A Bipolar-Output Switched-Capacitor DC-DC Boost Converter With Residual-Energy-Recycling Regulation and Low Dropout Post-Filtering Techniques

Abstract

This article presents an energy-efficient, low-noise, and bipolar-output step-up switched-capacitor converter (SCC) with ultralow dropout post-regulation, which aims to power a noise-sensitive thin-film transistor (TFT) circuitry in mobile applications. The residual-energy-recycled (RER) step-up SCC is proposed to realize fine-grained voltage conversion ratios (VCRs) without degrading the power efficiency. It also enables the current density to be highly relaxed, thereby integrating many capacitors of the SCC into the chip. To achieve high power-supply rejection (PSR) under an extremely low dropout voltage (V-DO) granularly regulated by the RER step-up SCC, a voltage/current-hybrid (VIH) post-regulator is also presented in this work. The proposed bipolar-output (+/- 15 V) boost converter able to supply up to 600 mW is implemented in a 0.18-mu m BCD process. The fabricated RER step-up SCC, capable of reconfiguring the VCR from 3 x to 5 x with a step size of x1/32, achieves a peak efficiency of 91.7%. The VIH post-regulator shows a PSR of -75 dB at 30 kHz while consuming a very low V-DO (1% of the final output). The total system efficiency is measured to be 90.5%, and the output noise integrated from 10 Hz to 0.5 MHz is 28.7 VRMS, including the SCC ripple.