A Short-Flip Switched-Capacitor-Based AC-DC Converter for 120/230VRMS Mains Interfaces

Abstract

Due to the rapid development of smart homes, some low-power consumption appliances need AC mains to supply energy, so the demand for AC-DC converters is increasing. AC-DC converters using transformers are not suitable for low-power devices due to their large size and expensive price. The method of series capacitors is a good way to convert high-voltage AC to low-voltage DC but has the disadvantage of low output power.
In this report, a Short-Flip Switched-Capacitor-Based AC-DC Converter for 120/230 VRMS mains Interfaces is proposed. Its innovative use of two charge-clearing switches clears the remaining charge of the switched capacitor after each closure. In this way, the same small voltage drops when the switched capacitor is needed to be connected, which ensures a long conduction time. In addition, two switches are used for short-flip operation, so that the waveform after the capacitor divider can be quickly lowered to 0 voltage, which can move to the next half-period faster, and applying these two switches can improve the maximum output power by 15%. The proposed AC-DC converter was manufactured in the 180 nm BCD process, with a silicon area of 2 mm2. It was tested and achieved a maximum output power of 1.2W and a peak efficiency of 78%, the power density is 1100mW /cm2, which is better than the state-of-art.