Using coupled inductors to enhance transient performance of multi-phase buck converters

Motivated by modern microprocessors' demand for high-current, low-voltage power with large transient load steps, a scalable multi-phase coupled inductor buck circuit is presented which delivers 80 A at 1.2 V from a 12 V input. 4-phase coupling and 1 MHz per-phase switching frequency enable the use of 50 nil per-phase leakage inductance so that the system is capable of supporting 15%-to-full-to-15% load transient steps with a 72 mV output voltage window using only a small bank of MLCC output capacitors.