Reducing the weight of a
portable battery charger
The battery charger for a mobile phone is bigger than the phone itself.
In fact, Alternating Current (AC) adapters can be bulky and heavy items, making them both
difficult and inconvenient to transport. The most significant cause of their size and
weight is the magnetic transformer needed for Direct Current (DC) power conversion.
Piezoelectric technology for power conversion can radically reduce the size of the power
The TRAMST project has been developing advanced piezoelectric transformers. The project
has already developed a transformer type with a power density of around 50mW/mm3.
The target in piezoelectric transformers is around 10mW/mm3. The project has
developed a miniaturised AC battery-charger for mobile phones, which is inserted directly
into the connector plug. The key feature is a novel power transformer based on
piezoelectric materials. The technology has reduced the size of a typical linear power
supply by a factor of five and its weight by a factor of four. The technology is not
limited to AC applications, as piezoelectric transformers are equally suitable for general
use in low-power converters (up to 20W), with important weight advantages over
conventional magnetic transformers.
The miniaturised battery-charger product is on display on the TRAMST stand where
visitors will be able to see and test it.