A Level Shifter With Almost Full Immunity to Positive dv/dt for Buck Converters

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Abstract

High-frequency buck converters need a fast transition of switching nodes
(high dv/dt). Such high dv/dt, especially the positive one, can cause
malfunction of a conventional pulse-triggered active-coupled (PTAC)
level shifter that is used to control the high-side NMOS switch. In this
work, we first discuss the dv/dt immunity of conventional PTAC level
shifters. Subsequently, we propose a new scheme to block the noise
current during the dv/dt sequence, allowing an almost full immunity to
the positive dv/dt. With this scheme, the maximum dv/dt is determined by
how well the circuitry is protected from the overvoltage during the
dv/dt sequence. We design a 20-V buck converter with this level shifter,
fabricated in 180-nm BCD process. Experimental results show it works
correctly under a 67-V/ns dv/dt.