A Time-Domain-Controlled Single-Inductor Step-Up Converter With Symmetric Bipolar Output Voltages

This article presents a time-domain-controlled (TDC) single-inductor triple-output (SITO) step-up converter for portable devices with a bipolar power supply. A time-domain controller is utilized in the proposed converter to achieve a minimized delay time and thus ensure a high-conversion ratio (CR) with a switching frequency of 2 MHz. The proposed power converter employs a time-domain energy distribution (ED) balance scheme to ensure the bipolar outputs are symmetrically regulated. In addition, with the assistance of the output offset correction circuits, the load regulation of the TDC-SITO converter is greatly improved. By using an analog-to-digital converter (ADC)-assisted fast-settling loop, the converter achieves an excellent load transient response with low undershoot/overshoot voltages. Powered by a lithium-ion battery, the TDC-SITO converter can generate a bipolar power supply of +/- 12 V and a standard 5 V output voltage, indicating a maximum CR of 8.8x. Implemented in a 180 nm bipolar-CMOS-DMOS (BCD) process, the converter achieves a peak conversion efficiency of 91.6% at an output power of 2.25 W. With a load current step of 100 mA between two output voltages of +/- 10 V, the output voltages recover their normal values within 100 mu s while the undershoot/overshoot voltages are below 160 mV. The maximum output power of the TDC-SITO converter is 9.6 W.