High-frequency isolated ac-dc converter with stacked architecture

This paper presents a new isolated ac-dc power converter achieving both high power factor and converter miniaturization suitable for many low power ac-dc applications. The proposed ac-dc converter architecture comprises a line-frequency rectifier, a stack of capacitors, a set of regulating converters, and a multi-input isolated bus converter. Among many suitable circuit implementations, the prototype system utilizes the resonant-transition buck converter as a regulating converter, and the capacitively-aided isolated bus converter for the isolated bus converter. The converter is miniaturized by operating at high frequency (1–10 MHz range), and it buffers the ac-line frequency energy with a pair of stacked ceramic capacitors (1 μE and 150 μE, 100 V rating) without a requirement for electrolytic capacitors. The prototype converter is implemented to operate from 120 Vac to 12 V, and up to 50 W output as an example isolated ac-dc converter for power supply applications. The prototype converter demonstrates with 88 % efficiency and 0.86 power factor, and provides 50 W/in 3 power density, which is five times higher than the power density of typical conventional designs.