This work presents an offline power supply with fully integrated power stage in 0.18 μ m high-voltage (HV) CMOS silicon on insulator (SOI). It supports both ac-dc and dc-dc conversion from 15-400 V input down to 3.3-10 V output and is optimized for applications below 300 mW such as the Internet of Things (IoT), smart home, and e-mobility. An active zero-crossing buffer enables on-chip integration of the HV buffer capacitor. Below 150 V, constant ON-time control is based on voltage intervals, sensed by ten HV threshold-detection circuits. Above 150 V, the converter operates in the resonant mode. It achieves a superior power density of 458 mW/cm3 and 84% peak efficiency.
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