Microfabricated coupled inductors for integrated power converters

A microfabricated coupled inductor for low-voltage, high-current power converters is presented. The aim is to miniaturize such converters and improve their transient response using high-performance microfabricated inductors. These inductors have high power density enabled by a high-flux-density magnetic material (NiFe) and have the potential for integration with silicon circuits. A four-phase magnetically coupled structure with 14 nH of inductance per phase has been fabricated on silicon and implemented in a 5 MHz, 5-1 V, 4 A DC-DC converter. The coupled structure consists of four adjacent U-shaped copper windings sandwiched between two layers of NiFe. Electrical measurements match well with predictions for the converter.