An improved integrated lossless self-matched current-sensing circuit based on Gm-C filter for 4-switch buck-boost topology

An integrated lossless inductor current-sensing method is proposed. Its core is the using of a Gm-C filter, whose frequency response matches the inductor time-constant. In order to fit different types and values of inductors, tuning and calibration process is introduced in for self-matching ahead of normal loop control. For applying the proposed method to a 4-switch buck-boost converter, some special issues like high ICMR, transconductance programmability, and high output resistant were carefully considered and treated. Based on it, the propose circuit is designed and fabricated with TSMC 0.35-µm CMOS technology successfully. The experimental results are consistent with expectations well.