An Accurate Zero-Current-Switching Circuit for Ultra-Low-Voltage Boost Converters

The use of digital schemes to indirectly detect the zero-current crossing and perform the zero-current switching in ultra-low-voltage inductive boost converters has been prevalent in recent developments. However, design guidelines for such digital schemes are still lacking. In this brief, an efficient zero-current switching scheme for ultra-low-voltage boost converters is proposed and implemented in standard CMOS 130 nm technology. Instrumental to our design was the introduction of the proper time delay for sensing the direction of the inductor current on the opening of the high-side switch. The correct delay time as a function of the circuit parameters keeps the switching as close as possible to the zero-current crossing. Owing to an efficient zero-current-switching scheme, the fabricated prototype provides end-to-end efficiency of 76% for a voltage converter having an input voltage as low as 20 mV.