Fully Integrating a 400 V-to-12 V DC–DC Converter in High-Voltage CMOS

This article presents the first fully integrated $\mathrm {400\quad V}$ switching DC–DC converter. The converter topology exploits maximized dielectric energy storage at high voltage (HV) and significantly reduces the sidewall coupling of flying capacitors. The custom design of the HV capacitors and drivers further optimizes the performance. In addition, a control circuit improves the ripple and the load-step response, as proven by measurements. The converter is implemented in a $\mathrm {180\quad nm}$ CMOS silicon on insulator (SOI) technology. While realizing a 33: 1 conversion step, the measured power density is $\mathrm {119\quad mW/mm^{2}}$ at $\mathrm {63.6\quad \%}$ efficiency. This advances the power density of fully integrated state-of-the-art converters by $270\times $ and the maximum input voltage by $9\times $ while achieving the highest efficiency.