48-to-1 V Direct Conversion Using High-Voltage Storage and Low-Voltage Boost Bootstrap Technique and Early Comparison On-Time Generator for Precise Nanosecond Pulses and 90.3% Efficiency in Automotive Applications

This article presents a one-stage buck converter with an accurate nanosecond ON-time (TON) control for 48–1-V direct conversion for automotive applications. In order to overcome the low duty cycle from 48 to 1 V, the proposed high-voltage storage and low-voltage boost (HSLB) bootstrap circuit can reduce the level shifter delay to close to zero and the bootstrap delay to less than 2 ns. In addition, the early comparisonTONgenerator can reduce the comparator delay (T_d_ comp) to close to zero at steady state to achieve precise nanosecond pulseTON. On the other hand,T_d_ compcan be quickly extended to increaseTONby 540% to achieve fast transient with the recovery time of 3μ s, in case load changes from 200 mA to 1 A. Based on the precise nanosecondTON, the OFF-time is extended by the load-dependent current limiting OFF-time modulation for improving light-load efficiency. Experimental results show that the peak efficiency reaches 96.5%, 95.1%, and 92.8% whenVINis 12, 24, and 48 V, respectively, forVOUT = 1V.