A digitally controlled DC-DC buck converter with lossless load-current sensing and BIST functionality

Lossless load current sensing ability is one of the most desirable features of contemporary current-or voltage-mode-controlled DC-DC converters. Current sensing can be used for short circuit detection, multi-stage converter load balancing, thermal control, and load-independent control of DC-DC converters (Woo et al., 2008). Recently, current sensing techniques using the existing inductor series DC resistance (DCR) are gaining attention due to their reduced complexity and minimized loss. These techniques increase the need for inductor build-in self test (BIST) ability to measure DCR. Inductor BIST is also critical for high-reliability applications such as automotive and aerospace systems where component variation and drift need to be closely monitored. An analog inductor characterization and current sensing technique utilizing Gm-C filtering is proposed in [2], where the gain errors and sensing offset are cancelled in analog domain. The DC-DC buck converter presented here uses an offset-independent inductor characterization enabling a digital continuous lossless load-current-sensing scheme. The proposed inductor BIST and current-sensing techniques can be extended to current-mode-controlled converters and multi-stage parallel converters as well.