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Smart homes and smart buildings require numerous offline devices such as IoT nodes, object sensors, smoke detectors, etc. Those devices usually get power from the AC main voltage and require converters to directly convert a universal 85-to-264Vac down to 3-to-4.2Vdc battery voltages. Non-isolated AC-DC converters feature compact size, low cost, and easy deployment, and are in huge demand in recent years. Traditional non-isolated AC-DC converters use high-voltage (HV) linear or inductive switching regulators and have low efficiency or bulky system volume drawbacks. Compared with inductive counterparts, the capacitor-drop AC-DC power converter [1] –[4] uses an X-capacitor as a buffer to stand most of the high voltage and reduce the voltage level that is faced by the rectifier. It shows potential benefits of higher integration level [3], [4], more compact size, and higher overall efficiency [3], but still faces challenges of …