A 5.7GHz RF Wireless Power Transfer Receiver Using 84.5% Efficiency 12V SIDO Buck-Boost DC-DC Converter with Internal Power Supply Mode

Power supply to the sensors in an IoT-era is a major concern because the number of sensors are so enormous that environmental loads and costs will be huge if wires are used. Also, battery exchange is unacceptable in many cases. RF wireless power transfer (WPT) system is a good solution for the remote power sources with a distance longer than a few meters. Figure 1 shows the 5.7GHz RFWPT system and its specification considered in this work. The TX power is controlled by beamforming using 5.7GHz frequency to reduce beam width and antenna size. The TX-RX distance ranges from 1 to 10m, thus RX RF input power P
IN
varies from -3 to nearly up to 30dBm $(500 \mu W \sim 1W)$. The maximum P
IN
is much higher than that of the typical RF energy harvesting systems can handle [1–4]. To supply multiple RX sensor nodes with a single TX module, time-division power supply is used. For such WPT system, input voltage of the DC-DC converter $(V_{IN_DC})$ needs to cover up to 10V, since the open circuit voltage V
OC
of the rectifier exceeds 10V at $P_{IN}=30$ dBm. On the other hand, power consumption of the controller circuit should be small to be efficient at low P
IN
. Furthermore, the DC-DC converter should be kept alive when there is no RF input. This interruption may last a few ms to a few seconds.