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
Siyi Li, Bo-Ruen Chen, Ke‐Horng Chen, Ying-Hsi Lin, Shian-Ru Lin, Tsung-Yen Tsai
Abstract
This article presents a one-stage buck converter with an accurate nanosecond ON-time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> ) 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 comparison <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> generator can reduce the comparator delay ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{d\_{}{\mathrm{ comp}}}$ </tex-math></inline-formula> ) to close to zero at steady state to achieve precise nanosecond pulse <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> . On the other hand, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{d\_{}{\mathrm{ comp}}}$ </tex-math></inline-formula> can be quickly extended to increase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> by 540% to achieve fast transient with the recovery time of 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> , in case load changes from 200 mA to 1 A. Based on the precise nanosecond <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> , 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% when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {IN}}$ </tex-math></inline-formula> is 12, 24, and 48 V, respectively, for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {OUT}} = 1$ </tex-math></inline-formula> V.