A Hybrid Boost Converter With Cross-Connected Flying Capacitors
Mo Huang, Yan Lü, Tingxu Hu, Rui P. Martins
Abstract
This article presents a monolithic hybrid boost converter suitable for a high conversion ratio (CR). It uses two inductors, two cross-connected flying capacitors ( C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> s), and six power switches, allowing a two-phase operation and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> s near-soft charging. With the internal voltages halved by the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> s, the inductor current ripple and voltage stress of the switches decrease, thus allowing a reduction in both power loss and silicon area. In addition, the cross-connected C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> s double the pulsewidth of the control signals, thereby allowing a higher switching frequency even under a very high CR. Moreover, this design shares the large bootstrap capacitors of the high-side NMOS switches and also eliminates the need for an additional bootstrap voltage generation for the stacked NMOS switches, enabling an area-efficient full integration of the bootstrap capacitors. The converter, fabricated in 0.35- μm CMOS, occupies a core area of 0.86 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . It achieves a 93.5% peak efficiency when the CR is 4.5, with two 3.3- μH inductors (3010 package), two 0.47- μF C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> s, and a 2-MHz switching frequency.