Synchronous coarse-fine comparators based zero-current detector for DC-DC converter operating in switching frequency beyond 10 MHz

This paper presents a zero-current detector (ZCD) applied in high-frequency synchronous buck DC-DC converters to enable DCM/PFM operation mode. The proposed ZCD is designed based on power efficient synchronous comparators operating in different frequency, of which coarse comparator predetermines operating period of fine comparator while inductor current zero-crossing is accurately detected by fine comparator. Implemented in 0.18 μm HVCMOS process and operating in a buck converter at a switching frequency of 10 MHz, the proposed ZCD can achieve a sensing delay around 1 ns.