A Robust DC-DC Converter with Negative Voltage Bootstrapping Using Low-Temperature Poly-Si Oxide TFTs for Fully Flexible Circuits

This paper presents a highly robust -4V DC-DC converter composed of low-temperature poly-Si oxide (LTPO) TFTs. The proposed circuit significantly reduces the off-state overdrive voltage using the negative voltage bootstrapping technique, thus enhancing the circuit robustness in against V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> shifts for flexible applications. A dual-gate feedback is adopted in the loop control system for a reliable and constant output performance. The post-layout simulation results demonstrate that the steady-state voltage deviation remains below 1%, whereas the conventional design suffers from a voltage degradation of 17.1% for a V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> shift of ±3 V. Furthermore, the compact DC-DC converter achieves maximum power efficiency of 93.7% @20 μA, and 84.1% @100 μA.