size of high power adaptors using wide bandwidth semiconductors at higher frequencies which requires smaller inductors and magnetics. Instead the MinE-CAP operates at a conventional 110kHz frequency.

“MinE-CAP provides more volume saving than doubling the switching frequency, while actually increasing system efficiency,” said Lee. “The switching frequency determines the size but the line voltage determines the bulk capacitors, so a 230V input needs a 400V capacitor, twice the size of a 160V 100uF capacitor. A lot of adaptors have an input that has to accommodate the high capacitor and high voltage, so MinE CAP will give a different way of thinking about how to use the bulk capacitor.”

Next: GaN design challenges

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