A Highly Power-Efficient Single-Inductor Bipolar-Output DC–DC Converter Using Hysteretic Skipping Control for OLED-on-Silicon Microdisplays

In this brief, a highly power-efficient single-inductor bipolar-output (SIBO) DC–DC converter is proposed for use as the pixel power supply of organic light-emitting diode-on-silicon microdisplays, which are used in virtual reality and augmented reality applications. The proposed SIBO DC–DC converter regulates its negative output voltage ( ${V_{\mathrm{ ON}}}$ ) using hysteretic skipping to reduce the number of switching operations, resulting in an increase in power efficiency. In addition, it regulates the positive output voltage ( ${V_{\mathrm{ OP}}}$ ) with higher priority than ${V_{\mathrm{ ON}}}$ , thus having little influence on pixel luminance variations. The proposed SIBO DC–DC converter was designed for a maximum load current of 30 mA, a ${V_{\mathrm{ OP}}}$ of 4.80 V, and a ${V_{\mathrm{ ON}}}$ of −2.50 V. It was fabricated using 90-nm standard CMOS process technology with high voltage devices of 8 V. The measurement results show that the ripples of ${V_{\mathrm{ OP}}}$ and ${V_{\mathrm{ ON}}}$ are 17 mV and 50 mV, respectively, at a load current of 20 mA. The measured load regulations of ${V_{\mathrm{ OP}}}$ and ${V_{\mathrm{ ON}}}$ are 0.03 mV/mA and 0.06 mV/mA, respectively. The measured line regulations of ${V_{\mathrm{ OP}}}$ and ${V_{\mathrm{ ON}}}$ are 1.25 mV/V and 2.50 mV/V, respectively. In addition, the measured maximum power efficiency is 90.1%.