Fully integrated high‐efficiency high step‐down ratio DC–DC buck converter with predictive over‐current protection scheme

Abstract

A high-efficiency fully integrated 36 V–3 A stepping down DC–DC converter with high step-down ratio and predictive over-current protection scheme is introduced. To achieve high-voltage conversion ratio, emulated current mode and dedicated current sensing circuits were involved. A novel predictive over-current scheme is proposed to overcome inherent lack of emulated current-mode control and provide fast response to over-current events. In addition, due to N-type field effect transistor (NFET) was adopted to improve efficiency, a floating rail regulator is presented to generate bootstrapped voltage for driver stage. The proposed converter was simulated and fabricated in 0.18 μm bipolar-complementary metal–oxide–semiconductor (MOS)-double-diffused MOS process. Experimental results show the features work well, and with 35 ns minimum on-time, this converter can convert up to 36 V input voltage to 1.8 V at 1 MHz switching frequency with single stage and compact solution. Measured peak efficiency is 89.5% and over 80% efficiency for 3 A output current is realised as well.