A 1.52-W Capacitor-Drop Sigma-Floating-SC AC/DC Converter for Grid Power to IoT Devices

This work proposes a switched-capacitor (SC)-based non-isolated ac–dc power converter, converting the ac mains (110V @ 60Hz or 230V @ 50Hz) input to a single-cell battery voltage (3.3–4.6V), optimized for the Internet-of-Things (IoT) and smart home devices. We use a sigma-SC rectifier to reduce the freewheeling current loss and to share the output current stress. Also, we introduce a floating-SC dc–dc converter to increase the output power and the equivalent output capacitance. Fabricated in a 180-nm BCD process, it reaches a peak efficiency of 81.3%, showing up to 8% efficiency improvement over a wide load current range compared with prior arts. With these two proposed techniques, the maximum output power of the ac–dc converter is 1.52W with 739-mW/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density, including all the bill of materials (BOM).