Positive‐negative DC‐DC converter using amorphous‐InGaZnO TFTs

Abstract

SummaryThis paper presents two DC‐DC converters capable of generating either positive or negative output DC voltage using amorphous‐indium gallium zinc oxide (a‐IGZO) thin‐film transistors (TFTs). While one uses conventional diode‐connected cross‐coupled (design‐1), the other employs a bootstrapped cross‐coupled (design‐2) DC‐DC converter, which overcomes the limitations of design‐1 but requires boosted clock pulses. Therefore, an on‐chip clock booster is proposed to generate all the required signals without any external clock pulses. The performance of the proposed circuits (DC‐DC converters and clock booster) has been demonstrated using in‐house a‐IGZO TFT models in the Cadence environment. The simulation results have shown that design‐1 (design‐2) generates negative or positive output DC voltage of 7.25 V (7.8 V) or 12.7 V (15.2 V), respectively, for a supply voltage of 8 V, using a single DC‐DC converter. Therefore, the output DC voltage of design‐2 is close to the theoretical value, and it ensures robust performance against different load currents when compared with design‐1. Besides, design‐2 has shown a maximum power efficiency of 90%, superior compared with design‐1, where power efficiency is 60.7%. Therefore, this circuit finds potential applications in the next generation flexible displays.